XtClass(3Xt)                         BSD                          XtClass(3Xt)



NAME
     XtClass, XtSuperClass, XtIsSubclass, XtCheckSubclass, XtIsComposite,
     XtIsManaged - 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(w, widget_class, message)
           Widget w;
           WidgetClass widget_class;
           String message;

     Boolean XtIsComposite(w)
           Widget w;

     Boolean XtIsManaged(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 widget class.  The
     specified widget can be any number of subclasses down the chain and need
     not be an immediate subclass of the specified widget 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.

     The XtIsComposite function is a convenience function that is equivalent
     to XtIsSubclass with compositeWidgetClass specified.

     The XtIsManaged macro (for widget programmers) or function (for
     application programmers) returns True if the specified child widget is
     managed or False if it is not.

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