.\" $Xorg: CH02,v 1.3 2000/08/17 19:42:42 cpqbld Exp $ .\" Copyright \(co 1985, 1986, 1987, 1988, 1991, 1994 .\" X Consortium .\" .\" Permission is hereby granted, free of charge, to any person obtaining .\" a copy of this software and associated documentation 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 PURPOSE AND NONINFRINGEMENT. .\" IN NO EVENT SHALL THE X CONSORTIUM 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 Consortium 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 \(co 1985, 1986, 1987, 1988, 1991, 1994 .\" Digital Equipment Corporation, Maynard, Massachusetts. .\" .\" Permission to use, copy, modify and distribute this documentation 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 .\" permission 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. .\" \& .sp 1 .ce 3 \s+1\fBChapter 2\fP\s-1 \s+1\fBWidget Instantiation\fP\s-1 .sp 2 .nr H1 2 .nr H2 0 .nr H3 0 .nr H4 0 .nr H5 0 .LP .XS Chapter 2 \(em Widget Instantiation .XE A hierarchy of widget instances constitutes a widget tree. The shell widget returned by .PN 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. .LP Widgets can be either composite or primitive. Both kinds of widgets can contain children, but the \*(xI provide a set of management mechanisms for constructing and interfacing between composite widgets, their children, and other clients. .LP Composite widgets, that is, members of the class .PN compositeWidgetClass , 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 management methods. .LP In addition, the \*(xI recursively perform many operations (for example, realization and destruction) on composite widgets and all their children. Primitive widgets that have children must be prepared to perform the recursive operations themselves on behalf of their children. .LP A widget tree is manipulated by several \*(xI functions. For example, .PN XtRealizeWidget traverses the tree downward and recursively realizes all pop-up widgets and children of composite widgets. .PN XtDestroyWidget traverses the tree downward and destroys all pop-up widgets and children 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. .PN XtMakeGeometryRequest traverses the tree up one level and calls the geometry manager that is responsible for a widget child's geometry. .LP To facilitate upward traversal of the widget tree, each widget has a pointer to its parent widget. The Shell widget that .PN XtAppCreateShell returns has a \fIparent\fP pointer of NULL. .LP To facilitate downward traversal of the widget tree, the \fIchildren\fP 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. .NH 2 Initializing the \*(tk .XS \fB\*(SN Initializing the \*(tk\fP .XE .LP Before an application can call any \*(xI function other than .PN XtSetLanguageProc and .PN XtToolkitThreadInitialize , it must initialize the \*(xI by using .IP \(bu 5 .PN XtToolkitInitialize , which initializes the \*(xI internals .IP \(bu 5 .PN XtCreateApplicationContext , which initializes the per-application state .IP \(bu 5 .PN XtDisplayInitialize or .PN XtOpenDisplay , which initializes the per-display state .IP \(bu 5 .PN XtAppCreateShell , which creates the root of a widget tree .LP Or an application can call the convenience procedure .PN XtOpenApplication , which combines the functions of the preceding procedures. An application wishing to use the ANSI C locale mechanism should call .PN XtSetLanguageProc prior to calling .PN XtDisplayInitialize , .PN XtOpenDisplay , .PN XtOpenApplication , or .PN XtAppInitialize . .LP Multiple instances of \*(tk applications may be implemented 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. .IN "application context" "" "@DEF@" To accommodate both requirements, the \*(xI 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 .PN Display pointers for that application. The \*(xI handle all display connections within a single application context simultaneously, handling input in a round-robin fashion. The application context type .PN XtAppContext .IN "XtAppContext" "" "@DEF@" is opaque to clients. .sp .LP To initialize the \*(xI internals, use .PN XtToolkitInitialize . .LP .IN "XtToolkitInitialize" "" "@DEF@" .sM .FD 0 void XtToolkitInitialize() .FN .LP .eM If .PN XtToolkitInitialize was previously called, it returns immediately. When .PN XtToolkitThreadInitialize is called before .PN XtToolkitInitialize , the latter is protected against simultaneous activation by multiple threads. .sp .LP To create an application context, use .PN XtCreateApplicationContext . .LP .IN "XtCreateApplicationContext" "" "@DEF@" .sM .FD 0 XtAppContext XtCreateApplicationContext() .FN .LP .eM The .PN XtCreateApplicationContext function returns an application context, which is an opaque type. Every application must have at least one application context. .sp .LP To destroy an application context and close any remaining display connections in it, use .PN XtDestroyApplicationContext . .LP .IN "XtDestroyApplicationContext" "" "@DEF@" .sM .FD 0 void XtDestroyApplicationContext(\fIapp_context\fP) .br XtAppContext \fIapp_context\fP; .FN .IP \fIapp_context\fP 1i Specifies the application context. .LP .eM The .PN XtDestroyApplicationContext function destroys the specified application context. If called from within an event dispatch (for example, in a callback procedure), .PN XtDestroyApplicationContext does not destroy the application context until the dispatch is complete. .sp .LP To get the application context in which a given widget was created, use .PN XtWidgetToApplicationContext . .LP .IN "XtWidgetToApplicationContext" "" "@DEF@" .sM .FD 0 XtAppContext XtWidgetToApplicationContext(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget for which you want the application context. \*(oI .LP .eM The .PN XtWidgetToApplicationContext function returns the application context for the specified widget. .sp .LP To initialize a display and add it to an application context, use .PN XtDisplayInitialize . .LP .IN "XtDisplayInitialize" "" "@DEF@" .sM .FD 0 void XtDisplayInitialize(\fIapp_context\fP, \fIdisplay\fP, \ \fIapplication_name\fP, \fIapplication_class\fP, .br \fIoptions\fP, \fInum_options\fP, \fIargc\fP, \fIargv\fP) .br XtAppContext \fIapp_context\fP; .br Display *\fIdisplay\fP; .br String \fIapplication_name\fP; .br String \fIapplication_class\fP; .br XrmOptionDescRec *\fIoptions\fP; .br Cardinal \fInum_options\fP; .br int *\fIargc\fP; .br String *\fIargv\fP; .FN .IP \fIapp_context\fP 1.4i Specifies the application context. .IP \fIdisplay\fP 1.4i Specifies a previously opened display connection. Note that a single display connection can be in at most one application context. .IP \fIapplication_name\fP 1.4i Specifies the name of the application instance. .IP \fIapplication_class\fP 1.4i Specifies the class name of this application, which is usually the generic name for all instances of this application. .IP \fIoptions\fP 1.4i Specifies how to parse the command line for any application-specific resources. The \fIoptions\fP argument is passed as a parameter to .PN XrmParseCommand . For further information, see Section 15.9 in \fI\*(xL\fP and Section 2.4 of this specification. .IP \fInum_options\fP 1.4i Specifies the number of entries in the options list. .IP \fIargc\fP 1.4i Specifies a pointer to the number of command line parameters. .IP \fIargv\fP 1.4i Specifies the list of command line parameters. .LP .eM The .PN 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 language string, builds the resource database for the default screen, calls the Xlib .PN XrmParseCommand function to parse the command line, and performs other per-display initialization. After .PN XrmParseCommand has been called, \fIargc\fP and \fIargv\fP contain only those parameters that were not in the standard option table or in the table specified by the \fIoptions\fP argument. If the modified \fIargc\fP is not zero, most applications simply print out the modified \fIargv\fP along with a message listing the allowable options. On POSIX-based systems, the application name is usually the final component of \fIargv\fP[0]. If the synchronous resource is .PN True , .PN XtDisplayInitialize calls the Xlib .PN 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 \fIapplication_name\fP, \fIapplication_class\fP, \fIoptions\fP, and \fInum_options\fP arguments. .LP .PN XtDisplayInitialize calls .PN XrmSetDatabase to associate the resource database of the default screen with the display before returning. .KS .LP To open a display, initialize it, and then add it to an application context, use .PN XtOpenDisplay . .LP .IN "XtOpenDisplay" "" "@DEF@" .sM .FD 0 Display *XtOpenDisplay(\fIapp_context\fP, \fIdisplay_string\fP, \ \fIapplication_name\fP, \fIapplication_class\fP, .br \fIoptions\fP, \fInum_options\fP, \fIargc\fP, \fIargv\fP) .br XtAppContext \fIapp_context\fP; .br String \fIdisplay_string\fP; .br String \fIapplication_name\fP; .br String \fIapplication_class\fP; .br XrmOptionDescRec *\fIoptions\fP; .br Cardinal \fInum_options\fP; .br int *\fIargc\fP; .br String *\fIargv\fP; .FN .IP \fIapp_context\fP 1.4i Specifies the application context. .IP \fIdisplay_string\fP 1.4i Specifies the display string, or NULL. .IP \fIapplication_name\fP 1.4i Specifies the name of the application instance, or NULL. .IP \fIapplication_class\fP 1.4i Specifies the class name of this application, which is usually the generic name for all instances of this application. .IP \fIoptions\fP 1.4i Specifies how to parse the command line for any application-specific resources. The options argument is passed as a parameter to .PN XrmParseCommand . .IP \fInum_options\fP 1.4i Specifies the number of entries in the options list. .IP \fIargc\fP 1.4i Specifies a pointer to the number of command line parameters. .IP \fIargv\fP 1.4i Specifies the list of command line parameters. .KE .LP .eM The .PN XtOpenDisplay function calls .PN XOpenDisplay with the specified \fIdisplay_string\fP. If \fIdisplay_string\fP is NULL, .PN XtOpenDisplay uses the current value of the \-display option specified in \fIargv\fP. If no display is specified in \fIargv\fP, the user's default display is retrieved from the environment. On POSIX-based systems, this is the value of the .PN \s-1DISPLAY\s+1 environment variable. .LP If this succeeds, .PN XtOpenDisplay then calls .PN XtDisplayInitialize and passes it the opened display and the value of the \-name option specified in \fIargv\fP as the application name. If no \-name option is specified and \fIapplication_name\fP is non-NULL, \fIapplication_name\fP is passed to .PN XtDisplayInitialize . If \fIapplication_name\fP is NULL and if the environment variable .PN \s-1RESOURCE_NAME\s+1 is set, the value of .PN \s-1RESOURCE_NAME\s+1 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 \fIargv\fP[0] less any directory and file type components, that is, the final component of \fIargv\fP[0], if specified. If \fIargv\fP[0] does not exist or is the empty string, the application name is ``main''. .PN XtOpenDisplay returns the newly opened display or NULL if it failed. .LP See Section 7.12 for information regarding the use of .PN XtOpenDisplay in multiple threads. .sp .LP To close a display and remove it from an application context, use .PN XtCloseDisplay . .LP .IN "XtCloseDisplay" "" "@DEF@" .sM .FD 0 void XtCloseDisplay(\fIdisplay\fP) .br Display *\fIdisplay\fP; .FN .IP \fIdisplay\fP 1i Specifies the display. .LP .eM The .PN XtCloseDisplay function calls .PN XCloseDisplay with the specified \fIdisplay\fP as soon as it is safe to do so. If called from within an event dispatch (for example, a callback procedure), .PN XtCloseDisplay does not close the display until the dispatch is complete. Note that applications need only call .PN XtCloseDisplay if they are to continue executing after closing the display; otherwise, they should call .PN XtDestroyApplicationContext . .LP See Section 7.12 for information regarding the use of .PN XtCloseDisplay in multiple threads. .NH 2 Establishing the Locale .XS \fB\*(SN Establishing the Locale\fP .XE .LP Resource databases are specified to be created in the current process locale. During display initialization prior to creating the per-screen resource database, the \*(xI 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. .LP The callout procedure provided by the application is of type .PN XtLanguageProc . .LP .IN "XtLanguageProc" "" "@DEF@" .sM .FD 0 typedef String (*XtLanguageProc)(Display*, String, XtPointer); .br Display *\fIdisplay\fP; .br String \fIlanguage\fP; .br XtPointer \fIclient_data\fP; .FN .IP \fIdisplay\fP 1i Passes the display. .IP \fIlanguage\fP Passes the initial language value obtained from the command line or server per-display resource specifications. .IP \fIclient_data\fP Passes the additional client data specified in the call to .PN XtSetLanguageProc . .LP .eM The language procedure allows an application to set the locale to the value of the language resource determined by .PN XtDisplayInitialize . The function returns a new language string that will be subsequently used by .PN XtDisplayInitialize to establish the path for loading resource files. The returned string will be copied by the \*(xI into new memory. .LP Initially, no language procedure is set by the \*(xI. To set the language procedure for use by .PN XtDisplayInitialize , use .PN XtSetLanguageProc . .LP .IN XtSetLanguageProc "" "@DEF@" .IN "language procedure" "" "@DEF@" .sM .FD 0 XtLanguageProc XtSetLanguageProc(\fIapp_context\fP, \fIproc\fP, \fIclient_data\fP) .br XtAppContext \fIapp_context\fP; .br XtLanguageProc \fIproc\fP; .br XtPointer \fIclient_data\fP; .FN .IP \fIapp_context\fP 1i Specifies the application context in which the language procedure is to be used, or NULL. .IP \fIproc\fP 1i Specifies the language procedure. .IP \fIclient_data\fP 1i Specifies additional client data to be passed to the language procedure when it is called. .LP .eM .PN XtSetLanguageProc sets the language procedure that will be called from .PN XtDisplayInitialize for all subsequent Displays initialized in the specified application context. If \fIapp_context\fP is NULL, the specified language procedure is registered in all application contexts created by the calling process, including any future application contexts that may be created. If \fIproc\fP is NULL, a default language procedure is registered. .PN XtSetLanguageProc returns the previously registered language procedure. If a language procedure has not yet been registered, the return value is unspecified, but if this return value is used in a subsequent call to .PN XtSetLanguageProc , it will cause the default language procedure to be registered. .LP The default language procedure does the following: .IP \(bu 5 Sets the locale according to the environment. On ANSI C-based systems this is done by calling .PN setlocale ( .PN LC_ALL , \fIlanguage\fP ). If an error is encountered, a warning message is issued with .PN XtWarning . .IP \(bu 5 Calls .PN XSupportsLocale to verify that the current locale is supported. If the locale is not supported, a warning message is issued with .PN XtWarning and the locale is set to ``C''. .IP \(bu 5 Calls .PN XSetLocaleModifiers specifying the empty string. .IP \(bu 5 Returns the value of the current locale. On ANSI C-based systems this is the return value from a final call to .PN setlocale ( .PN LC_ALL , NULL ). .LP A client wishing to use this mechanism to establish locale can do so by calling .PN XtSetLanguageProc prior to .PN XtDisplayInitialize , as in the following example. .LP .Ds 0 .TA .5i Widget top; XtSetLanguageProc(NULL, NULL, NULL); top = XtOpenApplication(...); ... .De .NH 2 Loading the Resource Database .XS \fB\*(SN Loading the Resource Database\fP .XE .LP The .PN XtDisplayInitialize function first determines the language 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 precedence: .IP \(bu 5 Application command line (\fIargc\fP, \fIargv\fP). .IP \(bu 5 Per-host user environment resource file on the local host. .IP \(bu 5 Per-screen resource specifications from the server. .IP \(bu 5 Per-display resource specifications from the server or from .br the user preference file on the local host. .IP \(bu 5 Application-specific user resource file on the local host. .IP \(bu 5 Application-specific class resource file on the local host. .LP When the resource database for a particular screen on the display is needed (either internally, or when .PN XtScreenDatabase is called), it is created in the following manner using the sources listed above in the same order: .IP \(bu 5 A temporary database, the ``server resource database'', is created from the string returned by .PN XResourceManagerString or, if .PN 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/\fB.Xdefaults\fP. .IN ".Xdefaults" "" "@DEF@" .IP \(bu 5 If a language procedure has been set, .PN XtDisplayInitialize 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 Character Set. If neither option is specified on the command line, .PN XtDisplayInitialize queries the server resource database (which is assumed to be entirely in XPCS) for the resource \fIname\fP\fB.xnlLanguage\fP, class \fIClass\fP\fB.XnlLanguage\fP where \fIname\fP .IN "xnlLanguage" "" "@DEF@" .IN "Resources" "xnlLanguage" and \fIClass\fP are the \fIapplication_name\fP and \fIapplication_class\fP specified to .PN 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 \*(xI that require the per-display language string. .IP \(bu 5 The screen resource database is initialized by parsing the command line in the manner specified by Section 2.4. .IP \(bu 5 If a language procedure has not been set, the initial database is then queried for the resource \fIname\fP\fB.xnlLanguage\fP, class \fIClass\fP\fB.XnlLanguage\fP 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 systems, this is done by retrieving the value of the .PN \s-1LANG\s+1 environment variable. If no language string is found, the empty string is used. This language string is saved for all future references in the \*(xI that require the per-display language string. .IP \(bu 5 After determining the language string, the user's environment 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 environment resource file name is specified by the value of the .PN \s-1XENVIRONMENT\s+1 environment variable. If this environment variable does not exist, the user's home directory is searched for a file named .PN \&.Xdefaults-\fIhost\fP , where \fIhost\fP is the host name of the machine on which the application is running. .IP \(bu 5 The per-screen resource specifications are then merged into the screen resource database, if they exist. These specifications are the string returned by .PN XScreenResourceString for the respective screen and are owned entirely by the user. .IP \(bu 5 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. .IP \(bu 5 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 .PN XrmSetDatabase with the current screen resource database, after preserving the original display-associated database, then calling .PN XtResolvePathname with the parameters (\fIdisplay\fP, NULL, NULL, NULL, \fIpath\fP, NULL, 0, NULL), where \fIpath\fP is defined in an operating-system-specific way. On POSIX-based systems, \fIpath\fP is defined to be the value of the environment variable .PN \s-1XUSERFILESEARCHPATH\s+1 if this is defined. If .PN \s-1XUSERFILESEARCHPATH\s+1 is not defined, an implementation-dependent default value is used. This default value is constrained in the following manner: .RS .IP \- 3 If the environment variable .PN \s-1XAPPLRESDIR\s+1 is not defined, the default .PN \s-1XUSERFILESEARCHPATH\s+1 must contain at least six entries. These entries must contain .IN "XUSERFILESEARCHPATH" "" "@DEF@" .IN "XAPPLRESDIR" "" "@DEF@" .IN "$HOME" $HOME as the directory prefix, plus the following substitutions: .nf .ta .3i 1.5i 2i 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 .fi 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. .IP \- 3 If .PN \s-1XAPPLRESDIR\s+1 is defined, the default .PN \s-1XUSERFILESEARCHPATH\s+1 must contain at least seven entries. These entries must contain the following directory prefixes and substitutions: .ne 1.1 .nf .ta .3i 1.6i 2.2i 3.3i 3.7i 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 .fi The order of these seven entries within the path must be as given above. The order and use of substitutions within a given entry are implementation-dependent. .RE .IP \(bu 5 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 application is installed. It may contain sitewide customizations specified by the system manager. The name of the application class resource file is found by calling .PN XtResolvePathname with the parameters (\fIdisplay\fP, ``app-defaults'', NULL, NULL, NULL, NULL, 0, NULL). This file is expected to be provided by the developer of the application and may be required for the application 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 .PN XtAppSetFallbackResources . Note that the customization substitution string is retrieved dynamically by .PN XtResolvePathname 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 .PN XtResolvePathname , the original display-associated database is restored. .sp .LP To obtain the resource database for a particular screen, use .PN XtScreenDatabase . .LP .IN "XtScreenDatabase" "" "@DEF@" .sM .FD 0 XrmDatabase XtScreenDatabase(\fIscreen\fP) .br Screen *\fIscreen\fP; .FN .IP \fIscreen\fP 1i Specifies the screen whose resource database is to be returned. .LP .eM The .PN XtScreenDatabase function returns the fully merged resource database as specified above, associated with the specified screen. If the specified \fIscreen\fP does not belong to a .PN Display initialized by .PN XtDisplayInitialize , the results are undefined. .sp .LP To obtain the default resource database associated with a particular display, use .PN XtDatabase . .LP .IN "XtDatabase" "" "@DEF@" .sM .FD 0 XrmDatabase XtDatabase(\fIdisplay\fP) .br Display *\fIdisplay\fP; .FN .IP \fIdisplay\fP 1i Specifies the display. .LP .eM The .PN XtDatabase function is equivalent to .PN XrmGetDatabase . It returns the database associated with the specified display, or NULL if a database has not been set. .sp .LP 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 .PN XtAppSetFallbackResources . .LP .IN "XtAppSetFallbackResources" "" "@DEF@" .sM .FD 0 void XtAppSetFallbackResources(\fIapp_context\fP, \fIspecification_list\fP) .br XtAppContext \fIapp_context\fP; .br String *\fIspecification_list\fP; .FN .IP \fIapp_context\fP 1.25i Specifies the application context in which the fallback specifications will be used. .IP \fIspecification_list\fP 1.25i Specifies a NULL-terminated list of resource specifications to preload the database, or NULL. .LP .eM Each entry in \fIspecification_list\fP points to a string in the format of .PN XrmPutLineResource . Following a call to .PN XtAppSetFallbackResources , when a resource database is being created for a particular screen and the \*(xI are not able to find or read an application-specific class resource file according to the rules given above and if \fIspecification_list\fP is not NULL, the resource specifications in \fIspecification_list\fP will be merged into the screen resource database in place of the application-specific class resource file. .PN XtAppSetFallbackResources is not required to copy \fIspecification_list\fP; 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 .PN XtAppSetFallbackResources is called again. The value NULL for \fIspecification_list\fP removes any previous fallback resource specification 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 problem exists in finding and loading the application defaults file. .NH 2 Parsing the Command Line .XS \fB\*(SN Parsing the Command Line\fP .XE .LP The .PN XtOpenDisplay function first parses the command line for the following options: .IP \-display 1i Specifies the display name for .PN XOpenDisplay . .IP \-name 1i Sets the resource name prefix, which overrides the application name passed to .PN XtOpenDisplay . .IP \-xnllanguage 1i Specifies the initial language string for establishing locale and for finding application class resource files. .LP .PN XtDisplayInitialize has a table of standard command line options that are passed to .PN XrmParseCommand for adding resources to the resource database, and it takes as a parameter additional application-specific resource abbreviations. .IN "XrmOptionDescRec" "" "@DEF@" The format of this table is described in Section 15.9 in \fI\*(xL\fP. .LP .sM .Ds 0 .TA .5i 2.75i .ta .5i 2.75i 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; .De .LP .eM The standard table contains the following entries: .TS H l l l l . _ .sp 6p .TH Option String Resource Name Argument Kind Resource Value .sp 6p _ .sp 6p \-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 \-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 .sp 6p _ .TE .LP Note that any unique abbreviation for an option name in the standard table or in the application table is accepted. .LP If reverseVideo is .PN True , the values of .PN XtDefaultForeground and .PN XtDefaultBackground are exchanged for all screens on the Display. .LP .IN "synchronous" "" "@DEF@" .IN "Resources" "synchronous" 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, .PN XtDisplayInitialize makes a call to .PN XSynchronize for all display connections currently open in the application context. Therefore, when multiple displays are initialized in the same application context, the most recent value specified for the synchronous resource is used for all displays in the application context. .LP .IN "selectionTimeout" "" "@DEF@" .IN "Resources" "selectionTimeout" The value of the selectionTimeout resource applies to all displays opened in the same application context. When multiple displays are initialized in the same application context, the most recent value specified is used for all displays in the application context. .LP 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 .PN xmh , you can start it up as .LP .Ds xmh \-xrm 'xmh*Command.background: red' .DE .LP When it parses the command line, .PN XtDisplayInitialize merges the application option table with the standard option table before calling the Xlib .PN 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 an option name is a prefix of another option name, both names are kept in the merged table. The \*(xI reserve all option names beginning with the characters ``-xt'' for future standard uses. .NH 2 Creating Widgets .XS \fB\*(SN Creating Widgets\fP .XE .LP The creation of widget instances is a three-phase process: .IP 1. 5 The widgets are allocated and initialized with resources and are optionally added to the managed subset of their parent. .IP 2. 5 All composite widgets are notified of their managed children in a bottom-up traversal of the widget tree. .IP 3. 5 The widgets create X windows, which then are mapped. .LP .EQ delim $$ .EN To start the first phase, the application calls .PN XtCreateWidget for all its widgets and adds some (usually, most or all) of its widgets to their respective parents' managed set by calling .PN XtManageChild . To avoid an $O( n sup 2 )$ creation process where each composite widget lays itself out each time a widget is created and managed, parent widgets are not notified of changes in their managed set during this phase. .EQ delim off .EN .LP After all widgets have been created, the application calls .PN XtRealizeWidget with the top-level widget to execute the second and third phases. .PN XtRealizeWidget first recursively traverses the widget tree in a postorder (bottom-up) traversal and then notifies each composite widget with one or more managed children by means of its change_managed procedure. .LP 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 example, 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 directions through the widget tree. The parent may force some of its children to change size and position and may issue geometry requests to its own parent in order to better accommodate all its children. You cannot predict where anything will go on the screen until this process finishes. .LP 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. .LP Finally, .PN XtRealizeWidget starts the third phase by making a preorder (top-down) traversal of the widget tree, allocates an X window to each widget by means of its realize procedure, and finally maps the widgets that are managed. .NH 3 Creating and Merging Argument Lists .XS \fB\*(SN Creating and Merging Argument Lists\fP .XE .LP Many \*(xI functions may be passed pairs of resource names and values. These are passed as an arglist, a pointer to an array of .PN Arg structures, which contains .IN "ArgList" "" "@DEF@" .IN "Arg" "" "@DEF@" .LP .sM .Ds 0 .TA .5i 3i .ta .5i 3i typedef struct { String name; XtArgVal value; } Arg, *ArgList; .De .LP .eM where .PN XtArgVal is as defined in Section 1.5. .LP If the size of the resource is less than or equal to the size of an .PN XtArgVal , the resource value is stored directly in \fIvalue\fP; otherwise, a pointer to it is stored in \fIvalue\fP. .LP To set values in an .PN ArgList , use .PN XtSetArg . .LP .IN "XtSetArg" "" "@DEF@" .sM .FD 0 void XtSetArg(\fIarg\fP, \fIname\fP, \fIvalue\fP) .br Arg \fIarg\fP; .br String \fIname\fP; .br XtArgVal \fIvalue\fP; .FN .IP \fIarg\fP 1i Specifies the \fIname/value\fP pair to set. .IP \fIname\fP 1i Specifies the name of the resource. .IP \fIvalue\fP 1i Specifies the value of the resource if it will fit in an .PN XtArgVal , else the address. .LP .eM The .PN XtSetArg function is usually used in a highly stylized manner to minimize the probability of making a mistake; for example: .LP .Ds .TA .5i 3i .ta .5i 3i Arg args[20]; int n; n = 0; XtSetArg(args[n], XtNheight, 100); n++; XtSetArg(args[n], XtNwidth, 200); n++; XtSetValues(widget, args, n); .De .LP Alternatively, an application can statically declare the argument list and use .PN XtNumber : .LP .Ds .TA .5i 3i .ta .5i 3i static Args args[] = { {XtNheight, (XtArgVal) 100}, {XtNwidth, (XtArgVal) 200}, }; XtSetValues(Widget, args, XtNumber(args)); .De .LP Note that you should not use expressions with side effects such as auto-increment or auto-decrement within the first argument to .PN XtSetArg . .PN XtSetArg can be implemented as a macro that evaluates the first argument twice. .sp .LP To merge two arglist arrays, use .PN XtMergeArgLists . .LP .IN "XtMergeArgLists" "" "@DEF@" .sM .FD 0 ArgList XtMergeArgLists(\fIargs1\fP, \fInum_args1\fP, \fIargs2\fP, \ \fInum_args2\fP) .br ArgList \fIargs1\fP; .br Cardinal \fInum_args1\fP; .br ArgList \fIargs2\fP; .br Cardinal \fInum_args2\fP; .FN .IP \fIargs1\fP 1i Specifies the first argument list. .IP \fInum_args1\fP 1i Specifies the number of entries in the first argument list. .IP \fIargs2\fP 1i Specifies the second argument list. .IP \fInum_args2\fP 1i Specifies the number of entries in the second argument list. .LP .eM The .PN 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 .PN XtFree . .sp .LP .IN "varargs" "" "@DEF@" All \*(xI interfaces that require .PN 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 of the corresponding .PN ArgList procedure; e.g., .PN XtVaCreateWidget . Each procedure named \fBXtVa\fP\fIsomething\fP takes as its last arguments, in place of the corresponding .PN ArgList / .PN Cardinal parameters, a variable parameter list of resource name and value pairs where each name is of type .PN String and each value is of type .PN XtArgVal . The end of the list is identified by a \fIname\fP 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 .PN ArgList and varargs forms interchangeably. .LP Two special names are defined for use only in varargs lists: .PN XtVaTypedArg and .PN XtVaNestedList . .sp .LP .IN "XtVaTypedArg" "" "@DEF@" .sM .Ds 0 #define XtVaTypedArg "XtVaTypedArg" .De .LP .eM If the name .PN XtVaTypedArg is specified in place of a resource name, then the following four arguments are interpreted as a \fIname/type/value/size\fP tuple \fIwhere\fP name is of type .PN String , \fItype\fP is of type .PN String , \fIvalue\fP is of type .PN XtArgVal , and \fIsize\fP is of type int. When a varargs list containing .PN XtVaTypedArg is processed, a resource type conversion (see Section 9.6) is performed if necessary to convert the value into the format required by the associated resource. If \fItype\fP is XtRString, then \fIvalue\fP contains a pointer to the string and \fIsize\fP contains the number of bytes allocated, including the trailing null byte. If \fItype\fP is not XtRString, then \fIif\fP size is less than or equal to \fBsizeof\fP(\fBXtArgVal\fP), the value should be the data cast to the type .PN XtArgVal , otherwise \fIvalue\fP 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. .sp .LP .IN "XtVaNestedList" "" "@DEF@" .sM .Ds 0 #define XtVaNestedList "XtVaNestedList" .De .LP .eM If the name .PN XtVaNestedList is specified in place of a resource name, then the following argument is interpreted as an .PN 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 identified with a name entry containing NULL. Varargs lists may nest to any depth. .sp .LP To dynamically allocate a varargs list for use with .PN XtVaNestedList in multiple calls, use .PN XtVaCreateArgsList . .IN "XtVaCreateArgsList" "" "@DEF@" .sp .LP .sM .Ds 0 typedef XtPointer XtVarArgsList; .De .LP .FD 0 XtVarArgsList XtVaCreateArgsList(\fIunused\fP, ...) .br XtPointer \fIunused\fP; .FN .IP \fIunused\fP 1i This argument is not currently used and must be specified as NULL. .IP ... 1i Specifies a variable parameter list of resource name and value pairs. .LP .eM The .PN XtVaCreateArgsList function allocates memory and copies its arguments into a single list pointer, which may be used with .PN XtVaNestedList . The end of both lists is identified by a \fIname\fP entry containing NULL. Any entries of type .PN XtVaTypedArg 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 .PN XtFree when no longer needed. .LP Use of resource files and of the resource database is generally encouraged over lengthy arglist or varargs lists whenever possible in order to permit modification without recompilation. .NH 3 Creating a Widget Instance .XS \fB\*(SN Creating a Widget Instance\fP .XE .LP To create an instance of a widget, use .PN XtCreateWidget . .LP .IN "XtCreateWidget" "" "@DEF@" .sM .FD 0 Widget XtCreateWidget(\fIname\fP, \fIobject_class\fP, \fIparent\fP, \ \fIargs\fP, \fInum_args\fP) .br String \fIname\fP; .br WidgetClass \fIobject_class\fP; .br Widget \fIparent\fP; .br ArgList \fIargs\fP; .br Cardinal \fInum_args\fP; .FN .IP \fIname\fP 1i Specifies the resource instance name for the created 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. .IP \fIobject_class\fP 1i Specifies the widget class pointer for the created object. \*(oC .IP \fIparent\fP 1i Specifies the parent widget. \*(oI .IP \fIargs\fP 1i Specifies the argument list to override any other resource specifications. .IP \fInum_args\fP 1i Specifies the number of entries in the argument list. .LP .eM The .PN XtCreateWidget function performs all the boilerplate operations of widget creation, doing the following in order: .IP \(bu 5 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. .IP \(bu 5 If the specified class is not .PN coreWidgetClass or a subclass thereof, and the parent's class is a subclass of .PN compositeWidgetClass and either no extension record in the parent's composite class part extension field exists with the \fIrecord_type\fP .PN \s-1NULLQUARK\s+1 or the \fIaccepts_objects\fP field in the extension record is .PN False , .PN XtCreateWidget issues a fatal error; see Section 3.1 and Chapter 12. .IP \(bu 5 If the specified class contains an extension record in the object class part \fIextension\fP field with \fIrecord_type\fP .PN \s-1NULLQUARK\s+1 and the \fIallocate\fP field is not NULL, the procedure is invoked to allocate memory for the widget instance. If the parent is a member of the class .PN constraintWidgetClass , the procedure also allocates memory for the parent's constraints and stores the address of this memory into the \fIconstraints\fP field. If no allocate procedure is found, the \*(xI allocate memory for the widget and, when applicable, the constraints, and initializes the \fIconstraints\fP field. .IP \(bu 5 Initializes the Core nonresource data fields \fIself\fP, \fIparent\fP, \fIwidget_class\fP, \fIbeing_destroyed\fP, \fIname\fP, \fImanaged\fP, \fIwindow\fP, \fIvisible\fP, \fIpopup_list\fP, and \fInum_popups\fP. .IP \(bu 5 Initializes the resource fields (for example, \fIbackground_pixel\fP) by using the .PN CoreClassPart resource lists specified for this class and all superclasses. .IP \(bu 5 If the parent is a member of the class .PN constraintWidgetClass , initializes the resource fields of the constraints record by using the .PN ConstraintClassPart resource lists specified for the parent's class and all superclasses up to .PN constraintWidgetClass . .IP \(bu 5 Calls the initialize procedures for the widget starting at the Object initialize procedure on down to the widget's initialize procedure. .IP \(bu 5 If the parent is a member of the class .PN constraintWidgetClass , calls the .PN ConstraintClassPart initialize procedures, starting at .PN constraintWidgetClass on down to the parent's .PN ConstraintClassPart initialize procedure. .IP \(bu 5 If the parent is a member of the class .PN compositeWidgetClass , puts the widget into its parent's children list by calling its parent's insert_child procedure. For further information, see Section 3.1. .sp .LP To create an instance of a widget using varargs lists, use .PN XtVaCreateWidget . .LP .IN "XtVaCreateWidget" "" "@DEF@" .sM .FD 0 Widget XtVaCreateWidget(\fIname\fP, \fIobject_class\fP, \fIparent\fP, ...) .br String \fIname\fP; .br WidgetClass \fIobject_class\fP; .br Widget \fIparent\fP; .FN .IP \fIname\fP 1i Specifies the resource name for the created widget. .IP \fIobject_class\fP 1i Specifies the widget class pointer for the created object. \*(oC .IP \fIparent\fP 1i Specifies the parent widget. \*(oI .IP ... 1i Specifies the variable argument list to override any other resource specifications. .LP .eM The .PN XtVaCreateWidget procedure is identical in function to .PN XtCreateWidget with the \fIargs\fP and \fInum_args\fP parameters replaced by a varargs list, as described in Section 2.5.1. .NH 3 Creating an Application Shell Instance .XS \fB\*(SN Creating an Application Shell Instance\fP .XE .LP 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 .PN XtAppCreateShell to create independent widget trees. .LP .IN "XtAppCreateShell" "" "@DEF@" .sM .FD 0 Widget XtAppCreateShell(\fIname\fP, \ \fIapplication_class\fP, \fIwidget_class\fP, \fIdisplay\fP, \ \fIargs\fP, \fInum_args\fP) .br String \fIname\fP; .br String \fIapplication_class\fP; .br WidgetClass \fIwidget_class\fP; .br Display *\fIdisplay\fP; .br ArgList \fIargs\fP; .br Cardinal \fInum_args\fP; .FN .IP \fIname\fP 1.25i Specifies the instance name of the shell widget. If \fIname\fP is NULL, the application name passed to .PN XtDisplayInitialize is used. .IP \fIapplication_class\fP 1.25i Specifies the resource class string to be used in place of the widget \fIclass_name\fP string when \fIwidget_class\fP is .PN applicationShellWidgetClass or a subclass thereof. .IP \fIwidget_class\fP 1.25i Specifies the widget class for the top-level widget (e.g., .PN applicationShellWidgetClass ). .IP \fIdisplay\fP 1.25i Specifies the display for the default screen and for the resource database used to retrieve the shell widget resources. .IP \fIargs\fP 1.25i Specifies the argument list to override any other resource specifications. .IP \fInum_args\fP 1.25i Specifies the number of entries in the argument list. .LP .eM The .PN 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 \fIargs\fP 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 \fIname\fP.screen, class \fIClass\fP.Screen where \fIClass\fP is the specified \fIapplication_class\fP if \fIwidget_class\fP is .PN applicationShellWidgetClass or a subclass thereof. If \fIwidget_class\fP is not .PN application\%Shell\%Widget\%Class or a subclass, \fIClass\fP is the \fIclass_name\fP field from the .PN CoreClassPart of the specified \fIwidget_class\fP. 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 \fIargs\fP. The widget name and \fIClass\fP as determined above are used as the leftmost (i.e., root) components in all fully qualified resource names for objects within this widget tree. .LP If the specified widget class is a subclass of WMShell, the name and \fIClass\fP as determined above will be stored into the .PN \s-1WM_CLASS\s+1 property on the widget's window when it becomes realized. If the specified \fIwidget_class\fP is .PN applicationShellWidgetClass or a subclass thereof, the .PN \s-1WM_COMMAND\s+1 property will also be set from the values of the XtNargv and XtNargc resources. .LP To create multiple top-level shells within a single (logical) application, you can use one of two methods: .IP \(bu 5 Designate one shell as the real top-level shell and create the others as pop-up children of it by using .PN XtCreatePopupShell . .IP \(bu 5 Have all shells as pop-up children of an unrealized top-level shell. .LP The first method, which is best used when there is a clear choice for what is the main window, leads to resource specifications like the following: .LP .Ds .TA 2i .ta 2i xmail.geometry:... (the main window) xmail.read.geometry:... (the read window) xmail.compose.geometry:... (the compose window) .De .LP The second method, which is best if there is no main window, leads to resource specifications like the following: .LP .Ds .TA 2i .ta 2i xmail.headers.geometry:... (the headers window) xmail.read.geometry:... (the read window) xmail.compose.geometry:... (the compose window) .De .sp .LP To create a top-level widget that is the root of a widget tree using varargs lists, use .PN XtVaAppCreateShell . .LP .IN "XtVaAppCreateShell" "" "@DEF@" .sM .FD 0 Widget XtVaAppCreateShell(\fIname\fP, \fIapplication_class\fP, \ \fIwidget_class\fP, \fIdisplay\fP, ...) .br String \fIname\fP; .br String \fIapplication_class\fP; .br WidgetClass \fIwidget_class\fP; .br Display *\fIdisplay\fP; .FN .IP \fIname\fP 1.5i Specifies the instance name of the shell widget. If \fIname\fP is NULL, the application name passed to .PN XtDisplayInitialize is used. .IP \fIapplication_class\fP 1.5i Specifies the resource class string to be used in place of the widget \fIclass_name\fP string when \fIwidget_class\fP is .PN applicationShellWidgetClass or a subclass thereof. .IP \fIwidget_class\fP 1.5i Specifies the widget class for the top-level widget. .IP \fIdisplay\fP 1.5i Specifies the display for the default screen and for the resource database used to retrieve the shell widget resources. .IP ... 1.5i Specifies the variable argument list to override any other resource specifications. .LP .eM The .PN XtVaAppCreateShell procedure is identical in function to .PN XtAppCreateShell with the \fIargs\fP and \fInum_args\fP parameters replaced by a varargs list, as described in Section 2.5.1. .NH 3 Convenience Procedure to Initialize an Application .XS \fB\*(SN Convenience Procedure to Initialize an Application\fP .XE .LP To initialize the \*(xI internals, create an application context, open and initialize a display, and create the initial root shell instance, an application may use .PN XtOpenApplication or .PN XtVaOpenApplication . .LP .IN "XtOpenApplication" "" "@DEF@" .sM .FD 0 Widget XtOpenApplication(\fIapp_context_return\fP, \fIapplication_class\fP, \ \fIoptions\fP, \fInum_options\fP, .br \fIargc_in_out\fP, \fIargv_in_out\fP, \ \fIfallback_resources\fP, \fIwidget_class\fP, \fIargs\fP, \fInum_args\fP) .br XtAppContext *\fIapp_context_return\fP; .br String \fIapplication_class\fP; .br XrmOptionDescList \fIoptions\fP; .br Cardinal \fInum_options\fP; .br int *\fIargc_in_out\fP; .br String *\fIargv_in_out\fP; .br String *\fIfallback_resources\fP; .br WidgetClass \fIwidget_class\fP; .br ArgList \fIargs\fP; .br Cardinal \fInum_args\fP; .FN .IP \fIapp_context_return\fP 1.5i Returns the application context, if non-NULL. .IP \fIapplication_class\fP 1.5i Specifies the class name of the application. .IP \fIoptions\fP 1.5i Specifies the command line options table. .IP \fInum_options\fP 1.5i Specifies the number of entries in \fIoptions\fP. .IP \fIargc_in_out\fP 1.5i Specifies a pointer to the number of command line arguments. .IP \fIargv_in_out\fP 1.5i Specifies a pointer to the command line arguments. .IP \fIfallback_resources\fP 1.5i Specifies resource values to be used if the application class resource file cannot be opened or read, or NULL. .IP \fIwidget_class\fP 1.5i Specifies the class of the widget to be created. Must be shellWidgetClass or a subclass. .br .IP \fIargs\fP 1.5i Specifies the argument list to override any other resource specifications for the created shell widget. .IP \fInum_args\fP 1.5i Specifies the number of entries in the argument list. .LP .eM The .PN XtOpenApplication function calls .PN XtToolkitInitialize followed by .PN XtCreateApplicationContext , then calls .PN XtOpenDisplay with \fIdisplay_string\fP NULL and \fIapplication_name\fP NULL, and finally calls .PN XtAppCreateShell with \fIname\fP NULL, the specified \fIwidget_class\fP, an argument list and count, and returns the created shell. The recommended \fIwidget_class\fP is .PN sessionShellWidgetClass . The argument list and count are created by merging the specified \fIargs\fP and \fInum_args\fP with a list containing the specified \fIargc\fP and \fIargv\fP. The modified \fIargc\fP and \fIargv\fP returned by .PN XtDisplayInitialize are returned in \fIargc_in_out\fP and \fIargv_in_out\fP. If \fIapp_context_return\fP 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 .PN XtOpenApplication terminates the application. If \fIfallback_resources\fP is non-NULL, .PN XtAppSetFallbackResources is called with the value prior to calling .PN XtOpenDisplay . .sp .LP .IN "XtVaOpenApplication" "" "@DEF@" .sM .FD 0 Widget XtVaOpenApplication(\fIapp_context_return\fP, \fIapplication_class\fP, \ \fIoptions\fP, \fInum_options\fP, .br \fIargc_in_out\fP, \fIargv_in_out\fP, \ \fIfallback_resources\fP, \fIwidget_class\fP, ...) .br XtAppContext *\fIapp_context_return\fP; .br String \fIapplication_class\fP; .br XrmOptionDescList \fIoptions\fP; .br Cardinal \fInum_options\fP; .br int *\fIargc_in_out\fP; .br String *\fIargv_in_out\fP; .br String *\fIfallback_resources\fP; .br WidgetClass \fIwidget_class\fP; .FN .IP \fIapp_context_return\fP 1.5i Returns the application context, if non-NULL. .IP \fIapplication_class\fP 1.5i Specifies the class name of the application. .IP \fIoptions\fP 1.5i Specifies the command line options table. .IP \fInum_options\fP 1.5i Specifies the number of entries in \fIoptions\fP. .IP \fIargc_in_out\fP 1.5i Specifies a pointer to the number of command line arguments. .IP \fIargv_in_out\fP 1.5i Specifies the command line arguments array. .IP \fIfallback_resources\fP 1.5i Specifies resource values to be used if the application class resource file cannot be opened, or NULL. .IP \fIwidget_class\fP 1.5i Specifies the class of the widget to be created. Must be shellWidgetClass or a subclass. .IP ... 1.5i Specifies the variable argument list to override any other resource specifications for the created shell. .LP .eM The .PN XtVaOpenApplication procedure is identical in function to .PN XtOpenApplication with the \fIargs\fP and \fInum_args\fP parameters replaced by a varargs list, as described in Section 2.5.1. .NH 3 Widget Instance Allocation: The allocate Procedure .XS \*(SN Widget Instance Allocation: The allocate Procedure .XE .IN "Widget Allocation" .LP A widget class may optionally provide an instance allocation procedure in the .PN ObjectClassExtension record. .LP When the call to create a widget includes a varargs list containing .PN XtVaTypedArg , these arguments will be passed to the allocation procedure in an .PN XtTypedArgList . .LP .IN "XtTypedArgList" "" "@DEF@" .sM .Ds 0 .TA .5i 3i .ta .5i 3i typedef struct { String name; String type; XtArgVal value; int size; } XtTypedArg, *XtTypedArgList; .De .LP .eM .IN "allocate procedure" "" "@DEF@" The allocate procedure pointer in the .PN ObjectClassExtension record is of type .PN XtAllocateProc . .LP .IN "XtAllocateProc" "" "@DEF@" .sM .FD 0 typedef void (*XtAllocateProc)(WidgetClass, Cardinal*, Cardinal*, ArgList, \ Cardinal*, XtTypedArgList, Cardinal*, \ Widget*, XtPointer*); .br WidgetClass \fIwidget_class\fP; .br Cardinal* \fIconstraint_size\fP; .br Cardinal* \fImore_bytes\fP; .br ArgList \fIargs\fP; .br Cardinal* \fInum_args\fP; .br XtTypedArgList \fItyped_args\fP, .br Cardinal* \fInum_typed_args\fP; .br Widget* \fInew_return\fP; .br XtPointer* \fImore_bytes_return\fP; .FN .IP \fIwidget_class\fP 1.5i Specifies the widget class of the instance to allocate. .IP \fIconstraint_size\fP 1.5i Specifies the size of the constraint record to allocate, or 0. .IP \fImore_bytes\fP 1.5i Specifies the number of auxiliary bytes of memory to allocate. .IP \fIargs\fP 1.5i Specifies the argument list as given in the call to create the widget. .IP \fInum_args\fP 1.5i Specifies the number of arguments. .IP \fItyped_args\fP 1.5i Specifies the list of typed arguments given in the call to create the widget. .IP \fInum_typed_args\fP 1.5i Specifies the number of typed arguments. .IP \fInew_return\fP 1.5i Returns a pointer to the newly allocated instance, or NULL in case of error. .IP \fImore_bytes_return\fP 1.5i Returns the auxiliary memory if it was requested, or NULL if requested and an error occurred; otherwise, unchanged. .LP .eM At widget allocation time, if an extension record with \fIrecord_type\fP equal to .PN \s-1NULLQUARK\s+1 is located through the object class part \fIextension\fP field and the \fIallocate\fP field is not NULL, the .PN XtAllocateProc will be invoked to allocate memory for the widget. If no ObjectClassPart extension record is declared with \fIrecord_type equal\fP to .PN \s-1NULLQUARK\s+1 , then .PN XtInheritAllocate and .PN XtInheritDeallocate are assumed. If no .PN XtAllocateProc is found, the \*(xI will allocate memory for the widget. .LP An .PN XtAllocateProc must perform the following: .IP \(bu 5 Allocate memory for the widget instance and return it in \fInew_return\fP. The memory must be at least \fIwc->core_class.widget_size\fP bytes in length, double-word aligned. .IP \(bu 5 Initialize the \fIcore.constraints\fP field in the instance record to NULL or to point to a constraint record. If \fIconstraint_size\fP is not 0, the procedure must allocate memory for the constraint record. The memory must be double-word aligned. .IP \(bu 5 If \fImore_bytes\fP is not 0, then the address of a block of memory at least \fImore_bytes\fP in size, double-word aligned, must be returned in the \fImore_bytes_return\fP parameter, or NULL to indicate an error. .LP A class allocation procedure that envelops the allocation procedure of a superclass must rely on the enveloped procedure 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. .NH 3 Widget Instance Initialization: The initialize Procedure .XS \*(SN Widget Instance Initialization: The initialize Procedure .XE .IN "Initialization" .IN "Chaining" .IN "Superclass Chaining" .IN "Inheritance" .LP The initialize procedure pointer in a widget class is of type .PN XtInitProc . .LP .IN "XtInitProc" "" "@DEF@" .IN "initialize procedure" "" "@DEF@" .sM .FD 0 typedef void (*XtInitProc)(Widget, Widget, ArgList, Cardinal*); .br Widget \fIrequest\fP; .br Widget \fInew\fP; .br ArgList \fIargs\fP; .br Cardinal *\fInum_args\fP; .FN .IP \fIrequest\fP 1i Specifies a copy of the widget with resource values as requested by the argument list, the resource database, and the widget defaults. .IP \fInew\fP 1i Specifies the widget with the new values, both resource and nonresource, that are actually allowed. .IP \fIargs\fP 1i 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 .PN XtVaTypedArg are converted to the widget representation and the list is transformed into the .PN ArgList format. .IP \fInum_args\fP 1i Specifies the number of entries in the argument list. .LP .eM An initialization procedure performs the following: .IP \(bu 5 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 .PN 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. .NT It is not necessary to allocate space for or to copy callback lists. .NE .IP \(bu 5 Computes values for unspecified resource fields. For example, if \fIwidth\fP and \fIheight\fP are zero, the widget should compute an appropriate width and height based on its other resources. .NT A widget may directly assign only its own \fIwidth\fP and \fIheight\fP within the initialize, initialize_hook, set_values, and set_values_hook procedures; see Chapter 6. .NE .IP \(bu 5 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. .LP 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. .LP Initialization procedures are called in superclass-to-subclass order after all fields specified in the resource lists have been initialized. The initialize procedure does not need to examine \fIargs\fP and \fInum_args\fP if all public resources are declared in the resource list. Most of the initialization code for a specific widget class deals with fields defined in that class and not with fields defined in its superclasses. .LP If a subclass does not need an initialization procedure because it does not need to perform any of the above operations, it can specify NULL for the \fIinitialize\fP field in the class record. .LP 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. .LP As an example, a subclass can visually surround its superclass display. In this case, the width and height calculated 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 calculated by the superclass or was specified explicitly. All widgets must place themselves into whatever size is explicitly given, but they should compute a reasonable size if no size is requested. .LP The \fIrequest\fP and \fInew\fP arguments provide the necessary information for a subclass to determine the difference between an explicitly specified field and a field computed by a superclass. The \fIrequest\fP widget is a copy of the widget as initialized by the arglist and resource database. The \fInew\fP 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. .LP In the above example, the subclass with the visual surround can see if the \fIwidth\fP and \fIheight\fP in the \fIrequest\fP widget are zero. If so, it adds its surround size to the \fIwidth\fP and \fIheight\fP fields in the \fInew\fP widget. If not, it must make do with the size originally specified. .LP The \fInew\fP widget will become the actual widget instance record. Therefore, the initialization procedure should do all its work on the \fInew\fP widget; the \fIrequest\fP widget should never be modified. If the initialize procedure needs to call any routines that operate on a widget, it should specify \fInew\fP as the widget instance. .NH 3 Constraint Instance Initialization: The ConstraintClassPart initialize Procedure .XS \*(SN Constraint Instance Initialization: The ConstraintClassPart initialize Procedure .XE .IN "Initialization" .IN "XtInitProc" .IN "initialize procedure" .IN "Chaining" .IN "Superclass Chaining" .IN "Inheritance" .LP The constraint initialization procedure pointer, found in the .PN ConstraintClassPart \fIinitialize\fP field of the widget class record, is of type .PN XtInitProc . The values passed to the parent constraint initialization procedures are the same as those passed to the child's class widget initialization procedures. .LP The \fIconstraints\fP field of the \fIrequest\fP widget points to a copy of the constraints record as initialized by the arglist and resource database. .LP The constraint initialization procedure should compute any constraint fields derived from constraint resources. It can make further changes to the \fInew\fP widget to make the widget and any other constraint fields conform to the specified constraints, for example, changing the widget's size or position. .LP If a constraint class does not need a constraint initialization procedure, it can specify NULL for the \fIinitialize\fP field of the .PN ConstraintClassPart in the class record. .NH 3 Nonwidget Data Initialization: The initialize_hook Procedure .XS \*(SN Nonwidget Data Initialization: The initialize_hook Procedure .XE .IN "Initialization" .LP .NT The initialize_hook procedure is obsolete, as the same information is now available to the initialize procedure. The procedure has been retained for those widgets that used it in previous releases. .NE .LP The initialize_hook procedure pointer is of type .PN XtArgsProc : .LP .IN "initialize_hook procedure" "" "@DEF@" .IN "XtArgsProc" "" "@DEF@" .sM .FD 0 typedef void (*XtArgsProc)(Widget, ArgList, Cardinal*); .br Widget \fIw\fP; .br ArgList \fIargs\fP; .br Cardinal *\fInum_args\fP; .FN .IP \fIw\fP 1i Specifies the widget. .IP \fIargs\fP 1i Specifies the argument list passed by the client. If the client created the widget using a varargs form, any resources specified via .PN XtVaTypedArg are converted to the widget representation and the list is transformed into the .PN ArgList format. .IP \fInum_args\fP 1i Specifies the number of entries in the argument list. .LP .eM If this procedure is not NULL, it is called immediately after the corresponding initialize procedure or in its place if the \fIinitialize\fP field is NULL. .LP The initialize_hook procedure allows a widget instance to initialize nonresource data using information from the specified argument list as if it were a resource. .NH 2 Realizing Widgets .XS \fB\*(SN Realizing Widgets\fP .XE .LP To realize a widget instance, use .PN XtRealizeWidget . .LP .IN "XtRealizeWidget" "" "@DEF@" .sM .FD 0 void XtRealizeWidget(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(cI .eM .LP If the widget is already realized, .PN XtRealizeWidget simply returns. Otherwise it performs the following: .IP \(bu 5 Binds all action names in the widget's translation table to procedures (see Section 10.1.2). .IP \(bu 5 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. .IP \(bu 5 Constructs an .PN 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. .IP \(bu 5 If the widget is not a subclass of .PN compositeWidgetClass , .PN XtRealizeWidget returns; otherwise it continues and performs the following: .RS .IP \- 5 Descends recursively to each of the widget's managed children and calls the realize procedures. Primitive widgets that instantiate children are responsible for realizing those children themselves. .IP \- 5 Maps all of the managed children windows that have \fImapped_when_managed\fP .PN True . If a widget is managed but \fImapped_when_managed\fP is .PN False , the widget is allocated visual space but is not displayed. .RE .LP If the widget is a top-level shell widget (that is, it has no parent), and \fImapped_when_managed\fP is .PN True , .PN XtRealizeWidget maps the widget window. .LP .PN XtCreateWidget , .PN XtVaCreateWidget , .PN XtRealizeWidget , .PN XtManageChildren , .PN XtUnmanage\%Children , .PN XtUnrealizeWidget , .PN XtSetMappedWhenManaged , and .PN XtDestroy\%Widget maintain the following invariants: .IP \(bu 5 If a composite widget is realized, then all its managed children are realized. .IP \(bu 5 If a composite widget is realized, then all its managed children that have \fImapped_when_managed\fP .PN True are mapped. .LP All \*(xI 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, .PN XtRealizeWidget calls the procedures in reverse order of appearance in the .PN CompositePart \fIchildren\fP list. By default, this ordering of the realize procedures will result in the stacking order of any newly created subwindows being top-to-bottom in the order of appearance on the list, and the most recently created child will be at the bottom. .sp .LP To check whether or not a widget has been realized, use .PN XtIsRealized . .LP .IN "XtIsRealized" "" "@DEF@" .sM .FD 0 Boolean XtIsRealized(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(oI .LP .eM The .PN XtIsRealized function returns .PN 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. .LP Some widget procedures (for example, set_values) might wish to operate differently after the widget has been realized. .NH 3 Widget Instance Window Creation: The realize Procedure .XS \*(SN Widget Instance Window Creation: The realize Procedure .XE .LP The realize procedure pointer in a widget class is of type .PN XtRealizeProc . .LP .IN "XtRealizeProc" "" "@DEF@" .sM .FD 0 typedef void (*XtRealizeProc)(Widget, XtValueMask*, XSetWindowAttributes*); .br Widget \fIw\fP; .br XtValueMask *\fIvalue_mask\fP; .br XSetWindowAttributes *\fIattributes\fP; .FN .IP \fIw\fP 1i Specifies the widget. .IP \fIvalue_mask\fP 1i Specifies which fields in the \fIattributes\fP structure are used. .IP \fIattributes\fP 1i Specifies the window attributes to use in the .PN XCreateWindow call. .LP .eM The realize procedure must create the widget's window. .LP Before calling the class realize procedure, the generic .PN XtRealizeWidget function fills in a mask and a corresponding .PN XSetWindowAttributes structure. It sets the following fields in \fIattributes\fP and corresponding bits in \fIvalue_mask\fP based on information in the widget core structure: .IP \(bu 5 The \fIbackground_pixmap\fP (or \fIbackground_pixel\fP if \fIbackground_pixmap\fP is .PN XtUnspecifiedPixmap ) is filled in from the corresponding field. .IP \(bu 5 The \fIborder_pixmap\fP (or \fIborder_pixel\fP if \fIborder_pixmap\fP is .PN XtUnspecifiedPixmap ) is filled in from the corresponding field. .IP \(bu 5 The \fIcolormap\fP is filled in from the corresponding field. .IP \(bu 5 The \fIevent_mask\fP is filled in based on the event handlers registered, the event translations specified, whether the \fIexpose\fP field is non-NULL, and whether \fIvisible_interest\fP is .PN True . .IP \(bu 5 The \fIbit_gravity\fP is set to .PN NorthWestGravity if the \fIexpose\fP field is NULL. .LP These or any other fields in attributes and the corresponding bits in \fIvalue_mask\fP can be set by the realize procedure. .LP Note that because realize is not a chained operation, the widget class realize procedure must update the .PN XSetWindowAttributes structure with all the appropriate fields from non-Core superclasses. .LP .IN "Inheritance" A widget class can inherit its realize procedure from its superclass during class initialization. The realize procedure defined for .PN coreWidgetClass calls .PN XtCreateWindow with the passed \fIvalue_mask\fP and \fIattributes\fP and with \fIwindow_class\fP and \fIvisual\fP set to .PN CopyFromParent . Both .PN compositeWidgetClass and .PN constraintWidgetClass inherit this realize procedure, and most new widget subclasses can do the same (see Section 1.6.10). .LP The most common noninherited realize procedures set \fIbit_gravity\fP in the mask and attributes to the appropriate value and then create the window. For example, depending on its justification, Label might set \fIbit_gravity\fP to .PN WestGravity , .PN CenterGravity , or .PN EastGravity . Consequently, shrinking it would just move the bits appropriately, and no exposure event is needed for repainting. .LP 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 .PN XtRealizeWidget on its children itself in the appropriate order from within its own realize procedure. .LP Widgets that have children and whose class is not a subclass of .PN compositeWidgetClass are responsible for calling .PN XtRealizeWidget on their children, usually from within the realize procedure. .LP Realize procedures cannot manage or unmanage their descendants. .NH 3 Window Creation Convenience Routine .XS \*(SN Window Creation Convenience Routine .XE .LP Rather than call the Xlib .PN XCreateWindow .IN "realize procedure" function explicitly, a realize procedure should normally call the \*(xI analog .PN XtCreateWindow , which simplifies the creation of windows for widgets. .LP .IN "XtCreateWindow" "" "@DEF@" .sM .FD 0 void XtCreateWindow(\fIw\fP, \fIwindow_class\fP, \fIvisual\fP, \ \fIvalue_mask\fP, \fIattributes\fP) .br Widget \fIw\fP; .br unsigned int \fIwindow_class\fP; .br Visual *\fIvisual\fP; .br XtValueMask \fIvalue_mask\fP; .br XSetWindowAttributes *\fIattributes\fP; .FN .IP \fIw\fP 1i Specifies the widget that defines the additional window attributed. \*(cI .IP \fIwindow_class\fP 1i Specifies the Xlib window class (for example, .PN InputOutput , .PN InputOnly , or .PN CopyFromParent ). .IP \fIvisual\fP 1i Specifies the visual type (usually .PN CopyFromParent ). .ds Vm attribute fields to use .IP \fIvalue_mask\fP 1i Specifies which fields in the \fIattributes\fP structure are used. .IP \fIattributes\fP 1i Specifies the window attributes to use in the .PN XCreateWindow call. .LP .eM The .PN XtCreateWindow function calls the Xlib .PN XCreateWindow function with values from the widget structure and the passed parameters. Then, it assigns the created window to the widget's \fIwindow\fP field. .LP .PN XtCreateWindow evaluates the following fields of the widget core structure: \fIdepth\fP, \fIscreen\fP, \fIparent->core.window\fP, \fIx\fP, \fIy\fP, \fIwidth\fP, \fIheight\fP, and \fIborder_width\fP. .NH 2 Obtaining Window Information from a Widget .XS \fB\*(SN Obtaining Window Information from a Widget\fP .XE .LP The Core widget class definition contains the screen and window ids. The \fIwindow\fP field may be NULL for a while (see Sections 2.5 and 2.6). .LP 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. .LP .IN "XtDisplay" "" "@DEF@" .sM .FD 0 Display *XtDisplay(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(cI .LP .eM .PN XtDisplay returns the display pointer for the specified widget. .sp .LP .IN "XtParent" "" "@DEF@" .sM .FD 0 Widget XtParent(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(oI .LP .eM .PN XtParent returns the parent object for the specified widget. The returned object will be of class Object or a subclass. .sp .LP .IN "XtScreen" "" "@DEF@" .sM .FD 0 Screen *XtScreen(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(cI .LP .eM .PN XtScreen returns the screen pointer for the specified widget. .sp .LP .IN "XtWindow" "" "@DEF@" .sM .FD 0 Window XtWindow(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(cI .LP .eM .PN XtWindow returns the window of the specified widget. .sp .LP 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 .PN XtDisplayOfObject , .PN XtScreenOfObject , and .PN XtWindowOfObject . .IN "XtDisplayOfObject" "" "@DEF@" .sp .LP .sM .FD 0 Display *XtDisplayOfObject(\fIobject\fP) .br Widget \fIobject\fP; .FN .IP \fIobject\fP 1i Specifies the object. \*(oI .LP .eM .PN XtDisplayOfObject is identical in function to .PN XtDisplay if the object is a widget; otherwise .PN XtDisplayOfObject returns the display pointer for the nearest ancestor of \fIobject\fP that is of class Widget or a subclass thereof. .LP .IN "XtScreenOfObject" "" "@DEF@" .sM .FD 0 Screen *XtScreenOfObject(\fIobject\fP) .br Widget \fIobject\fP; .FN .IP \fIobject\fP 1i Specifies the object. \*(oI .LP .eM .PN XtScreenOfObject is identical in function to .PN XtScreen if the object is a widget; otherwise .PN XtScreenOfObject returns the screen pointer for the nearest ancestor of \fIobject\fP that is of class Widget or a subclass thereof. .LP .IN "XtWindowOfObject" "" "@DEF@" .sM .FD 0 Window XtWindowOfObject(\fIobject\fP) .br Widget \fIobject\fP; .FN .IP \fIobject\fP 1i Specifies the object. \*(oI .LP .eM .PN XtWindowOfObject is identical in function to .PN XtWindow if the object is a widget; otherwise .PN XtWindowOfObject returns the window for the nearest ancestor of \fIobject\fP that is of class Widget or a subclass thereof. .sp .LP To retrieve the instance name of an object, use .PN XtName . .LP .IN "XtName" "" "@DEF@" .sM .FD 0 String XtName(\fIobject\fP) .br Widget \fIobject\fP; .FN .IP \fIobject\fP 1i Specifies the object whose name is desired. \*(oI .LP .eM .PN XtName returns a pointer to the instance name of the specified object. The storage is owned by the \*(xI and must not be modified. The name is not qualified by the names of any of the object's ancestors. .LP Several window attributes are locally cached in the widget instance. Thus, they can be set by the resource manager and .PN XtSetValues as well as used by routines that derive structures from these values (for example, \fIdepth\fP for deriving pixmaps, \fIbackground_pixel\fP for deriving GCs, and so on) or in the .PN XtCreateWindow call. .LP The \fIx\fP, \fIy\fP, \fIwidth\fP, \fIheight\fP, and \fIborder_width\fP window attributes are available to geometry managers. These fields are maintained synchronously inside the \*(xI. When an .PN XConfigureWindow is issued by the \*(xI on the widget's window (on request of its parent), these values are updated immediately rather than some time later when the server generates a .PN ConfigureNotify event. (In fact, most widgets do not select .PN SubstructureNotify events.) This ensures that all geometry calculations are based on the internally consistent toolkit world rather than on either an inconsistent world updated by asynchronous .PN 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). .NH 3 Unrealizing Widgets .XS \fB\*(SN Unrealizing Widgets\fP .XE .LP To destroy the windows associated with a widget and its non-pop-up descendants, use .PN XtUnrealizeWidget . .LP .IN "XtUnrealizeWidget" "" "@DEF@" .sM .FD 0 void XtUnrealizeWidget(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(cI .LP .eM If the widget is currently unrealized, .PN XtUnrealizeWidget simply returns. Otherwise it performs the following: .IP \(bu 5 Unmanages the widget if the widget is managed. .IP \(bu 5 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 .IN XtNunrealizeCallback XtNunrealizeCallback list. .IN "unrealizeCallback" "" "@DEF@" .IP \(bu 5 Destroys the widget's window and any subwindows by calling .PN XDestroyWindow with the specified widget's \fIwindow\fP field. .LP Any events in the queue or which arrive following a call to .PN XtUnrealizeWidget will be dispatched as if the window(s) of the unrealized widget(s) had never existed. .NH 2 Destroying Widgets .XS \fB\*(SN Destroying Widgets\fP .XE .LP The \*(xI provide support .IP \(bu 5 To destroy all the pop-up children of the widget being destroyed and destroy all children of composite widgets. .IP \(bu 5 To remove (and unmap) the widget from its parent. .IP \(bu 5 To call the callback procedures that have been registered to trigger when the widget is destroyed. .IP \(bu 5 To minimize the number of things a widget has to deallocate when destroyed. .IP \(bu 5 To minimize the number of .PN XDestroyWindow calls when destroying a widget tree. .sp .LP To destroy a widget instance, use .PN XtDestroyWidget . .LP .IN "XtDestroyWidget" "" "@DEF@" .sM .FD 0 void XtDestroyWidget(\fIw\fP) .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget. \*(oI .LP .eM The .PN 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. .LP In phase 1, .PN XtDestroyWidget performs the following: .IP \(bu 5 If the \fIbeing_destroyed\fP field of the widget is .PN True , it returns immediately. .IP \(bu 5 Recursively descends the widget tree and sets the \fIbeing_destroyed\fP field to .PN True for the widget and all normal and pop-up children. .IP \(bu 5 Adds the widget to a list of widgets (the destroy list) that should be destroyed when it is safe to do so. .LP 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. .LP 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 managers, that is, when the current invocation of .PN XtDispatchEvent is about to return, or immediately if not in .PN XtDispatchEvent . .LP In phase 2, .PN XtDestroyWidget performs the following on each entry in the destroy list in the order specified: .IP \(bu 5 If the widget is not a pop-up child and the widget's parent is a subclass of .PN composite\%WidgetClass , and if the parent is not being destroyed, it calls .PN XtUnmanageChild on the widget and then calls the widget's parent's delete_child procedure (see Section 3.3). .IP \(bu 5 Calls the destroy callback procedures registered on the widget and all normal and pop-up descendants in postorder (it calls child callbacks before parent callbacks). .LP The .PN 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: .IP \(bu 5 If the widget is not a pop-up child and the widget's parent is a subclass of .PN constraint\%WidgetClass , it calls the .PN ConstraintClassPart destroy procedure for the parent, then for the parent's superclass, until finally it calls the .PN ConstraintClassPart destroy procedure for .PN constraintWidgetClass . .IP \(bu 5 Calls the .PN 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. Callback lists are deallocated. .IP \(bu 5 If the widget class object class part contains an .PN ObjectClassExtension record with the record_type .PN \s-1NULLQUARK\s+1 and the \fIdeallocate\fP field is not NULL, calls the deallocate procedure to deallocate the instance and if one exists, the constraint record. Otherwise, the \*(xI will deallocate the widget instance record and if one exists, the constraint record. .IP \(bu 5 Calls .PN XDestroyWindow if the specified widget is realized (that is, has an X window). The server recursively destroys all normal descendant windows. (Windows of realized pop-up Shell children, and their descendants, are destroyed by a shell class destroy procedure.) .NH 3 Adding and Removing Destroy Callbacks .XS \fB\*(SN Adding and Removing Destroy Callbacks\fP .XE .LP 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. .IN "Destroy Callbacks" The destroy callback list is identified by the resource name XtNdestroyCallback. .LP For example, the following adds an application-supplied destroy callback procedure \fIClientDestroy\fP with client data to a widget by calling .PN XtAddCallback . .IN "XtAddCallback" .Ds XtAddCallback(\fIw\fP, XtNdestroyCallback, \fIClientDestroy\fP, \fIclient_data\fP) .De .LP Similarly, the following removes the application-supplied destroy callback procedure \fIClientDestroy\fP by calling .PN XtRemoveCallback . .IN "XtRemoveCallback" .Ds XtRemoveCallback(\fIw\fP, XtNdestroyCallback, \fIClientDestroy\fP, \fIclient_data\fP) .De .LP The \fIClientDestroy\fP argument is of type .PN XtCallbackProc ; see Section 8.1. .NH 3 Dynamic Data Deallocation: The destroy Procedure .XS \*(SN Dynamic Data Deallocation: The destroy Procedure .XE .LP .IN "destroy procedure" "" "@DEF@" The destroy procedure pointers in the .PN ObjectClassPart , .PN RectObjClassPart , and .PN CoreClassPart structures are of type .PN XtWidgetProc . .LP .IN "XtWidgetProc" "" "@DEF@" .sM .FD 0 typedef void (*XtWidgetProc)(Widget); .br Widget \fIw\fP; .FN .IP \fIw\fP 1i Specifies the widget being destroyed. .LP .eM The destroy procedures are called in subclass-to-superclass order. Therefore, a widget's destroy procedure should deallocate only storage that is specific to the subclass and should ignore the storage allocated by any of its superclasses. 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. .LP Deallocating storage includes, but is not limited to, the following steps: .IP \(bu 5 Calling .PN XtFree on dynamic storage allocated with .PN XtMalloc , .PN XtCalloc , and so on. .IP \(bu 5 Calling .PN XFreePixmap on pixmaps created with direct X calls. .IP \(bu 5 Calling .PN XtReleaseGC on GCs allocated with .PN XtGetGC . .IP \(bu 5 Calling .PN XFreeGC on GCs allocated with direct X calls. .IP \(bu 5 Calling .PN XtRemoveEventHandler on event handlers added to other widgets. .IP \(bu 5 Calling .PN XtRemoveTimeOut on timers created with .PN XtAppAddTimeOut . .IP \(bu 5 Calling .PN XtDestroyWidget for each child if the widget has children and is not a subclass of .PN compositeWidgetClass . .LP During destroy phase 2 for each widget, the \*(xI 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. .NH 3 Dynamic Constraint Data Deallocation: The ConstraintClassPart destroy Procedure .XS \*(SN Dynamic Constraint Data Deallocation: The ConstraintClassPart destroy Procedure .XE .LP The constraint destroy procedure identified in the .PN ConstraintClassPart structure is called for a widget whose parent is a subclass of .PN constraintWidgetClass . This constraint destroy procedure pointer is of type .PN XtWidgetProc . The constraint destroy procedures are called in subclass-to-superclass order, starting at the class of the widget's parent and ending at .PN constraint\%WidgetClass . 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. .LP If a parent does not need to deallocate any constraint storage, the constraint destroy procedure entry in its class record can be NULL. .NH 3 Widget Instance Deallocation: The deallocate Procedure .XS \*(SN Widget Instance Deallocation: The deallocate Procedure .XE .LP .IN "deallocate procedure" "" "@DEF@" The deallocate procedure pointer in the .PN ObjectClassExtension record is of type .PN XtDeallocateProc . .LP .IN "XtDeallocateProc" "" "@DEF@" .sM .FD 0 typedef void (*XtDeallocateProc)(Widget, XtPointer); .br Widget \fIwidget\fP; .br XtPointer \fImore_bytes\fP; .FN .IP \fIwidget\fP 1i Specifies the widget being destroyed. .IP \fImore_bytes\fP 1i Specifies the auxiliary memory received from the corresponding allocator along with the widget, or NULL. .LP .eM When a widget is destroyed, if an .PN ObjectClassExtension record exists in the object class part \fIextension\fP field with \fIrecord_type\fP .PN \s-1NULLQUARK\s+1 and the \fIdeallocate\fP field is not NULL, the .PN XtDeallocateProc will be called. If no ObjectClassPart extension record is declared with \fIrecord_type\fP equal to .PN \s-1NULLQUARK\s+1 , then .PN XtInheritAllocate and .PN XtInheritDeallocate are assumed. The responsibilities of the deallocate procedure are to deallocate the memory specified by \fImore_bytes\fP if it is not NULL, to deallocate the constraints record as specified by the widget's \fIcore.constraints\fP field if it is not NULL, and to deallocate the widget instance itself. .LP If no .PN XtDeallocateProc is found, it is assumed that the \*(xI originally allocated the memory and is responsible for freeing it. .NH 2 Exiting from an Application .XS \fB\*(SN Exiting from an Application\fP .XE .LP All \*(tk applications should terminate by calling .PN XtDestroyApplicationContext and then exiting using the standard method for their operating system (typically, by calling .PN exit for POSIX-based systems). The quickest way to make the windows disappear while exiting is to call .PN XtUnmapWidget on each top-level shell widget. The \*(xI 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. .LP Depending upon the widget set in use, it may be necessary to explicitly destroy individual widgets or widget trees with .PN XtDestroyWidget before calling .PN XtDestroyApplicationContext in order to ensure that any required widget cleanup is properly 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. .bp