NAME
bind - Arrange for X events to invoke Tcl scripts
SYNOPSIS
bind tag
bind tag sequence
bind tag sequence script
bind tag sequence +script
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INTRODUCTION
The bind command associates Tcl scripts with X events. If
all three arguments are specified, bind will arrange for
script (a Tcl script) to be evaluated whenever the
event(s) given by sequence occur in the window(s) identi-
fied by tag. If script is prefixed with a ``+'', then it
is appended to any existing binding for sequence; other-
wise script replaces any existing binding. If script is
an empty string then the current binding for sequence is
destroyed, leaving sequence unbound. In all of the cases
where a script argument is provided, bind returns an empty
string.
If sequence is specified without a script, then the script
currently bound to sequence is returned, or an empty
string is returned if there is no binding for sequence.
If neither sequence nor script is specified, then the
return value is a list whose elements are all the
sequences for which there exist bindings for tag.
The tag argument determines which window(s) the binding
applies to. If tag begins with a dot, as in .a.b.c, then
it must be the path name for a window; otherwise it may be
an arbitrary string. Each window has an associated list
of tags, and a binding applies to a particular window if
its tag is among those specified for the window. Although
the bindtags command may be used to assign an arbitrary
set of binding tags to a window, the default binding tags
provide the following behavior:
If a tag is the name of an internal window the
binding applies to that window.
If the tag is the name of a toplevel window the
binding applies to the toplevel window and all its
internal windows.
that class;
If tag has the value all, the binding applies to
all windows in the application.
EVENT PATTERNS
The sequence argument specifies a sequence of one or more
event patterns, with optional white space between the pat-
terns. Each event pattern may take one of three forms. |
In the simplest case it is a single printing ASCII charac-
ter, such as a or [. The character may not be a space
character or the character <. This form of pattern
matches a KeyPress event for the particular character.
The second form of pattern is longer but more general. It
has the following syntax:
<modifier-modifier-type-detail>
The entire event pattern is surrounded by angle brackets.
Inside the angle brackets are zero or more modifiers, an
event type, and an extra piece of information (detail)
identifying a particular button or keysym. Any of the
fields may be omitted, as long as at least one of type and
detail is present. The fields must be separated by white
space or dashes. |
The third form of pattern is used to specify a user- |
defined, named virtual event. It has the following syn- |
tax: |
<<name>> |
The entire virtual event pattern is surrounded by double |
angle brackets. Inside the angle brackets is the user- |
defined name of the virtual event. Modifiers, such as |
Shift or Control, may not be combined with a virtual event |
to modify it. Bindings on a virtual event may be created |
before the virtual event is defined, and if the definition |
of a virtual event changes dynamically, all windows bound |
to that virtual event will respond immediately to the new |
definition.
MODIFIERS
Modifiers consist of any of the following values:
Control Mod2, M2
Shift Mod3, M3
Lock Mod4, M4
Button1, B1 Mod5, M5
Button2, B2 Meta, M
Button3, B3 Alt
Button4, B4 Double
Button5, B5 Triple
Mod1, M1
obvious X meanings. For example, Button1 requires that
button 1 be depressed when the event occurs. For a bind-
ing to match a given event, the modifiers in the event
must include all of those specified in the event pattern.
An event may also contain additional modifiers not speci-
fied in the binding. For example, if button 1 is pressed
while the shift and control keys are down, the pattern
<Control-Button-1> will match the event, but
<Mod1-Button-1> will not. If no modifiers are specified,
then any combination of modifiers may be present in the
event.
Meta and M refer to whichever of the M1 through M5 modi-
fiers is associated with the meta key(s) on the keyboard
(keysyms Meta_R and Meta_L). If there are no meta keys,
or if they are not associated with any modifiers, then
Meta and M will not match any events. Similarly, the Alt
modifier refers to whichever modifier is associated with
the alt key(s) on the keyboard (keysyms Alt_L and Alt_R).
The Double and Triple modifiers are a convenience for
specifying double mouse clicks and other repeated events.
They cause a particular event pattern to be repeated 2 or
3 times, and also place a time and space requirement on
the sequence: for a sequence of events to match a Double
or Triple pattern, all of the events must occur close
together in time and without substantial mouse motion in
between. For example, <Double-Button-1> is equivalent to
<Button-1><Button-1> with the extra time and space
requirement.
EVENT TYPES
The type field may be any of the standard X event types,
with a few extra abbreviations. Below is a list of all
the valid types; where two names appear together, they are
synonyms.
ButtonPress, Button Expose Map
ButtonRelease FocusIn Motion
Circulate FocusOut Property
Colormap Gravity Reparent
Configure KeyPress, Key Unmap
Destroy KeyRelease Visibility
Enter Leave Activate
Deactivate
The last part of a long event specification is detail. In
the case of a ButtonPress or ButtonRelease event, it is
the number of a button (1-5). If a button number is
given, then only an event on that particular button will
is different than specifying a button modifier; in the
first case, it refers to a button being pressed or
released, while in the second it refers to some other but-
ton that is already depressed when the matching event
occurs. If a button number is given then type may be
omitted: if will default to ButtonPress. For example,
the specifier <1> is equivalent to <ButtonPress-1>.
If the event type is KeyPress or KeyRelease, then detail
may be specified in the form of an X keysym. Keysyms are
textual specifications for particular keys on the key-
board; they include all the alphanumeric ASCII characters
(e.g. ``a'' is the keysym for the ASCII character ``a''),
plus descriptions for non-alphanumeric characters
(``comma'' is the keysym for the comma character), plus
descriptions for all the non-ASCII keys on the keyboard
(``Shift_L'' is the keysm for the left shift key, and
``F1'' is the keysym for the F1 function key, if it
exists). The complete list of keysyms is not presented
here; it is available in other X documentation and may
vary from system to system. If necessary, you can use the
%K notation described below to print out the keysym name
for a particular key. If a keysym detail is given, then
the type field may be omitted; it will default to Key-
Press. For example, <Control-comma> is equivalent to
<Control-KeyPress-comma>.
BINDING SCRIPTS AND SUBSTITUTIONS
The script argument to bind is a Tcl script, which will be
executed whenever the given event sequence occurs. Com-
mand will be executed in the same interpreter that the
bind command was executed in, and it will run at global
level (only global variables will be accessible). If
script contains any % characters, then the script will not
be executed directly. Instead, a new script will be gen-
erated by replacing each %, and the character following
it, with information from the current event. The replace-
ment depends on the character following the %, as defined
in the list below. Unless otherwise indicated, the
replacement string is the decimal value of the given field
from the current event. Some of the substitutions are
only valid for certain types of events; if they are used
for other types of events the value substituted is unde-
fined.
%% Replaced with a single percent.
%# The number of the last client request processed by
the server (the serial field from the event). Valid
for all event types.
%b The number of the button that was pressed or
released. Valid only for ButtonPress and ButtonRe-
lease events.
%c The count field from the event. Valid only for
Expose events.
%d The detail field from the event. The %d is replaced
by a string identifying the detail. For Enter,
Leave, FocusIn, and FocusOut events, the string will
be one of the following:
NotifyAncestor NotifyNonlinearVirtual
NotifyDetailNone NotifyPointer
NotifyInferior NotifyPointerRoot
NotifyNonlinear NotifyVirtual
For events other than these, the substituted string
is undefined.
%f The focus field from the event (0 or 1). Valid only
for Enter and Leave events.
%h The height field from the event. Valid only for Con- |
figure and Expose events.
%k The keycode field from the event. Valid only for
KeyPress and KeyRelease events.
%m The mode field from the event. The substituted
string is one of NotifyNormal, NotifyGrab, NotifyUn-
grab, or NotifyWhileGrabbed. Valid only for Enter, |
FocusIn, FocusOut, and Leave events.
%o The override_redirect field from the event. Valid
only for Map, Reparent, and Configure events.
%p The place field from the event, substituted as one of
the strings PlaceOnTop or PlaceOnBottom. Valid only
for Circulate events.
%s The state field from the event. For ButtonPress,
ButtonRelease, Enter, KeyPress, KeyRelease, Leave,
and Motion events, a decimal string is substituted.
For Visibility, one of the strings VisibilityUnob-
scured, VisibilityPartiallyObscured, and Visibility-
FullyObscured is substituted.
%t The time field from the event. Valid only for events
that contain a time field.
%x The x field from the event. Valid only for events
containing an x field.
%y The y field from the event. Valid only for events
containing a y field.
%A Substitutes the ASCII character corresponding to the
event, or the empty string if the event doesn't cor-
respond to an ASCII character (e.g. the shift key was
pressed). XLookupString does all the work of trans-
lating from the event to an ASCII character. Valid
only for KeyPress and KeyRelease events.
%B The border_width field from the event. Valid only
for Configure events.
%E The send_event field from the event. Valid for all
event types.
%K The keysym corresponding to the event, substituted as
a textual string. Valid only for KeyPress and KeyRe-
lease events.
%N The keysym corresponding to the event, substituted as
a decimal number. Valid only for KeyPress and KeyRe-
lease events.
%R The root window identifier from the event. Valid
only for events containing a root field.
%S The subwindow window identifier from the event, for-
matted as a hexadecimal number. Valid only for
events containing a subwindow field.
%T The type field from the event. Valid for all event
types.
%W The path name of the window to which the event was
reported (the window field from the event). Valid
for all event types.
%X The x_root field from the event. If a virtual-root
window manager is being used then the substituted
value is the corresponding x-coordinate in the vir-
tual root. Valid only for ButtonPress, ButtonRe-
lease, KeyPress, KeyRelease, and Motion events.
%Y The y_root field from the event. If a virtual-root
window manager is being used then the substituted
value is the corresponding y-coordinate in the vir-
tual root. Valid only for ButtonPress, ButtonRe-
a proper Tcl list element. This means that it will be
surrounded with braces if it contains spaces, or special
characters such as $ and { may be preceded by backslashes.
This guarantees that the string will be passed through the
Tcl parser when the binding script is evaluated. Most
replacements are numbers or well-defined strings such as
Above; for these replacements no special formatting is
ever necessary. The most common case where reformatting
occurs is for the %A substitution. For example, if script
is
insert %A
and the character typed is an open square bracket, then
the script actually executed will be
insert \[
This will cause the insert to receive the original
replacement string (open square bracket) as its first
argument. If the extra backslash hadn't been added, Tcl
would not have been able to parse the script correctly.
MULTIPLE MATCHES
It is possible for several bindings to match a given X
event. If the bindings are associated with different
tag's, then each of the bindings will be executed, in
order. By default, a binding for the widget will be exe-
cuted first, followed by a class binding, a binding for
its toplevel, and an all binding. The bindtags command
may be used to change this order for a particular window
or to associate additional binding tags with the window.
The continue and break commands may be used inside a bind-
ing script to control the processing of matching scripts.
If continue is invoked, then the current binding script is
terminated but Tk will continue processing binding scripts
associated with other tag's. If the break command is
invoked within a binding script, then that script termi-
nates and no other scripts will be invoked for the event.
If more than one binding matches a particular event and |
they have the same tag, then the most specific binding is |
chosen and its script is evaluated. The following tests |
are applied, in order, to determine which of several |
matching sequences is more specific: (a) an event pattern |
that specifies a specific button or key is more specific |
than one that doesn't; (b) a longer sequence (in terms of |
number of events matched) is more specific than a shorter |
sequence; (c) if the modifiers specified in one pattern |
are a subset of the modifiers in another pattern, then the |
pattern with more modifiers is more specific. (d) a vir- |
tual event whose physical pattern matches the sequence is |
less specific than the same physical pattern that is not |
associated with a virtual event. (e) given a sequence |
If the matching sequences contain more than one event, |
then tests (c)-(e) are applied in order from the most |
recent event to the least recent event in the sequences. |
If these tests fail to determine a winner, then the most |
recently registered sequence is the winner. |
If there are two (or more) virtual events that are both |
triggered by the same sequence, and both of those virtual |
events are bound to the same window tag, then only one of |
the virtual events will be triggered, and it will be |
picked at random: |
event add <<Paste>> <Control-y> |
event add <<Paste>> <Button-2> |
event add <<Scroll>> <Button-2> |
bind Entry <<Paste>> {puts Paste} |
bind Entry <<Scroll>> {puts Scroll} |
If the user types Control-y, the <<Paste>> binding will be |
invoked, but if the user presses button 2 then one of |
either the <<Paste>> or the <<Scroll>> bindings will be |
invoked, but exactly which one gets invoked is undefined. |
If an X event does not match any of the existing bindings,
then the event is ignored. An unbound event is not con-
sidered to be an error.
MULTI-EVENT SEQUENCES AND IGNORED EVENTS
When a sequence specified in a bind command contains more
than one event pattern, then its script is executed when-
ever the recent events (leading up to and including the
current event) match the given sequence. This means, for
example, that if button 1 is clicked repeatedly the
sequence <Double-ButtonPress-1> will match each button
press but the first. If extraneous events that would pre-
vent a match occur in the middle of an event sequence then
the extraneous events are ignored unless they are KeyPress
or ButtonPress events. For example, <Double-
ButtonPress-1> will match a sequence of presses of button
1, even though there will be ButtonRelease events (and
possibly Motion events) between the ButtonPress events.
Furthermore, a KeyPress event may be preceded by any num-
ber of other KeyPress events for modifier keys without the
modifier keys preventing a match. For example, the event
sequence aB will match a press of the a key, a release of
the a key, a press of the Shift key, and a press of the b
key: the press of Shift is ignored because it is a modi-
fier key. Finally, if several Motion events occur in a
row, only the last one is used for purposes of matching
binding sequences.
If an error occurs in executing the script for a binding
then the bgerror mechanism is used to report the error.
The bgerror command will be executed at global level (out-
side the context of any Tcl procedure).
SEE ALSO
bgerror
KEYWORDS
form, manual