1XtCreateWidget(3)                XT FUNCTIONS                XtCreateWidget(3)
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3
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NAME

6       XtCreateWidget, XtVaCreateWidget, XtCreateManagedWidget, XtVaCreate‐
7       ManagedWidget, XtDestroyWidget - create and destroy widgets
8

SYNTAX

10       #include <X11/Intrinsic.h>
11
12       Widget XtCreateWidget(const char *name, WidgetClass widget_class, Wid‐
13              get parent, ArgList args, Cardinal num_args);
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15       Widget XtVaCreateWidget(const char *name, WidgetClass widget_class,
16              Widget parent, ...);
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18       Widget XtCreateManagedWidget(const char *name, WidgetClass wid‐
19              get_class, Widget parent, ArgList args, Cardinal num_args);
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21       Widget XtVaCreateManagedWidget(const char *name, WidgetClass wid‐
22              get_class, Widget parent, ...);
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24       void XtDestroyWidget(Widget w);
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ARGUMENTS

27       args      Specifies the argument list to override the resource
28                 defaults.
29
30       name      Specifies the resource name for the created widget, which is
31                 used for retrieving resources and, for that reason, should
32                 not be the same as any other widget that is a child of same
33                 parent.
34
35       num_args  Specifies the number of arguments in the argument list.
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37       parent    Specifies the parent widget.
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39       w         Specifies the widget.
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41       widget_class
42                 Specifies the widget class pointer for the created widget.
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44       ...       Specifies the variable argument list to override the resource
45                 defaults.
46

DESCRIPTION

48       The XtCreateWidget function performs much of the boilerplate operations
49       of widget creation:
50
51       ·    Checks to see if the class_initialize procedure has been called
52            for this class and for all superclasses and, if not, calls those
53            necessary in a superclass-to-subclass order.
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55       ·    Allocates memory for the widget instance.
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57       ·    If the parent is a subclass of constraintWidgetClass, it allocates
58            memory for the parent's constraints and stores the address of this
59            memory into the constraints field.
60
61       ·    Initializes the core nonresource data fields (for example, parent
62            and visible).
63
64       ·    Initializes the resource fields (for example, background_pixel) by
65            using the resource lists specified for this class and all super‐
66            classes.
67
68       ·    If the parent is a subclass of constraintWidgetClass, it initial‐
69            izes the resource fields of the constraints record by using the
70            constraint resource list specified for the parent's class and all
71            superclasses up to constraintWidgetClass.
72
73       ·    Calls the initialize procedures for the widget by starting at the
74            Core initialize procedure on down to the widget's initialize pro‐
75            cedure.
76
77       ·    If the parent is a subclass of compositeWidgetClass, it puts the
78            widget into its parent's children list by calling its parent's
79            insert_child procedure.  For further information, see Section 3.5.
80
81       ·    If the parent is a subclass of constraintWidgetClass, it calls the
82            constraint initialize procedures, starting at constraintWidget‐
83            Class on down to the parent's constraint initialize procedure.
84
85       Note that you can determine the number of arguments in an argument list
86       by using the XtNumber macro.  For further information, see Section
87       11.1.
88
89       The XtCreateManagedWidget function is a convenience routine that calls
90       XtCreateWidget and XtManageChild.
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92       The XtDestroyWidget function provides the only method of destroying a
93       widget, including widgets that need to destroy themselves.  It can be
94       called at any time, including from an application callback routine of
95       the widget being destroyed.  This requires a two-phase destroy process
96       in order to avoid dangling references to destroyed widgets.
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98       In phase one, XtDestroyWidget performs the following:
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100       ·    If the being_destroyed field of the widget is True, it returns
101            immediately.
102
103       ·    Recursively descends the widget tree and sets the being_destroyed
104            field to True for the widget and all children.
105
106       ·    Adds the widget to a list of widgets (the destroy list) that
107            should be destroyed when it is safe to do so.
108
109       Entries on the destroy list satisfy the invariant that if w2 occurs
110       after w1 on the destroy list then w2 is not a descendent of w1.  (A
111       descendant refers to both normal and pop-up children.)
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113       Phase two occurs when all procedures that should execute as a result of
114       the current event have been called (including all procedures registered
115       with the event and translation managers), that is, when the current
116       invocation of XtDispatchEvent is about to return or immediately if not
117       in XtDispatchEvent.
118
119       In phase two, XtDestroyWidget performs the following on each entry in
120       the destroy list:
121
122       ·    Calls the destroy callback procedures registered on the widget
123            (and all descendants) in post-order (it calls children callbacks
124            before parent callbacks).
125
126       ·    If the widget's parent is a subclass of compositeWidgetClass and
127            if the parent is not being destroyed, it calls XtUnmanageChild on
128            the widget and then calls the widget's parent's delete_child pro‐
129            cedure (see Section 3.4).
130
131       ·    If the widget's parent is a subclass of constraintWidgetClass, it
132            calls the constraint destroy procedure for the parent, then the
133            parent's superclass, until finally it calls the constraint destroy
134            procedure for constraintWidgetClass.
135
136       ·    Calls the destroy methods for the widget (and all descendants) in
137            post-order.  For each such widget, it calls the destroy procedure
138            declared in the widget class, then the destroy procedure declared
139            in its superclass, until finally it calls the destroy procedure
140            declared in the Core class record.
141
142       ·    Calls XDestroyWindow if the widget is realized (that is, has an X
143            window).  The server recursively destroys all descendant windows.
144
145       ·    Recursively descends the tree and deallocates all pop-up widgets,
146            constraint records, callback lists and, if the widget is a sub‐
147            class of compositeWidgetClass, children.
148

SEE ALSO

150       XtAppCreateShell(3), XtCreatePopupShell(3)
151       X Toolkit Intrinsics - C Language Interface
152       Xlib - C Language X Interface
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156X Version 11                      libXt 1.2.0                XtCreateWidget(3)
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