hpux man page for delete_child

delete_child()															    delete_child()

Name
  delete_child - Composite class method called when a child is destroyed.

Synopsis
  typedef void (*XtWidgetProc)(Widget);
	 Widget w;

Inputs
  w	    Specifies the child that is to be removed from its parent's children array.

Description
  The delete_child() method is registered on the delete_child field of the Composite class part structure.  It is called by XtDestroyWidget()
  to remove a child from its parent's children array.

  Note that the argument to the delete_child() method is the child widget, not the composite widget that defines  the  method.	 This  method
  must	remove	the  specified	child from its parent's children array, and free up any other memory that the class uses to keep track of the
  child.

  The delete_child() method is not chained.  If a class does not define a delete_child() method, it should inherit the method from its super-
  class  by specifying XtInheritDeleteChild in the delete_child field of its Composite class part structure.  This field should not be set to
  NULL.

Usage
  Most widgets simply inherit the delete_child() method from their superclass.	Some widget classes, though,  create  companion  widgets  for
  each	of  their children (the Xaw Paned widget creates the Grip widgets that separate the panes, for example) or maintain information about
  each child that must be freed up when the child is destroyed.  These classes must provide their own delete_child() procedures.  These  pro-
  cedures  commonly  "envelop"	their superclass's method by providing a procedure that does class-specific processing and explicitly invokes
  the superclass method.  This technique allows a kind of non-automatic inheritance, and is shown in the example below.

  Note that the Composite insert_child() and delete_child() methods exploit internal common data structures, so you should inherit or envelop
  both	or neither.  If you do not inherit or envelop these methods, then your methods are responsible for adding and removing the child wid-
  get from the children array.

Example
  The following procedure is the delete_child() method of the Xaw Paned widget class.  Note how it destroys the Grip widget that was automat-
  ically  created  as a sibling of the child, and then explicitly invokes its superclass's delete_child() method to remove the child from the
  Composite children array.  See insert_child(4) for the corresponding insert_child() procedure.

     static void DeleteChild(w)
     Widget w;
     {
	 /* remove the subwidget info and destroy the grip */
	 if ( IsPane(w) && HasGrip(w) ) XtDestroyWidget(PaneInfo(w)->grip);

	 /* delete the child widget in the composite children list with the */
	 /* superclass delete_child routine.				    */
	 (*SuperClass->composite_class.delete_child) (w);

     } /* DeleteChild */

  In this example, SuperClass is a symbolic name for the superclass of the Paned widget class.	Note that this method does not determine  the
  superclass as follows:

	 XtSuperclass(XtParent(w))

  The  parent  of  w  may  be  a  subclass of Paned, and therefore its superclass pointer will not always be the class whose method should be
  invoked.

See Also
  Composite(3),
  insert_child(4).

Xt - Intrinsics Methods 													    delete_child()