bindtags(3tk)
NAME
bindtags - Determine which bindings apply to a window, and order of evaluation
SYNOPSIS
bindtags window ?tagList? ______________________________________________________________________________
DESCRIPTION
When a binding is created with the bind command, it is associated
either with a particular window such as .a.b.c, a class name such as
Button, the keyword all, or any other string. All of these forms are
called binding tags. 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 bind command for more information
on the matching process.
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 all, in that order. Toplevel windows have only
three tags by default, since the toplevel name is the same as that of
the window. The bindtags command allows the binding tags for a window
to be read and modified.
If bindtags is invoked with only one argument, then the current set of
binding tags for window is returned as a list. If the tagList argument
is specified to bindtags, then it must be a proper list; the tags for
window are changed to the elements of the list. The elements of
tagList 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 tagList determines the order in
which binding scripts are executed in response to events. For example,
the command
bindtags .b {all . Button .b}
reverses the order in which binding scripts will be evaluated for a
button named .b so that all bindings are invoked first, following by
bindings for .b's toplevel ("."), followed by class bindings, followed
by bindings for .b. If tagList is an empty list then the binding tags
for window are returned to the default state described above.
The bindtags command may be used to introduce arbitrary additional
binding tags for a window, or to remove standard tags. For example,
the command
bindtags .b {.b TrickyButton . all}
replaces the Button tag for .b with TrickyButton. This means that the
default widget bindings for buttons, which are associated with the
Button tag, will no longer apply to .b, but any bindings associated
with TrickyButton (perhaps some new button behavior) will apply.
EXAMPLE
If you have a set of nested frame widgets and you want events sent to a
button widget to also be delivered to all the widgets up to the current
toplevel (in contrast to Tk's default behavior, where events are not
delivered to those intermediate windows) to make it easier to have
accelerators that are only active for part of a window, you could use a
helper procedure like this to help set things up:
proc setupBindtagsForTreeDelivery {widget} {
set tags [list $widget [winfo class $widget]]
set w $widget
set t [winfo toplevel $w]
while {$w ne $t} {
set w [winfo parent $w]
lappend tags $w
}
lappend tags all
bindtags $widget $tags
}
SEE ALSO
bind(3tk)
KEYWORDS
binding, event, tag
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