XtCreateWidget(3)		 XT FUNCTIONS		     XtCreateWidget(3)

NAME
       XtCreateWidget, XtVaCreateWidget, XtCreateManagedWidget, XtVaCreate‐
       ManagedWidget, XtDestroyWidget - create and destroy widgets

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

       Widget XtVaCreateWidget(String name, WidgetClass widget_class, Widget
	      parent, ...);

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

       Widget XtVaCreateManagedWidget(String name, WidgetClass widget_class,
	      Widget parent, ...);

       void XtDestroyWidget(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.

       ...	 Specifies the variable argument list to override the resource
		 defaults.

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

       ·    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.

       ·    Allocates memory for the widget instance.

       ·    If the parent is a subclass of constraintWidgetClass, it allocates
	    memory for the parent's constraints and stores the address of this
	    memory into the constraints field.

       ·    Initializes the core nonresource data fields (for example, parent
	    and visible).

       ·    Initializes the resource fields (for example, background_pixel) by
	    using the resource lists specified for this class and all super‐
	    classes.

       ·    If the parent is a subclass of constraintWidgetClass, it initial‐
	    izes the resource fields of the constraints record by using the
	    constraint resource list specified for the parent's class and all
	    superclasses up to constraintWidgetClass.

       ·    Calls the initialize procedures for the widget by starting at the
	    Core initialize procedure on down to the widget's initialize pro‐
	    cedure.

       ·    If the parent is a subclass of compositeWidgetClass, it puts the
	    widget into its parent's children list by calling its parent's
	    insert_child procedure.  For further information, see Section 3.5.

       ·    If the parent is a subclass of constraintWidgetClass, it calls the
	    constraint initialize procedures, starting at constraintWidget‐
	    Class on down to the parent's constraint initialize procedure.

       Note that you can determine the number of arguments in an argument list
       by using the XtNumber macro.  For further information, see Section
       11.1.

       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:

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

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

       ·    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:

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

       ·    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 pro‐
	    cedure (see Section 3.4).

       ·    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.

       ·    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.

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

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

SEE ALSO
       XtAppCreateShell(3Xt), XtCreatePopupShell(3Xt)
       X Toolkit Intrinsics - C Language Interface
       Xlib - C Language X Interface

X Version 11			  libXt 1.0.9		     XtCreateWidget(3)

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