XtClass(3Xt)               XT FUNCTIONS              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 wid-
       get'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 spec-
       ified widget class.  The specified widget can be any num-
       ber of subclasses down the chain and need not be an imme-
       diate 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 spec-
       ified widget class.  The widget can be any number of



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XtClass(3Xt)               XT FUNCTIONS              XtClass(3Xt)


       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; other-
       wise, 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 speci-
       fied 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































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