NAME

       XtCreateWidget, XtVaCreateWidget, XtCreateManagedWidget, XtVaCreateManagedWidget,
       XtDestroyWidget - create and destroy widgets

SYNTAX

       #include <X11/Intrinsic.h>

       Widget XtCreateWidget(const char *name, WidgetClass widget_class, Widget parent, ArgList
              args, Cardinal num_args);

       Widget XtVaCreateWidget(const char *name, WidgetClass widget_class, Widget parent, ...);

       Widget XtCreateManagedWidget(const char *name, WidgetClass widget_class, Widget parent,
              ArgList args, Cardinal num_args);

       Widget XtVaCreateManagedWidget(const char *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 superclasses.

       •    If the parent is a subclass of constraintWidgetClass, it initializes 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 procedure.

       •    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 constraintWidgetClass 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 procedure (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 subclass of compositeWidgetClass, children.

SEE ALSO

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