1XtCreateWidget(3) XT FUNCTIONS XtCreateWidget(3)
2
6 XtCreateWidget, XtVaCreateWidget, XtCreateManagedWidget, XtVaCreate‐
7 ManagedWidget, XtDestroyWidget - create and destroy widgets
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10 Widget XtCreateWidget(String name, WidgetClass widget_class, Widget
11 parent, ArgList args, Cardinal num_args);
12 Widget XtVaCreateWidget(String name, WidgetClass widget_class, Widget
14 parent, ...);
15 Widget XtCreateManagedWidget(String name, WidgetClass widget_class,
17 Widget parent, ArgList args, Cardinal num_args);
18 Widget XtVaCreateManagedWidget(String name, WidgetClass widget_class,
20 Widget parent, ...);
21 void XtDestroyWidget(Widget w);
23
25 args Specifies the argument list to override the resource
26 defaults.
27 name Specifies the resource name for the created widget, which is
29 used for retrieving resources and, for that reason, should
30 not be the same as any other widget that is a child of same
31 parent.
32 num_args Specifies the number of arguments in the argument list.
34 parent Specifies the parent widget.
36 w Specifies the widget.
38 widget_class
40 Specifies the widget class pointer for the created widget.
41 ... Specifies the variable argument list to override the resource
43 defaults.
44
46 The XtCreateWidget function performs much of the boilerplate operations
47 of widget creation:
48 · Checks to see if the class_initialize procedure has been called
50 for this class and for all superclasses and, if not, calls those
51 necessary in a superclass-to-subclass order.
52 · Allocates memory for the widget instance.
54 · If the parent is a subclass of constraintWidgetClass, it allocates
56 memory for the parent's constraints and stores the address of this
57 memory into the constraints field.
58 · Initializes the core nonresource data fields (for example, parent
60 and visible).
61 · Initializes the resource fields (for example, background_pixel) by
63 using the resource lists specified for this class and all super‐
64 classes.
65 · If the parent is a subclass of constraintWidgetClass, it initial‐
67 izes the resource fields of the constraints record by using the
68 constraint resource list specified for the parent's class and all
69 superclasses up to constraintWidgetClass.
70 · Calls the initialize procedures for the widget by starting at the
72 Core initialize procedure on down to the widget's initialize pro‐
73 cedure.
74 · If the parent is a subclass of compositeWidgetClass, it puts the
76 widget into its parent's children list by calling its parent's
77 insert_child procedure. For further information, see Section 3.5.
78 · If the parent is a subclass of constraintWidgetClass, it calls the
80 constraint initialize procedures, starting at constraintWidget‐
81 Class on down to the parent's constraint initialize procedure.
82 Note that you can determine the number of arguments in an argument list
84 by using the XtNumber macro. For further information, see Section
85 11.1.
86 The XtCreateManagedWidget function is a convenience routine that calls
88 XtCreateWidget and XtManageChild.
89 The XtDestroyWidget function provides the only method of destroying a
91 widget, including widgets that need to destroy themselves. It can be
92 called at any time, including from an application callback routine of
93 the widget being destroyed. This requires a two-phase destroy process
94 in order to avoid dangling references to destroyed widgets.
95 In phase one, XtDestroyWidget performs the following:
97 · If the being_destroyed field of the widget is True, it returns
99 immediately.
100 · Recursively descends the widget tree and sets the being_destroyed
102 field to True for the widget and all children.
103 · Adds the widget to a list of widgets (the destroy list) that
105 should be destroyed when it is safe to do so.
106 Entries on the destroy list satisfy the invariant that if w2 occurs
108 after w1 on the destroy list then w2 is not a descendent of w1. (A
109 descendant refers to both normal and pop-up children.)
110 Phase two occurs when all procedures that should execute as a result of
112 the current event have been called (including all procedures registered
113 with the event and translation managers), that is, when the current
114 invocation of XtDispatchEvent is about to return or immediately if not
115 in XtDispatchEvent.
116 In phase two, XtDestroyWidget performs the following on each entry in
118 the destroy list:
119 · Calls the destroy callback procedures registered on the widget
121 (and all descendants) in post-order (it calls children callbacks
122 before parent callbacks).
123 · If the widget's parent is a subclass of compositeWidgetClass and
125 if the parent is not being destroyed, it calls XtUnmanageChild on
126 the widget and then calls the widget's parent's delete_child pro‐
127 cedure (see Section 3.4).
128 · If the widget's parent is a subclass of constraintWidgetClass, it
130 calls the constraint destroy procedure for the parent, then the
131 parent's superclass, until finally it calls the constraint destroy
132 procedure for constraintWidgetClass.
133 · Calls the destroy methods for the widget (and all descendants) in
135 post-order. For each such widget, it calls the destroy procedure
136 declared in the widget class, then the destroy procedure declared
137 in its superclass, until finally it calls the destroy procedure
138 declared in the Core class record.
139 · Calls XDestroyWindow if the widget is realized (that is, has an X
141 window). The server recursively destroys all descendant windows.
142 · Recursively descends the tree and deallocates all pop-up widgets,
144 constraint records, callback lists and, if the widget is a sub‐
145 class of compositeWidgetClass, children.
146
148 XtAppCreateShell(3), XtCreatePopupShell(3)
149 X Toolkit Intrinsics - C Language Interface
150 Xlib - C Language X Interface
151X Version 11 libXt 1.1.4 XtCreateWidget(3)