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 XtClass(Xt)       X Version 11 (Release 5) 6 January 1993        XtClass(Xt)


 Name

    XtClass - 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.

    widgetclass
              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 immedi-
    ate 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 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 applica-
    tion programmers) returns True if the specified child widget is managed
    or False if it is not.

 See also

    XtAppErrorMsg(Xt) and XtDisplay(Xt).

    X Toolkit Intrinsics - C Language Interface
    Xlib - C Language X Interface