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X Version 11 (Release 5)

XtCreateWidget(Xt)


XtCreateWidget -- create and destroy widgets

Syntax

Widget XtCreateWidget(name, widget_class, parent, args, num_args)
String name;
WidgetClass widget_class;
Widget parent;
ArgList args;
Cardinal num_args;

Widget XtCreateManagedWidget(name, widget_class, parent, args, num_args) String name; WidgetClass widget_class; Widget parent; ArgList args; Cardinal num_args;

void XtDestroyWidget(w) Widget w;

Arguments


args
Specifies the argument list to override the resource defaults.

name
Specifies the resource 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 same parent.

num_args
Specifies the number of arguments in the argument list.

parent
Specifies the parent widget.

w
Specifies the widget.

widget_class
Specifies the widget class pointer for the created widget.

Description

The XtCreateWidget function performs much of the boilerplate operations of widget creation:

Note that you can determine the number of arguments in an argument list by using the XtNumber macro. For further information, see Section 11.2 of X Toolkit Intrinsics - C Language Interface.

The XtCreateManagedWidget function is a convenience routine that calls XtCreateWidget and XtManageChild.

The XtDestroyWidget function provides the only method of destroying a widget, including widgets that need to destroy themselves. It can be called at any time, including from an application callback routine of the widget being destroyed. This requires a two-phase destroy process in order to avoid dangling references to destroyed widgets.

In phase one, XtDestroyWidget performs the following:


BULLET
If the being_destroyed field of the widget is True, it returns immediately.

BULLET
Recursively descends the widget tree and sets the being_destroyed field to True for the widget and all children.

BULLET
Adds the widget to a list of widgets (the destroy list) that should be destroyed when it is safe to do so.

Entries on the destroy list satisfy the invariant that if w2 occurs after w1 on the destroy list then w2 is not a descendent of w1. (A descendant refers to both normal and pop-up children.)

Phase two 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 XtDispatchEvent is about to return or immediately if not in XtDispatchEvent.

In phase two, XtDestroyWidget performs the following on each entry in the destroy list:


BULLET
Calls the destroy callback procedures registered on the widget (and all descendants) in post-order (it calls children callbacks before parent callbacks).

BULLET
If the widget's parent is a subclass of compositeWidgetClass and if the parent is not being destroyed, it calls XtUnmanageChild on the widget and then calls the widget's parent's delete_child procedure (see Section 3.4 of X Toolkit Intrinsics - C Language Interface).

BULLET
If the widget's parent is a subclass of constraintWidgetClass, it calls the constraint destroy procedure for the parent, then the parent's superclass, until finally it calls the constraint destroy procedure for constraintWidgetClass.

BULLET
Calls the destroy methods for the widget (and all descendants) in post-order. For each such widget, it calls the 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 Core class record.

BULLET
Calls XDestroyWindow if the widget is realized (that is, has an X window). The server recursively destroys all descendant windows.

BULLET
Recursively descends the tree and deallocates all pop-up widgets, constraint records, callback lists and, if the widget is a subclass of compositeWidgetClass, children.

See also

XtAppCreateShell(Xt) and XtCreatePopupShell(Xt).

X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface


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