.\" $Xorg: XtClass.man,v 1.3 2000/08/17 19:41:59 cpqbld Exp $
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.ds tk X Toolkit
.ds xT X Toolkit Intrinsics \- C Language Interface
.ds xI Intrinsics
.ds xW X Toolkit Athena Widgets \- C Language Interface
.ds xL Xlib \- C Language X Interface
.ds xC Inter-Client Communication Conventions Manual
.ds Rn 3
.ds Vn 2.2
.hw XtCheck-Subclass XtIs-Object XtIs-RectObj XtIs-Widget XtIs-Composite XtIs-Constraint XtIs-Shell XtIs-Override-Shell XtIs-WM-Shell XtIs-Vendor-Shell XtIs-Transient-Shell XtIs-Top-Level-Shell XtIs-Application-Shell wid-get
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.TH XtClass 3Xt __xorgversion__ "XT FUNCTIONS"
.SH NAME
XtClass, XtSuperclass, XtIsSubclass, XtCheckSubclass, XtIsObject, XtIsRectObj, XtIsWidget, XtIsComposite, XtIsConstraint, XtIsShell, XtIsOverrideShell, XtIsWMShell, XtIsVendorShell, XtIsTransientShell, XtIsTopLevelShell, XtIsApplicationShell, XtIsSessionShell \- obtain and verify a widget's class
.SH SYNTAX
.HP
WidgetClass XtClass(Widget \fIw\fP); 
.HP
WidgetClass XtSuperclass(Widget \fIw\fP); 
.HP
Boolean XtIsSubclass(Widget \fIw\fP, WidgetClass \fIwidget_class\fP); 
.HP
void XtCheckSubclass(Widget \fIwidget\fP, WidgetClass \fIwidget_class\fP,
String \fImessage\fP); 
.HP
Boolean XtIsObject(Widget \fIw\fP); 
.HP
Boolean XtIsRectObj(Widget \fIw\fP); 
.HP
Boolean XtIsWidget(Widget \fIw\fP); 
.HP
Boolean XtIsComposite(Widget \fIw\fP); 
.HP
Boolean XtIsConstraint(Widget \fIw\fP, 
.HP
Boolean XtIsShell(Widget \fIw\fP); 
.HP
Boolean XtIsOverrideShell(Widget \fIw\fP); 
.HP
Boolean XtIsWMShell(Widget \fIw\fP); 
.HP
Boolean XtIsVendorShell(Widget \fIw\fP);
.HP
Boolean XtIsTransientShell(Widget \fIw\fP);
.HP
Boolean XtIsTopLevelShell(Widget \fIw\fP);
.HP
Boolean XtIsApplicationShell(Widget \fIw\fP);
.HP
Boolean XtIsSessionShell(Widget \fIw\fP);
.SH ARGUMENTS
.IP \fIw\fP 1i
Specifies the widget.
.IP \fIwidget_class\fP 1i
Specifies the widget class\*(Wc.
.ds Me used
.IP \fImessage\fP 1i
Specifies the message that is to be \*(Me.
.SH DESCRIPTION
The
.ZN XtClass
function returns a pointer to the widget's class structure.
.LP
The
.ZN XtSuperclass
function returns a pointer to the widget's superclass class structure.
.LP
The
.ZN XtIsSubclass
function returns 
.ZN True 
if the class of the specified widget is equal to or is a subclass of 
the specified class. The widget's class can be any number of subclasses
down the chain and need not be an immediate subclass of the specified
class. Composite widgets that need to restrict the class of the items
they contain can use
.ZN XtIsSubclass
to find out if a widget belongs to the desired class of objects.
.LP
The
.ZN 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,
.ZN XtCheckSubclass
constructs an error message from the supplied message,
the widget's actual class, and the expected class and calls
.ZN XtErrorMsg .
.ZN 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.
.LP
.ZN 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.
.LP
To test if a given widget belongs to a subclass of an Intrinsics-defined
class, the Intrinsics defines macros or functions equivalent to
.ZN XtIsSubclass
for each of the built-in classes. These procedures are
.ZN XtIsObject ,
.ZN XtIsRectObj ,
.ZN XtIsWidget ,
.ZN XtIsComposite ,
.ZN XtIsConstraint ,
.ZN XtIsShell ,
.ZN XtIsOverrideShell ,
.ZN XtIsWMShell ,
.ZN XtIsVendorShell ,
.ZN XtIsTransientShell ,
.ZN XtIsTopLevelShell ,
.ZN XtIsApplicationShell ,
and
.ZN XtIsSessionShell .
.LP
The
.SH "SEE ALSO"
XtAppErrorMsg(3Xt),
XtDisplay(3Xt)
.br
\fI\*(xT\fP
.br
\fI\*(xL\fP