XtClass(3Xt)

     NAME
          XtClass, XtSuperclass, XtIsSubclass, XtCheckSubclass,
          XtIsObject, XtIsRectObj, XtIsWidget, XtIsComposite,
          XtIsConstraint, XtIsShell, XtIsOverrideShell, XtIsWMShell,
          XtIsVendorShell, XtIsTransientShell, XtIsTopLevelShell,
          XtIsApplicationShell, XtIsSessionShell - obtain and verify a
          widget's class

     SYNTAX
          WidgetClass XtClass(w)
                Widget w;

          WidgetClass XtSuperclass(w)
                Widget w;

          Boolean XtIsSubclass(w, widget_class)
                Widget w;
                WidgetClass widget_class;

          void XtCheckSubclass(widget, widget_class, message)
                Widget widget;
                WidgetClass widget_class;
                String message;

          Boolean XtIsObject(w)
                Widget w;

          Boolean XtIsRectObj(w)
                Widget w;

          Boolean XtIsWidget(w)
                Widget w;

          Boolean XtIsComposite(w)
                Widget w;

          Boolean XtIsConstraint(w)
                Widget w;

          Boolean XtIsShell(w)
                Widget w;

          Boolean XtIsOverrideShell(w)
                Widget w;

          Boolean XtIsWMShell(w)
                Widget w;

          Boolean XtIsVendorShell(w)
                Widget w;

          Boolean XtIsTransientShell(w)
                Widget w;

          Boolean XtIsTopLevelShell(w)
                Widget w;

          Boolean XtIsApplicationShell(w)
                Widget w;

          Boolean XtIsSessionShell(w)
                Widget w;

     ARGUMENTS
          w         Specifies the widget.

          widget_class
                    Specifies the widget class.

          message   Specifies the message that is to be used.

     DESCRIPTION
          The XtClass function returns a pointer to the widget's class
          structure.

          The XtSuperclass function returns a pointer to the widget's
          superclass class structure.

          The XtIsSubclass function returns True if the class of the
          specified widget is equal to or is a subclass of the
          specified class. The widget's class can be any number of
          subclasses down the chain and need not be an immediate
          subclass of the specified class. Composite widgets that need
          to restrict the class of the items they contain can use
          XtIsSubclass to find out if a widget belongs to the desired
          class of objects.

          The XtCheckSubclass macro determines if the class of the
          specified widget is equal to or is a subclass of the
          specified widget class.  The widget can be any number of
          subclasses down the chain and need not be an immediate
          subclass of the specified widget class.  If the specified
          widget is not a subclass, XtCheckSubclass constructs an
          error message from the supplied message, the widget's actual
          class, and the expected class and calls XtErrorMsg.
          XtCheckSubclass should be used at the entry point of
          exported routines to ensure that the client has passed in a
          valid widget class for the exported operation.

          XtCheckSubclass is only executed when the widget has been
          compiled with the compiler symbol DEBUG defined; otherwise,
          it is defined as the empty string and generates no code.

          To test if a given widget belongs to a subclass of an
          Intrinsics-defined class, the Intrinsics defines macros or
          functions equivalent to XtIsSubclass for each of the built-
          in classes. These procedures are XtIsObject, XtIsRectObj,
          XtIsWidget, XtIsComposite, XtIsConstraint, XtIsShell,
          XtIsOverrideShell, XtIsWMShell, XtIsVendorShell,
          XtIsTransientShell, XtIsTopLevelShell, XtIsApplicationShell,
          and ZN XtIsSessionShell .

          The

     SEE ALSO
          XtAppErrorMsg(3Xt), XtDisplay(3Xt)
          X Toolkit Intrinsics - C Language Interface
          Xlib - C Language X Interface