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'\" Copyright (c) 1990 The Regents of the University of California.
'\" Copyright (c) 1994-1995 Sun Microsystems, Inc.
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" @(#) bindtags.n 1.6 95/08/12 17:35:01
.so STk-man.macros
.TH bindtags n 4.0 STk "Tk Built-In Commands"
'\" Note: do not modify the .SH NAME line immediately below!
bindtags \- Determine which bindings apply to a window, and order of evaluation
(\fBbindtags \fIwindow \fR?\fItagList\fR?)
When a binding is created with the \fBbind\fR procedure, it is
associated either with a particular window such as \fB.a.b.c\fR,
a class name such as \fBButton\fR, the constant \fB"all"\fR, or any
other string.
All of these forms are called \fIbinding tags\fR.
Each window contains a list of binding tags that determine how
events are processed for the window.
When an event occurs in a window, it is applied to each of the
window's tags in order: for each tag, the most specific binding
that matches the given tag and event is executed.
See the \fBbind\fR procedure for more information on the matching
By default, each window has four binding tags consisting of the
name of the window, the window's class name, the name of the window's
nearest toplevel ancestor, and \fB"all"\fR, in that order.
Toplevel windows have only three tags by default, since the toplevel
name is the same as that of the window.
The \fBbindtags\fR procedure allows the binding tags for a window to be
read and modified.
If \fBbindtags\fR is invoked with only one argument, then the
current set of binding tags for \fIwindow\fR is returned as a list.
If the \fItagList\fR argument is specified to \fBbindtags\fR,
then it must be a proper list; the tags for \fIwindow\fR are changed
to the elements of the list.
The elements of \fItagList\fR may be arbitrary strings; however,
any tag starting with a dot is treated as the name of a window; if
no window by that name exists at the time an event is processed,
then the tag is ignored for that event.
The order of the elements in \fItagList\fR determines the order in
which binding scripts are executed in response to events.
For example, the call
\fB(bindtags .b '("all" *root* "Button" .b))\fR
reverses the order in which binding scripts will be evaluated for
a button named \fB.b\fR so that \fB"all"\fR bindings are invoked
first, following by bindings for \fB.b\fR's toplevel (\fB*root\fR* or ``.''),
followed by class bindings, followed by bindings for \fB.b\fR.
If \fItagList\fR is an empty list then the binding tags for \fIwindow\fR
are returned to the default state described above.
The \fBbindtags\fR procedure may be used to introduce arbitrary
additional binding tags for a window, or to remove standard tags.
For example,
\fB(bindtags .b '(.b "TrickyButton" *root* "all"})\fR
replaces the \fBButton\fR tag for \fB.b\fR with \fBTrickyButton\fR.
This means that the default widget bindings for buttons, which are
associated with the \fBButton\fR tag, will no longer apply to \fB.b\fR,
but any bindings associated with \fBTrickyButton\fR (perhaps some
new button behavior) will apply.