XtClass(3Xt)                                         XtClass(3Xt)



NAME
     XtClass, XtSuperClass, XtIsSubclass, XtCheckSubclass,
     XtIsComposite, XtIsManaged - get and verify a widget's class

SYNOPSIS
     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)

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.

     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 sup-
     plied 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



November, 1990                                                  1

XtClass(3Xt)                                         XtClass(3Xt)



     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.

   Arguments
     These functions and macros accept the following arguments:

     w       Specifies the widget.

     widget-class
             Specifies the widget class.

     message Specifies the message that is to be used.

SEE ALSO
     XtAppErrorMsg(3Xt), XtDisplay(3Xt)

     X Toolkit Intrinsics - C Language Interface

     Xlib - C Language Interface


























2                                                  November, 1990