archie/tk4.2/doc/SetClass.3

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'\" Copyright (c) 1990 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\" SCCS: @(#) SetClass.3 1.12 96/03/26 18:18:10
'\" 
.so man.macros
.TH Tk_SetClass 3 "" Tk "Tk Library Procedures"
.BS
.SH NAME
Tk_SetClass, Tk_Class \- set or retrieve a window's class
.SH SYNOPSIS
.nf
\fB#include <tk.h>\fR
.sp
\fBTk_SetClass\fR(\fItkwin, class\fR)
.sp
Tk_Uid
\fBTk_Class\fR(\fItkwin\fR)
.SH ARGUMENTS
.AS Tk_Window parent
.AP Tk_Window tkwin in
Token for window.
.AP char *class in
New class name for window.
.BE

.SH DESCRIPTION
.PP
\fBTk_SetClass\fR is called to associate a class with a particular
window.  The \fIclass\fR string identifies the type of the
window;  all windows with the same general class of behavior
(button, menu, etc.) should have the same class.  By
convention all class names start with a capital letter, and
there exists a Tcl command with the same name as
each class (except all in lower-case) which can be used to
create and manipulate windows of that class.
A window's class string is initialized to NULL
when the window is created.
.PP
For main windows, Tk automatically propagates the name and class
to the WM_CLASS property used by window managers.  This happens
either when a main window is actually created (e.g. in
\fBTk_MakeWindowExist\fR), or when \fBTk_SetClass\fR
is called, whichever occurs later.  If a main window has not been
assigned a class then Tk will not set the WM_CLASS property for
the window.
.PP
\fBTk_Class\fR is a macro that returns the
current value of \fItkwin\fR's class.  The value is returned
as a Tk_Uid, which may be used just like a string pointer but also has
the properties of a unique identifier (see the manual entry for
\fBTk_GetUid\fR for details).
If \fItkwin\fR has not yet been given a class, then
\fBTk_Class\fR will return NULL.

.SH KEYWORDS
class, unique identifier, window, window manager