change_managed()														  change_managed()

Name
  change_managed     -	   Composite	 class	   method     to     respond	 to	a     change	 in	a     list     of     managed
  widgets.

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

Inputs
  w	    Specifies the widget that has had children managed or unmanaged.

Description
  The change_managed() method is registered on the change_managed field of the Composite class part structure, and is invoked when a child or
  children are managed or unmanaged with XtManageChild(), XtManageChildren(), XtUnmanageChild(), or XtUnmanageChildren().

  When	a  child  is managed or unmananged, it generally means that the layout of all the children of the widget should be redone.  Note that
  this method does not have an argument which specifies which children have had their managed state changed.   change_managed()  should  loop
  through  all	of the children in its children array, using XtIsManaged() to determine which are managed and should therefore be included in
  the layout calculations.

  The change_managed() method is not chained.  A widget class that does not define a change_managed() method can inherit this method from its
  superclass by specifying XtInheritChangeManaged in its Composite change_managed() class field.

Usage
  Many	change_managed()  methods  simply  call a general layout routine which may also be called from other places in the widget such as the
  resize() method.

Example
  The following procedure is the change_managed() method for the Xaw Form widget.  Note how it loops through all  of  its  children,  setting
  constraint  fields for those that are managed, and then calls a layout routine (which is a class method of the Form widget in this case) to
  recalculate the layout of all children.  It makes no attempt to determine which children have been managed or unmanaged.

     static void ChangeManaged(w)
	 Widget w;
     {
       FormWidget fw = (FormWidget)w;
       FormConstraints form;
       WidgetList children, childP;
       int num_children = fw->composite.num_children;
       Widget child;

       /*
	* Reset virtual width and height for all children.
	*/

       for (children = childP = fw->composite.children ;
	    childP - children < num_children; childP++) {
	 child = *childP;
	 if (XtIsManaged(child)) {
	   form = (FormConstraints)child->core.constraints;

     /*
      * If the size is one (1) then we must not change the virtual sizes, as
      * they contain useful information.  If someone actually wants a widget
      * of width or height one (1) in a form widget he will lose, can't win
      * them all.
      *
      * Chris D. Peterson 2/9/89.
      */

	   if ( child->core.width != 1)
	     form->form.virtual_width = (int) child->core.width;
	   if ( child->core.height != 1)
	     form->form.virtual_height = (int) child->core.height;
	 }
       }
       (*((FormWidgetClass)w->core.widget_class)->form_class.layout)
					      ((FormWidget) w, w->core.width,
					       w->core.height, TRUE);
     }

See Also
  Composite(3), Constraint(3).

Xt - Intrinsics Methods 													  change_managed()