X Toolkit Intrinsics -- C Language Interface X Window System X Version 11, Release 6.4 First Revision - April, 1994 Joel McCormack Digital Equipment Corporation Western Software Laboratory Paul Asente Digital Equipment Corporation Western Software Laboratory Ralph R. Swick Digital Equipment Corporation External Research Group MIT X Consortium version 6 edited by Donna Converse X Consortium, Inc. X Window System is a trademark of X Consortium, Inc. Copyright (C) 1985, 1986, 1987, 1988, 1991, 1994 X Consor- tium Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documenta- tion files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PUR- POSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSOR- TIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. Except as contained in this notice, the name of the X Con- sortium shall not be used in advertising or otherwise to promote the sale, use or other dealings in this Software without prior written authorization from the X Consortium. Copyright (C) 1985, 1986, 1987, 1988, 1991, 1994 Digital Equipment Corporation, Maynard, Massachusetts. Permission to use, copy, modify and distribute this documen- tation for any purpose and without fee is hereby granted, provided that the above copyright notice appears in all copies and that both that copyright notice and this permis- sion notice appear in supporting documentation, and that the name of Digital not be used in in advertising or publicity pertaining to distribution of the software without specific, written prior permission. Digital makes no representations about the suitability of the software described herein for any purpose. It is provided ``as is'' without express or implied warranty. Acknowledgments The design of the X11 Intrinsics was done primarily by Joel McCormack of Digital WSL. Major contributions to the design and implementation also were done by Charles Haynes, Mike Chow, and Paul Asente of Digital WSL. Additional contribu- tors to the design and/or implementation were: Loretta Guarino-Reid (Digital WSL)Rich Hyde (Digital WSL) Susan Angebranndt (Digital WSL)Terry Weissman (Digital WSL) Mary Larson (Digital UEG) Mark Manasse (Digital SRC) Jim Gettys (Digital SRC) Leo Treggiari (Digital SDT) Ralph Swick (Project Athena and Digital ERP)Mark Ackerman (Project Athena) Ron Newman (Project Athena) Bob Scheifler (MIT LCS) The contributors to the X10 toolkit also deserve mention. Although the X11 Intrinsics present an entirely different programming style, they borrow heavily from the implicit and explicit concepts in the X10 toolkit. The design and implementation of the X10 Intrinsics were done by: Terry Weissman (Digital WSL) Smokey Wallace (Digital WSL) Phil Karlton (Digital WSL) Charles Haynes (Digital WSL) Frank Hall (HP) The design and implementation of the X10 toolkit's sample widgets were by the above, as well as by: Ram Rao (Digital UEG) Mary Larson (Digital UEG) Mike Gancarz (Digital UEG) Kathleen Langone (Digital UEG) These widgets provided a checklist of requirements that we had to address in the X11 Intrinsics. Thanks go to Al Mento of Digital's UEG Documentation Group for formatting and generally improving this document and to John Ousterhout of Berkeley for extensively reviewing early drafts of it. xi Finally, a special thanks to Mike Chow, whose extensive per- formance analysis of the X10 toolkit provided the justifica- tion to redesign it entirely for X11. Joel McCormack Western Software Laboratory Digital Equipment Corporation March 1988 xii The current design of the Intrinsics has benefited greatly from the input of several dedicated reviewers in the member- ship of the X Consortium. In addition to those already men- tioned, the following individuals have dedicated significant time to suggesting improvements to the Intrinsics: Steve Pitschke (Stellar) C. Doug Blewett (AT&T) Bob Miller (HP) David Schiferl (Tektronix) Fred Taft (HP) Michael Squires (Sequent) Marcel Meth (AT&T) Jim Fulton (MIT) Mike Collins (Digital) Kerry Kimbrough (Texas Instruments) Scott McGregor (Digital) Phil Karlton (Digital) Julian Payne (ESS) Jacques Davy (Bull) Gabriel Beged-Dov (HP) Glenn Widener (Tektronix) Thanks go to each of them for the countless hours spent reviewing drafts and code. Ralph R. Swick External Research Group Digital Equipment Corporation MIT Project Athena June 1988 From Release 3 to Release 4, several new members joined the design team. We greatly appreciate the thoughtful comments, suggestions, lengthy discussions, and in some cases imple- mentation code contributed by each of the following: Don Alecci (AT&T) Ellis Cohen (OSF) Donna Converse (MIT) Clive Feather (IXI) Nayeem Islam (Sun) Dana Laursen (HP) Keith Packard (MIT) Chris Peterson (MIT) Richard Probst (Sun) Larry Cable (Sun) In Release 5, the effort to define the internationalization additions was headed by Bill McMahon of Hewlett Packard and Frank Rojas of IBM. This has been an educational process for many of us, and Bill and Frank's tutelage has carried us through. Vania Joloboff of the OSF also contributed to the internationalization additions. The implementation efforts of Bill, Gabe Beged-Dov, and especially Donna Converse for this release are also gratefully acknowledged. xiii Ralph R. Swick December 1989 and July 1991 xiv The Release 6 Intrinsics is a result of the collaborative efforts of participants in the X Consortium's intrinsics working group. A few individuals contributed substantial design proposals, participated in lengthy discussions, reviewed final specifications, and in most cases, were also responsible for sections of the implementation. They deserve recognition and thanks for their major contribu- tions: Paul Asente (Adobe) Larry Cable (SunSoft) Ellis Cohen (OSF) Daniel Dardailler (OSF) Vania Joloboff (OSF) Kaleb Keithley (X Consortium) Courtney Loomis (HP) Douglas Rand (OSF) Bob Scheifler (X Consortium) Ajay Vohra (SunSoft) Many others analyzed designs, offered useful comments and suggestions, and participated in a significant subset of the process. The following people deserve thanks for their con- tributions: Andy Bovingdon, Sam Chang, Chris Craig, George Erwin-Grotsky, Keith Edwards, Clive Feather, Stephen Gildea, Dan Heller, Steve Humphrey, David Kaelbling, Jaime Lau, Rob Lembree, Stuart Marks, Beth Mynatt, Tom Paquin, Chris Peter- son, Kamesh Ramakrishna, Tom Rodriguez, Jim VanGilder, Will Walker, and Mike Wexler. I am especially grateful to two of my colleagues: Ralph Swick for expert editorial guidance, and Kaleb Keithley for leadership in the implementation and the specification work. Donna Converse X Consortium April 1994 xv About This Manual X Toolkit Intrinsics -- C Language Interface is intended to be read by both application programmers who will use one or more of the many widget sets built with the Intrinsics and by widget programmers who will use the Intrinsics to build widgets for one of the widget sets. Not all the information in this manual, however, applies to both audiences. That is, because the application programmer is likely to use only a number of the Intrinsics functions in writing an applica- tion and because the widget programmer is likely to use many more, if not all, of the Intrinsics functions in building a widget, an attempt has been made to highlight those areas of information that are deemed to be of special interest for the application programmer. (It is assumed the widget pro- grammer will have to be familiar with all the information.) Therefore, all entries in the table of contents that are printed in bold indicate the information that should be of special interest to an application programmer. It is also assumed that, as application programmers become more familiar with the concepts discussed in this manual, they will find it more convenient to implement portions of their applications as special-purpose or custom widgets. It is possible, nonetheless, to use widgets without knowing how to build them. Conventions Used in this Manual This document uses the following conventions: o Global symbols are printed in this special font. These can be either function names, symbols defined in include files, data types, or structure names. Argu- ments to functions, procedures, or macros are printed in italics. o Each function is introduced by a general discussion that distinguishes it from other functions. The func- tion declaration itself follows, and each argument is specifically explained. General discussion of the function, if any is required, follows the arguments. o To eliminate any ambiguity between those arguments that you pass and those that a function returns to you, the explanations for all arguments that you pass start with the word specifies or, in the case of multiple argu- ments, the word specify. The explanations for all arguments that are returned to you start with the word returns or, in the case of multiple arguments, the word xvi return. xvii Chapter 1 Intrinsics and Widgets The Intrinsics are a programming library tailored to the special requirements of user interface construction within a network window system, specifically the X Window System. The Intrinsics and a widget set make up an X Toolkit. 1.1. Intrinsics The Intrinsics provide the base mechanism necessary to build a wide variety of interoperating widget sets and application environments. The Intrinsics are a layer on top of Xlib, the C Library X Interface. They extend the fundamental abstractions provided by the X Window System while still remaining independent of any particular user interface pol- icy or style. The Intrinsics use object-oriented programming techniques to supply a consistent architecture for constructing and com- posing user interface components, known as widgets. This allows programmers to extend a widget set in new ways, either by deriving new widgets from existing ones (subclass- ing) or by writing entirely new widgets following the estab- lished conventions. When the Intrinsics were first conceived, the root of the object hierarchy was a widget class named Core. In Release 4 of the Intrinsics, three nonwidget superclasses were added above Core. These superclasses are described in Chapter 12. The name of the class now at the root of the Intrinsics class hierarchy is Object. The remainder of this specifica- tion refers uniformly to widgets and Core as if they were the base class for all Intrinsics operations. The argument descriptions for each Intrinsics procedure and Chapter 12 describe which operations are defined for the nonwidget superclasses of Core. The reader may determine by context whether a specific reference to widget actually means ``wid- get'' or ``object.'' 1.2. Languages The Intrinsics are intended to be used for two programming purposes. Programmers writing widgets will be using most of the facilities provided by the Intrinsics to construct user interface components from the simple, such as buttons and scrollbars, to the complex, such as control panels and 1 X Toolkit Intrinsics X11 Release 6.4 property sheets. Application programmers will use a much smaller subset of the Intrinsics procedures in combination with one or more sets of widgets to construct and present complete user interfaces on an X display. The Intrinsics programming interfaces primarily intended for application use are designed to be callable from most procedural pro- gramming languages. Therefore, most arguments are passed by reference rather than by value. The interfaces primarily intended for widget programmers are expected to be used principally from the C language. In these cases, the usual C programming conventions apply. In this specification, the term client refers to any module, widget, or application that calls an Intrinsics procedure. Applications that use the Intrinsics mechanisms must include the header files and , or their equivalent, and they may also include and . In addition, widget implementations should include instead of . The applications must also include the additional header files for each widget class that they are to use (for exam- ple, or ). On a POSIX-based system, the Intrinsics object library file is named libXt.a and is usually referenced as -lXt when linking the application. 1.3. Procedures and Macros All functions defined in this specification except those specified below may be implemented as C macros with argu- ments. C applications may use ``#undef'' to remove a macro definition and ensure that the actual function is refer- enced. Any such macro will expand to a single expression that has the same precedence as a function call and that evaluates each of its arguments exactly once, fully pro- tected by parentheses, so that arbitrary expressions may be used as arguments. The following symbols are macros that do not have function equivalents and that may expand their arguments in a manner other than that described above: XtCheckSubclass, XtNew, XtNumber, XtOffsetOf, XtOffset, and XtSetArg. 1.4. Widgets The fundamental abstraction and data type of the X Toolkit is the widget, which is a combination of an X window and its associated input and display semantics and which is dynami- cally allocated and contains state information. Some 2 X Toolkit Intrinsics X11 Release 6.4 widgets display information (for example, text or graphics), and others are merely containers for other widgets (for example, a menu box). Some widgets are output-only and do not react to pointer or keyboard input, and others change their display in response to input and can invoke functions that an application has attached to them. Every widget belongs to exactly one widget class, which is statically allocated and initialized and which contains the operations allowable on widgets of that class. Logically, a widget class is the procedures and data associated with all widgets belonging to that class. These procedures and data can be inherited by subclasses. Physically, a widget class is a pointer to a structure. The contents of this structure are constant for all widgets of the widget class but will vary from class to class. (Here, ``constant'' means the class structure is initialized at compile time and never changed, except for a one-time class initialization and in- place compilation of resource lists, which takes place when the first widget of the class or subclass is created.) For further information, see Section 2.5. The distribution of the declarations and code for a new wid- get class among a public .h file for application programmer use, a private .h file for widget programmer use, and the implementation .c file is described in Section 1.6. The predefined widget classes adhere to these conventions. A widget instance is composed of two parts: o A data structure which contains instance-specific val- ues. o A class structure which contains information that is applicable to all widgets of that class. Much of the input/output of a widget (for example, fonts, colors, sizes, or border widths) is customizable by users. This chapter discusses the base widget classes, Core, Com- posite, and Constraint, and ends with a discussion of widget classing. 1.4.1. Core Widgets The Core widget class contains the definitions of fields common to all widgets. All widgets classes are subclasses of the Core class, which is defined by the CoreClassPart and CorePart structures. 3 X Toolkit Intrinsics X11 Release 6.4 1.4.1.1. CoreClassPart Structure All widget classes contain the fields defined in the Core- ClassPart structure. __ | typedef struct { WidgetClass superclass; See Section 1.6 String class_name; See Chapter 9 Cardinal widget_size; See Section 1.6 XtProc class_initialize; See Section 1.6 XtWidgetClassProc class_part_initialize;See Section 1.6 XtEnum class_inited; See Section 1.6 XtInitProc initialize; See Section 2.5 XtArgsProc initialize_hook; See Section 2.5 XtRealizeProc realize; See Section 2.6 XtActionList actions; See Chapter 10 Cardinal num_actions; See Chapter 10 XtResourceList resources; See Chapter 9 Cardinal num_resources; See Chapter 9 XrmClass xrm_class; Private to resource manager Boolean compress_motion; See Section 7.9 XtEnum compress_exposure; See Section 7.9 Boolean compress_enterleave; See Section 7.9 Boolean visible_interest; See Section 7.10 XtWidgetProc destroy; See Section 2.8 XtWidgetProc resize; See Chapter 6 XtExposeProc expose; See Section 7.10 XtSetValuesFunc set_values; See Section 9.7 XtArgsFunc set_values_hook; See Section 9.7 XtAlmostProc set_values_almost;See Section 9.7 XtArgsProc get_values_hook; See Section 9.7 XtAcceptFocusProc accept_focus;See Section 7.3 XtVersionType version; See Section 1.6 XtPointer callback_private; Private to callbacks String tm_table; See Chapter 10 XtGeometryHandler query_geometry;See Chapter 6 XtStringProc display_accelerator;See Chapter 10 XtPointer extension; See Section 1.6 } CoreClassPart; |__ All widget classes have the Core class fields as their first component. The prototypical WidgetClass and CoreWidgetClass are defined with only this set of fields. 4 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { CoreClassPart core_class; } WidgetClassRec, *WidgetClass, CoreClassRec, *CoreWidgetClass; |__ Various routines can cast widget class pointers, as needed, to specific widget class types. The single occurrences of the class record and pointer for creating instances of Core are In IntrinsicP.h: __ | extern WidgetClassRec widgetClassRec; #define coreClassRec widgetClassRec |__ In Intrinsic.h: __ | extern WidgetClass widgetClass, coreWidgetClass; |__ The opaque types Widget and WidgetClass and the opaque vari- able widgetClass are defined for generic actions on widgets. In order to make these types opaque and ensure that the com- piler does not allow applications to access private data, the Intrinsics use incomplete structure definitions in Intrinsic.h: __ | typedef struct _WidgetClassRec *WidgetClass, *CoreWidgetClass; |__ 1.4.1.2. CorePart Structure All widget instances contain the fields defined in the CorePart structure. 5 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _CorePart { Widget self; Described below WidgetClass widget_class;See Section 1.6 Widget parent; See Section 2.5 Boolean being_destroyed; See Section 2.8 XtCallbackList destroy_callbacks;See Section 2.8 XtPointer constraints; See Section 3.6 Position x; See Chapter 6 Position y; See Chapter 6 Dimension width; See Chapter 6 Dimension height; See Chapter 6 Dimension border_width; See Chapter 6 Boolean managed; See Chapter 3 Boolean sensitive; See Section 7.7 Boolean ancestor_sensitive;See Section 7.7 XtTranslations accelerators;See Chapter 10 Pixel border_pixel; See Section 2.6 Pixmap border_pixmap; See Section 2.6 WidgetList popup_list; See Chapter 5 Cardinal num_popups; See Chapter 5 String name; See Chapter 9 Screen *screen; See Section 2.6 Colormap colormap; See Section 2.6 Window window; See Section 2.6 Cardinal depth; See Section 2.6 Pixel background_pixel; See Section 2.6 Pixmap background_pixmap;See Section 2.6 Boolean visible; See Section 7.10 Boolean mapped_when_managed;See Chapter 3 } CorePart; |__ All widget instances have the Core fields as their first component. The prototypical type Widget is defined with only this set of fields. __ | typedef struct { CorePart core; } WidgetRec, *Widget, CoreRec, *CoreWidget; |__ Various routines can cast widget pointers, as needed, to specific widget types. In order to make these types opaque and ensure that the com- piler does not allow applications to access private data, the Intrinsics use incomplete structure definitions in Intrinsic.h. 6 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _WidgetRec *Widget, *CoreWidget; |__ 1.4.1.3. Core Resources The resource names, classes, and representation types speci- fied in the coreClassRec resource list are ------------------------------------------------------------------------ Name Class Representation ------------------------------------------------------------------------ XtNaccelerators XtCAccelerators XtRAcceleratorTable XtNbackground XtCBackground XtRPixel XtNbackgroundPixmap XtCPixmap XtRPixmap XtNborderColor XtCBorderColor XtRPixel XtNborderPixmap XtCPixmap XtRPixmap XtNcolormap XtCColormap XtRColormap XtNdepth XtCDepth XtRInt XtNmappedWhenManaged XtCMappedWhenManaged XtRBoolean XtNscreen XtCScreen XtRScreen XtNtranslations XtCTranslations XtRTranslationTable ------------------------------------------------------------------------ Additional resources are defined for all widgets via the objectClassRec and rectObjClassRec resource lists; see Sec- tions 12.2 and 12.3 for details. 1.4.1.4. CorePart Default Values The default values for the Core fields, which are filled in by the Intrinsics, from the resource lists, and by the ini- tialize procedures, are ------------------------------------------------------------------------------ Field Default Value ------------------------------------------------------------------------------ self Address of the widget structure (may not be changed). widget_class widget_class argument to XtCreateWidget (may not be changed). parent parent argument to XtCreateWidget (may not be changed). being_destroyed Parent's being_destroyed value. destroy_callbacks NULL constraints NULL x 0 y 0 7 X Toolkit Intrinsics X11 Release 6.4 width 0 height 0 border_width 1 managed False sensitive True ancestor_sensitive logical AND of parent's sensitive and ancestor_sensitive values. accelerators NULL border_pixel XtDefaultForeground border_pixmap XtUnspecifiedPixmap popup_list NULL num_popups 0 name name argument to XtCreateWidget (may not be changed). screen Parent's screen; top-level widget gets screen from dis- play specifier (may not be changed). colormap Parent's colormap value. window NULL depth Parent's depth; top-level widget gets root window depth. background_pixel XtDefaultBackground background_pixmap XtUnspecifiedPixmap visible True mapped_when_man- True aged ------------------------------------------------------------------------------ XtUnspecifiedPixmap is a symbolic constant guaranteed to be unequal to any valid Pixmap id, None, and ParentRelative. 1.4.2. Composite Widgets The Composite widget class is a subclass of the Core widget class (see Chapter 3). Composite widgets are intended to be containers for other widgets. The additional data used by composite widgets are defined by the CompositeClassPart and CompositePart structures. 1.4.2.1. CompositeClassPart Structure In addition to the Core class fields, widgets of the Compos- ite class have the following class fields. 8 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { XtGeometryHandler geometry_manager;See Chapter 6 XtWidgetProc change_managed; See Chapter 3 XtWidgetProc insert_child; See Chapter 3 XtWidgetProc delete_child; See Chapter 3 XtPointer extension; See Section 1.6 } CompositeClassPart; |__ The extension record defined for CompositeClassPart with record_type equal to NULLQUARK is CompositeClassExtension- Rec. __ | typedef struct { XtPointer next_extension; See Section 1.6.12 XrmQuark record_type; See Section 1.6.12 long version; See Section 1.6.12 Cardinal record_size; See Section 1.6.12 Boolean accepts_objects; See Section 2.5.2 Boolean allows_change_managed_set;See Section 3.4.3 } CompositeClassExtensionRec, *CompositeClassExtension; |__ Composite classes have the Composite class fields immedi- ately following the Core class fields. __ | typedef struct { CoreClassPart core_class; CompositeClassPart composite_class; } CompositeClassRec, *CompositeWidgetClass; |__ The single occurrences of the class record and pointer for creating instances of Composite are In IntrinsicP.h: __ | extern CompositeClassRec compositeClassRec; |__ In Intrinsic.h: 9 X Toolkit Intrinsics X11 Release 6.4 __ | extern WidgetClass compositeWidgetClass; |__ The opaque types CompositeWidget and CompositeWidgetClass and the opaque variable compositeWidgetClass are defined for generic operations on widgets whose class is Composite or a subclass of Composite. The symbolic constant for the Com- positeClassExtension version identifier is XtCompositeExten- sionVersion (see Section 1.6.12). Intrinsic.h uses an incomplete structure definition to ensure that the compiler catches attempts to access private data. __ | typedef struct _CompositeClassRec *CompositeWidgetClass; |__ 1.4.2.2. CompositePart Structure In addition to the Core instance fields, widgets of the Com- posite class have the following instance fields defined in the CompositePart structure. __ | typedef struct { WidgetList children; See Chapter 3 Cardinal num_children; See Chapter 3 Cardinal num_slots; See Chapter 3 XtOrderProc insert_position;See Section 3.2 } CompositePart; |__ Composite widgets have the Composite instance fields immedi- ately following the Core instance fields. __ | typedef struct { CorePart core; CompositePart composite; } CompositeRec, *CompositeWidget; |__ Intrinsic.h uses an incomplete structure definition to ensure that the compiler catches attempts to access private data. 10 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _CompositeRec *CompositeWidget; |__ 1.4.2.3. Composite Resources The resource names, classes, and representation types that are specified in the compositeClassRec resource list are ------------------------------------------------------------- Name Class Representation ------------------------------------------------------------- XtNchildren XtCReadOnly XtRWidgetList XtNinsertPosition XtCInsertPosition XtRFunction XtNnumChildren XtCReadOnly XtRCardinal ------------------------------------------------------------- 1.4.2.4. CompositePart Default Values The default values for the Composite fields, which are filled in from the Composite resource list and by the Com- posite initialize procedure, are ----------------------------------------------------- Field Default Value ----------------------------------------------------- children NULL num_children 0 num_slots 0 insert_position Internal function to insert at end ----------------------------------------------------- The children, num_children, and insert_position fields are declared as resources; XtNinsertPosition is a settable resource, XtNchildren and XtNnumChildren may be read by any client but should only be modified by the composite widget class procedures. 1.4.3. Constraint Widgets The Constraint widget class is a subclass of the Composite widget class (see Section 3.6). Constraint widgets maintain additional state data for each child; for example, client- defined constraints on the child's geometry. The additional data used by constraint widgets are defined by the Con- straintClassPart and ConstraintPart structures. 11 X Toolkit Intrinsics X11 Release 6.4 1.4.3.1. ConstraintClassPart Structure In addition to the Core and Composite class fields, widgets of the Constraint class have the following class fields. __ | typedef struct { XtResourceList resources;See Chapter 9 Cardinal num_resources; See Chapter 9 Cardinal constraint_size;See Section 3.6 XtInitProc initialize; See Section 3.6 XtWidgetProc destroy; See Section 3.6 XtSetValuesFunc set_values;See Section 9.7.2 XtPointer extension; See Section 1.6 } ConstraintClassPart; |__ The extension record defined for ConstraintClassPart with record_type equal to NULLQUARK is ConstraintClassExtension- Rec. __ | typedef struct { XtPointer next_extension;See Section 1.6.12 XrmQuark record_type; See Section 1.6.12 long version; See Section 1.6.12 Cardinal record_size; See Section 1.6.12 XtArgsProc get_values_hook;See Section 9.7.1 } ConstraintClassExtensionRec, *ConstraintClassExtension; |__ Constraint classes have the Constraint class fields immedi- ately following the Composite class fields. __ | typedef struct _ConstraintClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ConstraintClassPart constraint_class; } ConstraintClassRec, *ConstraintWidgetClass; |__ The single occurrences of the class record and pointer for creating instances of Constraint are In IntrinsicP.h: 12 X Toolkit Intrinsics X11 Release 6.4 __ | extern ConstraintClassRec constraintClassRec; |__ In Intrinsic.h: __ | extern WidgetClass constraintWidgetClass; |__ The opaque types ConstraintWidget and ConstraintWidgetClass and the opaque variable constraintWidgetClass are defined for generic operations on widgets whose class is Constraint or a subclass of Constraint. The symbolic constant for the ConstraintClassExtension version identifier is XtConstrain- tExtensionVersion (see Section 1.6.12). Intrinsic.h uses an incomplete structure definition to ensure that the compiler catches attempts to access private data. __ | typedef struct _ConstraintClassRec *ConstraintWidgetClass; |__ 1.4.3.2. ConstraintPart Structure In addition to the Core and Composite instance fields, wid- gets of the Constraint class have the following unused instance fields defined in the ConstraintPart structure __ | typedef struct { int empty; } ConstraintPart; |__ Constraint widgets have the Constraint instance fields imme- diately following the Composite instance fields. 13 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { CorePart core; CompositePart composite; ConstraintPart constraint; } ConstraintRec, *ConstraintWidget; |__ Intrinsic.h uses an incomplete structure definition to ensure that the compiler catches attempts to access private data. __ | typedef struct _ConstraintRec *ConstraintWidget; |__ 1.4.3.3. Constraint Resources The constraintClassRec core_class and constraint_class resources fields are NULL, and the num_resources fields are zero; no additional resources beyond those declared by the superclasses are defined for Constraint. 1.5. Implementation-Specific Types To increase the portability of widget and application source code between different system environments, the Intrinsics define several types whose precise representation is explic- itly dependent upon, and chosen by, each individual imple- mentation of the Intrinsics. These implementation-defined types are Boolean A datum that contains a zero or nonzero value. Unless explicitly stated, clients should not assume that the nonzero value is equal to the symbolic value True. Cardinal An unsigned integer datum with a minimum range of [0..2^16-1]. Dimension An unsigned integer datum with a minimum range of [0..2^16-1]. Position A signed integer datum with a minimum range of [-2^15..2^15-1]. XtPointer A datum large enough to contain the largest of a char*, int*, function pointer, structure pointer, 14 X Toolkit Intrinsics X11 Release 6.4 or long value. A pointer to any type or func- tion, or a long value may be converted to an XtPointer and back again and the result will com- pare equal to the original value. In ANSI C environments it is expected that XtPointer will be defined as void*. XtArgVal A datum large enough to contain an XtPointer, Cardinal, Dimension, or Position value. XtEnum An integer datum large enough to encode at least 128 distinct values, two of which are the sym- bolic values True and False. The symbolic values TRUE and FALSE are also defined to be equal to True and False, respectively. In addition to these specific types, the precise order of the fields within the structure declarations for any of the instance part records ObjectPart, RectObjPart, CorePart, CompositePart, ShellPart, WMShellPart, TopLevelShellPart, and ApplicationShellPart is implementation-defined. These structures may also have additional private fields internal to the implementation. The ObjectPart, RectObjPart, and CorePart structures must be defined so that any member with the same name appears at the same offset in ObjectRec, Rect- ObjRec, and CoreRec (WidgetRec). No other relations between the offsets of any two fields may be assumed. 1.6. Widget Classing The widget_class field of a widget points to its widget class structure, which contains information that is constant across all widgets of that class. As a consequence, widgets usually do not implement directly callable procedures; rather, they implement procedures, called methods, that are available through their widget class structure. These meth- ods are invoked by generic procedures that envelop common actions around the methods implemented by the widget class. Such procedures are applicable to all widgets of that class and also to widgets whose classes are subclasses of that class. All widget classes are a subclass of Core and can be sub- classed further. Subclassing reduces the amount of code and declarations necessary to make a new widget class that is similar to an existing class. For example, you do not have to describe every resource your widget uses in an XtRe- sourceList. Instead, you describe only the resources your widget has that its superclass does not. Subclasses usually inherit many of their superclasses' procedures (for example, the expose procedure or geometry handler). 15 X Toolkit Intrinsics X11 Release 6.4 Subclassing, however, can be taken too far. If you create a subclass that inherits none of the procedures of its super- class, you should consider whether you have chosen the most appropriate superclass. To make good use of subclassing, widget declarations and naming conventions are highly stylized. A widget consists of three files: o A public .h file, used by client widgets or applica- tions. o A private .h file, used by widgets whose classes are subclasses of the widget class. o A .c file, which implements the widget. 1.6.1. Widget Naming Conventions The Intrinsics provide a vehicle by which programmers can create new widgets and organize a collection of widgets into an application. To ensure that applications need not deal with as many styles of capitalization and spelling as the number of widget classes it uses, the following guidelines should be followed when writing new widgets: o Use the X library naming conventions that are applica- ble. For example, a record component name is all low- ercase and uses underscores (_) for compound words (for example, background_pixmap). Type and procedure names start with uppercase and use capitalization for com- pound words (for example, ArgList or XtSetValues). o A resource name is spelled identically to the field name except that compound names use capitalization rather than underscore. To let the compiler catch spelling errors, each resource name should have a sym- bolic identifier prefixed with ``XtN''. For example, the background_pixmap field has the corresponding iden- tifier XtNbackgroundPixmap, which is defined as the string ``backgroundPixmap''. Many predefined names are listed in . Before you invent a new name, you should make sure there is not already a name that you can use. o A resource class string starts with a capital letter and uses capitalization for compound names (for exam- ple,``BorderWidth''). Each resource class string should have a symbolic identifier prefixed with ``XtC'' (for example, XtCBorderWidth). Many predefined classes are listed in . 16 X Toolkit Intrinsics X11 Release 6.4 o A resource representation string is spelled identically to the type name (for example, ``TranslationTable''). Each representation string should have a symbolic iden- tifier prefixed with ``XtR'' (for example, XtRTransla- tionTable). Many predefined representation types are listed in . o New widget classes start with a capital and use upper- case for compound words. Given a new class name AbcXyz, you should derive several names: - Additional widget instance structure part name AbcXyzPart. - Complete widget instance structure names AbcXyzRec and _AbcXyzRec. - Widget instance structure pointer type name AbcXyzWidget. - Additional class structure part name AbcXyzClass- Part. - Complete class structure names AbcXyzClassRec and _AbcXyzClassRec. - Class structure pointer type name AbcXyzWidget- Class. - Class structure variable abcXyzClassRec. - Class structure pointer variable abcXyzWidget- Class. o Action procedures available to translation specifica- tions should follow the same naming conventions as pro- cedures. That is, they start with a capital letter, and compound names use uppercase (for example, ``High- light'' and ``NotifyClient''). The symbolic identifiers XtN..., XtC..., and XtR... may be implemented as macros, as global symbols, or as a mixture of the two. The (implicit) type of the identifier is String. The pointer value itself is not significant; clients must not assume that inequality of two identifiers implies inequality of the resource name, class, or representation string. Clients should also note that although global sym- bols permit savings in literal storage in some environments, they also introduce the possibility of multiple definition conflicts when applications attempt to use independently developed widgets simultaneously. 17 X Toolkit Intrinsics X11 Release 6.4 1.6.2. Widget Subclassing in Public .h Files The public .h file for a widget class is imported by clients and contains o A reference to the public .h file for the superclass. o Symbolic identifiers for the names and classes of the new resources that this widget adds to its superclass. The definitions should have a single space between the definition name and the value and no trailing space or comment in order to reduce the possibility of compiler warnings from similar declarations in multiple classes. o Type declarations for any new resource data types defined by the class. o The class record pointer variable used to create widget instances. o The C type that corresponds to widget instances of this class. o Entry points for new class methods. For example, the following is the public .h file for a pos- sible implementation of a Label widget: #ifndef LABEL_H #define LABEL_H /* New resources */ #define XtNjustify "justify" #define XtNforeground "foreground" #define XtNlabel "label" #define XtNfont "font" #define XtNinternalWidth "internalWidth" #define XtNinternalHeight "internalHeight" /* Class record pointer */ extern WidgetClass labelWidgetClass; /* C Widget type definition */ typedef struct _LabelRec *LabelWidget; /* New class method entry points */ extern void LabelSetText(); /* Widget w */ /* String text */ extern String LabelGetText(); /* Widget w */ 18 X Toolkit Intrinsics X11 Release 6.4 #endif LABEL_H The conditional inclusion of the text allows the application to include header files for different widgets without being concerned that they already may be included as a superclass of another widget. To accommodate operating systems with file name length restrictions, the name of the public .h file is the first ten characters of the widget class. For example, the public .h file for the Constraint widget class is Constraint.h. 1.6.3. Widget Subclassing in Private .h Files The private .h file for a widget is imported by widget classes that are subclasses of the widget and contains o A reference to the public .h file for the class. o A reference to the private .h file for the superclass. o Symbolic identifiers for any new resource representa- tion types defined by the class. The definitions should have a single space between the definition name and the value and no trailing space or comment. o A structure part definition for the new fields that the widget instance adds to its superclass's widget struc- ture. o The complete widget instance structure definition for this widget. o A structure part definition for the new fields that this widget class adds to its superclass's constraint structure if the widget class is a subclass of Con- straint. o The complete constraint structure definition if the widget class is a subclass of Constraint. o Type definitions for any new procedure types used by class methods declared in the widget class part. o A structure part definition for the new fields that this widget class adds to its superclass's widget class structure. o The complete widget class structure definition for this widget. 19 X Toolkit Intrinsics X11 Release 6.4 o The complete widget class extension structure defini- tion for this widget, if any. o The symbolic constant identifying the class extension version, if any. o The name of the global class structure variable con- taining the generic class structure for this class. o An inherit constant for each new procedure in the wid- get class part structure. For example, the following is the private .h file for a pos- sible Label widget: #ifndef LABELP_H #define LABELP_H #include /* New representation types used by the Label widget */ #define XtRJustify "Justify" /* New fields for the Label widget record */ typedef struct { /* Settable resources */ Pixel foreground; XFontStruct *font; String label; /* text to display */ XtJustify justify; Dimension internal_width;/* # pixels horizontal border */ Dimension internal_height;/* # pixels vertical border */ /* Data derived from resources */ GC normal_GC; GC gray_GC; Pixmap gray_pixmap; Position label_x; Position label_y; Dimension label_width; Dimension label_height; Cardinal label_len; Boolean display_sensitive; } LabelPart; /* Full instance record declaration */ typedef struct _LabelRec { CorePart core; LabelPart label; } LabelRec; 20 X Toolkit Intrinsics X11 Release 6.4 /* Types for Label class methods */ typedef void (*LabelSetTextProc)(); /* Widget w */ /* String text */ typedef String (*LabelGetTextProc)(); /* Widget w */ /* New fields for the Label widget class record */ typedef struct { LabelSetTextProc set_text; LabelGetTextProc get_text; XtPointer extension; } LabelClassPart; /* Full class record declaration */ typedef struct _LabelClassRec { CoreClassPart core_class; LabelClassPart label_class; } LabelClassRec; /* Class record variable */ extern LabelClassRec labelClassRec; #define LabelInheritSetText((LabelSetTextProc)_XtInherit) #define LabelInheritGetText((LabelGetTextProc)_XtInherit) #endif LABELP_H To accommodate operating systems with file name length restrictions, the name of the private .h file is the first nine characters of the widget class followed by a capital P. For example, the private .h file for the Constraint widget class is ConstrainP.h. 1.6.4. Widget Subclassing in .c Files The .c file for a widget contains the structure initializer for the class record variable, which contains the following parts: o Class information (for example, superclass, class_name, widget_size, class_initialize, and class_inited). o Data constants (for example, resources and num_resources, actions and num_actions, visible_inter- est, compress_motion, compress_exposure, and version). o Widget operations (for example, initialize, realize, destroy, resize, expose, set_values, accept_focus, and any new operations specific to the widget). 21 X Toolkit Intrinsics X11 Release 6.4 The superclass field points to the superclass global class record, declared in the superclass private .h file. For direct subclasses of the generic core widget, superclass should be initialized to the address of the widgetClassRec structure. The superclass is used for class chaining opera- tions and for inheriting or enveloping a superclass's opera- tions (see Sections 1.6.7, 1.6.9, and 1.6.10). The class_name field contains the text name for this class, which is used by the resource manager. For example, the Label widget has the string ``Label''. More than one widget class can share the same text class name. This string must be permanently allocated prior to or during the execution of the class initialization procedure and must not be subse- quently deallocated. The widget_size field is the size of the corresponding wid- get instance structure (not the size of the class struc- ture). The version field indicates the toolkit implementation ver- sion number and is used for runtime consistency checking of the X Toolkit and widgets in an application. Widget writers must set it to the implementation-defined symbolic value XtVersion in the widget class structure initialization. Those widget writers who believe that their widget binaries are compatible with other implementations of the Intrinsics can put the special value XtVersionDontCheck in the version field to disable version checking for those widgets. If a widget needs to compile alternative code for different revi- sions of the Intrinsics interface definition, it may use the symbol XtSpecificationRelease, as described in Chapter 13. Use of XtVersion allows the Intrinsics implementation to recognize widget binaries that were compiled with older implementations. The extension field is for future upward compatibility. If the widget programmer adds fields to class parts, all sub- class structure layouts change, requiring complete recompi- lation. To allow clients to avoid recompilation, an exten- sion field at the end of each class part can point to a record that contains any additional class information required. All other fields are described in their respective sections. The .c file also contains the declaration of the global class structure pointer variable used to create instances of the class. The following is an abbreviated version of the .c file for a Label widget. The resources table is described in Chapter 9. 22 X Toolkit Intrinsics X11 Release 6.4 /* Resources specific to Label */ static XtResource resources[] = { {XtNforeground, XtCForeground, XtRPixel, sizeof(Pixel), XtOffset(LabelWidget, label.foreground), XtRString, XtDefaultForeground}, {XtNfont, XtCFont, XtRFontStruct, sizeof(XFontStruct *), XtOffset(LabelWidget, label.font),XtRString, XtDefaultFont}, {XtNlabel, XtCLabel, XtRString, sizeof(String), XtOffset(LabelWidget, label.label), XtRString, NULL}, . . . } /* Forward declarations of procedures */ static void ClassInitialize(); static void Initialize(); static void Realize(); static void SetText(); static void GetText(); . . . /* Class record constant */ LabelClassRec labelClassRec = { { /* core_class fields */ /* superclass */ (WidgetClass)&coreClassRec, /* class_name */ "Label", /* widget_size */ sizeof(LabelRec), /* class_initialize */ClassInitialize, /* class_part_initialize */NULL, /* class_inited */False, /* initialize */ Initialize, /* initialize_hook */NULL, /* realize */ Realize, /* actions */ NULL, /* num_actions */ 0, /* resources */ resources, /* num_resources */XtNumber(resources), /* xrm_class */ NULLQUARK, /* compress_motion */True, /* compress_exposure */True, /* compress_enterleave */True, /* visible_interest */False, /* destroy */ NULL, /* resize */ Resize, /* expose */ Redisplay, /* set_values */ SetValues, /* set_values_hook */NULL, 23 X Toolkit Intrinsics X11 Release 6.4 /* set_values_almost */XtInheritSetValuesAlmost, /* get_values_hook */NULL, /* accept_focus */NULL, /* version */ XtVersion, /* callback_offsets */NULL, /* tm_table */ NULL, /* query_geometry */XtInheritQueryGeometry, /* display_accelerator */NULL, /* extension */ NULL }, { /* Label_class fields */ /* get_text */ GetText, /* set_text */ SetText, /* extension */ NULL } }; /* Class record pointer */ WidgetClass labelWidgetClass = (WidgetClass) &labelClassRec; /* New method access routines */ void LabelSetText(w, text) Widget w; String text; { Label WidgetClass lwc = (Label WidgetClass)XtClass(w); XtCheckSubclass(w, labelWidgetClass, NULL); *(lwc->label_class.set_text)(w, text) } /* Private procedures */ . . . 1.6.5. Widget Class and Superclass Look Up To obtain the class of a widget, use XtClass. __ | WidgetClass XtClass(w) Widget w; w Specifies the widget. Must be of class Object or any subclass thereof. |__ The XtClass function returns a pointer to the widget's class structure. 24 X Toolkit Intrinsics X11 Release 6.4 To obtain the superclass of a widget, use XtSuperclass. __ | WidgetClass XtSuperclass(w) Widget w; w Specifies the widget. Must be of class Object or any subclass thereof. |__ The XtSuperclass function returns a pointer to the widget's superclass class structure. 1.6.6. Widget Subclass Verification To check the subclass to which a widget belongs, use XtIs- Subclass. __ | Boolean XtIsSubclass(w, widget_class) Widget w; WidgetClass widget_class; w Specifies the widget or object instance whose class is to be checked. Must be of class Object or any subclass thereof. widget_class Specifies the widget class for which to test. Must be objectClass or any subclass thereof. |__ The XtIsSubclass function returns True if the class of the specified widget is equal to or is a subclass of the speci- fied class. The widget's class can be any number of sub- classes down the chain and need not be an immediate subclass of the specified class. Composite widgets that need to restrict the class of the items they contain can use XtIs- Subclass to find out if a widget belongs to the desired class of objects. To test if a given widget belongs to a subclass of an Intrinsics-defined class, the Intrinsics define macros or functions equivalent to XtIsSubclass for each of the built- in classes. These procedures are XtIsObject, XtIsRectObj, XtIsWidget, XtIsComposite, XtIsConstraint, XtIsShell, XtIsOverrideShell, XtIsWMShell, XtIsVendorShell, XtIsTran- sientShell, XtIsTopLevelShell, XtIsApplicationShell, and 25 X Toolkit Intrinsics X11 Release 6.4 XtIsSessionShell. All these macros and functions have the same argument description. __ | Boolean XtIs (w) Widget w; w Specifies the widget or object instance whose class is to be checked. Must be of class Object or any subclass thereof. |__ These procedures may be faster than calling XtIsSubclass directly for the built-in classes. To check a widget's class and to generate a debugging error message, use XtCheckSubclass, defined in : __ | void XtCheckSubclass(w, widget_class, message) Widget w; WidgetClass widget_class; String message; w Specifies the widget or object whose class is to be checked. Must be of class Object or any sub- class thereof. widget_class Specifies the widget class for which to test. Must be objectClass or any subclass thereof. message Specifies the message to be used. |__ The XtCheckSubclass macro determines if the class of the specified widget is equal to or is a subclass of the speci- fied class. The widget's class can be any number of sub- classes down the chain and need not be an immediate subclass of the specified class. If the specified widget's class is not a subclass, XtCheckSubclass constructs an error message from the supplied message, the widget's actual class, and the expected class and calls XtErrorMsg. XtCheckSubclass should be used at the entry point of exported routines to ensure that the client has passed in a valid widget class for the exported operation. 26 X Toolkit Intrinsics X11 Release 6.4 XtCheckSubclass is only executed when the module has been compiled with the compiler symbol DEBUG defined; otherwise, it is defined as the empty string and generates no code. 1.6.7. Superclass Chaining While most fields in a widget class structure are self-con- tained, some fields are linked to their corresponding fields in their superclass structures. With a linked field, the Intrinsics access the field's value only after accessing its corresponding superclass value (called downward superclass chaining) or before accessing its corresponding superclass value (called upward superclass chaining). The self-con- tained fields are In all widget classes:class_name class_initialize widget_size realize visible_interest resize expose accept_focus compress_motion compress_exposure compress_enterleave set_values_almost tm_table version allocate deallocate In Composite widget classes:geometry_manager change_managed insert_child delete_child accepts_objects allows_change_managed_set In Constraint widget classes:constraint_size In Shell widget classes:root_geometry_manager With downward superclass chaining, the invocation of an operation first accesses the field from the Object, RectObj, and Core class structures, then from the subclass structure, and so on down the class chain to that widget's class struc- ture. These superclass-to-subclass fields are class_part_initialize get_values_hook initialize 27 X Toolkit Intrinsics X11 Release 6.4 initialize_hook set_values set_values_hook resources In addition, for subclasses of Constraint, the following fields of the ConstraintClassPart and ConstraintClassExten- sionRec structures are chained from the Constraint class down to the subclass: resources initialize set_values get_values_hook With upward superclass chaining, the invocation of an opera- tion first accesses the field from the widget class struc- ture, then from the superclass structure, and so on up the class chain to the Core, RectObj, and Object class struc- tures. The subclass-to-superclass fields are destroy actions For subclasses of Constraint, the following field of Con- straintClassPart is chained from the subclass up to the Con- straint class: destroy 1.6.8. Class Initialization: class_initialize and class_part_initialize Procedures Many class records can be initialized completely at compile or link time. In some cases, however, a class may need to register type converters or perform other sorts of once-only runtime initialization. Because the C language does not have initialization proce- dures that are invoked automatically when a program starts up, a widget class can declare a class_initialize procedure that will be automatically called exactly once by the Intrinsics. A class initialization procedure pointer is of type XtProc: 28 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtProc)(void); |__ A widget class indicates that it has no class initialization procedure by specifying NULL in the class_initialize field. In addition to the class initialization that is done exactly once, some classes perform initialization for fields in their parts of the class record. These are performed not just for the particular class, but for subclasses as well, and are done in the class's class part initialization proce- dure, a pointer to which is stored in the class_part_ini- tialize field. The class_part_initialize procedure pointer is of type XtWidgetClassProc. __ | typedef void (*XtWidgetClassProc)(WidgetClass); WidgetClass widget_class; widget_class Points to the class structure for the class being initialized. |__ During class initialization, the class part initialization procedures for the class and all its superclasses are called in superclass-to-subclass order on the class record. These procedures have the responsibility of doing any dynamic ini- tializations necessary to their class's part of the record. The most common is the resolution of any inherited methods defined in the class. For example, if a widget class C has superclasses Core, Composite, A, and B, the class record for C first is passed to Core 's class_part_initialize proce- dure. This resolves any inherited Core methods and compiles the textual representations of the resource list and action table that are defined in the class record. Next, Compos- ite's class_part_initialize procedure is called to initial- ize the composite part of C's class record. Finally, the class_part_initialize procedures for A, B, and C, in that order, are called. For further information, see Section 1.6.9. Classes that do not define any new class fields or that need no extra processing for them can specify NULL in the class_part_initialize field. All widget classes, whether they have a class initialization procedure or not, must start with their class_inited field False. The first time a widget of a class is created, XtCreateWid- get ensures that the widget class and all superclasses are 29 X Toolkit Intrinsics X11 Release 6.4 initialized, in superclass-to-subclass order, by checking each class_inited field and, if it is False, by calling the class_initialize and the class_part_initialize procedures for the class and all its superclasses. The Intrinsics then set the class_inited field to a nonzero value. After the one-time initialization, a class structure is constant. The following example provides the class initialization pro- cedure for a Label class. static void ClassInitialize() { XtSetTypeConverter(XtRString, XtRJustify, CvtStringToJustify, NULL, 0, XtCacheNone, NULL); } 1.6.9. Initializing a Widget Class A class is initialized when the first widget of that class or any subclass is created. To initialize a widget class without creating any widgets, use XtInitializeWidgetClass. __ | void XtInitializeWidgetClass(object_class) WidgetClass object_class; object_class Specifies the object class to initialize. May be objectClass or any subclass thereof. |__ If the specified widget class is already initialized, XtIni- tializeWidgetClass returns immediately. If the class initialization procedure registers type con- verters, these type converters are not available until the first object of the class or subclass is created or XtIni- tializeWidgetClass is called (see Section 9.6). 1.6.10. Inheritance of Superclass Operations A widget class is free to use any of its superclass's self- contained operations rather than implementing its own code. The most frequently inherited operations are expose 30 X Toolkit Intrinsics X11 Release 6.4 realize insert_child delete_child geometry_manager set_values_almost To inherit an operation xyz, specify the constant XtIn- heritXyz in your class record. Every class that declares a new procedure in its widget class part must provide for inheriting the procedure in its class_part_initialize procedure. The chained operations declared in Core and Constraint records are never inherited. Widget classes that do nothing beyond what their superclass does specify NULL for chained procedures in their class records. Inheriting works by comparing the value of the field with a known, special value and by copying in the superclass's value for that field if a match occurs. This special value, called the inheritance constant, is usually the Intrinsics internal value _XtInherit cast to the appropriate type. _XtInherit is a procedure that issues an error message if it is actually called. For example, CompositeP.h contains these definitions: #define XtInheritGeometryManager ((XtGeometryHandler) _XtInherit) #define XtInheritChangeManaged ((XtWidgetProc) _XtInherit) #define XtInheritInsertChild ((XtArgsProc) _XtInherit) #define XtInheritDeleteChild ((XtWidgetProc) _XtInherit) Composite's class_part_initialize procedure begins as fol- lows: static void CompositeClassPartInitialize(widgetClass) WidgetClass widgetClass; { CompositeWidgetClass wc = (CompositeWidgetClass)widgetClass; CompositeWidgetClass super = (CompositeWidgetClass)wc->core_class.superclass; if (wc->composite_class.geometry_manager == XtInheritGeometryManager) { wc->composite_class.geometry_manager = super->composite_class.geometry_manager; } if (wc->composite_class.change_managed == XtInheritChangeManaged) { wc->composite_class.change_managed = super->composite_class.change_managed; 31 X Toolkit Intrinsics X11 Release 6.4 } . . . Nonprocedure fields may be inherited in the same manner as procedure fields. The class may declare any reserved value it wishes for the inheritance constant for its new fields. The following inheritance constants are defined: For Object: XtInheritAllocate XtInheritDeallocate For Core: XtInheritRealize XtInheritResize XtInheritExpose XtInheritSetValuesAlmost XtInheritAcceptFocus XtInheritQueryGeometry XtInheritTranslations XtInheritDisplayAccelerator For Composite: XtInheritGeometryManager XtInheritChangeManaged XtInheritInsertChild XtInheritDeleteChild For Shell: XtInheritRootGeometryManager 1.6.11. Invocation of Superclass Operations A widget sometimes needs to call a superclass operation that is not chained. For example, a widget's expose procedure 32 X Toolkit Intrinsics X11 Release 6.4 might call its superclass's expose and then perform a little more work on its own. For example, a Composite class with predefined managed children can implement insert_child by first calling its superclass's insert_child and then calling XtManageChild to add the child to the managed set. Note A class method should not use XtSuperclass but should instead call the class method of its own specific superclass directly through the super- class record. That is, it should use its own class pointers only, not the widget's class point- ers, as the widget's class may be a subclass of the class whose implementation is being refer- enced. This technique is referred to as enveloping the superclass's operation. 1.6.12. Class Extension Records It may be necessary at times to add new fields to already existing widget class structures. To permit this to be done without requiring recompilation of all subclasses, the last field in a class part structure should be an extension pointer. If no extension fields for a class have yet been defined, subclasses should initialize the value of the extension pointer to NULL. If extension fields exist, as is the case with the Compos- ite, Constraint, and Shell classes, subclasses can provide values for these fields by setting the extension pointer for the appropriate part in their class structure to point to a statically declared extension record containing the addi- tional fields. Setting the extension field is never manda- tory; code that uses fields in the extension record must always check the extension field and take some appropriate default action if it is NULL. In order to permit multiple subclasses and libraries to chain extension records from a single extension field, extension records should be declared as a linked list, and each extension record definition should contain the follow- ing four fields at the beginning of the structure declara- tion: 33 X Toolkit Intrinsics X11 Release 6.4 __ | struct { XtPointer next_extension; XrmQuark record_type; long version; Cardinal record_size; }; next_extension Specifies the next record in the list, or NULL. record_type Specifies the particular structure declaration to which each extension record instance con- forms. version Specifies a version id symbolic constant sup- plied by the definer of the structure. record_size Specifies the total number of bytes allocated for the extension record. |__ The record_type field identifies the contents of the exten- sion record and is used by the definer of the record to locate its particular extension record in the list. The record_type field is normally assigned the result of Xrm- StringToQuark for a registered string constant. The Intrin- sics reserve all record type strings beginning with the two characters ``XT'' for future standard uses. The value NUL- LQUARK may also be used by the class part owner in extension records attached to its own class part extension field to identify the extension record unique to that particular class. The version field is an owner-defined constant that may be used to identify binary files that have been compiled with alternate definitions of the remainder of the extension record data structure. The private header file for a widget class should provide a symbolic constant for subclasses to use to initialize this field. The record_size field value includes the four common header fields and should normally be initialized with sizeof(). Any value stored in the class part extension fields of Com- positeClassPart, ConstraintClassPart, or ShellClassPart must point to an extension record conforming to this definition. The Intrinsics provide a utility function for widget writers to locate a particular class extension record in a linked list, given a widget class and the offset of the extension field in the class record. 34 X Toolkit Intrinsics X11 Release 6.4 To locate a class extension record, use XtGetClassExtension. __ | XtPointer XtGetClassExtension(object_class, byte_offset, type, version, record_size) WidgetClass object_class; Cardinal byte_offset; XrmQuark type; long version; Cardinal record_size; object_class Specifies the object class containing the exten- sion list to be searched. byte_offset Specifies the offset in bytes from the base of the class record of the extension field to be searched. type Specifies the record_type of the class extension to be located. version Specifies the minimum acceptable version of the class extension required for a match. record_size Specifies the minimum acceptable length of the class extension record required for a match, or 0. |__ The list of extension records at the specified offset in the specified object class will be searched for a match on the specified type, a version greater than or equal to the spec- ified version, and a record size greater than or equal the specified record_size if it is nonzero. XtGetClassExtension returns a pointer to a matching extension record or NULL if no match is found. The returned extension record must not be modified or freed by the caller if the caller is not the extension owner. 35 X Toolkit Intrinsics X11 Release 6.4 Chapter 2 Widget Instantiation A hierarchy of widget instances constitutes a widget tree. The shell widget returned by XtAppCreateShell is the root of the widget tree instance. The widgets with one or more children are the intermediate nodes of that tree, and the widgets with no children of any kind are the leaves of the widget tree. With the exception of pop-up children (see Chapter 5), this widget tree instance defines the associated X Window tree. Widgets can be either composite or primitive. Both kinds of widgets can contain children, but the Intrinsics provide a set of management mechanisms for constructing and interfac- ing between composite widgets, their children, and other clients. Composite widgets, that is, members of the class compos- iteWidgetClass, are containers for an arbitrary, but widget implementation-defined, collection of children, which may be instantiated by the composite widget itself, by other clients, or by a combination of the two. Composite widgets also contain methods for managing the geometry (layout) of any child widget. Under unusual circumstances, a composite widget may have zero children, but it usually has at least one. By contrast, primitive widgets that contain children typically instantiate specific children of known classes themselves and do not expect external clients to do so. Primitive widgets also do not have general geometry manage- ment methods. In addition, the Intrinsics recursively perform many opera- tions (for example, realization and destruction) on compos- ite widgets and all their children. Primitive widgets that have children must be prepared to perform the recursive operations themselves on behalf of their children. A widget tree is manipulated by several Intrinsics func- tions. For example, XtRealizeWidget traverses the tree downward and recursively realizes all pop-up widgets and children of composite widgets. XtDestroyWidget traverses the tree downward and destroys all pop-up widgets and chil- dren of composite widgets. The functions that fetch and modify resources traverse the tree upward and determine the inheritance of resources from a widget's ancestors. XtMake- GeometryRequest traverses the tree up one level and calls the geometry manager that is responsible for a widget child's geometry. 36 X Toolkit Intrinsics X11 Release 6.4 To facilitate upward traversal of the widget tree, each wid- get has a pointer to its parent widget. The Shell widget that XtAppCreateShell returns has a parent pointer of NULL. To facilitate downward traversal of the widget tree, the children field of each composite widget is a pointer to an array of child widgets, which includes all normal children created, not just the subset of children that are managed by the composite widget's geometry manager. Primitive widgets that instantiate children are entirely responsible for all operations that require downward traversal below themselves. In addition, every widget has a pointer to an array of pop- up children. 2.1. Initializing the X Toolkit Before an application can call any Intrinsics function other than XtSetLanguageProc and XtToolkitThreadInitialize, it must initialize the Intrinsics by using o XtToolkitInitialize, which initializes the Intrinsics internals o XtCreateApplicationContext, which initializes the per- application state o XtDisplayInitialize or XtOpenDisplay, which initializes the per-display state o XtAppCreateShell, which creates the root of a widget tree Or an application can call the convenience procedure XtOpe- nApplication, which combines the functions of the preceding procedures. An application wishing to use the ANSI C locale mechanism should call XtSetLanguageProc prior to calling XtDisplayInitialize, XtOpenDisplay, XtOpenApplication, or XtAppInitialize. Multiple instances of X Toolkit applications may be imple- mented in a single address space. Each instance needs to be able to read input and dispatch events independently of any other instance. Further, an application instance may need multiple display connections to have widgets on multiple displays. From the application's point of view, multiple display connections usually are treated together as a single unit for purposes of event dispatching. To accommodate both requirements, the Intrinsics define application contexts, each of which provides the information needed to distinguish one application instance from another. The major component of an application context is a list of one or more X Display pointers for that application. The Intrinsics handle all display connections within a single application context 37 X Toolkit Intrinsics X11 Release 6.4 simultaneously, handling input in a round-robin fashion. The application context type XtAppContext is opaque to clients. To initialize the Intrinsics internals, use XtToolkitIni- tialize. __ | void XtToolkitInitialize() |__ If XtToolkitInitialize was previously called, it returns immediately. When XtToolkitThreadInitialize is called before XtToolkitInitialize, the latter is protected against simultaneous activation by multiple threads. To create an application context, use XtCreateApplication- Context. __ | XtAppContext XtCreateApplicationContext() |__ The XtCreateApplicationContext function returns an applica- tion context, which is an opaque type. Every application must have at least one application context. To destroy an application context and close any remaining display connections in it, use XtDestroyApplicationContext. __ | void XtDestroyApplicationContext(app_context) XtAppContext app_context; app_context Specifies the application context. |__ The XtDestroyApplicationContext function destroys the speci- fied application context. If called from within an event dispatch (for example, in a callback procedure), XtDestroy- ApplicationContext does not destroy the application context until the dispatch is complete. 38 X Toolkit Intrinsics X11 Release 6.4 To get the application context in which a given widget was created, use XtWidgetToApplicationContext. __ | XtAppContext XtWidgetToApplicationContext(w) Widget w; w Specifies the widget for which you want the appli- cation context. Must be of class Object or any subclass thereof. |__ The XtWidgetToApplicationContext function returns the appli- cation context for the specified widget. To initialize a display and add it to an application con- text, use XtDisplayInitialize. 39 X Toolkit Intrinsics X11 Release 6.4 __ | void XtDisplayInitialize(app_context, display, application_name, application_class, options, num_options, argc, argv) XtAppContext app_context; Display *display; String application_name; String application_class; XrmOptionDescRec *options; Cardinal num_options; int *argc; String *argv; app_context Specifies the application context. display Specifies a previously opened display connec- tion. Note that a single display connection can be in at most one application context. application_name Specifies the name of the application instance. application_class Specifies the class name of this application, which is usually the generic name for all instances of this application. options Specifies how to parse the command line for any application-specific resources. The options argument is passed as a parameter to XrmParseCommand. For further information, see Section 15.9 in Xlib -- C Language X Interface and Section 2.4 of this specification. num_options Specifies the number of entries in the options list. argc Specifies a pointer to the number of command line parameters. argv Specifies the list of command line parameters. |__ The XtDisplayInitialize function retrieves the language string to be used for the specified display (see Section 11.11), calls the language procedure (if set) with that lan- guage string, builds the resource database for the default screen, calls the Xlib XrmParseCommand function to parse the command line, and performs other per-display initialization. After XrmParseCommand has been called, argc and argv contain only those parameters that were not in the standard option table or in the table specified by the options argument. If the modified argc is not zero, most applications simply 40 X Toolkit Intrinsics X11 Release 6.4 print out the modified argv along with a message listing the allowable options. On POSIX-based systems, the application name is usually the final component of argv[0]. If the syn- chronous resource is True, XtDisplayInitialize calls the Xlib XSynchronize function to put Xlib into synchronous mode for this display connection and any others currently open in the application context. See Sections 2.3 and 2.4 for details on the application_name, application_class, options, and num_options arguments. XtDisplayInitialize calls XrmSetDatabase to associate the resource database of the default screen with the display before returning. 41 X Toolkit Intrinsics X11 Release 6.4 To open a display, initialize it, and then add it to an application context, use XtOpenDisplay. __ | Display *XtOpenDisplay(app_context, display_string, application_name, application_class, options, num_options, argc, argv) XtAppContext app_context; String display_string; String application_name; String application_class; XrmOptionDescRec *options; Cardinal num_options; int *argc; String *argv; app_context Specifies the application context. display_string Specifies the display string, or NULL. application_name Specifies the name of the application instance, or NULL. application_class Specifies the class name of this application, which is usually the generic name for all instances of this application. options Specifies how to parse the command line for any application-specific resources. The options argument is passed as a parameter to XrmParseCommand. num_options Specifies the number of entries in the options list. argc Specifies a pointer to the number of command line parameters. argv Specifies the list of command line parameters. |__ The XtOpenDisplay function calls XOpenDisplay with the spec- ified display_string. If display_string is NULL, XtOpenDis- play uses the current value of the -display option specified in argv. If no display is specified in argv, the user's default display is retrieved from the environment. On POSIX-based systems, this is the value of the DISPLAY envi- ronment variable. 42 X Toolkit Intrinsics X11 Release 6.4 If this succeeds, XtOpenDisplay then calls XtDisplayInitial- ize and passes it the opened display and the value of the -name option specified in argv as the application name. If no -name option is specified and application_name is non- NULL, application_name is passed to XtDisplayInitialize. If application_name is NULL and if the environment variable RESOURCE_NAME is set, the value of RESOURCE_NAME is used. Otherwise, the application name is the name used to invoke the program. On implementations that conform to ANSI C Hosted Environment support, the application name will be argv[0] less any directory and file type components, that is, the final component of argv[0], if specified. If argv[0] does not exist or is the empty string, the applica- tion name is ``main''. XtOpenDisplay returns the newly opened display or NULL if it failed. See Section 7.12 for information regarding the use of XtOpenDisplay in multiple threads. To close a display and remove it from an application con- text, use XtCloseDisplay. __ | void XtCloseDisplay(display) Display *display; display Specifies the display. |__ The XtCloseDisplay function calls XCloseDisplay with the specified display as soon as it is safe to do so. If called from within an event dispatch (for example, a callback pro- cedure), XtCloseDisplay does not close the display until the dispatch is complete. Note that applications need only call XtCloseDisplay if they are to continue executing after clos- ing the display; otherwise, they should call XtDestroyAppli- cationContext. See Section 7.12 for information regarding the use of XtCloseDisplay in multiple threads. 2.2. Establishing the Locale Resource databases are specified to be created in the cur- rent process locale. During display initialization prior to creating the per-screen resource database, the Intrinsics will call out to a specified application procedure to set the locale according to options found on the command line or in the per-display resource specifications. 43 X Toolkit Intrinsics X11 Release 6.4 The callout procedure provided by the application is of type XtLanguageProc. __ | typedef String (*XtLanguageProc)(Display*, String, XtPointer); Display *display; String language; XtPointer client_data; display Passes the display. language Passes the initial language value obtained from the command line or server per-display resource specifications. client_data Passes the additional client data specified in the call to XtSetLanguageProc. |__ The language procedure allows an application to set the locale to the value of the language resource determined by XtDisplayInitialize. The function returns a new language string that will be subsequently used by XtDisplayInitialize to establish the path for loading resource files. The returned string will be copied by the Intrinsics into new memory. Initially, no language procedure is set by the Intrinsics. To set the language procedure for use by XtDisplayInitial- ize, use XtSetLanguageProc. __ | XtLanguageProc XtSetLanguageProc(app_context, proc, client_data) XtAppContext app_context; XtLanguageProc proc; XtPointer client_data; app_context Specifies the application context in which the language procedure is to be used, or NULL. proc Specifies the language procedure. client_data Specifies additional client data to be passed to the language procedure when it is called. |__ XtSetLanguageProc sets the language procedure that will be 44 X Toolkit Intrinsics X11 Release 6.4 called from XtDisplayInitialize for all subsequent Displays initialized in the specified application context. If app_context is NULL, the specified language procedure is registered in all application contexts created by the call- ing process, including any future application contexts that may be created. If proc is NULL, a default language proce- dure is registered. XtSetLanguageProc returns the previ- ously registered language procedure. If a language proce- dure has not yet been registered, the return value is unspecified, but if this return value is used in a subse- quent call to XtSetLanguageProc, it will cause the default language procedure to be registered. The default language procedure does the following: o Sets the locale according to the environment. On ANSI C-based systems this is done by calling setlocale( LC_ALL, language ). If an error is encountered, a warning message is issued with XtWarning. o Calls XSupportsLocale to verify that the current locale is supported. If the locale is not supported, a warn- ing message is issued with XtWarning and the locale is set to ``C''. o Calls XSetLocaleModifiers specifying the empty string. o Returns the value of the current locale. On ANSI C- based systems this is the return value from a final call to setlocale( LC_ALL, NULL ). A client wishing to use this mechanism to establish locale can do so by calling XtSetLanguageProc prior to XtDis- playInitialize, as in the following example. Widget top; XtSetLanguageProc(NULL, NULL, NULL); top = XtOpenApplication(...); ... 2.3. Loading the Resource Database The XtDisplayInitialize function first determines the lan- guage string to be used for the specified display. It then creates a resource database for the default screen of the display by combining the following sources in order, with the entries in the first named source having highest prece- dence: 45 X Toolkit Intrinsics X11 Release 6.4 o Application command line (argc, argv). o Per-host user environment resource file on the local host. o Per-screen resource specifications from the server. o Per-display resource specifications from the server or from the user preference file on the local host. o Application-specific user resource file on the local host. o Application-specific class resource file on the local host. When the resource database for a particular screen on the display is needed (either internally, or when XtScreen- Database is called), it is created in the following manner using the sources listed above in the same order: o A temporary database, the ``server resource database'', is created from the string returned by XResourceMan- agerString or, if XResourceManagerString returns NULL, the contents of a resource file in the user's home directory. On POSIX-based systems, the usual name for this user preference resource file is $HOME/.Xdefaults. o If a language procedure has been set, XtDisplayInitial- ize first searches the command line for the option ``-xnlLanguage'', or for a -xrm option that specifies the xnlLanguage/XnlLanguage resource, as specified by Section 2.4. If such a resource is found, the value is assumed to be entirely in XPCS, the X Portable Charac- ter Set. If neither option is specified on the command line, XtDisplayInitialize queries the server resource database (which is assumed to be entirely in XPCS) for the resource name.xnlLanguage, class Class.XnlLanguage where name and Class are the application_name and application_class specified to XtDisplayInitialize. The language procedure is then invoked with the resource value if found, else the empty string. The string returned from the language procedure is saved for all future references in the Intrinsics that require the per-display language string. o The screen resource database is initialized by parsing the command line in the manner specified by Section 2.4. 46 X Toolkit Intrinsics X11 Release 6.4 o If a language procedure has not been set, the initial database is then queried for the resource name.xnlLan- guage, class Class.XnlLanguage as specified above. If this database query fails, the server resource database is queried; if this query also fails, the language is determined from the environment; on POSIX-based sys- tems, this is done by retrieving the value of the LANG environment variable. If no language string is found, the empty string is used. This language string is saved for all future references in the Intrinsics that require the per-display language string. o After determining the language string, the user's envi- ronment resource file is then merged into the initial resource database if the file exists. This file is user-, host-, and process-specific and is expected to contain user preferences that are to override those specifications in the per-display and per-screen resources. On POSIX-based systems, the user's environ- ment resource file name is specified by the value of the XENVIRONMENT environment variable. If this envi- ronment variable does not exist, the user's home direc- tory is searched for a file named .Xdefaults-host, where host is the host name of the machine on which the application is running. o The per-screen resource specifications are then merged into the screen resource database, if they exist. These specifications are the string returned by XScreenResourceString for the respective screen and are owned entirely by the user. o Next, the server resource database created earlier is merged into the screen resource database. The server property, and corresponding user preference file, are owned and constructed entirely by the user. o The application-specific user resource file from the local host is then merged into the screen resource database. This file contains user customizations and is stored in a directory owned by the user. Either the user or the application or both can store resource specifications in the file. Each should be prepared to find and respect entries made by the other. The file name is found by calling XrmSetDatabase with the cur- rent screen resource database, after preserving the original display-associated database, then calling XtResolvePathname with the parameters (display, NULL, NULL, NULL, path, NULL, 0, NULL), where path is defined in an operating-system-specific way. On POSIX-based 47 X Toolkit Intrinsics X11 Release 6.4 systems, path is defined to be the value of the envi- ronment variable XUSERFILESEARCHPATH if this is defined. If XUSERFILESEARCHPATH is not defined, an implementation-dependent default value is used. This default value is constrained in the following manner: - If the environment variable XAPPLRESDIR is not defined, the default XUSERFILESEARCHPATH must con- tain at least six entries. These entries must con- tain $HOME as the directory prefix, plus the follow- ing substitutions: 1. %C, %N, %L or %C, %N, %l, %t, %c 2. %C, %N, %l 3. %C, %N 4. %N, %L or %N, %l, %t, %c 5. %N, %l 6. %N The order of these six entries within the path must be as given above. The order and use of substitu- tions within a given entry are implementation-depen- dent. - If XAPPLRESDIR is defined, the default XUSERFILE- SEARCHPATH must contain at least seven entries. These entries must contain the following directory prefixes and substitutions: 1. $XAPPLRESDIR with %C, %N, %L or %C, %N, %l, %t, %c 2. $XAPPLRESDIR with %C, %N, %l 3. $XAPPLRESDIR with %C, %N 4. $XAPPLRESDIR with %N, %L or %N, %l, %t, %c 5. $XAPPLRESDIR with %N, %l 6. $XAPPLRESDIR with %N 7. $HOME with %N The order of these seven entries within the path must be as given above. The order and use of sub- stitutions within a given entry are implementation- dependent. o Last, the application-specific class resource file from the local host is merged into the screen resource database. This file is owned by the application and is usually installed in a system directory when the appli- cation is installed. It may contain sitewide cus- tomizations specified by the system manager. The name of the application class resource file is found by calling XtResolvePathname with the parameters (display, ``app-defaults'', NULL, NULL, NULL, NULL, 0, NULL). 48 X Toolkit Intrinsics X11 Release 6.4 This file is expected to be provided by the developer of the application and may be required for the applica- tion to function properly. A simple application that wants to be assured of having a minimal set of resources in the absence of its class resource file can declare fallback resource specifications with XtAppSet- FallbackResources. Note that the customization substi- tution string is retrieved dynamically by XtRe- solvePathname so that the resolved file name of the application class resource file can be affected by any of the earlier sources for the screen resource database, even though the contents of the class resource file have lowest precedence. After calling XtResolvePathname, the original display-associated database is restored. To obtain the resource database for a particular screen, use XtScreenDatabase. __ | XrmDatabase XtScreenDatabase(screen) Screen *screen; screen Specifies the screen whose resource database is to be returned. |__ The XtScreenDatabase function returns the fully merged resource database as specified above, associated with the specified screen. If the specified screen does not belong to a Display initialized by XtDisplayInitialize, the results are undefined. To obtain the default resource database associated with a particular display, use XtDatabase. __ | XrmDatabase XtDatabase(display) Display *display; display Specifies the display. |__ The XtDatabase function is equivalent to XrmGetDatabase. It returns the database associated with the specified display, or NULL if a database has not been set. 49 X Toolkit Intrinsics X11 Release 6.4 To specify a default set of resource values that will be used to initialize the resource database if no application- specific class resource file is found (the last of the six sources listed above), use XtAppSetFallbackResources. __ | void XtAppSetFallbackResources(app_context, specification_list) XtAppContext app_context; String *specification_list; app_context Specifies the application context in which the fallback specifications will be used. specification_list Specifies a NULL-terminated list of resource specifications to preload the database, or NULL. |__ Each entry in specification_list points to a string in the format of XrmPutLineResource. Following a call to XtAppSet- FallbackResources, when a resource database is being created for a particular screen and the Intrinsics are not able to find or read an application-specific class resource file according to the rules given above and if specification_list is not NULL, the resource specifications in specifica- tion_list will be merged into the screen resource database in place of the application-specific class resource file. XtAppSetFallbackResources is not required to copy specifica- tion_list; the caller must ensure that the contents of the list and of the strings addressed by the list remain valid until all displays are initialized or until XtAppSetFall- backResources is called again. The value NULL for specifi- cation_list removes any previous fallback resource specifi- cation for the application context. The intended use for fallback resources is to provide a minimal number of resources that will make the application usable (or at least terminate with helpful diagnostic messages) when some prob- lem exists in finding and loading the application defaults file. 2.4. Parsing the Command Line The XtOpenDisplay function first parses the command line for the following options: -display Specifies the display name for XOpenDisplay. -name Sets the resource name prefix, which overrides the application name passed to XtOpenDisplay. 50 X Toolkit Intrinsics X11 Release 6.4 -xnllanguage Specifies the initial language string for estab- lishing locale and for finding application class resource files. XtDisplayInitialize has a table of standard command line options that are passed to XrmParseCommand for adding resources to the resource database, and it takes as a param- eter additional application-specific resource abbreviations. The format of this table is described in Section 15.9 in Xlib -- C Language X Interface. __ | typedef enum { XrmoptionNoArg, /* Value is specified in OptionDescRec.value */ XrmoptionIsArg, /* Value is the option string itself */ XrmoptionStickyArg, /* Value is characters immediately following option */ XrmoptionSepArg, /* Value is next argument in argv */ XrmoptionResArg, /* Use the next argument as input to XrmPutLineResource*/ XrmoptionSkipArg, /* Ignore this option and the next argument in argv */ XrmoptionSkipNArgs, /* Ignore this option and the next */ /* OptionDescRec.value arguments in argv */ XrmoptionSkipLine /* Ignore this option and the rest of argv */ } XrmOptionKind; typedef struct { char *option; /* Option name in argv */ char *specifier; /* Resource name (without application name) */ XrmOptionKind argKind;/* Location of the resource value */ XPointer value; /* Value to provide if XrmoptionNoArg */ } XrmOptionDescRec, *XrmOptionDescList; |__ The standard table contains the following entries: ----------------------------------------------------------------------- Option String Resource Name Argument Kind Resource Value ----------------------------------------------------------------------- -background *background SepArg next argument -bd *borderColor SepArg next argument -bg *background SepArg next argument -borderwidth .borderWidth SepArg next argument -bordercolor *borderColor SepArg next argument -bw .borderWidth SepArg next argument -display .display SepArg next argument -fg *foreground SepArg next argument -fn *font SepArg next argument -font *font SepArg next argument -foreground *foreground SepArg next argument -geometry .geometry SepArg next argument 51 X Toolkit Intrinsics X11 Release 6.4 ----------------------------------------------------------------------- -iconic .iconic NoArg ``true'' -name .name SepArg next argument -reverse .reverseVideo NoArg ``on'' -rv .reverseVideo NoArg ``on'' +rv .reverseVideo NoArg ``off'' -selectionTimeout .selectionTimeout SepArg next argument -synchronous .synchronous NoArg ``on'' +synchronous .synchronous NoArg ``off'' -title .title SepArg next argument -xnllanguage .xnlLanguage SepArg next argument -xrm next argument ResArg next argument -xtsessionID .sessionID SepArg next argument ----------------------------------------------------------------------- Note that any unique abbreviation for an option name in the standard table or in the application table is accepted. If reverseVideo is True, the values of XtDefaultForeground and XtDefaultBackground are exchanged for all screens on the Display. The value of the synchronous resource specifies whether or not Xlib is put into synchronous mode. If a value is found in the resource database during display initialization, XtDisplayInitialize makes a call to XSynchronize for all display connections currently open in the application con- text. Therefore, when multiple displays are initialized in the same application context, the most recent value speci- fied for the synchronous resource is used for all displays in the application context. The value of the selectionTimeout resource applies to all displays opened in the same application context. When mul- tiple displays are initialized in the same application con- text, the most recent value specified is used for all dis- plays in the application context. The -xrm option provides a method of setting any resource in an application. The next argument should be a quoted string identical in format to a line in the user resource file. For example, to give a red background to all command buttons in an application named xmh, you can start it up as xmh -xrm 'xmh*Command.background: red' When it parses the command line, XtDisplayInitialize merges the application option table with the standard option table before calling the Xlib XrmParseCommand function. An entry in the application table with the same name as an entry in the standard table overrides the standard table entry. If 52 X Toolkit Intrinsics X11 Release 6.4 an option name is a prefix of another option name, both names are kept in the merged table. The Intrinsics reserve all option names beginning with the characters ``-xt'' for future standard uses. 2.5. Creating Widgets The creation of widget instances is a three-phase process: 1. The widgets are allocated and initialized with resources and are optionally added to the managed sub- set of their parent. 2. All composite widgets are notified of their managed children in a bottom-up traversal of the widget tree. 3. The widgets create X windows, which then are mapped. To start the first phase, the application calls XtCreateWid- get for all its widgets and adds some (usually, most or all) of its widgets to their respective parents' managed set by calling XtManageChild. To avoid an O(n2) creation process where each composite widget lays itself out each time a wid- get is created and managed, parent widgets are not notified of changes in their managed set during this phase. After all widgets have been created, the application calls XtRealizeWidget with the top-level widget to execute the second and third phases. XtRealizeWidget first recursively traverses the widget tree in a postorder (bottom-up) traver- sal and then notifies each composite widget with one or more managed children by means of its change_managed procedure. Notifying a parent about its managed set involves geometry layout and possibly geometry negotiation. A parent deals with constraints on its size imposed from above (for exam- ple, when a user specifies the application window size) and suggestions made from below (for example, when a primitive child computes its preferred size). One difference between the two can cause geometry changes to ripple in both direc- tions through the widget tree. The parent may force some of its children to change size and position and may issue geom- etry requests to its own parent in order to better accommo- date all its children. You cannot predict where anything will go on the screen until this process finishes. Consequently, in the first and second phases, no X windows are actually created, because it is likely that they will get moved around after creation. This avoids unnecessary requests to the X server. Finally, XtRealizeWidget starts the third phase by making a preorder (top-down) traversal of the widget tree, allocates 53 X Toolkit Intrinsics X11 Release 6.4 an X window to each widget by means of its realize proce- dure, and finally maps the widgets that are managed. 2.5.1. Creating and Merging Argument Lists Many Intrinsics functions may be passed pairs of resource names and values. These are passed as an arglist, a pointer to an array of Arg structures, which contains __ | typedef struct { String name; XtArgVal value; } Arg, *ArgList; |__ where XtArgVal is as defined in Section 1.5. If the size of the resource is less than or equal to the size of an XtArgVal, the resource value is stored directly in value; otherwise, a pointer to it is stored in value. To set values in an ArgList, use XtSetArg. __ | void XtSetArg(arg, name, value) Arg arg; String name; XtArgVal value; arg Specifies the name/value pair to set. name Specifies the name of the resource. value Specifies the value of the resource if it will fit in an XtArgVal, else the address. |__ The XtSetArg function is usually used in a highly stylized manner to minimize the probability of making a mistake; for example: Arg args[20]; int n; n = 0; XtSetArg(args[n], XtNheight, 100);n++; XtSetArg(args[n], XtNwidth, 200);n++; 54 X Toolkit Intrinsics X11 Release 6.4 XtSetValues(widget, args, n); Alternatively, an application can statically declare the argument list and use XtNumber: static Args args[] = { {XtNheight, (XtArgVal) 100}, {XtNwidth, (XtArgVal) 200}, }; XtSetValues(Widget, args, XtNumber(args)); Note that you should not use expressions with side effects such as auto-increment or auto-decrement within the first argument to XtSetArg. XtSetArg can be implemented as a macro that evaluates the first argument twice. To merge two arglist arrays, use XtMergeArgLists. __ | ArgList XtMergeArgLists(args1, num_args1, args2, num_args2) ArgList args1; Cardinal num_args1; ArgList args2; Cardinal num_args2; args1 Specifies the first argument list. num_args1 Specifies the number of entries in the first argu- ment list. args2 Specifies the second argument list. num_args2 Specifies the number of entries in the second argument list. |__ The XtMergeArgLists function allocates enough storage to hold the combined arglist arrays and copies them into it. Note that it does not check for duplicate entries. The length of the returned list is the sum of the lengths of the specified lists. When it is no longer needed, free the returned storage by using XtFree. All Intrinsics interfaces that require ArgList arguments have analogs conforming to the ANSI C variable argument list (traditionally called ``varargs'') calling convention. The name of the analog is formed by prefixing ``Va'' to the name 55 X Toolkit Intrinsics X11 Release 6.4 of the corresponding ArgList procedure; e.g., XtVaCreateWid- get. Each procedure named XtVasomething takes as its last arguments, in place of the corresponding ArgList/ Cardinal parameters, a variable parameter list of resource name and value pairs where each name is of type String and each value is of type XtArgVal. The end of the list is identified by a name entry containing NULL. Developers writing in the C language wishing to pass resource name and value pairs to any of these interfaces may use the ArgList and varargs forms interchangeably. Two special names are defined for use only in varargs lists: XtVaTypedArg and XtVaNestedList. __ | #define XtVaTypedArg "XtVaTypedArg" |__ If the name XtVaTypedArg is specified in place of a resource name, then the following four arguments are interpreted as a name/type/value/size tuple where name is of type String, type is of type String, value is of type XtArgVal, and size is of type int. When a varargs list containing XtVaTypedArg is processed, a resource type conversion (see Section 9.6) is performed if necessary to convert the value into the for- mat required by the associated resource. If type is XtRString, then value contains a pointer to the string and size contains the number of bytes allocated, including the trailing null byte. If type is not XtRString, then if size is less than or equal to sizeof(XtArgVal), the value should be the data cast to the type XtArgVal, otherwise value is a pointer to the data. If the type conversion fails for any reason, a warning message is issued and the list entry is skipped. __ | #define XtVaNestedList "XtVaNestedList" |__ If the name XtVaNestedList is specified in place of a resource name, then the following argument is interpreted as an XtVarArgsList value, which specifies another varargs list that is logically inserted into the original list at the point of declaration. The end of the nested list is identi- fied with a name entry containing NULL. Varargs lists may nest to any depth. 56 X Toolkit Intrinsics X11 Release 6.4 To dynamically allocate a varargs list for use with XtVaNestedList in multiple calls, use XtVaCreateArgsList. __ | typedef XtPointer XtVarArgsList; XtVarArgsList XtVaCreateArgsList(unused, ...) XtPointer unused; unused This argument is not currently used and must be specified as NULL. ... Specifies a variable parameter list of resource name and value pairs. |__ The XtVaCreateArgsList function allocates memory and copies its arguments into a single list pointer, which may be used with XtVaNestedList. The end of both lists is identified by a name entry containing NULL. Any entries of type XtVaType- dArg are copied as specified without applying conversions. Data passed by reference (including Strings) are not copied, only the pointers themselves; the caller must ensure that the data remain valid for the lifetime of the created varargs list. The list should be freed using XtFree when no longer needed. Use of resource files and of the resource database is gener- ally encouraged over lengthy arglist or varargs lists when- ever possible in order to permit modification without recom- pilation. 2.5.2. Creating a Widget Instance To create an instance of a widget, use XtCreateWidget. 57 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtCreateWidget(name, object_class, parent, args, num_args) String name; WidgetClass object_class; Widget parent; ArgList args; Cardinal num_args; name Specifies the resource instance name for the cre- ated widget, which is used for retrieving resources and, for that reason, should not be the same as any other widget that is a child of the same parent. object_class Specifies the widget class pointer for the created object. Must be objectClass or any subclass thereof. parent Specifies the parent widget. Must be of class Object or any subclass thereof. args Specifies the argument list to override any other resource specifications. num_args Specifies the number of entries in the argument list. |__ The XtCreateWidget function performs all the boilerplate operations of widget creation, doing the following in order: o Checks to see if the class_initialize procedure has been called for this class and for all superclasses and, if not, calls those necessary in a superclass-to- subclass order. o If the specified class is not coreWidgetClass or a sub- class thereof, and the parent's class is a subclass of compositeWidgetClass and either no extension record in the parent's composite class part extension field exists with the record_type NULLQUARK or the accepts_objects field in the extension record is False, XtCreateWidget issues a fatal error; see Section 3.1 and Chapter 12. o If the specified class contains an extension record in the object class part extension field with record_type NULLQUARK and the allocate field is not NULL, the pro- cedure is invoked to allocate memory for the widget instance. If the parent is a member of the class con- straintWidgetClass, the procedure also allocates memory for the parent's constraints and stores the address of 58 X Toolkit Intrinsics X11 Release 6.4 this memory into the constraints field. If no allocate procedure is found, the Intrinsics allocate memory for the widget and, when applicable, the constraints, and initializes the constraints field. o Initializes the Core nonresource data fields self, par- ent, widget_class, being_destroyed, name, managed, win- dow, visible, popup_list, and num_popups. o Initializes the resource fields (for example, back- ground_pixel) by using the CoreClassPart resource lists specified for this class and all superclasses. o If the parent is a member of the class constraintWid- getClass, initializes the resource fields of the con- straints record by using the ConstraintClassPart resource lists specified for the parent's class and all superclasses up to constraintWidgetClass. o Calls the initialize procedures for the widget starting at the Object initialize procedure on down to the wid- get's initialize procedure. o If the parent is a member of the class constraintWid- getClass, calls the ConstraintClassPart initialize pro- cedures, starting at constraintWidgetClass on down to the parent's ConstraintClassPart initialize procedure. o If the parent is a member of the class compositeWidget- Class, puts the widget into its parent's children list by calling its parent's insert_child procedure. For further information, see Section 3.1. To create an instance of a widget using varargs lists, use XtVaCreateWidget. 59 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtVaCreateWidget(name, object_class, parent, ...) String name; WidgetClass object_class; Widget parent; name Specifies the resource name for the created wid- get. object_class Specifies the widget class pointer for the created object. Must be objectClass or any subclass thereof. parent Specifies the parent widget. Must be of class Object or any subclass thereof. ... Specifies the variable argument list to override any other resource specifications. |__ The XtVaCreateWidget procedure is identical in function to XtCreateWidget with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. 2.5.3. Creating an Application Shell Instance An application can have multiple top-level widgets, each of which specifies a unique widget tree that can potentially be on different screens or displays. An application uses XtAp- pCreateShell to create independent widget trees. 60 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtAppCreateShell(name, application_class, widget_class, display, args, num_args) String name; String application_class; WidgetClass widget_class; Display *display; ArgList args; Cardinal num_args; name Specifies the instance name of the shell widget. If name is NULL, the application name passed to XtDisplayInitialize is used. application_class Specifies the resource class string to be used in place of the widget class_name string when widget_class is applicationShellWidgetClass or a subclass thereof. widget_class Specifies the widget class for the top-level widget (e.g., applicationShellWidgetClass). display Specifies the display for the default screen and for the resource database used to retrieve the shell widget resources. args Specifies the argument list to override any other resource specifications. num_args Specifies the number of entries in the argument list. |__ The XtAppCreateShell function creates a new shell widget instance as the root of a widget tree. The screen resource for this widget is determined by first scanning args for the XtNscreen argument. If no XtNscreen argument is found, the resource database associated with the default screen of the specified display is queried for the resource name.screen, class Class.Screen where Class is the specified applica- tion_class if widget_class is applicationShellWidgetClass or a subclass thereof. If widget_class is not application- ShellWidgetClass or a subclass, Class is the class_name field from the CoreClassPart of the specified widget_class. If this query fails, the default screen of the specified display is used. Once the screen is determined, the resource database associated with that screen is used to retrieve all remaining resources for the shell widget not specified in args. The widget name and Class as determined above are used as the leftmost (i.e., root) components in all fully qualified resource names for objects within this widget tree. 61 X Toolkit Intrinsics X11 Release 6.4 If the specified widget class is a subclass of WMShell, the name and Class as determined above will be stored into the WM_CLASS property on the widget's window when it becomes realized. If the specified widget_class is application- ShellWidgetClass or a subclass thereof, the WM_COMMAND prop- erty will also be set from the values of the XtNargv and XtNargc resources. To create multiple top-level shells within a single (logi- cal) application, you can use one of two methods: o Designate one shell as the real top-level shell and create the others as pop-up children of it by using XtCreatePopupShell. o Have all shells as pop-up children of an unrealized top-level shell. The first method, which is best used when there is a clear choice for what is the main window, leads to resource speci- fications like the following: xmail.geometry:... (the main window) xmail.read.geometry:...(the read window) xmail.compose.geometry:...(the compose window) The second method, which is best if there is no main window, leads to resource specifications like the following: xmail.headers.geometry:...(the headers window) xmail.read.geometry:...(the read window) xmail.compose.geometry:...(the compose window) To create a top-level widget that is the root of a widget tree using varargs lists, use XtVaAppCreateShell. 62 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtVaAppCreateShell(name, application_class, widget_class, display, ...) String name; String application_class; WidgetClass widget_class; Display *display; name Specifies the instance name of the shell wid- get. If name is NULL, the application name passed to XtDisplayInitialize is used. application_class Specifies the resource class string to be used in place of the widget class_name string when widget_class is applicationShellWidget- Class or a subclass thereof. widget_class Specifies the widget class for the top-level widget. display Specifies the display for the default screen and for the resource database used to retrieve the shell widget resources. ... Specifies the variable argument list to over- ride any other resource specifications. |__ The XtVaAppCreateShell procedure is identical in function to XtAppCreateShell with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. 2.5.4. Convenience Procedure to Initialize an Application To initialize the Intrinsics internals, create an applica- tion context, open and initialize a display, and create the initial root shell instance, an application may use XtOpe- nApplication or XtVaOpenApplication. 63 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtOpenApplication(app_context_return, application_class, options, num_options, argc_in_out, argv_in_out, fallback_resources, widget_class, args, num_args) XtAppContext *app_context_return; String application_class; XrmOptionDescList options; Cardinal num_options; int *argc_in_out; String *argv_in_out; String *fallback_resources; WidgetClass widget_class; ArgList args; Cardinal num_args; app_context_return Returns the application context, if non-NULL. application_class Specifies the class name of the application. options Specifies the command line options table. num_options Specifies the number of entries in options. argc_in_out Specifies a pointer to the number of command line arguments. argv_in_out Specifies a pointer to the command line argu- ments. fallback_resources Specifies resource values to be used if the application class resource file cannot be opened or read, or NULL. widget_class Specifies the class of the widget to be cre- ated. Must be shellWidgetClass or a sub- class. args Specifies the argument list to override any other resource specifications for the created shell widget. num_args Specifies the number of entries in the argu- ment list. |__ The XtOpenApplication function calls XtToolkitInitialize followed by XtCreateApplicationContext, then calls XtOpenDisplay with display_string NULL and application_name NULL, and finally calls XtAppCreateShell with name NULL, the specified widget_class, an argument list and count, and returns the created shell. The recommended widget_class is 64 X Toolkit Intrinsics X11 Release 6.4 sessionShellWidgetClass. The argument list and count are created by merging the specified args and num_args with a list containing the specified argc and argv. The modified argc and argv returned by XtDisplayInitialize are returned in argc_in_out and argv_in_out. If app_context_return is not NULL, the created application context is also returned. If the display specified by the command line cannot be opened, an error message is issued and XtOpenApplication terminates the application. If fallback_resources is non- NULL, XtAppSetFallbackResources is called with the value prior to calling XtOpenDisplay. 65 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtVaOpenApplication(app_context_return, application_class, options, num_options, argc_in_out, argv_in_out, fallback_resources, widget_class, ...) XtAppContext *app_context_return; String application_class; XrmOptionDescList options; Cardinal num_options; int *argc_in_out; String *argv_in_out; String *fallback_resources; WidgetClass widget_class; app_context_return Returns the application context, if non-NULL. application_class Specifies the class name of the application. options Specifies the command line options table. num_options Specifies the number of entries in options. argc_in_out Specifies a pointer to the number of command line arguments. argv_in_out Specifies the command line arguments array. fallback_resources Specifies resource values to be used if the application class resource file cannot be opened, or NULL. widget_class Specifies the class of the widget to be cre- ated. Must be shellWidgetClass or a sub- class. ... Specifies the variable argument list to over- ride any other resource specifications for the created shell. |__ The XtVaOpenApplication procedure is identical in function to XtOpenApplication with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. 2.5.5. Widget Instance Allocation: The allocate Procedure A widget class may optionally provide an instance allocation procedure in the ObjectClassExtension record. When the call to create a widget includes a varargs list containing XtVaTypedArg, these arguments will be passed to 66 X Toolkit Intrinsics X11 Release 6.4 the allocation procedure in an XtTypedArgList. __ | typedef struct { String name; String type; XtArgVal value; int size; } XtTypedArg, *XtTypedArgList; |__ The allocate procedure pointer in the ObjectClassExtension record is of type XtAllocateProc. 67 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtAllocateProc)(WidgetClass, Cardinal*, Cardinal*, ArgList, Cardinal*, XtTypedArgList, Cardinal*, Widget*, XtPointer*); WidgetClass widget_class; Cardinal* constraint_size; Cardinal* more_bytes; ArgList args; Cardinal* num_args; XtTypedArgList typed_args, Cardinal* num_typed_args; Widget* new_return; XtPointer* more_bytes_return; widget_class Specifies the widget class of the instance to allocate. constraint_size Specifies the size of the constraint record to allocate, or 0. more_bytes Specifies the number of auxiliary bytes of memory to allocate. args Specifies the argument list as given in the call to create the widget. num_args Specifies the number of arguments. typed_args Specifies the list of typed arguments given in the call to create the widget. num_typed_args Specifies the number of typed arguments. new_return Returns a pointer to the newly allocated instance, or NULL in case of error. more_bytes_return Returns the auxiliary memory if it was requested, or NULL if requested and an error occurred; otherwise, unchanged. |__ At widget allocation time, if an extension record with record_type equal to NULLQUARK is located through the object class part extension field and the allocate field is not NULL, the XtAllocateProc will be invoked to allocate memory for the widget. If no ObjectClassPart extension record is declared with record_type equal to NULLQUARK, then XtInheri- tAllocate and XtInheritDeallocate are assumed. If no XtAl- locateProc is found, the Intrinsics will allocate memory for the widget. 68 X Toolkit Intrinsics X11 Release 6.4 An XtAllocateProc must perform the following: o Allocate memory for the widget instance and return it in new_return. The memory must be at least wc->core_class.widget_size bytes in length, double-word aligned. o Initialize the core.constraints field in the instance record to NULL or to point to a constraint record. If constraint_size is not 0, the procedure must allocate memory for the constraint record. The memory must be double-word aligned. o If more_bytes is not 0, then the address of a block of memory at least more_bytes in size, double-word aligned, must be returned in the more_bytes_return parameter, or NULL to indicate an error. A class allocation procedure that envelops the allocation procedure of a superclass must rely on the enveloped proce- dure to perform the instance and constraint allocation. Allocation procedures should refrain from initializing fields in the widget record except to store pointers to newly allocated additional memory. Under no circumstances should an allocation procedure that envelopes its superclass allocation procedure modify fields in the instance part of any superclass. 2.5.6. Widget Instance Initialization: The initialize Pro- cedure The initialize procedure pointer in a widget class is of type XtInitProc. 69 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtInitProc)(Widget, Widget, ArgList, Cardinal*); Widget request; Widget new; ArgList args; Cardinal *num_args; request Specifies a copy of the widget with resource val- ues as requested by the argument list, the resource database, and the widget defaults. new Specifies the widget with the new values, both resource and nonresource, that are actually allowed. args Specifies the argument list passed by the client, for computing derived resource values. If the client created the widget using a varargs form, any resources specified via XtVaTypedArg are con- verted to the widget representation and the list is transformed into the ArgList format. num_args Specifies the number of entries in the argument list. |__ An initialization procedure performs the following: o Allocates space for and copies any resources referenced by address that the client is allowed to free or modify after the widget has been created. For example, if a widget has a field that is a String, it may choose not to depend on the characters at that address remaining constant but dynamically allocate space for the string and copy it to the new space. Widgets that do not copy one or more resources referenced by address should clearly so state in their user documentation. Note It is not necessary to allocate space for or to copy callback lists. o Computes values for unspecified resource fields. For example, if width and height are zero, the widget should compute an appropriate width and height based on its other resources. 70 X Toolkit Intrinsics X11 Release 6.4 Note A widget may directly assign only its own width and height within the initialize, ini- tialize_hook, set_values, and set_values_hook procedures; see Chapter 6. o Computes values for uninitialized nonresource fields that are derived from resource fields. For example, graphics contexts (GCs) that the widget uses are derived from resources like background, foreground, and font. An initialization procedure also can check certain fields for internal consistency. For example, it makes no sense to specify a colormap for a depth that does not support that colormap. Initialization procedures are called in superclass-to-sub- class order after all fields specified in the resource lists have been initialized. The initialize procedure does not need to examine args and num_args if all public resources are declared in the resource list. Most of the initializa- tion code for a specific widget class deals with fields defined in that class and not with fields defined in its superclasses. If a subclass does not need an initialization procedure because it does not need to perform any of the above opera- tions, it can specify NULL for the initialize field in the class record. Sometimes a subclass may want to overwrite values filled in by its superclass. In particular, size calculations of a superclass often are incorrect for a subclass, and in this case, the subclass must modify or recalculate fields declared and computed by its superclass. As an example, a subclass can visually surround its super- class display. In this case, the width and height calcu- lated by the superclass initialize procedure are too small and need to be incremented by the size of the surround. The subclass needs to know if its superclass's size was calcu- lated by the superclass or was specified explicitly. All widgets must place themselves into whatever size is explic- itly given, but they should compute a reasonable size if no size is requested. The request and new arguments provide the necessary informa- tion for a subclass to determine the difference between an explicitly specified field and a field computed by a super- class. The request widget is a copy of the widget as ini- tialized by the arglist and resource database. The new 71 X Toolkit Intrinsics X11 Release 6.4 widget starts with the values in the request, but it has been updated by all superclass initialization procedures called so far. A subclass initialize procedure can compare these two to resolve any potential conflicts. In the above example, the subclass with the visual surround can see if the width and height in the request widget are zero. If so, it adds its surround size to the width and height fields in the new widget. If not, it must make do with the size originally specified. The new widget will become the actual widget instance record. Therefore, the initialization procedure should do all its work on the new widget; the request widget should never be modified. If the initialize procedure needs to call any routines that operate on a widget, it should spec- ify new as the widget instance. 2.5.7. Constraint Instance Initialization: The Constraint- ClassPart initialize Procedure The constraint initialization procedure pointer, found in the ConstraintClassPart initialize field of the widget class record, is of type XtInitProc. The values passed to the parent constraint initialization procedures are the same as those passed to the child's class widget initialization pro- cedures. The constraints field of the request widget points to a copy of the constraints record as initialized by the arglist and resource database. The constraint initialization procedure should compute any constraint fields derived from constraint resources. It can make further changes to the new widget to make the widget and any other constraint fields conform to the specified constraints, for example, changing the widget's size or position. If a constraint class does not need a constraint initializa- tion procedure, it can specify NULL for the initialize field of the ConstraintClassPart in the class record. 2.5.8. Nonwidget Data Initialization: The initialize_hook Procedure 72 X Toolkit Intrinsics X11 Release 6.4 Note The initialize_hook procedure is obsolete, as the same information is now available to the initial- ize procedure. The procedure has been retained for those widgets that used it in previous releases. The initialize_hook procedure pointer is of type XtArgsProc: __ | typedef void (*XtArgsProc)(Widget, ArgList, Cardinal*); Widget w; ArgList args; Cardinal *num_args; w Specifies the widget. args Specifies the argument list passed by the client. If the client created the widget using a varargs form, any resources specified via XtVaTypedArg are converted to the widget representation and the list is transformed into the ArgList format. num_args Specifies the number of entries in the argument list. |__ If this procedure is not NULL, it is called immediately after the corresponding initialize procedure or in its place if the initialize field is NULL. The initialize_hook procedure allows a widget instance to initialize nonresource data using information from the spec- ified argument list as if it were a resource. 2.6. Realizing Widgets To realize a widget instance, use XtRealizeWidget. __ | void XtRealizeWidget(w) Widget w; w Specifies the widget. Must be of class Core or |__ any subclass thereof. 73 X Toolkit Intrinsics X11 Release 6.4 If the widget is already realized, XtRealizeWidget simply returns. Otherwise it performs the following: o Binds all action names in the widget's translation table to procedures (see Section 10.1.2). o Makes a postorder traversal of the widget tree rooted at the specified widget and calls each non-NULL change_managed procedure of all composite widgets that have one or more managed children. o Constructs an XSetWindowAttributes structure filled in with information derived from the Core widget fields and calls the realize procedure for the widget, which adds any widget-specific attributes and creates the X window. o If the widget is not a subclass of compositeWidget- Class, XtRealizeWidget returns; otherwise it continues and performs the following: - Descends recursively to each of the widget's man- aged children and calls the realize procedures. Primitive widgets that instantiate children are responsible for realizing those children them- selves. - Maps all of the managed children windows that have mapped_when_managed True. If a widget is managed but mapped_when_managed is False, the widget is allocated visual space but is not displayed. If the widget is a top-level shell widget (that is, it has no parent), and mapped_when_managed is True, XtRealizeWidget maps the widget window. XtCreateWidget, XtVaCreateWidget, XtRealizeWidget, XtMan- ageChildren, XtUnmanageChildren, XtUnrealizeWidget, XtSetMappedWhenManaged, and XtDestroyWidget maintain the following invariants: o If a composite widget is realized, then all its managed children are realized. o If a composite widget is realized, then all its managed children that have mapped_when_managed True are mapped. All Intrinsics functions and all widget routines should accept either realized or unrealized widgets. When calling the realize or change_managed procedures for children of a composite widget, XtRealizeWidget calls the procedures in reverse order of appearance in the CompositePart children list. By default, this ordering of the realize procedures will result in the stacking order of any newly created 74 X Toolkit Intrinsics X11 Release 6.4 subwindows being top-to-bottom in the order of appearance on the list, and the most recently created child will be at the bottom. To check whether or not a widget has been realized, use XtIsRealized. __ | Boolean XtIsRealized(w) Widget w; w Specifies the widget. Must be of class Object or any subclass thereof. |__ The XtIsRealized function returns True if the widget has been realized, that is, if the widget has a nonzero window ID. If the specified object is not a widget, the state of the nearest widget ancestor is returned. Some widget procedures (for example, set_values) might wish to operate differently after the widget has been realized. 2.6.1. Widget Instance Window Creation: The realize Proce- dure The realize procedure pointer in a widget class is of type XtRealizeProc. __ | typedef void (*XtRealizeProc)(Widget, XtValueMask*, XSetWindowAttributes*); Widget w; XtValueMask *value_mask; XSetWindowAttributes *attributes; w Specifies the widget. value_mask Specifies which fields in the attributes structure are used. attributes Specifies the window attributes to use in the XCreateWindow call. |__ The realize procedure must create the widget's window. 75 X Toolkit Intrinsics X11 Release 6.4 Before calling the class realize procedure, the generic XtRealizeWidget function fills in a mask and a corresponding XSetWindowAttributes structure. It sets the following fields in attributes and corresponding bits in value_mask based on information in the widget core structure: o The background_pixmap (or background_pixel if back- ground_pixmap is XtUnspecifiedPixmap) is filled in from the corresponding field. o The border_pixmap (or border_pixel if border_pixmap is XtUnspecifiedPixmap) is filled in from the correspond- ing field. o The colormap is filled in from the corresponding field. o The event_mask is filled in based on the event handlers registered, the event translations specified, whether the expose field is non-NULL, and whether visi- ble_interest is True. o The bit_gravity is set to NorthWestGravity if the expose field is NULL. These or any other fields in attributes and the correspond- ing bits in value_mask can be set by the realize procedure. Note that because realize is not a chained operation, the widget class realize procedure must update the XSetWindowAt- tributes structure with all the appropriate fields from non- Core superclasses. A widget class can inherit its realize procedure from its superclass during class initialization. The realize proce- dure defined for coreWidgetClass calls XtCreateWindow with the passed value_mask and attributes and with window_class and visual set to CopyFromParent. Both compositeWidgetClass and constraintWidgetClass inherit this realize procedure, and most new widget subclasses can do the same (see Section 1.6.10). The most common noninherited realize procedures set bit_gravity in the mask and attributes to the appropriate value and then create the window. For example, depending on its justification, Label might set bit_gravity to WestGrav- ity, CenterGravity, or EastGravity. Consequently, shrinking it would just move the bits appropriately, and no exposure event is needed for repainting. If a composite widget's children should be realized in an order other than that specified (to control the stacking order, for example), it should call XtRealizeWidget on its children itself in the appropriate order from within its own realize procedure. 76 X Toolkit Intrinsics X11 Release 6.4 Widgets that have children and whose class is not a subclass of compositeWidgetClass are responsible for calling XtReal- izeWidget on their children, usually from within the realize procedure. Realize procedures cannot manage or unmanage their descen- dants. 2.6.2. Window Creation Convenience Routine Rather than call the Xlib XCreateWindow function explicitly, a realize procedure should normally call the Intrinsics ana- log XtCreateWindow, which simplifies the creation of windows for widgets. __ | void XtCreateWindow(w, window_class, visual, value_mask, attributes) Widget w; unsigned int window_class; Visual *visual; XtValueMask value_mask; XSetWindowAttributes *attributes; w Specifies the widget that defines the additional window attributed. Must be of class Core or any subclass thereof. window_class Specifies the Xlib window class (for example, InputOutput, InputOnly, or CopyFromParent). visual Specifies the visual type (usually CopyFromPar- ent). value_mask Specifies which fields in the attributes structure are used. attributes Specifies the window attributes to use in the XCreateWindow call. |__ The XtCreateWindow function calls the Xlib XCreateWindow function with values from the widget structure and the passed parameters. Then, it assigns the created window to the widget's window field. XtCreateWindow evaluates the following fields of the widget core structure: depth, screen, parent->core.window, x, y, width, height, and border_width. 77 X Toolkit Intrinsics X11 Release 6.4 2.7. Obtaining Window Information from a Widget The Core widget class definition contains the screen and window ids. The window field may be NULL for a while (see Sections 2.5 and 2.6). The display pointer, the parent widget, screen pointer, and window of a widget are available to the widget writer by means of macros and to the application writer by means of functions. __ | Display *XtDisplay(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ XtDisplay returns the display pointer for the specified wid- get. __ | Widget XtParent(w) Widget w; w Specifies the widget. Must be of class Object or any subclass thereof. |__ XtParent returns the parent object for the specified widget. The returned object will be of class Object or a subclass. __ | Screen *XtScreen(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ XtScreen returns the screen pointer for the specified wid- get. 78 X Toolkit Intrinsics X11 Release 6.4 __ | Window XtWindow(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ XtWindow returns the window of the specified widget. The display pointer, screen pointer, and window of a widget or of the closest widget ancestor of a nonwidget object are available by means of XtDisplayOfObject, XtScreenOfObject, and XtWindowOfObject. __ | Display *XtDisplayOfObject(object) Widget object; object Specifies the object. Must be of class Object or any subclass thereof. |__ XtDisplayOfObject is identical in function to XtDisplay if the object is a widget; otherwise XtDisplayOfObject returns the display pointer for the nearest ancestor of object that is of class Widget or a subclass thereof. __ | Screen *XtScreenOfObject(object) Widget object; object Specifies the object. Must be of class Object or any subclass thereof. |__ XtScreenOfObject is identical in function to XtScreen if the object is a widget; otherwise XtScreenOfObject returns the screen pointer for the nearest ancestor of object that is of class Widget or a subclass thereof. 79 X Toolkit Intrinsics X11 Release 6.4 __ | Window XtWindowOfObject(object) Widget object; object Specifies the object. Must be of class Object or any subclass thereof. |__ XtWindowOfObject is identical in function to XtWindow if the object is a widget; otherwise XtWindowOfObject returns the window for the nearest ancestor of object that is of class Widget or a subclass thereof. To retrieve the instance name of an object, use XtName. __ | String XtName(object) Widget object; object Specifies the object whose name is desired. Must be of class Object or any subclass thereof. |__ XtName returns a pointer to the instance name of the speci- fied object. The storage is owned by the Intrinsics and must not be modified. The name is not qualified by the names of any of the object's ancestors. Several window attributes are locally cached in the widget instance. Thus, they can be set by the resource manager and XtSetValues as well as used by routines that derive struc- tures from these values (for example, depth for deriving pixmaps, background_pixel for deriving GCs, and so on) or in the XtCreateWindow call. The x, y, width, height, and border_width window attributes are available to geometry managers. These fields are main- tained synchronously inside the Intrinsics. When an XCon- figureWindow is issued by the Intrinsics on the widget's window (on request of its parent), these values are updated immediately rather than some time later when the server gen- erates a ConfigureNotify event. (In fact, most widgets do not select SubstructureNotify events.) This ensures that all geometry calculations are based on the internally con- sistent toolkit world rather than on either an inconsistent world updated by asynchronous ConfigureNotify events or a consistent, but slow, world in which geometry managers ask the server for window sizes whenever they need to lay out their managed children (see Chapter 6). 80 X Toolkit Intrinsics X11 Release 6.4 2.7.1. Unrealizing Widgets To destroy the windows associated with a widget and its non- pop-up descendants, use XtUnrealizeWidget. __ | void XtUnrealizeWidget(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ If the widget is currently unrealized, XtUnrealizeWidget simply returns. Otherwise it performs the following: o Unmanages the widget if the widget is managed. o Makes a postorder (child-to-parent) traversal of the widget tree rooted at the specified widget and, for each widget that has declared a callback list resource named ``unrealizeCallback'', executes the procedures on the XtNunrealizeCallback list. o Destroys the widget's window and any subwindows by calling XDestroyWindow with the specified widget's win- dow field. Any events in the queue or which arrive following a call to XtUnrealizeWidget will be dispatched as if the window(s) of the unrealized widget(s) had never existed. 2.8. Destroying Widgets The Intrinsics provide support o To destroy all the pop-up children of the widget being destroyed and destroy all children of composite wid- gets. o To remove (and unmap) the widget from its parent. o To call the callback procedures that have been regis- tered to trigger when the widget is destroyed. o To minimize the number of things a widget has to deal- locate when destroyed. o To minimize the number of XDestroyWindow calls when destroying a widget tree. 81 X Toolkit Intrinsics X11 Release 6.4 To destroy a widget instance, use XtDestroyWidget. __ | void XtDestroyWidget(w) Widget w; w Specifies the widget. Must be of class Object or any subclass thereof. |__ The XtDestroyWidget function provides the only method of destroying a widget, including widgets that need to destroy themselves. It can be called at any time, including from an application callback routine of the widget being destroyed. This requires a two-phase destroy process in order to avoid dangling references to destroyed widgets. In phase 1, XtDestroyWidget performs the following: o If the being_destroyed field of the widget is True, it returns immediately. o Recursively descends the widget tree and sets the being_destroyed field to True for the widget and all normal and pop-up children. o Adds the widget to a list of widgets (the destroy list) that should be destroyed when it is safe to do so. Entries on the destroy list satisfy the invariant that if w2 occurs after w1 on the destroy list, then w2 is not a descendent, either normal or pop-up, of w1. Phase 2 occurs when all procedures that should execute as a result of the current event have been called, including all procedures registered with the event and translation man- agers, that is, when the current invocation of XtDis- patchEvent is about to return, or immediately if not in XtDispatchEvent. In phase 2, XtDestroyWidget performs the following on each entry in the destroy list in the order specified: o If the widget is not a pop-up child and the widget's parent is a subclass of compositeWidgetClass, and if the parent is not being destroyed, it calls XtUnman- ageChild on the widget and then calls the widget's par- ent's delete_child procedure (see Section 3.3). o Calls the destroy callback procedures registered on the widget and all normal and pop-up descendants in pos- torder (it calls child callbacks before parent 82 X Toolkit Intrinsics X11 Release 6.4 callbacks). The XtDestroyWidget function then makes second traversal of the widget and all normal and pop-up descendants to perform the following three items on each widget in postorder: o If the widget is not a pop-up child and the widget's parent is a subclass of constraintWidgetClass, it calls the ConstraintClassPart destroy procedure for the par- ent, then for the parent's superclass, until finally it calls the ConstraintClassPart destroy procedure for constraintWidgetClass. o Calls the CoreClassPart destroy procedure declared in the widget class, then the destroy procedure declared in its superclass, until finally it calls the destroy procedure declared in the Object class record. Call- back lists are deallocated. o If the widget class object class part contains an ObjectClassExtension record with the record_type NUL- LQUARK and the deallocate field is not NULL, calls the deallocate procedure to deallocate the instance and if one exists, the constraint record. Otherwise, the Intrinsics will deallocate the widget instance record and if one exists, the constraint record. o Calls XDestroyWindow if the specified widget is real- ized (that is, has an X window). The server recur- sively destroys all normal descendant windows. (Win- dows of realized pop-up Shell children, and their descendants, are destroyed by a shell class destroy procedure.) 2.8.1. Adding and Removing Destroy Callbacks When an application needs to perform additional processing during the destruction of a widget, it should register a destroy callback procedure for the widget. The destroy callback procedures use the mechanism described in Chapter 8. The destroy callback list is identified by the resource name XtNdestroyCallback. For example, the following adds an application-supplied destroy callback procedure ClientDestroy with client data to a widget by calling XtAddCallback. XtAddCallback(w, XtNdestroyCallback, ClientDestroy, client_data) Similarly, the following removes the application-supplied destroy callback procedure ClientDestroy by calling XtRemoveCallback. 83 X Toolkit Intrinsics X11 Release 6.4 XtRemoveCallback(w, XtNdestroyCallback, ClientDestroy, client_data) The ClientDestroy argument is of type XtCallbackProc; see Section 8.1. 2.8.2. Dynamic Data Deallocation: The destroy Procedure The destroy procedure pointers in the ObjectClassPart, Rec- tObjClassPart, and CoreClassPart structures are of type XtWidgetProc. __ | typedef void (*XtWidgetProc)(Widget); Widget w; w Specifies the widget being destroyed. |__ The destroy procedures are called in subclass-to-superclass order. Therefore, a widget's destroy procedure should deal- locate only storage that is specific to the subclass and should ignore the storage allocated by any of its super- classes. The destroy procedure should deallocate only resources that have been explicitly created by the subclass. Any resource that was obtained from the resource database or passed in an argument list was not created by the widget and therefore should not be destroyed by it. If a widget does not need to deallocate any storage, the destroy procedure entry in its class record can be NULL. Deallocating storage includes, but is not limited to, the following steps: o Calling XtFree on dynamic storage allocated with XtMal- loc, XtCalloc, and so on. o Calling XFreePixmap on pixmaps created with direct X calls. o Calling XtReleaseGC on GCs allocated with XtGetGC. o Calling XFreeGC on GCs allocated with direct X calls. o Calling XtRemoveEventHandler on event handlers added to other widgets. o Calling XtRemoveTimeOut on timers created with XtAppAd- dTimeOut. 84 X Toolkit Intrinsics X11 Release 6.4 o Calling XtDestroyWidget for each child if the widget has children and is not a subclass of compositeWidget- Class. During destroy phase 2 for each widget, the Intrinsics remove the widget from the modal cascade, unregister all event handlers, remove all key, keyboard, button, and pointer grabs and remove all callback procedures registered on the widget. Any outstanding selection transfers will time out. 2.8.3. Dynamic Constraint Data Deallocation: The Con- straintClassPart destroy Procedure The constraint destroy procedure identified in the Con- straintClassPart structure is called for a widget whose par- ent is a subclass of constraintWidgetClass. This constraint destroy procedure pointer is of type XtWidgetProc. The con- straint destroy procedures are called in subclass-to-super- class order, starting at the class of the widget's parent and ending at constraintWidgetClass. Therefore, a parent's constraint destroy procedure should deallocate only storage that is specific to the constraint subclass and not storage allocated by any of its superclasses. If a parent does not need to deallocate any constraint stor- age, the constraint destroy procedure entry in its class record can be NULL. 2.8.4. Widget Instance Deallocation: The deallocate Proce- dure The deallocate procedure pointer in the ObjectClassExtension record is of type XtDeallocateProc. __ | typedef void (*XtDeallocateProc)(Widget, XtPointer); Widget widget; XtPointer more_bytes; widget Specifies the widget being destroyed. more_bytes Specifies the auxiliary memory received from the corresponding allocator along with the widget, or NULL. |__ When a widget is destroyed, if an ObjectClassExtension record exists in the object class part extension field with 85 X Toolkit Intrinsics X11 Release 6.4 record_type NULLQUARK and the deallocate field is not NULL, the XtDeallocateProc will be called. If no ObjectClassPart extension record is declared with record_type equal to NUL- LQUARK, then XtInheritAllocate and XtInheritDeallocate are assumed. The responsibilities of the deallocate procedure are to deallocate the memory specified by more_bytes if it is not NULL, to deallocate the constraints record as speci- fied by the widget's core.constraints field if it is not NULL, and to deallocate the widget instance itself. If no XtDeallocateProc is found, it is assumed that the Intrinsics originally allocated the memory and is responsi- ble for freeing it. 2.9. Exiting from an Application All X Toolkit applications should terminate by calling XtDe- stroyApplicationContext and then exiting using the standard method for their operating system (typically, by calling exit for POSIX-based systems). The quickest way to make the windows disappear while exiting is to call XtUnmapWidget on each top-level shell widget. The Intrinsics have no resources beyond those in the program image, and the X server will free its resources when its connection to the application is broken. Depending upon the widget set in use, it may be necessary to explicitly destroy individual widgets or widget trees with XtDestroyWidget before calling XtDestroyApplicationContext in order to ensure that any required widget cleanup is prop- erly executed. The application developer must refer to the widget documentation to learn if a widget needs to perform cleanup beyond that performed automatically by the operating system. If the client is a session participant (see Section 4.2), then the client may wish to resign from the session before exiting. See Section 4.2.4 for details. 86 X Toolkit Intrinsics X11 Release 6.4 Chapter 3 Composite Widgets and Their Children Composite widgets (widgets whose class is a subclass of com- positeWidgetClass) can have an arbitrary number of children. Consequently, they are responsible for much more than primi- tive widgets. Their responsibilities (either implemented directly by the widget class or indirectly by Intrinsics functions) include: o Overall management of children from creation to destruction. o Destruction of descendants when the composite widget is destroyed. o Physical arrangement (geometry management) of a dis- playable subset of children (that is, the managed chil- dren). o Mapping and unmapping of a subset of the managed chil- dren. Overall management is handled by the generic procedures XtCreateWidget and XtDestroyWidget. XtCreateWidget adds children to their parent by calling the parent's insert_child procedure. XtDestroyWidget removes children from their parent by calling the parent's delete_child pro- cedure and ensures that all children of a destroyed compos- ite widget also get destroyed. Only a subset of the total number of children is actually managed by the geometry manager and hence possibly visible. For example, a composite editor widget supporting multiple editing buffers might allocate one child widget for each file buffer, but it might display only a small number of the existing buffers. Widgets that are in this displayable sub- set are called managed widgets and enter into geometry man- ager calculations. The other children are called unmanaged widgets and, by definition, are not mapped by the Intrin- sics. Children are added to and removed from their parent's man- aged set by using XtManageChild, XtManageChildren, XtUnman- ageChild, XtUnmanageChildren, and XtChangeManagedSet, which notify the parent to recalculate the physical layout of its children by calling the parent's change_managed procedure. The XtCreateManagedWidget convenience function calls XtCre- ateWidget and XtManageChild on the result. 87 X Toolkit Intrinsics X11 Release 6.4 Most managed children are mapped, but some widgets can be in a state where they take up physical space but do not show anything. Managed widgets are not mapped automatically if their map_when_managed field is False. The default is True and is changed by using XtSetMappedWhenManaged. Each composite widget class declares a geometry manager, which is responsible for figuring out where the managed children should appear within the composite widget's window. Geometry management techniques fall into four classes: Fixed boxes Fixed boxes have a fixed number of children created by the parent. All these children are managed, and none ever makes geometry manager requests. Homogeneous boxes Homogeneous boxes treat all children equally and apply the same geometry constraints to each child. Many clients insert and delete widgets freely. Heterogeneous boxes Heterogeneous boxes have a specific location where each child is placed. This location usually is not specified in pixels, because the window may be resized, but is expressed rather in terms of the relationship between a child and the parent or between the child and other specific children. The class of heterogeneous boxes is usually a subclass of Constraint. Shell boxes Shell boxes typically have only one child, and the child's size is usually exactly the size of the shell. The geometry manager must communicate with the window manager, if it exists, and the box must also accept Con- figureNotify events when the window size is changed by the window manager. 3.1. Addition of Children to a Composite Widget: The insert_child Procedure To add a child to the parent's list of children, the XtCre- ateWidget function calls the parent's class routine insert_child. The insert_child procedure pointer in a com- posite widget is of type XtWidgetProc. 88 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtWidgetProc)(Widget); Widget w; w Passes the newly created child. |__ Most composite widgets inherit their superclass's operation. The insert_child routine in CompositeWidgetClasscalls and inserts the child at the specified position in the children list, expanding it if necessary. Some composite widgets define their own insert_child routine so that they can order their children in some convenient way, create companion controller widgets for a new widget, or limit the number or class of their child widgets. A com- posite widget class that wishes to allow nonwidget children (see Chapter 12) must specify a CompositeClassExtension extension record as described in Section 1.4.2.1 and set the accepts_objects field in this record to True. If the Com- positeClassExtension record is not specified or the accepts_objects field is False, the composite widget can assume that all its children are of a subclass of Core with- out an explicit subclass test in the insert_child procedure. If there is not enough room to insert a new child in the children array (that is, num_children is equal to num_slots), the insert_child procedure must first reallocate the array and update num_slots. The insert_child procedure then places the child at the appropriate position in the array and increments the num_children field. 3.2. Insertion Order of Children: The insert_position Pro- cedure Instances of composite widgets sometimes need to specify more about the order in which their children are kept. For example, an application may want a set of command buttons in some logical order grouped by function, and it may want but- tons that represent file names to be kept in alphabetical order without constraining the order in which the buttons are created. An application controls the presentation order of a set of children by supplying an XtNinsertPosition resource. The insert_position procedure pointer in a composite widget instance is of type XtOrderProc. 89 X Toolkit Intrinsics X11 Release 6.4 __ | typedef Cardinal (*XtOrderProc)(Widget); Widget w; w Passes the newly created widget. |__ Composite widgets that allow clients to order their children (usually homogeneous boxes) can call their widget instance's insert_position procedure from the class's insert_child pro- cedure to determine where a new child should go in its chil- dren array. Thus, a client using a composite class can apply different sorting criteria to widget instances of the class, passing in a different insert_position procedure resource when it creates each composite widget instance. The return value of the insert_position procedure indicates how many children should go before the widget. Returning zero indicates that the widget should go before all other children, and returning num_children indicates that it should go after all other children. The default insert_position function returns num_children and can be overridden by a specific composite widget's resource list or by the argument list provided when the composite widget is created. 3.3. Deletion of Children: The delete_child Procedure To remove the child from the parent's children list, the XtDestroyWidget function eventually causes a call to the Composite parent's class delete_child procedure. The delete_child procedure pointer is of type XtWidgetProc. __ | typedef void (*XtWidgetProc)(Widget); Widget w; w Passes the child being deleted. |__ Most widgets inherit the delete_child procedure from their superclass. Composite widgets that create companion widgets define their own delete_child procedure to remove these com- panion widgets. 90 X Toolkit Intrinsics X11 Release 6.4 3.4. Adding and Removing Children from the Managed Set The Intrinsics provide a set of generic routines to permit the addition of widgets to or the removal of widgets from a composite widget's managed set. These generic routines eventually call the composite widget's change_managed proce- dure if the procedure pointer is non-NULL. The change_man- aged procedure pointer is of type XtWidgetProc. The widget argument specifies the composite widget whose managed child set has been modified. 3.4.1. Managing Children To add a list of widgets to the geometry-managed (and hence displayable) subset of their Composite parent, use XtMan- ageChildren. __ | typedef Widget *WidgetList; void XtManageChildren(children, num_children) WidgetList children; Cardinal num_children; children Specifies a list of child widgets. Each child must be of class RectObj or any subclass thereof. num_children Specifies the number of children in the list. |__ The XtManageChildren function performs the following: o Issues an error if the children do not all have the same parent or if the parent's class is not a subclass of compositeWidgetClass. o Returns immediately if the common parent is being destroyed; otherwise, for each unique child on the list, XtManageChildren ignores the child if it already is managed or is being destroyed, and marks it if not. o If the parent is realized and after all children have been marked, it makes some of the newly managed chil- dren viewable: - Calls the change_managed routine of the widgets' parent. - Calls XtRealizeWidget on each previously unmanaged child that is unrealized. 91 X Toolkit Intrinsics X11 Release 6.4 - Maps each previously unmanaged child that has map_when_managed True. Managing children is independent of the ordering of children and independent of creating and deleting children. The lay- out routine of the parent should consider children whose managed field is True and should ignore all other children. Note that some composite widgets, especially fixed boxes, call XtManageChild from their insert_child procedure. If the parent widget is realized, its change_managed proce- dure is called to notify it that its set of managed children has changed. The parent can reposition and resize any of its children. It moves each child as needed by calling XtMoveWidget, which first updates the x and y fields and which then calls XMoveWindow. If the composite widget wishes to change the size or border width of any of its children, it calls XtResizeWidget, which first updates the width, height, and border_width fields and then calls XConfigureWindow. Simultaneous repositioning and resizing may be done with XtConfigureWidget; see Section 6.6. To add a single child to its parent widget's set of managed children, use XtManageChild. __ | void XtManageChild(child) Widget child; child Specifies the child. Must be of class RectObj or any subclass thereof. |__ The XtManageChild function constructs a WidgetList of length 1 and calls XtManageChildren. To create and manage a child widget in a single procedure, use XtCreateManagedWidget or XtVaCreateManagedWidget. 92 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtCreateManagedWidget(name, widget_class, parent, args, num_args) String name; WidgetClass widget_class; Widget parent; ArgList args; Cardinal num_args; name Specifies the resource instance name for the cre- ated widget. widget_class Specifies the widget class pointer for the created widget. Must be rectObjClass or any subclass thereof. parent Specifies the parent widget. Must be of class Composite or any subclass thereof. args Specifies the argument list to override any other resource specifications. num_args Specifies the number of entries in the argument list. |__ The XtCreateManagedWidget function is a convenience routine that calls XtCreateWidget and XtManageChild. 93 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtVaCreateManagedWidget(name, widget_class, parent, ...) String name; WidgetClass widget_class; Widget parent; name Specifies the resource instance name for the cre- ated widget. widget_class Specifies the widget class pointer for the created widget. Must be rectObjClass or any subclass thereof. parent Specifies the parent widget. Must be of class Composite or any subclass thereof. ... Specifies the variable argument list to override any other resource specifications. |__ XtVaCreateManagedWidget is identical in function to XtCre- ateManagedWidget with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. 3.4.2. Unmanaging Children To remove a list of children from a parent widget's managed list, use XtUnmanageChildren. __ | void XtUnmanageChildren(children, num_children) WidgetList children; Cardinal num_children; children Specifies a list of child widgets. Each child must be of class RectObj or any subclass thereof. num_children Specifies the number of children. |__ The XtUnmanageChildren function performs the following: o Returns immediately if the common parent is being destroyed. o Issues an error if the children do not all have the same parent or if the parent is not a subclass of com- positeWidgetClass. 94 X Toolkit Intrinsics X11 Release 6.4 o For each unique child on the list, XtUnmanageChildren ignores the child if it is unmanaged; otherwise it per- forms the following: - Marks the child as unmanaged. - If the child is realized and the map_when_managed field is True, it is unmapped. o If the parent is realized and if any children have become unmanaged, calls the change_managed routine of the widgets' parent. XtUnmanageChildren does not destroy the child widgets. Removing widgets from a parent's managed set is often a tem- porary banishment, and some time later the client may manage the children again. To destroy widgets entirely, XtDestroy- Widget should be called instead; see Section 2.9. To remove a single child from its parent widget's managed set, use XtUnmanageChild. __ | void XtUnmanageChild(child) Widget child; child Specifies the child. Must be of class RectObj or any subclass thereof. |__ The XtUnmanageChild function constructs a widget list of length 1 and calls XtUnmanageChildren. These functions are low-level routines that are used by generic composite widget building routines. In addition, composite widgets can provide widget-specific, high-level convenience procedures. 3.4.3. Bundling Changes to the Managed Set A client may simultaneously unmanage and manage children with a single call to the Intrinsics. In this same call the client may provide a callback procedure that can modify the geometries of one or more children. The composite widget class defines whether this single client call results in separate invocations of the change_managed method, one to unmanage and the other to manage, or in just a single invo- cation. 95 X Toolkit Intrinsics X11 Release 6.4 To simultaneously remove from and add to the geometry-man- aged set of children of a composite parent, use XtChangeMan- agedSet. __ | void XtChangeManagedSet(unmanage_children, num_unmanage_children, do_change_proc, client_data, manage_children, num_manage_children) WidgetList unmanage_children; Cardinal num_unmanage_children; XtDoChangeProc do_change_proc; XtPointer client_data; WidgetList manage_children; Cardinal num_manage_children; unmanage_children Specifies the list of widget children to initially remove from the managed set. num_unmanage_children Specifies the number of entries in the unmanage_children list. do_change_proc Specifies a procedure to invoke between unmanaging and managing the children, or NULL. client_data Specifies client data to be passed to the do_change_proc. manage_children Specifies the list of widget children to finally add to the managed set. num_manage_children Specifies the number of entries in the manage_children list. |__ The XtChangeManagedSet function performs the following: o Returns immediately if num_unmanage_children and num_manage_children are both 0. o Issues a warning and returns if the widgets specified in the manage_children and the unmanage_children lists do not all have the same parent or if that parent is not a subclass of compositeWidgetClass. o Returns immediately if the common parent is being destroyed. o If do_change_proc is not NULL and the parent's Compos- iteClassExtension allows_change_managed_set field is 96 X Toolkit Intrinsics X11 Release 6.4 False, then XtChangeManagedSet performs the following: - Calls XtUnmanageChildren (unmanage_children, num_unmanage_children). - Calls the do_change_proc. - Calls XtManageChildren (manage_children, num_man- age_children). o Otherwise, the following is performed: - For each child on the unmanage_children list; if the child is already unmanaged it is ignored, oth- erwise it is marked as unmanaged, and if it is realized and its map_when_managed field is True, it is unmapped. - If do_change_proc is non-NULL, the procedure is invoked. - For each child on the manage_children list; if the child is already managed or is being destroyed, it is ignored; otherwise it is marked as managed. - If the parent is realized and after all children have been marked, the change_managed method of the parent is invoked, and subsequently some of the newly managed children are made viewable by call- ing XtRealizeWidget on each previously unmanaged child that is unrealized and mapping each previ- ously unmanaged child that has map_when_managed True. If no CompositeClassExtension record is found in the par- ent's composite class part extension field with record type NULLQUARK and version greater than 1, and if XtInher- itChangeManaged was specified in the parent's class record during class initialization, the value of the allows_change_managed_set field is inherited from the super- class. The value inherited from compositeWidgetClass for the allows_change_managed_set field is False. It is not an error to include a child in both the unman- age_children and the manage_children lists. The effect of such a call is that the child remains managed following the call, but the do_change_proc is able to affect the child while it is in an unmanaged state. The do_change_proc is of type XtDoChangeProc. 97 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtDoChangeProc)(Widget, WidgetList, Cardinal*, WidgetList, Cardinal*, XtPointer); Widget composite_parent; WidgetList unmange_children; Cardinal *num_unmanage_children; WidgetList manage_children; Cardinal *num_manage_children; XtPointer client_data; composite_parent Passes the composite parent whose managed set is being altered. unmanage_children Passes the list of children just removed from the managed set. num_unmanage_children Passes the number of entries in the unman- age_children list. manage_children Passes the list of children about to be added to the managed set. num_manage_children Passes the number of entries in the man- age_children list. client_data Passes the client data passed to XtChange- ManagedSet. |__ The do_change_proc procedure is used by the caller of XtChangeManagedSet to make changes to one or more children at the point when the managed set contains the fewest entries. These changes may involve geometry requests, and in this case the caller of XtChangeManagedSet may take advantage of the fact that the Intrinsics internally grant geometry requests made by unmanaged children without invok- ing the parent's geometry manager. To achieve this advan- tage, if the do_change_proc procedure changes the geometry of a child or of a descendant of a child, then that child should be included in the unmanage_children and manage_chil- dren lists. 3.4.4. Determining if a Widget Is Managed To determine the managed state of a given child widget, use XtIsManaged. 98 X Toolkit Intrinsics X11 Release 6.4 __ | Boolean XtIsManaged(w) Widget w; w Specifies the widget. Must be of class Object or any subclass thereof. |__ The XtIsManaged function returns True if the specified wid- get is of class RectObj or any subclass thereof and is man- aged, or False otherwise. 3.5. Controlling When Widgets Get Mapped A widget is normally mapped if it is managed. However, this behavior can be overridden by setting the XtNmappedWhenMan- aged resource for the widget when it is created or by set- ting the map_when_managed field to False. To change the value of a given widget's map_when_managed field, use XtSetMappedWhenManaged. __ | void XtSetMappedWhenManaged(w, map_when_managed) Widget w; Boolean map_when_managed; w Specifies the widget. Must be of class Core or any subclass thereof. map_when_managed Specifies a Boolean value that indicates the new value that is stored into the widget's map_when_managed field. |__ If the widget is realized and managed, and if map_when_man- aged is True, XtSetMappedWhenManaged maps the window. If the widget is realized and managed, and if map_when_managed is False, it unmaps the window. XtSetMappedWhenManaged is a convenience function that is equivalent to (but slightly faster than) calling XtSetValues and setting the new value for the XtNmappedWhenManaged resource then mapping the wid- get as appropriate. As an alternative to using XtSetMapped- WhenManaged to control mapping, a client may set mapped_when_managed to False and use XtMapWidget and XtUn- mapWidget explicitly. 99 X Toolkit Intrinsics X11 Release 6.4 To map a widget explicitly, use XtMapWidget. __ | XtMapWidget(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ To unmap a widget explicitly, use XtUnmapWidget. __ | XtUnmapWidget(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ 3.6. Constrained Composite Widgets The Constraint widget class is a subclass of compositeWid- getClass. The name is derived from the fact that constraint widgets may manage the geometry of their children based on constraints associated with each child. These constraints can be as simple as the maximum width and height the parent will allow the child to occupy or can be as complicated as how other children should change if this child is moved or resized. Constraint widgets let a parent define constraints as resources that are supplied for their children. For example, if the Constraint parent defines the maximum sizes for its children, these new size resources are retrieved for each child as if they were resources that were defined by the child widget's class. Accordingly, constraint resources may be included in the argument list or resource file just like any other resource for the child. Constraint widgets have all the responsibilities of normal composite widgets and, in addition, must process and act upon the constraint information associated with each of their children. To make it easy for widgets and the Intrinsics to keep track of the constraints associated with a child, every widget has a constraints field, which is the address of a parent-spe- cific structure that contains constraint information about the child. If a child's parent does not belong to a 100 X Toolkit Intrinsics X11 Release 6.4 subclass of constraintWidgetClass, then the child's con- straints field is NULL. Subclasses of Constraint can add constraint data to the con- straint record defined by their superclass. To allow this, widget writers should define the constraint records in their private .h file by using the same conventions as used for widget records. For example, a widget class that needs to maintain a maximum width and height for each child might define its constraint record as follows: typedef struct { Dimension max_width, max_height; } MaxConstraintPart; typedef struct { MaxConstraintPart max; } MaxConstraintRecord, *MaxConstraint; A subclass of this widget class that also needs to maintain a minimum size would define its constraint record as fol- lows: typedef struct { Dimension min_width, min_height; } MinConstraintPart; typedef struct { MaxConstraintPart max; MinConstraintPart min; } MaxMinConstraintRecord, *MaxMinConstraint; Constraints are allocated, initialized, deallocated, and otherwise maintained insofar as possible by the Intrinsics. The Constraint class record part has several entries that facilitate this. All entries in ConstraintClassPart are fields and procedures that are defined and implemented by the parent, but they are called whenever actions are per- formed on the parent's children. The XtCreateWidget function uses the constraint_size field in the parent's class record to allocate a constraint record when a child is created. XtCreateWidget also uses the con- straint resources to fill in resource fields in the con- straint record associated with a child. It then calls the constraint initialize procedure so that the parent can com- pute constraint fields that are derived from constraint resources and can possibly move or resize the child to con- form to the given constraints. 101 X Toolkit Intrinsics X11 Release 6.4 When the XtGetValues and XtSetValues functions are executed on a child, they use the constraint resources to get the values or set the values of constraints associated with that child. XtSetValues then calls the constraint set_values procedures so that the parent can recompute derived con- straint fields and move or resize the child as appropriate. If a Constraint widget class or any of its superclasses have declared a ConstraintClassExtension record in the Con- straintClassPart extension fields with a record type of NUL- LQUARK and the get_values_hook field in the extension record is non-NULL, XtGetValues calls the get_values_hook proce- dure(s) to allow the parent to return derived constraint fields. The XtDestroyWidget function calls the constraint destroy procedure to deallocate any dynamic storage associated with a constraint record. The constraint record itself must not be deallocated by the constraint destroy procedure; XtDe- stroyWidget does this automatically. 102 X Toolkit Intrinsics X11 Release 6.4 Chapter 4 Shell Widgets Shell widgets hold an application's top-level widgets to allow them to communicate with the window manager and ses- sion manager. Shells have been designed to be as nearly invisible as possible. Clients have to create them, but they should never have to worry about their sizes. If a shell widget is resized from the outside (typically by a window manager), the shell widget also resizes its managed child widget automatically. Similarly, if the shell's child widget needs to change size, it can make a geometry request to the shell, and the shell negotiates the size change with the outer environment. Clients should never attempt to change the size of their shells directly. The five types of public shells are: OverrideShell Used for shell windows that completely bypass the window manager (for example, pop-up menu shells). TransientShell Used for shell windows that have the WM_TRANSIENT_FOR property set. The effect of this property is dependent upon the window manager being used. TopLevelShell Used for normal top-level windows (for example, any additional top-level widgets an application needs). Application- Formerly used for the single main top- Shell level window that the window manager iden- tifies as an application instance and made obsolete by SessionShell. SessionShell Used for the single main top-level window that the window manager identifies as an application instance and that interacts with the session manager. 4.1. Shell Widget Definitions Widgets negotiate their size and position with their parent widget, that is, the widget that directly contains them. 103 X Toolkit Intrinsics X11 Release 6.4 Widgets at the top of the hierarchy do not have parent wid- gets. Instead, they must deal with the outside world. To provide for this, each top-level widget is encapsulated in a special widget, called a shell widget. Shell widgets, whose class is a subclass of the Composite class, encapsulate other widgets and can allow a widget to avoid the geometry clipping imposed by the parent-child win- dow relationship. They also can provide a layer of communi- cation with the window manager. The eight different types of shells are: Shell The base class for shell widgets; provides the fields needed for all types of shells. Shell is a direct subclass of compositeWid- getClass. OverrideShell A subclass of Shell; used for shell windows that completely bypass the window manager. WMShell A subclass of Shell; contains fields needed by the common window manager protocol. VendorShell A subclass of WMShell; contains fields used by vendor-specific window managers. TransientShell A subclass of VendorShell; used for shell windows that desire the WM_TRANSIENT_FOR property. TopLevelShell A subclass of VendorShell; used for normal top-level windows. Application- A subclass of TopLevelShell; may be used for Shell an application's additional root windows. SessionShell A subclass of ApplicationShell; used for an application's main root window. Note that the classes Shell, WMShell, and VendorShell are internal and should not be instantiated or subclassed. Only OverrrideShell, TransientShell, TopLevelShell, Application- Shell, and SessionShell are intended for public use. 4.1.1. ShellClassPart Definitions Only the Shell class has additional class fields, which are all contained in the ShellClassExtensionRec. None of the other Shell classes have any additional class fields: 104 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { XtPointer extension; } ShellClassPart, OverrideShellClassPart, WMShellClassPart, VendorShellClassPart, TransientShellClassPart, TopLevelShellClassPart, ApplicationShellClassPart, SessionShellClassPart; |__ The full Shell class record definitions are: 105 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _ShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; } ShellClassRec; typedef struct { XtPointer next_extension; See Section 1.6.12 XrmQuark record_type; See Section 1.6.12 long version; See Section 1.6.12 Cardinal record_size; See Section 1.6.12 XtGeometryHandler root_geometry_manager;See below } ShellClassExtensionRec, *ShellClassExtension; typedef struct _OverrideShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; OverrideShellClassPart override_shell_class; } OverrideShellClassRec; typedef struct _WMShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; WMShellClassPart wm_shell_class; } WMShellClassRec; typedef struct _VendorShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; WMShellClassPart wm_shell_class; VendorShellClassPart vendor_shell_class; } VendorShellClassRec; typedef struct _TransientShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; WMShellClassPart wm_shell_class; VendorShellClassPart vendor_shell_class; TransientShellClassPart transient_shell_class; } TransientShellClassRec; 106 X Toolkit Intrinsics X11 Release 6.4 typedef struct _TopLevelShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; WMShellClassPart wm_shell_class; VendorShellClassPart vendor_shell_class; TopLevelShellClassPart top_level_shell_class; } TopLevelShellClassRec; typedef struct _ApplicationShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; WMShellClassPart wm_shell_class; VendorShellClassPart vendor_shell_class; TopLevelShellClassPart top_level_shell_class; ApplicationShellClassPart application_shell_class; } ApplicationShellClassRec; typedef struct _SessionShellClassRec { CoreClassPart core_class; CompositeClassPart composite_class; ShellClassPart shell_class; WMShellClassPart wm_shell_class; VendorShellClassPart vendor_shell_class; TopLevelShellClassPart top_level_shell_class; ApplicationShellClassPart application_shell_class; SessionShellClassPart session_shell_class; } SessionShellClassRec; |__ 107 X Toolkit Intrinsics X11 Release 6.4 The single occurrences of the class records and pointers for creating instances of shells are: __ | extern ShellClassRec shellClassRec; extern OverrideShellClassRec overrideShellClassRec; extern WMShellClassRec wmShellClassRec; extern VendorShellClassRec vendorShellClassRec; extern TransientShellClassRec transientShellClassRec; extern TopLevelShellClassRec topLevelShellClassRec; extern ApplicationShellClassRec applicationShellClassRec; extern SessionShellClassRec sessionShellClassRec; extern WidgetClass shellWidgetClass; extern WidgetClass overrideShellWidgetClass; extern WidgetClass wmShellWidgetClass; extern WidgetClass vendorShellWidgetClass; extern WidgetClass transientShellWidgetClass; extern WidgetClass topLevelShellWidgetClass; extern WidgetClass applicationShellWidgetClass; extern WidgetClass sessionShellWidgetClass; |__ The following opaque types and opaque variables are defined for generic operations on widgets whose class is a subclass of Shell. ----------------------------------------------------------- Types Variables ----------------------------------------------------------- ShellWidget shellWidgetClass OverrideShellWidget overrideShellWidgetClass WMShellWidget wmShellWidgetClass VendorShellWidget vendorShellWidgetClass TransientShellWidget transientShellWidgetClass TopLevelShellWidget topLevelShellWidgetClass ApplicationShellWidget applicationShellWidgetClass SessionShellWidget sessionShellWidgetClass ShellWidgetClass OverrideShellWidgetClass WMShellWidgetClass VendorShellWidgetClass TransientShellWidgetClass TopLevelShellWidgetClass ApplicationShellWidgetClass SessionShellWidgetClass ----------------------------------------------------------- The declarations for all Intrinsics-defined shells except VendorShell appear in Shell.h and ShellP.h. VendorShell has separate public and private .h files which are included by 108 X Toolkit Intrinsics X11 Release 6.4 Shell.h and ShellP.h. Shell.h uses incomplete structure definitions to ensure that the compiler catches attempts to access private data in any of the Shell instance or class data structures. The symbolic constant for the ShellClassExtension version identifier is XtShellExtensionVersion (see Section 1.6.12). The root_geometry_manager procedure acts as the parent geom- etry manager for geometry requests made by shell widgets. When a shell widget calls either XtMakeGeometryRequest or XtMakeResizeRequest, the root_geometry_manager procedure is invoked to negotiate the new geometry with the window man- ager. If the window manager permits the new geometry, the root_geometry_manager procedure should return XtGeometryYes; if the window manager denies the geometry request or does not change the window geometry within some timeout interval (equal to wm_timeout in the case of WMShells), the root_geometry_manager procedure should return XtGeometryNo. If the window manager makes some alternative geometry change, the root_geometry_manager procedure may return either XtGeometryNo and handle the new geometry as a resize or XtGeometryAlmost in anticipation that the shell will accept the compromise. If the compromise is not accepted, the new size must then be handled as a resize. Subclasses of Shell that wish to provide their own root_geometry_man- ager procedures are strongly encouraged to use enveloping to invoke their superclass's root_geometry_manager procedure under most situations, as the window manager interaction may be very complex. If no ShellClassPart extension record is declared with record_type equal to NULLQUARK, then XtInheritRootGeometry- Manager is assumed. 4.1.2. ShellPart Definition The various shell widgets have the following additional instance fields defined in their widget records: 109 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { String geometry; XtCreatePopupChildProc create_popup_child_proc; XtGrabKind grab_kind; Boolean spring_loaded; Boolean popped_up; Boolean allow_shell_resize; Boolean client_specified; Boolean save_under; Boolean override_redirect; XtCallbackList popup_callback; XtCallbackList popdown_callback; Visual * visual; } ShellPart; typedef struct { int empty; } OverrideShellPart; typedef struct { String title; int wm_timeout; Boolean wait_for_wm; Boolean transient; Boolean urgency; Widget client_leader; String window_role; struct _OldXSizeHints { long flags; int x, y; int width, height; int min_width, min_height; int max_width, max_height; int width_inc, height_inc; struct { int x; int y; } min_aspect, max_aspect; } size_hints; XWMHints wm_hints; int base_width, base_height, win_gravity; Atom title_encoding; } WMShellPart; typedef struct { int vendor_specific; } VendorShellPart; typedef struct { 110 X Toolkit Intrinsics X11 Release 6.4 Widget transient_for; } TransientShellPart; typedef struct { String icon_name; Boolean iconic; Atom icon_name_encoding; } TopLevelShellPart; typedef struct { char * class; XrmClass xrm_class; int argc; char ** argv; } ApplicationShellPart; typedef struct { SmcConn connection; String session_id; String * restart_command; String * clone_command; String * discard_command; String * resign_command; String * shutdown_command; String * environment; String current_dir; String program_path; unsigned char restart_style; Boolean join_session; XtCallbackList save_callbacks; XtCallbackList interact_callbacks; XtCallbackList cancel_callbacks; XtCallbackList save_complete_callbacks; XtCallbackList die_callbacks; XtCallbackList error_callbacks; } SessionShellPart; |__ 111 X Toolkit Intrinsics X11 Release 6.4 The full shell widget instance record definitions are: __ | typedef struct { CorePart core; CompositePart composite; ShellPart shell; } ShellRec, *ShellWidget; typedef struct { CorePart core; CompositePart composite; ShellPart shell; OverrideShellPart override; } OverrideShellRec, *OverrideShellWidget; typedef struct { CorePart core; CompositePart composite; ShellPart shell; WMShellPart wm; } WMShellRec, *WMShellWidget; typedef struct { CorePart core; CompositePart composite; ShellPart shell; WMShellPart wm; VendorShellPart vendor; } VendorShellRec, *VendorShellWidget; typedef struct { CorePart core; CompositePart composite; ShellPart shell; WMShellPart wm; VendorShellPart vendor; TransientShellPart transient; } TransientShellRec, *TransientShellWidget; 112 X Toolkit Intrinsics X11 Release 6.4 typedef struct { CorePart core; CompositePart composite; ShellPart shell; WMShellPart wm; VendorShellPart vendor; TopLevelShellPart topLevel; } TopLevelShellRec, *TopLevelShellWidget; typedef struct { CorePart core; CompositePart composite; ShellPart shell; WMShellPart wm; VendorShellPart vendor; TopLevelShellPart topLevel; ApplicationShellPart application; } ApplicationShellRec, *ApplicationShellWidget; typedef struct { CorePart core; CompositePart composite; ShellPart shell; WMShellPart wm; VendorShellPart vendor; TopLevelShellPart topLevel; ApplicationShellPart application; SessionShellPart session; } SessionShellRec, *SessionShellWidget; |__ 4.1.3. Shell Resources The resource names, classes, and representation types speci- fied in the shellClassRec resource list are: ------------------------------------------------------------------- Name Class Representation ------------------------------------------------------------------- XtNallowShellResize XtCAllowShellResize XtRBoolean XtNcreatePopupChildProc XtCCreatePopupChildProc XtRFunction XtNgeometry XtCGeometry XtRString XtNoverrideRedirect XtCOverrideRedirect XtRBoolean XtNpopdownCallback XtCCallback XtRCallback XtNpopupCallback XtCCallback XtRCallback XtNsaveUnder XtCSaveUnder XtRBoolean 113 X Toolkit Intrinsics X11 Release 6.4 XtNvisual XtCVisual XtRVisual ------------------------------------------------------------------- OverrideShell declares no additional resources beyond those defined by Shell. The resource names, classes, and representation types speci- fied in the wmShellClassRec resource list are: -------------------------------------------------------------------------- Name Class Representation -------------------------------------------------------------------------- XtNbaseHeight XtCBaseHeight XtRInt XtNbaseWidth XtCBaseWidth XtRInt XtNclientLeader XtCClientLeader XtRWidget XtNheightInc XtCHeightInc XtRInt XtNiconMask XtCIconMask XtRBitmap XtNiconPixmap XtCIconPixmap XtRBitmap XtNiconWindow XtCIconWindow XtRWindow XtNiconX XtCIconX XtRInt XtNiconY XtCIconY XtRInt XtNinitialState XtCInitialState XtRInitialState XtNinput XtCInput XtRBool XtNmaxAspectX XtCMaxAspectX XtRInt XtNmaxAspectY XtCMaxAspectY XtRInt XtNmaxHeight XtCMaxHeight XtRInt XtNmaxWidth XtCMaxWidth XtRInt XtNminAspectX XtCMinAspectX XtRInt XtNminAspectY XtCMinAspectY XtRInt XtNminHeight XtCMinHeight XtRInt XtNminWidth XtCMinWidth XtRInt XtNtitle XtCTitle XtRString XtNtitleEncoding XtCTitleEncoding XtRAtom XtNtransient XtCTransient XtRBoolean XtNwaitforwm, XtNwaitForWm XtCWaitforwm, XtCWaitForWm XtRBoolean XtNwidthInc XtCWidthInc XtRInt XtNwindowRole XtCWindowRole XtRString XtNwinGravity XtCWinGravity XtRGravity XtNwindowGroup XtCWindowGroup XtRWindow XtNwmTimeout XtCWmTimeout XtRInt XtNurgency XtCUrgency XtRBoolean -------------------------------------------------------------------------- The class resource list for VendorShell is implementation- defined. The resource names, classes, and representation types that are specified in the transientShellClassRec resource list are: 114 X Toolkit Intrinsics X11 Release 6.4 ------------------------------------------------------- Name Class Representation ------------------------------------------------------- XtNtransientFor XtCTransientFor XtRWidget ------------------------------------------------------- The resource names, classes, and representation types that are specified in the topLevelShellClassRec resource list are: ----------------------------------------------------------- Name Class Representation ----------------------------------------------------------- XtNiconName XtCIconName XtRString XtNiconNameEncoding XtCIconNameEncoding XtRAtom XtNiconic XtCIconic XtRBoolean ----------------------------------------------------------- The resource names, classes, and representation types that are specified in the applicationShellClassRec resource list are: ------------------------------------------------------- Name Class Representation ------------------------------------------------------- XtNargc XtCArgc XtRInt XtNargv XtCArgv XtRStringArray ------------------------------------------------------- 115 X Toolkit Intrinsics X11 Release 6.4 The resource names, classes, and representation types that are specified in the sessionShellClassRec resource list are: -------------------------------------------------------------------- Name Class Representation -------------------------------------------------------------------- XtNcancelCallback XtCCallback XtRCallback XtNcloneCommand XtCCloneCommand XtRCommandArgArray XtNconnection XtCConnection XtRSmcConn XtNcurrentDirectory XtCCurrentDirectory XtRDirectoryString XtNdieCallback XtCCallback XtRCallback XtNdiscardCommand XtCDiscardCommand XtRCommandArgArray XtNenvironment XtCEnvironment XtREnvironmentArray XtNerrorCallback XtCCallback XtRCallback XtNinteractCallback XtCCallback XtRCallback XtNjoinSession XtCJoinSession XtRBoolean XtNprogramPath XtCProgramPath XtRString XtNresignCommand XtCResignCommand XtRCommandArgArray XtNrestartCommand XtCRestartCommand XtRCommandArgArray XtNrestartStyle XtCRestartStyle XtRRestartStyle XtNsaveCallback XtCCallback XtRCallback XtNsaveCompleteCallback XtCCallback XtRCallback XtNsessionID XtCSessionID XtRString XtNshutdownCommand XtCShutdownCommand XtRCommandArgArray -------------------------------------------------------------------- 4.1.4. ShellPart Default Values The default values for fields common to all classes of pub- lic shells (filled in by the Shell resource lists and the Shell initialize procedures) are: --------------------------------------------------------- Field Default Value --------------------------------------------------------- geometry NULL create_popup_child_proc NULL grab_kind (none) spring_loaded (none) popped_up False allow_shell_resize False client_specified (internal) save_under True for OverrideShell and TransientShell, False other- wise override_redirect True for OverrideShell, False otherwise popup_callback NULL popdown_callback NULL visual CopyFromParent --------------------------------------------------------- 116 X Toolkit Intrinsics X11 Release 6.4 The geometry field specifies the size and position and is usually given only on a command line or in a defaults file. If the geometry field is non-NULL when a widget of class WMShell is realized, the geometry specification is parsed using XWMGeometry with a default geometry string constructed from the values of x, y, width, height, width_inc, and height_inc and the size and position flags in the window manager size hints are set. If the geometry specifies an x or y position, then USPosition is set. If the geometry specifies a width or height, then USSize is set. Any fields in the geometry specification override the corresponding values in the Core x, y, width, and height fields. If geom- etry is NULL or contains only a partial specification, then the Core x, y, width, and height fields are used and PPosi- tion and PSize are set as appropriate. The geometry string is not copied by any of the Intrinsics Shell classes; a client specifying the string in an arglist or varargs list must ensure that the value remains valid until the shell widget is realized. For further information on the geometry string, see Section 16.4 in Xlib -- C Language X Interface. The create_popup_child_proc procedure is called by the XtPopup procedure and may remain NULL. The grab_kind, spring_loaded, and popped_up fields maintain widget state information as described under XtPopup, XtMenuPopup, XtPop- down, and XtMenuPopdown. The allow_shell_resize field con- trols whether the widget contained by the shell is allowed to try to resize itself. If allow_shell_resize is False, any geometry requests made by the child will always return XtGeometryNo without interacting with the window manager. Setting save_under True instructs the server to attempt to save the contents of windows obscured by the shell when it is mapped and to restore those contents automatically when the shell is unmapped. It is useful for pop-up menus. Set- ting override_redirect True determines whether the window manager can intercede when the shell window is mapped. For further information on override_redirect, see Section 3.2 in Xlib -- C Language X Interface and Sections 4.1.10 and 4.2.2 in the Inter-Client Communication Conventions Manual. The pop-up and pop-down callbacks are called during XtPopup and XtPopdown. The default value of the visual resource is the symbolic value CopyFromParent. The Intrinsics do not need to query the parent's visual type when the default value is used; if a client using XtGetValues to examine the visual type receives the value CopyFromParent, it must then use XGetWindowAttributes if it needs the actual visual type. The default values for Shell fields in WMShell and its sub- classes are: 117 X Toolkit Intrinsics X11 Release 6.4 ---------------------------------------------------------- Field Default Value ---------------------------------------------------------- title Icon name, if specified, otherwise the application's name wm_timeout Five seconds, in units of milliseconds wait_for_wm True transient True for TransientShell, False otherwise urgency False client_leader NULL window_role NULL min_width XtUnspecifiedShellInt min_height XtUnspecifiedShellInt max_width XtUnspecifiedShellInt max_height XtUnspecifiedShellInt width_inc XtUnspecifiedShellInt height_inc XtUnspecifiedShellInt min_aspect_x XtUnspecifiedShellInt min_aspect_y XtUnspecifiedShellInt max_aspect_x XtUnspecifiedShellInt max_aspect_y XtUnspecifiedShellInt input False initial_state Normal icon_pixmap None icon_window None icon_x XtUnspecifiedShellInt icon_y XtUnspecifiedShellInt icon_mask None window_group XtUnspecifiedWindow base_width XtUnspecifiedShellInt base_height XtUnspecifiedShellInt win_gravity XtUnspecifiedShellInt title_encoding See text ---------------------------------------------------------- The title and title_encoding fields are stored in the WM_NAME property on the shell's window by the WMShell real- ize procedure. If the title_encoding field is None, the title string is assumed to be in the encoding of the current locale and the encoding of the WM_NAME property is set to XStdICCTextStyle. If a language procedure has not been set the default value of title_encoding is XA_STRING, otherwise the default value is None. The wm_timeout field specifies, in milliseconds, the amount of time a shell is to wait for confirmation of a geometry request to the window manager. If none comes back within that time, the shell assumes the window manager is not functioning properly and sets wait_for_wm to False (later events may reset this value). When wait_for_wm is False, the shell does not wait for a response, but relies on asynchronous notification. If tran- sient is True, the WM_TRANSIENT_FOR property will be stored on the shell window with a value as specified below. The interpretation of this property is specific to the window 118 X Toolkit Intrinsics X11 Release 6.4 manager under which the application is run; see the Inter- Client Communication Conventions Manual for more details. The realize and set_values procedures of WMShell store the WM_CLIENT_LEADER property on the shell window. When client_leader is not NULL and the client leader widget is realized, the property will be created with the value of the window of the client leader widget. When client_leader is NULL and the shell widget has a NULL parent, the widget's window is used as the value of the property. When client_leader is NULL and the shell widget has a non-NULL parent, a search is made for the closest shell ancestor with a non-NULL client_leader, and if none is found the shell ancestor with a NULL parent is the result. If the resulting widget is realized, the property is created with the value of the widget's window. When the value of window_role is not NULL, the realize and set_values procedures store the WM_WINDOW_ROLE property on the shell's window with the value of the resource. All other resources specify fields in the window manager hints and the window manager size hints. The realize and set_values procedures of WMShell set the corresponding flag bits in the hints if any of the fields contain nondefault values. In addition, if a flag bit is set that refers to a field with the value XtUnspecifiedShellInt, the value of the field is modified as follows: ------------------------------------------------------------ Field Replacement ------------------------------------------------------------ base_width, base_height 0 width_inc, height_inc 1 max_width, max_height 32767 min_width, min_height 1 min_aspect_x, min_aspect_y -1 max_aspect_x, max_aspect_y -1 icon_x, icon_y -1 win_gravity Value returned by XWMGeometry if called, else NorthWestGrav- ity ------------------------------------------------------------ If the shell widget has a non-NULL parent, then the realize and set_values procedures replace the value XtUnspecified- Window in the window_group field with the window id of the root widget of the widget tree if the root widget is real- ized. The symbolic constant XtUnspecifiedWindowGroup may be used to indicate that the window_group hint flag bit is not to be set. If transient is True, the shell's class is not a 119 X Toolkit Intrinsics X11 Release 6.4 subclass of TransientShell, and window_group is not XtUn- specifiedWindowGroup, the WMShell realize and set_values procedures then store the WM_TRANSIENT_FOR property with the value of window_group. Transient shells have the following additional resource: ------------------------------ Field Default Value ------------------------------ transient_for NULL ------------------------------ The realize and set_values procedures of TransientShell store the WM_TRANSIENT_FOR property on the shell window if transient is True. If transient_for is non-NULL and the widget specified by transient_for is realized, then its win- dow is used as the value of the WM_TRANSIENT_FOR property; otherwise, the value of window_group is used. TopLevel shells have the the following additional resources: ----------------------------------------- Field Default Value ----------------------------------------- icon_name Shell widget's name iconic False icon_name_encoding See text ----------------------------------------- The icon_name and icon_name_encoding fields are stored in the WM_ICON_NAME property on the shell's window by the TopLevelShell realize procedure. If the icon_name_encoding field is None, the icon_name string is assumed to be in the encoding of the current locale and the encoding of the WM_ICON_NAME property is set to XStdICCTextStyle. If a lan- guage procedure has not been set, the default value of icon_name_encoding is XA_STRING, otherwise the default value is None. The iconic field may be used by a client to request that the window manager iconify or deiconify the shell; the TopLevelShell set_values procedure will send the appropriate WM_CHANGE_STATE message (as specified by the Inter-Client Communication Conventions Manual) if this resource is changed from False to True and will call XtPopup specifying grab_kind as XtGrabNone if iconic is changed from True to False. The XtNiconic resource is also an alterna- tive way to set the XtNinitialState resource to indicate that a shell should be initially displayed as an icon; the TopLevelShell initialize procedure will set initial_state to IconicState if iconic is True. 120 X Toolkit Intrinsics X11 Release 6.4 Application shells have the following additional resources: ---------------------- Field Default Value ---------------------- argc 0 argv NULL ---------------------- The argc and argv fields are used to initialize the standard property WM_COMMAND. See the Inter-Client Communication Conventions Manual for more information. The default values for the SessionShell instance fields, which are filled in from the resource lists and by the ini- tialize procedure, are --------------------------------------------- Field Default Value --------------------------------------------- cancel_callbacks NULL clone_command See text connection NULL current_dir NULL die_callbacks NULL discard_command NULL environment NULL error_callbacks NULL interact_callbacks NULL join_session True program_path See text resign_command NULL restart_command See text restart_style SmRestartIfRunning save_callbacks NULL save_complete_callbacks NULL session_id NULL shutdown_command NULL --------------------------------------------- The connection field contains the session connection object or NULL if a session connection is not being managed by this widget. The session_id is an identification assigned to the session participant by the session manager. The session_id will be passed to the session manager as the client identifier of the previous session. When a connection is established with the session manager, the client id assigned by the session manager is stored in the session_id field. When not NULL, the session_id of the Session shell widget that is at the root of the widget tree of the client leader widget will be 121 X Toolkit Intrinsics X11 Release 6.4 used to create the SM_CLIENT_ID property on the client leader's window. If join_session is False, the widget will not attempt to establish a connection to the session manager at shell cre- ation time. See Sections 4.2.1 and 4.2.4 for more informa- tion on the functionality of this resource. The restart_command, clone_command, discard_command, resign_command, shutdown_command, environment, current_dir, program_path, and restart_style fields contain standard ses- sion properties. When a session connection is established or newly managed by the shell, the shell initialize and set_values methods check the values of the restart_command, clone_command, and pro- gram_path resources. At that time, if restart_command is NULL, the value of the argv resource will be copied to restart_command. Whether or not restart_command was NULL, if "-xtsessionID" "" does not already appear in the restart_command, it will be added by the initialize and set_values methods at the beginning of the command argu- ments; if the "-xtsessionID" argument already appears with an incorrect session id in the following argument, that argument will be replaced with the current session id. After this, the shell initialize and set_values procedures check the clone_command. If clone_command is NULL, restart_command will be copied to clone_command, except the "-xtsessionID" and following argument will not be copied. Finally, the shell initialize and set_values procedures check the program_path. If program_path is NULL, the first element of restart_command is copied to program_path. The possible values of restart_style are SmRestartIfRunning, SmRestartAnyway, SmRestartImmediately, and SmRestartNever. A resource converter is registered for this resource; for the strings that it recognizes, see Section 9.6.1. The resource type EnvironmentArray is a NULL-terminated array of pointers to strings; each string has the format "name=value". The `=' character may not appear in the name, and the string is terminated by a null character. 4.2. Session Participation Applications can participate in a user's session, exchanging messages with the session manager as described in the X Ses- sion Management Protocol and the X Session Management Library. 122 X Toolkit Intrinsics X11 Release 6.4 When a widget of sessionShellWidgetClass or a subclass is created, the widget provides support for the application as a session participant and continues to provide support until the widget is destroyed. 4.2.1. Joining a Session When a Session shell is created, if connection is NULL, and if join_session is True, and if argv or restart_command is not NULL, and if in POSIX environments the SESSION_MANAGER environment variable is defined, the shell will attempt to establish a new connection with the session manager. To transfer management of an existing session connection from an application to the shell at widget creation time, pass the existing session connection ID as the connection resource value when creating the Session shell, and if the other creation-time conditions on session participation are met, the widget will maintain the connection with the ses- sion manager. The application must ensure that only one Session shell manages the connection. In the Session shell set_values procedure, if join_session changes from False to True and connection is NULL and when in POSIX environments the SESSION_MANAGER environment vari- able is defined, the shell will attempt to open a connection to the session manager. If connection changes from NULL to non-NULL, the Session shell will take over management of that session connection and will set join_session to True. If join_session changes from False to True and connection is not NULL, the Session shell will take over management of the session connection. When a successful connection has been established, connec- tion contains the session connection ID for the session par- ticipant. When the shell begins to manage the connection, it will call XtAppAddInput to register the handler which watches for protocol messages from the session manager. When the attempt to connect fails, a warning message is issued and connection is set to NULL. While the connection is being managed, if a SaveYourself, SaveYourselfPhase2, Interact, ShutdownCancelled, SaveCom- plete, or Die message is received from the session manager, the Session shell will call out to application callback pro- cedures registered on the respective callback list of the Session shell and will send SaveYourselfPhase2Request, InteractRequest, InteractDone, SaveYourselfDone, and Connec- tionClosed messages as appropriate. Initially, all of the client's session properties are undefined. When any of the session property resource values are defined or change, the Session shell initialize and set_values procedures will update the client's session property value by a 123 X Toolkit Intrinsics X11 Release 6.4 SetProperties or a DeleteProperties message, as appropriate. The session ProcessID and UserID properties are always set by the shell when it is possible to determine the value of these properties. 4.2.2. Saving Application State The session manager instigates an application checkpoint by sending a SaveYourself request. Applications are responsi- ble for saving their state in response to the request. When the SaveYourself request arrives, the procedures regis- tered on the Session shell's save callback list are called. If the application does not register any save callback pro- cedures on the save callback list, the shell will report to the session manager that the application failed to save its state. Each procedure on the save callback list receives a token in the call_data parameter. The checkpoint token in the call_data parameter is of type XtCheckpointToken. __ | typedef struct { int save_type; int interact_style; Boolean shutdown; Boolean fast; Boolean cancel_shutdown int phase; int interact_dialog_type;/* return */ Boolean request_cancel; /* return */ Boolean request_next_phase; /* return */ Boolean save_success; /* return */ } XtCheckpointTokenRec, *XtCheckpointToken; |__ The save_type, interact_style, shutdown, and fast fields of the token contain the parameters of the SaveYourself mes- sage. The possible values of save_type are SmSaveLocal, SmSaveGlobal, and SmSaveBoth; these indicate the type of information to be saved. The possible values of inter- act_style are SmInteractStyleNone, SmInteractStyleErrors, and SmInteractStyleAny; these indicate whether user interac- tion would be permitted and, if so, what kind of interac- tion. If shutdown is True, the checkpoint is being per- formed in preparation for the end of the session. If fast is True, the client should perform the checkpoint as quickly as possible. If cancel_shutdown is True, a ShutdownCan- celled message has been received for the current save 124 X Toolkit Intrinsics X11 Release 6.4 operation. (See Section 4.4.4.) The phase is used by man- ager clients, such as a window manager, to distinguish between the first and second phase of a save operation. The phase will be either 1 or 2. The remaining fields in the checkpoint token structure are provided for the application to communicate with the shell. Upon entry to the first application save callback procedure, the return fields in the token have the following initial values: interact_dialog_type is SmDialogNormal; request_can- cel is False; request_next_phase is False; and save_success is True. When a token is returned with any of the four return fields containing a noninitial value, and when the field is applicable, subsequent tokens passed to the appli- cation during the current save operation will always contain the noninitial value. The purpose of the token's save_success field is to indicate the outcome of the entire operation to the session manager and ultimately, to the user. Returning False indicates some portion of the application state could not be successfully saved. If any token is returned to the shell with save_suc- cess False, tokens subsequently received by the application for the current save operation will show save_success as False. When the shell sends the final status of the check- point to the session manager, it will indicate failure to save application state if any token was returned with save_success False. Session participants that manage and save the state of other clients should structure their save or interact callbacks to set request_next_phase to True when phase is 1, which will cause the shell to send the SaveYourselfPhase2Request when the first phase is complete. When the SaveYourselfPhase2 message is received, the shell will invoke the save call- backs a second time with phase equal to 2. Manager clients should save the state of other clients when the callbacks are invoked the second time and phase equal to 2. The application may request additional tokens while a check- point is under way, and these additional tokens must be returned by an explicit call. 125 X Toolkit Intrinsics X11 Release 6.4 To request an additional token for a save callback response that has a deferred outcome, use XtSessionGetToken. __ | XtCheckpointToken XtSessionGetToken(widget) Widget widget; widget Specifies the Session shell widget which manages session participation. |__ The XtSessionGetToken function will return NULL if no check- point operation is currently under way. To indicate the completion of checkpoint processing includ- ing user interaction, the application must signal the Ses- sion shell by returning all tokens. (See Sections 4.2.2.2 and 4.2.2.4). To return a token, use XtSessionReturnToken. __ | void XtSessionReturnToken(token) XtCheckpointToken token; token Specifies a token that was received as the call_data by a procedure on the interact callback list or a token that was received by a call to XtSessionGetToken. |__ Tokens passed as call_data to save callbacks are implicitly returned when the save callback procedure returns. A save callback procedure should not call XtSessionReturnToken on the token passed in its call_data. 4.2.2.1. Requesting Interaction When the token interact_style allows user interaction, the application may interact with the user during the check- point, but must wait for permission to interact. Applica- tions request permission to interact with the user during the checkpointing operation by registering a procedure on the Session shell's interact callback list. When all save callback procedures have returned, and each time a token that was granted by a call to XtSessionGetToken is returned, the Session shell examines the interact callback list. If interaction is permitted and the interact callback list is not empty, the shell will send an InteractRequest to the 126 X Toolkit Intrinsics X11 Release 6.4 session manager when an interact request is not already out- standing for the application. The type of interaction dialog that will be requested is specified by the interact_dialog_type field in the check- point token. The possible values for interact_dialog_type are SmDialogError and SmDialogNormal. If a token is returned with interact_dialog_type containing SmDialogError, the interact request and any subsequent interact requests will be for an error dialog; otherwise, the request will be for a normal dialog with the user. When a token is returned with save_success False or inter- act_dialog_type SmDialogError, tokens subsequently passed to callbacks during the same active SaveYourself response will reflect these changed values, indicating that an error con- dition has occurred during the checkpoint. The request_cancel field is a return value for interact callbacks only. Upon return from a procedure on the save callback list, the value of the token's request_cancel field is not examined by the shell. This is also true of tokens received through a call to XtSessionGetToken. 4.2.2.2. Interacting with the User during a Checkpoint When the session manager grants the application's request for user interaction, the Session shell receives an Interact message. The procedures registered on the interact callback list are executed, but not as if executing a typical call- back list. These procedures are individually executed in sequence, with a checkpoint token functioning as the sequencing mechanism. Each step in the sequence begins by removing a procedure from the interact callback list and executing it with a token passed in the call_data. The interact callback will typically pop up a dialog box and return. When the user interaction and associated applica- tion checkpointing has completed, the application must return the token by calling XtSessionReturnToken. Returning the token completes the current step and triggers the next step in the sequence. During interaction the client may request cancellation of a shutdown. When a token passed as call_data to an interact procedure is returned, if shutdown is True and cancel_shut- down is False, request_cancel indicates whether the applica- tion requests that the pending shutdown be cancelled. If request_cancel is True, the field will also be True in any tokens subsequently granted during the checkpoint operation. When a token is returned requesting cancellation of the ses- sion shutdown, pending interact procedures will still be called by the Session shell. When all interact procedures have been removed from the interact callback list, executed, 127 X Toolkit Intrinsics X11 Release 6.4 and the final interact token returned to the shell, an InteractDone message is sent to the session manager, indi- cating whether a pending session shutdown is requested to be cancelled. 4.2.2.3. Responding to a Shutdown Cancellation Callbacks registered on the cancel callback list are invoked when the Session shell processes a ShutdownCancelled message from the session manager. This may occur during the pro- cessing of save callbacks, while waiting for interact per- mission, during user interaction, or after the save opera- tion is complete and the application is expecting a SaveCom- plete or a Die message. The call_data for these callbacks is NULL. When the shell notices that a pending shutdown has been can- celled, the token cancel_shutdown field will be True in tokens subsequently given to the application. Receiving notice of a shutdown cancellation does not cancel the pending execution of save callbacks or interact call- backs. After the cancel callbacks execute, if inter- act_style is not SmInteractStyleNone and the interact list is not empty, the procedures on the interact callback list will be executed and passed a token with interact_style SmInteractStyleNone. The application should not interact with the user, and the Session shell will not send an Inter- actDone message. 4.2.2.4. Completing a Save When there is no user interaction, the shell regards the application as having finished saving state when all call- back procedures on the save callback list have returned, and any additional tokens passed out by XtSessionGetToken have been returned by corresponding calls to XtSessionReturnTo- ken. If the save operation involved user interaction, the above completion conditions apply, and in addition, all requests for interaction have been granted or cancelled, and all tokens passed to interact callbacks have been returned through calls to XtSessionReturnToken. If the save opera- tion involved a manager client that requested the second phase, the above conditions apply to both the first and sec- ond phase of the save operation. When the application has finished saving state, the Session shell will report the result to the session manager by send- ing the SaveYourselfDone message. If the session is contin- uing, the shell will receive the SaveComplete message when all applications have completed saving state. This message indicates that applications may again allow changes to their 128 X Toolkit Intrinsics X11 Release 6.4 state. The shell will execute the save_complete callbacks. The call_data for these callbacks is NULL. 4.2.3. Responding to a Shutdown Callbacks registered on the die callback list are invoked when the session manager sends a Die message. The callbacks on this list should do whatever is appropriate to quit the application. Before executing procedures on the die call- back list, the Session shell will close the connection to the session manager and will remove the handler that watches for protocol messages. The call_data for these callbacks is NULL. 4.2.4. Resigning from a Session When the Session shell widget is destroyed, the destroy method will close the connection to the session manager by sending a ConnectionClosed protocol message and will remove the input callback that was watching for session protocol messages. When XtSetValues is used to set join_session to False, the set_values method of the Session shell will close the con- nection to the session manager if one exists by sending a ConnectionClosed message, and connection will be set to NULL. Applications that exit in response to user actions and that do not wait for phase 2 destroy to complete on the Session shell should set join_session to False before exiting. When XtSetValues is used to set connection to NULL, the Ses- sion shell will stop managing the connection, if one exists. However, that session connection will not be closed. Applications that wish to ensure continuation of a session connection beyond the destruction of the shell should first retrieve the connection resource value, then set the connec- tion resource to NULL, and then they may safely destroy the widget without losing control of the session connection. The error callback list will be called if an unrecoverable communications error occurs while the shell is managing the connection. The shell will close the connection, set con- nection to NULL, remove the input callback, and call the procedures registered on the error callback list. The call_data for these callbacks is NULL. 129 X Toolkit Intrinsics X11 Release 6.4 Chapter 5 Pop-Up Widgets Pop-up widgets are used to create windows outside of the window hierarchy defined by the widget tree. Each pop-up child has a window that is a descendant of the root window, so that the pop-up window is not clipped by the pop-up wid- get's parent window. Therefore, pop-ups are created and attached differently to their widget parent than normal wid- get children. A parent of a pop-up widget does not actively manage its pop-up children; in fact, it usually does not operate upon them in any way. The popup_list field in the CorePart structure contains the list of its pop-up children. This pop-up list exists mainly to provide the proper place in the widget hierarchy for the pop-up to get resources and to pro- vide a place for XtDestroyWidget to look for all extant children. A composite widget can have both normal and pop-up children. A pop-up can be popped up from almost anywhere, not just by its parent. The term child always refers to a normal, geom- etry-managed widget on the composite widget's list of chil- dren, and the term pop-up child always refers to a widget on the pop-up list. 5.1. Pop-Up Widget Types There are three kinds of pop-up widgets: o Modeless pop-ups A modeless pop-up (for example, a dialog box that does not prevent continued interaction with the rest of the application) can usually be manipulated by the window manager and looks like any other application window from the user's point of view. The application main window itself is a special case of a modeless pop-up. o Modal pop-ups A modal pop-up (for example, a dialog box that requires user input to continue) can sometimes be manipulated by the window manager, and except for events that occur in the dialog box, it disables user-event distribution to the rest of the application. 130 X Toolkit Intrinsics X11 Release 6.4 o Spring-loaded pop-ups A spring-loaded pop-up (for example, a menu) can seldom be manipulated by the window manager, and except for events that occur in the pop-up or its descendants, it disables user-event distribution to all other applica- tions. Modal pop-ups and spring-loaded pop-ups are very similar and should be coded as if they were the same. In fact, the same widget (for example, a ButtonBox or Menu widget) can be used both as a modal pop-up and as a spring-loaded pop-up within the same application. The main difference is that spring- loaded pop-ups are brought up with the pointer and, because of the grab that the pointer button causes, require differ- ent processing by the Intrinsics. Furthermore, all user input remap events occurring outside the spring-loaded pop- up (e.g., in a descendant) are also delivered to the spring- loaded pop-up after they have been dispatched to the appro- priate descendant, so that, for example, button-up can take down a spring-loaded pop-up no matter where the button-up occurs. Any kind of pop-up, in turn, can pop up other widgets. Modal and spring-loaded pop-ups can constrain user events to the most recent such pop-up or allow user events to be dis- patched to any of the modal or spring-loaded pop-ups cur- rently mapped. Regardless of their type, all pop-up widget classes are responsible for communicating with the X window manager and therefore are subclasses of one of the Shell widget classes. 5.2. Creating a Pop-Up Shell For a widget to be popped up, it must be the child of a pop- up shell widget. None of the Intrinsics-supplied shells will simultaneously manage more than one child. Both the shell and child taken together are referred to as the pop- up. When you need to use a pop-up, you always refer to the pop-up by the pop-up shell, not the child. To create a pop-up shell, use XtCreatePopupShell. 131 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtCreatePopupShell(name, widget_class, parent, args, num_args) String name; WidgetClass widget_class; Widget parent; ArgList args; Cardinal num_args; name Specifies the instance name for the created shell widget. widget_class Specifies the widget class pointer for the created shell widget. parent Specifies the parent widget. Must be of class Core or any subclass thereof. args Specifies the argument list to override any other resource specifications. num_args Specifies the number of entries in the argument list. |__ The XtCreatePopupShell function ensures that the specified class is a subclass of Shell and, rather than using insert_child to attach the widget to the parent's children list, attaches the shell to the parent's popup_list directly. The screen resource for this widget is determined by first scanning args for the XtNscreen argument. If no XtNscreen argument is found, the resource database associated with the parent's screen is queried for the resource name.screen, class Class.Screen where Class is the class_name field from the CoreClassPart of the specified widget_class. If this query fails, the parent's screen is used. Once the screen is determined, the resource database associated with that screen is used to retrieve all remaining resources for the widget not specified in args. A spring-loaded pop-up invoked from a translation table via XtMenuPopup must already exist at the time that the transla- tion is invoked, so the translation manager can find the shell by name. Pop-ups invoked in other ways can be created when the pop-up actually is needed. This delayed creation of the shell is particularly useful when you pop up an unspecified number of pop-ups. You can look to see if an appropriate unused shell (that is, not currently popped up) exists and create a new shell if needed. 132 X Toolkit Intrinsics X11 Release 6.4 To create a pop-up shell using varargs lists, use XtVaCre- atePopupShell. __ | Widget XtVaCreatePopupShell(name, widget_class, parent, ...) String name; WidgetClass widget_class; Widget parent; name Specifies the instance name for the created shell widget. widget_class Specifies the widget class pointer for the created shell widget. parent Specifies the parent widget. Must be of class Core or any subclass thereof. ... Specifies the variable argument list to override any other resource specifications. |__ XtVaCreatePopupShell is identical in function to XtCre- atePopupShell with the args and num_args parameters replaced by a varargs list as described in Section 2.5.1. 5.3. Creating Pop-Up Children Once a pop-up shell is created, the single child of the pop- up shell can be created either statically or dynamically. At startup, an application can create the child of the pop- up shell, which is appropriate for pop-up children composed of a fixed set of widgets. The application can change the state of the subparts of the pop-up child as the application state changes. For example, if an application creates a static menu, it can call XtSetSensitive (or, in general, XtSetValues) on any of the buttons that make up the menu. Creating the pop-up child early means that pop-up time is minimized, especially if the application calls XtRealizeWid- get on the pop-up shell at startup. When the menu is needed, all the widgets that make up the menu already exist and need only be mapped. The menu should pop up as quickly as the X server can respond. Alternatively, an application can postpone the creation of the child until it is needed, which minimizes application startup time and allows the pop-up child to reconfigure itself each time it is popped up. In this case, the pop-up child creation routine might poll the application to find 133 X Toolkit Intrinsics X11 Release 6.4 out if it should change the sensitivity of any of its sub- parts. Pop-up child creation does not map the pop-up, even if you create the child and call XtRealizeWidget on the pop-up shell. All shells have pop-up and pop-down callbacks, which provide the opportunity either to make last-minute changes to a pop- up child before it is popped up or to change it after it is popped down. Note that excessive use of pop-up callbacks can make popping up occur more slowly. 5.4. Mapping a Pop-Up Widget Pop-ups can be popped up through several mechanisms: o A call to XtPopup or XtPopupSpringLoaded. o One of the supplied callback procedures XtCallbackNone, XtCallbackNonexclusive, or XtCallbackExclusive. o The standard translation action XtMenuPopup. Some of these routines take an argument of type XtGrabKind, which is defined as __ | typedef enum {XtGrabNone, XtGrabNonexclusive, XtGrabExclusive} XtGrabKind; |__ The create_popup_child_proc procedure pointer in the shell widget instance record is of type XtCreatePopupChildProc. __ | typedef void (*XtCreatePopupChildProc)(Widget); Widget w; w Specifies the shell widget being popped up. |__ To map a pop-up from within an application, use XtPopup. 134 X Toolkit Intrinsics X11 Release 6.4 __ | void XtPopup(popup_shell, grab_kind) Widget popup_shell; XtGrabKind grab_kind; popup_shell Specifies the shell widget. grab_kind Specifies the way in which user events should be constrained. |__ The XtPopup function performs the following: o Calls XtCheckSubclass to ensure popup_shell's class is a subclass of shellWidgetClass. o Raises the window and returns if the shell's popped_up field is already True. o Calls the callback procedures on the shell's popup_callback list, specifying a pointer to the value of grab_kind as the call_data argument. o Sets the shell popped_up field to True, the shell spring_loaded field to False, and the shell grab_kind field from grab_kind. o If the shell's create_popup_child_proc field is non- NULL, XtPopup calls it with popup_shell as the parame- ter. o If grab_kind is either XtGrabNonexclusive or XtGrabEx- clusive, it calls XtAddGrab(popup_shell, (grab_kind == XtGrabExclusive), False) o Calls XtRealizeWidget with popup_shell specified. o Calls XMapRaised with the window of popup_shell. To map a spring-loaded pop-up from within an application, use XtPopupSpringLoaded. 135 X Toolkit Intrinsics X11 Release 6.4 __ | void XtPopupSpringLoaded(popup_shell) Widget popup_shell; popup_shell Specifies the shell widget to be popped up. |__ The XtPopupSpringLoaded function performs exactly as XtPopup except that it sets the shell spring_loaded field to True and always calls XtAddGrab with exclusive True and spring- loaded True. To map a pop-up from a given widget's callback list, you also can register one of the XtCallbackNone, XtCallbac- kNonexclusive, or XtCallbackExclusive convenience routines as callbacks, using the pop-up shell widget as the client data. 136 X Toolkit Intrinsics X11 Release 6.4 __ | void XtCallbackNone(w, client_data, call_data) Widget w; XtPointer client_data; XtPointer call_data; w Specifies the widget. client_data Specifies the pop-up shell. call_data Specifies the callback data argument, which is not used by this procedure. void XtCallbackNonexclusive(w, client_data, call_data) Widget w; XtPointer client_data; XtPointer call_data; w Specifies the widget. client_data Specifies the pop-up shell. call_data Specifies the callback data argument, which is not used by this procedure. void XtCallbackExclusive(w, client_data, call_data) Widget w; XtPointer client_data; XtPointer call_data; w Specifies the widget. client_data Specifies the pop-up shell. call_data Specifies the callback data argument, which is not used by this procedure. |__ The XtCallbackNone, XtCallbackNonexclusive, and XtCallback- Exclusive functions call XtPopup with the shell specified by the client_data argument and grab_kind set as the name spec- ifies. XtCallbackNone, XtCallbackNonexclusive, and XtCall- backExclusive specify XtGrabNone, XtGrabNonexclusive, and XtGrabExclusive, respectively. Each function then sets the 137 X Toolkit Intrinsics X11 Release 6.4 widget that executed the callback list to be insensitive by calling XtSetSensitive. Using these functions in callbacks is not required. In particular, an application must provide customized code for callbacks that create pop-up shells dynamically or that must do more than desensitizing the but- ton. Within a translation table, to pop up a menu when a key or pointer button is pressed or when the pointer is moved into a widget, use XtMenuPopup, or its synonym, MenuPopup. From a translation writer's point of view, the definition for this translation action is __ | void XtMenuPopup(shell_name) String shell_name; shell_name Specifies the name of the shell widget to pop up. |__ XtMenuPopup is known to the translation manager, which reg- isters the corresponding built-in action procedure XtMenuPopupAction using XtRegisterGrabAction specifying owner_events True, event_mask ButtonPressMask | ButtonRe- leaseMask, and pointer_mode and keyboard_mode GrabModeAsync. If XtMenuPopup is invoked on ButtonPress, it calls XtPopup- SpringLoaded on the specified shell widget. If XtMenuPopup is invoked on KeyPress or EnterWindow, it calls XtPopup on the specified shell widget with grab_kind set to XtGrab- Nonexclusive. Otherwise, the translation manager generates a warning message and ignores the action. XtMenuPopup tries to find the shell by searching the widget tree starting at the widget in which it is invoked. If it finds a shell with the specified name in the pop-up children of that widget, it pops up the shell with the appropriate parameters. Otherwise, it moves up the parent chain to find a pop-up child with the specified name. If XtMenuPopup gets to the application top-level shell widget and has not found a matching shell, it generates a warning and returns immedi- ately. 5.5. Unmapping a Pop-Up Widget Pop-ups can be popped down through several mechanisms: o A call to XtPopdown 138 X Toolkit Intrinsics X11 Release 6.4 o The supplied callback procedure XtCallbackPopdown o The standard translation action XtMenuPopdown To unmap a pop-up from within an application, use XtPopdown. __ | void XtPopdown(popup_shell) Widget popup_shell; popup_shell Specifies the shell widget to pop down. |__ The XtPopdown function performs the following: o Calls XtCheckSubclass to ensure popup_shell's class is a subclass of shellWidgetClass. o Checks that the popped_up field of popup_shell is True; otherwise, it returns immediately. o Unmaps popup_shell's window and, if override_redirect is False, sends a synthetic UnmapNotify event as speci- fied by the Inter-Client Communication Conventions Man- ual. o If popup_shell's grab_kind is either XtGrabNonexclusive or XtGrabExclusive, it calls XtRemoveGrab. o Sets popup_shell's popped_up field to False. o Calls the callback procedures on the shell's pop- down_callback list, specifying a pointer to the value of the shell's grab_kind field as the call_data argu- ment. To pop down a pop-up from a callback list, you may use the callback XtCallbackPopdown. 139 X Toolkit Intrinsics X11 Release 6.4 __ | void XtCallbackPopdown(w, client_data, call_data) Widget w; XtPointer client_data; XtPointer call_data; w Specifies the widget. client_data Specifies a pointer to the XtPopdownID structure. call_data Specifies the callback data argument, which is not used by this procedure. |__ The XtCallbackPopdown function casts the client_data parame- ter to a pointer of type XtPopdownID. __ | typedef struct { Widget shell_widget; Widget enable_widget; } XtPopdownIDRec, *XtPopdownID; |__ The shell_widget is the pop-up shell to pop down, and the enable_widget is usually the widget that was used to pop it up in one of the pop-up callback convenience procedures. XtCallbackPopdown calls XtPopdown with the specified shell_widget and then calls XtSetSensitive to resensitize enable_widget. Within a translation table, to pop down a spring-loaded menu when a key or pointer button is released or when the pointer is moved into a widget, use XtMenuPopdown or its synonym, MenuPopdown. From a translation writer's point of view, the definition for this translation action is 140 X Toolkit Intrinsics X11 Release 6.4 __ | void XtMenuPopdown(shell_name) String shell_name; shell_name Specifies the name of the shell widget to pop down. |__ If a shell name is not given, XtMenuPopdown calls XtPopdown with the widget for which the translation is specified. If shell_name is specified in the translation table, XtMenuPop- down tries to find the shell by looking up the widget tree starting at the widget in which it is invoked. If it finds a shell with the specified name in the pop-up children of that widget, it pops down the shell; otherwise, it moves up the parent chain to find a pop-up child with the specified name. If XtMenuPopdown gets to the application top-level shell widget and cannot find a matching shell, it generates a warning and returns immediately. 141 X Toolkit Intrinsics X11 Release 6.4 Chapter 6 Geometry Management A widget does not directly control its size and location; rather, its parent is responsible for controlling them. Although the position of children is usually left up to their parent, the widgets themselves often have the best idea of their optimal sizes and, possibly, preferred loca- tions. To resolve physical layout conflicts between sibling widgets and between a widget and its parent, the Intrinsics provide the geometry management mechanism. Almost all composite widgets have a geometry manager specified in the geome- try_manager field in the widget class record that is respon- sible for the size, position, and stacking order of the wid- get's children. The only exception is fixed boxes, which create their children themselves and can ensure that their children will never make a geometry request. 6.1. Initiating Geometry Changes Parents, children, and clients each initiate geometry changes differently. Because a parent has absolute control of its children's geometry, it changes the geometry directly by calling XtMoveWidget, XtResizeWidget, or XtConfigureWid- get. A child must ask its parent for a geometry change by calling XtMakeGeometryRequest or XtMakeResizeRequest. An application or other client code initiates a geometry change by calling XtSetValues on the appropriate geometry fields, thereby giving the widget the opportunity to modify or reject the client request before it gets propagated to the parent and the opportunity to respond appropriately to the parent's reply. When a widget that needs to change its size, position, bor- der width, or stacking depth asks its parent's geometry man- ager to make the desired changes, the geometry manager can allow the request, disallow the request, or suggest a com- promise. When the geometry manager is asked to change the geometry of a child, the geometry manager may also rearrange and resize any or all of the other children that it controls. The geometry manager can move children around freely using XtMoveWidget. When it resizes a child (that is, changes the width, height, or border width) other than the one making 142 X Toolkit Intrinsics X11 Release 6.4 the request, it should do so by calling XtResizeWidget. The requesting child may be given special treatment; see Section 6.5. It can simultaneously move and resize a child with a single call to XtConfigureWidget. Often, geometry managers find that they can satisfy a request only if they can reconfigure a widget that they are not in control of; in particular, the composite widget may want to change its own size. In this case, the geometry manager makes a request to its parent's geometry manager. Geometry requests can cascade this way to arbitrary depth. Because such cascaded arbitration of widget geometry can involve extended negotiation, windows are not actually allo- cated to widgets at application startup until all widgets are satisfied with their geometry; see Sections 2.5 and 2.6. Notes 1. The Intrinsics treatment of stacking requests is deficient in several areas. Stacking requests for unrealized widgets are granted but will have no effect. In addition, there is no way to do an XtSetValues that will gen- erate a stacking geometry request. 2. After a successful geometry request (one that returned XtGeometryYes), a widget does not know whether its resize procedure has been called. Widgets should have resize proce- dures that can be called more than once with- out ill effects. 6.2. General Geometry Manager Requests When making a geometry request, the child specifies an XtWidgetGeometry structure. 143 X Toolkit Intrinsics X11 Release 6.4 __ | typedef unsigned long XtGeometryMask; typedef struct { XtGeometryMask request_mode; Position x, y; Dimension width, height; Dimension border_width; Widget sibling; int stack_mode; } XtWidgetGeometry; |__ To make a general geometry manager request from a widget, use XtMakeGeometryRequest. __ | XtGeometryResult XtMakeGeometryRequest(w, request, reply_return) Widget w; XtWidgetGeometry *request; XtWidgetGeometry *reply_return; w Specifies the widget making the request. Must be of class RectObj or any subclass thereof. request Specifies the desired widget geometry (size, posi- tion, border width, and stacking order). reply_return Returns the allowed widget size, or may be NULL if the requesting widget is not interested in han- dling XtGeometryAlmost. |__ Depending on the condition, XtMakeGeometryRequest performs the following: o If the widget is unmanaged or the widget's parent is not realized, it makes the changes and returns XtGeome- tryYes. o If the parent's class is not a subclass of compos- iteWidgetClass or the parent's geometry_manager field is NULL, it issues an error. o If the widget's being_destroyed field is True, it returns XtGeometryNo. o If the widget x, y, width, height, and border_width fields are all equal to the requested values, it returns XtGeometryYes; otherwise, it calls the parent's 144 X Toolkit Intrinsics X11 Release 6.4 geometry_manager procedure with the given parameters. o If the parent's geometry manager returns XtGeometryYes and if XtCWQueryOnly is not set in request->request_mode and if the widget is realized, XtMakeGeometryRequest calls the XConfigureWindow Xlib function to reconfigure the widget's window (set its size, location, and stacking order as appropriate). o If the geometry manager returns XtGeometryDone, the change has been approved and actually has been done. In this case, XtMakeGeometryRequest does no configuring and returns XtGeometryYes. XtMakeGeometryRequest never returns XtGeometryDone. o Otherwise, XtMakeGeometryRequest just returns the resulting value from the parent's geometry manager. Children of primitive widgets are always unmanaged; there- fore, XtMakeGeometryRequest always returns XtGeometryYes when called by a child of a primitive widget. The return codes from geometry managers are __ | typedef enum { XtGeometryYes, XtGeometryNo, XtGeometryAlmost, XtGeometryDone } XtGeometryResult; |__ The request_mode definitions are from . __ | #define CWX (1<<0) #define CWY (1<<1) #define CWWidth (1<<2) #define CWHeight (1<<3) #define CWBorderWidth (1<<4) #define CWSibling (1<<5) #define CWStackMode (1<<6) |__ The Intrinsics also support the following value. 145 X Toolkit Intrinsics X11 Release 6.4 __ | #define XtCWQueryOnly (1<<7) |__ XtCWQueryOnly indicates that the corresponding geometry request is only a query as to what would happen if this geometry request were made and that no widgets should actu- ally be changed. XtMakeGeometryRequest, like the XConfigureWindow Xlib func- tion, uses request_mode to determine which fields in the XtWidgetGeometry structure the caller wants to specify. The stack_mode definitions are from : __ | #define Above 0 #define Below 1 #define TopIf 2 #define BottomIf 3 #define Opposite 4 |__ The Intrinsics also support the following value. __ | #define XtSMDontChange 5 |__ For definition and behavior of Above, Below, TopIf, Bot- tomIf, and Opposite, see Section 3.7 in Xlib -- C Language X Interface. XtSMDontChange indicates that the widget wants its current stacking order preserved. 6.3. Resize Requests To make a simple resize request from a widget, you can use XtMakeResizeRequest as an alternative to XtMakeGeometry- Request. 146 X Toolkit Intrinsics X11 Release 6.4 __ | XtGeometryResult XtMakeResizeRequest(w, width, height, width_return, height_return) Widget w; Dimension width, height; Dimension *width_return, *height_return; w Specifies the widget making the request. Must be of class RectObj or any subclass thereof. width Specify the desired widget width and height. height width_return Return the allowed widget width and height. height_return |__ The XtMakeResizeRequest function, a simple interface to XtMakeGeometryRequest, creates an XtWidgetGeometry structure and specifies that width and height should change by setting request_mode to CWWidth | CWHeight. The geometry manager is free to modify any of the other window attributes (position or stacking order) to satisfy the resize request. If the return value is XtGeometryAlmost, width_return and height_return contain a compromise width and height. If these are acceptable, the widget should immediately call XtMakeResizeRequest again and request that the compromise width and height be applied. If the widget is not inter- ested in XtGeometryAlmost replies, it can pass NULL for width_return and height_return. 6.4. Potential Geometry Changes Sometimes a geometry manager cannot respond to a geometry request from a child without first making a geometry request to the widget's own parent (the original requestor's grand- parent). If the request to the grandparent would allow the parent to satisfy the original request, the geometry manager can make the intermediate geometry request as if it were the originator. On the other hand, if the geometry manager already has determined that the original request cannot be completely satisfied (for example, if it always denies posi- tion changes), it needs to tell the grandparent to respond to the intermediate request without actually changing the geometry because it does not know if the child will accept the compromise. To accomplish this, the geometry manager uses XtCWQueryOnly in the intermediate request. When XtCWQueryOnly is used, the geometry manager needs to cache enough information to exactly reconstruct the interme- diate request. If the grandparent's response to the inter- mediate query was XtGeometryAlmost, the geometry manager 147 X Toolkit Intrinsics X11 Release 6.4 needs to cache the entire reply geometry in the event the child accepts the parent's compromise. If the grandparent's response was XtGeometryAlmost, it may also be necessary to cache the entire reply geometry from the grandparent when XtCWQueryOnly is not used. If the geometry manager is still able to satisfy the original request, it may immediately accept the grandparent's compro- mise and then act on the child's request. If the grandpar- ent's compromise geometry is insufficient to allow the child's request and if the geometry manager is willing to offer a different compromise to the child, the grandparent's compromise should not be accepted until the child has accepted the new compromise. Note that a compromise geometry returned with XtGeometryAl- most is guaranteed only for the next call to the same wid- get; therefore, a cache of size 1 is sufficient. 6.5. Child Geometry Management: The geometry_manager Proce- dure The geometry_manager procedure pointer in a composite widget class is of type XtGeometryHandler. __ | typedef XtGeometryResult (*XtGeometryHandler)(Widget, XtWidgetGeometry*, XtWidgetGeometry*); Widget w; XtWidgetGeometry *request; XtWidgetGeometry *geometry_return; w Passes the widget making the request. request Passes the new geometry the child desires. geometry_return Passes a geometry structure in which the geome- try manager may store a compromise. |__ A class can inherit its superclass's geometry manager during class initialization. A bit set to zero in the request's request_mode field means that the child widget does not care about the value of the corresponding field, so the geometry manager can change this field as it wishes. A bit set to 1 means that the child wants that geometry element set to the value in the corre- sponding field. 148 X Toolkit Intrinsics X11 Release 6.4 If the geometry manager can satisfy all changes requested and if XtCWQueryOnly is not specified, it updates the wid- get's x, y, width, height, and border_width fields appropri- ately. Then, it returns XtGeometryYes, and the values pointed to by the geometry_return argument are undefined. The widget's window is moved and resized automatically by XtMakeGeometryRequest. Homogeneous composite widgets often find it convenient to treat the widget making the request the same as any other widget, including reconfiguring it using XtConfigureWidget or XtResizeWidget as part of its layout process, unless XtCWQueryOnly is specified. If it does this, it should return XtGeometryDone to inform XtMakeGeometryRequest that it does not need to do the configuration itself. Note To remain compatible with layout techniques used in older widgets (before XtGeometryDone was added to the Intrinsics), a geometry manager should avoid using XtResizeWidget or XtConfigureWidget on the child making the request because the layout process of the child may be in an intermediate state in which it is not prepared to handle a call to its resize procedure. A self-contained widget set may choose this alternative geometry manage- ment scheme, however, provided that it clearly warns widget developers of the compatibility con- sequences. Although XtMakeGeometryRequest resizes the widget's window (if the geometry manager returns XtGeometryYes), it does not call the widget class's resize procedure. The requesting widget must perform whatever resizing calculations are needed explicitly. If the geometry manager disallows the request, the widget cannot change its geometry. The values pointed to by geome- try_return are undefined, and the geometry manager returns XtGeometryNo. Sometimes the geometry manager cannot satisfy the request exactly but may be able to satisfy a similar request. That is, it could satisfy only a subset of the requests (for example, size but not position) or a lesser request (for example, it cannot make the child as big as the request but it can make the child bigger than its current size). In such cases, the geometry manager fills in the structure pointed to by geometry_return with the actual changes it is willing to make, including an appropriate request_mode mask, and returns XtGeometryAlmost. If a bit in geome- try_return->request_mode is zero, the geometry manager 149 X Toolkit Intrinsics X11 Release 6.4 agrees not to change the corresponding value if geome- try_return is used immediately in a new request. If a bit is 1, the geometry manager does change that element to the corresponding value in geometry_return. More bits may be set in geometry_return->request_mode than in the original request if the geometry manager intends to change other fields should the child accept the compromise. When XtGeometryAlmost is returned, the widget must decide if the compromise suggested in geometry_return is acceptable. If it is, the widget must not change its geometry directly; rather, it must make another call to XtMakeGeometryRequest. If the next geometry request from this child uses the geome- try_return values filled in by the geometry manager with an XtGeometryAlmost return and if there have been no interven- ing geometry requests on either its parent or any of its other children, the geometry manager must grant the request, if possible. That is, if the child asks immediately with the returned geometry, it should get an answer of XtGeome- tryYes. However, dynamic behavior in the user's window man- ager may affect the final outcome. To return XtGeometryYes, the geometry manager frequently rearranges the position of other managed children by calling XtMoveWidget. However, a few geometry managers may some- times change the size of other managed children by calling XtResizeWidget or XtConfigureWidget. If XtCWQueryOnly is specified, the geometry manager must return data describing how it would react to this geometry request without actually moving or resizing any widgets. Geometry managers must not assume that the request and geom- etry_return arguments point to independent storage. The caller is permitted to use the same field for both, and the geometry manager must allocate its own temporary storage, if necessary. 6.6. Widget Placement and Sizing To move a sibling widget of the child making the geometry request, the parent uses XtMoveWidget. 150 X Toolkit Intrinsics X11 Release 6.4 __ | void XtMoveWidget(w, x, y) Widget w; Position x; Position y; w Specifies the widget. Must be of class RectObj or any subclass thereof. x y Specify the new widget x and y coordinates. |__ The XtMoveWidget function returns immediately if the speci- fied geometry fields are the same as the old values. Other- wise, XtMoveWidget writes the new x and y values into the object and, if the object is a widget and is realized, issues an Xlib XMoveWindow call on the widget's window. To resize a sibling widget of the child making the geometry request, the parent uses XtResizeWidget. __ | void XtResizeWidget(w, width, height, border_width) Widget w; Dimension width; Dimension height; Dimension border_width; w Specifies the widget. Must be of class RectObj or any subclass thereof. width height border_width Specify the new widget size. |__ The XtResizeWidget function returns immediately if the spec- ified geometry fields are the same as the old values. Oth- erwise, XtResizeWidget writes the new width, height, and border_width values into the object and, if the object is a widget and is realized, issues an XConfigureWindow call on the widget's window. If the new width or height is different from the old values, XtResizeWidget calls the object's resize procedure to notify it of the size change. 151 X Toolkit Intrinsics X11 Release 6.4 To move and resize the sibling widget of the child making the geometry request, the parent uses XtConfigureWidget. __ | void XtConfigureWidget(w, x, y, width, height, border_width) Widget w; Position x; Position y; Dimension width; Dimension height; Dimension border_width; w Specifies the widget. Must be of class RectObj or any subclass thereof. x y Specify the new widget x and y coordinates. width height border_width Specify the new widget size. |__ The XtConfigureWidget function returns immediately if the specified new geometry fields are all equal to the current values. Otherwise, XtConfigureWidget writes the new x, y, width, height, and border_width values into the object and, if the object is a widget and is realized, makes an Xlib XConfigureWindow call on the widget's window. If the new width or height is different from its old value, XtConfigureWidget calls the object's resize procedure to notify it of the size change; otherwise, it simply returns. To resize a child widget that already has the new values of its width, height, and border width, the parent uses XtRe- sizeWindow. __ | void XtResizeWindow(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ The XtResizeWindow function calls the XConfigureWindow Xlib function to make the window of the specified widget match 152 X Toolkit Intrinsics X11 Release 6.4 its width, height, and border width. This request is done unconditionally because there is no inexpensive way to tell if these values match the current values. Note that the widget's resize procedure is not called. There are very few times to use XtResizeWindow; instead, the parent should use XtResizeWidget. 6.7. Preferred Geometry Some parents may be willing to adjust their layouts to accommodate the preferred geometries of their children. They can use XtQueryGeometry to obtain the preferred geome- try and, as they see fit, can use or ignore any portion of the response. To query a child widget's preferred geometry, use XtQuery- Geometry. __ | XtGeometryResult XtQueryGeometry(w, intended, preferred_return) Widget w; XtWidgetGeometry *intended; XtWidgetGeometry *preferred_return; w Specifies the widget. Must be of class RectObj or any subclass thereof. intended Specifies the new geometry the parent plans to give to the child, or NULL. preferred_return Returns the child widget's preferred geometry. |__ To discover a child's preferred geometry, the child's parent stores the new geometry in the corresponding fields of the intended structure, sets the corresponding bits in intended.request_mode, and calls XtQueryGeometry. The par- ent should set only those fields that are important to it so that the child can determine whether it may be able to attempt changes to other fields. XtQueryGeometry clears all bits in the pre- ferred_return->request_mode field and checks the query_geom- etry field of the specified widget's class record. If query_geometry is not NULL, XtQueryGeometry calls the query_geometry procedure and passes as arguments the speci- fied widget, intended, and preferred_return structures. If the intended argument is NULL, XtQueryGeometry replaces it 153 X Toolkit Intrinsics X11 Release 6.4 with a pointer to an XtWidgetGeometry structure with request_mode equal to zero before calling the query_geometry procedure. Note If XtQueryGeometry is called from within a geome- try_manager procedure for the widget that issued XtMakeGeometryRequest or XtMakeResizeRequest, the results are not guaranteed to be consistent with the requested changes. The change request passed to the geometry manager takes precedence over the preferred geometry. The query_geometry procedure pointer is of type XtGeometry- Handler. __ | typedef XtGeometryResult (*XtGeometryHandler)(Widget, XtWidgetGeometry*, XtWidgetGeometry*); Widget w; XtWidgetGeometry *request; XtWidgetGeometry *preferred_return; w Passes the child widget whose preferred geometry is required. request Passes the geometry changes that the parent plans to make. preferred_return Passes a structure in which the child returns its preferred geometry. |__ The query_geometry procedure is expected to examine the bits set in request->request_mode, evaluate the preferred geome- try of the widget, and store the result in preferred_return (setting the bits in preferred_return->request_mode corre- sponding to those geometry fields that it cares about). If the proposed geometry change is acceptable without modifica- tion, the query_geometry procedure should return XtGeome- tryYes. If at least one field in preferred_return with a bit set in preferred_return->request_mode is different from the corresponding field in request or if a bit was set in preferred_return->request_mode that was not set in the request, the query_geometry procedure should return XtGeome- tryAlmost. If the preferred geometry is identical to the current geometry, the query_geometry procedure should return XtGeometryNo. 154 X Toolkit Intrinsics X11 Release 6.4 Note The query_geometry procedure may assume that no XtMakeResizeRequest or XtMakeGeometryRequest is in progress for the specified widget; that is, it is not required to construct a reply consistent with the requested geometry if such a request were actually outstanding. After calling the query_geometry procedure or if the query_geometry field is NULL, XtQueryGeometry examines all the unset bits in preferred_return->request_mode and sets the corresponding fields in preferred_return to the current values from the widget instance. If CWStackMode is not set, the stack_mode field is set to XtSMDontChange. XtQuery- Geometry returns the value returned by the query_geometry procedure or XtGeometryYes if the query_geometry field is NULL. Therefore, the caller can interpret a return of XtGeome- tryYes as not needing to evaluate the contents of the reply and, more important, not needing to modify its layout plans. A return of XtGeometryAlmost means either that both the par- ent and the child expressed interest in at least one common field and the child's preference does not match the parent's intentions or that the child expressed interest in a field that the parent might need to consider. A return value of XtGeometryNo means that both the parent and the child expressed interest in a field and that the child suggests that the field's current value in the widget instance is its preferred value. In addition, whether or not the caller ignores the return value or the reply mask, it is guaranteed that the preferred_return structure contains complete geome- try information for the child. Parents are expected to call XtQueryGeometry in their layout routine and wherever else the information is significant after change_managed has been called. The first time it is invoked, the changed_managed procedure may assume that the child's current geometry is its preferred geometry. Thus, the child is still responsible for storing values into its own geometry during its initialize procedure. 6.8. Size Change Management: The resize Procedure A child can be resized by its parent at any time. Widgets usually need to know when they have changed size so that they can lay out their displayed data again to match the new size. When a parent resizes a child, it calls XtResizeWid- get, which updates the geometry fields in the widget, con- figures the window if the widget is realized, and calls the child's resize procedure to notify the child. The resize 155 X Toolkit Intrinsics X11 Release 6.4 procedure pointer is of type XtWidgetProc. If a class need not recalculate anything when a widget is resized, it can specify NULL for the resize field in its class record. This is an unusual case and should occur only for widgets with very trivial display semantics. The resize procedure takes a widget as its only argument. The x, y, width, height, and border_width fields of the widget contain the new values. The resize procedure should recalculate the layout of internal data as needed. (For example, a centered Label in a window that changes size should recalculate the starting position of the text.) The widget must obey resize as a command and must not treat it as a request. A widget must not issue an XtMakeGeometryRequest or XtMakeResiz- eRequest call from its resize procedure. 156 X Toolkit Intrinsics X11 Release 6.4 Chapter 7 Event Management While Xlib allows the reading and processing of events any- where in an application, widgets in the X Toolkit neither directly read events nor grab the server or pointer. Wid- gets register procedures that are to be called when an event or class of events occurs in that widget. A typical application consists of startup code followed by an event loop that reads events and dispatches them by call- ing the procedures that widgets have registered. The default event loop provided by the Intrinsics is XtAppMain- Loop. The event manager is a collection of functions to perform the following tasks: o Add or remove event sources other than X server events (in particular, timer interrupts, file input, or POSIX signals). o Query the status of event sources. o Add or remove procedures to be called when an event occurs for a particular widget. o Enable and disable the dispatching of user-initiated events (keyboard and pointer events) for a particular widget. o Constrain the dispatching of events to a cascade of pop-up widgets. o Register procedures to be called when specific events arrive. o Register procedures to be called when the Intrinsics will block. o Enable safe operation in a multi-threaded environment. Most widgets do not need to call any of the event handler functions explicitly. The normal interface to X events is through the higher-level translation manager, which maps sequences of X events, with modifiers, into procedure calls. Applications rarely use any of the event manager routines besides XtAppMainLoop. 157 X Toolkit Intrinsics X11 Release 6.4 7.1. Adding and Deleting Additional Event Sources While most applications are driven only by X events, some applications need to incorporate other sources of input into the Intrinsics event-handling mechanism. The event manager provides routines to integrate notification of timer events and file data pending into this mechanism. The next section describes functions that provide input gathering from files. The application registers the files with the Intrinsics read routine. When input is pending on one of the files, the registered callback procedures are invoked. 7.1.1. Adding and Removing Input Sources To register a new file as an input source for a given appli- cation context, use XtAppAddInput. __ | XtInputId XtAppAddInput(app_context, source, condition, proc, client_data) XtAppContext app_context; int source; XtPointer condition; XtInputCallbackProc proc; XtPointer client_data; app_context Specifies the application context that identifies the application. source Specifies the source file descriptor on a POSIX- based system or other operating-system-dependent device specification. condition Specifies the mask that indicates a read, write, or exception condition or some other operating- system-dependent condition. proc Specifies the procedure to be called when the con- dition is found. client_data Specifies an argument passed to the specified pro- cedure when it is called. |__ The XtAppAddInput function registers with the Intrinsics read routine a new source of events, which is usually file input but can also be file output. Note that file should be loosely interpreted to mean any sink or source of data. 158 X Toolkit Intrinsics X11 Release 6.4 XtAppAddInput also specifies the conditions under which the source can generate events. When an event is pending on this source, the callback procedure is called. The legal values for the condition argument are operating- system-dependent. On a POSIX-based system, source is a file number and the condition is some union of the following: XtInputReadMask Specifies that proc is to be called when source has data to be read. XtInputWriteMask Specifies that proc is to be called when source is ready for writing. XtInputExceptMask Specifies that proc is to be called when source has exception data. Callback procedure pointers used to handle file events are of type XtInputCallbackProc. __ | typedef void (*XtInputCallbackProc)(XtPointer, int*, XtInputId*); XtPointer client_data; int *source; XtInputId *id; client_data Passes the client data argument that was regis- tered for this procedure in XtAppAddInput. source Passes the source file descriptor generating the event. id Passes the id returned from the corresponding XtAppAddInput call. |__ See Section 7.12 for information regarding the use of XtAp- pAddInput in multiple threads. To discontinue a source of input, use XtRemoveInput. 159 X Toolkit Intrinsics X11 Release 6.4 __ | void XtRemoveInput(id) XtInputId id; id Specifies the id returned from the corresponding XtAppAddInput call. |__ The XtRemoveInput function causes the Intrinsics read rou- tine to stop watching for events from the file source speci- fied by id. See Section 7.12 for information regarding the use of XtRemoveInput in multiple threads. 7.1.2. Adding and Removing Blocking Notifications Occasionally it is desirable for an application to receive notification when the Intrinsics event manager detects no pending input from file sources and no pending input from X server event sources and is about to block in an operating system call. To register a hook that is called immediately prior to event blocking, use XtAppAddBlockHook. __ | XtBlockHookId XtAppAddBlockHook(app_context, proc, client_data) XtAppContext app_context; XtBlockHookProc proc; XtPointer client_data; app_context Specifies the application context that identifies the application. proc Specifies the procedure to be called before block- ing. client_data Specifies an argument passed to the specified pro- cedure when it is called. |__ The XtAppAddBlockHook function registers the specified pro- cedure and returns an identifier for it. The hook procedure proc is called at any time in the future when the Intrinsics are about to block pending some input. 160 X Toolkit Intrinsics X11 Release 6.4 The procedure pointers used to provide notification of event blocking are of type XtBlockHookProc. __ | typedef void (*XtBlockHookProc)(XtPointer); XtPointer client_data; client_data Passes the client data argument that was regis- tered for this procedure in XtAppAddBlockHook. |__ To discontinue the use of a procedure for blocking notifica- tion, use XtRemoveBlockHook. __ | void XtRemoveBlockHook(id) XtBlockHookId id; id Specifies the identifier returned from the corre- sponding call to XtAppAddBlockHook. |__ The XtRemoveBlockHook function removes the specified proce- dure from the list of procedures that are called by the Intrinsics read routine before blocking on event sources. 7.1.3. Adding and Removing Timeouts The timeout facility notifies the application or the widget through a callback procedure that a specified time interval has elapsed. Timeout values are uniquely identified by an interval id. To register a timeout callback, use XtAppAddTimeOut. 161 X Toolkit Intrinsics X11 Release 6.4 __ | XtIntervalId XtAppAddTimeOut(app_context, interval, proc, client_data) XtAppContext app_context; unsigned long interval; XtTimerCallbackProc proc; XtPointer client_data; app_context Specifies the application context for which the timer is to be set. interval Specifies the time interval in milliseconds. proc Specifies the procedure to be called when the time expires. client_data Specifies an argument passed to the specified pro- cedure when it is called. |__ The XtAppAddTimeOut function creates a timeout and returns an identifier for it. The timeout value is set to interval. The callback procedure proc is called when XtAppNextEvent or XtAppProcessEvent is next called after the time interval elapses, and then the timeout is removed. Callback procedure pointers used with timeouts are of type XtTimerCallbackProc. __ | typedef void (*XtTimerCallbackProc)(XtPointer, XtIntervalId*); XtPointer client_data; XtIntervalId *timer; client_data Passes the client data argument that was regis- tered for this procedure in XtAppAddTimeOut. timer Passes the id returned from the corresponding XtAppAddTimeOut call. |__ See Section 7.12 for information regarding the use of XtAp- pAddTimeOut in multiple threads. To clear a timeout value, use XtRemoveTimeOut. 162 X Toolkit Intrinsics X11 Release 6.4 __ | void XtRemoveTimeOut(timer) XtIntervalId timer; timer Specifies the id for the timeout request to be cleared. |__ The XtRemoveTimeOut function removes the pending timeout. Note that timeouts are automatically removed once they trig- ger. Please refer to Section 7.12 for information regarding the use of XtRemoveTimeOut in multiple threads. 7.1.4. Adding and Removing Signal Callbacks The signal facility notifies the application or the widget through a callback procedure that a signal or other external asynchronous event has occurred. The registered callback procedures are uniquely identified by a signal id. Prior to establishing a signal handler, the application or widget should call XtAppAddSignal and store the resulting identifier in a place accessible to the signal handler. When a signal arrives, the signal handler should call XtNo- ticeSignal to notify the Intrinsics that a signal has occured. To register a signal callback use XtAppAddSignal. __ | XtSignalId XtAppAddSignal(app_context, proc, client_data) XtAppContext app_context; XtSignalCallbackProc proc; XtPointer client_data; app_context Specifies the application context that identifies the application. proc Specifies the procedure to be called when the sig- nal is noticed. client_data Specifies an argument passed to the specified pro- cedure when it is called. |__ The callback procedure pointers used to handle signal events are of type XtSignalCallbackProc. 163 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtSignalCallbackProc)(XtPointer, XtSignalId*); XtPointer client_data; XtSignalId *id; client_data Passes the client data argument that was regis- tered for this procedure in XtAppAddSignal. id Passes the id returned from the corresponding XtAppAddSignal call. |__ To notify the Intrinsics that a signal has occured, use XtNoticeSignal. __ | void XtNoticeSignal(id) XtSignalId id; id Specifies the id returned from the corresponding XtAppAddSignal call. |__ On a POSIX-based system, XtNoticeSignal is the only Intrin- sics function that can safely be called from a signal han- dler. If XtNoticeSignal is invoked multiple times before the Intrinsics are able to invoke the registered callback, the callback is only called once. Logically, the Intrinsics maintain ``pending'' flag for each registered callback. This flag is initially False and is set to True by XtNo- ticeSignal. When XtAppNextEvent or XtAppProcessEvent (with a mask including XtIMSignal) is called, all registered call- backs with ``pending'' True are invoked and the flags are reset to False. If the signal handler wants to track how many times the sig- nal has been raised, it can keep its own private counter. Typically the handler would not do any other work; the call- back does the actual processing for the signal. The Intrin- sics never block signals from being raised, so if a given signal can be raised multiple times before the Intrinsics can invoke the callback for that signal, the callback must be designed to deal with this. In another case, a signal might be raised just after the Intrinsics sets the pending flag to False but before the callback can get control, in which case the pending flag will still be True after the callback returns, and the Intrinsics will invoke the call- back again, even though all of the signal raises have been handled. The callback must also be prepared to handle this 164 X Toolkit Intrinsics X11 Release 6.4 case. To remove a registered signal callback, call XtRemoveSignal. __ | void XtRemoveSignal(id) XtSignalId id; id Specifies the id returned by the corresponding call to XtAppAddSignal. |__ The client should typically disable the source of the signal before calling XtRemoveSignal. If the signal could have been raised again before the source was disabled and the client wants to process it, then after disabling the source but before calling XtRemoveSignal the client can test for signals with XtAppPending and process them by calling XtApp- ProcessEvent with the mask XtIMSignal. 7.2. Constraining Events to a Cascade of Widgets Modal widgets are widgets that, except for the input directed to them, lock out user input to the application. When a modal menu or modal dialog box is popped up using XtPopup, user events (keyboard and pointer events) that occur outside the modal widget should be delivered to the modal widget or ignored. In no case will user events be delivered to a widget outside the modal widget. Menus can pop up submenus, and dialog boxes can pop up fur- ther dialog boxes to create a pop-up cascade. In this case, user events may be delivered to one of several modal widgets in the cascade. Display-related events should be delivered outside the modal cascade so that exposure events and the like keep the appli- cation's display up-to-date. Any event that occurs within the cascade is delivered as usual. The user events deliv- ered to the most recent spring-loaded shell in the cascade when they occur outside the cascade are called remap events and are KeyPress, KeyRelease, ButtonPress, and ButtonRe- lease. The user events ignored when they occur outside the cascade are MotionNotify and EnterNotify. All other events are delivered normally. In particular, note that this is one way in which widgets can receive LeaveNotify events without first receiving EnterNotify events; they should be prepared to deal with this, typically by ignoring any unmatched LeaveNotify events. 165 X Toolkit Intrinsics X11 Release 6.4 XtPopup uses the XtAddGrab and XtRemoveGrab functions to constrain user events to a modal cascade and subsequently to remove a grab when the modal widget is popped down. To constrain or redirect user input to a modal widget, use XtAddGrab. __ | void XtAddGrab(w, exclusive, spring_loaded) Widget w; Boolean exclusive; Boolean spring_loaded; w Specifies the widget to add to the modal cascade. Must be of class Core or any subclass thereof. exclusive Specifies whether user events should be dispatched exclusively to this widget or also to previous widgets in the cascade. spring_loaded Specifies whether this widget was popped up because the user pressed a pointer button. |__ The XtAddGrab function appends the widget to the modal cas- cade and checks that exclusive is True if spring_loaded is True. If this condition is not met, XtAddGrab generates a warning message. The modal cascade is used by XtDispatchEvent when it tries to dispatch a user event. When at least one modal widget is in the widget cascade, XtDispatchEvent first determines if the event should be delivered. It starts at the most recent cascade entry and follows the cascade up to and including the most recent cascade entry added with the exclusive parameter True. This subset of the modal cascade along with all descendants of these widgets comprise the active subset. User events that occur outside the widgets in this subset are ignored or remapped. Modal menus with submenus generally add a submenu widget to the cascade with exclusive False. Modal dialog boxes that need to restrict user input to the most deeply nested dialog box add a subdialog widget to the cascade with exclusive True. User events that occur within the active subset are delivered to the appropriate widget, which is usually a child or further descendant of the modal widget. 166 X Toolkit Intrinsics X11 Release 6.4 Regardless of where in the application they occur, remap events are always delivered to the most recent widget in the active subset of the cascade registered with spring_loaded True, if any such widget exists. If the event occurred in the active subset of the cascade but outside the spring- loaded widget, it is delivered normally before being deliv- ered also to the spring-loaded widget. Regardless of where it is dispatched, the Intrinsics do not modify the contents of the event. To remove the redirection of user input to a modal widget, use XtRemoveGrab. __ | void XtRemoveGrab(w) Widget w; w Specifies the widget to remove from the modal cas- cade. |__ The XtRemoveGrab function removes widgets from the modal cascade starting at the most recent widget up to and includ- ing the specified widget. It issues a warning if the speci- fied widget is not on the modal cascade. 7.2.1. Requesting Key and Button Grabs The Intrinsics provide a set of key and button grab inter- faces that are parallel to those provided by Xlib and that allow the Intrinsics to modify event dispatching when neces- sary. X Toolkit applications and widgets that need to pas- sively grab keys or buttons or actively grab the keyboard or pointer should use the following Intrinsics routines rather than the corresponding Xlib routines. To passively grab a single key of the keyboard, use XtGrabKey. 167 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGrabKey(widget, keycode, modifiers, owner_events, pointer_mode, keyboard_mode) Widget widget; KeyCode keycode; Modifiers modifiers; Boolean owner_events; int pointer_mode, keyboard_mode; widget Specifies the widget in whose window the key is to be grabbed. Must be of class Core or any subclass thereof. keycode modifiers owner_events pointer_mode keyboard_mode Specify arguments to XGrabKey; see Section 12.2 in Xlib -- C Language X Interface. |__ XtGrabKey calls XGrabKey specifying the widget's window as the grab window if the widget is realized. The remaining arguments are exactly as for XGrabKey. If the widget is not realized, or is later unrealized, the call to XGrabKey is performed (again) when the widget is realized and its window becomes mapped. In the future, if XtDispatchEvent is called with a KeyPress event matching the specified keycode and modifiers (which may be AnyKey or AnyModifier, respectively) for the widget's window, the Intrinsics will call XtUn- grabKeyboard with the timestamp from the KeyPress event if either of the following conditions is true: o There is a modal cascade and the widget is not in the active subset of the cascade and the keyboard was not previously grabbed, or o XFilterEvent returns True. To cancel a passive key grab, use XtUngrabKey. 168 X Toolkit Intrinsics X11 Release 6.4 __ | void XtUngrabKey(widget, keycode, modifiers) Widget widget; KeyCode keycode; Modifiers modifiers; widget Specifies the widget in whose window the key was grabbed. keycode modifiers Specify arguments to XUngrabKey; see Section 12.2 in Xlib -- C Language X Interface. |__ The XtUngrabKey procedure calls XUngrabKey specifying the widget's window as the ungrab window if the widget is real- ized. The remaining arguments are exactly as for XUn- grabKey. If the widget is not realized, XtUngrabKey removes a deferred XtGrabKey request, if any, for the specified wid- get, keycode, and modifiers. To actively grab the keyboard, use XtGrabKeyboard. __ | int XtGrabKeyboard(widget, owner_events, pointer_mode, keyboard_mode, time) Widget widget; Boolean owner_events; int pointer_mode, keyboard_mode; Time time; widget Specifies the widget for whose window the keyboard is to be grabbed. Must be of class Core or any subclass thereof. owner_events pointer_mode keyboard_mode time Specify arguments to XGrabKeyboard; see Section 12.2 in Xlib -- C Language X Interface. |__ If the specified widget is realized, XtGrabKeyboard calls XGrabKeyboard specifying the widget's window as the grab window. The remaining arguments and return value are exactly as for XGrabKeyboard. If the widget is not real- ized, XtGrabKeyboard immediately returns GrabNotViewable. No future automatic ungrab is implied by XtGrabKeyboard. 169 X Toolkit Intrinsics X11 Release 6.4 To cancel an active keyboard grab, use XtUngrabKeyboard. __ | void XtUngrabKeyboard(widget, time) Widget widget; Time time; widget Specifies the widget that has the active keyboard grab. time Specifies the additional argument to XUngrabKey- board; see Section 12.2 in Xlib -- C Language X Interface. |__ XtUngrabKeyboard calls XUngrabKeyboard with the specified time. To passively grab a single pointer button, use XtGrabButton. __ | void XtGrabButton(widget, button, modifiers, owner_events, event_mask, pointer_mode, keyboard_mode, confine_to, cursor) Widget widget; int button; Modifiers modifiers; Boolean owner_events; unsigned int event_mask; int pointer_mode, keyboard_mode; Window confine_to; Cursor cursor; widget Specifies the widget in whose window the button is to be grabbed. Must be of class Core or any sub- class thereof. button modifiers owner_events event_mask pointer_mode keyboard_mode confine_to cursor Specify arguments to XGrabButton; see Section 12.1 in Xlib -- C Language X Interface. |__ XtGrabButton calls XGrabButton specifying the widget's win- dow as the grab window if the widget is realized. The 170 X Toolkit Intrinsics X11 Release 6.4 remaining arguments are exactly as for XGrabButton. If the widget is not realized, or is later unrealized, the call to XGrabButton is performed (again) when the widget is realized and its window becomes mapped. In the future, if XtDis- patchEvent is called with a ButtonPress event matching the specified button and modifiers (which may be AnyButton or AnyModifier, respectively) for the widget's window, the Intrinsics will call XtUngrabPointer with the timestamp from the ButtonPress event if either of the following conditions is true: o There is a modal cascade and the widget is not in the active subset of the cascade and the pointer was not pre- viously grabbed, or o XFilterEvent returns True. To cancel a passive button grab, use XtUngrabButton. __ | void XtUngrabButton(widget, button, modifiers) Widget widget; unsigned int button; Modifiers modifiers; widget Specifies the widget in whose window the button was grabbed. button modifiers Specify arguments to XUngrabButton; see Section 12.1 in Xlib -- C Language X Interface. |__ The XtUngrabButton procedure calls XUngrabButton specifying the widget's window as the ungrab window if the widget is realized. The remaining arguments are exactly as for XUn- grabButton. If the widget is not realized, XtUngrabButton removes a deferred XtGrabButton request, if any, for the specified widget, button, and modifiers. To actively grab the pointer, use XtGrabPointer. 171 X Toolkit Intrinsics X11 Release 6.4 __ | int XtGrabPointer(widget, owner_events, event_mask, pointer_mode, keyboard_mode, confine_to, cursor, time) Widget widget; Boolean owner_events; unsigned int event_mask; int pointer_mode, keyboard_mode; Window confine_to; Cursor cursor; Time time; widget Specifies the widget for whose window the pointer is to be grabbed. Must be of class Core or any subclass thereof. owner_events event_mask pointer_mode keyboard_mode confine_to cursor time Specify arguments to XGrabPointer; see Section 12.1 in Xlib -- C Language X Interface. |__ If the specified widget is realized, XtGrabPointer calls XGrabPointer, specifying the widget's window as the grab window. The remaining arguments and return value are exactly as for XGrabPointer. If the widget is not realized, XtGrabPointer immediately returns GrabNotViewable. No future automatic ungrab is implied by XtGrabPointer. To cancel an active pointer grab, use XtUngrabPointer. __ | void XtUngrabPointer(widget, time) Widget widget; Time time; widget Specifies the widget that has the active pointer grab. time Specifies the time argument to XUngrabPointer; see Section 12.1 in Xlib -- C Language X Interface. |__ XtUngrabPointer calls XUngrabPointer with the specified time. 172 X Toolkit Intrinsics X11 Release 6.4 7.3. Focusing Events on a Child To redirect keyboard input to a normal descendant of a wid- get without calling XSetInputFocus, use XtSetKeyboardFocus. __ | void XtSetKeyboardFocus(subtree descendant) Widget subtree, descendant; subtree Specifies the subtree of the hierarchy for which the keyboard focus is to be set. Must be of class Core or any subclass thereof. descendant Specifies either the normal (non-pop-up) descen- dant of subtree to which keyboard events are logi- cally directed, or None. It is not an error to specify None when no input focus was previously set. Must be of class Object or any subclass thereof. |__ XtSetKeyboardFocus causes XtDispatchEvent to remap keyboard events occurring within the specified subtree and dispatch them to the specified descendant widget or to an ancestor. If the descendant's class is not a subclass of Core, the descendant is replaced by its closest windowed ancestor. When there is no modal cascade, keyboard events can be dis- patched to a widget in one of five ways. Assume the server delivered the event to the window for widget E (because of X input focus, key or keyboard grabs, or pointer position). o If neither E nor any of E's ancestors have redirected the keyboard focus, or if the event activated a grab for E as specified by a call to XtGrabKey with any value of owner_events, or if the keyboard is actively grabbed by E with owner_events False via XtGrabKeyboard or XtGrabKey on a previous key press, the event is dispatched to E. o Beginning with the ancestor of E closest to the root that has redirected the keyboard focus or E if no such ances- tor exists, if the target of that focus redirection has in turn redirected the keyboard focus, recursively follow this focus chain to find a widget F that has not redi- rected focus. - If E is the final focus target widget F or a descen- dant of F, the event is dispatched to E. - If E is not F, an ancestor of F, or a descendant of F, and the event activated a grab for E as specified by a 173 X Toolkit Intrinsics X11 Release 6.4 call to XtGrabKey for E, XtUngrabKeyboard is called. - If E is an ancestor of F, and the event is a key press, and either + E has grabbed the key with XtGrabKey and owner_events False, or + E has grabbed the key with XtGrabKey and owner_events True, and the coordinates of the event are outside the rectangle specified by E's geome- try, then the event is dispatched to E. - Otherwise, define A as the closest common ancestor of E and F: + If there is an active keyboard grab for any widget via either XtGrabKeyboard or XtGrabKey on a previ- ous key press, or if no widget between F and A (noninclusive) has grabbed the key and modifier combination with XtGrabKey and any value of owner_events, the event is dispatched to F. + Else, the event is dispatched to the ancestor of F closest to A that has grabbed the key and modifier combination with XtGrabKey. When there is a modal cascade, if the final destination wid- get as identified above is in the active subset of the cas- cade, the event is dispatched; otherwise the event is remapped to a spring-loaded shell or discarded. Regardless of where it is dispatched, the Intrinsics do not modify the contents of the event. When subtree or one of its descendants acquires the X input focus or the pointer moves into the subtree such that key- board events would now be delivered to the subtree, a FocusIn event is generated for the descendant if FocusChange events have been selected by the descendant. Similarly, when subtree loses the X input focus or the keyboard focus for one of its ancestors, a FocusOut event is generated for descendant if FocusChange events have been selected by the descendant. A widget tree may also actively manage the X server input focus. To do so, a widget class specifies an accept_focus procedure. The accept_focus procedure pointer is of type XtAcceptFocus- Proc. 174 X Toolkit Intrinsics X11 Release 6.4 __ | typedef Boolean (*XtAcceptFocusProc)(Widget, Time*); Widget w; Time *time; w Specifies the widget. time Specifies the X time of the event causing the accept focus. |__ Widgets that need the input focus can call XSetInputFocus explicitly, pursuant to the restrictions of the Inter-Client Communication Conventions Manual. To allow outside agents, such as the parent, to cause a widget to take the input focus, every widget exports an accept_focus procedure. The widget returns a value indicating whether it actually took the focus or not, so that the parent can give the focus to another widget. Widgets that need to know when they lose the input focus must use the Xlib focus notification mecha- nism explicitly (typically by specifying translations for FocusIn and FocusOut events). Widgets classes that never want the input focus should set the accept_focus field to NULL. To call a widget's accept_focus procedure, use XtCallAccept- Focus. __ | Boolean XtCallAcceptFocus(w, time) Widget w; Time *time; w Specifies the widget. Must be of class Core or any subclass thereof. time Specifies the X time of the event that is causing the focus change. |__ The XtCallAcceptFocus function calls the specified widget's accept_focus procedure, passing it the specified widget and time, and returns what the accept_focus procedure returns. If accept_focus is NULL, XtCallAcceptFocus returns False. 7.3.1. Events for Drawables That Are Not a Widget's Window Sometimes an application must handle events for drawables that are not associated with widgets in its widget tree. 175 X Toolkit Intrinsics X11 Release 6.4 Examples include handling GraphicsExpose and NoExpose events on Pixmaps, and handling PropertyNotify events on the root window. To register a drawable with the Intrinsics event dispatch- ing, use XtRegisterDrawable. __ | void XtRegisterDrawable(display, drawable, widget) Display *display; Drawable drawable; Widget widget; display Specifies the drawable's display. drawable Specifies the drawable to register. widget Specifies the widget to register the drawable for. |__ XtRegisterDrawable associates the specified drawable with the specified widget so that future calls to XtWindowToWid- get with the drawable will return the widget. The default event dispatcher will dispatch future events that arrive for the drawable to the widget in the same manner as events that contain the widget's window. If the drawable is already registered with another widget, or if the drawable is the window of a widget in the client's widget tree, the results of calling XtRegisterDrawable are undefined. To unregister a drawable with the Intrinsics event dispatch- ing, use XtUnregisterDrawable. __ | void XtUnregisterDrawable(display, drawable) Display *display; Drawable drawable; display Specifies the drawable's display. drawable Specifies the drawable to unregister. |__ XtUnregisterDrawable removes an association created with XtRegisterDrawable. If the drawable is the window of a wid- get in the client's widget tree the results of calling XtUn- registerDrawable are undefined. 176 X Toolkit Intrinsics X11 Release 6.4 7.4. Querying Event Sources The event manager provides several functions to examine and read events (including file and timer events) that are in the queue. The next three functions are Intrinsics equiva- lents of the XPending, XPeekEvent, and XNextEvent Xlib calls. To determine if there are any events on the input queue for a given application, use XtAppPending. __ | XtInputMask XtAppPending(app_context) XtAppContext app_context; app_context Specifies the application context that identifies the application to check. |__ The XtAppPending function returns a nonzero value if there are events pending from the X server, timer pending, other input sources pending, or signal sources pending. The value returned is a bit mask that is the OR of XtIMXEvent, XtIM- Timer, XtIMAlternateInput, and XtIMSignal (see XtAppProces- sEvent). If there are no events pending, XtAppPending flushes the output buffers of each Display in the applica- tion context and returns zero. To return the event from the head of a given application's input queue without removing input from the queue, use XtAppPeekEvent. __ | Boolean XtAppPeekEvent(app_context, event_return) XtAppContext app_context; XEvent *event_return; app_context Specifies the application context that identifies the application. event_return Returns the event information to the specified event structure. |__ If there is an X event in the queue, XtAppPeekEvent copies 177 X Toolkit Intrinsics X11 Release 6.4 it into event_return and returns True. If no X input is on the queue, XtAppPeekEvent flushes the output buffers of each Display in the application context and blocks until some input is available (possibly calling some timeout callbacks in the interim). If the next available input is an X event, XtAppPeekEvent fills in event_return and returns True. Oth- erwise, the input is for an input source registered with XtAppAddInput, and XtAppPeekEvent returns False. To remove and return the event from the head of a given application's X event queue, use XtAppNextEvent. __ | void XtAppNextEvent(app_context, event_return) XtAppContext app_context; XEvent *event_return; app_context Specifies the application context that identifies the application. event_return Returns the event information to the specified event structure. |__ If the X event queue is empty, XtAppNextEvent flushes the X output buffers of each Display in the application context and waits for an X event while looking at the other input sources and timeout values and calling any callback proce- dures triggered by them. This wait time can be used for background processing; see Section 7.8. 7.5. Dispatching Events The Intrinsics provide functions that dispatch events to widgets or other application code. Every client interested in X events on a widget uses XtAddEventHandler to register which events it is interested in and a procedure (event han- dler) to be called when the event happens in that window. The translation manager automatically registers event han- dlers for widgets that use translation tables; see Chapter 10. ----------- The sample implementations provides XtAppPeekEvent as described. Timeout callbacks are called while blocking for input. If some input for an input source is available, XtAppPeekEvent will return True without returning an event. 178 X Toolkit Intrinsics X11 Release 6.4 Applications that need direct control of the processing of different types of input should use XtAppProcessEvent. __ | void XtAppProcessEvent(app_context, mask) XtAppContext app_context; XtInputMask mask; app_context Specifies the application context that identifies the application for which to process input. mask Specifies what types of events to process. The mask is the bitwise inclusive OR of any combina- tion of XtIMXEvent, XtIMTimer, XtIMAlternateInput, and XtIMSignal. As a convenience, Intrinsic.h defines the symbolic name XtIMAll to be the bit- wise inclusive OR of these four event types. |__ The XtAppProcessEvent function processes one timer, input source, signal source, or X event. If there is no event or input of the appropriate type to process, then XtAppProces- sEvent blocks until there is. If there is more than one type of input available to process, it is undefined which will get processed. Usually, this procedure is not called by client applications; see XtAppMainLoop. XtAppProcessEv- ent processes timer events by calling any appropriate timer callbacks, input sources by calling any appropriate input callbacks, signal source by calling any appropriate signal callbacks, and X events by calling XtDispatchEvent. When an X event is received, it is passed to XtDis- patchEvent, which calls the appropriate event handlers and passes them the widget, the event, and client-specific data registered with each procedure. If no handlers for that event are registered, the event is ignored and the dis- patcher simply returns. To dispatch an event returned by XtAppNextEvent, retrieved directly from the Xlib queue, or synthetically constructed, to any registered event filters or event handlers, call XtDispatchEvent. 179 X Toolkit Intrinsics X11 Release 6.4 __ | Boolean XtDispatchEvent(event) XEvent *event; event Specifies a pointer to the event structure to be dispatched to the appropriate event handlers. |__ The XtDispatchEvent function first calls XFilterEvent with the event and the window of the widget to which the Intrin- sics intend to dispatch the event, or the event window if the Intrinsics would not dispatch the event to any handlers. If XFilterEvent returns True and the event activated a server grab as identified by a previous call to XtGrabKey or XtGrabButton, XtDispatchEvent calls XtUngrabKeyboard or XtUngrabPointer with the timestamp from the event and imme- diately returns True. If XFilterEvent returns True and a grab was not activated, XtDispatchEvent just immediately returns True. Otherwise, XtDispatchEvent sends the event to the event handler functions that have been previously regis- tered with the dispatch routine. XtDispatchEvent returns True if XFilterEvent returned True, or if the event was dis- patched to some handler, and False if it found no handler to which to dispatch the event. XtDispatchEvent records the last timestamp in any event that contains a timestamp (see XtLastTimestampProcessed), regardless of whether it was fil- tered or dispatched. If a modal cascade is active with spring_loaded True, and if the event is a remap event as defined by XtAddGrab, XtDispatchEvent may dispatch the event a second time. If it does so, XtDispatchEvent will call XFilterEvent again with the window of the spring-loaded wid- get prior to the second dispatch, and if XFilterEvent returns True, the second dispatch will not be performed. 7.6. The Application Input Loop To process all input from a given application in a continu- ous loop, use the convenience procedure XtAppMainLoop. __ | void XtAppMainLoop(app_context) XtAppContext app_context; app_context Specifies the application context that identifies the application. |__ The XtAppMainLoop function first reads the next incoming X event by calling XtAppNextEvent and then dispatches the 180 X Toolkit Intrinsics X11 Release 6.4 event to the appropriate registered procedure by calling XtDispatchEvent. This constitutes the main loop of X Toolkit applications. There is nothing special about XtApp- MainLoop; it simply calls XtAppNextEvent and then XtDis- patchEvent in a conditional loop. At the bottom of the loop, it checks to see if the specified application con- text's destroy flag is set. If the flag is set, the loop breaks. The whole loop is enclosed between a matching XtAp- pLock and XtAppUnlock. Applications can provide their own version of this loop, which tests some global termination flag or tests that the number of top-level widgets is larger than zero before cir- cling back to the call to XtAppNextEvent. 7.7. Setting and Checking the Sensitivity State of a Widget Many widgets have a mode in which they assume a different appearance (for example, are grayed out or stippled), do not respond to user events, and become dormant. When dormant, a widget is considered to be insensitive. If a widget is insensitive, the event manager does not dispatch any events to the widget with an event type of KeyPress, KeyRelease, ButtonPress, ButtonRelease, MotionNotify, Enter- Notify, LeaveNotify, FocusIn, or FocusOut. A widget can be insensitive because its sensitive field is False or because one of its ancestors is insensitive and thus the widget's ancestor_sensitive field also is False. A widget can but does not need to distinguish these two cases visually. Note Pop-up shells will have ancestor_sensitive False if the parent was insensitive when the shell was created. Since XtSetSensitive on the parent will not modify the resource of the pop-up child, clients are advised to include a resource specifi- cation of the form ``*TransientShell.ancestorSen- sitive: True'' in the application defaults resource file or to otherwise ensure that the par- ent is sensitive when creating pop-up shells. To set the sensitivity state of a widget, use XtSetSensi- tive. 181 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetSensitive(w, sensitive) Widget w; Boolean sensitive; w Specifies the widget. Must be of class RectObj or any subclass thereof. sensitive Specifies whether the widget should receive key- board, pointer, and focus events. |__ The XtSetSensitive function first calls XtSetValues on the current widget with an argument list specifying the XtNsen- sitive resource and the new value. If sensitive is False and the widget's class is a subclass of Composite, XtSetSen- sitive recursively propagates the new value down the child tree by calling XtSetValues on each child to set ances- tor_sensitive to False. If sensitive is True and the wid- get's class is a subclass of Composite and the widget's ancestor_sensitive field is True, XtSetSensitive sets the ancestor_sensitive of each child to True and then recur- sively calls XtSetValues on each normal descendant that is now sensitive to set ancestor_sensitive to True. XtSetSensitive calls XtSetValues to change the sensitive and ancestor_sensitive fields of each affected widget. There- fore, when one of these changes, the widget's set_values procedure should take whatever display actions are needed (for example, graying out or stippling the widget). XtSetSensitive maintains the invariant that, if the parent has either sensitive or ancestor_sensitive False, then all children have ancestor_sensitive False. To check the current sensitivity state of a widget, use XtIsSensitive. __ | Boolean XtIsSensitive(w) Widget w; w Specifies the object. Must be of class Object or any subclass thereof. |__ The XtIsSensitive function returns True or False to indicate whether user input events are being dispatched. If object's class is a subclass of RectObj and both sensitive and ances- tor_sensitive are True, XtIsSensitive returns True; 182 X Toolkit Intrinsics X11 Release 6.4 otherwise, it returns False. 7.8. Adding Background Work Procedures The Intrinsics have some limited support for background pro- cessing. Because most applications spend most of their time waiting for input, you can register an idle-time work proce- dure that is called when the toolkit would otherwise block in XtAppNextEvent or XtAppProcessEvent. Work procedure pointers are of type XtWorkProc. __ | typedef Boolean (*XtWorkProc)(XtPointer); XtPointer client_data; client_data Passes the client data specified when the work procedure was registered. |__ This procedure should return True when it is done to indi- cate that it should be removed. If the procedure returns False, it will remain registered and called again when the application is next idle. Work procedures should be very judicious about how much they do. If they run for more than a small part of a second, interactive feel is likely to suf- fer. To register a work procedure for a given application, use XtAppAddWorkProc. 183 X Toolkit Intrinsics X11 Release 6.4 __ | XtWorkProcId XtAppAddWorkProc(app_context, proc, client_data) XtAppContext app_context; XtWorkProc proc; XtPointer client_data; app_context Specifies the application context that identifies the application. proc Specifies the procedure to be called when the application is idle. client_data Specifies the argument passed to the specified procedure when it is called. |__ The XtAppAddWorkProc function adds the specified work proce- dure for the application identified by app_context and returns an opaque unique identifier for this work procedure. Multiple work procedures can be registered, and the most recently added one is always the one that is called. How- ever, if a work procedure adds another work procedure, the newly added one has lower priority than the current one. To remove a work procedure, either return True from the pro- cedure when it is called or use XtRemoveWorkProc outside of the procedure. __ | void XtRemoveWorkProc(id) XtWorkProcId id; id Specifies which work procedure to remove. |__ The XtRemoveWorkProc function explicitly removes the speci- fied background work procedure. 7.9. X Event Filters The event manager provides filters that can be applied to specific X events. The filters, which screen out events that are redundant or are temporarily unwanted, handle pointer motion compression, enter/leave compression, and exposure compression. 184 X Toolkit Intrinsics X11 Release 6.4 7.9.1. Pointer Motion Compression Widgets can have a hard time keeping up with a rapid stream of pointer motion events. Furthermore, they usually do not care about every motion event. To throw out redundant motion events, the widget class field compress_motion should be True. When a request for an event would return a motion event, the Intrinsics check if there are any other motion events for the same widget immediately following the current one and, if so, skip all but the last of them. 7.9.2. Enter/Leave Compression To throw out pairs of enter and leave events that have no intervening events, as can happen when the user moves the pointer across a widget without stopping in it, the widget class field compress_enterleave should be True. These enter and leave events are not delivered to the client if they are found together in the input queue. 7.9.3. Exposure Compression Many widgets prefer to process a series of exposure events as a single expose region rather than as individual rectan- gles. Widgets with complex displays might use the expose region as a clip list in a graphics context, and widgets with simple displays might ignore the region entirely and redisplay their whole window or might get the bounding box from the region and redisplay only that rectangle. In either case, these widgets do not care about getting par- tial exposure events. The compress_exposure field in the widget class structure specifies the type and number of exposure events that are dispatched to the widget's expose procedure. This field must be initialized to one of the following values: __ | #define XtExposeNoCompress ((XtEnum)False) #define XtExposeCompressSeries((XtEnum)True) #define XtExposeCompressMultiple #define XtExposeCompressMaximal |__ optionally ORed with any combination of the following flags (all with implementation-defined values): XtExposeGraphic- sExpose, XtExposeGraphicsExposeMerged, XtExposeNoExpose, and XtExposeNoRegion. 185 X Toolkit Intrinsics X11 Release 6.4 If the compress_exposure field in the widget class structure does not specify XtExposeNoCompress, the event manager calls the widget's expose procedure only once for a series of exposure events. In this case, all Expose or GraphicsExpose events are accumulated into a region. When the final event is received, the event manager replaces the rectangle in the event with the bounding box for the region and calls the widget's expose procedure, passing the modified exposure event and (unless XtExposeNoRegion is specified) the region. For more information on regions, see Section 16.5 in Xlib -- C Language X Interface.) The values have the following interpretation: XtExposeNoCompress No exposure compression is performed; every selected event is individually dispatched to the expose proce- dure with a region argument of NULL. XtExposeCompressSeries Each series of exposure events is coalesced into a sin- gle event, which is dispatched when an exposure event with count equal to zero is reached. XtExposeCompressMultiple Consecutive series of exposure events are coalesced into a single event, which is dispatched when an expo- sure event with count equal to zero is reached and either the event queue is empty or the next event is not an exposure event for the same widget. XtExposeCompressMaximal All expose series currently in the queue for the widget are coalesced into a single event without regard to intervening nonexposure events. If a partial series is in the end of the queue, the Intrinsics will block until the end of the series is received. The additional flags have the following meaning: XtExposeGraphicsExpose Specifies that GraphicsExpose events are also to be dispatched to the expose procedure. GraphicsExpose 186 X Toolkit Intrinsics X11 Release 6.4 events are compressed, if specified, in the same manner as Expose events. XtExposeGraphicsExposeMerged Specifies in the case of XtExposeCompressMultiple and XtExposeCompressMaximal that series of GraphicsExpose and Expose events are to be compressed together, with the final event type determining the type of the event passed to the expose procedure. If this flag is not set, then only series of the same event type as the event at the head of the queue are coalesced. This flag also implies XtExposeGraphicsExpose. XtExposeNoExpose Specifies that NoExpose events are also to be dis- patched to the expose procedure. NoExpose events are never coalesced with other exposure events or with each other. XtExposeNoRegion Specifies that the final region argument passed to the expose procedure is NULL. The rectangle in the event will still contain bounding box information for the entire series of compressed exposure events. This option saves processing time when the region is not needed by the widget. 7.10. Widget Exposure and Visibility Every primitive widget and some composite widgets display data on the screen by means of direct Xlib calls. Widgets cannot simply write to the screen and forget what they have done. They must keep enough state to redisplay the window or parts of it if a portion is obscured and then reexposed. 7.10.1. Redisplay of a Widget: The expose Procedure The expose procedure pointer in a widget class is of type XtExposeProc. 187 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtExposeProc)(Widget, XEvent*, Region); Widget w; XEvent *event; Region region; w Specifies the widget instance requiring redisplay. event Specifies the exposure event giving the rectangle requiring redisplay. region Specifies the union of all rectangles in this exposure sequence. |__ The redisplay of a widget upon exposure is the responsibil- ity of the expose procedure in the widget's class record. If a widget has no display semantics, it can specify NULL for the expose field. Many composite widgets serve only as containers for their children and have no expose procedure. Note If the expose procedure is NULL, XtRealizeWidget fills in a default bit gravity of NorthWestGravity before it calls the widget's realize procedure. If the widget's compress_exposure class field specifies XtExposeNoCompress or XtExposeNoRegion, or if the event type is NoExpose (see Section 7.9.3), region is NULL. If XtEx- poseNoCompress is not specified and the event type is not NoExpose, the event is the final event in the compressed series but x, y, width, and height contain the bounding box for all the compressed events. The region is created and destroyed by the Intrinsics, but the widget is permitted to modify the region contents. A small simple widget (for example, Label) can ignore the bounding box information in the event and redisplay the entire window. A more complicated widget (for example, Text) can use the bounding box information to minimize the amount of calculation and redisplay it does. A very complex widget uses the region as a clip list in a GC and ignores the event information. The expose procedure is not chained and is therefore responsible for exposure of all superclass data as well as its own. However, it often is possible to anticipate the display needs of several levels of subclassing. For example, rather than implement separate display procedures for the widgets Label, Pushbutton, and Toggle, you could write a single dis- play routine in Label that uses display state fields like 188 X Toolkit Intrinsics X11 Release 6.4 Boolean invert; Boolean highlight; Dimension highlight_width; Label would have invert and highlight always False and high- light_width zero. Pushbutton would dynamically set high- light and highlight_width, but it would leave invert always False. Finally, Toggle would dynamically set all three. In this case, the expose procedures for Pushbutton and Toggle inherit their superclass's expose procedure; see Section 1.6.10. 7.10.2. Widget Visibility Some widgets may use substantial computing resources to pro- duce the data they will display. However, this effort is wasted if the widget is not actually visible on the screen, that is, if the widget is obscured by another application or is iconified. The visible field in the core widget structure provides a hint to the widget that it need not compute display data. This field is guaranteed to be True by the time an exposure event is processed if any part of the widget is visible, but is False if the widget is fully obscured. Widgets can use or ignore the visible hint. If they ignore it, they should have visible_interest in their widget class record set False. In such cases, the visible field is ini- tialized True and never changes. If visible_interest is True, the event manager asks for VisibilityNotify events for the widget and sets visible to True on VisibilityUnobscured or VisibilityPartiallyObscured events and False on Visibili- tyFullyObscured events. 7.11. X Event Handlers Event handlers are procedures called when specified events occur in a widget. Most widgets need not use event handlers explicitly. Instead, they use the Intrinsics translation manager. Event handler procedure pointers are of the type XtEventHandler. 189 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtEventHandler)(Widget, XtPointer, XEvent*, Boolean*); Widget w; XtPointer client_data; XEvent *event; Boolean *continue_to_dispatch; w Specifies the widget for which the event arrived. client_data Specifies any client-specific information regis- tered with the event handler. event Specifies the triggering event. continue_to_dispatch Specifies whether the remaining event handlers registered for the current event should be called. |__ After receiving an event and before calling any event han- dlers, the Boolean pointed to by continue_to_dispatch is initialized to True. When an event handler is called, it may decide that further processing of the event is not desirable and may store False in this Boolean, in which case any handlers remaining to be called for the event are ignored. The circumstances under which the Intrinsics may add event handlers to a widget are currently implementation-dependent. Clients must therefore be aware that storing False into the continue_to_dispatch argument can lead to portability prob- lems. 7.11.1. Event Handlers That Select Events To register an event handler procedure with the dispatch mechanism, use XtAddEventHandler. 190 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAddEventHandler(w, event_mask, nonmaskable, proc, client_data) Widget w; EventMask event_mask; Boolean nonmaskable; XtEventHandler proc; XtPointer client_data; w Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. event_mask Specifies the event mask for which to call this procedure. nonmaskable Specifies whether this procedure should be called on the nonmaskable events (GraphicsExpose, NoEx- pose, SelectionClear, SelectionRequest, Selection- Notify, ClientMessage, and MappingNotify). proc Specifies the procedure to be called. client_data Specifies additional data to be passed to the event handler. |__ The XtAddEventHandler function registers a procedure with the dispatch mechanism that is to be called when an event that matches the mask occurs on the specified widget. Each widget has a single registered event handler list, which will contain any procedure/client_data pair exactly once regardless of the manner in which it is registered. If the procedure is already registered with the same client_data value, the specified mask augments the existing mask. If the widget is realized, XtAddEventHandler calls XSelectIn- put, if necessary. The order in which this procedure is called relative to other handlers registered for the same event is not defined. To remove a previously registered event handler, use XtRemoveEventHandler. 191 X Toolkit Intrinsics X11 Release 6.4 __ | void XtRemoveEventHandler(w, event_mask, nonmaskable, proc, client_data) Widget w; EventMask event_mask; Boolean nonmaskable; XtEventHandler proc; XtPointer client_data; w Specifies the widget for which this procedure is registered. Must be of class Core or any subclass thereof. event_mask Specifies the event mask for which to unregister this procedure. nonmaskable Specifies whether this procedure should be removed on the nonmaskable events (GraphicsExpose, NoEx- pose, SelectionClear, SelectionRequest, Selection- Notify, ClientMessage, and MappingNotify). proc Specifies the procedure to be removed. client_data Specifies the registered client data. |__ The XtRemoveEventHandler function unregisters an event han- dler registered with XtAddEventHandler or XtInsertEven- tHandler for the specified events. The request is ignored if client_data does not match the value given when the han- dler was registered. If the widget is realized and no other event handler requires the event, XtRemoveEventHandler calls XSelectInput. If the specified procedure has not been reg- istered or if it has been registered with a different value of client_data, XtRemoveEventHandler returns without report- ing an error. To stop a procedure registered with XtAddEventHandler or XtInsertEventHandler from receiving all selected events, call XtRemoveEventHandler with an event_mask of XtAllEvents and nonmaskable True. The procedure will continue to receive any events that have been specified in calls to XtAddRawEventHandler or XtInsertRawEventHandler. To register an event handler procedure that receives events before or after all previously registered event handlers, use XtInsertEventHandler. 192 X Toolkit Intrinsics X11 Release 6.4 __ | typedef enum {XtListHead, XtListTail} XtListPosition; void XtInsertEventHandler(w, event_mask, nonmaskable, proc, client_data, position) Widget w; EventMask event_mask; Boolean nonmaskable; XtEventHandler proc; XtPointer client_data; XtListPosition position; w Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. event_mask Specifies the event mask for which to call this procedure. nonmaskable Specifies whether this procedure should be called on the nonmaskable events (GraphicsExpose, NoEx- pose, SelectionClear, SelectionRequest, Selection- Notify, ClientMessage, and MappingNotify). proc Specifies the procedure to be called. client_data Specifies additional data to be passed to the client's event handler. position Specifies when the event handler is to be called relative to other previously registered handlers. |__ XtInsertEventHandler is identical to XtAddEventHandler with the additional position argument. If position is XtList- Head, the event handler is registered so that it is called before any event handlers that were previously registered for the same widget. If position is XtListTail, the event handler is registered to be called after any previously reg- istered event handlers. If the procedure is already regis- tered with the same client_data value, the specified mask augments the existing mask and the procedure is repositioned in the list. 7.11.2. Event Handlers That Do Not Select Events On occasion, clients need to register an event handler pro- cedure with the dispatch mechanism without explicitly 193 X Toolkit Intrinsics X11 Release 6.4 causing the X server to select for that event. To do this, use XtAddRawEventHandler. __ | void XtAddRawEventHandler(w, event_mask, nonmaskable, proc, client_data) Widget w; EventMask event_mask; Boolean nonmaskable; XtEventHandler proc; XtPointer client_data; w Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. event_mask Specifies the event mask for which to call this procedure. nonmaskable Specifies whether this procedure should be called on the nonmaskable events (GraphicsExpose, NoEx- pose, SelectionClear, SelectionRequest, Selection- Notify, ClientMessage, and MappingNotify). proc Specifies the procedure to be called. client_data Specifies additional data to be passed to the client's event handler. |__ The XtAddRawEventHandler function is similar to XtAddEven- tHandler except that it does not affect the widget's event mask and never causes an XSelectInput for its events. Note that the widget might already have those mask bits set because of other nonraw event handlers registered on it. If the procedure is already registered with the same client_data, the specified mask augments the existing mask. The order in which this procedure is called relative to other handlers registered for the same event is not defined. To remove a previously registered raw event handler, use XtRemoveRawEventHandler. 194 X Toolkit Intrinsics X11 Release 6.4 __ | void XtRemoveRawEventHandler(w, event_mask, nonmaskable, proc, client_data) Widget w; EventMask event_mask; Boolean nonmaskable; XtEventHandler proc; XtPointer client_data; w Specifies the widget for which this procedure is registered. Must be of class Core or any subclass thereof. event_mask Specifies the event mask for which to unregister this procedure. nonmaskable Specifies whether this procedure should be removed on the nonmaskable events (GraphicsExpose, NoEx- pose, SelectionClear, SelectionRequest, Selection- Notify, ClientMessage, and MappingNotify). proc Specifies the procedure to be registered. client_data Specifies the registered client data. |__ The XtRemoveRawEventHandler function unregisters an event handler registered with XtAddRawEventHandler or XtInsertRaw- EventHandler for the specified events without changing the window event mask. The request is ignored if client_data does not match the value given when the handler was regis- tered. If the specified procedure has not been registered or if it has been registered with a different value of client_data, XtRemoveRawEventHandler returns without report- ing an error. To stop a procedure registered with XtAddRawEventHandler or XtInsertRawEventHandler from receiving all nonselected events, call XtRemoveRawEventHandler with an event_mask of XtAllEvents and nonmaskable True. The procedure will con- tinue to receive any events that have been specified in calls to XtAddEventHandler or XtInsertEventHandler. To register an event handler procedure that receives events before or after all previously registered event handlers without selecting for the events, use XtInsertRawEven- tHandler. 195 X Toolkit Intrinsics X11 Release 6.4 __ | void XtInsertRawEventHandler(w, event_mask, nonmaskable, proc, client_data, position) Widget w; EventMask event_mask; Boolean nonmaskable; XtEventHandler proc; XtPointer client_data; XtListPosition position; w Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. event_mask Specifies the event mask for which to call this procedure. nonmaskable Specifies whether this procedure should be called on the nonmaskable events (GraphicsExpose, NoEx- pose, SelectionClear, SelectionRequest, Selection- Notify, ClientMessage, and MappingNotify). proc Specifies the procedure to be registered. client_data Specifies additional data to be passed to the client's event handler. position Specifies when the event handler is to be called relative to other previously registered handlers. |__ The XtInsertRawEventHandler function is similar to XtIn- sertEventHandler except that it does not modify the widget's event mask and never causes an XSelectInput for the speci- fied events. If the procedure is already registered with the same client_data value, the specified mask augments the existing mask and the procedure is repositioned in the list. 7.11.3. Current Event Mask To retrieve the event mask for a given widget, use XtBuildE- ventMask. 196 X Toolkit Intrinsics X11 Release 6.4 __ | EventMask XtBuildEventMask(w) Widget w; w Specifies the widget. Must be of class Core or any subclass thereof. |__ The XtBuildEventMask function returns the event mask repre- senting the logical OR of all event masks for event handlers registered on the widget with XtAddEventHandler and XtIn- sertEventHandler and all event translations, including accelerators, installed on the widget. This is the same event mask stored into the XSetWindowAttributes structure by XtRealizeWidget and sent to the server when event handlers and translations are installed or removed on the realized widget. 7.11.4. Event Handlers for X11 Protocol Extensions To register an event handler procedure with the Intrinsics dispatch mechanism according to an event type, use XtIn- sertEventTypeHandler. 197 X Toolkit Intrinsics X11 Release 6.4 __ | void XtInsertEventTypeHandler(widget, event_type, select_data, proc, client_data, position) Widget widget; int event_type; XtPointer select_data; XtEventHandler proc; XtPointer client_data; XtListPosition position; widget Specifies the widget for which this event handler is being registered. Must be of class Core or any subclass thereof. event_type Specifies the event type for which to call this event handler. select_data Specifies data used to request events of the spec- ified type from the server, or NULL. proc Specifies the event handler to be called. client_data Specifies additional data to be passed to the event handler. position Specifies when the event handler is to be called relative to other previously registered handlers. |__ XtInsertEventTypeHandler registers a procedure with the dis- patch mechanism that is to be called when an event that matches the specified event_type is dispatched to the speci- fied widget. If event_type specifies one of the core X protocol events, then select_data must be a pointer to a value of type Event- Mask, indicating the event mask to be used to select for the desired event. This event mask is included in the value returned by XtBuildEventMask. If the widget is realized, XtInsertEventTypeHandler calls XSelectInput if necessary. Specifying NULL for select_data is equivalent to specifying a pointer to an event mask containing 0. This is similar to the XtInsertRawEventHandler function. If event_type specifies an extension event type, then the semantics of the data pointed to by select_data are defined by the extension selector registered for the specified event type. In either case the Intrinsics are not required to copy the data pointed to by select_data, so the caller must ensure 198 X Toolkit Intrinsics X11 Release 6.4 that it remains valid as long as the event handler remains registered with this value of select_data. The position argument allows the client to control the order of invocation of event handlers registered for the same event type. If the client does not care about the order, it should normally specify XtListTail, which registers this event handler after any previously registered handlers for this event type. Each widget has a single registered event handler list, which will contain any procedure/client_data pair exactly once if it is registered with XtInsertEventTypeHandler, regardless of the manner in which it is registered and regardless of the value(s) of select_data. If the procedure is already registered with the same client_data value, the specified mask augments the existing mask and the procedure is repositioned in the list. To remove an event handler registered with XtInsertEvent- TypeHandler, use XtRemoveEventTypeHandler. __ | void XtRemoveEventTypeHandler(widget, event_type, select_data, proc, client_data) Widget widget; int event_type; XtPointer select_data; XtEventHandler proc; XtPointer client_data; widget Specifies the widget for which the event handler was registered. Must be of class Core or any sub- class thereof. event_type Specifies the event type for which the handler was registered. select_data Specifies data used to deselect events of the specified type from the server, or NULL. proc Specifies the event handler to be removed. client_data Specifies the additional client data with which the procedure was registered. |__ The XtRemoveEventTypeHandler function unregisters an event handler registered with XtInsertEventTypeHandler for the 199 X Toolkit Intrinsics X11 Release 6.4 specified event type. The request is ignored if client_data does not match the value given when the handler was regis- tered. If event_type specifies one of the core X protocol events, select_data must be a pointer to a value of type Event- Mask,indicating mask to be used to deselect for the appro- priate event. If the widget is realized, XtRemoveEventType- Handler calls XSelectInput if necessary. Specifying NULL for select_data is equivalent to specifying a pointer to an event mask containing 0. This is similar to the XtRemoveR- awEventHandler function. If event_type specifies an extension event type, then the semantics of the data pointed to by select_data are defined by the extension selector registered for the specified event type. To register a procedure to select extension events for a widget, use XtRegisterExtensionSelector. __ | void XtRegisterExtensionSelector(display, min_event_type, max_event_type, proc, client_data) Display *display; int min_event_type; int max_event_type; XtExtensionSelectProc proc; XtPointer client_data; display Specifies the display for which the extension selector is to be registered. min_event_type max_event_type Specifies the range of event types for the extension. proc Specifies the extension selector procedure. client_data Specifies additional data to be passed to the extension selector. |__ The XtRegisterExtensionSelector function registers a proce- dure to arrange for the delivery of extension events to wid- gets. If min_event_type and max_event_type match the parameters to a previous call to XtRegisterExtensionSelector for the same display, then proc and client_data replace the previously 200 X Toolkit Intrinsics X11 Release 6.4 registered values. If the range specified by min_event_type and max_event_type overlaps the range of the parameters to a previous call for the same display in any other way, an error results. When a widget is realized, after the core.realize method is called, the Intrinsics check to see if any event handler specifies an event type within the range of a registered extension selector. If so, the Intrinsics call each such selector. If an event type handler is added or removed, the Intrinsics check to see if the event type falls within the range of a registered extension selector, and if it does, calls the selector. In either case the Intrinsics pass a list of all the widget's event types that are within the selector's range. The corresponding select data are also passed. The selector is responsible for enabling the deliv- ery of extension events required by the widget. An extension selector is of type XtExtensionSelectProc. __ | typedef void (*XtExtensionSelectProc)(Widget, int *, XtPointer *, int, XtPointer); Widget widget; int *event_types; XtPointer *select_data; int count; XtPointer client_data; widget Specifies the widget that is being realized or is having an event handler added or removed. event_types Specifies a list of event types that the widget has registered event handlers for. select_data Specifies a list of the select_data parameters specified in XtInsertEventTypeHandler. count Specifies the number of entries in the event_types and select_data lists. client_data Specifies the additional client data with which the procedure was registered. |__ The event_types and select_data lists will always have the same number of elements, specified by count. Each event type/select data pair represents one call to XtInsertEvent- TypeHandler. 201 X Toolkit Intrinsics X11 Release 6.4 To register a procedure to dispatch events of a specific type within XtDispatchEvent, use XtSetEventDispatcher. __ | XtEventDispatchProc XtSetEventDispatcher(display, event_type, proc) Display *display; int event_type; XtEventDispatchProc proc; display Specifies the display for which the event dis- patcher is to be registered. event_type Specifies the event type for which the dispatcher should be invoked. proc Specifies the event dispatcher procedure. |__ The XtSetEventDispatcher function registers the event dis- patcher procedure specified by proc for events with the type event_type. The previously registered dispatcher (or the default dispatcher if there was no previously registered dispatcher) is returned. If proc is NULL, the default pro- cedure is restored for the specified type. In the future, when XtDispatchEvent is called with an event type of event_type, the specified proc (or the default dis- patcher) is invoked to determine a widget to which to dis- patch the event. The default dispatcher handles the Intrinsics modal cascade and keyboard focus mechanisms, handles the semantics of com- press_enterleave and compress_motion, and discards all extension events. An event dispatcher procedure pointer is of type XtEventDis- patchProc. __ | typedef Boolean (*XtEventDispatchProc)(XEvent*) XEvent *event; event Passes the event to be dispatched. |__ The event dispatcher procedure should determine whether this event is of a type that should be dispatched to a widget. 202 X Toolkit Intrinsics X11 Release 6.4 If the event should be dispatched to a widget, the event dispatcher procedure should determine the appropriate widget to receive the event, call XFilterEvent with the window of this widget, or None if the event is to be discarded, and if XFilterEvent returns False, dispatch the event to the widget using XtDispatchEventToWidget. The procedure should return True if either XFilterEvent or XtDispatchEventToWidget returned True and False otherwise. If the event should not be dispatched to a widget, the event dispatcher procedure should attempt to dispatch the event elsewhere as appropriate and return True if it successfully dispatched the event and False otherwise. Some dispatchers for extension events may wish to forward events according to the Intrinsics' keyboard focus mecha- nism. To determine which widget is the end result of key- board event forwarding, use XtGetKeyboardFocusWidget. __ | Widget XtGetKeyboardFocusWidget(widget) Widget widget; widget Specifies the widget to get forwarding information for. |__ The XtGetKeyboardFocusWidget function returns the widget that would be the end result of keyboard event forwarding for a keyboard event for the specified widget. To dispatch an event to a specified widget, use XtDis- patchEventToWidget. __ | Boolean XtDispatchEventToWidget(widget, event) Widget widget; XEvent *event; widget Specifies the widget to which to dispatch the event. event Specifies a pointer to the event to be dispatched. |__ The XtDispatchEventToWidget function scans the list of reg- istered event handlers for the specified widget and calls each handler that has been registered for the specified 203 X Toolkit Intrinsics X11 Release 6.4 event type, subject to the continue_to_dispatch value returned by each handler. The Intrinsics behave as if event handlers were registered at the head of the list for Expose, NoExpose, GraphicsExpose, and VisibilityNotify events to invoke the widget's expose procedure according to the expo- sure compression rules and to update the widget's visible field if visible_interest is True. These internal event handlers never set continue_to_dispatch to False. XtDispatchEventToWidget returns True if any event handler was called and False otherwise. 7.12. Using the Intrinsics in a Multi-Threaded Environment The Intrinsics may be used in environments that offer multi- ple threads of execution within the context of a single pro- cess. A multi-threaded application using the Intrinsics must explicitly initialize the toolkit for mutually exclu- sive access by calling XtToolkitThreadInitialize. 7.12.1. Initializing a Multi-Threaded Intrinsics Applica- tion To test and initialize Intrinsics support for mutually exclusive thread access, call XtToolkitThreadInitialize. __ | Boolean XtToolkitThreadInitialize() |__ XtToolkitThreadInitialize returns True if the Intrinsics support mutually exclusive thread access, otherwise it returns False. XtToolkitThreadInitialize must be called before XtCreateApplicationContext, XtAppInitialize, XtOpe- nApplication, or XtSetLanguageProc is called. XtToolkit- ThreadInitialize may be called more than once; however, the application writer must ensure that it is not called simul- taneously by two or more threads. 7.12.2. Locking X Toolkit Data Structures The Intrinsics employs two levels of locking: application context and process. Locking an application context ensures mutually exclusive access by a thread to the state associ- ated with the application context, including all displays and widgets associated with it. Locking a process ensures mutually exclusive access by a thread to Intrinsics process global data. 204 X Toolkit Intrinsics X11 Release 6.4 A client may acquire a lock multiple times and the effect is cumulative. The client must ensure that the lock is released an equal number of times in order for the lock to be acquired by another thread. Most application writers will have little need to use lock- ing as the Intrinsics performs the necessary locking inter- nally. Resource converters are an exception. They require the application context or process to be locked before the application can safely call them directly, for example: ... XtAppLock(app_context); XtCvtStringToPixel(dpy, args, num_args, fromVal, toVal, closure_ret); XtAppUnlock(app_context); ... When the application relies upon XtConvertAndStore or a con- verter to provide the storage for the results of a conver- sion, the application should acquire the process lock before calling out and hold the lock until the results have been copied. Application writers who write their own utility functions, such as one which retrieves the being_destroyed field from a widget instance, must lock the application context before accessing widget internal data. For example: #include Boolean BeingDestroyed (widget) Widget widget; { Boolean ret; XtAppLock(XtWidgetToApplicationContext(widget)); ret = widget->core.being_destroyed; XtAppUnlock(XtWidgetToApplicationContext(widget)); return ret; } A client that wishes to atomically call two or more Intrin- sics functions must lock the application context. For exam- ple: 205 X Toolkit Intrinsics X11 Release 6.4 ... XtAppLock(XtWidgetToApplicationContext(widget)); XtUnmanageChild (widget1); XtManageChild (widget2); XtAppUnlock(XtWidgetToApplicationContext(widget)); ... 7.12.2.1. Locking the Application Context To ensure mutual exclusion of application context, display, or widget internal state, use XtAppLock. __ | void XtAppLock(app_context) XtAppContext app_context; app_context Specifies the application context to lock. |__ XtAppLock blocks until it is able to acquire the lock. Locking the application context also ensures that only the thread holding the lock makes Xlib calls from within Xt. An application that makes its own direct Xlib calls must either lock the application context around every call or enable thread locking in Xlib. To unlock a locked application context, use XtAppUnlock. __ | void XtAppUnlock(app_context) XtAppContext app_context; app_context Specifies the application context that was previ- ously locked. |__ 7.12.2.2. Locking the Process To ensure mutual exclusion of X Toolkit process global data, a widget writer must use XtProcessLock. 206 X Toolkit Intrinsics X11 Release 6.4 __ | void XtProcessLock() |__ XtProcessLock blocks until it is able to acquire the lock. Widget writers may use XtProcessLock to guarantee mutually exclusive access to widget static data. To unlock a locked process, use XtProcessUnlock. __ | void XtProcessUnlock() |__ To lock both an application context and the process at the same time, call XtAppLock first and then XtProcessLock. To release both locks, call XtProcessUnlock first and then XtAppUnlock. The order is important to avoid deadlock. 7.12.3. Event Management in a Multi-Threaded Environment In a nonthreaded environment an application writer could reasonably assume that it is safe to exit the application from a quit callback. This assumption may no longer hold true in a multi-threaded environment; therefore it is desir- able to provide a mechanism to terminate an event-processing loop without necessarily terminating its thread. To indicate that the event loop should terminate after the current event dispatch has completed, use XtAppSetExitFlag. __ | void XtAppSetExitFlag(app_context) XtAppContext app_context; app_context Specifies the application context. |__ XtAppMainLoop tests the value of the flag and will return if the flag is True. Application writers who implement their own main loop may test the value of the exit flag with XtAppGetExitFlag. 207 X Toolkit Intrinsics X11 Release 6.4 __ | Boolean XtAppGetExitFlag(app_context) XtAppContext app_context; app_context Specifies the application context. |__ XtAppGetExitFlag will normally return False, indicating that event processing may continue. When XtAppGetExitFlag returns True, the loop must terminate and return to the caller, which might then destroy the application context. Application writers should be aware that, if a thread is blocked in XtAppNextEvent, XtAppPeekEvent, or XtAppProces- sEvent and another thread in the same application context opens a new display, adds an alternate input, or a timeout, any new source(s) will not normally be "noticed" by the blocked thread. Any new sources are "noticed" the next time one of these functions is called. The Intrinsics manage access to events on a last-in, first- out basis. If multiple threads in the same application con- text block in XtAppNextEvent, XtAppPeekEvent, or XtAppPro- cessEvent, the last thread to call one of these functions is the first thread to return. 208 X Toolkit Intrinsics X11 Release 6.4 Chapter 8 Callbacks Applications and other widgets often need to register a pro- cedure with a widget that gets called under certain prespec- ified conditions. For example, when a widget is destroyed, every procedure on the widget's destroy_callbacks list is called to notify clients of the widget's impending doom. Every widget has an XtNdestroyCallbacks callback list resource. Widgets can define additional callback lists as they see fit. For example, the Pushbutton widget has a callback list to notify clients when the button has been activated. Except where otherwise noted, it is the intent that all Intrinsics functions may be called at any time, including from within callback procedures, action routines, and event handlers. 8.1. Using Callback Procedure and Callback List Definitions Callback procedure pointers for use in callback lists are of type XtCallbackProc. __ | typedef void (*XtCallbackProc)(Widget, XtPointer, XtPointer); Widget w; XtPointer client_data; XtPointer call_data; w Specifies the widget owning the list in which the callback is registered. client_data Specifies additional data supplied by the client when the procedure was registered. call_data Specifies any callback-specific data the widget wants to pass to the client. For example, when Scrollbar executes its XtNthumbChanged callback list, it passes the new position of the thumb. |__ The client_data argument provides a way for the client reg- istering the callback procedure also to register client- 209 X Toolkit Intrinsics X11 Release 6.4 specific data, for example, a pointer to additional informa- tion about the widget, a reason for invoking the callback, and so on. The client_data value may be NULL if all neces- sary information is in the widget. The call_data argument is a convenience to avoid having simple cases where the client could otherwise always call XtGetValues or a widget- specific function to retrieve data from the widget. Widgets should generally avoid putting complex state information in call_data. The client can use the more general data retrieval methods, if necessary. Whenever a client wants to pass a callback list as an argu- ment in an XtCreateWidget, XtSetValues, or XtGetValues call, it should specify the address of a NULL-terminated array of type XtCallbackList. __ | typedef struct { XtCallbackProc callback; XtPointer closure; } XtCallbackRec, *XtCallbackList; |__ For example, the callback list for procedures A and B with client data clientDataA and clientDataB, respectively, is static XtCallbackRec callbacks[] = { {A, (XtPointer) clientDataA}, {B, (XtPointer) clientDataB}, {(XtCallbackProc) NULL, (XtPointer) NULL} }; Although callback lists are passed by address in arglists and varargs lists, the Intrinsics recognize callback lists through the widget resource list and will copy the contents when necessary. Widget initialize and set_values procedures should not allocate memory for the callback list contents. The Intrinsics automatically do this, potentially using a different structure for their internal representation. 8.2. Identifying Callback Lists Whenever a widget contains a callback list for use by clients, it also exports in its public .h file the resource name of the callback list. Applications and client widgets never access callback list fields directly. Instead, they always identify the desired callback list by using the exported resource name. All the callback manipulation func- tions described in this chapter except XtCallCallbackList 210 X Toolkit Intrinsics X11 Release 6.4 check to see that the requested callback list is indeed implemented by the widget. For the Intrinsics to find and correctly handle callback lists, they must be declared with a resource type of XtR- Callback. The internal representation of a callback list is implementation-dependent; widgets may make no assumptions about the value stored in this resource if it is non-NULL. Except to compare the value to NULL (which is equivalent to XtCallbackStatus XtCallbackHasNone), access to callback list resources must be made through other Intrinsics procedures. 8.3. Adding Callback Procedures To add a callback procedure to a widget's callback list, use XtAddCallback. __ | void XtAddCallback(w, callback_name, callback, client_data) Widget w; String callback_name; XtCallbackProc callback; XtPointer client_data; w Specifies the widget. Must be of class Object or any subclass thereof. callback_name Specifies the callback list to which the procedure is to be appended. callback Specifies the callback procedure. client_data Specifies additional data to be passed to the specified procedure when it is invoked, or NULL. |__ A callback will be invoked as many times as it occurs in the callback list. To add a list of callback procedures to a given widget's callback list, use XtAddCallbacks. 211 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAddCallbacks(w, callback_name, callbacks) Widget w; String callback_name; XtCallbackList callbacks; w Specifies the widget. Must be of class Object or any subclass thereof. callback_name Specifies the callback list to which the proce- dures are to be appended. callbacks Specifies the null-terminated list of callback procedures and corresponding client data. |__ 8.4. Removing Callback Procedures To delete a callback procedure from a widget's callback list, use XtRemoveCallback. __ | void XtRemoveCallback(w, callback_name, callback, client_data) Widget w; String callback_name; XtCallbackProc callback; XtPointer client_data; w Specifies the widget. Must be of class Object or any subclass thereof. callback_name Specifies the callback list from which the proce- dure is to be deleted. callback Specifies the callback procedure. client_data Specifies the client data to match with the regis- tered callback entry. |__ The XtRemoveCallback function removes a callback only if both the procedure and the client data match. To delete a list of callback procedures from a given wid- get's callback list, use XtRemoveCallbacks. 212 X Toolkit Intrinsics X11 Release 6.4 __ | void XtRemoveCallbacks(w, callback_name, callbacks) Widget w; String callback_name; XtCallbackList callbacks; w Specifies the widget. Must be of class Object or any subclass thereof. callback_name Specifies the callback list from which the proce- dures are to be deleted. callbacks Specifies the null-terminated list of callback procedures and corresponding client data. |__ To delete all callback procedures from a given widget's callback list and free all storage associated with the call- back list, use XtRemoveAllCallbacks. __ | void XtRemoveAllCallbacks(w, callback_name) Widget w; String callback_name; w Specifies the widget. Must be of class Object or any subclass thereof. callback_name Specifies the callback list to be cleared. |__ 8.5. Executing Callback Procedures To execute the procedures in a given widget's callback list, specifying the callback list by resource name, use XtCall- Callbacks. 213 X Toolkit Intrinsics X11 Release 6.4 __ | void XtCallCallbacks(w, callback_name, call_data) Widget w; String callback_name; XtPointer call_data; w Specifies the widget. Must be of class Object or any subclass thereof. callback_name Specifies the callback list to be executed. call_data Specifies a callback-list-specific data value to pass to each of the callback procedure in the list, or NULL. |__ XtCallCallbacks calls each of the callback procedures in the list named by callback_name in the specified widget, passing the client data registered with the procedure and call-data. To execute the procedures in a callback list, specifying the callback list by address, use XtCallCallbackList. __ | void XtCallCallbackList(widget, callbacks, call_data) Widget widget; XtCallbackList callbacks; XtPointer call_data; widget Specifies the widget instance that contains the callback list. Must be of class Object or any subclass thereof. callbacks Specifies the callback list to be executed. call_data Specifies a callback-list-specific data value to pass to each of the callback procedures in the list, or NULL. |__ The callbacks parameter must specify the contents of a wid- get or object resource declared with representation type XtRCallback. If callbacks is NULL, XtCallCallbackList returns immediately; otherwise it calls each of the callback procedures in the list, passing the client data and call_data. 214 X Toolkit Intrinsics X11 Release 6.4 8.6. Checking the Status of a Callback List To find out the status of a given widget's callback list, use XtHasCallbacks. __ | typedef enum {XtCallbackNoList, XtCallbackHasNone, XtCallbackHasSome} XtCallbackStatus; XtCallbackStatus XtHasCallbacks(w, callback_name) Widget w; String callback_name; w Specifies the widget. Must be of class Object or any subclass thereof. callback_name Specifies the callback list to be checked. |__ The XtHasCallbacks function first checks to see if the wid- get has a callback list identified by callback_name. If the callback list does not exist, XtHasCallbacks returns XtCall- backNoList. If the callback list exists but is empty, it returns XtCallbackHasNone. If the callback list exists and has at least one callback registered, it returns XtCallback- HasSome. 215 X Toolkit Intrinsics X11 Release 6.4 Chapter 9 Resource Management A resource is a field in the widget record with a corre- sponding resource entry in the resources list of the widget or any of its superclasses. This means that the field is settable by XtCreateWidget (by naming the field in the argu- ment list), by an entry in a resource file (by using either the name or class), and by XtSetValues. In addition, it is readable by XtGetValues. Not all fields in a widget record are resources. Some are for bookkeeping use by the generic routines (like managed and being_destroyed). Others can be for local bookkeeping, and still others are derived from resources (many graphics contexts and pixmaps). Widgets typically need to obtain a large set of resources at widget creation time. Some of the resources come from the argument list supplied in the call to XtCreateWidget, some from the resource database, and some from the internal defaults specified by the widget. Resources are obtained first from the argument list, then from the resource database for all resources not specified in the argument list, and last, from the internal default, if needed. 9.1. Resource Lists A resource entry specifies a field in the widget, the tex- tual name and class of the field that argument lists and external resource files use to refer to the field, and a default value that the field should get if no value is spec- ified. The declaration for the XtResource structure is __ | typedef struct { String resource_name; String resource_class; String resource_type; Cardinal resource_size; Cardinal resource_offset; String default_type; XtPointer default_addr; } XtResource, *XtResourceList; |__ 216 X Toolkit Intrinsics X11 Release 6.4 When the resource list is specified as the CoreClassPart, ObjectClassPart, RectObjClassPart, or ConstraintClassPart resources field, the strings pointed to by resource_name, resource_class, resource_type, and default_type must be per- manently allocated prior to or during the execution of the class initialization procedure and must not be subsequently deallocated. The resource_name field contains the name used by clients to access the field in the widget. By convention, it starts with a lowercase letter and is spelled exactly like the field name, except all underscores (_) are deleted and the next letter is replaced by its uppercase counterpart. For example, the resource name for background_pixel becomes backgroundPixel. Resource names beginning with the two- character sequence ``xt'', and resource classes beginning with the two-character sequence ``Xt'' are reserved to the Intrinsics for future standard and implementation-dependent uses. Widget header files typically contain a symbolic name for each resource name. All resource names, classes, and types used by the Intrinsics are named in . The Intrinsics's symbolic resource names begin with ``XtN'' and are followed by the string name (for example, XtNbackgroundPixel for backgroundPixel). The resource_class field contains the class string used in resource specification files to identify the field. A resource class provides two functions: o It isolates an application from different representa- tions that widgets can use for a similar resource. o It lets you specify values for several actual resources with a single name. A resource class should be chosen to span a group of closely related fields. For example, a widget can have several pixel resources: background, foreground, border, block cursor, pointer cur- sor, and so on. Typically, the background defaults to white and everything else to black. The resource class for each of these resources in the resource list should be chosen so that it takes the minimal number of entries in the resource database to make the background ivory and everything else darkblue. In this case, the background pixel should have a resource class of ``Background'' and all the other pixel entries a resource class of ``Foreground''. Then, the resource file needs only two lines to change all pixels to ivory or dark- blue: 217 X Toolkit Intrinsics X11 Release 6.4 *Background: ivory *Foreground: darkblue Similarly, a widget may have several font resources (such as normal and bold), but all fonts should have the class Font. Thus, changing all fonts simply requires only a single line in the default resource file: *Font: 6x13 By convention, resource classes are always spelled starting with a capital letter to distinguish them from resource names. Their symbolic names are preceded with ``XtC'' (for example, XtCBackground). The resource_type field gives the physical representation type of the resource and also encodes information about the specific usage of the field. By convention, it starts with an uppercase letter and is spelled identically to the type name of the field. The resource type is used when resources are fetched to convert from the resource database format (usually String) or the format of the resource default value (almost anything, but often String) to the desired physical representation (see Section 9.6). The Intrinsics define the following resource types: ------------------------------------------------------ Resource Type Structure or Field Type ------------------------------------------------------ XtRAcceleratorTable XtAccelerators XtRAtom Atom XtRBitmap Pixmap, depth=1 XtRBoolean Boolean XtRBool Bool XtRCallback XtCallbackList XtRCardinal Cardinal XtRColor XColor XtRColormap Colormap XtRCommandArgArray String* XtRCursor Cursor XtRDimension Dimension XtRDirectoryString String XtRDisplay Display* XtREnum XtEnum XtREnvironmentArray String* XtRFile FILE* XtRFloat float XtRFont Font XtRFontSet XFontSet XtRFontStruct XFontStruct* 218 X Toolkit Intrinsics X11 Release 6.4 ------------------------------------------------------ Resource Type Structure or Field Type ------------------------------------------------------ XtRFunction (*)() XtRGeometry char*, format as defined by XParseGeometry XtRGravity int XtRInitialState int XtRInt int XtRLongBoolean long XtRObject Object XtRPixel Pixel XtRPixmap Pixmap XtRPointer XtPointer XtRPosition Position XtRRestartStyle unsigned char XtRScreen Screen* XtRShort short XtRSmcConn XtPointer XtRString String XtRStringArray String* XtRStringTable String* XtRTranslationTable XtTranslations XtRUnsignedChar unsigned char XtRVisual Visual* XtRWidget Widget XtRWidgetClass WidgetClass XtRWidgetList WidgetList XtRWindow Window ------------------------------------------------------ also defines the following resource types as a convenience for widgets, although they do not have any corresponding data type assigned: XtREditMode, XtRJustify, and XtROrientation. The resource_size field is the size of the physical repre- sentation in bytes; you should specify it as sizeof(type) so that the compiler fills in the value. The resource_offset field is the offset in bytes of the field within the widget. You should use the XtOffsetOf macro to retrieve this value. The default_type field is the representation type of the default resource value. If default_type is different from resource_type and the default value is needed, the resource manager invokes a conversion procedure from default_type to resource_type. Whenever possible, the default type should be identical to the resource type in order to minimize wid- get creation time. However, there are sometimes no values of the type that the program can easily specify. In this case, it should be a value for which the converter is guar- anteed to work (for example, XtDefaultForeground for a pixel resource). The default_addr field specifies the address of 219 X Toolkit Intrinsics X11 Release 6.4 the default resource value. As a special case, if default_type is XtRString, then the value in the default_addr field is the pointer to the string rather than a pointer to the pointer. The default is used if a resource is not specified in the argument list or in the resource database or if the conversion from the representation type stored in the resource database fails, which can happen for various reasons (for example, a misspelled entry in a resource file). Two special representation types (XtRImmediate and XtRCall- Proc) are usable only as default resource types. XtRImmedi- ate indicates that the value in the default_addr field is the actual value of the resource rather than the address of the value. The value must be in the correct representation type for the resource, coerced to an XtPointer. No conver- sion is possible, since there is no source representation type. XtRCallProc indicates that the value in the default_addr field is a procedure pointer. This procedure is automatically invoked with the widget, resource_offset, and a pointer to an XrmValue in which to store the result. XtRCallProc procedure pointers are of type XtResourceDe- faultProc. __ | typedef void (*XtResourceDefaultProc)(Widget, int, XrmValue*); Widget w; int offset; XrmValue *value; w Specifies the widget whose resource value is to be obtained. offset Specifies the offset of the field in the widget record. value Specifies the resource value descriptor to return. |__ The XtResourceDefaultProc procedure should fill in the value->addr field with a pointer to the resource value in its correct representation type. To get the resource list structure for a particular class, use XtGetResourceList. 220 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetResourceList(class, resources_return, num_resources_return); WidgetClass class; XtResourceList *resources_return; Cardinal *num_resources_return; class Specifies the object class to be queried. It must be objectClass or any subclass thereof. resources_return Returns the resource list. num_resources_return Returns the number of entries in the resource list. |__ If XtGetResourceList is called before the class is initial- ized, it returns the resource list as specified in the class record. If it is called after the class has been initial- ized, XtGetResourceList returns a merged resource list that includes the resources for all superclasses. The list returned by XtGetResourceList should be freed using XtFree when it is no longer needed. To get the constraint resource list structure for a particu- lar widget class, use XtGetConstraintResourceList. __ | void XtGetConstraintResourceList(class, resources_return, num_resources_return) WidgetClass class; XtResourceList *resources_return; Cardinal *num_resources_return; class Specifies the object class to be queried. It must be objectClass or any subclass thereof. resources_return Returns the constraint resource list. num_resources_return Returns the number of entries in the con- straint resource list. |__ If XtGetConstraintResourceList is called before the widget class is initialized, the resource list as specified in the widget class Constraint part is returned. If XtGetCon- straintResourceList is called after the widget class has been initialized, the merged resource list for the class and 221 X Toolkit Intrinsics X11 Release 6.4 all Constraint superclasses is returned. If the specified class is not a subclass of constraintWidgetClass, *resources_return is set to NULL and *num_resources_return is set to zero. The list returned by XtGetConstraintRe- sourceList should be freed using XtFree when it is no longer needed. The routines XtSetValues and XtGetValues also use the resource list to set and get widget state; see Sections 9.7.1 and 9.7.2. Here is an abbreviated version of a possible resource list for a Label widget: /* Resources specific to Label */ static XtResource resources[] = { {XtNforeground, XtCForeground, XtRPixel, sizeof(Pixel), XtOffsetOf(LabelRec, label.foreground), XtRString, XtDefaultForeground}, {XtNfont, XtCFont, XtRFontStruct, sizeof(XFontStruct*), XtOffsetOf(LabelRec, label.font), XtRString, XtDefaultFont}, {XtNlabel, XtCLabel, XtRString, sizeof(String), XtOffsetOf(LabelRec, label.label), XtRString, NULL}, . . . } The complete resource name for a field of a widget instance is the concatenation of the application shell name (from XtAppCreateShell), the instance names of all the widget's parents up to the top of the widget tree, the instance name of the widget itself, and the resource name of the specified field of the widget. Similarly, the full resource class of a field of a widget instance is the concatenation of the application class (from XtAppCreateShell), the widget class names of all the widget's parents up to the top of the wid- get tree, the widget class name of the widget itself, and the resource class of the specified field of the widget. 9.2. Byte Offset Calculations To determine the byte offset of a field within a structure type, use XtOffsetOf. 222 X Toolkit Intrinsics X11 Release 6.4 __ | Cardinal XtOffsetOf(structure_type, field_name) Type structure_type; Field field_name; structure_type Specifies a type that is declared as a structure. field_name Specifies the name of a member within the struc- ture. |__ The XtOffsetOf macro expands to a constant expression that gives the offset in bytes to the specified structure member from the beginning of the structure. It is normally used to statically initialize resource lists and is more portable than XtOffset, which serves the same function. To determine the byte offset of a field within a structure pointer type, use XtOffset. __ | Cardinal XtOffset(pointer_type, field_name) Type pointer_type; Field field_name; pointer_type Specifies a type that is declared as a pointer to a structure. field_name Specifies the name of a member within the struc- ture. |__ The XtOffset macro expands to a constant expression that gives the offset in bytes to the specified structure member from the beginning of the structure. It may be used to statically initialize resource lists. XtOffset is less portable than XtOffsetOf. 9.3. Superclass-to-Subclass Chaining of Resource Lists The XtCreateWidget function gets resources as a superclass- to-subclass chained operation. That is, the resources spec- ified in the objectClass resource list are fetched, then those in rectObjClass, and so on down to the resources spec- ified for this widget's class. Within a class, resources are 223 X Toolkit Intrinsics X11 Release 6.4 fetched in the order they are declared. In general, if a widget resource field is declared in a superclass, that field is included in the superclass's resource list and need not be included in the subclass's resource list. For example, the Core class contains a resource entry for background_pixel. Consequently, the implementation of Label need not also have a resource entry for background_pixel. However, a subclass, by specifying a resource entry for that field in its own resource list, can override the resource entry for any field declared in a superclass. This is most often done to override the defaults provided in the superclass with new ones. At class initialization time, resource lists for that class are scanned from the superclass down to the class to look for resources with the same offset. A matching resource in a subclass will be reordered to override the superclass entry. If reordering is necessary, a copy of the superclass resource list is made to avoid affecting other subclasses of the superclass. Also at class initialization time, the Intrinsics produce an internal representation of the resource list to optimize access time when creating widgets. In order to save memory, the Intrinsics may overwrite the storage allocated for the resource list in the class record; therefore, widgets must allocate resource lists in writable storage and must not access the list contents directly after the class_initialize procedure has returned. 9.4. Subresources A widget does not do anything to retrieve its own resources; instead, XtCreateWidget does this automatically before call- ing the class initialize procedure. Some widgets have subparts that are not widgets but for which the widget would like to fetch resources. Such wid- gets call XtGetSubresources to accomplish this. 224 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetSubresources(w, base, name, class, resources, num_resources, args, num_args) Widget w; XtPointer base; String name; String class; XtResourceList resources; Cardinal num_resources; ArgList args; Cardinal num_args; w Specifies the object used to qualify the subpart resource name and class. Must be of class Object or any subclass thereof. base Specifies the base address of the subpart data structure into which the resources will be writ- ten. name Specifies the name of the subpart. class Specifies the class of the subpart. resources Specifies the resource list for the subpart. num_resources Specifies the number of entries in the resource list. args Specifies the argument list to override any other resource specifications. num_args Specifies the number of entries in the argument list. |__ The XtGetSubresources function constructs a name and class list from the application name and class, the names and classes of all the object's ancestors, and the object itself. Then it appends to this list the name and class pair passed in. The resources are fetched from the argument list, the resource database, or the default values in the resource list. Then they are copied into the subpart record. If args is NULL, num_args must be zero. However, if num_args is zero, the argument list is not referenced. XtGetSubresources may overwrite the specified resource list with an equivalent representation in an internal format, which optimizes access time if the list is used repeatedly. The resource list must be allocated in writable storage, and the caller must not modify the list contents after the call if the same list is to be used again. Resources fetched by XtGetSubresources are reference-counted as if they were 225 X Toolkit Intrinsics X11 Release 6.4 referenced by the specified object. Subresources might therefore be freed from the conversion cache and destroyed when the object is destroyed, but not before then. To fetch resources for widget subparts using varargs lists, use XtVaGetSubresources. __ | void XtVaGetSubresources(w, base, name, class, resources, num_resources, ...) Widget w; XtPointer base; String name; String class; XtResourceList resources; Cardinal num_resources; w Specifies the object used to qualify the subpart resource name and class. Must be of class Object or any subclass thereof. base Specifies the base address of the subpart data structure into which the resources will be writ- ten. name Specifies the name of the subpart. class Specifies the class of the subpart. resources Specifies the resource list for the subpart. num_resources Specifies the number of entries in the resource list. ... Specifies the variable argument list to override any other resource specifications. |__ XtVaGetSubresources is identical in function to XtGetSubre- sources with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. 9.5. Obtaining Application Resources To retrieve resources that are not specific to a widget but apply to the overall application, use XtGetApplicationRe- sources. 226 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetApplicationResources(w, base, resources, num_resources, args, num_args) Widget w; XtPointer base; XtResourceList resources; Cardinal num_resources; ArgList args; Cardinal num_args; w Specifies the object that identifies the resource database to search (the database is that associ- ated with the display for this object). Must be of class Object or any subclass thereof. base Specifies the base address into which the resource values will be written. resources Specifies the resource list. num_resources Specifies the number of entries in the resource list. args Specifies the argument list to override any other resource specifications. num_args Specifies the number of entries in the argument list. |__ The XtGetApplicationResources function first uses the passed object, which is usually an application shell widget, to construct a resource name and class list. The full name and class of the specified object (that is, including its ances- tors, if any) is logically added to the front of each resource name and class. Then it retrieves the resources from the argument list, the resource database, or the resource list default values. After adding base to each address, XtGetApplicationResources copies the resources into the addresses obtained by adding base to each offset in the resource list. If args is NULL, num_args must be zero. However, if num_args is zero, the argument list is not ref- erenced. The portable way to specify application resources is to declare them as members of a structure and pass the address of the structure as the base argument. XtGetApplicationResources may overwrite the specified resource list with an equivalent representation in an inter- nal format, which optimizes access time if the list is used repeatedly. The resource list must be allocated in writable storage, and the caller must not modify the list contents after the call if the same list is to be used again. Any per-display resources fetched by XtGetApplicationResources 227 X Toolkit Intrinsics X11 Release 6.4 will not be freed from the resource cache until the display is closed. To retrieve resources for the overall application using varargs lists, use XtVaGetApplicationResources. __ | void XtVaGetApplicationResources(w, base, resources, num_resources, ...) Widget w; XtPointer base; XtResourceList resources; Cardinal num_resources; w Specifies the object that identifies the resource database to search (the database is that associ- ated with the display for this object). Must be of class Object or any subclass thereof. base Specifies the base address into which the resource values will be written. resources Specifies the resource list for the subpart. num_resources Specifies the number of entries in the resource list. ... Specifies the variable argument list to override any other resource specifications. |__ XtVaGetApplicationResources is identical in function to XtGetApplicationResources with the args and num_args parame- ters replaced by a varargs list, as described in Section 2.5.1. 9.6. Resource Conversions The Intrinsics provide a mechanism for registering represen- tation converters that are automatically invoked by the resource-fetching routines. The Intrinsics additionally provide and register several commonly used converters. This resource conversion mechanism serves several purposes: o It permits user and application resource files to con- tain textual representations of nontextual values. o It allows textual or other representations of default resource values that are dependent on the display, screen, or colormap, and thus must be computed at 228 X Toolkit Intrinsics X11 Release 6.4 runtime. o It caches conversion source and result data. Conver- sions that require much computation or space (for exam- ple, string-to-translation-table) or that require round-trips to the server (for example, string-to-font or string-to-color) are performed only once. 9.6.1. Predefined Resource Converters The Intrinsics define all the representations used in the Object, RectObj, Core, Composite, Constraint, and Shell wid- get classes. The Intrinsics register the following resource converters that accept input values of representation type XtRString. --------------------------------------------------------------------------- Target Representation Converter Name Additional Args --------------------------------------------------------------------------- XtRAcceleratorTable XtCvtStringToAccelera- torTable XtRAtom XtCvtStringToAtom Display* XtRBoolean XtCvtStringToBoolean XtRBool XtCvtStringToBool XtRCommandArgArray XtCvtStringToCommandAr- gArray XtRCursor XtCvtStringToCursor Display* XtRDimension XtCvtStringToDimension XtRDirectoryString XtCvtStringToDirectoryS- tring XtRDisplay XtCvtStringToDisplay XtRFile XtCvtStringToFile XtRFloat XtCvtStringToFloat XtRFont XtCvtStringToFont Display* XtRFontSet XtCvtStringToFontSet Display*, String locale XtRFontStruct XtCvtStringToFontStruct Display* XtRGravity XtCvtStringToGravity XtRInitialState XtCvtStringToInitial- State XtRInt XtCvtStringToInt XtRPixel XtCvtStringToPixel colorConvertArgs XtRPosition XtCvtStringToPosition XtRRestartStyle XtCvtStringToRestart- Style XtRShort XtCvtStringToShort XtRTranslationTable XtCvtStringToTransla- tionTable XtRUnsignedChar XtCvtStringToUnsigned- Char XtRVisual XtCvtStringToVisual Screen*, Cardinal depth --------------------------------------------------------------------------- 229 X Toolkit Intrinsics X11 Release 6.4 The String-to-Pixel conversion has two predefined constants that are guaranteed to work and contrast with each other: XtDefaultForeground and XtDefaultBackground. They evaluate to the black and white pixel values of the widget's screen, respectively. If the application resource reverseVideo is True, they evaluate to the white and black pixel values of the widget's screen, respectively. Similarly, the String- to-Font and String-to-FontStruct converters recognize the constant XtDefaultFont and evaluate this in the following manner: o Query the resource database for the resource whose full name is ``xtDefaultFont'', class ``XtDefaultFont'' (that is, no widget name/class prefixes), and use a type XtRString value returned as the font name or a type XtRFont or XtRFontStruct value directly as the resource value. o If the resource database does not contain a value for xtDefaultFont, class XtDefaultFont, or if the returned font name cannot be successfully opened, an implementa- tion-defined font in ISO8859-1 character set encoding is opened. (One possible algorithm is to perform an XListFonts using a wildcard font name and use the first font in the list. This wildcard font name should be as broad as possible to maximize the probability of locat- ing a useable font; for example, "-*-*-*-R-*-*-*-120-*-*-*-*-ISO8859-1".) o If no suitable ISO8859-1 font can be found, issue a warning message and return False. The String-to-FontSet converter recognizes the constant XtDefaultFontSet and evaluate this in the following manner: o Query the resource database for the resource whose full name is ``xtDefaultFontSet'', class ``XtDefault- FontSet'' (that is, no widget name/class prefixes), and use a type XtRString value returned as the base font name list or a type XtRFontSet value directly as the resource value. o If the resource database does not contain a value for xtDefaultFontSet, class XtDefaultFontSet, or if a font set cannot be successfully created from this resource, an implementation-defined font set is created. (One possible algorithm is to perform an XCreateFontSet using a wildcard base font name. This wildcard base font name should be as broad as possible to maximize the probability of locating a useable font; for exam- ple, "-*-*-*-R-*-*-*-120-*-*-*-*".) o If no suitable font set can be created, issue a warning message and return False. 230 X Toolkit Intrinsics X11 Release 6.4 If a font set is created but missing_charset_list is not empty, a warning is issued and the partial font set is returned. The Intrinsics register the String-to-FontSet converter with a conversion argument list that extracts the current process locale at the time the converter is invoked. This ensures that the converter is invoked again if the same conversion is required in a different locale. The String-to-Gravity conversion accepts string values that are the names of window and bit gravities and their numeri- cal equivalents, as defined in Xlib -- C Language X Inter- face: ForgetGravity, UnmapGravity, NorthWestGravity, North- Gravity, NorthEastGravity, WestGravity, CenterGravity, East- Gravity, SouthWestGravity, SouthGravity, SouthEastGravity, and StaticGravity. Alphabetic case is not significant in the conversion. The String-to-CommandArgArray conversion parses a String into an array of strings. White space characters separate elements of the command line. The converter recognizes the backslash character ``\'' as an escape character to allow the following white space character to be part of the array element. The String-to-DirectoryString conversion recognizes the string ``XtCurrentDirectory'' and returns the result of a call to the operating system to get the current directory. The String-to-RestartStyle conversion accepts the values RestartIfRunning, RestartAnyway, RestartImmediately, and RestartNever as defined by the X Session Management Proto- col. The String-to-InitialState conversion accepts the values NormalState or IconicState as defined by the Inter-Client Communication Conventions Manual. The String-to-Visual conversion calls XMatchVisualInfo using the screen and depth fields from the core part and returns the first matching Visual on the list. The widget resource list must be certain to specify any resource of type XtRVi- sual after the depth resource. The allowed string values are the visual class names defined in X Window System Proto- col, Section 8; StaticGray, StaticColor, TrueColor, GrayScale, PseudoColor, and DirectColor. The Intrinsics register the following resource converter that accepts an input value of representation type XtRColor. ----------------------------------------------------------------- Target Representation Converter Name Additional Args 231 X Toolkit Intrinsics X11 Release 6.4 ----------------------------------------------------------------- XtRPixel XtCvtColorToPixel ----------------------------------------------------------------- The Intrinsics register the following resource converters that accept input values of representation type XtRInt. ----------------------------------------------------------------- Target Representation Converter Name Additional Args ----------------------------------------------------------------- XtRBoolean XtCvtIntToBoolean XtRBool XtCvtIntToBool XtRColor XtCvtIntToColor colorConver- tArgs XtRDimension XtCvtIntToDimension XtRFloat XtCvtIntToFloat XtRFont XtCvtIntToFont XtRPixel XtCvtIntToPixel XtRPixmap XtCvtIntToPixmap XtRPosition XtCvtIntToPosition XtRShort XtCvtIntToShort XtRUnsignedChar XtCvtIntToUnsignedChar ----------------------------------------------------------------- The Intrinsics register the following resource converter that accepts an input value of representation type XtRPixel. ----------------------------------------------------------------- Target Representation Converter Name Additional Args ----------------------------------------------------------------- XtRColor XtCvtPixelToColor ----------------------------------------------------------------- 9.6.2. New Resource Converters Type converters use pointers to XrmValue structures (defined in ; see Section 15.4 in Xlib -- C Language X Interface) for input and output values. 232 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { unsigned int size; XPointer addr; } XrmValue, *XrmValuePtr; |__ The addr field specifies the address of the data, and the size field gives the total number of significant bytes in the data. For values of type String, addr is the address of the first character and size includes the NULL-terminating byte. A resource converter procedure pointer is of type XtTypeCon- verter. __ | typedef Boolean (*XtTypeConverter)(Display*, XrmValue*, Cardinal*, XrmValue*, XrmValue*, XtPointer*); Display *display; XrmValue *args; Cardinal *num_args; XrmValue *from; XrmValue *to; XtPointer *converter_data; display Specifies the display connection with which this conversion is associated. args Specifies a list of additional XrmValue arguments to the converter if additional context is needed to perform the conversion, or NULL. For example, the String-to-Font converter needs the widget's display, and the String-to-Pixel converter needs the widget's screen and colormap. num_args Specifies the number of entries in args. from Specifies the value to convert. to Specifies a descriptor for a location into which to store the converted value. converter_data Specifies a location into which the converter may store converter-specific data associated with this conversion. |__ The display argument is normally used only when generating error messages, to identify the application context (with 233 X Toolkit Intrinsics X11 Release 6.4 the function XtDisplayToApplicationContext). The to argument specifies the size and location into which the converter should store the converted value. If the addr field is NULL, the converter should allocate appropriate storage and store the size and location into the to descrip- tor. If the type converter allocates the storage, it remains under the ownership of the converter and must not be modified by the caller. The type converter is permitted to use static storage for this purpose, and therefore the caller must immediately copy the data upon return from the converter. If the addr field is not NULL, the converter must check the size field to ensure that sufficient space has been allocated before storing the converted value. If insufficient space is specified, the converter should update the size field with the number of bytes required and return False without modifying the data at the specified location. If sufficient space was allocated by the caller, the con- verter should update the size field with the number of bytes actually occupied by the converted value. For converted values of type XtRString, the size should include the NULL- terminating byte, if any. The converter may store any value in the location specified in converter_data; this value will be passed to the destructor, if any, when the resource is freed by the Intrinsics. The converter must return True if the conversion was suc- cessful and False otherwise. If the conversion cannot be performed because of an improper source value, a warning message should also be issued with XtAppWarningMsg. Most type converters just take the data described by the specified from argument and return data by writing into the location specified in the to argument. A few need other information, which is available in args. A type converter can invoke another type converter, which allows differing sources that may convert into a common intermediate result to make maximum use of the type converter cache. Note that if an address is written into to->addr, it cannot be that of a local variable of the converter because the data will not be valid after the converter returns. Static variables may be used, as in the following example. If the converter modifies the resource database, the changes affect any in-progress widget creation, XtGetApplicationResources, or XtGetSubresources in an implementation-defined manner; however, insertion of new entries or changes to existing entries is allowed and will not directly cause an error. The following is an example of a converter that takes a string and converts it to a Pixel. Note that the display parameter is used only to generate error messages; the 234 X Toolkit Intrinsics X11 Release 6.4 Screen conversion argument is still required to inform the Intrinsics that the converted value is a function of the particular display (and colormap). #define done(type, value) \ { \ if (toVal->addr != NULL) { \ if (toVal->size < sizeof(type)) {\ toVal->size = sizeof(type);\ return False; \ } \ *(type*)(toVal->addr) = (value);\ } \ else { \ static type static_val; \ static_val = (value); \ toVal->addr = (XPointer)&static_val;\ } \ toVal->size = sizeof(type); \ return True; \ } static Boolean CvtStringToPixel(dpy, args, num_args, fromVal, toVal, converter_data) Display *dpy; XrmValue *args; Cardinal *num_args; XrmValue *fromVal; XrmValue *toVal; XtPointer *converter_data; { static XColor screenColor; XColor exactColor; Screen *screen; Colormap colormap; Status status; if (*num_args != 2) XtAppWarningMsg(XtDisplayToApplicationContext(dpy), "wrongParameters", "cvtStringToPixel", "XtToolkitError", "String to pixel conversion needs screen and colormap arguments", (String *)NULL, (Cardinal *)NULL); screen = *((Screen**) args[0].addr); colormap = *((Colormap *) args[1].addr); if (CompareISOLatin1(str, XtDefaultBackground) == 0) { *closure_ret = False; done(Pixel, WhitePixelOfScreen(screen)); } if (CompareISOLatin1(str, XtDefaultForeground) == 0) { *closure_ret = False; done(Pixel, BlackPixelOfScreen(screen)); 235 X Toolkit Intrinsics X11 Release 6.4 } status = XAllocNamedColor(DisplayOfScreen(screen), colormap, (char*)fromVal->addr, &screenColor, &exactColor); if (status == 0) { String params[1]; Cardinal num_params = 1; params[0] = (String)fromVal->addr; XtAppWarningMsg(XtDisplayToApplicationContext(dpy), "noColormap", "cvtStringToPixel", "XtToolkitError", "Cannot allocate colormap entry for \"%s\"", params, &num_params); *converter_data = (char *) False; return False; } else { *converter_data = (char *) True; done(Pixel, &screenColor.pixel); } } All type converters should define some set of conversion values for which they are guaranteed to succeed so these can be used in the resource defaults. This issue arises only with conversions, such as fonts and colors, where there is no string representation that all server implementations will necessarily recognize. For resources like these, the converter should define a symbolic constant in the same man- ner as XtDefaultForeground, XtDefaultBackground, and XtDe- faultFont. To allow the Intrinsics to deallocate resources produced by type converters, a resource destructor procedure may also be provided. A resource destructor procedure pointer is of type XtDe- structor. 236 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtDestructor) (XtAppContext, XrmValue*, XtPointer, XrmValue*, Cardinal*); XtAppContext app; XrmValue *to; XtPointer converter_data; XrmValue *args; Cardinal *num_args; app Specifies an application context in which the resource is being freed. to Specifies a descriptor for the resource produced by the type converter. converter_data Specifies the converter-specific data returned by the type converter. args Specifies the additional converter arguments as passed to the type converter when the conversion was performed. num_args Specifies the number of entries in args. |__ The destructor procedure is responsible for freeing the resource specified by the to argument, including any auxil- iary storage associated with that resource, but not the mem- ory directly addressed by the size and location in the to argument or the memory specified by args. 9.6.3. Issuing Conversion Warnings The XtDisplayStringConversionWarning procedure is a conve- nience routine for resource type converters that convert from string values. 237 X Toolkit Intrinsics X11 Release 6.4 __ | void XtDisplayStringConversionWarning(display, from_value, to_type) Display *display; String from_value, to_type; display Specifies the display connection with which the conversion is associated. from_value Specifies the string that could not be converted. to_type Specifies the target representation type requested. |__ The XtDisplayStringConversionWarning procedure issues a warning message using XtAppWarningMsg with name ``conver- sionError'', type ``string'', class ``XtToolkitError'', and the default message ``Cannot convert "from_value" to type to_type''. To issue other types of warning or error messages, the type converter should use XtAppWarningMsg or XtAppErrorMsg. To retrieve the application context associated with a given display connection, use XtDisplayToApplicationContext. __ | XtAppContext XtDisplayToApplicationContext( display ) Display *display; display Specifies an open and initialized display connec- tion. |__ The XtDisplayToApplicationContext function returns the application context in which the specified display was ini- tialized. If the display is not known to the Intrinsics, an error message is issued. 9.6.4. Registering a New Resource Converter When registering a resource converter, the client must spec- ify the manner in which the conversion cache is to be used when there are multiple calls to the converter. Conversion cache control is specified via an XtCacheType argument. 238 X Toolkit Intrinsics X11 Release 6.4 __ | typedef int XtCacheType; |__ An XtCacheType field may contain one of the following val- ues: XtCacheNone Specifies that the results of a previous conversion may not be reused to satisfy any other resource requests; the specified converter will be called each time the converted value is required. XtCacheAll Specifies that the results of a previous conversion should be reused for any resource request that depends upon the same source value and conversion arguments. XtCacheByDisplay Specifies that the results of a previous conversion should be used as for XtCacheAll but the destructor will be called, if specified, if XtCloseDisplay is called for the display connection associated with the converted value, and the value will be removed from the conversion cache. The qualifier XtCacheRefCount may be ORed with any of the above values. If XtCacheRefCount is specified, calls to XtCreateWidget, XtCreateManagedWidget, XtGetApplicationRe- sources, and XtGetSubresources that use the converted value will be counted. When a widget using the converted value is destroyed, the count is decremented, and, if the count reaches zero, the destructor procedure will be called and the converted value will be removed from the conversion cache. To register a type converter for all application contexts in a process, use XtSetTypeConverter, and to register a type converter in a single application context, use XtAppSetType- Converter. 239 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetTypeConverter(from_type, to_type, converter, convert_args, num_args, cache_type, destructor) String from_type; String to_type; XtTypeConverter converter; XtConvertArgList convert_args; Cardinal num_args; XtCacheType cache_type; XtDestructor destructor; from_type Specifies the source type. to_type Specifies the destination type. converter Specifies the resource type converter procedure. convert_args Specifies additional conversion arguments, or NULL. num_args Specifies the number of entries in convert_args. cache_type Specifies whether or not resources produced by this converter are sharable or display-specific and when they should be freed. destructor Specifies a destroy procedure for resources pro- duced by this conversion, or NULL if no additional action is required to deallocate resources pro- duced by the converter. void XtAppSetTypeConverter(app_context, from_type, to_type, converter, convert_args, num_args, cache_type, destructor) XtAppContext app_context; String from_type; String to_type; XtTypeConverter converter; XtConvertArgList convert_args; Cardinal num_args; XtCacheType cache_type; XtDestructor destructor; app_context Specifies the application context. from_type Specifies the source type. to_type Specifies the destination type. 240 X Toolkit Intrinsics X11 Release 6.4 converter Specifies the resource type converter procedure. convert_args Specifies additional conversion arguments, or NULL. num_args Specifies the number of entries in convert_args. cache_type Specifies whether or not resources produced by this converter are sharable or display-specific and when they should be freed. destructor Specifies a destroy procedure for resources pro- duced by this conversion, or NULL if no additional action is required to deallocate resources pro- duced by the converter. |__ XtSetTypeConverter registers the specified type converter and destructor in all application contexts created by the calling process, including any future application contexts that may be created. XtAppSetTypeConverter registers the specified type converter in the single application context specified. If the same from_type and to_type are specified in multiple calls to either function, the most recent over- rides the previous ones. For the few type converters that need additional arguments, the Intrinsics conversion mechanism provides a method of specifying how these arguments should be computed. The enu- merated type XtAddressMode and the structure XtConvertArgRec specify how each argument is derived. These are defined in . 241 X Toolkit Intrinsics X11 Release 6.4 __ | typedef enum { /* address mode parameter representation */ XtAddress, /* address */ XtBaseOffset, /* offset */ XtImmediate, /* constant */ XtResourceString,/* resource name string */ XtResourceQuark, /* resource name quark */ XtWidgetBaseOffset,/* offset */ XtProcedureArg /* procedure to call */ } XtAddressMode; typedef struct { XtAddressMode address_mode; XtPointer address_id; Cardinal size; } XtConvertArgRec, *XtConvertArgList; |__ The size field specifies the length of the data in bytes. The address_mode field specifies how the address_id field should be interpreted. XtAddress causes address_id to be interpreted as the address of the data. XtBaseOffset causes address_id to be interpreted as the offset from the widget base. XtImmediate causes address_id to be interpreted as a constant. XtResourceString causes address_id to be inter- preted as the name of a resource that is to be converted into an offset from the widget base. XtResourceQuark causes address_id to be interpreted as the result of an XrmString- ToQuark conversion on the name of a resource, which is to be converted into an offset from the widget base. XtWidget- BaseOffset is similar to XtBaseOffset except that it searches for the closest windowed ancestor if the object is not of a subclass of Core (see Chapter 12). XtProcedureArg specifies that address_id is a pointer to a procedure to be invoked to return the conversion argument. If XtProce- dureArg is specified, address_id must contain the address of a function of type XtConvertArgProc. 242 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtConvertArgProc)(Widget, Cardinal*, XrmValue*); Widget object; Cardinal *size; XrmValue *value; object Passes the object for which the resource is being converted, or NULL if the converter was invoked by XtCallConverter or XtDirectConvert. size Passes a pointer to the size field from the XtCon- vertArgRec. value Passes a pointer to a descriptor into which the procedure must store the conversion argument. |__ When invoked, the XtConvertArgProc procedure must derive a conversion argument and store the address and size of the argument in the location pointed to by value. In order to permit reentrancy, the XtConvertArgProc should return the address of storage whose lifetime is no shorter than the lifetime of object. If object is NULL, the life- time of the conversion argument must be no shorter than the lifetime of the resource with which the conversion argument is associated. The Intrinsics do not guarantee to copy this storage but do guarantee not to reference it if the resource is removed from the conversion cache. The following example illustrates how to register the Cvt- StringToPixel routine given earlier: static XtConvertArgRec colorConvertArgs[] = { {XtWidgetBaseOffset, (XtPointer)XtOffset(Widget, core.screen), sizeof(Screen*)}, {XtWidgetBaseOffset, (XtPointer)XtOffset(Widget, core.colormap),sizeof(Colormap)} }; XtSetTypeConverter(XtRString, XtRPixel, CvtStringToPixel, colorConvertArgs, XtNumber(colorConvertArgs), XtCacheByDisplay, NULL); The conversion argument descriptors colorConvertArgs and screenConvertArg are predefined by the Intrinsics. Both take the values from the closest windowed ancestor if the object is not of a subclass of Core. The screenConvertArg descriptor puts the widget's screen field into args[0]. The colorConvertArgs descriptor puts the widget's screen field into args[0], and the widget's colormap field into args[1]. Conversion routines should not just put a descriptor for the address of the base of the widget into args[0], and use that 243 X Toolkit Intrinsics X11 Release 6.4 in the routine. They should pass in the actual values on which the conversion depends. By keeping the dependencies of the conversion procedure specific, it is more likely that subsequent conversions will find what they need in the con- version cache. This way the cache is smaller and has fewer and more widely applicable entries. If any conversion arguments of type XtBaseOffset, XtRe- sourceString, XtResourceQuark, and XtWidgetBaseOffset are specified for conversions performed by XtGetApplicationRe- sources, XtGetSubresources, XtVaGetApplicationResources, or XtVaGetSubresources, the arguments are computed with respect to the specified widget, not the base address or resource list specified in the call. If the XtConvertArgProc modifies the resource database, the changes affect any in-progress widget creation, XtGetAppli- cationResources, or XtGetSubresources in an implementation- defined manner; however, insertion of new entries or changes to existing entries are allowed and will not directly cause an error. 9.6.5. Resource Converter Invocation All resource-fetching routines (for example, XtGetSubre- sources, XtGetApplicationResources, and so on) call resource converters if the resource database or varargs list speci- fies a value that has a different representation from the desired representation or if the widget's default resource value representation is different from the desired represen- tation. To invoke explicit resource conversions, use XtConvertAnd- Store or XtCallConverter. 244 X Toolkit Intrinsics X11 Release 6.4 __ | typedef XtPointer XtCacheRef; Boolean XtCallConverter(display, converter, conversion_args, num_args, from, to_in_out, cache_ref_return) Display* display; XtTypeConverter converter; XrmValuePtr conversion_args; Cardinal num_args; XrmValuePtr from; XrmValuePtr to_in_out; XtCacheRef *cache_ref_return; display Specifies the display with which the conver- sion is to be associated. converter Specifies the conversion procedure to be called. conversion_args Specifies the additional conversion arguments needed to perform the conversion, or NULL. num_args Specifies the number of entries in conver- sion_args. from Specifies a descriptor for the source value. to_in_out Returns the converted value. cache_ref_return Returns a conversion cache id. |__ The XtCallConverter function looks up the specified type converter in the application context associated with the display and, if the converter was not registered or was reg- istered with cache type XtCacheAll or XtCacheByDisplay, looks in the conversion cache to see if this conversion pro- cedure has been called with the specified conversion argu- ments. If so, it checks the success status of the prior call, and if the conversion failed, XtCallConverter returns False immediately; otherwise it checks the size specified in the to argument, and, if it is greater than or equal to the size stored in the cache, copies the information stored in the cache into the location specified by to->addr, stores the cache size into to->size, and returns True. If the size specified in the to argument is smaller than the size stored in the cache, XtCallConverter copies the cache size into to->size and returns False. If the converter was registered with cache type XtCacheNone or no value was found in the conversion cache, XtCallConverter calls the converter, and 245 X Toolkit Intrinsics X11 Release 6.4 if it was not registered with cache type XtCacheNone, enters the result in the cache. XtCallConverter then returns what the converter returned. The cache_ref_return field specifies storage allocated by the caller in which an opaque value will be stored. If the type converter has been registered with the XtCacheRefCount modifier and if the value returned in cache_ref_return is non-NULL, then the caller should store the cache_ref_return value in order to decrement the reference count when the converted value is no longer required. The cache_ref_return argument should be NULL if the caller is unwilling or unable to store the value. To explicitly decrement the reference counts for resources obtained from XtCallConverter, use XtAppReleaseCacheRefs. __ | void XtAppReleaseCacheRefs(app_context, refs) XtAppContext app_context; XtCacheRef *refs; app_context Specifies the application context. refs Specifies the list of cache references to be released. |__ XtAppReleaseCacheRefs decrements the reference count for the conversion entries identified by the refs argument. This argument is a pointer to a NULL-terminated list of XtCacheRef values. If any reference count reaches zero, the destructor, if any, will be called and the resource removed from the conversion cache. As a convenience to clients needing to explicitly decrement reference counts via a callback function, the Intrinsics define two callback procedures, XtCallbackReleaseCacheRef and XtCallbackReleaseCacheRefList. 246 X Toolkit Intrinsics X11 Release 6.4 __ | void XtCallbackReleaseCacheRef(object, client_data, call_data) Widget object; XtPointer client_data; XtPointer call_data; object Specifies the object with which the resource is associated. client_data Specifies the conversion cache entry to be released. call_data Is ignored. |__ This callback procedure may be added to a callback list to release a previously returned XtCacheRef value. When adding the callback, the callback client_data argument must be specified as the value of the XtCacheRef data cast to type XtPointer. __ | void XtCallbackReleaseCacheRefList(object, client_data, call_data) Widget object; XtPointer client_data; XtPointer call_data; object Specifies the object with which the resources are associated. client_data Specifies the conversion cache entries to be released. call_data Is ignored. |__ This callback procedure may be added to a callback list to release a list of previously returned XtCacheRef values. When adding the callback, the callback client_data argument must be specified as a pointer to a NULL-terminated list of XtCacheRef values. To lookup and call a resource converter, copy the resulting value, and free a cached resource when a widget is destroyed, use XtConvertAndStore. 247 X Toolkit Intrinsics X11 Release 6.4 __ | Boolean XtConvertAndStore(object, from_type, from, to_type, to_in_out) Widget object; String from_type; XrmValuePtr from; String to_type; XrmValuePtr to_in_out; object Specifies the object to use for additional argu- ments, if any are needed, and the destroy callback list. Must be of class Object or any subclass thereof. from_type Specifies the source type. from Specifies the value to be converted. to_type Specifies the destination type. to_in_out Specifies a descriptor for storage into which the converted value will be returned. |__ The XtConvertAndStore function looks up the type converter registered to convert from_type to to_type, computes any additional arguments needed, and then calls XtCallConverter (or XtDirectConvert if an old-style converter was registered with XtAddConverter or XtAppAddConverter; see Appendix C) with the from and to_in_out arguments. The to_in_out argu- ment specifies the size and location into which the con- verted value will be stored and is passed directly to the converter. If the location is specified as NULL, it will be replaced with a pointer to private storage and the size will be returned in the descriptor. The caller is expected to copy this private storage immediately and must not modify it in any way. If a non-NULL location is specified, the caller must allocate sufficient storage to hold the converted value and must also specify the size of that storage in the descriptor. The size field will be modified on return to indicate the actual size of the converted data. If the con- version succeeds, XtConvertAndStore returns True; otherwise, it returns False. XtConvertAndStore adds XtCallbackReleaseCacheRef to the destroyCallback list of the specified object if the conver- sion returns an XtCacheRef value. The resulting resource should not be referenced after the object has been destroyed. XtCreateWidget performs processing equivalent to XtConver- tAndStore when initializing the object instance. Because there is extra memory overhead required to implement refer- ence counting, clients may distinguish those objects that 248 X Toolkit Intrinsics X11 Release 6.4 are never destroyed before the application exits from those that may be destroyed and whose resources should be deallo- cated. To specify whether reference counting is to be enabled for the resources of a particular object when the object is cre- ated, the client can specify a value for the Boolean resource XtNinitialResourcesPersistent, class XtCInitialRe- sourcesPersistent. When XtCreateWidget is called, if this resource is not spec- ified as False in either the arglist or the resource database, then the resources referenced by this object are not reference-counted, regardless of how the type converter may have been registered. The effective default value is True; thus clients that expect to destroy one or more objects and want resources deallocated must explicitly spec- ify False for XtNinitialResourcesPersistent. The resources are still freed and destructors called when XtCloseDisplay is called if the conversion was registered as XtCacheByDisplay. 9.7. Reading and Writing Widget State Any resource field in a widget can be read or written by a client. On a write operation, the widget decides what changes it will actually allow and updates all derived fields appropriately. 9.7.1. Obtaining Widget State To retrieve the current values of resources associated with a widget instance, use XtGetValues. 249 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetValues(object, args, num_args) Widget object; ArgList args; Cardinal num_args; object Specifies the object whose resource values are to be returned. Must be of class Object or any sub- class thereof. args Specifies the argument list of name/address pairs that contain the resource names and the addresses into which the resource values are to be stored. The resource names are widget-dependent. num_args Specifies the number of entries in the argument list. |__ The XtGetValues function starts with the resources specified for the Object class and proceeds down the subclass chain to the class of the object. The value field of a passed argu- ment list must contain the address into which to copy the contents of the corresponding object instance field. If the field is a pointer type, the lifetime of the pointed-to data is defined by the object class. For the Intrinsics-defined resources, the following lifetimes apply: o Not valid following any operation that modifies the resource: - XtNchildren resource of composite widgets. - All resources of representation type XtRCallback. o Remain valid at least until the widget is destroyed: - XtNaccelerators, XtNtranslations. o Remain valid until the Display is closed: - XtNscreen. It is the caller's responsibility to allocate and deallocate storage for the copied data according to the size of the resource representation type used within the object. If the class of the object's parent is a subclass of con- straintWidgetClass, XtGetValues then fetches the values for any constraint resources requested. It starts with the con- straint resources specified for constraintWidgetClass and proceeds down the subclass chain to the parent's constraint resources. If the argument list contains a resource name 250 X Toolkit Intrinsics X11 Release 6.4 that is not found in any of the resource lists searched, the value at the corresponding address is not modified. If any get_values_hook procedures in the object's class or super- class records are non-NULL, they are called in superclass- to-subclass order after all the resource values have been fetched by XtGetValues. Finally, if the object's parent is a subclass of constraintWidgetClass, and if any of the par- ent's class or superclass records have declared Constraint- ClassExtension records in the Constraint class part exten- sion field with a record type of NULLQUARK, and if the get_values_hook field in the extension record is non-NULL, XtGetValues calls the get_values_hook procedures in super- class-to-subclass order. This permits a Constraint parent to provide nonresource data via XtGetValues. Get_values_hook procedures may modify the data stored at the location addressed by the value field, including (but not limited to) making a copy of data whose resource representa- tion is a pointer. None of the Intrinsics-defined object classes copy data in this manner. Any operation that modi- fies the queried object resource may invalidate the pointed- to data. To retrieve the current values of resources associated with a widget instance using varargs lists, use XtVaGetValues. __ | void XtVaGetValues(object, ...) Widget object; object Specifies the object whose resource values are to be returned. Must be of class Object or any sub- class thereof. ... Specifies the variable argument list for the resources to be returned. |__ XtVaGetValues is identical in function to XtGetValues with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. All value entries in the list must specify pointers to storage allocated by the caller to which the resource value will be copied. It is the caller's responsibility to ensure that sufficient stor- age is allocated. If XtVaTypedArg is specified, the type argument specifies the representation desired by the caller and the size argument specifies the number of bytes allo- cated to store the result of the conversion. If the size is insufficient, a warning message is issued and the list entry is skipped. 251 X Toolkit Intrinsics X11 Release 6.4 9.7.1.1. Widget Subpart Resource Data: The get_values_hook Procedure Widgets that have subparts can return resource values from them through XtGetValues by supplying a get_values_hook pro- cedure. The get_values_hook procedure pointer is of type XtArgsProc. __ | typedef void (*XtArgsProc)(Widget, ArgList, Cardinal*); Widget w; ArgList args; Cardinal *num_args; w Specifies the widget whose subpart resource values are to be retrieved. args Specifies the argument list that was passed to XtGetValues or the transformed varargs list passed to XtVaGetValues. num_args Specifies the number of entries in the argument list. |__ The widget with subpart resources should call XtGetSubvalues in the get_values_hook procedure and pass in its subresource list and the args and num_args parameters. 9.7.1.2. Widget Subpart State To retrieve the current values of subpart resource data associated with a widget instance, use XtGetSubvalues. For a discussion of subpart resources, see Section 9.4. 252 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetSubvalues(base, resources, num_resources, args, num_args) XtPointer base; XtResourceList resources; Cardinal num_resources; ArgList args; Cardinal num_args; base Specifies the base address of the subpart data structure for which the resources should be retrieved. resources Specifies the subpart resource list. num_resources Specifies the number of entries in the resource list. args Specifies the argument list of name/address pairs that contain the resource names and the addresses into which the resource values are to be stored. num_args Specifies the number of entries in the argument list. |__ The XtGetSubvalues function obtains resource values from the structure identified by base. The value field in each argu- ment entry must contain the address into which to store the corresponding resource value. It is the caller's responsi- bility to allocate and deallocate this storage according to the size of the resource representation type used within the subpart. If the argument list contains a resource name that is not found in the resource list, the value at the corre- sponding address is not modified. To retrieve the current values of subpart resources associ- ated with a widget instance using varargs lists, use XtVaGetSubvalues. 253 X Toolkit Intrinsics X11 Release 6.4 __ | void XtVaGetSubvalues(base, resources, num_resources, ...) XtPointer base; XtResourceList resources; Cardinal num_resources; base Specifies the base address of the subpart data structure for which the resources should be retrieved. resources Specifies the subpart resource list. num_resources Specifies the number of entries in the resource list. ... Specifies a variable argument list of name/address pairs that contain the resource names and the addresses into which the resource values are to be stored. |__ XtVaGetSubvalues is identical in function to XtGetSubvalues with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. XtVaTypedArg is not supported for XtVaGetSubvalues. If XtVaTypedArg is speci- fied in the list, a warning message is issued and the entry is then ignored. 9.7.2. Setting Widget State To modify the current values of resources associated with a widget instance, use XtSetValues. 254 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetValues(object, args, num_args) Widget object; ArgList args; Cardinal num_args; object Specifies the object whose resources are to be modified. Must be of class Object or any subclass thereof. args Specifies the argument list of name/value pairs that contain the resources to be modified and their new values. num_args Specifies the number of entries in the argument list. |__ The XtSetValues function starts with the resources specified for the Object class fields and proceeds down the subclass chain to the object. At each stage, it replaces the object resource fields with any values specified in the argument list. XtSetValues then calls the set_values procedures for the object in superclass-to-subclass order. If the object has any non-NULL set_values_hook fields, these are called immediately after the corresponding set_values procedure. This procedure permits subclasses to set subpart data via XtSetValues. If the class of the object's parent is a subclass of con- straintWidgetClass, XtSetValues also updates the object's constraints. It starts with the constraint resources speci- fied for constraintWidgetClass and proceeds down the sub- class chain to the parent's class. At each stage, it replaces the constraint resource fields with any values specified in the argument list. It then calls the con- straint set_values procedures from constraintWidgetClass down to the parent's class. The constraint set_values pro- cedures are called with widget arguments, as for all set_values procedures, not just the constraint records, so that they can make adjustments to the desired values based on full information about the widget. Any arguments speci- fied that do not match a resource list entry are silently ignored. If the object is of a subclass of RectObj, XtSetValues determines if a geometry request is needed by comparing the old object to the new object. If any geometry changes are required, XtSetValues restores the original geometry and makes the request on behalf of the widget. If the geometry manager returns XtGeometryYes, XtSetValues calls the object's resize procedure. If the geometry manager returns XtGeometryDone, XtSetValues continues, as the object's 255 X Toolkit Intrinsics X11 Release 6.4 resize procedure should have been called by the geometry manager. If the geometry manager returns XtGeometryNo, XtSetValues ignores the geometry request and continues. If the geometry manager returns XtGeometryAlmost, XtSetValues calls the set_values_almost procedure, which determines what should be done. XtSetValues then repeats this process, deciding once more whether the geometry manager should be called. Finally, if any of the set_values procedures returned True, and the widget is realized, XtSetValues causes the widget's expose procedure to be invoked by calling XClearArea on the widget's window. To modify the current values of resources associated with a widget instance using varargs lists, use XtVaSetValues. __ | void XtVaSetValues(object, ...) Widget object; object Specifies the object whose resources are to be modified. Must be of class Object or any subclass thereof. ... Specifies the variable argument list of name/value pairs that contain the resources to be modified and their new values. |__ XtVaSetValues is identical in function to XtSetValues with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. 9.7.2.1. Widget State: The set_values Procedure The set_values procedure pointer in a widget class is of type XtSetValuesFunc. 256 X Toolkit Intrinsics X11 Release 6.4 __ | typedef Boolean (*XtSetValuesFunc)(Widget, Widget, Widget, ArgList, Cardinal*); Widget current; Widget request; Widget new; ArgList args; Cardinal *num_args; current Specifies a copy of the widget as it was before the XtSetValues call. request Specifies a copy of the widget with all values changed as asked for by the XtSetValues call before any class set_values procedures have been called. new Specifies the widget with the new values that are actually allowed. args Specifies the argument list passed to XtSetValues or the transformed argument list passed to XtVaSetValues. num_args Specifies the number of entries in the argument list. |__ The set_values procedure should recompute any field derived from resources that are changed (for example, many GCs depend on foreground and background pixels). If no recompu- tation is necessary, and if none of the resources specific to a subclass require the window to be redisplayed when their values are changed, you can specify NULL for the set_values field in the class record. Like the initialize procedure, set_values mostly deals only with the fields defined in the subclass, but it has to resolve conflicts with its superclass, especially conflicts over width and height. Sometimes a subclass may want to overwrite values filled in by its superclass. In particular, size calculations of a superclass are often incorrect for a subclass, and, in this case, the subclass must modify or recalculate fields declared and computed by its superclass. As an example, a subclass can visually surround its super- class display. In this case, the width and height calcu- lated by the superclass set_values procedure are too small and need to be incremented by the size of the surround. The subclass needs to know if its superclass's size was calcu- lated by the superclass or was specified explicitly. All widgets must place themselves into whatever size is 257 X Toolkit Intrinsics X11 Release 6.4 explicitly given, but they should compute a reasonable size if no size is requested. How does a subclass know the dif- ference between a specified size and a size computed by a superclass? The request and new parameters provide the necessary infor- mation. The request widget is a copy of the widget, updated as originally requested. The new widget starts with the values in the request, but it has additionally been updated by all superclass set_values procedures called so far. A subclass set_values procedure can compare these two to resolve any potential conflicts. The set_values procedure need not refer to the request widget unless it must resolve conflicts between the current and new widgets. Any changes the widget needs to make, including geometry changes, should be made in the new widget. In the above example, the subclass with the visual surround can see if the width and height in the request widget are zero. If so, it adds its surround size to the width and height fields in the new widget. If not, it must make do with the size originally specified. In this case, zero is a special value defined by the class to permit the application to invoke this behavior. The new widget is the actual widget instance record. There- fore, the set_values procedure should do all its work on the new widget; the request widget should never be modified. If the set_values procedure needs to call any routines that operate on a widget, it should specify new as the widget instance. Before calling the set_values procedures, the Intrinsics modify the resources of the request widget according to the contents of the arglist; if the widget names all its resources in the class resource list, it is never necessary to examine the contents of args. Finally, the set_values procedure must return a Boolean that indicates whether the widget needs to be redisplayed. Note that a change in the geometry fields alone does not require the set_values procedure to return True; the X server will eventually generate an Expose event, if necessary. After calling all the set_values procedures, XtSetValues forces a redisplay by calling XClearArea if any of the set_values procedures returned True. Therefore, a set_values procedure should not try to do its own redisplaying. Set_values procedures should not do any work in response to changes in geometry because XtSetValues eventually will per- form a geometry request, and that request might be denied. If the widget actually changes size in response to a call to XtSetValues, its resize procedure is called. Widgets should do any geometry-related work in their resize procedure. 258 X Toolkit Intrinsics X11 Release 6.4 Note that it is permissible to call XtSetValues before a widget is realized. Therefore, the set_values procedure must not assume that the widget is realized. 9.7.2.2. Widget State: The set_values_almost Procedure The set_values_almost procedure pointer in the widget class record is of type XtAlmostProc. __ | typedef void (*XtAlmostProc)(Widget, Widget, XtWidgetGeometry*, XtWidgetGeometry*); Widget old; Widget new; XtWidgetGeometry *request; XtWidgetGeometry *reply; old Specifies a copy of the object as it was before the XtSetValues call. new Specifies the object instance record. request Specifies the original geometry request that was sent to the geometry manager that caused XtGeome- tryAlmost to be returned. reply Specifies the compromise geometry that was returned by the geometry manager with XtGeome- tryAlmost. |__ Most classes inherit the set_values_almost procedure from their superclass by specifying XtInheritSetValuesAlmost in the class initialization. The set_values_almost procedure in rectObjClass accepts the compromise suggested. The set_values_almost procedure is called when a client tries to set a widget's geometry by means of a call to XtSetValues and the geometry manager cannot satisfy the request but instead returns XtGeometryNo or XtGeometryAlmost and a compromise geometry. The new object is the actual instance record. The x, y, width, height, and border_width fields contain the original values as they were before the XtSetValues call, and all other fields contain the new val- ues. The request parameter contains the new geometry request that was made to the parent. The reply parameter contains reply->request_mode equal to zero if the parent returned XtGeometryNo and contains the parent's compromise geometry otherwise. The set_values_almost procedure takes the original geometry and the compromise geometry and deter- mines if the compromise is acceptable or whether to try a different compromise. It returns its results in the request 259 X Toolkit Intrinsics X11 Release 6.4 parameter, which is then sent back to the geometry manager for another try. To accept the compromise, the procedure must copy the contents of the reply geometry into the request geometry; to attempt an alternative geometry, the procedure may modify any part of the request argument; to terminate the geometry negotiation and retain the original geometry, the procedure must set request->request_mode to zero. The geometry fields of the old and new instances must not be modified directly. 9.7.2.3. Widget State: The ConstraintClassPart set_values Procedure The constraint set_values procedure pointer is of type XtSetValuesFunc. The values passed to the parent's con- straint set_values procedure are the same as those passed to the child's class set_values procedure. A class can specify NULL for the set_values field of the ConstraintPart if it need not compute anything. The constraint set_values procedure should recompute any constraint fields derived from constraint resources that are changed. Furthermore, it may modify other widget fields as appropriate. For example, if a constraint for the maximum height of a widget is changed to a value smaller than the widget's current height, the constraint set_values procedure may reset the height field in the widget. 9.7.2.4. Widget Subpart State To set the current values of subpart resources associated with a widget instance, use XtSetSubvalues. For a discus- sion of subpart resources, see Section 9.4. 260 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetSubvalues(base, resources, num_resources, args, num_args) XtPointer base; XtResourceList resources; Cardinal num_resources; ArgList args; Cardinal num_args; base Specifies the base address of the subpart data structure into which the resources should be writ- ten. resources Specifies the subpart resource list. num_resources Specifies the number of entries in the resource list. args Specifies the argument list of name/value pairs that contain the resources to be modified and their new values. num_args Specifies the number of entries in the argument list. |__ The XtSetSubvalues function updates the resource fields of the structure identified by base. Any specified arguments that do not match an entry in the resource list are silently ignored. To set the current values of subpart resources associated with a widget instance using varargs lists, use XtVaSetSub- values. 261 X Toolkit Intrinsics X11 Release 6.4 __ | void XtVaSetSubvalues(base, resources, num_resources, ...) XtPointer base; XtResourceList resources; Cardinal num_resources; base Specifies the base address of the subpart data structure into which the resources should be writ- ten. resources Specifies the subpart resource list. num_resources Specifies the number of entries in the resource list. ... Specifies the variable argument list of name/value pairs that contain the resources to be modified and their new values. |__ XtVaSetSubvalues is identical in function to XtSetSubvalues with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. XtVaTypedArg is not supported for XtVaSetSubvalues. If an entry containing XtVaTypedArg is specified in the list, a warning message is issued and the entry is ignored. 9.7.2.5. Widget Subpart Resource Data: The set_values_hook Procedure Note The set_values_hook procedure is obsolete, as the same information is now available to the set_val- ues procedure. The procedure has been retained for those widgets that used it in versions prior to Release 4. Widgets that have a subpart can set the subpart resource values through XtSetValues by supplying a set_values_hook procedure. The set_values_hook procedure pointer in a wid- get class is of type XtArgsFunc. 262 X Toolkit Intrinsics X11 Release 6.4 __ | typedef Boolean (*XtArgsFunc)(Widget, Arglist, Cardinal*); Widget w; Arglist args; Cardinal *num_args; w Specifies the widget whose subpart resource values are to be changed. args Specifies the argument list that was passed to XtSetValues or the transformed varargs list passed to XtVaSetValues. num_args Specifies the number of entries in the argument list. |__ The widget with subpart resources may call XtSetValues from the set_values_hook procedure and pass in its subresource list and the args and num_args parameters. 263 X Toolkit Intrinsics X11 Release 6.4 Chapter 10 Translation Management Except under unusual circumstances, widgets do not hardwire the mapping of user events into widget behavior by using the event manager. Instead, they provide a default mapping of events into behavior that you can override. The translation manager provides an interface to specify and manage the mapping of X event sequences into widget-supplied functionality, for example, calling procedure Abc when the y key is pressed. The translation manager uses two kinds of tables to perform translations: o The action tables, which are in the widget class struc- ture, specify the mapping of externally available pro- cedure name strings to the corresponding procedure implemented by the widget class. o A translation table, which is in the widget class structure, specifies the mapping of event sequences to procedure name strings. You can override the translation table in the class struc- ture for a specific widget instance by supplying a different translation table for the widget instance. The resources XtNtranslations and XtNbaseTranslations are used to modify the class default translation table; see Section 10.3. 10.1. Action Tables All widget class records contain an action table, an array of XtActionsRec entries. In addition, an application can register its own action tables with the translation manager so that the translation tables it provides to widget instances can access application functionality directly. The translation action procedure pointer is of type XtAc- tionProc. 264 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtActionProc)(Widget, XEvent*, String*, Cardinal*); Widget w; XEvent *event; String *params; Cardinal *num_params; w Specifies the widget that caused the action to be called. event Specifies the event that caused the action to be called. If the action is called after a sequence of events, then the last event in the sequence is used. params Specifies a pointer to the list of strings that were specified in the translation table as argu- ments to the action, or NULL. num_params Specifies the number of entries in params. typedef struct _XtActionsRec { String string; XtActionProc proc; } XtActionsRec, *XtActionList; |__ The string field is the name used in translation tables to access the procedure. The proc field is a pointer to a pro- cedure that implements the functionality. When the action list is specified as the CoreClassPart actions field, the string pointed to by string must be per- manently allocated prior to or during the execution of the class initialization procedure and must not be subsequently deallocated. Action procedures should not assume that the widget in which they are invoked is realized; an accelerator specification can cause an action procedure to be called for a widget that does not yet have a window. Widget writers should also note which of a widget's callback lists are invoked from action procedures and warn clients not to assume the widget is realized in those callbacks. For example, a Pushbutton widget has procedures to take the following actions: o Set the button to indicate it is activated. 265 X Toolkit Intrinsics X11 Release 6.4 o Unset the button back to its normal mode. o Highlight the button borders. o Unhighlight the button borders. o Notify any callbacks that the button has been acti- vated. The action table for the Pushbutton widget class makes these functions available to translation tables written for Push- button or any subclass. The string entry is the name used in translation tables. The procedure entry (usually spelled identically to the string) is the name of the C procedure that implements that function: XtActionsRec actionTable[] = { {"Set", Set}, {"Unset", Unset}, {"Highlight",Highlight}, {"Unhighlight",Unhighlight} {"Notify",Notify}, }; The Intrinsics reserve all action names and parameters starting with the characters ``Xt'' for future standard enhancements. Users, applications, and widgets should not declare action names or pass parameters starting with these characters except to invoke specified built-in Intrinsics functions. 10.1.1. Action Table Registration The actions and num_actions fields of CoreClassPart specify the actions implemented by a widget class. These are auto- matically registered with the Intrinsics when the class is initialized and must be allocated in writable storage prior to Core class_part initialization, and never deallocated. To save memory and optimize access, the Intrinsics may over- write the storage in order to compile the list into an internal representation. To declare an action table within an application and regis- ter it with the translation manager, use XtAppAddActions. 266 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAppAddActions(app_context, actions, num_actions) XtAppContext app_context; XtActionList actions; Cardinal num_actions; app_context Specifies the application context. actions Specifies the action table to register. num_actions Specifies the number of entries in this action table. |__ If more than one action is registered with the same name, the most recently registered action is used. If duplicate actions exist in an action table, the first is used. The Intrinsics register an action table containing XtMenuPopup and XtMenuPopdown as part of XtCreateApplicationContext. 10.1.2. Action Names to Procedure Translations The translation manager uses a simple algorithm to resolve the name of a procedure specified in a translation table into the actual procedure specified in an action table. When the widget is realized, the translation manager per- forms a search for the name in the following tables, in order: o The widget's class and all superclass action tables, in subclass-to-superclass order. o The parent's class and all superclass action tables, in subclass-to-superclass order, then on up the ancestor tree. o The action tables registered with XtAppAddActions and XtAddActions from the most recently added table to the oldest table. As soon as it finds a name, the translation manager stops the search. If it cannot find a name, the translation man- ager generates a warning message. 10.1.3. Action Hook Registration An application can specify a procedure that will be called just before every action routine is dispatched by the trans- lation manager. To do so, the application supplies a 267 X Toolkit Intrinsics X11 Release 6.4 procedure pointer of type XtActionHookProc. __ | typedef void (*XtActionHookProc)(Widget, XtPointer, String, XEvent*, String*, Cardinal*); Widget w; XtPointer client_data; String action_name; XEvent* event; String* params; Cardinal* num_params; w Specifies the widget whose action is about to be dispatched. client_data Specifies the application-specific closure that was passed to XtAppAddActionHook. action_name Specifies the name of the action to be dispatched. event Specifies the event argument that will be passed to the action routine. params Specifies the action parameters that will be passed to the action routine. num_params Specifies the number of entries in params. |__ Action hooks should not modify any of the data pointed to by the arguments other than the client_data argument. To add an action hook, use XtAppAddActionHook. 268 X Toolkit Intrinsics X11 Release 6.4 __ | XtActionHookId XtAppAddActionHook(app, proc, client_data) XtAppContext app; XtActionHookProc proc; XtPointer client_data; app Specifies the application context. proc Specifies the action hook procedure. client_data Specifies application-specific data to be passed to the action hook. |__ XtAppAddActionHook adds the specified procedure to the front of a list maintained in the application context. In the future, when an action routine is about to be invoked for any widget in this application context, either through the translation manager or via XtCallActionProc, the action hook procedures will be called in reverse order of registration just prior to invoking the action routine. Action hook procedures are removed automatically and the XtActionHookIdis destroyed when the application context in which they were added is destroyed. To remove an action hook procedure without destroying the application context, use XtRemoveActionHook. __ | void XtRemoveActionHook(id) XtActionHookId id; id Specifies the action hook id returned by XtAppAd- dActionHook. |__ XtRemoveActionHook removes the specified action hook proce- dure from the list in which it was registered. 10.2. Translation Tables All widget instance records contain a translation table, which is a resource with a default value specified elsewhere in the class record. A translation table specifies what action procedures are invoked for an event or a sequence of events. A translation table is a string containing a list of translations from an event sequence into one or more 269 X Toolkit Intrinsics X11 Release 6.4 action procedure calls. The translations are separated from one another by newline characters (ASCII LF). The complete syntax of translation tables is specified in Appendix B. As an example, the default behavior of Pushbutton is o Highlight on enter window. o Unhighlight on exit window. o Invert on left button down. o Call callbacks and reinvert on left button up. The following illustrates Pushbutton's default translation table: static String defaultTranslations = ":Highlight()\n\ :Unhighlight()\n\ :Set()\n\ : Notify() Unset()"; The tm_table field of the CoreClassPart should be filled in at class initialization time with the string containing the class's default translations. If a class wants to inherit its superclass's translations, it can store the special value XtInheritTranslations into tm_table. In Core's class part initialization procedure, the Intrinsics compile this translation table into an efficient internal form. Then, at widget creation time, this default translation table is com- bined with the XtNtranslations and XtNbaseTranslations resources; see Section 10.3. The resource conversion mechanism automatically compiles string translation tables that are specified in the resource database. If a client uses translation tables that are not retrieved via a resource conversion, it must compile them itself using XtParseTranslationTable. The Intrinsics use the compiled form of the translation table to register the necessary events with the event man- ager. Widgets need do nothing other than specify the action and translation tables for events to be processed by the translation manager. 10.2.1. Event Sequences An event sequence is a comma-separated list of X event descriptions that describes a specific sequence of X events to map to a set of program actions. Each X event 270 X Toolkit Intrinsics X11 Release 6.4 description consists of three parts: The X event type, a prefix consisting of the X modifier bits, and an event-spe- cific suffix. Various abbreviations are supported to make translation tables easier to read. The events must match incoming events in left-to-right order to trigger the action sequence. 10.2.2. Action Sequences Action sequences specify what program or widget actions to take in response to incoming X events. An action sequence consists of space-separated action procedure call specifica- tions. Each action procedure call consists of the name of an action procedure and a parenthesized list of zero or more comma-separated string parameters to pass to that procedure. The actions are invoked in left-to-right order as specified in the action sequence. 10.2.3. Multi-Click Time Translation table entries may specify actions that are taken when two or more identical events occur consecutively within a short time interval, called the multi-click time. The multi-click time value may be specified as an application resource with name ``multiClickTime'' and class ``Mul- tiClickTime'' and may also be modified dynamically by the application. The multi-click time is unique for each Dis- play value and is retrieved from the resource database by XtDisplayInitialize. If no value is specified, the initial value is 200 milliseconds. To set the multi-click time dynamically, use XtSetMul- tiClickTime. __ | void XtSetMultiClickTime(display, time) Display *display; int time; display Specifies the display connection. time Specifies the multi-click time in milliseconds. |__ XtSetMultiClickTime sets the time interval used by the translation manager to determine when multiple events are interpreted as a repeated event. When a repeat count is 271 X Toolkit Intrinsics X11 Release 6.4 specified in a translation entry, the interval between the timestamps in each pair of repeated events (e.g., between two ButtonPress events) must be less than the multi-click time in order for the translation actions to be taken. To read the multi-click time, use XtGetMultiClickTime. __ | int XtGetMultiClickTime(display) Display *display; display Specifies the display connection. |__ XtGetMultiClickTime returns the time in milliseconds that the translation manager uses to determine if multiple events are to be interpreted as a repeated event for purposes of matching a translation entry containing a repeat count. 10.3. Translation Table Management Sometimes an application needs to merge its own translations with a widget's translations. For example, a window manager provides functions to move a window. The window manager wishes to bind this operation to a specific pointer button in the title bar without the possibility of user override and bind it to other buttons that may be overridden by the user. To accomplish this, the window manager should first create the title bar and then should merge the two translation tables into the title bar's translations. One translation table contains the translations that the window manager wants only if the user has not specified a translation for a particular event or event sequence (i.e., those that may be overridden). The other translation table contains the translations that the window manager wants regardless of what the user has specified. Three Intrinsics functions support this merging: XtParseTransla- Compiles a translation table. tionTable XtAugmentTransla- Merges a compiled translation table tions into a widget's compiled translation table, ignoring any new translations that conflict with existing transla- tions. 272 X Toolkit Intrinsics X11 Release 6.4 XtOverrideTransla- Merges a compiled translation table tions into a widget's compiled translation table, replacing any existing trans- lations that conflict with new trans- lations. To compile a translation table, use XtParseTranslationTable. __ | XtTranslations XtParseTranslationTable(table) String table; table Specifies the translation table to compile. |__ The XtParseTranslationTable function compiles the transla- tion table, provided in the format given in Appendix B, into an opaque internal representation of type XtTranslations. Note that if an empty translation table is required for any purpose, one can be obtained by calling XtParseTransla- tionTable and passing an empty string. To merge additional translations into an existing transla- tion table, use XtAugmentTranslations. __ | void XtAugmentTranslations(w, translations) Widget w; XtTranslations translations; w Specifies the widget into which the new transla- tions are to be merged. Must be of class Core or any subclass thereof. translations Specifies the compiled translation table to merge in. |__ The XtAugmentTranslations function merges the new transla- tions into the existing widget translations, ignoring any #replace, #augment, or #override directive that may have been specified in the translation string. The translation table specified by translations is not altered by this pro- cess. XtAugmentTranslations logically appends the string representation of the new translations to the string repre- sentation of the widget's current translations and reparses 273 X Toolkit Intrinsics X11 Release 6.4 the result with no warning messages about duplicate left- hand sides, then stores the result back into the widget instance; i.e., if the new translations contain an event or event sequence that already exists in the widget's transla- tions, the new translation is ignored. To overwrite existing translations with new translations, use XtOverrideTranslations. __ | void XtOverrideTranslations(w, translations) Widget w; XtTranslations translations; w Specifies the widget into which the new transla- tions are to be merged. Must be of class Core or any subclass thereof. translations Specifies the compiled translation table to merge in. |__ The XtOverrideTranslations function merges the new transla- tions into the existing widget translations, ignoring any #replace, #augment, or #override directive that may have been specified in the translation string. The translation table specified by translations is not altered by this pro- cess. XtOverrideTranslations logically appends the string representation of the widget's current translations to the string representation of the new translations and reparses the result with no warning messages about duplicate left- hand sides, then stores the result back into the widget instance; i.e., if the new translations contain an event or event sequence that already exists in the widget's transla- tions, the new translation overrides the widget's transla- tion. To replace a widget's translations completely, use XtSetVal- ues on the XtNtranslations resource and specify a compiled translation table as the value. To make it possible for users to easily modify translation tables in their resource files, the string-to-translation- table resource type converter allows the string to specify whether the table should replace, augment, or override any existing translation table in the widget. To specify this, a pound sign (#) is given as the first character of the table followed by one of the keywords ``replace'', ``aug- ment'', or ``override'' to indicate whether to replace, 274 X Toolkit Intrinsics X11 Release 6.4 augment, or override the existing table. The replace or merge operation is performed during the Core instance ini- tialization. Each merge operation produces a new transla- tion resource value; if the original tables were shared by other widgets, they are unaffected. If no directive is specified, ``#replace'' is assumed. At instance initialization the XtNtranslations resource is first fetched. Then, if it was not specified or did not contain ``#replace'', the resource database is searched for the resource XtNbaseTranslations. If XtNbaseTranslations is found, it is merged into the widget class translation table. Then the widget translations field is merged into the result or into the class translation table if XtNbaseTranslations was not found. This final table is then stored into the widget translations field. If the XtNtranslations resource specified ``#replace'', no merge is done. If neither XtNbaseTranslations or XtNtranslations are specified, the class translation table is copied into the widget instance. To completely remove existing translations, use XtUninstall- Translations. __ | void XtUninstallTranslations(w) Widget w; w Specifies the widget from which the translations are to be removed. Must be of class Core or any subclass thereof. |__ The XtUninstallTranslations function causes the entire translation table for the widget to be removed. 10.4. Using Accelerators It is often desirable to be able to bind events in one wid- get to actions in another. In particular, it is often use- ful to be able to invoke menu actions from the keyboard. The Intrinsics provide a facility, called accelerators, that lets you accomplish this. An accelerator table is a trans- lation table that is bound with its actions in the context of a particular widget, the source widget. The accelerator table can then be installed on one or more destination wid- gets. When an event sequence in the destination widget would cause an accelerator action to be taken, and if the source widget is sensitive, the actions are executed as though triggered by the same event sequence in the accelera- tor source widget. The event is passed to the action 275 X Toolkit Intrinsics X11 Release 6.4 procedure without modification. The action procedures used within accelerators must not assume that the source widget is realized nor that any fields of the event are in refer- ence to the source widget's window if the widget is real- ized. Each widget instance contains that widget's exported accel- erator table as a resource. Each class of widget exports a method that takes a displayable string representation of the accelerators so that widgets can display their current accelerators. The representation is the accelerator table in canonical translation table form (see Appendix B). The display_accelerator procedure pointer is of type XtString- Proc. __ | typedef void (*XtStringProc)(Widget, String); Widget w; String string; w Specifies the source widget that supplied the accelerators. string Specifies the string representation of the accel- erators for this widget. |__ Accelerators can be specified in resource files, and the string representation is the same as for a translation table. However, the interpretation of the #augment and #override directives applies to what will happen when the accelerator is installed; that is, whether or not the accel- erator translations will override the translations in the destination widget. The default is #augment, which means that the accelerator translations have lower priority than the destination translations. The #replace directive is ignored for accelerator tables. To parse an accelerator table, use XtParseAcceleratorTable. __ | XtAccelerators XtParseAcceleratorTable(source) String source; source Specifies the accelerator table to compile. |__ The XtParseAcceleratorTable function compiles the accelera- tor table into an opaque internal representation. The 276 X Toolkit Intrinsics X11 Release 6.4 client should set the XtNaccelerators resource of each wid- get that is to be activated by these translations to the returned value. To install accelerators from a widget on another widget, use XtInstallAccelerators. __ | void XtInstallAccelerators(destination, source) Widget destination; Widget source; destination Specifies the widget on which the accelerators are to be installed. Must be of class Core or any subclass thereof. source Specifies the widget from which the accelerators are to come. Must be of class Core or any sub- class thereof. |__ The XtInstallAccelerators function installs the accelerators resource value from source onto destination by merging the source accelerators into the destination translations. If the source display_accelerator field is non-NULL, XtInstal- lAccelerators calls it with the source widget and a string representation of the accelerator table, which indicates that its accelerators have been installed and that it should display them appropriately. The string representation of the accelerator table is its canonical translation table representation. As a convenience for installing all accelerators from a wid- get and all its descendants onto one destination, use XtIn- stallAllAccelerators. 277 X Toolkit Intrinsics X11 Release 6.4 __ | void XtInstallAllAccelerators(destination, source) Widget destination; Widget source; destination Specifies the widget on which the accelerators are to be installed. Must be of class Core or any subclass thereof. source Specifies the root widget of the widget tree from which the accelerators are to come. Must be of class Core or any subclass thereof. |__ The XtInstallAllAccelerators function recursively descends the widget tree rooted at source and installs the accelera- tors resource value of each widget encountered onto destina- tion. A common use is to call XtInstallAllAccelerators and pass the application main window as the source. 10.5. KeyCode-to-KeySym Conversions The translation manager provides support for automatically translating KeyCodes in incoming key events into KeySyms. KeyCode-to-KeySym translator procedure pointers are of type XtKeyProc. 278 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtKeyProc)(Display*, KeyCode, Modifiers, Modifiers*, KeySym*); Display *display; KeyCode keycode; Modifiers modifiers; Modifiers *modifiers_return; KeySym *keysym_return; display Specifies the display that the KeyCode is from. keycode Specifies the KeyCode to translate. modifiers Specifies the modifiers to the KeyCode. modifiers_return Specifies a location in which to store a mask that indicates the subset of all modifiers that are examined by the key translator for the speci- fied keycode. keysym_return Specifies a location in which to store the resulting KeySym. |__ This procedure takes a KeyCode and modifiers and produces a KeySym. For any given key translator function and keyboard encoding, modifiers_return will be a constant per KeyCode that indicates the subset of all modifiers that are examined by the key translator for that KeyCode. The KeyCode-to-KeySym translator procedure must be imple- mented such that multiple calls with the same display, key- code, and modifiers return the same result until either a new case converter, an XtCaseProc, is installed or a Map- pingNotify event is received. The Intrinsics maintain tables internally to map KeyCodes to KeySyms for each open display. Translator procedures and other clients may share a single copy of this table to per- form the same mapping. To return a pointer to the KeySym-to-KeyCode mapping table for a particular display, use XtGetKeysymTable. 279 X Toolkit Intrinsics X11 Release 6.4 __ | KeySym *XtGetKeysymTable(display, min_keycode_return, keysyms_per_keycode_return) Display *display; KeyCode *min_keycode_return; int *keysyms_per_keycode_return; display Specifies the display whose table is required. min_keycode_return Returns the minimum KeyCode valid for the display. keysyms_per_keycode_return Returns the number of KeySyms stored for each Key- Code. |__ XtGetKeysymTable returns a pointer to the Intrinsics' copy of the server's KeyCode-to-KeySym table. This table must not be modified. There are keysyms_per_keycode_return KeySyms associated with each KeyCode, located in the table with indices starting at index (test_keycode - min_keycode_return) * keysyms_per_keycode_return for KeyCode test_keycode. Any entries that have no KeySyms associated with them contain the value NoSymbol. Clients should not cache the KeySym table but should call XtGetKeysymTable each time the value is needed, as the table may change prior to dispatching each event. For more information on this table, see Section 12.7 in Xlib -- C Language X Interface. To register a key translator, use XtSetKeyTranslator. __ | void XtSetKeyTranslator(display, proc) Display *display; XtKeyProc proc; display Specifies the display from which to translate the events. proc Specifies the procedure to perform key transla- tions. |__ The XtSetKeyTranslator function sets the specified procedure as the current key translator. The default translator is 280 X Toolkit Intrinsics X11 Release 6.4 XtTranslateKey, an XtKeyProc that uses the Shift, Lock, num- lock, and group modifiers with the interpretations defined in X Window System Protocol, Section 5. It is provided so that new translators can call it to get default KeyCode-to- KeySym translations and so that the default translator can be reinstalled. To invoke the currently registered KeyCode-to-KeySym trans- lator, use XtTranslateKeycode. __ | void XtTranslateKeycode(display, keycode, modifiers, modifiers_return, keysym_return) Display *display; KeyCode keycode; Modifiers modifiers; Modifiers *modifiers_return; KeySym *keysym_return; display Specifies the display that the KeyCode is from. keycode Specifies the KeyCode to translate. modifiers Specifies the modifiers to the KeyCode. modifiers_return Returns a mask that indicates the modifiers actu- ally used to generate the KeySym. keysym_return Returns the resulting KeySym. |__ The XtTranslateKeycode function passes the specified argu- ments directly to the currently registered KeyCode-to-KeySym translator. To handle capitalization of nonstandard KeySyms, the Intrin- sics allow clients to register case conversion routines. Case converter procedure pointers are of type XtCaseProc. 281 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtCaseProc)(Display*, KeySym, KeySym*, KeySym*); Display *display; KeySym keysym; KeySym *lower_return; KeySym *upper_return; display Specifies the display connection for which the conversion is required. keysym Specifies the KeySym to convert. lower_return Specifies a location into which to store the low- ercase equivalent for the KeySym. upper_return Specifies a location into which to store the uppercase equivalent for the KeySym. |__ If there is no case distinction, this procedure should store the KeySym into both return values. To register a case converter, use XtRegisterCaseConverter. __ | void XtRegisterCaseConverter(display, proc, start, stop) Display *display; XtCaseProc proc; KeySym start; KeySym stop; display Specifies the display from which the key events are to come. proc Specifies the XtCaseProc to do the conversions. start Specifies the first KeySym for which this con- verter is valid. stop Specifies the last KeySym for which this converter is valid. |__ The XtRegisterCaseConverter registers the specified case converter. The start and stop arguments provide the inclu- sive range of KeySyms for which this converter is to be called. The new converter overrides any previous converters for KeySyms in that range. No interface exists to remove 282 X Toolkit Intrinsics X11 Release 6.4 converters; you need to register an identity converter. When a new converter is registered, the Intrinsics refresh the keyboard state if necessary. The default converter understands case conversion for all Latin KeySyms defined in X Window System Protocol, Appendix A. To determine uppercase and lowercase equivalents for a KeySym, use XtConvertCase. __ | void XtConvertCase(display, keysym, lower_return, upper_return) Display *display; KeySym keysym; KeySym *lower_return; KeySym *upper_return; display Specifies the display that the KeySym came from. keysym Specifies the KeySym to convert. lower_return Returns the lowercase equivalent of the KeySym. upper_return Returns the uppercase equivalent of the KeySym. |__ The XtConvertCase function calls the appropriate converter and returns the results. A user-supplied XtKeyProc may need to use this function. 10.6. Obtaining a KeySym in an Action Procedure When an action procedure is invoked on a KeyPress or KeyRe- lease event, it often has a need to retrieve the KeySym and modifiers corresponding to the event that caused it to be invoked. In order to avoid repeating the processing that was just performed by the Intrinsics to match the transla- tion entry, the KeySym and modifiers are stored for the duration of the action procedure and are made available to the client. To retrieve the KeySym and modifiers that matched the final event specification in the translation table entry, use XtGetActionKeysym. 283 X Toolkit Intrinsics X11 Release 6.4 __ | KeySym XtGetActionKeysym(event, modifiers_return) XEvent *event; Modifiers *modifiers_return; event Specifies the event pointer passed to the action procedure by the Intrinsics. modifiers_return Returns the modifiers that caused the match, if non-NULL. |__ If XtGetActionKeysym is called after an action procedure has been invoked by the Intrinsics and before that action proce- dure returns, and if the event pointer has the same value as the event pointer passed to that action routine, and if the event is a KeyPress or KeyRelease event, then XtGetAction- Keysym returns the KeySym that matched the final event spec- ification in the translation table and, if modifiers_return is non-NULL, the modifier state actually used to generate this KeySym; otherwise, if the event is a KeyPress or KeyRe- lease event, then XtGetActionKeysym calls XtTranslateKeycode and returns the results; else it returns NoSymbol and does not examine modifiers_return. Note that if an action procedure invoked by the Intrinsics invokes a subsequent action procedure (and so on) via XtCallActionProc, the nested action procedure may also call XtGetActionKeysym to retrieve the Intrinsics' KeySym and modifiers. 10.7. KeySym-to-KeyCode Conversions To return the list of KeyCodes that map to a particular KeySym in the keyboard mapping table maintained by the Intrinsics, use XtKeysymToKeycodeList. 284 X Toolkit Intrinsics X11 Release 6.4 __ | void XtKeysymToKeycodeList(display, keysym, keycodes_return, keycount_return) Display *display; KeySym keysym; KeyCode **keycodes_return; Cardinal *keycount_return; display Specifies the display whose table is required. keysym Specifies the KeySym for which to search. keycodes_return Returns a list of KeyCodes that have keysym associated with them, or NULL if keycount_return is 0. keycount_return Returns the number of KeyCodes in the keycode list. |__ The XtKeysymToKeycodeList procedure returns all the KeyCodes that have keysym in their entry for the keyboard mapping table associated with display. For each entry in the table, the first four KeySyms (groups 1 and 2) are interpreted as specified by X Window System Protocol, Section 5. If no KeyCodes map to the specified KeySym, keycount_return is zero and *keycodes_return is NULL. The caller should free the storage pointed to by key- codes_return using XtFree when it is no longer useful. If the caller needs to examine the KeyCode-to-KeySym table for a particular KeyCode, it should call XtGetKeysymTable. 10.8. Registering Button and Key Grabs for Actions To register button and key grabs for a widget's window according to the event bindings in the widget's translation table, use XtRegisterGrabAction. 285 X Toolkit Intrinsics X11 Release 6.4 __ | void XtRegisterGrabAction(action_proc, owner_events, event_mask, pointer_mode, keyboard_mode) XtActionProc action_proc; Boolean owner_events; unsigned int event_mask; int pointer_mode, keyboard_mode; action_proc Specifies the action procedure to search for in translation tables. owner_events event_mask pointer_mode keyboard_mode Specify arguments to XtGrabButton or XtGrabKey. |__ XtRegisterGrabAction adds the specified action_proc to a list known to the translation manager. When a widget is realized, or when the translations of a realized widget or the accelerators installed on a realized widget are modi- fied, its translation table and any installed accelerators are scanned for action procedures on this list. If any are invoked on ButtonPress or KeyPress events as the only or final event in a sequence, the Intrinsics will call XtGrab- Button or XtGrabKey for the widget with every button or Key- Code which maps to the event detail field, passing the spec- ified owner_events, event_mask, pointer_mode, and key- board_mode. For ButtonPress events, the modifiers specified in the grab are determined directly from the translation specification and confine_to and cursor are specified as None. For KeyPress events, if the translation table entry specifies colon (:) in the modifier list, the modifiers are determined by calling the key translator procedure regis- tered for the display and calling XtGrabKey for every combi- nation of standard modifiers which map the KeyCode to the specified event detail KeySym, and ORing any modifiers spec- ified in the translation table entry, and event_mask is ignored. If the translation table entry does not specify colon in the modifier list, the modifiers specified in the grab are those specified in the translation table entry only. For both ButtonPress and KeyPress events, don't-care modifiers are ignored unless the translation entry explic- itly specifies ``Any'' in the modifiers field. If the specified action_proc is already registered for the calling process, the new values will replace the previously specified values for any widgets that become realized fol- lowing the call, but existing grabs are not altered on cur- rently realized widgets. 286 X Toolkit Intrinsics X11 Release 6.4 When translations or installed accelerators are modified for a realized widget, any previous key or button grabs regis- tered as a result of the old bindings are released if they do not appear in the new bindings and are not explicitly grabbed by the client with XtGrabKey or XtGrabButton. 10.9. Invoking Actions Directly Normally action procedures are invoked by the Intrinsics when an event or event sequence arrives for a widget. To invoke an action procedure directly, without generating (or synthesizing) events, use XtCallActionProc. __ | void XtCallActionProc(widget, action, event, params, num_params) Widget widget; String action; XEvent *event; String *params; Cardinal num_params; widget Specifies the widget in which the action is to be invoked. Must be of class Core or any subclass thereof. action Specifies the name of the action routine. event Specifies the contents of the event passed to the action routine. params Specifies the contents of the params passed to the action routine. num_params Specifies the number of entries in params. |__ XtCallActionProc searches for the named action routine in the same manner and order as translation tables are bound, as described in Section 10.1.2, except that application action tables are searched, if necessary, as of the time of the call to XtCallActionProc. If found, the action routine is invoked with the specified widget, event pointer, and parameters. It is the responsibility of the caller to ensure that the contents of the event, params, and num_params arguments are appropriate for the specified action routine and, if necessary, that the specified widget is realized or sensitive. If the named action routine can- not be found, XtCallActionProc generates a warning message and returns. 287 X Toolkit Intrinsics X11 Release 6.4 10.10. Obtaining a Widget's Action List Occasionally a subclass will require the pointers to one or more of its superclass's action procedures. This would be needed, for example, in order to envelop the superclass's action. To retrieve the list of action procedures regis- tered in the superclass's actions field, use XtGetAction- List. __ | void XtGetActionList(widget_class, actions_return, num_actions_return) WidgetClass widget_class; XtActionList *actions_return; Cardinal *num_actions_return; widget_class Specifies the widget class whose actions are to be returned. actions_return Returns the action list. num_actions_return Returns the number of action procedures declared by the class. |__ XtGetActionList returns the action table defined by the specified widget class. This table does not include actions defined by the superclasses. If widget_class is not ini- tialized, or is not coreWidgetClass or a subclass thereof, or if the class does not define any actions, *actions_return will be NULL and *num_actions_return will be zero. If *actions_return is non-NULL the client is responsible for freeing the table using XtFree when it is no longer needed. 288 X Toolkit Intrinsics X11 Release 6.4 Chapter 11 Utility Functions The Intrinsics provide a number of utility functions that you can use to o Determine the number of elements in an array. o Translate strings to widget instances. o Manage memory usage. o Share graphics contexts. o Manipulate selections. o Merge exposure events into a region. o Translate widget coordinates. o Locate a widget given a window id. o Handle errors. o Set the WM_COLORMAP_WINDOWS property. o Locate files by name with string substitutions. o Register callback functions for external agents. o Locate all the displays of an application context. 11.1. Determining the Number of Elements in an Array To determine the number of elements in a fixed-size array, use XtNumber. __ | Cardinal XtNumber(array) ArrayType array; array Specifies a fixed-size array of arbitrary type. |__ The XtNumber macro returns the number of elements allocated to the array. 289 X Toolkit Intrinsics X11 Release 6.4 11.2. Translating Strings to Widget Instances To translate a widget name to a widget instance, use XtName- ToWidget. __ | Widget XtNameToWidget(reference, names) Widget reference; String names; reference Specifies the widget from which the search is to start. Must be of class Core or any subclass thereof. names Specifies the partially qualified name of the desired widget. |__ The XtNameToWidget function searches for a descendant of the reference widget whose name matches the specified names. The names parameter specifies a simple object name or a series of simple object name components separated by periods or asterisks. XtNameToWidget returns the descendant with the shortest name matching the specification according to the following rules, where child is either a pop-up child or a normal child if the widget's class is a subclass of Com- posite : o Enumerate the object subtree rooted at the reference widget in breadth-first order, qualifying the name of each object with the names of all its ancestors up to, but not including, the reference widget. The ordering between children of a common parent is not defined. o Return the first object in the enumeration that matches the specified name, where each component of names matches exactly the corresponding component of the qualified object name and asterisk matches any series of components, including none. o If no match is found, return NULL. Since breadth-first traversal is specified, the descendant with the shortest matching name (i.e., the fewest number of components), if any, will always be returned. However, since the order of enumeration of children is undefined and since the Intrinsics do not require that all children of a widget have unique names, XtNameToWidget may return any child that matches if there are multiple objects in the sub- tree with the same name. Consecutive separators (periods or asterisks) including at least one asterisk are treated as a single asterisk. Consecutive periods are treated as a 290 X Toolkit Intrinsics X11 Release 6.4 single period. 11.3. Managing Memory Usage The Intrinsics memory management functions provide uniform checking for null pointers and error reporting on memory allocation errors. These functions are completely compati- ble with their standard C language runtime counterparts mal- loc, calloc, realloc, and free with the following added functionality: o XtMalloc, XtCalloc, and XtRealloc give an error if there is not enough memory. o XtFree simply returns if passed a NULL pointer. o XtRealloc simply allocates new storage if passed a NULL pointer. See the standard C library documentation on malloc, calloc, realloc, and free for more information. To allocate storage, use XtMalloc. __ | char *XtMalloc(size) Cardinal size; size Specifies the number of bytes desired. |__ The XtMalloc function returns a pointer to a block of stor- age of at least the specified size bytes. If there is insufficient memory to allocate the new block, XtMalloc calls XtErrorMsg. To allocate and initialize an array, use XtCalloc. 291 X Toolkit Intrinsics X11 Release 6.4 __ | char *XtCalloc(num, size) Cardinal num; Cardinal size; num Specifies the number of array elements to allo- cate. size Specifies the size of each array element in bytes. |__ The XtCalloc function allocates space for the specified num- ber of array elements of the specified size and initializes the space to zero. If there is insufficient memory to allo- cate the new block, XtCalloc calls XtErrorMsg. XtCalloc returns the address of the allocated storage. To change the size of an allocated block of storage, use XtRealloc. __ | char *XtRealloc(ptr, num) char *ptr; Cardinal num; ptr Specifies a pointer to the old storage allocated with XtMalloc, XtCalloc, or XtRealloc, or NULL. num Specifies number of bytes desired in new storage. |__ The XtRealloc function changes the size of a block of stor- age, possibly moving it. Then it copies the old contents (or as much as will fit) into the new block and frees the old block. If there is insufficient memory to allocate the new block, XtRealloc calls XtErrorMsg. If ptr is NULL, XtRealloc simply calls XtMalloc. XtRealloc then returns the address of the new block. To free an allocated block of storage, use XtFree. 292 X Toolkit Intrinsics X11 Release 6.4 __ | void XtFree(ptr) char *ptr; ptr Specifies a pointer to a block of storage allo- cated with XtMalloc, XtCalloc, or XtRealloc, or NULL. |__ The XtFree function returns storage, allowing it to be reused. If ptr is NULL, XtFree returns immediately. To allocate storage for a new instance of a type, use XtNew. __ | type *XtNew(type) type t; type Specifies a previously declared type. |__ XtNew returns a pointer to the allocated storage. If there is insufficient memory to allocate the new block, XtNew calls XtErrorMsg. XtNew is a convenience macro that calls XtMalloc with the following arguments specified: ((type *) XtMalloc((unsigned) sizeof(type))) The storage allocated by XtNew should be freed using XtFree. To copy an instance of a string, use XtNewString. __ | String XtNewString(string) String string; string Specifies a previously declared string. |__ XtNewString returns a pointer to the allocated storage. If there is insufficient memory to allocate the new block, XtNewString calls XtErrorMsg. XtNewString is a convenience macro that calls XtMalloc with the following arguments spec- ified: 293 X Toolkit Intrinsics X11 Release 6.4 (strcpy(XtMalloc((unsigned)strlen(str) + 1), str)) The storage allocated by XtNewString should be freed using XtFree. 11.4. Sharing Graphics Contexts The Intrinsics provide a mechanism whereby cooperating objects can share a graphics context (GC), thereby reducing both the number of GCs created and the total number of server calls in any given application. The mechanism is a simple caching scheme and allows for clients to declare both modifiable and nonmodifiable fields of the shared GCs. To obtain a shareable GC with modifiable fields, use XtAllo- cateGC. __ | GC XtAllocateGC(widget, depth, value_mask, values, dynamic_mask, unused_mask) Widget object; Cardinal depth; XtGCMask value_mask; XGCValues *values; XtGCMask dynamic_mask; XtGCMask unused_mask; object Specifies an object, giving the screen for which the returned GC is valid. Must be of class Object or any subclass thereof. depth Specifies the depth for which the returned GC is valid, or 0. value_mask Specifies fields of the GC that are initialized from values. values Specifies the values for the initialized fields. dynamic_mask Specifies fields of the GC that will be modified by the caller. unused_mask Specifies fields of the GC that will not be needed by the caller. |__ The XtAllocateGC function returns a shareable GC that may be modified by the client. The screen field of the specified 294 X Toolkit Intrinsics X11 Release 6.4 widget or of the nearest widget ancestor of the specified object and the specified depth argument supply the root and drawable depths for which the GC is to be valid. If depth is zero, the depth is taken from the depth field of the specified widget or of the nearest widget ancestor of the specified object. The value_mask argument specifies fields of the GC that are initialized with the respective member of the values struc- ture. The dynamic_mask argument specifies fields that the caller intends to modify during program execution. The caller must ensure that the corresponding GC field is set prior to each use of the GC. The unused_mask argument spec- ifies fields of the GC that are of no interest to the caller. The caller may make no assumptions about the con- tents of any fields specified in unused_mask. The caller may assume that at all times all fields not specified in either dynamic_mask or unused_mask have their default value if not specified in value_mask or the value specified by values. If a field is specified in both value_mask and dynamic_mask, the effect is as if it were specified only in dynamic_mask and then immediately set to the value in val- ues. If a field is set in unused_mask and also in either value_mask or dynamic_mask, the specification in unused_mask is ignored. XtAllocateGC tries to minimize the number of unique GCs cre- ated by comparing the arguments with those of previous calls and returning an existing GC when there are no conflicts. XtAllocateGC may modify and return an existing GC if it was allocated with a nonzero unused_mask. To obtain a shareable GC with no modifiable fields, use XtGetGC. 295 X Toolkit Intrinsics X11 Release 6.4 __ | GC XtGetGC(object, value_mask, values) Widget object; XtGCMask value_mask; XGCValues *values; object Specifies an object, giving the screen and depth for which the returned GC is valid. Must be of class Object or any subclass thereof. value_mask Specifies which fields of the values structure are specified. values Specifies the actual values for this GC. |__ The XtGetGC function returns a shareable, read-only GC. The parameters to this function are the same as those for XCre- ateGC except that an Object is passed instead of a Display. XtGetGC is equivalent to XtAllocateGC with depth, dynamic_mask, and unused_mask all zero. XtGetGC shares only GCs in which all values in the GC returned by XCreateGC are the same. In particular, it does not use the value_mask provided to determine which fields of the GC a widget considers relevant. The value_mask is used only to tell the server which fields should be filled in from values and which it should fill in with default values. To deallocate a shared GC when it is no longer needed, use XtReleaseGC. __ | void XtReleaseGC(object, gc) Widget object; GC gc; object Specifies any object on the Display for which the GC was created. Must be of class Object or any subclass thereof. gc Specifies the shared GC obtained with either XtAl- locateGC or XtGetGC. |__ References to shareable GCs are counted and a free request is generated to the server when the last user of a given GC releases it. 296 X Toolkit Intrinsics X11 Release 6.4 11.5. Managing Selections Arbitrary widgets in multiple applications can communicate with each other by means of the Intrinsics global selection mechanism, which conforms to the specifications in the Inter-Client Communication Conventions Manual. The Intrin- sics supply functions for providing and receiving selection data in one logical piece (atomic transfers) or in smaller logical segments (incremental transfers). The incremental interface is provided for a selection owner or selection requestor that cannot or prefers not to pass the selection value to and from the Intrinsics in a single call. For instance, either an application that is running on a machine with limited memory may not be able to store the entire selection value in memory or a selection owner may already have the selection value available in discrete chunks, and it would be more efficient not to have to allo- cate additional storage to copy the pieces contiguously. Any owner or requestor that prefers to deal with the selec- tion value in segments can use the incremental interfaces to do so. The transfer between the selection owner or requestor and the Intrinsics is not required to match the underlying transport protocol between the application and the X server; the Intrinsics will break too large a selec- tion into smaller pieces for transport if necessary and will coalesce a selection transmitted incrementally if the value was requested atomically. 11.5.1. Setting and Getting the Selection Timeout Value To set the Intrinsics selection timeout, use XtAppSetSelec- tionTimeout. __ | void XtAppSetSelectionTimeout(app_context, timeout) XtAppContext app_context; unsigned long timeout; app_context Specifies the application context. timeo|__ Specifies the selection timeout in milliseconds. To get the current selection timeout value, use XtAppGetSe- lectionTimeout. 297 X Toolkit Intrinsics X11 Release 6.4 __ | unsigned long XtAppGetSelectionTimeout(app_context) XtAppContext app_context; app_context Specifies the application context. |__ The XtAppGetSelectionTimeout function returns the current selection timeout value in milliseconds. The selection timeout is the time within which the two communicating applications must respond to one another. The initial time- out value is set by the selectionTimeout application resource as retrieved by XtDisplayInitialize. If selection- Timeout is not specified, the default is five seconds. 11.5.2. Using Atomic Transfers When using atomic transfers, the owner will completely pro- cess one selection request at a time. The owner may con- sider each request individually, since there is no possibil- ity for overlap between evaluation of two requests. 11.5.2.1. Atomic Transfer Procedures The following procedures are used by the selection owner when providing selection data in a single unit. The procedure pointer specified by the owner to supply the selection data to the Intrinsics is of type XtConvertSelec- tionProc. 298 X Toolkit Intrinsics X11 Release 6.4 __ | typedef Boolean (*XtConvertSelectionProc)(Widget, Atom*, Atom*, Atom*, XtPointer*, unsigned long*, int*); Widget w; Atom *selection; Atom *target; Atom *type_return; XtPointer *value_return; unsigned long *length_return; int *format_return; w Specifies the widget that currently owns this selection. selection Specifies the atom naming the selection requested (for example, XA_PRIMARY or XA_SECONDARY). target Specifies the target type of the selection that has been requested, which indicates the desired information about the selection (for example, File Name, Text, Window). type_return Specifies a pointer to an atom into which the property type of the converted value of the selec- tion is to be stored. For instance, either File Name or Text might have property type XA_STRING. value_return Specifies a pointer into which a pointer to the converted value of the selection is to be stored. The selection owner is responsible for allocating this storage. If the selection owner has provided an XtSelectionDoneProc for the selection, this storage is owned by the selection owner; other- wise, it is owned by the Intrinsics selection mechanism, which frees it by calling XtFree when it is done with it. length_return Specifies a pointer into which the number of ele- ments in value_return, each of size indicated by format_return, is to be stored. format_return Specifies a pointer into which the size in bits of the data elements of the selection value is to be stored. |__ This procedure is called by the Intrinsics selection mecha- nism to get the value of a selection as a given type from the current selection owner. It returns True if the owner 299 X Toolkit Intrinsics X11 Release 6.4 successfully converted the selection to the target type or False otherwise. If the procedure returns False, the values of the return arguments are undefined. Each XtConvertSelec- tionProc should respond to target value TARGETS by returning a value containing the list of the targets into which it is prepared to convert the selection. The value returned in format_return must be one of 8, 16, or 32 to allow the server to byte-swap the data if necessary. This procedure does not need to worry about responding to the MULTIPLE or the TIMESTAMP target values (see Section 2.6.2 in the Inter-Client Communication Conventions Manual). A selection request with the MULTIPLE target type is trans- parently transformed into a series of calls to this proce- dure, one for each target type, and a selection request with the TIMESTAMP target value is answered automatically by the Intrinsics using the time specified in the call to XtOwnSe- lection or XtOwnSelectionIncremental. To retrieve the SelectionRequest event that triggered the XtConvertSelectionProc procedure, use XtGetSelectionRequest. __ | XSelectionRequestEvent *XtGetSelectionRequest(w, selection, request_id) Widget w; Atom selection; XtRequestId request_id; w Specifies the widget that currently owns this selection. Must be of class Core or any subclass thereof. selection Specifies the selection being processed. request_id Specifies the requestor id in the case of incre- mental selections, or NULL in the case of atomic transfers. |__ XtGetSelectionRequest may be called only from within an XtConvertSelectionProc procedure and returns a pointer to the SelectionRequest event that caused the conversion proce- dure to be invoked. Request_id specifies a unique id for the individual request in the case that multiple incremental transfers are outstanding. For atomic transfers, request_id must be specified as NULL. If no SelectionRequest event is being processed for the specified widget, selection, and request_id, XtGetSelectionRequest returns NULL. 300 X Toolkit Intrinsics X11 Release 6.4 The procedure pointer specified by the owner when it desires notification upon losing ownership is of type XtLoseSelec- tionProc. __ | typedef void (*XtLoseSelectionProc)(Widget, Atom*); Widget w; Atom *selection; w Specifies the widget that has lost selection own- ership. selection Specifies the atom naming the selection. |__ This procedure is called by the Intrinsics selection mecha- nism to inform the specified widget that it has lost the given selection. Note that this procedure does not ask the widget to relinquish the selection ownership; it is merely informative. The procedure pointer specified by the owner when it desires notification of receipt of the data or when it manages the storage containing the data is of type XtSelectionDoneProc. __ | typedef void (*XtSelectionDoneProc)(Widget, Atom*, Atom*); Widget w; Atom *selection; Atom *target; w Specifies the widget that owns the converted selection. selection Specifies the atom naming the selection that was converted. target Specifies the target type to which the conversion was done. |__ This procedure is called by the Intrinsics selection mecha- nism to inform the selection owner that a selection requestor has successfully retrieved a selection value. If the selection owner has registered an XtSelectionDoneProc, it should expect it to be called once for each conversion that it performs, after the converted value has been suc- cessfully transferred to the requestor. If the selection owner has registered an XtSelectionDoneProc, it also owns 301 X Toolkit Intrinsics X11 Release 6.4 the storage containing the converted selection value. 11.5.2.2. Getting the Selection Value The procedure pointer specified by the requestor to receive the selection data from the Intrinsics is of type XtSelec- tionCallbackProc. __ | typedef void (*XtSelectionCallbackProc)(Widget, XtPointer, Atom*, Atom*, XtPointer, unsigned long*, int*); Widget w; XtPointer client_data; Atom *selection; Atom *type; XtPointer value; unsigned long *length; int *format; w Specifies the widget that requested the selection value. client_data Specifies a value passed in by the widget when it requested the selection. selection Specifies the name of the selection that was requested. type Specifies the representation type of the selection value (for example, XA_STRING). Note that it is not the target that was requested (which the client must remember for itself), but the type that is used to represent the target. The special symbolic constant XT_CONVERT_FAIL is used to indi- cate that the selection conversion failed because the selection owner did not respond within the Intrinsics selection timeout interval. value Specifies a pointer to the selection value. The requesting client owns this storage and is respon- sible for freeing it by calling XtFree when it is done with it. length Specifies the number of elements in value. format Specifies the size in bits of the data in each element of value. |__ This procedure is called by the Intrinsics selection mecha- nism to deliver the requested selection to the requestor. 302 X Toolkit Intrinsics X11 Release 6.4 If the SelectionNotify event returns a property of None, meaning the conversion has been refused because there is no owner for the specified selection or the owner cannot con- vert the selection to the requested target for any reason, the procedure is called with a value of NULL and a length of zero. To obtain the selection value in a single logical unit, use XtGetSelectionValue or XtGetSelectionValues. __ | void XtGetSelectionValue(w, selection, target, callback, client_data, time) Widget w; Atom selection; Atom target; XtSelectionCallbackProc callback; XtPointer client_data; Time time; w Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the particular selection desired; for example, XA_PRIMARY. target Specifies the type of information needed about the selection. callback Specifies the procedure to be called when the selection value has been obtained. Note that this is how the selection value is communicated back to the client. client_data Specifies additional data to be passed to the specified procedure when it is called. time Specifies the timestamp that indicates when the selection request was initiated. This should be the timestamp of the event that triggered this request; the value CurrentTime is not acceptable. |__ The XtGetSelectionValue function requests the value of the selection converted to the target type. The specified call- back is called at some time after XtGetSelectionValue is called, when the selection value is received from the X server. It may be called before or after XtGetSelectionVa- lue returns. For more information about selection, target, and time, see Section 2.6 in the Inter-Client Communication Conventions Manual. 303 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetSelectionValues(w, selection, targets, count, callback, client_data, time) Widget w; Atom selection; Atom *targets; int count; XtSelectionCallbackProc callback; XtPointer *client_data; Time time; w Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the particular selection desired (that is, primary or secondary). targets Specifies the types of information needed about the selection. count Specifies the length of the targets and client_data lists. callback Specifies the callback procedure to be called with each selection value obtained. Note that this is how the selection values are communicated back to the client. client_data Specifies a list of additional data values, one for each target type, that are passed to the call- back procedure when it is called for that target. time Specifies the timestamp that indicates when the selection request was initiated. This should be the timestamp of the event that triggered this request; the value CurrentTime is not acceptable. |__ The XtGetSelectionValues function is similar to multiple calls to XtGetSelectionValue except that it guarantees that no other client can assert ownership between requests and therefore that all the conversions will refer to the same selection value. The callback is invoked once for each tar- get value with the corresponding client data. For more information about selection, target, and time, see Section 2.6 in the Inter-Client Communication Conventions Manual. 11.5.2.3. Setting the Selection Owner To set the selection owner and indicate that the selection value will be provided in one piece, use XtOwnSelection. 304 X Toolkit Intrinsics X11 Release 6.4 __ | Boolean XtOwnSelection(w, selection, time, convert_proc, lose_selection, done_proc) Widget w; Atom selection; Time time; XtConvertSelectionProc convert_proc; XtLoseSelectionProc lose_selection; XtSelectionDoneProc done_proc; w Specifies the widget that wishes to become the owner. Must be of class Core or any subclass thereof. selection Specifies the name of the selection (for example, XA_PRIMARY). time Specifies the timestamp that indicates when the ownership request was initiated. This should be the timestamp of the event that triggered owner- ship; the value CurrentTime is not acceptable. convert_proc Specifies the procedure to be called whenever a client requests the current value of the selec- tion. lose_selection Specifies the procedure to be called whenever the widget has lost selection ownership, or NULL if the owner is not interested in being called back. done_proc Specifies the procedure called after the requestor has received the selection value, or NULL if the owner is not interested in being called back. |__ The XtOwnSelection function informs the Intrinsics selection mechanism that a widget wishes to own a selection. It returns True if the widget successfully becomes the owner and False otherwise. The widget may fail to become the owner if some other widget has asserted ownership at a time later than this widget. The widget can lose selection own- ership either because some other widget asserted later own- ership of the selection or because the widget voluntarily gave up ownership of the selection. The lose_selection pro- cedure is not called if the widget fails to obtain selection ownership in the first place. If a done_proc is specified, the client owns the storage allocated for passing the value to the Intrinsics. If done_proc is NULL, the convert_proc must allocate storage using XtMalloc, XtRealloc, or XtCalloc, and the value speci- fied is freed by the Intrinsics when the transfer is 305 X Toolkit Intrinsics X11 Release 6.4 complete. Usually, a selection owner maintains ownership indefinitely until some other widget requests ownership, at which time the Intrinsics selection mechanism informs the previous owner that it has lost ownership of the selection. However, in response to some user actions (for example, when a user deletes the information selected), the application may wish to explicitly inform the Intrinsics by using XtDisownSelec- tion that it no longer is to be the selection owner. __ | void XtDisownSelection(w, selection, time) Widget w; Atom selection; Time time; w Specifies the widget that wishes to relinquish ownership. selection Specifies the atom naming the selection being given up. time Specifies the timestamp that indicates when the request to relinquish selection ownership was ini- tiated. |__ The XtDisownSelection function informs the Intrinsics selec- tion mechanism that the specified widget is to lose owner- ship of the selection. If the widget does not currently own the selection, either because it lost the selection or because it never had the selection to begin with, XtDisownS- election does nothing. After a widget has called XtDisownSelection, its convert procedure is not called even if a request arrives later with a timestamp during the period that this widget owned the selection. However, its done procedure is called if a con- version that started before the call to XtDisownSelection finishes after the call to XtDisownSelection. 11.5.3. Using Incremental Transfers When using the incremental interface, an owner may have to process more than one selection request for the same selec- tion, converted to the same target, at the same time. The incremental functions take a request_id argument, which is an identifier that is guaranteed to be unique among all incremental requests that are active concurrently. 306 X Toolkit Intrinsics X11 Release 6.4 For example, consider the following: o Upon receiving a request for the selection value, the owner sends the first segment. o While waiting to be called to provide the next segment value but before sending it, the owner receives another request from a different requestor for the same selec- tion value. o To distinguish between the requests, the owner uses the request_id value. This allows the owner to distinguish between the first requestor, which is asking for the second segment, and the second requestor, which is ask- ing for the first segment. 11.5.3.1. Incremental Transfer Procedures The following procedures are used by selection owners who wish to provide the selection data in multiple segments. The procedure pointer specified by the incremental owner to supply the selection data to the Intrinsics is of type XtConvertSelectionIncrProc. 307 X Toolkit Intrinsics X11 Release 6.4 __ | typedef XtPointer XtRequestId; typedef Boolean (*XtConvertSelectionIncrProc)(Widget, Atom*, Atom*, Atom*, XtPointer*, unsigned long*, int*, unsigned long*, XtPointer, XtRequestId*); Widget w; Atom *selection; Atom *target; Atom *type_return; XtPointer *value_return; unsigned long *length_return; int *format_return; unsigned long *max_length; XtPointer client_data; XtRequestId *request_id; w Specifies the widget that currently owns this selection. selection Specifies the atom that names the selection requested. target Specifies the type of information required about the selection. type_return Specifies a pointer to an atom into which the property type of the converted value of the selec- tion is to be stored. value_return Specifies a pointer into which a pointer to the converted value of the selection is to be stored. The selection owner is responsible for allocating this storage. length_return Specifies a pointer into which the number of ele- ments in value_return, each of size indicated by format_return, is to be stored. format_return Specifies a pointer into which the size in bits of the data elements of the selection value is to be stored so that the server may byte-swap the data if necessary. max_length Specifies the maximum number of bytes which may be transferred at any one time. client_data 308 X Toolkit Intrinsics X11 Release 6.4 Specifies the value passed in by the widget when it took ownership of the selection. request_id Specifies an opaque identification for a specific request. |__ This procedure is called repeatedly by the Intrinsics selec- tion mechanism to get the next incremental chunk of data from a selection owner who has called XtOwnSelectionIncre- mental. It must return True if the procedure has succeeded in converting the selection data or False otherwise. On the first call with a particular request id, the owner must begin a new incremental transfer for the requested selection and target. On subsequent calls with the same request id, the owner may assume that the previously supplied value is no longer needed by the Intrinsics; that is, a fixed trans- fer area may be allocated and returned in value_return for each segment to be transferred. This procedure should store a non-NULL value in value_return and zero in length_return to indicate that the entire selection has been delivered. After returning this final segment, the request id may be reused by the Intrinsics to begin a new transfer. To retrieve the SelectionRequest event that triggered the selection conversion procedure, use XtGetSelectionRequest, described in Section 11.5.2.1. The procedure pointer specified by the incremental selection owner when it desires notification upon no longer having ownership is of type XtLoseSelectionIncrProc. __ | typedef void (*XtLoseSelectionIncrProc)(Widget, Atom*, XtPointer); Widget w; Atom *selection; XtPointer client_data; w Specifies the widget that has lost the selection ownership. selection Specifies the atom that names the selection. client_data Specifies the value passed in by the widget when it took ownership of the selection. |__ This procedure, which is optional, is called by the Intrin- sics to inform the selection owner that it no longer owns 309 X Toolkit Intrinsics X11 Release 6.4 the selection. The procedure pointer specified by the incremental selection owner when it desires notification of receipt of the data or when it manages the storage containing the data is of type XtSelectionDoneIncrProc. __ | typedef void (*XtSelectionDoneIncrProc)(Widget, Atom*, Atom*, XtRequestId*, XtPointer); Widget w; Atom *selection; Atom *target; XtRequestId *request_id; XtPointer client_data; w Specifies the widget that owns the selection. selection Specifies the atom that names the selection being transferred. target Specifies the target type to which the conversion was done. request_id Specifies an opaque identification for a specific request. client_data Specified the value passed in by the widget when it took ownership of the selection. |__ This procedure, which is optional, is called by the Intrin- sics after the requestor has retrieved the final (zero- length) segment of the incremental transfer to indicate that the entire transfer is complete. If this procedure is not specified, the Intrinsics will free only the final value returned by the selection owner using XtFree. The procedure pointer specified by the incremental selection owner to notify it if a transfer should be terminated prema- turely is of type XtCancelConvertSelectionProc. 310 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtCancelConvertSelectionProc)(Widget, Atom*, Atom*, XtRequestId*, XtPointer); Widget w; Atom *selection; Atom *target; XtRequestId *request_id; XtPointer client_data; w Specifies the widget that owns the selection. selection Specifies the atom that names the selection being transferred. target Specifies the target type to which the conversion was done. request_id Specifies an opaque identification for a specific request. client_data Specifies the value passed in by the widget when it took ownership of the selection. |__ This procedure is called by the Intrinsics when it has been determined by means of a timeout or other mechanism that any remaining segments of the selection no longer need to be transferred. Upon receiving this callback, the selection request is considered complete and the owner can free the memory and any other resources that have been allocated for the transfer. 11.5.3.2. Getting the Selection Value Incrementally To obtain the value of the selection using incremental transfers, use XtGetSelectionValueIncremental or XtGetSelec- tionValuesIncremental. 311 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetSelectionValueIncremental(w, selection, target, selection_callback, client_data, time) Widget w; Atom selection; Atom target; XtSelectionCallbackProc selection_callback; XtPointer client_data; Time time; w Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the particular selection desired. target Specifies the type of information needed about the selection. selection_callback Specifies the callback procedure to be called to receive each data segment. client_data Specifies client-specific data to be passed to the specified callback procedure when it is invoked. time Specifies the timestamp that indicates when the selection request was initiated. This should be the timestamp of the event that triggered this request; the value CurrentTime is not acceptable. |__ The XtGetSelectionValueIncremental function is similar to XtGetSelectionValue except that the selection_callback pro- cedure will be called repeatedly upon delivery of multiple segments of the selection value. The end of the selection value is indicated when selection_callback is called with a non-NULL value of length zero, which must still be freed by the client. If the transfer of the selection is aborted in the middle of a transfer (for example, because of a time- out), the selection_callback procedure is called with a type value equal to the symbolic constant XT_CONVERT_FAIL so that the requestor can dispose of the partial selection value it has collected up until that point. Upon receiving XT_CON- VERT_FAIL, the requesting client must determine for itself whether or not a partially completed data transfer is mean- ingful. For more information about selection, target, and time, see Section 2.6 in the Inter-Client Communication Con- ventions Manual. 312 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetSelectionValuesIncremental(w, selection, targets, count, selection_callback, client_data, time) Widget w; Atom selection; Atom *targets; int count; XtSelectionCallbackProc selection_callback; XtPointer *client_data; Time time; w Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the particular selection desired. targets Specifies the types of information needed about the selection. count Specifies the length of the targets and client_data lists. selection_callback Specifies the callback procedure to be called to receive each selection value. client_data Specifies a list of client data (one for each tar- get type) values that are passed to the callback procedure when it is invoked for the corresponding target. time Specifies the timestamp that indicates when the selection request was initiated. This should be the timestamp of the event that triggered this request; the value CurrentTime is not acceptable. |__ The XtGetSelectionValuesIncremental function is similar to XtGetSelectionValueIncremental except that it takes a list of targets and client data. XtGetSelectionValuesIncremental is equivalent to calling XtGetSelectionValueIncremental suc- cessively for each target/client_data pair except that XtGetSelectionValuesIncremental does guarantee that all the conversions will use the same selection value because the ownership of the selection cannot change in the middle of the list, as would be possible when calling XtGetSelection- ValueIncremental repeatedly. For more information about selection, target, and time, see Section 2.6 in the Inter- Client Communication Conventions Manual. 313 X Toolkit Intrinsics X11 Release 6.4 11.5.3.3. Setting the Selection Owner for Incremental Transfers To set the selection owner when using incremental transfers, use XtOwnSelectionIncremental. 314 X Toolkit Intrinsics X11 Release 6.4 __ | Boolean XtOwnSelectionIncremental(w, selection, time, convert_callback, lose_callback, done_callback, cancel_callback, client_data) Widget w; Atom selection; Time time; XtConvertSelectionIncrProc convert_callback; XtLoseSelectionIncrProc lose_callback; XtSelectionDoneIncrProc done_callback; XtCancelConvertSelectionProc cancel_callback; XtPointer client_data; w Specifies the widget that wishes to become the owner. Must be of class Core or any subclass thereof. selection Specifies the atom that names the selection. time Specifies the timestamp that indicates when the selection ownership request was initiated. This should be the timestamp of the event that trig- gered ownership; the value CurrentTime is not acceptable. convert_callback Specifies the procedure to be called whenever the current value of the selection is requested. lose_callback Specifies the procedure to be called whenever the widget has lost selection ownership, or NULL if the owner is not interested in being noti- fied. done_callback Specifies the procedure called after the requestor has received the entire selection, or NULL if the owner is not interested in being notified. cancel_callback Specifies the callback procedure to be called when a selection request aborts because a time- out expires, or NULL if the owner is not inter- ested in being notified. client_data Specifies the argument to be passed to each of the callback procedures when they are called. |__ The XtOwnSelectionIncremental procedure informs the Intrin- sics incremental selection mechanism that the specified wid- get wishes to own the selection. It returns True if the 315 X Toolkit Intrinsics X11 Release 6.4 specified widget successfully becomes the selection owner or False otherwise. For more information about selection, tar- get, and time, see Section 2.6 in the Inter-Client Communi- cation Conventions Manual. If a done_callback procedure is specified, the client owns the storage allocated for passing the value to the Intrin- sics. If done_callback is NULL, the convert_callback proce- dure must allocate storage using XtMalloc, XtRealloc, or XtCalloc, and the final value specified is freed by the Intrinsics when the transfer is complete. After a selection transfer has started, only one of the done_callback or can- cel_callback procedures is invoked to indicate completion of the transfer. The lose_callback procedure does not indicate completion of any in-progress transfers; it is invoked at the time a SelectionClear event is dispatched regardless of any active transfers, which are still expected to continue. A widget that becomes the selection owner using XtOwnSelec- tionIncremental may use XtDisownSelection to relinquish selection ownership. 11.5.4. Setting and Retrieving Selection Target Parameters To specify target parameters for a selection request with a single target, use XtSetSelectionParameters. 316 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetSelectionParameters(requestor, selection, type, value, length, format) Widget requestor; Atom selection; Atom type; XtPointer value; unsigned long length; int format; requestor Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the atom that names the selection. type Specifies the type of the property in which the parameters are passed. value Specifies a pointer to the parameters. length Specifies the number of elements containing data in value, each element of a size indicated by for- mat. format Specifies the size in bits of the data in the ele- ments of value. The specified parameters are copied and stored in a new property of the specified type and format on the requestor's window. To initiate a selection request with a target and these parameters, a subsequent call to XtGetSelectionValue or to XtGetSelectionValueIncremental specifying the same requestor widget and selection atom will generate a Convert- Selection request referring to the property containing the parameters. If XtSetSelectionParameters is called more than once with the same widget and selection without a call to specify a request, the most recently specified parameters are used in the subsequent request. |__ The possible values of format are 8, 16, or 32. If the for- mat is 8, the elements of value are assumed to be sizeof(char); if 16, sizeof(short); if 32, sizeof(long). To generate a MULTIPLE target request with parameters for any of the multiple targets of the selection request, pre- cede individual calls to XtGetSelectionValue and XtGetSelec- tionValueIncremental with corresponding individual calls to XtSetSelectionParameters, and enclose these all within XtCreateSelectionRequest and XtSendSelectionRequest. XtGetS- electionValues and XtGetSelectionValuesIncremental cannot be used to make selection requests with parameterized targets. 317 X Toolkit Intrinsics X11 Release 6.4 To retrieve any target parameters needed to perform a selec- tion conversion, the selection owner calls XtGetSelectionPa- rameters. __ | void XtGetSelectionParameters(owner, selection, request_id, type_return, value_return, length_return, format_return) Widget owner; Atom selection; XtRequestId request_id; Atom *type_return; XtPointer *value_return; unsigned long *length_return; int *format_return; owner Specifies the widget that owns the specified selection. selection Specifies the selection being processed. request_id Specifies the requestor id in the case of incre- mental selections, or NULL in the case of atomic transfers. type_return Specifies a pointer to an atom in which the prop- erty type of the parameters is stored. value_return Specifies a pointer into which a pointer to the parameters is to be stored. A NULL is stored if no parameters accompany the request. length_return Specifies a pointer into which the number of data elements in value_return of size indicated by for- mat_return are stored. format_return Specifies a pointer into which the size in bits of the parameter data in the elements of value is stored. |__ XtGetSelectionParameters may be called only from within an XtConvertSelectionProc or from within the first call to an XtConvertSelectionIncrProc with a new request_id. It is the responsibility of the caller to free the returned parameters using XtFree when the parameters are no longer needed. 318 X Toolkit Intrinsics X11 Release 6.4 11.5.5. Generating MULTIPLE Requests To have the Intrinsics bundle multiple calls to make selec- tion requests into a single request using a MULTIPLE target, use XtCreateSelectionRequest and XtSendSelectionRequest. __ | void XtCreateSelectionRequest(requestor, selection) Widget requestor; Atom selection; requestor Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the particular selection desired. |__ When XtCreateSelectionRequest is called, subsequent calls to XtGetSelectionValue, XtGetSelectionValueIncremental, XtGetS- electionValues, and XtGetSelectionValuesIncremental, with the requestor and selection as specified to XtCreateSelec- tionRequest, are bundled into a single selection request with multiple targets. The request is made by calling XtSendSelectionRequest. __ | void XtSendSelectionRequest(requestor, selection, time) Widget requestor; Atom selection; Time time; requestor Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the particular selection desired. time Specifies the timestamp that indicates when the selection request was initiated. The value Cur- rentTime is not acceptable. |__ When XtSendSelectionRequest is called with a value of requestor and selection matching a previous call to XtCre- ateSelectionRequest, a selection request is sent to the selection owner. If a single target request is queued, that request is made. If multiple targets are queued, they are bundled into a single request with a target of MULTIPLE using the specified timestamp. As the values are returned, the callbacks specified in XtGetSelectionValue, XtGetSelec- tionValueIncremental, XtGetSelectionValues, and 319 X Toolkit Intrinsics X11 Release 6.4 XtGetSelectionValueIncremental are invoked. Multi-threaded applications should lock the application con- text before calling XtCreateSelectionRequest and release the lock after calling XtSendSelectionRequest to ensure that the thread assembling the request is safe from interference by another thread assembling a different request naming the same widget and selection. To relinquish the composition of a MULTIPLE request without sending it, use XtCancelSelectionRequest. __ | void XtCancelSelectionRequest(requestor, selection) Widget requestor; Atom selection; requestor Specifies the widget making the request. Must be of class Core or any subclass thereof. selection Specifies the particular selection desired. |__ When XtCancelSelectionRequest is called, any requests queued since the last call to XtCreateSelectionRequest for the same widget and selection are discarded and any resources reserved are released. A subsequent call to XtSendSelec- tionRequest will not result in any request being made. Sub- sequent calls to XtGetSelectionValue, XtGetSelectionValues, XtGetSelectionValueIncremental, or XtGetSelectionValuesIn- cremental will not be deferred. 11.5.6. Auxiliary Selection Properties Certain uses of parameterized selections require clients to name other window properties within a selection parameter. To permit reuse of temporary property names in these circum- stances and thereby reduce the number of unique atoms cre- ated in the server, the Intrinsics provides two interfaces for acquiring temporary property names. To acquire a temporary property name atom for use in a selection request, the client may call XtReserveProperty- Atom. 320 X Toolkit Intrinsics X11 Release 6.4 __ | Atom XtReservePropertyAtom(w) Widget w; w Specifies the widget making a selection request. |__ XtReservePropertyAtom returns an atom that may be used as a property name during selection requests involving the speci- fied widget. As long as the atom remains reserved, it is unique with respect to all other reserved atoms for the wid- get. To return a temporary property name atom for reuse and to delete the property named by that atom, use XtReleaseProp- ertyAtom. __ | void XtReleasePropertyAtom(w, atom) Widget w; Atom atom; w Specifies the widget used to reserve the property name atom. atom Specifies the property name atom returned by XtRe- servePropertyAtom that is to be released for reuse. |__ XtReleasePropertyAtom marks the specified property name atom as no longer in use and ensures that any property having that name on the specified widget's window is deleted. If atom does not specify a value returned by XtReserveProperty- Atom for the specified widget, the results are undefined. 11.5.7. Retrieving the Most Recent Timestamp To retrieve the timestamp from the most recent call to XtDispatchEvent that contained a timestamp, use XtLastTimes- tampProcessed. 321 X Toolkit Intrinsics X11 Release 6.4 __ | Time XtLastTimestampProcessed(display) Display *display; display Specifies an open display connection. |__ If no KeyPress, KeyRelease, ButtonPress, ButtonRelease, MotionNotify, EnterNotify, LeaveNotify, PropertyNotify, or SelectionClear event has yet been passed to XtDispatchEvent for the specified display, XtLastTimestampProcessed returns zero. 11.5.8. Retrieving the Most Recent Event To retrieve the event from the most recent call to XtDis- patchEvent for a specific display, use XtLastEventProcessed. __ | XEvent *XtLastEventProcessed(display) Display *display; display Specifies the display connection from which to retrieve the event. |__ Returns the last event passed to XtDispatchEvent for the specified display. Returns NULL if there is no such event. The client must not modify the contents of the returned event. 11.6. Merging Exposure Events into a Region The Intrinsics provide an XtAddExposureToRegion utility function that merges Expose and GraphicsExpose events into a region for clients to process at once rather than processing individual rectangles. For further information about regions, see Section 16.5 in Xlib -- C Language X Interface. To merge Expose and GraphicsExpose events into a region, use XtAddExposureToRegion. 322 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAddExposureToRegion(event, region) XEvent *event; Region region; event Specifies a pointer to the Expose or GraphicsEx- pose event. region Specifies the region object (as defined in ). |__ The XtAddExposureToRegion function computes the union of the rectangle defined by the exposure event and the specified region. Then it stores the results back in region. If the event argument is not an Expose or GraphicsExpose event, XtAddExposureToRegion returns without an error and without modifying region. This function is used by the exposure compression mechanism; see Section 7.9.3. 11.7. Translating Widget Coordinates To translate an x-y coordinate pair from widget coordinates to root window absolute coordinates, use XtTranslateCoords. __ | void XtTranslateCoords(w, x, y, rootx_return, rooty_return) Widget w; Position x, y; Position *rootx_return, *rooty_return; w Specifies the widget. Must be of class RectObj or any subclass thereof. x y Specify the widget-relative x and y coordinates. rootx_return rooty_return Return the root-relative x and y coordinates. |__ While XtTranslateCoords is similar to the Xlib XTranslateCo- ordinates function, it does not generate a server request because all the required information already is in the wid- get's data structures. 323 X Toolkit Intrinsics X11 Release 6.4 11.8. Translating a Window to a Widget To translate a given window and display pointer into a wid- get instance, use XtWindowToWidget. __ | Widget XtWindowToWidget(display, window) Display *display; Window window; display Specifies the display on which the window is defined. window Specifies the drawable for which you want the wid- get. |__ If there is a realized widget whose window is the specified drawable on the specified display, XtWindowToWidget returns that widget. If not and if the drawable has been associated with a widget through XtRegisterDrawable, XtWindowToWidget returns the widget associated with the drawable. In other cases it returns NULL. 11.9. Handling Errors The Intrinsics allow a client to register procedures that are called whenever a fatal or nonfatal error occurs. These facilities are intended for both error reporting and logging and for error correction or recovery. Two levels of interface are provided: o A high-level interface that takes an error name and class and retrieves the error message text from an error resource database. o A low-level interface that takes a simple string to display. The high-level functions construct a string to pass to the lower-level interface. The strings may be specified in application code and are overridden by the contents of an external systemwide file, the ``error database file''. The location and name of this file are implementation-dependent. 324 X Toolkit Intrinsics X11 Release 6.4 Note The application-context-specific error handling is not implemented on many systems, although the interfaces are always present. Most implementa- tions will have just one set of error handlers for all application contexts within a process. If they are set for different application contexts, the ones registered last will prevail. To obtain the error database (for example, to merge with an application- or widget-specific database), use XtAppGetEr- rorDatabase. __ | XrmDatabase *XtAppGetErrorDatabase(app_context) XtAppContext app_context; app_context Specifies the application context. |__ The XtAppGetErrorDatabase function returns the address of the error database. The Intrinsics do a lazy binding of the error database and do not merge in the database file until the first call to XtAppGetErrorDatabaseText. For a complete listing of all errors and warnings that can be generated by the Intrinsics, see Appendix D. The high-level error and warning handler procedure pointers are of type XtErrorMsgHandler. 325 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtErrorMsgHandler)(String, String, String, String, String*, Cardinal*); String name; String type; String class; String defaultp; String *params; Cardinal *num_params; name Specifies the name to be concatenated with the specified type to form the resource name of the error message. type Specifies the type to be concatenated with the name to form the resource name of the error mes- sage. class Specifies the resource class of the error message. defaultp Specifies the default message to use if no error database entry is found. params Specifies a pointer to a list of parameters to be substituted in the message. num_params Specifies the number of entries in params. |__ The specified name can be a general kind of error, like ``invalidParameters'' or ``invalidWindow'', and the speci- fied type gives extra information such as the name of the routine in which the error was detected. Standard printf notation is used to substitute the parameters into the mes- sage. An error message handler can obtain the error database text for an error or a warning by calling XtAppGetErrorDatabase- Text. 326 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAppGetErrorDatabaseText(app_context, name, type, class, default, buffer_return, nbytes, database) XtAppContext app_context; String name, type, class; String default; String buffer_return; int nbytes; XrmDatabase database; app_context Specifies the application context. name type Specify the name and type concatenated to form the resource name of the error message. class Specifies the resource class of the error message. default Specifies the default message to use if an error database entry is not found. buffer_return Specifies the buffer into which the error message is to be returned. nbytes Specifies the size of the buffer in bytes. database Specifies the name of the alternative database to be used, or NULL if the application context's error database is to be used. |__ The XtAppGetErrorDatabaseText returns the appropriate mes- sage from the error database or returns the specified default message if one is not found in the error database. To form the full resource name and class when querying the database, the name and type are concatenated with a single ``.'' between them and the class is concatenated with itself with a single ``.'' if it does not already contain a ``.''. To return the application name and class as passed to XtDis- playInitialize for a particular Display, use XtGetApplica- tionNameAndClass. 327 X Toolkit Intrinsics X11 Release 6.4 __ | void XtGetApplicationNameAndClass(display, name_return, class_return) Display* display; String* name_return; String* class_return; display Specifies an open display connection that has been initialized with XtDisplayInitialize. name_return Returns the application name. class_return Returns the application class. |__ XtGetApplicationNameAndClass returns the application name and class passed to XtDisplayInitialize for the specified display. If the display was never initialized or has been closed, the result is undefined. The returned strings are owned by the Intrinsics and must not be modified or freed by the caller. To register a procedure to be called on fatal error condi- tions, use XtAppSetErrorMsgHandler. __ | XtErrorMsgHandler XtAppSetErrorMsgHandler(app_context, msg_handler) XtAppContext app_context; XtErrorMsgHandler msg_handler; app_context Specifies the application context. msg_handler Specifies the new fatal error procedure, which should not return. |__ XtAppSetErrorMsgHandler returns a pointer to the previously installed high-level fatal error handler. The default high- level fatal error handler provided by the Intrinsics is named _XtDefaultErrorMsg and constructs a string from the error resource database and calls XtError. Fatal error mes- sage handlers should not return. If one does, subsequent Intrinsics behavior is undefined. To call the high-level error handler, use XtAppErrorMsg. 328 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAppErrorMsg(app_context, name, type, class, default, params, num_params) XtAppContext app_context; String name; String type; String class; String default; String *params; Cardinal *num_params; app_context Specifies the application context. name Specifies the general kind of error. type Specifies the detailed name of the error. class Specifies the resource class. default Specifies the default message to use if an error database entry is not found. params Specifies a pointer to a list of values to be stored in the message. num_params Specifies the number of entries in params. |__ The Intrinsics internal errors all have class ``XtToolkitEr- ror''. To register a procedure to be called on nonfatal error con- ditions, use XtAppSetWarningMsgHandler. __ | XtErrorMsgHandler XtAppSetWarningMsgHandler(app_context, msg_handler) XtAppContext app_context; XtErrorMsgHandler msg_handler; app_context Specifies the application context. msg_handler Specifies the new nonfatal error procedure, which usually returns. |__ XtAppSetWarningMsgHandler returns a pointer to the previ- ously installed high-level warning handler. The default 329 X Toolkit Intrinsics X11 Release 6.4 high-level warning handler provided by the Intrinsics is named _XtDefaultWarningMsg and constructs a string from the error resource database and calls XtWarning. To call the installed high-level warning handler, use XtApp- WarningMsg. __ | void XtAppWarningMsg(app_context, name, type, class, default, params, num_params) XtAppContext app_context; String name; String type; String class; String default; String *params; Cardinal *num_params; app_context Specifies the application context. name Specifies the general kind of error. type Specifies the detailed name of the error. class Specifies the resource class. default Specifies the default message to use if an error database entry is not found. params Specifies a pointer to a list of values to be stored in the message. num_params Specifies the number of entries in params. |__ The Intrinsics internal warnings all have class ``XtToolkitError''. The low-level error and warning handler procedure pointers are of type XtErrorHandler. 330 X Toolkit Intrinsics X11 Release 6.4 __ | typedef void (*XtErrorHandler)(String); String message; message Specifies the error message. |__ The error handler should display the message string in some appropriate fashion. To register a procedure to be called on fatal error condi- tions, use XtAppSetErrorHandler. __ | XtErrorHandler XtAppSetErrorHandler(app_context, handler) XtAppContext app_context; XtErrorHandler handler; app_context Specifies the application context. handler Specifies the new fatal error procedure, which should not return. |__ XtAppSetErrorHandler returns a pointer to the previously installed low-level fatal error handler. The default low- level error handler provided by the Intrinsics is _XtDe- faultError. On POSIX-based systems, it prints the message to standard error and terminates the application. Fatal error message handlers should not return. If one does, sub- sequent Intrinsics behavior is undefined. To call the installed fatal error procedure, use XtAppError. __ | void XtAppError(app_context, message) XtAppContext app_context; String message; app_context Specifies the application context. message Specifies the message to be reported. |__ Most programs should use XtAppErrorMsg, not XtAppError, to 331 X Toolkit Intrinsics X11 Release 6.4 provide for customization and internationalization of error messages. To register a procedure to be called on nonfatal error con- ditions, use XtAppSetWarningHandler. __ | XtErrorHandler XtAppSetWarningHandler(app_context, handler) XtAppContext app_context; XtErrorHandler handler; app_context Specifies the application context. handler Specifies the new nonfatal error procedure, which usually returns. |__ XtAppSetWarningHandler returns a pointer to the previously installed low-level warning handler. The default low-level warning handler provided by the Intrinsics is _XtDefault- Warning. On POSIX-based systems, it prints the message to standard error and returns to the caller. To call the installed nonfatal error procedure, use XtApp- Warning. __ | void XtAppWarning(app_context, message) XtAppContext app_context; String message; app_context Specifies the application context. message Specifies the nonfatal error message to be reported. |__ Most programs should use XtAppWarningMsg, not XtAppWarning, to provide for customization and internationalization of warning messages. 11.10. Setting WM_COLORMAP_WINDOWS A client may set the value of the WM_COLORMAP_WINDOWS prop- erty on a widget's window by calling XtSetWMColormapWindows. 332 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetWMColormapWindows(widget, list, count) Widget widget; Widget* list; Cardinal count; widget Specifies the widget on whose window the WM_COL- ORMAP_WINDOWS property is stored. Must be of class Core or any subclass thereof. list Specifies a list of widgets whose windows are potentially to be listed in the WM_COLORMAP_WIN- DOWS property. count Specifies the number of widgets in list. |__ XtSetWMColormapWindows returns immediately if widget is not realized or if count is 0. Otherwise, XtSetWMColormapWin- dows constructs an ordered list of windows by examining each widget in list in turn and ignoring the widget if it is not realized, or adding the widget's window to the window list if the widget is realized and if its colormap resource is different from the colormap resources of all widgets whose windows are already on the window list. Finally, XtSetWMColormapWindows stores the resulting window list in the WM_COLORMAP_WINDOWS property on the specified widget's window. Refer to Section 4.1.8 in the Inter-Client Communication Conventions Manual for details of the seman- tics of the WM_COLORMAP_WINDOWS property. 11.11. Finding File Names The Intrinsics provide procedures to look for a file by name, allowing string substitutions in a list of file speci- fications. Two routines are provided for this: XtFindFile and XtResolvePathname. XtFindFile uses an arbitrary set of client-specified substitutions, and XtResolvePathname uses a set of standard substitutions corresponding to the X/Open Portability Guide language localization conventions. Most applications should use XtResolvePathname. A string substitution is defined by a list of Substitution entries. 333 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { char match; String substitution; } SubstitutionRec, *Substitution; |__ File name evaluation is handled in an operating-system- dependent fashion by an XtFilePredicate procedure. __ | typedef Boolean (*XtFilePredicate)(String); String filename; filename Specifies a potential filename. |__ A file predicate procedure is called with a string that is potentially a file name. It should return True if this string specifies a file that is appropriate for the intended use and False otherwise. To search for a file using substitutions in a path list, use XtFindFile. __ | String XtFindFile(path, substitutions, num_substitutions, predicate) String path; Substitution substitutions; Cardinal num_substitutions; XtFilePredicate predicate; path Specifies a path of file names, including sub- stitution characters. substitutions Specifies a list of substitutions to make into the path. num_substitutions Specifies the number of substitutions passed in. predicate Specifies a procedure called to judge each potential file name, or NULL. |__ The path parameter specifies a string that consists of a series of potential file names delimited by colons. Within 334 X Toolkit Intrinsics X11 Release 6.4 each name, the percent character specifies a string substi- tution selected by the following character. The character sequence ``%:'' specifies an embedded colon that is not a delimiter; the sequence is replaced by a single colon. The character sequence ``%%'' specifies a percent character that does not introduce a substitution; the sequence is replaced by a single percent character. If a percent character is followed by any other character, XtFindFile looks through the specified substitutions for that character in the match field and, if found, replaces the percent and match charac- ters with the string in the corresponding substitution field. A substitution field entry of NULL is equivalent to a pointer to an empty string. If the operating system does not interpret multiple embedded name separators in the path (i.e., ``/'' in POSIX) the same way as a single separator, XtFindFile will collapse multiple separators into a single one after performing all string substitutions. Except for collapsing embedded separators, the contents of the string substitutions are not interpreted by XtFindFile and may therefore contain any operating-system-dependent characters, including additional name separators. Each resulting string is passed to the predicate procedure until a string is found for which the procedure returns True; this string is the return value for XtFindFile. If no string yields a True return from the predicate, XtFindFile returns NULL. If the predicate parameter is NULL, an internal procedure that checks if the file exists, is readable, and is not a directory is used. It is the responsibility of the caller to free the returned string using XtFree when it is no longer needed. To search for a file using standard substitutions in a path list, use XtResolvePathname. 335 X Toolkit Intrinsics X11 Release 6.4 __ | String XtResolvePathname(display, type, filename, suffix, path, substitutions, num_substitutions, predicate) Display *display; String type, filename, suffix, path; Substitution substitutions; Cardinal num_substitutions; XtFilePredicate predicate; display Specifies the display to use to find the lan- guage for language substitutions. type filename suffix Specify values to substitute into the path. path Specifies the list of file specifications, or NULL. substitutions Specifies a list of additional substitutions to make into the path, or NULL. num_substitutions Specifies the number of entries in substitu- tions. predicate Specifies a procedure called to judge each potential file name, or NULL. |__ The substitutions specified by XtResolvePathname are deter- mined from the value of the language string retrieved by XtDisplayInitialize for the specified display. To set the language for all applications specify ``*xnlLanguage: lang'' in the resource database. The format and content of the language string are implementation-defined. One suggested syntax is to compose the language string of three parts; a ``language part'', a ``territory part'' and a ``codeset part''. The manner in which this composition is accom- plished is implementation-defined, and the Intrinsics make no interpretation of the parts other than to use them in substitutions as described below. XtResolvePathname calls XtFindFile with the following sub- stitutions in addition to any passed by the caller and returns the value returned by XtFindFile: %N The value of the filename parameter, or the applica- tion's class name if filename is NULL. %T The value of the type parameter. 336 X Toolkit Intrinsics X11 Release 6.4 %S The value of the suffix parameter. %L The language string associated with the specified dis- play. %l The language part of the display's language string. %t The territory part of the display's language string. %c The codeset part of the display's language string. %C The customization string retrieved from the resource database associated with display. %D The value of the implementation-specific default path. If a path is passed to XtResolvePathname, it is passed along to XtFindFile. If the path argument is NULL, the value of the XFILESEARCHPATH environment variable is passed to XtFindFile. If XFILESEARCHPATH is not defined, an implemen- tation-specific default path is used that contains at least six entries. These entries must contain the following sub- stitutions: 1. %C, %N, %S, %T, %L or%C, %N, %S, %T, %l, %t, %c 2. %C, %N, %S, %T, %l 3. %C, %N, %S, %T 4. %N, %S, %T, %L or %N, %S, %T, %l, %t, %c 5. %N, %S, %T, %l 6. %N, %S, %T The order of these six entries within the path must be as given above. The order and use of substitutions within a given entry are implementation-dependent. If the path begins with a colon, it is preceded by %N%S. If the path includes two adjacent colons, %N%S is inserted between them. The type parameter is intended to be a category of files, usually being translated into a directory in the pathname. Possible values might include ``app-defaults'', ``help'', and ``bitmap''. The suffix parameter is intended to be appended to the file name. Possible values might include ``.txt'', ``.dat'', and ``.bm''. A suggested value for the default path on POSIX-based sys- tems is /usr/lib/X11/%L/%T/%N%C%S:/usr/lib/X11/%l/%T/%N%C%S:\ /usr/lib/X11/%T/%N%C%S:/usr/lib/X11/%L/%T/%N%S:\ /usr/lib/X11/%l/%T/%N%S:/usr/lib/X11/%T/%N%S 337 X Toolkit Intrinsics X11 Release 6.4 Using this example, if the user has specified a language, it is used as a subdirectory of /usr/lib/X11 that is searched for other files. If the desired file is not found there, the lookup is tried again using just the language part of the specification. If the file is not there, it is looked for in /usr/lib/X11. The type parameter is used as a subdi- rectory of the language directory or of /usr/lib/X11, and suffix is appended to the file name. The %D substitution allows the addition of path elements to the implementation-specific default path, typically to allow additional directories to be searched without preventing resources in the system directories from being found. For example, a user installing resource files under a directory called ``ourdir'' might set XFILESEARCHPATH to %D:ourdir/%T/%N%C:ourdir/%T/%N The customization string is obtained by querying the resource database currently associated with the display (the database returned by XrmGetDatabase) for the resource appli- cation_name.customization, class application_class.Cus- tomization, where application_name and application_class are the values returned by XtGetApplicationNameAndClass. If no value is specified in the database, the empty string is used. It is the responsibility of the caller to free the returned string using XtFree when it is no longer needed. 11.12. Hooks for External Agents Applications may register functions that are called at a particular control points in the Intrinsics. These func- tions are intended to be used to provide notification of an "X Toolkit event", such as widget creation, to an external agent, such as an interactive resource editor, drag-and-drop server, or an aid for physically challenged users. The con- trol points containing such registration hooks are identi- fied in a "hook registration" object. To retrieve the hook registration widget, use XtHooksOfDis- play. 338 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtHooksOfDisplay(display) Display *display; display Specifies the desired display. |__ The class of this object is a private, implementation-depen- dent subclass of Object. The hook object has no parent. The resources of this object are the callback lists for hooks and the read-only resources for getting a list of par- entless shells. All of the callback lists are initially empty. When a display is closed, the hook object associated with it is destroyed. The following procedures can be called with the hook regis- tration object as an argument: XtAddCallback, XtAddCallbacks, XtRemoveCallback, XtRemoveCallbacks, XtRemoveAllCallbacks, XtCallCall- backs, XtHasCallbacks, XtCallCallbackList XtClass, XtSuperclass, XtIsSubclass, XtCheckSubclass, XtIsObject, XtIsRectObj, XtIsWidget, XtIsComposite, XtIsConstraint, XtIsShell, XtIsOverrideShell, XtIsWMShell, XtIsVendorShell, XtIsTransientShell, XtIsToplevelShell, XtIsApplicationShell, XtIsSession- Shell XtWidgetToApplicationContext XtName, XtParent, XtDisplayOfObject, XtScreenOfObject XtSetValues, XtGetValues, XtVaSetValues, XtVaGetValues 11.12.1. Hook Object Resources The resource names, classes, and representation types that are specified in the hook object resource list are: 339 X Toolkit Intrinsics X11 Release 6.4 --------------------------------------------------------------- Name Class Representation --------------------------------------------------------------- XtNcreateHook XtCCallback XtRCallback XtNchangeHook XtCCallback XtRCallback XtNconfigureHook XtCCallback XtRCallback XtNgeometryHook XtCCallback XtRCallback XtNdestroyHook XtCCallback XtRCallback XtNshells XtCReadOnly XtRWidgetList XtNnumShells XtCReadOnly XtRCardinal --------------------------------------------------------------- Descriptions of each of these resources: The XtNcreateHook callback list is called from: XtCreateWid- get, XtCreateManagedWidget, XtCreatePopupShell, XtAppCre- ateShell, and their corresponding varargs versions. The call_data parameter in a createHook callback may be cast to type XtCreateHookData. __ | typedef struct { String type; Widget widget; ArgList args; Cardinal num_args; } XtCreateHookDataRec, *XtCreateHookData; |__ The type is set to XtHcreate, widget is the newly created widget, and args and num_args are the arguments passed to the create function. The callbacks are called before return- ing from the create function. The XtNchangeHook callback list is called from: XtSetValues, XtVaSetValues XtManageChild, XtManageChildren, XtUnmanageChild, XtUn- manageChildren XtRealizeWidget, XtUnrealizeWidget XtAddCallback, XtRemoveCallback, XtAddCallbacks, XtRemoveCallbacks, XtRemoveAllCallbacks XtAugmentTranslations, XtOverrideTranslations, XtUnin- stallTranslations 340 X Toolkit Intrinsics X11 Release 6.4 XtSetKeyboardFocus, XtSetWMColormapWindows XtSetMappedWhenManaged, XtMapWidget, XtUnmapWidget XtPopup, XtPopupSpringLoaded, XtPopdown The call_data parameter in a changeHook callback may be cast to type XtChangeHookData. __ | typedef struct { String type; Widget widget; XtPointer event_data; Cardinal num_event_data; } XtChangeHookDataRec, *XtChangeHookData; |__ When the changeHook callbacks are called as a result of a call to XtSetValues or XtVaSetValues, type is set to XtHset- Values, widget is the new widget passed to the set_values procedure, and event_data may be cast to type XtChangeHook- SetValuesData. __ | typedef struct { Widget old, req; ArgList args; Cardinal num_args; } XtChangeHookSetValuesDataRec, *XtChangeHookSetValuesData; |__ The old, req, args, and num_args are the parameters passed to the set_values procedure. The callbacks are called after the set_values and constraint set_values procedures have been called. When the changeHook callbacks are called as a result of a call to XtManageChild or XtManageChildren, type is set to XtHmanageChildren, widget is the parent, event_data may be cast to type WidgetList and is the list of children being managed, and num_event_data is the length of the widget list. The callbacks are called after the children have been managed. When the changeHook callbacks are called as a result of a call to XtUnmanageChild or XtUnmanageChildren, type is set to XtHunmanageChildren, widget is the parent, event_data may 341 X Toolkit Intrinsics X11 Release 6.4 be cast to type WidgetList and is a list of the children being unmanaged, and num_event_data is the length of the widget list. The callbacks are called after the children have been unmanaged. The changeHook callbacks are called twice as a result of a call to XtChangeManagedSet, once after unmanaging and again after managing. When the callbacks are called the first time, type is set to XtHunmanageSet, widget is the parent, event_data may be cast to type WidgetList and is a list of the children being unmanaged, and num_event_data is the length of the widget list. When the callbacks are called the second time, the type is set to XtHmanageSet, widget is the parent, event_data may be cast to type WidgetList and is a list of the children being managed, and num_event_data is the length of the widget list. When the changeHook callbacks are called as a result of a call to XtRealizeWidget, the type is set to XtHrealizeWidget and widget is the widget being realized. The callbacks are called after the widget has been realized. When the changeHook callbacks are called as a result of a call to XtUnrealizeWidget, the type is set to XtHunreal- izeWidget, and widget is the widget being unrealized. The callbacks are called after the widget has been unrealized. When the changeHook callbacks are called as a result of a call to XtAddCallback, type is set to XtHaddCallback, widget is the widget to which the callback is being added, and event_data may be cast to type String and is the name of the callback being added. The callbacks are called after the callback has been added to the widget. When the changeHook callbacks are called as a result of a call to XtAddCallbacks, the type is set to XtHaddCallbacks, widget is the widget to which the callbacks are being added, and event_data may be cast to type String and is the name of the callbacks being added. The callbacks are called after the callbacks have been added to the widget. When the changeHook callbacks are called as a result of a call to XtRemoveCallback, the type is set to XtHremoveCall- back, widget is the widget from which the callback is being removed, and event_data may be cast to type String and is the name of the callback being removed. The callbacks are called after the callback has been removed from the widget. When the changeHook callbacks are called as a result of a call to XtRemoveCallbacks, the type is set to XtHremoveCall- backs, widget is the widget from which the callbacks are being removed, and event_data may be cast to type String and is the name of the callbacks being removed. The callbacks are called after the callbacks have been removed from the 342 X Toolkit Intrinsics X11 Release 6.4 widget. When the changeHook callbacks are called as a result of a call to XtRemoveAllCallbacks, the type is set to XtHre- moveAllCallbacks and widget is the widget from which the callbacks are being removed. The callbacks are called after the callbacks have been removed from the widget. When the changeHook callbacks are called as a result of a call to XtAugmentTranslations, the type is set to XtHaug- mentTranslations and widget is the widget whose translations are being modified. The callbacks are called after the wid- get's translations have been modified. When the changeHook callbacks are called as a result of a call to XtOverrideTranslations, the type is set to XtHover- rideTranslations and widget is the widget whose translations are being modified. The callbacks are called after the wid- get's translations have been modified. When the changeHook callbacks are called as a result of a call to XtUninstallTranslations, The type is XtHuninstall- Translations and widget is the widget whose translations are being uninstalled. The callbacks are called after the wid- get's translations have been uninstalled. When the changeHook callbacks are called as a result of a call to XtSetKeyboardFocus, the type is set to XtHsetKey- boardFocus and event_data may be cast to type Widget and is the value of the descendant argument passed to XtSetKey- boardFocus. The callbacks are called before returning from XtSetKeyboardFocus. When the changeHook callbacks are called as a result of a call to XtSetWMColormapWindows, type is set to XtHsetWMCol- ormapWindows, event_data may be cast to type WidgetList and is the value of the list argument passed to XtSetWMColormap- Windows, and num_event_data is the length of the list. The callbacks are called before returning from XtSetWMColormap- Windows. When the changeHook callbacks are called as a result of a call to XtSetMappedWhenManaged, the type is set to XtH- setMappedWhenManaged and event_data may be cast to type Boolean and is the value of the mapped_when_managed argument passed to XtSetMappedWhenManaged. The callbacks are called after setting the widget's mapped_when_managed field and before realizing or unrealizing the widget. When the changeHook callbacks are called as a result of a call to XtMapWidget, the type is set to XtHmapWidget and widget is the widget being mapped. The callbacks are called after mapping the widget. 343 X Toolkit Intrinsics X11 Release 6.4 When the changeHook callbacks are called as a result of a call to XtUnmapWidget, the type is set to XtHunmapWidget and widget is the widget being unmapped. The callbacks are called after unmapping the widget. When the changeHook callbacks are called as a result of a call to XtPopup, the type is set to XtHpopup, widget is the widget being popped up, and event_data may be cast to type XtGrabKind and is the value of the grab_kind argument passed to XtPopup. The callbacks are called before returning from XtPopup. When the changeHook callbacks are called as a result of a call to XtPopupSpringLoaded, the type is set to XtHpopup- SpringLoaded and widget is the widget being popped up. The callbacks are called before returning from XtPopup- SpringLoaded. When the changeHook callbacks are called as a result of a call to XtPopdown, the type is set to XtHpopdown and widget is the widget being popped down. The callbacks are called before returning from XtPopdown. A widget set that exports interfaces that change application state without employing the Intrinsics library should invoke the change hook itself. This is done by: XtCallCallbacks(XtHooksOfDisplay(dpy), XtNchangeHook, call_data); The XtNconfigureHook callback list is called any time the Intrinsics move, resize, or configure a widget and when XtResizeWindow is called. The call_data parameter may be cast to type XtConfigureHook- Data. __ | typedef struct { String type; Widget widget; XtGeometryMask changeMask; XWindowChanges changes; } XtConfigureHookDataRec, *XtConfigureHookData; |__ When the configureHook callbacks are called, the type is XtHconfigure, widget is the widget being configured, and changeMask and changes reflect the changes made to the 344 X Toolkit Intrinsics X11 Release 6.4 widget. The callbacks are called after changes have been made to the widget. The XtNgeometryHook callback list is called from XtMake- GeometryRequest and XtMakeResizeRequest once before and once after geometry negotiation occurs. The call_data parameter may be cast to type XtGeometryHook- Data. __ | typedef struct { String type; Widget widget; XtWidgetGeometry* request; XtWidgetGeometry* reply; XtGeometryResult result; } XtGeometryHookDataRec, *XtGeometryHookData; |__ When the geometryHook callbacks are called prior to geometry negotiation, the type is XtHpreGeometry, widget is the wid- get for which the request is being made, and request is the requested geometry. When the geometryHook callbacks are called after geometry negotiation, the type is XtHpostGeome- try, widget is the widget for which the request was made, request is the requested geometry, reply is the resulting geometry granted, and result is the value returned from the geometry negotiation. The XtNdestroyHook callback list is called when a widget is destroyed. The call_data parameter may be cast to type XtDestroyHookData. __ | typedef struct { String type; Widget widget; } XtDestroyHookDataRec, *XtDestroyHookData; |__ When the destroyHook callbacks are called as a result of a call to XtDestroyWidget, the type is XtHdestroy and widget is the widget being destroyed. The callbacks are called upon completion of phase one destroy for a widget. 345 X Toolkit Intrinsics X11 Release 6.4 The XtNshells and XtnumShells are read-only resources that report a list of all parentless shell widgets associated with a display. Clients who use these hooks must exercise caution in calling Intrinsics functions in order to avoid recursion. 11.12.2. Querying Open Displays To retrieve a list of the Displays associated with an appli- cation context, use XtGetDisplays. __ | void XtGetDisplays(app_context, dpy_return, num_dpy_return) XtAppContext app_context; Display ***dpy_return; Cardinal *num_dpy_return; app_context Specifies the application context. dpy_return Returns a list of open Display connections in the specified application context. num_dpy_return Returns the count of open Display connections in dpy_return. |__ XtGetDisplays may be used by an external agent to query the list of open displays that belong to an application context. To free the list of displays, use XtFree. 346 X Toolkit Intrinsics X11 Release 6.4 Chapter 12 Nonwidget Objects Although widget writers are free to treat Core as the base class of the widget hierarchy, there are actually three classes above it. These classes are Object, RectObj (Rect- angle Object), and (unnamed), and members of these classes are referred to generically as objects. By convention, the term widget refers only to objects that are a subclass of Core, and the term nonwidget refers to objects that are not a subclass of Core. In the preceding portion of this speci- fication, the interface descriptions indicate explicitly whether the generic widget argument is restricted to partic- ular subclasses of Object. Sections 12.2.5, 12.3.5, and 12.5 summarize the permissible classes of the arguments to, and return values from, each of the Intrinsics routines. 12.1. Data Structures In order not to conflict with previous widget code, the data structures used by nonwidget objects do not follow all the same conventions as those for widgets. In particular, the class records are not composed of parts but instead are com- plete data structures with filler for the widget fields they do not use. This allows the static class initializers for existing widgets to remain unchanged. 12.2. Object Objects The Object object contains the definitions of fields common to all objects. It encapsulates the mechanisms for resource management. All objects and widgets are members of sub- classes of Object, which is defined by the ObjectClassPart and ObjectPart structures. 12.2.1. ObjectClassPart Structure The common fields for all object classes are defined in the ObjectClassPart structure. All fields have the same pur- pose, function, and restrictions as the corresponding fields in CoreClassPart; fields whose names are objn for some inte- ger n are not used for Object, but exist to pad the data structure so that it matches Core's class record. The class record initialization must fill all objn fields with NULL or zero as appropriate to the type. 347 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _ObjectClassPart { WidgetClass superclass; String class_name; Cardinal widget_size; XtProc class_initialize; XtWidgetClassProc class_part_initialize; XtEnum class_inited; XtInitProc initialize; XtArgsProc initialize_hook; XtProc obj1; XtPointer obj2; Cardinal obj3; XtResourceList resources; Cardinal num_resources; XrmClass xrm_class; Boolean obj4; XtEnum obj5; Boolean obj6; Boolean obj7; XtWidgetProc destroy; XtProc obj8; XtProc obj9; XtSetValuesFunc set_values; XtArgsFunc set_values_hook; XtProc obj10; XtArgsProc get_values_hook; XtProc obj11; XtVersionType version; XtPointer callback_private; String obj12; XtProc obj13; XtProc obj14; XtPointer extension; } ObjectClassPart; |__ The extension record defined for ObjectClassPart with a record_type equal to NULLQUARK is ObjectClassExtensionRec. 348 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct { XtPointer next_extension;See Section 1.6.12 XrmQuark record_type; See Section 1.6.12 long version; See Section 1.6.12 Cardinal record_size; See Section 1.6.12 XtAllocateProc allocate; See Section 2.5.5. XtDeallocateProc deallocate;See Section 2.8.4. } ObjectClassExtensionRec, *ObjectClassExtension; |__ The prototypical ObjectClass consists of just the Object- ClassPart. __ | typedef struct _ObjectClassRec { ObjectClassPart object_class; } ObjectClassRec, *ObjectClass; |__ The predefined class record and pointer for ObjectClassRec are In IntrinsicP.h: __ | extern ObjectClassRec objectClassRec; |__ In Intrinsic.h: __ | extern WidgetClass objectClass; |__ The opaque types Object and ObjectClass and the opaque vari- able objectClass are defined for generic actions on objects. The symbolic constant for the ObjectClassExtension version identifier is XtObjectExtensionVersion (see Section 1.6.12). Intrinsic.h uses an incomplete structure definition to ensure that the compiler catches attempts to access private data: 349 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _ObjectClassRec* ObjectClass; |__ 12.2.2. ObjectPart Structure The common fields for all object instances are defined in the ObjectPart structure. All fields have the same meaning as the corresponding fields in CorePart. __ | typedef struct _ObjectPart { Widget self; WidgetClass widget_class; Widget parent; Boolean being_destroyed; XtCallbackList destroy_callbacks; XtPointer constraints; } ObjectPart; |__ All object instances have the Object fields as their first component. The prototypical type Object is defined with only this set of fields. Various routines can cast object pointers, as needed, to specific object types. In IntrinsicP.h: __ | typedef struct _ObjectRec { ObjectPart object; } ObjectRec, *Object; |__ In Intrinsic.h: __ | typedef struct _ObjectRec *Object; |__ 350 X Toolkit Intrinsics X11 Release 6.4 12.2.3. Object Resources The resource names, classes, and representation types speci- fied in the objectClassRec resource list are: ----------------------------------------------------------------- Name Class Representation ----------------------------------------------------------------- XtNdestroyCallback XtCCallback XtRCallback ----------------------------------------------------------------- 12.2.4. ObjectPart Default Values All fields in ObjectPart have the same default values as the corresponding fields in CorePart. 12.2.5. Object Arguments to Intrinsics Routines The WidgetClass arguments to the following procedures may be objectClass or any subclass: XtInitializeWidgetClass, XtCreateWidget, XtVaCreateWid- get XtIsSubclass, XtCheckSubclass XtGetResourceList, XtGetConstraintResourceList The Widget arguments to the following procedures may be of class Object or any subclass: XtCreateWidget, XtVaCreateWidget XtAddCallback, XtAddCallbacks, XtRemoveCallback, XtRemoveCallbacks, XtRemoveAllCallbacks, XtCallCall- backs, XtHasCallbacks, XtCallCallbackList XtClass, XtSuperclass, XtIsSubclass, XtCheckSubclass, XtIsObject, XtIsRectObj, XtIsWidget, XtIsComposite, XtIsConstraint, XtIsShell, XtIsOverrideShell, XtIsWMShell, XtIsVendorShell, XtIsTransientShell, XtIsToplevelShell, XtIsApplicationShell, XtIsSession- Shell XtIsManaged, XtIsSensitive (both will return False if argument is not a subclass of RectObj) 351 X Toolkit Intrinsics X11 Release 6.4 XtIsRealized (returns the state of the nearest windowed ancestor if class of argument is not a subclass of Core) XtWidgetToApplicationContext XtDestroyWidget XtParent, XtDisplayOfObject, XtScreenOfObject, XtWin- dowOfObject XtSetKeyboardFocus (descendant) XtGetGC, XtReleaseGC XtName XtSetValues, XtGetValues, XtVaSetValues, XtVaGetValues XtGetSubresources, XtGetApplicationResources, XtVaGet- Subresources, XtVaGetApplicationResources XtConvert, XtConvertAndStore The return value of the following procedures will be of class Object or a subclass: XtCreateWidget, XtVaCreateWidget XtParent XtNameToWidget The return value of the following procedures will be object- Class or a subclass: XtClass, XtSuperclass 12.2.6. Use of Objects The Object class exists to enable programmers to use the Intrinsics' classing and resource-handling mechanisms for things smaller and simpler than widgets. Objects make obso- lete many common uses of subresources as described in Sec- tions 9.4, 9.7.2.4, and 9.7.2.5. Composite widget classes that wish to accept nonwidget chil- dren must set the accepts_objects field in the Composite- ClassExtension structure to True. XtCreateWidget will 352 X Toolkit Intrinsics X11 Release 6.4 otherwise generate an error message on an attempt to create a nonwidget child. Of the classes defined by the Intrinsics, ApplicationShell and SessionShell accept nonwidget children, and the class of any nonwidget child must not be rectObjClass or any sub- class. The intent of allowing Object children of Applica- tionShell and SessionShell is to provide clients a simple mechanism for establishing the resource-naming root of an object hierarchy. 12.3. Rectangle Objects The class of rectangle objects is a subclass of Object that represents rectangular areas. It encapsulates the mecha- nisms for geometry management and is called RectObj to avoid conflict with the Xlib Rectangle data type. 12.3.1. RectObjClassPart Structure As with the ObjectClassPart structure, all fields in the RectObjClassPart structure have the same purpose and func- tion as the corresponding fields in CoreClassPart; fields whose names are rectn for some integer n are not used for RectObj, but exist to pad the data structure so that it matches Core's class record. The class record initializa- tion must fill all rectn fields with NULL or zero as appro- priate to the type. 353 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _RectObjClassPart { WidgetClass superclass; String class_name; Cardinal widget_size; XtProc class_initialize; XtWidgetClassProc class_part_initialize; XtEnum class_inited; XtInitProc initialize; XtArgsProc initialize_hook; XtProc rect1; XtPointer rect2; Cardinal rect3; XtResourceList resources; Cardinal num_resources; XrmClass xrm_class; Boolean rect4; XtEnum rect5; Boolean rect6; Boolean rect7; XtWidgetProc destroy; XtWidgetProc resize; XtExposeProc expose; XtSetValuesFunc set_values; XtArgsFunc set_values_hook; XtAlmostProc set_values_almost; XtArgsProc get_values_hook; XtProc rect9; XtVersionType version; XtPointer callback_private; String rect10; XtGeometryHandler query_geometry; XtProc rect11; XtPointer extension ; } RectObjClassPart; |__ The RectObj class record consists of just the RectObjClass- Part. __ | typedef struct _RectObjClassRec { RectObjClassPart rect_class; } RectObjClassRec, *RectObjClass; |__ The predefined class record and pointer for RectObjClassRec are In Intrinsic.h: 354 X Toolkit Intrinsics X11 Release 6.4 __ | extern RectObjClassRec rectObjClassRec; |__ In Intrinsic.h: __ | extern WidgetClass rectObjClass; |__ The opaque types RectObj and RectObjClass and the opaque variable rectObjClass are defined for generic actions on objects whose class is RectObj or a subclass of RectObj. Intrinsic.h uses an incomplete structure definition to ensure that the compiler catches attempts to access private data: __ | typedef struct _RectObjClassRec* RectObjClass; |__ 12.3.2. RectObjPart Structure In addition to the ObjectPart fields, RectObj objects have the following fields defined in the RectObjPart structure. All fields have the same meaning as the corresponding field in CorePart. __ | typedef struct _RectObjPart { Position x, y; Dimension width, height; Dimension border_width; Boolean managed; Boolean sensitive; Boolean ancestor_sensitive; } RectObjPart; |__ RectObj objects have the RectObj fields immediately follow- ing the Object fields. 355 X Toolkit Intrinsics X11 Release 6.4 __ | typedef struct _RectObjRec { ObjectPart object; RectObjPart rectangle; } RectObjRec, *RectObj; |__ In Intrinsic.h: __ | typedef struct _RectObjRec* RectObj; |__ 12.3.3. RectObj Resources The resource names, classes, and representation types that are specified in the rectObjClassRec resource list are: ------------------------------------------------------------------- Name Class Representation ------------------------------------------------------------------- XtNancestorSensitive XtCSensitive XtRBoolean XtNborderWidth XtCBorderWidth XtRDimension XtNheight XtCHeight XtRDimension XtNsensitive XtCSensitive XtRBoolean XtNwidth XtCWidth XtRDimension XtNx XtCPosition XtRPosition XtNy XtCPosition XtRPosition ------------------------------------------------------------------- 12.3.4. RectObjPart Default Values All fields in RectObjPart have the same default values as the corresponding fields in CorePart. 12.3.5. Widget Arguments to Intrinsics Routines The WidgetClass arguments to the following procedures may be rectObjClass or any subclass: XtCreateManagedWidget, XtVaCreateManagedWidget The Widget arguments to the following procedures may be of class RectObj or any subclass: 356 X Toolkit Intrinsics X11 Release 6.4 XtConfigureWidget, XtMoveWidget, XtResizeWidget XtMakeGeometryRequest, XtMakeResizeRequest XtManageChildren, XtManageChild, XtUnmanageChildren, XtUnmanageChild, XtChangeManagedSet XtQueryGeometry XtSetSensitive XtTranslateCoords The return value of the following procedures will be of class RectObj or a subclass: XtCreateManagedWidget, XtVaCreateManagedWidget 12.3.6. Use of Rectangle Objects RectObj can be subclassed to provide widgetlike objects (sometimes called gadgets) that do not use windows and do not have those features that are seldom used in simple wid- gets. This can save memory resources both in the server and in applications but requires additional support code in the parent. In the following discussion, rectobj refers only to objects whose class is RectObj or a subclass of RectObj, but not Core or a subclass of Core. Composite widget classes that wish to accept rectobj chil- dren must set the accepts_objects field in the Composite- ClassExtension extension structure to True. XtCreateWidget or XtCreateManagedWidget will otherwise generate an error if called to create a nonwidget child. If the composite widget supports only children of class RectObj or a subclass (i.e., not of the general Object class), it must declare an insert_child procedure and check the subclass of each new child in that procedure. None of the classes defined by the Intrinsics accept rectobj children. If gadgets are defined in an object set, the parent is responsible for much more than the parent of a widget. The parent must request and handle input events that occur for the gadget and is responsible for making sure that when it receives an exposure event the gadget children get drawn correctly. Rectobj children may have expose procedures specified in their class records, but the parent is free to ignore them, instead drawing the contents of the child itself. This can potentially save graphics context switch- ing. The precise contents of the exposure event and region arguments to the RectObj expose procedure are not specified 357 X Toolkit Intrinsics X11 Release 6.4 by the Intrinsics; a particular rectangle object is free to define the coordinate system origin (self-relative or par- ent-relative) and whether or not the rectangle or region is assumed to have been intersected with the visible region of the object. In general, it is expected that a composite widget that accepts nonwidget children will document those children it is able to handle, since a gadget cannot be viewed as a com- pletely self-contained entity, as can a widget. Since a particular composite widget class is usually designed to handle nonwidget children of only a limited set of classes, it should check the classes of newly added children in its insert_child procedure to make sure that it can deal with them. The Intrinsics will clear areas of a parent window obscured by rectobj children, causing exposure events, under the fol- lowing circumstances: o A rectobj child is managed or unmanaged. o In a call to XtSetValues on a rectobj child, one or more of the set_values procedures returns True. o In a call to XtConfigureWidget on a rectobj child, areas will be cleared corresponding to both the old and the new child geometries, including the border, if the geometry changes. o In a call to XtMoveWidget on a rectobj child, areas will be cleared corresponding to both the old and the new child geometries, including the border, if the geometry changes. o In a call to XtResizeWidget on a rectobj child, a sin- gle rectangle will be cleared corresponding to the larger of the old and the new child geometries if they are different. o In a call to XtMakeGeometryRequest (or XtMakeResiz- eRequest) on a rectobj child with XtQueryOnly not set, if the manager returns XtGeometryYes, two rectangles will be cleared corresponding to both the old and the new child geometries. Stacking order is not supported for rectobj children. Com- posite widgets with rectobj children are free to define any semantics desired if the child geometries overlap, including making this an error. When a rectobj is playing the role of a widget, developers must be reminded to avoid making assumptions about the object passed in the Widget argument to a callback 358 X Toolkit Intrinsics X11 Release 6.4 procedure. 12.4. Undeclared Class The Intrinsics define an unnamed class between RectObj and Core for possible future use by the X Consortium. The only assumptions that may be made about the unnamed class are o The core_class.superclass field of coreWidgetClassRec contains a pointer to the unnamed class record. o A pointer to the unnamed class record when dereferenced as an ObjectClass will contain a pointer to rectObj- ClassRec in its object_class.superclass field. Except for the above, the contents of the class record for this class and the result of an attempt to subclass or to create a widget of this unnamed class are undefined. 12.5. Widget Arguments to Intrinsics Routines The WidgetClass arguments to the following procedures must be of class Shell or a subclass: XtCreatePopupShell, XtVaCreatePopupShell, XtAppCre- ateShell, XtVaAppCreateShell, XtOpenApplication, XtVaOpenApplication The Widget arguments to the following procedures must be of class Core or any subclass: XtCreatePopupShell, XtVaCreatePopupShell XtAddEventHandler, XtAddRawEventHandler, XtRemoveEven- tHandler, XtRemoveRawEventHandler, XtInsertEventHandler, XtInser- tRawEventHandler XtInsertEventTypeHandler, XtRemoveEventTypeHandler, XtRegisterDrawable XtDispatchEventToWidget XtAddGrab, XtRemoveGrab, XtGrabKey, XtGrabKeyboard, XtUngrabKey, XtUngrabKeyboard, XtGrabButton, XtGrab- Pointer, XtUngrabButton, XtUngrabPointer XtBuildEventMask 359 X Toolkit Intrinsics X11 Release 6.4 XtCreateWindow, XtDisplay, XtScreen, XtWindow XtNameToWidget XtGetSelectionValue, XtGetSelectionValues, XtOwnSelec- tion, XtDisownSelection, XtOwnSelectionIncremental, XtGetSelectionValueIncremental, XtGetSelectionValuesIn- cremental, XtGetSelectionRequest XtInstallAccelerators, XtInstallAllAccelerators (both destination and source) XtAugmentTranslations, XtOverrideTranslations, XtUnin- stallTranslations, XtCallActionProc XtMapWidget, XtUnmapWidget XtRealizeWidget, XtUnrealizeWidget XtSetMappedWhenManaged XtCallAcceptFocus, XtSetKeyboardFocus (subtree) XtResizeWindow XtSetWMColormapWindows The Widget arguments to the following procedures must be of class Composite or any subclass: XtCreateManagedWidget, XtVaCreateManagedWidget The Widget arguments to the following procedures must be of a subclass of Shell: XtPopdown, XtCallbackPopdown, XtPopup, XtCallbackNone, XtCallbackNonexclusive, XtCallbackExclusive, XtPopup- SpringLoaded The return value of the following procedure will be of class Core or a subclass: XtWindowToWidget 360 X Toolkit Intrinsics X11 Release 6.4 The return value of the following procedures will be of a subclass of Shell: XtAppCreateShell, XtVaAppCreateShell, XtAppInitialize, XtVaAppInitialize, XtCreatePopupShell, XtVaCreatePopup- Shell 361 X Toolkit Intrinsics X11 Release 6.4 Chapter 13 Evolution of the Intrinsics The interfaces described by this specification have under- gone several sets of revisions in the course of adoption as an X Consortium standard specification. Having now been adopted by the Consortium as a standard part of the X Window System, it is expected that this and future revisions will retain backward compatibility in the sense that fully con- forming implementations of these specifications may be pro- duced that provide source compatibility with widgets and applications written to previous Consortium standard revi- sions. The Intrinsics do not place any special requirement on wid- get programmers to retain source or binary compatibility for their widgets as they evolve, but several conventions have been established to assist those developers who want to pro- vide such compatibility. In particular, widget programmers may wish to conform to the convention described in Section 1.6.12 when defining class extension records. 13.1. Determining Specification Revision Level Widget and application developers who wish to maintain a common source pool that will build properly with implementa- tions of the Intrinsics at different revision levels of these specifications but that take advantage of newer fea- tures added in later revisions may use the symbolic macro XtSpecificationRelease. #define XtSpecificationRelease 6 As the symbol XtSpecificationRelease was new to Release 4, widgets and applications desiring to build against earlier implementations should test for the presence of this symbol and assume only Release 3 interfaces if the definition is not present. 362 X Toolkit Intrinsics X11 Release 6.4 13.2. Release 3 to Release 4 Compatibility At the data structure level, Release 4 retains binary com- patibility with Release 3 (the first X Consortium standard release) for all data structures except WMShellPart, TopLevelShellPart, and TransientShellPart. Release 4 changed the argument type to most procedures that now take arguments of type XtPointer and structure members that are now of type XtPointer in order to avoid potential ANSI C conformance problems. It is expected that most implementa- tions will be binary compatible with the previous defini- tion. Two fields in CoreClassPart were changed from Boolean to XtEnum to allow implementations additional freedom in speci- fying the representations of each. This change should require no source modification. 13.2.1. Additional Arguments Arguments were added to the procedure definitions for XtInitProc, XtSetValuesFunc, and XtEventHandler to provide more information and to allow event handlers to abort fur- ther dispatching of the current event (caution is advised!). The added arguments to XtInitProc and XtSetValuesFunc make the initialize_hook and set_values_hook methods obsolete, but the hooks have been retained for those widgets that used them in Release 3. 13.2.2. set_values_almost Procedures The use of the arguments by a set_values_almost procedure was poorly described in Release 3 and was inconsistent with other conventions. The current specification for the manner in which a set_val- ues_almost procedure returns information to the Intrinsics is not compatible with the Release 3 specification, and all widget implementations should verify that any set_val- ues_almost procedures conform to the current interface. No known implementation of the Intrinsics correctly imple- mented the Release 3 interface, so it is expected that the impact of this specification change is small. 13.2.3. Query Geometry A composite widget layout routine that calls XtQueryGeometry is now expected to store the complete new geometry in the intended structure; previously the specification said ``store the changes it intends to make''. Only by storing 363 X Toolkit Intrinsics X11 Release 6.4 the complete geometry does the child have any way to know what other parts of the geometry may still be flexible. Existing widgets should not be affected by this, except to take advantage of the new information. 13.2.4. unrealizeCallback Callback List In order to provide a mechanism for widgets to be notified when they become unrealized through a call to XtUnreal- izeWidget, the callback list name ``unrealizeCallback'' has been defined by the Intrinsics. A widget class that requires notification on unrealize may declare a callback list resource by this name. No class is required to declare this resource, but any class that did so in a prior revision may find it necessary to modify the resource name if it does not wish to use the new semantics. 13.2.5. Subclasses of WMShell The formal adoption of the Inter-Client Communication Con- ventions Manual as an X Consortium standard has meant the addition of four fields to WMShellPart and one field to TopLevelShellPart. In deference to some widget libraries that had developed their own additional conventions to pro- vide binary compatibility, these five new fields were added at the end of the respective data structures. To provide more convenience for TransientShells, a field was added to the previously empty TransientShellPart. On some architectures the size of the part structure will not have changed as a result of this. Any widget implementation whose class is a subclass of TopLevelShell or TransientShell must at minimum be recom- piled with the new data structure declarations. Because WMShellPart no longer contains a contiguous XSizeHints data structure, a subclass that expected to do a single structure assignment of an XSizeHints structure to the size_hints field of WMShellPart must be revised, though the old fields remain at the same positions within WMShellPart. 13.2.6. Resource Type Converters A new interface declaration for resource type converters was defined to provide more information to converters, to sup- port conversion cache cleanup with resource reference count- ing, and to allow additional procedures to be declared to free resources. The old interfaces remain (in the compati- bility section), and a new set of procedures was defined that work only with the new type converter interface. 364 X Toolkit Intrinsics X11 Release 6.4 In the now obsolete old type converter interface, converters are reminded that they must return the size of the converted value as well as its address. The example indicated this, but the description of XtConverter was incomplete. 13.2.7. KeySym Case Conversion Procedure The specification for the XtCaseProc function type has been changed to match the Release 3 implementation, which included necessary additional information required by the function (a pointer to the display connection), and corrects the argument type of the source KeySym parameter. No known implementation of the Intrinsics implemented the previously documented interface. 13.2.8. Nonwidget Objects Formal support for nonwidget objects is new to Release 4. A prototype implementation was latent in at least one Release 3 implementation of the Intrinsics, but the specification has changed somewhat. The most significant change is the requirement for a composite widget to declare the Composite- ClassExtension record with the accepts_objects field set to True in order to permit a client to create a nonwidget child. The addition of this extension field ensures that composite widgets written under Release 3 will not encounter unex- pected errors if an application attempts to create a nonwid- get child. In Release 4 there is no requirement that all composite widgets implement the extra functionality required to manage windowless children, so the accept_objects field allows a composite widget to declare that it is not prepared to do so. 13.3. Release 4 to Release 5 Compatibility At the data structure level, Release 5 retains complete binary compatibility with Release 4. The specification of the ObjectPart, RectObjPart, CorePart, CompositePart, Shell- Part, WMShellPart, TopLevelShellPart, and ApplicationShell- Part instance records was made less strict to permit imple- mentations to add internal fields to these structures. Any implementation that chooses to do so would, of course, force a recompilation. The Xlib specification for XrmValue and XrmOptionDescRec was updated to use a new type, XPointer, for the addr and value fields, respectively, to avoid ANSI C conformance problems. The definition of XPointer is binary compatible with the previous implementation. 365 X Toolkit Intrinsics X11 Release 6.4 13.3.1. baseTranslations Resource A new pseudo-resource, XtNbaseTranslations, was defined to permit application developers to specify translation tables in application defaults files while still giving end users the ability to augment or override individual event sequences. This change will affect only those applications that wish to take advantage of the new functionality or those widgets that may have previously defined a resource named ``baseTranslations''. Applications wishing to take advantage of the new function- ality would change their application defaults file, e.g., from app.widget.translations: value to app.widget.baseTranslations: value If it is important to the application to preserve complete compatibility of the defaults file between different ver- sions of the application running under Release 4 and Release 5, the full translations can be replicated in both the ``translations'' and the ``baseTranslations'' resource. 13.3.2. Resource File Search Path The current specification allows implementations greater flexibility in defining the directory structure used to hold the application class and per-user application defaults files. Previous specifications required the substitution strings to appear in the default path in a certain order, preventing sites from collecting all the files for a spe- cific application together in one directory. The Release 5 specification allows the default path to specify the substi- tution strings in any order within a single path entry. Users will need to pay close attention to the documentation for the specific implementation to know where to find these files and how to specify their own XFILESEARCHPATH and XUSERFILESEARCHPATH values when overriding the system defaults. 13.3.3. Customization Resource XtResolvePathname supports a new substitution string, %C, for specifying separate application class resource files according to arbitrary user-specified categories. The 366 X Toolkit Intrinsics X11 Release 6.4 primary motivation for this addition was separate monochrome and color application class defaults files. The substitu- tion value is obtained by querying the current resource database for the application resource name ``customiza- tion'', class ``Customization''. Any application that pre- viously used this resource name and class will need to be aware of the possibly conflicting semantics. 13.3.4. Per-Screen Resource Database To allow a user to specify separate preferences for each screen of a display, a per-screen resource specification string has been added and multiple resource databases are created; one for each screen. This will affect any applica- tion that modified the (formerly unique) resource database associated with the display subsequent to the Intrinsics database initialization. Such applications will need to be aware of the particular screen on which each shell widget is to be created. Although the wording of the specification changed substan- tially in the description of the process by which the resource database(s) is initialized, the net effect is the same as in prior releases with the exception of the added per-screen resource specification and the new customization substitution string in XtResolvePathname. 13.3.5. Internationalization of Applications Internationalization as defined by ANSI is a technology that allows support of an application in a single locale. In adding support for internationalization to the Intrinsics the restrictions of this model have been followed. In par- ticular, the new Intrinsics interfaces are designed not to preclude an application from using other alternatives. For this reason, no Intrinsics routine makes a call to establish the locale. However, a convenience routine to establish the locale at initialize time has been provided, in the form of a default procedure that must be explicitly installed if the application desires ANSI C locale behavior. As many objects in X, particularly resource databases, now inherit the global locale when they are created, applica- tions wishing to use the ANSI C locale model should use the new function XtSetLanguageProc to do so. The internationalization additions also define event filters as a part of the Xlib Input Method specifications. The Intrinsics enable the use of event filters through additions to XtDispatchEvent. Applications that may not be 367 X Toolkit Intrinsics X11 Release 6.4 dispatching all events through XtDispatchEvent should be reviewed in the context of this new input method mechanism. In order to permit internationalization of error messages, the name and path of the error database file are now allowed to be implementation-dependent. No adequate standard mecha- nism has yet been suggested to allow the Intrinsics to locate the database from localization information supplied by the client. The previous specification for the syntax of the language string specified by xnlLanguage has been dropped to avoid potential conflicts with other standards. The language string syntax is now implementation-defined. The example syntax cited is consistent with the previous specification. 13.3.6. Permanently Allocated Strings In order to permit additional memory savings, an Xlib inter- face was added to allow the resource manager to avoid copy- ing certain string constants. The Intrinsics specification was updated to explicitly require the Object class_name, resource_name, resource_class, resource_type, default_type in resource tables, Core actions string field, and Con- straint resource_name, resource_class, resource_type, and default_type resource fields to be permanently allocated. This explicit requirement is expected to affect only appli- cations that may create and destroy classes on the fly. 13.3.7. Arguments to Existing Functions The args argument to XtAppInitialize, XtVaAppInitialize, XtOpenDisplay, XtDisplayInitialize, and XtInitialize were changed from Cardinal* to int* to conform to pre-existing convention and avoid otherwise annoying typecasting in ANSI C environments. 13.4. Release 5 to Release 6 Compatibility At the data structure level, Release 6 retains binary com- patibility with Release 5 for all data structures except WMShellPart. Three resources were added to the specifica- tion. The known implementations had unused space in the data structure, therefore on some architectures and imple- mentations, the size of the part structure will not have changed as a result of this. 368 X Toolkit Intrinsics X11 Release 6.4 13.4.1. Widget Internals Two new widget methods for instance allocation and dealloca- tion were added to the Object class. These new methods allow widgets to be treated as C++ objects in the C++ envi- ronment when an appropriate allocation method is specified or inherited by the widget class. The textual descriptions of the processes of widget creation and widget destruction have been edited to provide clarifi- cation to widget writers. Widgets writers may have reason to rely on the specific order of the stages of widget cre- ation and destruction; with that motivation, the specifica- tion now more exactly describes the process. As a convenience, an interface to locate a widget class extension record on a linked list, XtGetClassExtension, has been added. A new option to allow bundled changes to the managed set of a Composite widget is introduced in the Composite class extension record. Widgets that define a change_managed pro- cedure that can accommodate additions and deletions to the managed set of children in a single invocation should set allows_change_managed_set to True in the extension record. The wording of the process followed by XtUnmanageChildren has changed slightly to better handle changes to the managed set during phase 2 destroy processing. A new exposure event compression flag, XtExposeNoRegion, was added. Many widgets specify exposure compression, but either ignore the actual damage region passed to the core expose procedure or use only the cumulative bounding box data available in the event. Widgets with expose procedures that do not make use of exact exposure region information can indicate that the Intrinsics need not compute the region. 13.4.2. General Application Development XtOpenApplication is a new convenience procedure to initial- ize the toolkit, create an application context, open an X display connection, and create the root of the widget instance tree. It is identical to the interface it replaces, XtAppInitialize, in all respects except that it takes an additional argument specifying the widget class of the root shell to create. This interface is now the recom- mended one so that clients may easily become session partic- ipants. The old convenience procedures appear in the com- patibility section. 369 X Toolkit Intrinsics X11 Release 6.4 The toolkit initialization function XtToolkitInitialize may be called multiple times without penalty. In order to optimize changes in geometry to a set of geome- try-managed children, a new interface, XtChangeManagedSet, has been added. 13.4.3. Communication with Window and Session Managers The revision of the Inter-Client Communication Conventions Manual as an X Consortium standard has resulted in the addi- tion of three fields to the specification of WMShellPart. These are urgency, client_leader, and window_role. The adoption of the X Session Management Protocol as an X Consortium standard has resulted in the addition of a new shell widget, SessionShell, and an accompanying subclass verification interface, XtIsSessionShell. This widget pro- vides support for communication between an application and a session manager, as well as a window manager. In order to preserve compatibility with existing subclasses of Applica- tionShell, the ApplicationShell was subclassed to create the new widget class. The session protocol requires a modal response to certain checkpointing operations by participat- ing applications. The SessionShell structures the applica- tion's notification of and responses to messages from the session manager by use of various callback lists and by use of the new interfaces XtSessionGetToken and XtSessionReturn- Token. There is also a new command line argument, -xtses- sionID, which facilitates the session manager in restarting applications based on the Intrinsics. The resource name and class strings defined by the Intrin- sics shell widgets in are now listed in Appendix E. The addition of a new symbol for the WMShell wait_for_wm resource was made to bring the external symbol and the string it represents into agreement. The actual resource name string in WMShell has not changed. The resource representation type of the XtNwinGravity resource of the WMShell was changed to XtRGravity in order to regis- ter a type converter so that window gravity resource values could be specified by name. 13.4.4. Geometry Management A clarification to the specification was made to indicate that geometry requests may include current values along with the requested changes. 370 X Toolkit Intrinsics X11 Release 6.4 13.4.5. Event Management In Release 6, support is provided for registering selectors and event handlers for events generated by X protocol exten- sions and for dispatching those events to the appropriate widget. The new event handler registration interfaces are XtInsertEventTypeHandler and XtRemoveEventTypeHandler. Since the mechanism to indicate selection of extension events is specific to the extension being used, the Intrin- sics introduces XtRegisterExtensionSelector, which allows the application to select for the events of interest. In order to change the dispatching algorithm to accommodate extension events as well as core X protocol events, the Intrinsics event dispatcher may now be replaced or enveloped by the application with XtSetEventDispatcher. The dis- patcher may wish to call XtGetKeyboardFocusWidget to deter- mine the widget with the current Intrinsics keyboard focus. A dispatcher, after determining the destination widget, may use XtDispatchEventToWidget to cause the event to be dis- patched to the event handlers registered by a specific wid- get. To permit the dispatching of events for nonwidget drawables, such as pixmaps that are not associated with a widget's win- dow, XtRegisterDrawable and XtUnregisterDrawable have been added to the library. A related update was made to the description of XtWindowToWidget. The library is now thread-safe, allowing one thread at a time to enter the library and protecting global data as nec- essary from concurrent use. Threaded toolkit applications are supported by the new interfaces XtToolkitThreadInitial- ize, XtAppLock, XtAppUnlock, XtAppSetExitFlag, and XtAppGe- tExitFlag. Widget writers may also use XtProcessLock and XtProcessUnlock. Safe handling of POSIX signals and other asynchronous noti- fications is now provided by use of XtAppAddSignal, XtNo- ticeSignal, and XtRemoveSignal. The application can receive notification of an impending block in the Intrinsics event manager by registering inter- est through XtAppAddBlockHook and XtRemoveBlockHook. XtLastEventProcessed returns the most recent event passed to XtDispatchEvent for a specified display. 13.4.6. Resource Management Resource converters are registered by the Intrinsics for window gravity and for three new resource types associated with session participation: RestartStyle, CommandArgArray and DirectoryString. 371 X Toolkit Intrinsics X11 Release 6.4 The file search path syntax has been extended to make it easier to include the default search path, which controls resource database construction, by using the new substitu- tion string, %D. 13.4.7. Translation Management The default key translator now recognizes the NumLock modi- fier. If NumLock is on and the second keysym is a keypad keysym (a standard keysym named with a ``KP'' prefix or a vendor-specific keysym in the hexadecimal range 0x11000000 to 0x1100FFFF), then the default key translator will use the first keysym if Shift and/or ShiftLock is on and will use the second keysym if neither is on. Otherwise, it will ignore NumLock and apply the normal protocol semantics. 13.4.8. Selections The targets of selection requests may be parameterized, as described by the revised Inter-Client Communication Conven- tions Manual. When such requests are made, XtSetSelection- Parameters is used by the requestor to specify the target parameters and XtGetSelectionParameters is used by the selection owner to retrieve the parameters. When a parame- terized target is specified in the context of a bundled request for multiple targets, XtCreateSelectionRequest, XtCancelSelectionRequest, and XtSendSelectionRequest are used to envelop the assembly of the request. When the parameters themselves are the names of properties, the Intrinsics provides support for the economical use of prop- erty atom names; see XtReservePropertyAtom and XtRelease- PropertyAtom. 13.4.9. External Agent Hooks External agent hooks were added for the benefit of applica- tions that instrument other applications for purposes of accessibility, testing, and customization. The external agent and the application communicate by a shared protocol which is transparent to the application. The hook callbacks permit the external agent to register interest in groups or classes of toolkit activity and to be notified of the type and details of the activity as it occurs. The new inter- faces related to this effort are XtHooksOfDisplay, which returns the hook registration widget, and XtGetDisplays, which returns a list of the X displays associated with an application context. 372 X Toolkit Intrinsics X11 Release 6.4 Appendix A Resource File Format A resource file contains text representing the default resource values for an application or set of applications. The format of resource files is defined by Xlib -- C Lan- guage X Interface and is reproduced here for convenience only. The format of a resource specification is ResourceLine = Comment | IncludeFile | ResourceSpec | Comment = ``!'' {} IncludeFile = ``#'' WhiteSpace ``include'' WhiteSpace FileName WhiteSpace FileName = ResourceSpec = WhiteSpace ResourceName WhiteSpace ``:'' WhiteSpace Value ResourceName = [Binding] {Component Binding} ComponentName Binding = ``.'' | ``*'' WhiteSpace = { | } Component = ``?'' | ComponentName ComponentName = NameChar {NameChar} NameChar = ``a''-``z'' | ``A''-``Z'' | ``0''-``9'' | ``_'' | ``-'' Value = {} Elements separated by vertical bar (|) are alternatives. Curly braces ({...}) indicate zero or more repetitions of the enclosed elements. Square brackets ([...]) indicate that the enclosed element is optional. Quotes (``...'') are used around literal characters. If the last character on a line is a backslash (\), that line is assumed to continue on the next line. To allow a Value to begin with whitespace, the two-character sequence ``\space'' (backslash followed by space) is recog- nized and replaced by a space character, and the two-charac- ter sequence ``\tab'' (backslash followed by horizontal tab) is recognized and replaced by a horizontal tab character. To allow a Value to contain embedded newline characters, the two-character sequence ``\n'' is recognized and replaced by a newline character. To allow a Value to be broken across multiple lines in a text file, the two-character sequence ``\newline'' (backslash followed by newline) is recognized and removed from the value. To allow a Value to contain arbitrary character codes, the 373 X Toolkit Intrinsics X11 Release 6.4 four-character sequence ``\nnn'', where each n is a digit character in the range of ``0''-``7'', is recognized and replaced with a single byte that contains the octal value specified by the sequence. Finally, the two-character sequence ``\\'' is recognized and replaced with a single backslash. 374 X Toolkit Intrinsics X11 Release 6.4 Appendix B Translation Table Syntax Notation Syntax is specified in EBNF notation with the following con- ventions: [ a ] Means either nothing or ``a'' { a } Means zero or more occurrences of ``a'' ( a | b ) Means either ``a'' or ``b'' \\n Is the newline character All terminals are enclosed in double quotation marks (`` ''). Informal descriptions are enclosed in angle brackets (< >). Syntax The syntax of a translation table is translationTable = [ directive ] { production } directive = ( ``#replace'' | ``#override'' | ``#augment'' ) ``\\n'' production = lhs ``:'' rhs ``\\n'' lhs = ( event | keyseq ) { ``,'' (event | keyseq) } keyseq = ``"'' keychar {keychar} ``"'' keychar = [ ``^'' | ``$'' | ``\\'' ] event = [modifier_list] ``<''event_type``>'' [ ``('' count[``+''] ``)'' ] {detail} modifier_list = ( [``!''] [``:''] {modifier} ) | ``None'' modifier = [``~''] modifier_name count = (``1'' | ``2'' | ``3'' | ``4'' | ...) modifier_name = ``@'' | event_type = detail = rhs = { name ``('' [params] ``)'' } name = namechar { namechar } namechar = { ``a''-``z'' | ``A''-``Z'' | ``0''-``9'' | ``_'' | ``-'' } params = string {``,'' string} string = quoted_string | unquoted_string quoted_string = ``"'' { | escape_char} [``\\\\'' ] ``"'' escape_char = ``\\"'' unquoted_string = {} The params field is parsed into a list of String values that will be passed to the named action procedure. A quoted 375 X Toolkit Intrinsics X11 Release 6.4 string may contain an embedded quotation mark if the quota- tion mark is preceded by a single backslash (\). The three- character sequence ``\\"'' is interpreted as ``single back- slash followed by end-of-string''. Modifier Names The modifier field is used to specify standard X keyboard and button modifier mask bits. Modifiers are legal on event types KeyPress, KeyRelease, ButtonPress, ButtonRelease, MotionNotify, EnterNotify, LeaveNotify, and their abbrevia- tions. An error is generated when a translation table that contains modifiers for any other events is parsed. o If the modifier list has no entries and is not ``None'', it means ``don't care'' on all modifiers. o If an exclamation point (!) is specified at the begin- ning of the modifier list, it means that the listed modifiers must be in the correct state and no other modifiers can be asserted. o If any modifiers are specified and an exclamation point (!) is not specified, it means that the listed modi- fiers must be in the correct state and ``don't care'' about any other modifiers. o If a modifier is preceded by a tilde (~), it means that that modifier must not be asserted. o If ``None'' is specified, it means no modifiers can be asserted. o If a colon (:) is specified at the beginning of the modifier list, it directs the Intrinsics to apply any standard modifiers in the event to map the event key- code into a KeySym. The default standard modifiers are Shift and Lock, with the interpretation as defined in X Window System Protocol, Section 5. The resulting KeySym must exactly match the specified KeySym, and the nonstandard modifiers in the event must match the modi- fier list. For example, ``:a'' is distinct from ``:A'', and ``:ShiftA'' is distinct from ``:A''. o If both an exclamation point (!) and a colon (:) are specified at the beginning of the modifier list, it means that the listed modifiers must be in the correct state and that no other modifiers except the standard modifiers can be asserted. Any standard modifiers in the event are applied as for colon (:) above. 376 X Toolkit Intrinsics X11 Release 6.4 o If a colon (:) is not specified, no standard modifiers are applied. Then, for example, ``A'' and ``a'' are equivalent. In key sequences, a circumflex (^) is an abbreviation for the Control modifier, a dollar sign ($) is an abbreviation for Meta, and a backslash (\) can be used to quote any char- acter, in particular a double quote ("), a circumflex (^), a dollar sign ($), and another backslash (\). Briefly: No modifiers: None detail Any modifiers: detail Only these modifiers: ! mod1 mod2 detail These modifiers and any others:mod1 mod2 detail The use of ``None'' for a modifier list is identical to the use of an exclamation point with no modifers. ----------------------------------------------------------- Modifier Abbreviation Meaning ----------------------------------------------------------- Ctrl c Control modifier bit Shift s Shift modifier bit Lock l Lock modifier bit Meta m Meta key modifier Hyper h Hyper key modifier Super su Super key modifier Alt a Alt key modifier Mod1 Mod1 modifier bit Mod2 Mod2 modifier bit Mod3 Mod3 modifier bit Mod4 Mod4 modifier bit Mod5 Mod5 modifier bit Button1 Button1 modifier bit Button2 Button2 modifier bit Button3 Button3 modifier bit Button4 Button4 modifier bit Button5 Button5 modifier bit None No modifiers Any Any modifier combination ----------------------------------------------------------- A key modifier is any modifier bit one of whose correspond- ing KeyCodes contains the corresponding left or right KeySym. For example, ``m'' or ``Meta'' means any modifier bit mapping to a KeyCode whose KeySym list contains XK_Meta_L or XK_Meta_R. Note that this interpretation is for each display, not global or even for each application context. The Control, Shift, and Lock modifier names refer explicitly to the corresponding modifier bits; there is no 377 X Toolkit Intrinsics X11 Release 6.4 additional interpretation of KeySyms for these modifiers. Because it is possible to associate arbitrary KeySyms with modifiers, the set of key modifiers is extensible. The ``@'' syntax means any modifier bit whose corre- sponding KeyCode contains the specified KeySym name. A modifier_list/KeySym combination in a translation matches a modifiers/KeyCode combination in an event in the following ways: 1. If a colon (:) is used, the Intrinsics call the dis- play's XtKeyProc with the KeyCode and modifiers. To match, (modifiers & ~modifiers_return) must equal modi- fier_list, and keysym_return must equal the given KeySym. 2. If (:) is not used, the Intrinsics mask off all don't- care bits from the modifiers. This value must be equal to modifier_list. Then, for each possible combination of don't-care modifiers in the modifier list, the Intrinsics call the display's XtKeyProc with the Key- Code and that combination ORed with the cared-about modifier bits from the event. Keysym_return must match the KeySym in the translation. Event Types The event-type field describes XEvent types. In addition to the standard Xlib symbolic event type names, the following event type synonyms are defined: ------------------------------------------------- Type Meaning ------------------------------------------------- Key KeyPress KeyDown KeyPress KeyUp KeyRelease BtnDown ButtonPress BtnUp ButtonRelease Motion MotionNotify PtrMoved MotionNotify MouseMoved MotionNotify Enter EnterNotify EnterWindow EnterNotify Leave LeaveNotify LeaveWindow LeaveNotify FocusIn FocusIn FocusOut FocusOut Keymap KeymapNotify Expose Expose GrExp GraphicsExpose NoExp NoExpose 378 X Toolkit Intrinsics X11 Release 6.4 ------------------------------------------------- Type Meaning ------------------------------------------------- Visible VisibilityNotify Create CreateNotify Destroy DestroyNotify Unmap UnmapNotify Map MapNotify MapReq MapRequest Reparent ReparentNotify Configure ConfigureNotify ConfigureReq ConfigureRequest Grav GravityNotify ResReq ResizeRequest Circ CirculateNotify CircReq CirculateRequest Prop PropertyNotify SelClr SelectionClear SelReq SelectionRequest Select SelectionNotify Clrmap ColormapNotify Message ClientMessage Mapping MappingNotify ------------------------------------------------- The supported abbreviations are: ---------------------------------------------------------- Abbreviation Event Type Including ---------------------------------------------------------- Ctrl KeyPress with Control modifier Meta KeyPress with Meta modifier Shift KeyPress with Shift modifier Btn1Down ButtonPress with Button1 detail Btn1Up ButtonRe- with Button1 detail lease Btn2Down ButtonPress with Button2 detail Btn2Up ButtonRe- with Button2 detail lease Btn3Down ButtonPress with Button3 detail Btn3Up ButtonRe- with Button3 detail lease Btn4Down ButtonPress with Button4 detail Btn4Up ButtonRe- with Button4 detail lease Btn5Down ButtonPress with Button5 detail Btn5Up ButtonRe- with Button5 detail lease BtnMotion MotionNotify with any button modifier Btn1Motion MotionNotify with Button1 modifier Btn2Motion MotionNotify with Button2 modifier Btn3Motion MotionNotify with Button3 modifier Btn4Motion MotionNotify with Button4 modifier 379 X Toolkit Intrinsics X11 Release 6.4 ---------------------------------------------------------- Abbreviation Event Type Including ---------------------------------------------------------- Btn5Motion MotionNotify with Button5 modifier ---------------------------------------------------------- The detail field is event-specific and normally corresponds to the detail field of the corresponding event as described by X Window System Protocol, Section 11. The detail field is supported for the following event types: ------------------------------------------------------ Event Event Field ------------------------------------------------------ KeyPress KeySym from event detail (keycode) KeyRelease KeySym from event detail (keycode) ButtonPress button from event detail ButtonRelease button from event detail MotionNotify event detail EnterNotify event mode LeaveNotify event mode FocusIn event mode FocusOut event mode PropertyNotify atom SelectionClear selection SelectionRequest selection SelectionNotify selection ClientMessage type MappingNotify request ------------------------------------------------------ If the event type is KeyPress or KeyRelease, the detail field specifies a KeySym name in standard format which is matched against the event as described above, for example, A. For the PropertyNotify, SelectionClear, SelectionRequest, SelectionNotify, and ClientMessage events the detail field is specified as an atom name; for example, WM_PRO- TOCOLS. For the MotionNotify, EnterNotify, LeaveNotify, FocusIn, FocusOut, and MappingNotify events, either the sym- bolic constants as defined by X Window System Protocol, Sec- tion 11, or the numeric values may be specified. If no detail field is specified, then any value in the event detail is accepted as a match. A KeySym can be specified as any of the standard KeySym names, a hexadecimal number prefixed with ``0x'' or ``0X'', an octal number prefixed with ``0'', or a decimal number. A 380 X Toolkit Intrinsics X11 Release 6.4 KeySym expressed as a single digit is interpreted as the corresponding Latin 1 KeySym, for example, ``0'' is the KeySym XK_0. Other single character KeySyms are treated as literal constants from Latin 1, for example, ``!'' is treated as 0x21. Standard KeySym names are as defined in with the ``XK_'' prefix removed. Canonical Representation Every translation table has a unique, canonical text repre- sentation. This representation is passed to a widget's dis- play_accelerator procedure to describe the accelerators installed on that widget. The canonical representation of a translation table is (see also ``Syntax'') translationTable = { production } production = lhs ``:'' rhs ``\\n'' lhs = event { ``,'' event } event = [modifier_list] ``<''event_type``>'' [ ``('' count[``+''] ``)'' ] {detail} modifier_list = [``!''] [``:''] {modifier} modifier = [``~''] modifier_name count = (``1'' | ``2'' | ``3'' | ``4'' | ...) modifier_name = ``@'' | event_type = detail = rhs = { name ``('' [params] ``)'' } name = namechar { namechar } namechar = { ``a''-``z'' | ``A''-``Z'' | ``0''-``9'' | ``_'' | ``-'' } params = string {``,'' string} string = quoted_string quoted_string = ``"'' { | escape_char} [``\\\\'' ] ``"'' escape_char = ``\\"'' The canonical modifier names are Ctrl Mod1 Button1 Shift Mod2 Button2 Lock Mod3 Button3 Mod4 Button4 Mod5 Button5 The canonical event types are KeyPress KeyRelease ButtonPress ButtonRelease MotionNotify EnterNotify LeaveNotify FocusIn FocusOut KeymapNotify 381 X Toolkit Intrinsics X11 Release 6.4 Expose GraphicsExpose, NoExpose VisibilityNotify CreateNotify DestroyNotify UnmapNotify MapNotify MapRequest ReparentNotify ConfigureNotify ConfigureRequest GravityNotify ResizeRequest CirculateNotify CirculateRequest PropertyNotify SelectionClear SelectionRequest SelectionNotify ColormapNotify ClientMessage Examples o Always put more specific events in the table before more general ones: Shift : twas()\n\ : brillig() o For double-click on Button1 Up with Shift, use this specification: Shift(2) : and() This is equivalent to the following line with appropri- ate timers set between events: Shift,Shift,Shift,Shift : and() o For double-click on Button1 Down with Shift, use this specification: Shift(2) : the() This is equivalent to the following line with appropri- ate timers set between events: Shift,Shift,Shift : the() 382 X Toolkit Intrinsics X11 Release 6.4 o Mouse motion is always discarded when it occurs between events in a table where no motion event is specified: , : slithy() This is taken, even if the pointer moves a bit between the down and up events. Similarly, any motion event specified in a translation matches any number of motion events. If the motion event causes an action procedure to be invoked, the procedure is invoked after each motion event. o If an event sequence consists of a sequence of events that is also a noninitial subsequence of another trans- lation, it is not taken if it occurs in the context of the longer sequence. This occurs mostly in sequences like the following: , : toves()\n\ : did() The second translation is taken only if the button release is not preceded by a button press or if there are intervening events between the press and the release. Be particularly aware of this when using the repeat notation, above, with buttons and keys, because their expansion includes additional events; and when specifying motion events, because they are implicitly included between any two other events. In particular, pointer motion and double-click translations cannot coexist in the same translation table. o For single click on Button1 Up with Shift and Meta, use this specification: Shift Meta , Shift Meta: gyre() o For multiple clicks greater or equal to a minimum num- ber, a plus sign (+) may be appended to the final (rightmost) count in an event sequence. The actions will be invoked on the count-th click and each subse- quent one arriving within the multi-click time inter- val. For example: Shift (2+) : and() 383 X Toolkit Intrinsics X11 Release 6.4 o To indicate EnterNotify with any modifiers, use this specification: : gimble() o To indicate EnterNotify with no modifiers, use this specification: None : in() o To indicate EnterNotify with Button1 Down and Button2 Up and ``don't care'' about the other modifiers, use this specification: Button1 ~Button2 : the() o To indicate EnterNotify with Button1 down and Button2 down exclusively, use this specification: ! Button1 Button2 : wabe() You do not need to use a tilde (~) with an exclamation point (!). 384 X Toolkit Intrinsics X11 Release 6.4 Appendix C Compatibility Functions In prototype versions of the X Toolkit each widget class implemented an XtCreate (for example, XtLabelCreate) function, in which most of the code was identical from wid- get to widget. In the Intrinsics, a single generic XtCre- ateWidget performs most of the common work and then calls the initialize procedure implemented for the particular wid- get class. Each Composite class also implemented the procedures XtAdd and an XtDelete (for example, XtButtonBoxAd- dButton and XtButtonBoxDeleteButton). In the Intrinsics, the Composite generic procedures XtManageChildren and XtUn- manageChildren perform error checking and screening out of certain children. Then they call the change_managed proce- dure implemented for the widget's Composite class. If the widget's parent has not yet been realized, the call to the change_managed procedure is delayed until realization time. Old-style calls can be implemented in the X Toolkit by defining one-line procedures or macros that invoke a generic routine. For example, you could define the macro XtLabel- Create as: #define XtLabelCreate(name, parent, args, num_args) \ ((LabelWidget) XtCreateWidget(name, labelWidgetClass, parent, args, num_args)) Pop-up shells in some of the prototypes automatically per- formed an XtManageChild on their child within their insert_child procedure. Creators of pop-up children need to call XtManageChild themselves. XtAppInitialize and XtVaAppInitialize have been replaced by XtOpenApplication and XtVaOpenApplication. To initialize the Intrinsics internals, create an applica- tion context, open and initialize a display, and create the initial application shell instance, an application may use XtAppInitialize or XtVaAppInitialize. ----------- This appendix is part of the formal Intrinsics Specification. 385 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtAppInitialize(app_context_return, application_class, options, num_options, argc_in_out, argv_in_out, fallback_resources, args, num_args) XtAppContext *app_context_return; String application_class; XrmOptionDescList options; Cardinal num_options; int *argc_in_out; String *argv_in_out; String *fallback_resources; ArgList args; Cardinal num_args; app_context_return Returns the application context, if non-NULL. application_class Specifies the class name of the application. options Specifies the command line options table. num_options Specifies the number of entries in options. argc_in_out Specifies a pointer to the number of command line arguments. argv_in_out Specifies a pointer to the command line argu- ments. fallback_resources Specifies resource values to be used if the application class resource file cannot be opened or read, or NULL. args Specifies the argument list to override any other resource specifications for the created shell widget. num_args Specifies the number of entries in the argu- ment list. |__ The XtAppInitialize function calls XtToolkitInitialize fol- lowed by XtCreateApplicationContext, then calls XtOpenDis- play with display_string NULL and application_name NULL, and finally calls XtAppCreateShell with application_name NULL, widget_class applicationShellWidgetClass, and the specified args and num_args and returns the created shell. The modi- fied argc and argv returned by XtDisplayInitialize are returned in argc_in_out and argv_in_out. If app_con- text_return is not NULL, the created application context is also returned. If the display specified by the command line cannot be opened, an error message is issued and 386 X Toolkit Intrinsics X11 Release 6.4 XtAppInitialize terminates the application. If fall- back_resources is non-NULL, XtAppSetFallbackResources is called with the value prior to calling XtOpenDisplay. __ | Widget XtVaAppInitialize(app_context_return, application_class, options, num_options, argc_in_out, argv_in_out, fallback_resources, ...) XtAppContext *app_context_return; String application_class; XrmOptionDescList options; Cardinal num_options; int *argc_in_out; String *argv_in_out; String *fallback_resources; app_context_return Returns the application context, if non-NULL. application_class Specifies the class name of the application. options Specifies the command line options table. num_options Specifies the number of entries in options. argc_in_out Specifies a pointer to the number of command line arguments. argv_in_out Specifies the command line arguments array. fallback_resources Specifies resource values to be used if the application class resource file cannot be opened, or NULL. ... Specifies the variable argument list to over- ride any other resource specifications for the created shell. |__ The XtVaAppInitialize procedure is identical in function to XtAppInitialize with the args and num_args parameters replaced by a varargs list, as described in Section 2.5.1. As a convenience to people converting from earlier versions of the toolkit without application contexts, the following routines exist: XtInitialize, XtMainLoop, XtNextEvent, XtProcessEvent, XtPeekEvent, XtPending, XtAddInput, XtAd- dTimeOut, XtAddWorkProc, XtCreateApplicationShell, XtAddAc- tions, XtSetSelectionTimeout, and XtGetSelectionTimeout. 387 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtInitialize(shell_name, application_class, options, num_options, argc, argv) String shell_name; String application_class; XrmOptionDescRec options[]; Cardinal num_options; int *argc; String argv[]; shell_name This parameter is ignored; therefore, you can specify NULL. application_class Specifies the class name of this application. options Specifies how to parse the command line for any application-specific resources. The options argu- ment is passed as a parameter to XrmParseCommand. num_options Specifies the number of entries in the options list. argc Specifies a pointer to the number of command line parameters. argv Specifies the command line parameters. |__ XtInitialize calls XtToolkitInitialize to initialize the toolkit internals, creates a default application context for use by the other convenience routines, calls XtOpenDisplay with display_string NULL and application_name NULL, and finally calls XtAppCreateShell with application_name NULL and returns the created shell. The semantics of calling XtInitialize more than once are undefined. This routine has been replaced by XtOpenApplication. __ | void XtMainLoop(void) |__ XtMainLoop first reads the next alternate input, timer, or X event by calling XtNextEvent. Then it dispatches this to the appropriate registered procedure by calling XtDis- patchEvent. This routine has been replaced by XtAppMain- Loop. 388 X Toolkit Intrinsics X11 Release 6.4 __ | void XtNextEvent(event_return) XEvent *event_return; event_return Returns the event information to the specified event structure. |__ If no input is on the X input queue for the default applica- tion context, XtNextEvent flushes the X output buffer and waits for an event while looking at the alternate input sources and timeout values and calling any callback proce- dures triggered by them. This routine has been replaced by XtAppNextEvent. XtInitialize must be called before using this routine. __ | void XtProcessEvent(mask) XtInputMask mask; mask Specifies the type of input to process. |__ XtProcessEvent processes one X event, timeout, or alternate input source (depending on the value of mask), blocking if necessary. It has been replaced by XtAppProcessEvent. XtInitialize must be called before using this function. __ | Boolean XtPeekEvent(event_return) XEvent *event_return; event_return Returns the event information to the specified event structure. |__ If there is an event in the queue for the default applica- tion context, XtPeekEvent fills in the event and returns a nonzero value. If no X input is on the queue, XtPeekEvent flushes the output buffer and blocks until input is avail- able, possibly calling some timeout callbacks in the pro- cess. If the input is an event, XtPeekEvent fills in the event and returns a nonzero value. Otherwise, the input is for an alternate input source, and XtPeekEvent returns zero. This routine has been replaced by XtAppPeekEvent. XtIni- tialize must be called before using this routine. 389 X Toolkit Intrinsics X11 Release 6.4 __ | Boolean XtPending() |__ XtPending returns a nonzero value if there are events pend- ing from the X server or alternate input sources in the default application context. If there are no events pend- ing, it flushes the output buffer and returns a zero value. It has been replaced by XtAppPending. XtInitialize must be called before using this routine. __ | XtInputId XtAddInput(source, condition, proc, client_data) int source; XtPointer condition; XtInputCallbackProc proc; XtPointer client_data; source Specifies the source file descriptor on a POSIX- based system or other operating-system-dependent device specification. condition Specifies the mask that indicates either a read, write, or exception condition or some operating- system-dependent condition. proc Specifies the procedure called when input is available. client_data Specifies the parameter to be passed to proc when input is available. |__ The XtAddInput function registers in the default application context a new source of events, which is usually file input but can also be file output. (The word file should be loosely interpreted to mean any sink or source of data.) XtAddInput also specifies the conditions under which the source can generate events. When input is pending on this source in the default application context, the callback pro- cedure is called. This routine has been replaced by XtAp- pAddInput. XtInitialize must be called before using this routine. 390 X Toolkit Intrinsics X11 Release 6.4 __ | XtIntervalId XtAddTimeOut(interval, proc, client_data) unsigned long interval; XtTimerCallbackProc proc; XtPointer client_data; interval Specifies the time interval in milliseconds. proc Specifies the procedure to be called when time expires. client_data Specifies the parameter to be passed to proc when it is called. |__ The XtAddTimeOut function creates a timeout in the default application context and returns an identifier for it. The timeout value is set to interval. The callback procedure will be called after the time interval elapses, after which the timeout is removed. This routine has been replaced by XtAppAddTimeOut. XtInitialize must be called before using this routine. __ | XtWorkProcId XtAddWorkProc(proc, client_data) XtWorkProc proc; XtPointer client_data; proc Procedure to call to do the work. client_data Client data to pass to proc when it is called. |__ This routine registers a work procedure in the default application context. It has been replaced by XtAppAd- dWorkProc. XtInitialize must be called before using this routine. 391 X Toolkit Intrinsics X11 Release 6.4 __ | Widget XtCreateApplicationShell(name, widget_class, args, num_args) String name; WidgetClass widget_class; ArgList args; Cardinal num_args; name This parameter is ignored; therefore, you can specify NULL. widget_class Specifies the widget class pointer for the created application shell widget. This will usually be topLevelShellWidgetClass or a subclass thereof. args Specifies the argument list to override any other resource specifications. num_args Specifies the number of entries in args. |__ The procedure XtCreateApplicationShell calls XtAppCre- ateShell with application_name NULL, the application class passed to XtInitialize, and the default application context created by XtInitialize. This routine has been replaced by XtAppCreateShell. An old-format resource type converter procedure pointer is of type XtConverter. __ | typedef void (*XtConverter)(XrmValue*, Cardinal*, XrmValue*, XrmValue*); XrmValue *args; Cardinal *num_args; XrmValue *from; XrmValue *to; args Specifies a list of additional XrmValue arguments to the converter if additional context is needed to perform the conversion, or NULL. num_args Specifies the number of entries in args. from Specifies the value to convert. to Specifies the descriptor to use to return the con- verted value. |__ Type converters should perform the following actions: 392 X Toolkit Intrinsics X11 Release 6.4 o Check to see that the number of arguments passed is correct. o Attempt the type conversion. o If successful, return the size and pointer to the data in the to argument; otherwise, call XtWarningMsg and return without modifying the to argument. Most type converters just take the data described by the specified from argument and return data by writing into the specified to argument. A few need other information, which is available in the specified argument list. A type con- verter can invoke another type converter, which allows dif- fering sources that may convert into a common intermediate result to make maximum use of the type converter cache. Note that the address returned in to->addr cannot be that of a local variable of the converter because this is not valid after the converter returns. It should be a pointer to a static variable. The procedure type XtConverter has been replaced by XtType- Converter. The XtStringConversionWarning function is a convenience rou- tine for old-format resource converters that convert from strings. __ | void XtStringConversionWarning(src, dst_type) String src, dst_type; src Specifies the string that could not be converted. dst_type Specifies the name of the type to which the string could not be converted. |__ The XtStringConversionWarning function issues a warning mes- sage with name ``conversionError'', type ``string'', class ``XtToolkitError, and the default message string ``Cannot convert "src" to type dst_type''. This routine has been superseded by XtDisplayStringConversionWarning. To register an old-format converter, use XtAddConverter or XtAppAddConverter. 393 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAddConverter(from_type, to_type, converter, convert_args, num_args) String from_type; String to_type; XtConverter converter; XtConvertArgList convert_args; Cardinal num_args; from_type Specifies the source type. to_type Specifies the destination type. converter Specifies the type converter procedure. convert_args Specifies how to compute the additional arguments to the converter, or NULL. num_args Specifies the number of entries in convert_args. |__ XtAddConverter is equivalent in function to XtSetTypeCon- verter with cache_type equal to XtCacheAll for old-format type converters. It has been superseded by XtSetTypeCon- verter. 394 X Toolkit Intrinsics X11 Release 6.4 __ | void XtAppAddConverter(app_context, from_type, to_type, converter, convert_args, num_args) XtAppContext app_context; String from_type; String to_type; XtConverter converter; XtConvertArgList convert_args; Cardinal num_args; app_context Specifies the application context. from_type Specifies the source type. to_type Specifies the destination type. converter Specifies the type converter procedure. convert_args Specifies how to compute the additional arguments to the converter, or NULL. num_args Specifies the number of entries in convert_args. |__ XtAppAddConverter is equivalent in function to XtAppSetType- Converter with cache_type equal to XtCacheAll for old-format type converters. It has been superseded by XtAppSetTypeCon- verter. To invoke resource conversions, a client may use XtConvert or, for old-format converters only, XtDirectConvert. 395 X Toolkit Intrinsics X11 Release 6.4 __ | void XtConvert(w, from_type, from, to_type, to_return) Widget w; String from_type; XrmValuePtr from; String to_type; XrmValuePtr to_return; w Specifies the widget to use for additional argu- ments, if any are needed. from_type Specifies the source type. from Specifies the value to be converted. to_type Specifies the destination type. to_return Returns the converted value. void XtDirectConvert(converter, args, num_args, from, to_return) XtConverter converter; XrmValuePtr args; Cardinal num_args; XrmValuePtr from; XrmValuePtr to_return; converter Specifies the conversion procedure to be called. args Specifies the argument list that contains the additional arguments needed to perform the conver- sion (often NULL). num_args Specifies the number of entries in args. from Specifies the value to be converted. to_return Returns the converted value. |__ The XtConvert function looks up the type converter regis- tered to convert from_type to to_type, computes any addi- tional arguments needed, and then calls XtDirectConvert or XtCallConverter. The XtDirectConvert function looks in the converter cache to see if this conversion procedure has been called with the specified arguments. If so, it returns a descriptor for information stored in the cache; otherwise, it calls the converter and enters the result in the cache. Before calling the specified converter, XtDirectConvert sets the return value size to zero and the return value address to NULL. To determine if the conversion was successful, the 396 X Toolkit Intrinsics X11 Release 6.4 client should check to_return.addr for non-NULL. The data returned by XtConvert must be copied immediately by the caller, as it may point to static data in the type con- verter. XtConvert has been replaced by XtConvertAndStore, and XtDi- rectConvert has been superseded by XtCallConverter. To deallocate a shared GC when it is no longer needed, use XtDestroyGC. __ | void XtDestroyGC(w, gc) Widget w; GC gc; w Specifies any object on the display for which the shared GC was created. Must be of class Object or any subclass thereof. gc Specifies the shared GC to be deallocated. |__ References to sharable GCs are counted and a free request is generated to the server when the last user of a given GC destroys it. Note that some earlier versions of XtDestroyGC had only a gc argument. Therefore, this function is not very portable, and you are encouraged to use XtReleaseGC instead. To declare an action table in the default application con- text and register it with the translation manager, use XtAd- dActions. __ | void XtAddActions(actions, num_actions) XtActionList actions; Cardinal num_actions; actions Specifies the action table to register. num_actions Specifies the number of entries in actions. |__ If more than one action is registered with the same name, the most recently registered action is used. If duplicate actions exist in an action table, the first is used. The 397 X Toolkit Intrinsics X11 Release 6.4 Intrinsics register an action table for XtMenuPopup and XtMenuPopdown as part of X Toolkit initialization. This routine has been replaced by XtAppAddActions. XtInitialize must be called before using this routine. To set the Intrinsics selection timeout in the default application context, use XtSetSelectionTimeout. __ | void XtSetSelectionTimeout(timeout) unsigned long timeout; timeout Specifies the selection timeout in milliseconds. This routine has been replaced by XtAppSetSelec- tionTimeout. XtInitialize must be called before using this routine. |__ To get the current selection timeout value in the default application context, use XtGetSelectionTimeout. __ | unsigned long XtGetSelectionTimeout() |__ The selection timeout is the time within which the two com- municating applications must respond to one another. If one of them does not respond within this interval, the Intrin- sics abort the selection request. This routine has been replaced by XtAppGetSelectionTimeout. XtInitialize must be called before using this routine. To obtain the global error database (for example, to merge with an application- or widget-specific database), use XtGetErrorDatabase. __ | XrmDatabase *XtGetErrorDatabase() |__ The XtGetErrorDatabase function returns the address of the error database. The Intrinsics do a lazy binding of the error database and do not merge in the database file until 398 X Toolkit Intrinsics X11 Release 6.4 the first call to XtGetErrorDatbaseText. This routine has been replaced by XtAppGetErrorDatabase. An error message handler can obtain the error database text for an error or a warning by calling XtGetErrorDatabaseText. __ | void XtGetErrorDatabaseText(name, type, class, default, buffer_return, nbytes) String name, type, class; String default; String buffer_return; int nbytes; name type Specify the name and type that are concatenated to form the resource name of the error message. class Specifies the resource class of the error message. default Specifies the default message to use if an error database entry is not found. buffer_return Specifies the buffer into which the error message is to be returned. nbytes Specifies the size of the buffer in bytes. |__ The XtGetErrorDatabaseText returns the appropriate message from the error database associated with the default applica- tion context or returns the specified default message if one is not found in the error database. To form the full resource name and class when querying the database, the name and type are concatenated with a single ``.'' between them and the class is concatenated with itself with a single ``.'' if it does not already contain a ``.''. This routine has been superseded by XtAppGetErrorDatabaseText. To register a procedure to be called on fatal error condi- tions, use XtSetErrorMsgHandler. 399 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetErrorMsgHandler(msg_handler) XtErrorMsgHandler msg_handler; msg_handler Specifies the new fatal error procedure, which should not return. |__ The default error handler provided by the Intrinsics con- structs a string from the error resource database and calls XtError. Fatal error message handlers should not return. If one does, subsequent Intrinsics behavior is undefined. This routine has been superseded by XtAppSetErrorMsgHandler. To call the high-level error handler, use XtErrorMsg. __ | void XtErrorMsg(name, type, class, default, params, num_params) String name; String type; String class; String default; String *params; Cardinal *num_params; name Specifies the general kind of error. type Specifies the detailed name of the error. class Specifies the resource class. default Specifies the default message to use if an error database entry is not found. params Specifies a pointer to a list of values to be stored in the message. num_params Specifies the number of entries in params. |__ This routine has been superseded by XtAppErrorMsg. To register a procedure to be called on nonfatal error con- ditions, use XtSetWarningMsgHandler. 400 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetWarningMsgHandler(msg_handler) XtErrorMsgHandler msg_handler; msg_handler Specifies the new nonfatal error procedure, which usually returns. |__ The default warning handler provided by the Intrinsics con- structs a string from the error resource database and calls XtWarning. This routine has been superseded by XtAppSet- WarningMsgHandler. To call the installed high-level warning handler, use XtWarningMsg. __ | void XtWarningMsg(name, type, class, default, params, num_params) String name; String type; String class; String default; String *params; Cardinal *num_params; name Specifies the general kind of error. type Specifies the detailed name of the error. class Specifies the resource class. default Specifies the default message to use if an error database entry is not found. params Specifies a pointer to a list of values to be stored in the message. num_params Specifies the number of entries in params. |__ This routine has been superseded by XtAppWarningMsg. To register a procedure to be called on fatal error condi- tions, use XtSetErrorHandler. 401 X Toolkit Intrinsics X11 Release 6.4 __ | void XtSetErrorHandler(handler) XtErrorHandler handler; handler Specifies the new fatal error procedure, which should not return. |__ The default error handler provided by the Intrinsics is _XtError. On POSIX-based systems, it prints the message to standard error and terminates the application. Fatal error message handlers should not return. If one does, subsequent X Toolkit behavior is undefined. This routine has been superseded by XtAppSetErrorHandler. To call the installed fatal error procedure, use XtError. __ | void XtError(message) String message; message Specifies the message to be reported. |__ Most programs should use XtAppErrorMsg, not XtError, to pro- vide for customization and internationalization of error messages. This routine has been superseded by XtAppError. To register a procedure to be called on nonfatal error con- ditions, use XtSetWarningHandler. __ | void XtSetWarningHandler(handler) XtErrorHandler handler; handler Specifies the new nonfatal error procedure, which usually returns. |__ The default warning handler provided by the Intrinsics is _XtWarning. On POSIX-based systems, it prints the message to standard error and returns to the caller. This routine has been superseded by XtAppSetWarningHandler. To call the installed nonfatal error procedure, use XtWarn- ing. 402 X Toolkit Intrinsics X11 Release 6.4 __ | void XtWarning(message) String message; message Specifies the nonfatal error message to be reported. |__ Most programs should use XtAppWarningMsg, not XtWarning, to provide for customization and internationalization of warn- ing messages. This routine has been superseded by XtApp- Warning. 403 X Toolkit Intrinsics X11 Release 6.4 Appendix D Intrinsics Error Messages All Intrinsics errors and warnings have class ``XtToolkitEr- ror''. The following two tables summarize the common errors and warnings that can be generated by the Intrinsics. Addi- tional implementation-dependent messages are permitted. Error Messages ------------------------------------------------------------------------------------- Name Type Default Message ------------------------------------------------------------------------------------- allocError calloc Cannot perform calloc allocError malloc Cannot perform malloc allocError realloc Cannot perform realloc internalError xtMakeGeometryRequest internal error; ShellClassEx- tension is NULL invalidArgCount xtGetValues Argument count > 0 on NULL argument list in XtGetValues invalidArgCount xtSetValues Argument count > 0 on NULL argument list in XtSetValues invalidClass applicationShellInsertChild ApplicationShell does not accept RectObj children; ignored invalidClass constraintSetValue Subclass of Constraint required in CallCon- straintSetValues invalidClass xtAppCreateShell XtAppCreateShell requires non-NULL widget class invalidClass xtCreatePopupShell XtCreatePopupShell requires non-NULL widget class invalidClass xtCreateWidget XtCreateWidget requires non- NULL widget class invalidClass xtPopdown XtPopdown requires a subclass of shellWidgetClass invalidClass xtPopup XtPopup requires a subclass of shellWidgetClass invalidDimension xtCreateWindow Widget %s has zero width and/or height invalidDimension shellRealize Shell widget %s has zero width and/or height invalidDisplay xtInitialize Can't open display: %s invalidGetValues xtGetValues NULL ArgVal in XtGetValues invalidExtension shellClassPartInitialize widget class %s has invalid ShellClassExtension record 404 X Toolkit Intrinsics X11 Release 6.4 invalidExtension xtMakeGeometryRequest widget class %s has invalid ShellClassExtension record invalidGeometryManager xtMakeGeometryRequest XtMakeGeometryRequest - par- ent has no geometry manager invalidParameter xtAddInput invalid condition passed to XtAddInput invalidParameter xtAddInput invalid condition passed to XtAppAddInput invalidParent xtChangeManagedSet Attempt to manage a child when parent is not Composite invalidParent xtChangeManagedSet Attempt to unmanage a child when parent is not Composite invalidParent xtCreatePopupShell XtCreatePopupShell requires non-NULL parent invalidParent xtCreateWidget XtCreateWidget requires non- NULL parent invalidParent xtMakeGeometryRequest non-shell has no parent in XtMakeGeometryRequest invalidParent xtMakeGeometryRequest XtMakeGeometryRequest - par- ent not composite invalidParent xtManageChildren Attempt to manage a child when parent is not Composite invalidParent xtUnmanageChildren Attempt to unmanage a child when parent is not Composite invalidProcedure inheritanceProc Unresolved inheritance opera- tion invalidProcedure realizeProc No realize class procedure defined invalidWindow eventHandler Event with wrong window missingWidget fetchDisplayArg FetchDisplayArg called with- out a widget to reference nonWidget xtCreateWidget attempt to add non-widget child "%s" to parent "%s" which supports only widgets noPerDisplay closeDisplay Couldn't find per display information noPerDisplay getPerDisplay Couldn't find per display information noSelectionProperties freeSelectionProperty internal error: no selection property context for display noWidgetAncestor windowedAncestor Object "%s" does not have windowed ancestor nullDisplay xtRegisterExtensionSelector XtRegisterExtensionSelector requires a non-NULL display nullProc insertChild "%s" parent has NULL insert_child method r2versionMismatch widget Widget class %s must be re- compiled. R3versionMismatch widget Widget class %s must be re- compiled. R4orR5versionMismatch widget Widget class %s must be re- compiled. 405 X Toolkit Intrinsics X11 Release 6.4 rangeError xtRegisterExtensionSelector Attempt to register multiple selectors for one extension event type sessionManagement SmcOpenConnection Tried to connect to session manager, %s subclassMismatch xtCheckSubclass Widget class %s found when subclass of %s expected: %s ------------------------------------------------------------------------------------- Warning Messages --------------------------------------------------------------------------- Name Type Default Message --------------------------------------------------------------------------- ambiguousParent xtChangeManagedSet Not all children have same parent ambiguousParent xtManageChildren Not all children have same parent in XtManageChildren ambiguousParent xtUnmanageChildren Not all children have same parent in XtUnmanageChildren badFormat xtGetSelectionValue Selection owner returned type INCR property with format != 32 badGeometry shellRealize Shell widget "%s" has an invalid geometry specifica- tion: "%s" badValue cvtStringToPixel Color name "%s" is not defined communicationError select Select failed; error code %s conversionError string Cannot convert string "%s" to type %s conversionError stringToVisual Cannot find Visual of class %s for display %s conversionFailed xtConvertVarToArgList Type conversion failed conversionFailed xtGetTypedArg Type conversion (%s to %s) failed for widget '%s' displayError invalidDisplay Can't find display structure grabError xtAddGrab XtAddGrab requires exclusive grab if spring_loaded is TRUE grabError xtRemoveGrab XtRemoveGrab asked to remove a widget not on the list initializationError xtInitialize Initializing Resource Lists twice insufficientSpace xtGetTypedArg Insufficient space for con- verted type '%s' in widget '%s' internalError shell Shell's window manager inter- action is broken 406 X Toolkit Intrinsics X11 Release 6.4 invalidAddressMode computeArgs Conversion arguments for wid- get '%s' contain an unsup- ported address mode invalidArgCount getResources argument count > 0 on NULL argument list invalidCallbackList xtAddCallback Cannot find callback list in XtAddCallback invalidCallbackList xtAddCallback Cannot find callback list in XtAddCallbacks invalidCallbackList xtCallCallback Cannot find callback list in XtCallCallbacks invalidCallbackList xtRemoveAllCallback Cannot find callback list in XtRemoveAllCallbacks invalidCallbackList xtRemoveCallback Cannot find callback list in XtRemoveCallbacks invalidChild xtChangeManagedSet Null child passed to Unman- ageChildren invalidChild xtManageChildren null child passed to Man- ageChildren invalidChild xtManageChildren null child passed to XtMan- ageChildren invalidChild xtUnmanageChildren Null child passed to XtUnman- ageChildren invalidChild xtUnmanageChildren Null child found in argument list to unmanage invalidDepth setValues Can't change widget depth invalidExtension xtCreateWidget widget "%s" class %s has invalid CompositeClassExten- sion record invalidExtension xtCreateWidget widget class %s has invalid ConstraintClassExtension record invalidGrab ungrabKeyOrButton Attempt to remove nonexistent passive grab invalidGrabKind xtPopup grab kind argument has invalid value; XtGrabNone assumed invalidParameters freeTranslations Freeing XtTranslations requires no extra arguments invalidParameters mergeTranslations MergeTM to TranslationTable needs no extra arguments invalidParameters xtMenuPopdown XtMenuPopdown called with num_params != 0 or 1 invalidParameters xtMenuPopupAction MenuPopup wants exactly one argument invalidParent xtCopyFromParent CopyFromParent must have non- NULL parent invalidPopup xtMenuPopup Can't find popup widget "%s" in XtMenuPopup invalidPopup xtMenuPopdown Can't find popup in widget "%s" in XtMenuPopdown 407 X Toolkit Intrinsics X11 Release 6.4 invalidPopup unsupportedOperation Pop-up menu creation is only supported on ButtonPress, KeyPress or EnterNotify events. invalidPopup unsupportedOperation Pop-up menu creation is only supported on Button, Key or EnterNotify events. invalidProcedure deleteChild null delete_child procedure for class %s in XtDestroy invalidProcedure inputHandler XtRemoveInput: Input handler not found invalidProcedure set_values_almost set_values_almost procedure shouldn't be NULL invalidResourceCount getResources resource count > 0 on NULL resource list invalidResourceName computeArgs Cannot find resource name %s as argument to conversion invalidShell xtTranslateCoords Widget has no shell ancestor invalidSizeOverride xtDependencies Representation size %d must match superclass's to over- ride %s missingCharsetList cvtStringToFontSet Missing charsets in String to FontSet conversion noActionProc xtCallActionProc No action proc named "%s" is registered for widget "%s" noColormap cvtStringToPixel Cannot allocate colormap entry for "%s" noFont cvtStringToFont Unable to load any usable ISO8859-1 font noFont cvtStringToFontSet Unable to load any usable fontset noFont cvtStringToFontStruct Unable to load any usable ISO8859-1 font notInConvertSelection xtGetSelectionRequest XtGetSelectionRequest or XtGetSelectionParameters called for widget "%s" out- side of ConvertSelection proc notRectObj xtChangeManagedSet child "%s", class %s is not a RectObj notRectObj xtManageChildren child "%s", class %s is not a RectObj nullWidget xtConvertVarToArgList XtVaTypedArg conversion needs non-NULL widget handle r3versionMismatch widget Shell Widget class %s binary compiled for R3 translationError nullTable Can't remove accelerators from NULL table translationError nullTable Tried to remove nonexistent accelerators translationError ambiguousActions Overriding earlier transla- tion manager actions. 408 X Toolkit Intrinsics X11 Release 6.4 translationError newActions New actions are:%s translationError nullTable table to (un)merge must not be null translationError nullTable Can't translate event through NULL table translationError oldActions Previous entry was: %s %s translationError unboundActions Actions not found: %s translationError xtTranslateInitialize Initializing Translation man- ager twice. translationParseError missingComma ... possibly due to missing ',' in event sequence. translationParseError nonLatin1 ... probably due to non- Latin1 character in quoted string translationParseError parseError translation table syntax error: %s translationParseError parseString Missing '"'. translationParseError showLine ... found while parsing '%s' typeConversionError noConverter No type converter registered for '%s' to '%s' conversion. unknownType xtConvertVarToArgList Unable to find type of resource for conversion unknownType xtGetTypedArg Unable to find type of resource for conversion versionMismatch widget Widget class %s version mis- match (recompilation needed):\n widget %d vs. intrinsics %d. wrongParameters cvtIntOrPixelToXColor Pixel to color conversion needs screen and colormap arguments wrongParameters cvtIntToBool Integer to Bool conversion needs no extra arguments wrongParameters cvtIntToBoolean Integer to Boolean conversion needs no extra arguments wrongParameters cvtIntToFloat Integer to Float conversion needs no extra arguments wrongParameters cvtIntToFont Integer to Font conversion needs no extra arguments wrongParameters cvtIntToPixel Integer to Pixel conversion needs no extra arguments wrongParameters cvtIntToPixmap Integer to Pixmap conversion needs no extra arguments wrongParameters cvtIntToShort Integer to Short conversion needs no extra arguments wrongParameters cvtIntToUnsignedChar Integer to UnsignedChar con- version needs no extra argu- ments wrongParameters cvtStringToAcceleratorTable String to AcceleratorTable conversion needs no extra arguments wrongParameters cvtStringToAtom String to Atom conversion needs Display argument 409 X Toolkit Intrinsics X11 Release 6.4 wrongParameters cvtStringToBool String to Bool conversion needs no extra arguments wrongParameters cvtStringToBoolean String to Boolean conversion needs no extra arguments wrongParameters cvtStringToCommandArgArray String to CommandArgArray conversion needs no extra arguments wrongParameters cvtStringToCursor String to cursor conversion needs display argument wrongParameters cvtStringToDimension String to Dimension conver- sion needs no extra arguments wrongParameters cvtStringToDirectoryString String to DirectoryString conversion needs no extra arguments wrongParameters cvtStringToDisplay String to Display conversion needs no extra arguments wrongParameters cvtStringToFile String to File conversion needs no extra arguments wrongParameters cvtStringToFloat String to Float conversion needs no extra arguments wrongParameters cvtStringToFont String to font conversion needs display argument wrongParameters cvtStringToFontSet String to FontSet conversion needs display and locale arguments wrongParameters cvtStringToFontStruct String to font conversion needs display argument wrongParameters cvtStringToGravity String to Gravity conversion needs no extra arguments wrongParameters cvtStringToInitialState String to InitialState con- version needs no extra argu- ments wrongParameters cvtStringToInt String to Integer conversion needs no extra arguments wrongParameters cvtStringToPixel String to pixel conversion needs screen and colormap arguments wrongParameters cvtStringToRestartStyle String to RestartStyle con- version needs no extra argu- ments wrongParameters cvtStringToShort String to Integer conversion needs no extra arguments wrongParameters cvtStringToTranslationTable String to TranslationTable conversion needs no extra arguments wrongParameters cvtStringToUnsignedChar String to Integer conversion needs no extra arguments wrongParameters cvtStringToVisual String to Visual conversion needs screen and depth argu- ments 410 X Toolkit Intrinsics X11 Release 6.4 wrongParameters cvtXColorToPixel Color to Pixel conversion needs no extra arguments wrongParameters freeCursor Free Cursor requires display argument wrongParameters freeDirectoryString Free Directory String requires no extra arguments wrongParameters freeFile Free File requires no extra arguments wrongParameters freeFont Free Font needs display argu- ment wrongParameters freeFontSet FreeFontSet needs display and locale arguments wrongParameters freeFontStruct Free FontStruct requires dis- play argument wrongParameters freePixel Freeing a pixel requires screen and colormap arguments ------------------------------------------------------------------------------ 411 X Toolkit Intrinsics X11 Release 6.4 Appendix E Defined Strings The StringDefs.h header file contains definitions for the following resource name, class, and representation type sym- bolic constants. Resource names: ------------------------------------------------------------- Symbol Definition ------------------------------------------------------------- XtNaccelerators "accelerators" XtNallowHoriz "allowHoriz" XtNallowVert "allowVert" XtNancestorSensitive "ancestorSensitive" XtNbackground "background" XtNbackgroundPixmap "backgroundPixmap" XtNbitmap "bitmap" XtNborder "borderColor" XtNborderColor "borderColor" XtNborderPixmap "borderPixmap" XtNborderWidth "borderWidth" XtNcallback "callback" XtNchangeHook "changeHook" XtNchildren "children" XtNcolormap "colormap" XtNconfigureHook "configureHook" XtNcreateHook "createHook" XtNdepth "depth" XtNdestroyCallback "destroyCallback" XtNdestroyHook "destroyHook" XtNeditType "editType" XtNfile "file" XtNfont "font" XtNfontSet "fontSet" XtNforceBars "forceBars" XtNforeground "foreground" XtNfunction "function" XtNgeometryHook "geometryHook" XtNheight "height" XtNhighlight "highlight" XtNhSpace "hSpace" XtNindex "index" XtNinitialResourcesPersistent "initialResourcesPersistent" XtNinnerHeight "innerHeight" XtNinnerWidth "innerWidth" 412 X Toolkit Intrinsics X11 Release 6.4 XtNinnerWindow "innerWindow" XtNinsertPosition "insertPosition" XtNinternalHeight "internalHeight" XtNinternalWidth "internalWidth" XtNjumpProc "jumpProc" XtNjustify "justify" XtNknobHeight "knobHeight" XtNknobIndent "knobIndent" XtNknobPixel "knobPixel" XtNknobWidth "knobWidth" XtNlabel "label" XtNlength "length" XtNlowerRight "lowerRight" XtNmappedWhenManaged "mappedWhenManaged" XtNmenuEntry "menuEntry" XtNname "name" XtNnotify "notify" XtNnumChildren "numChildren" XtNnumShells "numShells" XtNorientation "orientation" XtNparameter "parameter" XtNpixmap "pixmap" XtNpopupCallback "popupCallback" XtNpopdownCallback "popdownCallback" XtNresize "resize" XtNreverseVideo "reverseVideo" XtNscreen "screen" XtNscrollProc "scrollProc" XtNscrollDCursor "scrollDCursor" XtNscrollHCursor "scrollHCursor" XtNscrollLCursor "scrollLCursor" XtNscrollRCursor "scrollRCursor" XtNscrollUCursor "scrollUCursor" XtNscrollVCursor "scrollVCursor" XtNselection "selection" XtNselectionArray "selectionArray" XtNsensitive "sensitive" XtNsession "session" XtNshells "shells" XtNshown "shown" XtNspace "space" XtNstring "string" XtNtextOptions "textOptions" XtNtextSink "textSink" XtNtextSource "textSource" XtNthickness "thickness" XtNthumb "thumb" XtNthumbProc "thumbProc" XtNtop "top" XtNtranslations "translations" XtNunrealizeCallback "unrealizeCallback" XtNupdate "update" XtNuseBottom "useBottom" 413 X Toolkit Intrinsics X11 Release 6.4 XtNuseRight "useRight" XtNvalue "value" XtNvSpace "vSpace" XtNwidth "width" XtNwindow "window" XtNx "x" XtNy "y" ------------------------------------------------------------- Resource classes: ------------------------------------------------------------- Symbol Definition ------------------------------------------------------------- XtCAccelerators "Accelerators" XtCBackground "Background" XtCBitmap "Bitmap" XtCBoolean "Boolean" XtCBorderColor "BorderColor" XtCBorderWidth "BorderWidth" XtCCallback "Callback" XtCColormap "Colormap" XtCColor "Color" XtCCursor "Cursor" XtCDepth "Depth" XtCEditType "EditType" XtCEventBindings "EventBindings" XtCFile "File" XtCFont "Font" XtCFontSet "FontSet" XtCForeground "Foreground" XtCFraction "Fraction" XtCFunction "Function" XtCHeight "Height" XtCHSpace "HSpace" XtCIndex "Index" XtCInitialResourcesPersistent "InitialResourcesPersistent" XtCInsertPosition "InsertPosition" XtCInterval "Interval" XtCJustify "Justify" XtCKnobIndent "KnobIndent" XtCKnobPixel "KnobPixel" XtCLabel "Label" XtCLength "Length" XtCMappedWhenManaged "MappedWhenManaged" XtCMargin "Margin" XtCMenuEntry "MenuEntry" XtCNotify "Notify" XtCOrientation "Orientation" XtCParameter "Parameter" XtCPixmap "Pixmap" XtCPosition "Position" 414 X Toolkit Intrinsics X11 Release 6.4 XtCReadOnly "ReadOnly" XtCResize "Resize" XtCReverseVideo "ReverseVideo" XtCScreen "Screen" XtCScrollProc "ScrollProc" XtCScrollDCursor "ScrollDCursor" XtCScrollHCursor "ScrollHCursor" XtCScrollLCursor "ScrollLCursor" XtCScrollRCursor "ScrollRCursor" XtCScrollUCursor "ScrollUCursor" XtCScrollVCursor "ScrollVCursor" XtCSelection "Selection" XtCSelectionArray "SelectionArray" XtCSensitive "Sensitive" XtCSession "Session" XtCSpace "Space" XtCString "String" XtCTextOptions "TextOptions" XtCTextPosition "TextPosition" XtCTextSink "TextSink" XtCTextSource "TextSource" XtCThickness "Thickness" XtCThumb "Thumb" XtCTranslations "Translations" XtCValue "Value" XtCVSpace "VSpace" XtCWidth "Width" XtCWindow "Window" XtCX "X" XtCY "Y" ------------------------------------------------------------- Resource representation types: ------------------------------------------------- Symbol Definition ------------------------------------------------- XtRAcceleratorTable "AcceleratorTable" XtRAtom "Atom" XtRBitmap "Bitmap" XtRBool "Bool" XtRBoolean "Boolean" XtRCallback "Callback" XtRCallProc "CallProc" XtRCardinal "Cardinal" XtRColor "Color" XtRColormap "Colormap" XtRCommandArgArray "CommandArgArray" XtRCursor "Cursor" XtRDimension "Dimension" XtRDirectoryString "DirectoryString" XtRDisplay "Display" 415 X Toolkit Intrinsics X11 Release 6.4 XtREditMode "EditMode" XtREnum "Enum" XtREnvironmentArray "EnvironmentArray" XtRFile "File" XtRFloat "Float" XtRFont "Font" XtRFontSet "FontSet" XtRFontStruct "FontStruct" XtRFunction "Function" XtRGeometry "Geometry" XtRGravity "Gravity" XtRImmediate "Immediate" XtRInitialState "InitialState" XtRInt "Int" XtRJustify "Justify" XtRLongBoolean XtRBool XtRObject "Object" XtROrientation "Orientation" XtRPixel "Pixel" XtRPixmap "Pixmap" XtRPointer "Pointer" XtRPosition "Position" XtRRestartStyle "RestartStyle" XtRScreen "Screen" XtRShort "Short" XtRSmcConn "SmcConn" XtRString "String" XtRStringArray "StringArray" XtRStringTable "StringTable" XtRUnsignedChar "UnsignedChar" XtRTranslationTable "TranslationTable" XtRVisual "Visual" XtRWidget "Widget" XtRWidgetClass "WidgetClass" XtRWidgetList "WidgetList" XtRWindow "Window" ------------------------------------------------- Boolean enumeration constants: ------------------------------------------------- Symbol Definition ------------------------------------------------- XtEoff "off" XtEfalse "false" XtEno "no" XtEon "on" XtEtrue "true" XtEyes "yes" ------------------------------------------------- 416 X Toolkit Intrinsics X11 Release 6.4 Orientation enumeration constants: ------------------------------------------------- Symbol Definition ------------------------------------------------- XtEvertical "vertical" XtEhorizontal "horizontal" ------------------------------------------------- Text edit enumeration constants: ------------------------------------------------- Symbol Definition ------------------------------------------------- XtEtextRead "read" XtEtextAppend "append" XtEtextEdit "edit" ------------------------------------------------- Color enumeration constants: --------------------------------------------------- Symbol Definition --------------------------------------------------- XtExtdefaultbackground "xtdefaultbackground" XtExtdefaultforeground "xtdefaultforeground" --------------------------------------------------- Font constant: ------------------------------------------------- Symbol Definition ------------------------------------------------- XtExtdefaultfont "xtdefaultfont" ------------------------------------------------- Hooks for External Agents constants: ----------------------------------------------------- Symbol Definition ----------------------------------------------------- XtHcreate "Xtcreate" XtHsetValues "Xtsetvalues" XtHmanageChildren "XtmanageChildren" XtHunmanageChildren "XtunmanageChildren" XtHmanageSet "XtmanageSet" XtHunmanageSet "XtunmanageSet" XtHrealizeWidget "XtrealizeWidget" XtHunrealizeWidget "XtunrealizeWidget" 417 X Toolkit Intrinsics X11 Release 6.4 XtHaddCallback "XtaddCallback" XtHaddCallbacks "XtaddCallbacks" XtHremoveCallback "XtremoveCallback" XtHremoveCallbacks "XtremoveCallbacks" XtHremoveAllCallbacks "XtremoveAllCallbacks" XtHaugmentTranslations "XtaugmentTranslations" XtHoverrideTranslations "XtoverrideTranslations" XtHuninstallTranslations "XtuninstallTranslations" XtHsetKeyboardFocus "XtsetKeyboardFocus" XtHsetWMColormapWindows "XtsetWMColormapWindows" XtHmapWidget "XtmapWidget" XtHunmapWidget "XtunmapWidget" XtHpopup "Xtpopup" XtHpopupSpringLoaded "XtpopupSpringLoaded" XtHpopdown "Xtpopdown" XtHconfigure "Xtconfigure" XtHpreGeometry "XtpreGeometry" XtHpostGeometry "XtpostGeometry" XtHdestroy "Xtdestroy" ----------------------------------------------------- The Shell.h header file contains definitions for the follow- ing resource name, class, and representation type symbolic constants. Resource names: ---------------------------------------------------- Symbol Definition ---------------------------------------------------- XtNallowShellResize "allowShellResize" XtNargc "argc" XtNargv "argv" XtNbaseHeight "baseHeight" XtNbaseWidth "baseWidth" XtNcancelCallback "cancelCallback" XtNclientLeader "clientLeader" XtNcloneCommand "cloneCommand" XtNconnection "connection" XtNcreatePopupChildProc "createPopupChildProc" XtNcurrentDirectory "currentDirectory" XtNdieCallback "dieCallback" XtNdiscardCommand "discardCommand" XtNenvironment "environment" XtNerrorCallback "errorCallback" XtNgeometry "geometry" XtNheightInc "heightInc" XtNiconMask "iconMask" XtNiconName "iconName" XtNiconNameEncoding "iconNameEncoding" XtNiconPixmap "iconPixmap" XtNiconWindow "iconWindow" 418 X Toolkit Intrinsics X11 Release 6.4 XtNiconX "iconX" XtNiconY "iconY" XtNiconic "iconic" XtNinitialState "initialState" XtNinput "input" XtNinteractCallback "interactCallback" XtNjoinSession "joinSession" XtNmaxAspectX "maxAspectX" XtNmaxAspectY "maxAspectY" XtNmaxHeight "maxHeight" XtNmaxWidth "maxWidth" XtNminAspectX "minAspectX" XtNminAspectY "minAspectY" XtNminHeight "minHeight" XtNminWidth "minWidth" XtNoverrideRedirect "overrideRedirect" XtNprogramPath "programPath" XtNresignCommand "resignCommand" XtNrestartCommand "restartCommand" XtNrestartStyle "restartStyle" XtNsaveCallback "saveCallback" XtNsaveCompleteCallback "saveCompleteCallback" XtNsaveUnder "saveUnder" XtNsessionID "sessionID" XtNshutdownCommand "shutdownCommand" XtNtitle "title" XtNtitleEncoding "titleEncoding" XtNtransient "transient" XtNtransientFor "transientFor" XtNurgency "urgency" XtNvisual "visual" XtNwaitForWm "waitforwm" XtNwaitforwm "waitforwm" XtNwidthInc "widthInc" XtNwindowGroup "windowGroup" XtNwindowRole "windowRole" XtNwinGravity "winGravity" XtNwmTimeout "wmTimeout" ---------------------------------------------------- Resource classes: ---------------------------------------------------- Symbol Definition ---------------------------------------------------- XtCAllowShellResize "allowShellResize" XtCArgc "Argc" XtCArgv "Argv" XtCBaseHeight "BaseHeight" XtCBaseWidth "BaseWidth" XtCClientLeader "ClientLeader" XtCCloneCommand "CloneCommand" 419 X Toolkit Intrinsics X11 Release 6.4 XtCConnection "Connection" XtCCreatePopupChildProc "CreatePopupChildProc" XtCCurrentDirectory "CurrentDirectory" XtCDiscardCommand "DiscardCommand" XtCEnvironment "Environment" XtCGeometry "Geometry" XtCHeightInc "HeightInc" XtCIconMask "IconMask" XtCIconName "IconName" XtCIconNameEncoding "IconNameEncoding" XtCIconPixmap "IconPixmap" XtCIconWindow "IconWindow" XtCIconX "IconX" XtCIconY "IconY" XtCIconic "Iconic" XtCInitialState "InitialState" XtCInput "Input" XtCJoinSession "JoinSession" XtCMaxAspectX "MaxAspectX" XtCMaxAspectY "MaxAspectY" XtCMaxHeight "MaxHeight" XtCMaxWidth "MaxWidth" XtCMinAspectX "MinAspectX" XtCMinAspectY "MinAspectY" XtCMinHeight "MinHeight" XtCMinWidth "MinWidth" XtCOverrideRedirect "OverrideRedirect" XtCProgramPath "ProgramPath" XtCResignCommand "ResignCommand" XtCRestartCommand "RestartCommand" XtCRestartStyle "RestartStyle" XtCSaveUnder "SaveUnder" XtCSessionID "SessionID" XtCShutdownCommand "ShutdownCommand" XtCTitle "Title" XtCTitleEncoding "TitleEncoding" XtCTransient "Transient" XtCTransientFor "TransientFor" XtCUrgency "Urgency" XtCVisual "Visual" XtCWaitForWm "Waitforwm" XtCWaitforwm "Waitforwm" XtCWidthInc "WidthInc" XtCWindowGroup "WindowGroup" XtCWindowRole "WindowRole" XtCWinGravity "WinGravity" XtCWmTimeout "WmTimeout" ---------------------------------------------------- Resource representation types: 420 X Toolkit Intrinsics X11 Release 6.4 ------------------------------------------------- Symbol Definition ------------------------------------------------- XtRAtom "Atom" ------------------------------------------------- 421 X Toolkit Intrinsics X11 Release 6.4 Appendix F Resource Configuration Management Setting and changing resources in X applications can be dif- ficult for both the application programmer and the end user. Resource Configuration Management (RCM) addresses this prob- lem by changing the X Intrinsics to immediately modify a resource for a specified widget and each child widget in the hierarchy. In this context, immediate means: no sourcing of a resource file is required; the application does not need to be restarted for the new resource values to take effect; and the change occurs immediately. The main difference between RCM and the Editres protocol is that the RCM customizing hooks reside in the Intrinsics and thus are linked with other toolkits such as Motif and the Athena widgets. However, the EditRes protocol requires the application to link with the EditRes routines in the Xmu library and Xmu is not used by all applications that use Motif. Also, the EditRes protocol uses ClientMessage, whereas the RCM Intrinsics hooks use PropertyNotify events. X Properties and the PropertyNotify events are used to implement RCM and allow on-the-fly resource customization. When the X Toolkit is initialized, two atoms are interned with the strings Custom Init and Custom Data. Both _XtCre- atePopupShell and _XtAppCreateShell register a PropertyNo- tify event handler to handle these properties. A customization tool uses the Custom Init property to ping an application to get the application's toplevel window. When the application's property notify event handler is invoked, the handler deletes the property. No data is transferred in this property. A customization tool uses the Custom Data property to tell an application that it should change a resource's value. The data in the property contains the length of the resource name (the number of bytes in the resource name), the resource name and the new value for the resource. This property's type is XA_STRING and the format of the string is: 1. The length of the resource name (the number of bytes in the resource name) 2. One space character 422 X Toolkit Intrinsics X11 Release 6.4 3. The resource name 4. One space character 5. The resource value When setting the application's resource, the event handler calls functions to walk the application's widget tree, determining which widgets are affected by the resource string, and then applying the value with XtSetValues. As the widget tree is recursively descended, at each level in the widget tree a resource part is tested for a match. When the entire resource string has been matched, the value is applied to the widget or widgets. Before a value is set on a widget, it is first determined if the last part of the resource is a valid resource for that widget. It must also add the resource to the application's resource database and then query it using specific resource strings that is builds from the widget information. 423 424 Table of Contents Acknowledgments . . . . . . . . . . . . . . . . . . . . ix About This Manual . . . . . . . . . . . . . . . . . . . xii Chapter 1 -- Intrinsics and Widgets . . . . . . . . . . 1 1.1. Intrinsics . . . . . . . . . . . . . . . . . . . . 1 1.2. Languages . . . . . . . . . . . . . . . . . . . . . 1 1.3. Procedures and Macros . . . . . . . . . . . . . . . 2 1.4. Widgets . . . . . . . . . . . . . . . . . . . . . . 2 1.4.1. Core Widgets . . . . . . . . . . . . . . . . . . 3 1.4.1.1. CoreClassPart Structure . . . . . . . . . . . . 4 1.4.1.2. CorePart Structure . . . . . . . . . . . . . . 5 1.4.1.3. Core Resources . . . . . . . . . . . . . . . . 7 1.4.1.4. CorePart Default Values . . . . . . . . . . . . 7 1.4.2. Composite Widgets . . . . . . . . . . . . . . . . 8 1.4.2.1. CompositeClassPart Structure . . . . . . . . . 8 1.4.2.2. CompositePart Structure . . . . . . . . . . . . 10 1.4.2.3. Composite Resources . . . . . . . . . . . . . . 11 1.4.2.4. CompositePart Default Values . . . . . . . . . 11 1.4.3. Constraint Widgets . . . . . . . . . . . . . . . 11 1.4.3.1. ConstraintClassPart Structure . . . . . . . . . 12 1.4.3.2. ConstraintPart Structure . . . . . . . . . . . 13 1.4.3.3. Constraint Resources . . . . . . . . . . . . . 14 1.5. Implementation-Specific Types . . . . . . . . . . . 14 1.6. Widget Classing . . . . . . . . . . . . . . . . . . 15 1.6.1. Widget Naming Conventions . . . . . . . . . . . . 16 1.6.2. Widget Subclassing in Public .h Files . . . . . . 18 1.6.3. Widget Subclassing in Private .h Files . . . . . 19 1.6.4. Widget Subclassing in .c Files . . . . . . . . . 21 1.6.5. Widget Class and Superclass Look Up . . . . . . . 24 1.6.6. Widget Subclass Verification . . . . . . . . . . 25 1.6.7. Superclass Chaining . . . . . . . . . . . . . . . 27 1.6.8. Class Initialization: class_initialize and class_part_initialize Procedures . . . . . . . . . . . . 28 1.6.9. Initializing a Widget Class . . . . . . . . . . . 30 1.6.10. Inheritance of Superclass Operations . . . . . . 30 1.6.11. Invocation of Superclass Operations . . . . . . 32 1.6.12. Class Extension Records . . . . . . . . . . . . 33 Chapter 2 -- Widget Instantiation . . . . . . . . . . . 36 2.1. Initializing the X Toolkit . . . . . . . . . . . . 37 2.2. Establishing the Locale . . . . . . . . . . . . . . 43 2.3. Loading the Resource Database . . . . . . . . . . . 45 2.4. Parsing the Command Line . . . . . . . . . . . . . 50 2.5. Creating Widgets . . . . . . . . . . . . . . . . . 53 2.5.1. Creating and Merging Argument Lists . . . . . . . 54 2.5.2. Creating a Widget Instance . . . . . . . . . . . 57 2.5.3. Creating an Application Shell Instance . . . . . 60 2.5.4. Convenience Procedure to Initialize an Appli- cation . . . . . . . . . . . . . . . . . . . . . . . . . 63 2.5.5. Widget Instance Allocation: The allocate Pro- cedure . . . . . . . . . . . . . . . . . . . . . . . . . 66 2.5.6. Widget Instance Initialization: The initial- ize Procedure . . . . . . . . . . . . . . . . . . . . . 69 iii 2.5.7. Constraint Instance Initialization: The Con- straintClassPart initialize Procedure . . . . . . . . . 72 2.5.8. Nonwidget Data Initialization: The initial- ize_hook Procedure . . . . . . . . . . . . . . . . . . . 72 2.6. Realizing Widgets . . . . . . . . . . . . . . . . . 73 2.6.1. Widget Instance Window Creation: The realize Procedure . . . . . . . . . . . . . . . . . . . . . . . 75 2.6.2. Window Creation Convenience Routine . . . . . . . 77 2.7. Obtaining Window Information from a Widget . . . . 78 2.7.1. Unrealizing Widgets . . . . . . . . . . . . . . . 81 2.8. Destroying Widgets . . . . . . . . . . . . . . . . 81 2.8.1. Adding and Removing Destroy Callbacks . . . . . . 83 2.8.2. Dynamic Data Deallocation: The destroy Proce- dure . . . . . . . . . . . . . . . . . . . . . . . . . . 84 2.8.3. Dynamic Constraint Data Deallocation: The ConstraintClassPart destroy Procedure . . . . . . . . . 85 2.8.4. Widget Instance Deallocation: The deallocate Procedure . . . . . . . . . . . . . . . . . . . . . . . 85 2.9. Exiting from an Application . . . . . . . . . . . . 86 Chapter 3 -- Composite Widgets and Their Children . . . 87 3.1. Addition of Children to a Composite Widget: The insert_child Procedure . . . . . . . . . . . . . . . . . 88 3.2. Insertion Order of Children: The insert_posi- tion Procedure . . . . . . . . . . . . . . . . . . . . . 89 3.3. Deletion of Children: The delete_child Proce- dure . . . . . . . . . . . . . . . . . . . . . . . . . . 90 3.4. Adding and Removing Children from the Managed Set . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.4.1. Managing Children . . . . . . . . . . . . . . . . 91 3.4.2. Unmanaging Children . . . . . . . . . . . . . . . 94 3.4.3. Bundling Changes to the Managed Set . . . . . . . 95 3.4.4. Determining if a Widget Is Managed . . . . . . . 98 3.5. Controlling When Widgets Get Mapped . . . . . . . . 99 3.6. Constrained Composite Widgets . . . . . . . . . . . 100 Chapter 4 -- Shell Widgets . . . . . . . . . . . . . . . 103 4.1. Shell Widget Definitions . . . . . . . . . . . . . 103 4.1.1. ShellClassPart Definitions . . . . . . . . . . . 104 4.1.2. ShellPart Definition . . . . . . . . . . . . . . 109 4.1.3. Shell Resources . . . . . . . . . . . . . . . . . 113 4.1.4. ShellPart Default Values . . . . . . . . . . . . 116 4.2. Session Participation . . . . . . . . . . . . . . . 122 4.2.1. Joining a Session . . . . . . . . . . . . . . . . 123 4.2.2. Saving Application State . . . . . . . . . . . . 124 4.2.2.1. Requesting Interaction . . . . . . . . . . . . 126 4.2.2.2. Interacting with the User during a Check- point . . . . . . . . . . . . . . . . . . . . . . . . . 127 4.2.2.3. Responding to a Shutdown Cancellation . . . . . 128 4.2.2.4. Completing a Save . . . . . . . . . . . . . . . 128 4.2.3. Responding to a Shutdown . . . . . . . . . . . . 129 4.2.4. Resigning from a Session . . . . . . . . . . . . 129 Chapter 5 -- Pop-Up Widgets . . . . . . . . . . . . . . 130 5.1. Pop-Up Widget Types . . . . . . . . . . . . . . . . 130 5.2. Creating a Pop-Up Shell . . . . . . . . . . . . . . 131 5.3. Creating Pop-Up Children . . . . . . . . . . . . . 133 iv 5.4. Mapping a Pop-Up Widget . . . . . . . . . . . . . . 134 5.5. Unmapping a Pop-Up Widget . . . . . . . . . . . . . 138 Chapter 6 -- Geometry Management . . . . . . . . . . . . 142 6.1. Initiating Geometry Changes . . . . . . . . . . . . 142 6.2. General Geometry Manager Requests . . . . . . . . . 143 6.3. Resize Requests . . . . . . . . . . . . . . . . . . 146 6.4. Potential Geometry Changes . . . . . . . . . . . . 147 6.5. Child Geometry Management: The geometry_manager Procedure . . . . . . . . . . . . . . . . . . . . . . . 148 6.6. Widget Placement and Sizing . . . . . . . . . . . . 150 6.7. Preferred Geometry . . . . . . . . . . . . . . . . 153 6.8. Size Change Management: The resize Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Chapter 7 -- Event Management . . . . . . . . . . . . . 157 7.1. Adding and Deleting Additional Event Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 7.1.1. Adding and Removing Input Sources . . . . . . . . 158 7.1.2. Adding and Removing Blocking Notifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 7.1.3. Adding and Removing Timeouts . . . . . . . . . . 161 7.1.4. Adding and Removing Signal Callbacks . . . . . . 163 7.2. Constraining Events to a Cascade of Widgets . . . . 165 7.2.1. Requesting Key and Button Grabs . . . . . . . . . 167 7.3. Focusing Events on a Child . . . . . . . . . . . . 173 7.3.1. Events for Drawables That Are Not a Widget's Window . . . . . . . . . . . . . . . . . . . . . . . . . 175 7.4. Querying Event Sources . . . . . . . . . . . . . . 177 7.5. Dispatching Events . . . . . . . . . . . . . . . . 178 7.6. The Application Input Loop . . . . . . . . . . . . 180 7.7. Setting and Checking the Sensitivity State of a Widget . . . . . . . . . . . . . . . . . . . . . . . . . 181 7.8. Adding Background Work Procedures . . . . . . . . . 183 7.9. X Event Filters . . . . . . . . . . . . . . . . . . 184 7.9.1. Pointer Motion Compression . . . . . . . . . . . 185 7.9.2. Enter/Leave Compression . . . . . . . . . . . . . 185 7.9.3. Exposure Compression . . . . . . . . . . . . . . 185 7.10. Widget Exposure and Visibility . . . . . . . . . . 187 7.10.1. Redisplay of a Widget: The expose Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 7.10.2. Widget Visibility . . . . . . . . . . . . . . . 189 7.11. X Event Handlers . . . . . . . . . . . . . . . . . 189 7.11.1. Event Handlers That Select Events . . . . . . . 190 7.11.2. Event Handlers That Do Not Select Events . . . . 193 7.11.3. Current Event Mask . . . . . . . . . . . . . . . 196 7.11.4. Event Handlers for X11 Protocol Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 7.12. Using the Intrinsics in a Multi-Threaded Envi- ronment . . . . . . . . . . . . . . . . . . . . . . . . 204 7.12.1. Initializing a Multi-Threaded Intrinsics Application . . . . . . . . . . . . . . . . . . . . . . 204 7.12.2. Locking X Toolkit Data Structures . . . . . . . 204 7.12.2.1. Locking the Application Context . . . . . . . 206 7.12.2.2. Locking the Process . . . . . . . . . . . . . 206 7.12.3. Event Management in a Multi-Threaded Envi- v ronment . . . . . . . . . . . . . . . . . . . . . . . . 207 Chapter 8 -- Callbacks . . . . . . . . . . . . . . . . . 209 8.1. Using Callback Procedure and Callback List Def- initions . . . . . . . . . . . . . . . . . . . . . . . . 209 8.2. Identifying Callback Lists . . . . . . . . . . . . 210 8.3. Adding Callback Procedures . . . . . . . . . . . . 211 8.4. Removing Callback Procedures . . . . . . . . . . . 212 8.5. Executing Callback Procedures . . . . . . . . . . . 213 8.6. Checking the Status of a Callback List . . . . . . 215 Chapter 9 -- Resource Management . . . . . . . . . . . . 216 9.1. Resource Lists . . . . . . . . . . . . . . . . . . 216 9.2. Byte Offset Calculations . . . . . . . . . . . . . 222 9.3. Superclass-to-Subclass Chaining of Resource Lists . . . . . . . . . . . . . . . . . . . . . . . . . 223 9.4. Subresources . . . . . . . . . . . . . . . . . . . 224 9.5. Obtaining Application Resources . . . . . . . . . . 226 9.6. Resource Conversions . . . . . . . . . . . . . . . 228 9.6.1. Predefined Resource Converters . . . . . . . . . 229 9.6.2. New Resource Converters . . . . . . . . . . . . . 232 9.6.3. Issuing Conversion Warnings . . . . . . . . . . . 237 9.6.4. Registering a New Resource Converter . . . . . . 238 9.6.5. Resource Converter Invocation . . . . . . . . . . 244 9.7. Reading and Writing Widget State . . . . . . . . . 249 9.7.1. Obtaining Widget State . . . . . . . . . . . . . 249 9.7.1.1. Widget Subpart Resource Data: The get_val- ues_hook Procedure . . . . . . . . . . . . . . . . . . . 252 9.7.1.2. Widget Subpart State . . . . . . . . . . . . . 252 9.7.2. Setting Widget State . . . . . . . . . . . . . . 254 9.7.2.1. Widget State: The set_values Procedure . . . . 256 9.7.2.2. Widget State: The set_values_almost Proce- dure . . . . . . . . . . . . . . . . . . . . . . . . . . 259 9.7.2.3. Widget State: The ConstraintClassPart set_values Procedure . . . . . . . . . . . . . . . . . . 260 9.7.2.4. Widget Subpart State . . . . . . . . . . . . . 260 9.7.2.5. Widget Subpart Resource Data: The set_val- ues_hook Procedure . . . . . . . . . . . . . . . . . . . 262 Chapter 10 -- Translation Management . . . . . . . . . . 264 10.1. Action Tables . . . . . . . . . . . . . . . . . . 264 10.1.1. Action Table Registration . . . . . . . . . . . 266 10.1.2. Action Names to Procedure Translations . . . . . 267 10.1.3. Action Hook Registration . . . . . . . . . . . . 267 10.2. Translation Tables . . . . . . . . . . . . . . . . 269 10.2.1. Event Sequences . . . . . . . . . . . . . . . . 270 10.2.2. Action Sequences . . . . . . . . . . . . . . . . 271 10.2.3. Multi-Click Time . . . . . . . . . . . . . . . . 271 10.3. Translation Table Management . . . . . . . . . . . 272 10.4. Using Accelerators . . . . . . . . . . . . . . . . 275 10.5. KeyCode-to-KeySym Conversions . . . . . . . . . . 278 10.6. Obtaining a KeySym in an Action Procedure . . . . 283 10.7. KeySym-to-KeyCode Conversions . . . . . . . . . . 284 10.8. Registering Button and Key Grabs for Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285 10.9. Invoking Actions Directly . . . . . . . . . . . . 287 10.10. Obtaining a Widget's Action List . . . . . . . . 288 vi Chapter 11 -- Utility Functions . . . . . . . . . . . . 289 11.1. Determining the Number of Elements in an Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 11.2. Translating Strings to Widget Instances . . . . . 290 11.3. Managing Memory Usage . . . . . . . . . . . . . . 291 11.4. Sharing Graphics Contexts . . . . . . . . . . . . 294 11.5. Managing Selections . . . . . . . . . . . . . . . 297 11.5.1. Setting and Getting the Selection Timeout Value . . . . . . . . . . . . . . . . . . . . . . . . . 297 11.5.2. Using Atomic Transfers . . . . . . . . . . . . . 298 11.5.2.1. Atomic Transfer Procedures . . . . . . . . . . 298 11.5.2.2. Getting the Selection Value . . . . . . . . . 302 11.5.2.3. Setting the Selection Owner . . . . . . . . . 304 11.5.3. Using Incremental Transfers . . . . . . . . . . 306 11.5.3.1. Incremental Transfer Procedures . . . . . . . 307 11.5.3.2. Getting the Selection Value Incrementally . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311 11.5.3.3. Setting the Selection Owner for Incremen- tal Transfers . . . . . . . . . . . . . . . . . . . . . 314 11.5.4. Setting and Retrieving Selection Target Parameters . . . . . . . . . . . . . . . . . . . . . . . 316 11.5.5. Generating MULTIPLE Requests . . . . . . . . . . 319 11.5.6. Auxiliary Selection Properties . . . . . . . . . 320 11.5.7. Retrieving the Most Recent Timestamp . . . . . . 321 11.5.8. Retrieving the Most Recent Event . . . . . . . . 322 11.6. Merging Exposure Events into a Region . . . . . . 322 11.7. Translating Widget Coordinates . . . . . . . . . . 323 11.8. Translating a Window to a Widget . . . . . . . . . 324 11.9. Handling Errors . . . . . . . . . . . . . . . . . 324 11.10. Setting WM_COLORMAP_WINDOWS . . . . . . . . . . . 332 11.11. Finding File Names . . . . . . . . . . . . . . . 333 11.12. Hooks for External Agents . . . . . . . . . . . . 338 11.12.1. Hook Object Resources . . . . . . . . . . . . . 339 11.12.2. Querying Open Displays . . . . . . . . . . . . 346 Chapter 12 -- Nonwidget Objects . . . . . . . . . . . . 347 12.1. Data Structures . . . . . . . . . . . . . . . . . 347 12.2. Object Objects . . . . . . . . . . . . . . . . . . 347 12.2.1. ObjectClassPart Structure . . . . . . . . . . . 347 12.2.2. ObjectPart Structure . . . . . . . . . . . . . . 350 12.2.3. Object Resources . . . . . . . . . . . . . . . . 351 12.2.4. ObjectPart Default Values . . . . . . . . . . . 351 12.2.5. Object Arguments to Intrinsics Routines . . . . 351 12.2.6. Use of Objects . . . . . . . . . . . . . . . . . 352 12.3. Rectangle Objects . . . . . . . . . . . . . . . . 353 12.3.1. RectObjClassPart Structure . . . . . . . . . . . 353 12.3.2. RectObjPart Structure . . . . . . . . . . . . . 355 12.3.3. RectObj Resources . . . . . . . . . . . . . . . 356 12.3.4. RectObjPart Default Values . . . . . . . . . . . 356 12.3.5. Widget Arguments to Intrinsics Routines . . . . 356 12.3.6. Use of Rectangle Objects . . . . . . . . . . . . 357 12.4. Undeclared Class . . . . . . . . . . . . . . . . . 359 12.5. Widget Arguments to Intrinsics Routines . . . . . 359 Chapter 13 -- Evolution of the Intrinsics . . . . . . . 362 13.1. Determining Specification Revision Level . . . . . 362 vii 13.2. Release 3 to Release 4 Compatibility . . . . . . . 363 13.2.1. Additional Arguments . . . . . . . . . . . . . . 363 13.2.2. set_values_almost Procedures . . . . . . . . . . 363 13.2.3. Query Geometry . . . . . . . . . . . . . . . . . 363 13.2.4. unrealizeCallback Callback List . . . . . . . . 364 13.2.5. Subclasses of WMShell . . . . . . . . . . . . . 364 13.2.6. Resource Type Converters . . . . . . . . . . . . 364 13.2.7. KeySym Case Conversion Procedure . . . . . . . . 365 13.2.8. Nonwidget Objects . . . . . . . . . . . . . . . 365 13.3. Release 4 to Release 5 Compatibility . . . . . . . 365 13.3.1. baseTranslations Resource . . . . . . . . . . . 366 13.3.2. Resource File Search Path . . . . . . . . . . . 366 13.3.3. Customization Resource . . . . . . . . . . . . . 366 13.3.4. Per-Screen Resource Database . . . . . . . . . . 367 13.3.5. Internationalization of Applications . . . . . . 367 13.3.6. Permanently Allocated Strings . . . . . . . . . 368 13.3.7. Arguments to Existing Functions . . . . . . . . 368 13.4. Release 5 to Release 6 Compatibility . . . . . . . 368 13.4.1. Widget Internals . . . . . . . . . . . . . . . . 369 13.4.2. General Application Development . . . . . . . . 369 13.4.3. Communication with Window and Session Man- agers . . . . . . . . . . . . . . . . . . . . . . . . . 370 13.4.4. Geometry Management . . . . . . . . . . . . . . 370 13.4.5. Event Management . . . . . . . . . . . . . . . . 371 13.4.6. Resource Management . . . . . . . . . . . . . . 371 13.4.7. Translation Management . . . . . . . . . . . . . 372 13.4.8. Selections . . . . . . . . . . . . . . . . . . . 372 13.4.9. External Agent Hooks . . . . . . . . . . . . . . 372 Appendix A -- Resource File Format . . . . . . . . . . . 373 Appendix B -- Translation Table Syntax . . . . . . . . . 375 Appendix C -- Compatibility Functions . . . . . . . . . 385 Appendix D -- Intrinsics Error Messages . . . . . . . . 404 Appendix E -- Defined Strings . . . . . . . . . . . . . 412 Appendix F -- Resource Configuration Management . . . . 422 Index . . . . . . . . . . . . . . . . . . . . . . . . . 425 viii