XtClass(3Xt)        RISC/os Reference Manual         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 speci-
     fied 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.





                         Printed 1/24/91  1 September 1988 Page 1

XtClass(3Xt)        RISC/os Reference Manual         XtClass(3Xt)



     The XtCheckSubclass macro determines if the class of the
     specified widget is equal to or is a subclass of the speci-
     fied widget class.  The widget can be any number of subc-
     lasses 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 speci-
     fied.

     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



























1 September 1988 Page 2  Printed 1/24/91