XtCreateWidget(3Xt)                  SysV                  XtCreateWidget(3Xt)



NAME
     XtCreateWidget, XtCreateManagedWidget, XtDestroyWidget - 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:

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