bind(n) Tk Built-In Commands bind(n)______________________________________________________________________________NAMEbind - Arrange for X events to invoke Tcl scripts
SYNOPSISbind tag
bind tag sequence
bind tag sequence script
bind tag sequence +script
_________________________________________________________________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 win‐
dow(s) identified by tag. If script is prefixed with a ``+'', then it
is appended to any existing binding for sequence; otherwise 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 speci‐
fied, 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 bind‐
tags 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.
If the tag is the name of a class of widgets, such as Button,
the binding applies to all widgets in 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 pat‐
terns, with optional white space between the patterns. Each event pat‐ │
tern may take one of three forms. In the simplest case it is a single
printing ASCII character, 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 pat‐
tern 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 vir‐ │
tual event. It has the following syntax: │
<<name>> │
The entire virtual event pattern is surrounded by double angle brack‐ │
ets. 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: Con‐
trol Mod2, M2 Shift Mod3, M3
Lock Mod4, M4 Button1, B1 Mod5, M5 But‐
ton2, B2 Meta, M Button3, B3 Alt Button4,
B4 Double Button5, B5 Triple Mod1, M1 Where
more than one value is listed, separated by commas, the values are
equivalent. Most of the modifiers have the obvious X meanings. For
example, Button1 requires that button 1 be depressed when the event
occurs. For a binding 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 specified in the bind‐
ing. 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 com‐
bination of modifiers may be present in the event.
Meta and M refer to whichever of the M1 through M5 modifiers is associ‐
ated 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 modi‐
fiers, 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 Dou‐
ble 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. The type field will also accept a couple non-
standard X event types that were added to better support the Macintosh
and Windows platforms. Below is a list of all the valid types; where
two names appear together, they are synonyms. Acti‐
vate Enter Map ButtonPress, But‐
ton Expose Motion ButtonRe‐ │
lease FocusIn MouseWheel Circulate Focu‐
sOut Property Colormap Gravity Reparent
Configure KeyPress, Key Unmap Deacti‐
vate KeyRelease Visibility Destroy Leave
Most of the above events have the same fields and behaviors as events │
in the X Windowing system. You can find more detailed descriptions of │
these events in any X window programming book. A couple of the events │
are extensions to the X event system to support features unique to the │
Macintosh and Windows platforms. We provide a little more detail on │
these events here. These include: │
Activate │
Deactivate │
These two events are sent to every sub-window of a toplevel when │
they change state. In addition to the focus Window, the Macintosh │
platform and Windows platforms have a notion of an active window │
(which often has but is not required to have the focus). On the │
Macintosh, widgets in the active window have a different appear‐ │
ance than widgets in deactive windows. The Activate event is sent │
to all the sub-windows in a toplevel when it changes from being │
deactive to active. Likewise, the Deactive event is sent when the │
window's state changes from active to deactive. There are no use‐ │
ful percent substitutions you would make when binding to these │
events. │
MouseWheel │
Some mice on the Windows platform support a mouse wheel which is │
used for scrolling documents without using the scrollbars. By │
rolling the wheel, the system will generate MouseWheel events that │
the application can use to scroll. Like Key events the event is │
always routed to the window that currently has focus. When the │
event is received you can use the %D substitution to get the delta │
field for the event which is a integer value of motion that the │
mouse wheel has moved. The smallest value for which the system │
will report is defined by the OS. On Windows 95 & 98 machines │
this value is at least 120 before it is reported. However, higher │
resolution devices may be available in the future. The sign of │
the value determines which direction your widget should scroll. │
Positive values should scroll up and negative values should scroll │
down.
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 partic‐
ular button will match; if no button number is given, then an event on
any button will match. Note: giving a specific button number is dif‐
ferent 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 button 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 speci‐
fied in the form of an X keysym. Keysyms are textual specifications
for particular keys on the keyboard; 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 neces‐
sary, 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 KeyPress. For exam‐
ple, <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. Command 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 generated by replacing each %,
and the character following it, with information from the current
event. The replacement 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
undefined.
%% 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.
%a The above field from the event, formatted as a hexadecimal number.
Valid only for Configure events.
%b The number of the button that was pressed or released. Valid only
for ButtonPress and ButtonRelease 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 NotifyDetail‐
None NotifyPointer NotifyInferior NotifyPointer‐
Root 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 for the Configure 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, NotifyUngrab, 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 Visi‐
bilityUnobscured, VisibilityPartiallyObscured, and VisibilityFul‐
lyObscured is substituted.
%t The time field from the event. Valid only for events that contain
a time field.
%w The width field from the event. Valid only for Configure and │
Expose events.
%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 correspond to an ASCII character
(e.g. the shift key was pressed). XLookupString does all the work
of translating 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. │
%D │
This reports the delta value of a MouseWheel event. The delta │
value represents the rotation units the mouse wheel has been │
moved. On Windows 95 & 98 systems the smallest value for the │
delta is 120. Future systems may support higher resolution values │
for the delta. The sign of the value represents the direction the │
mouse wheel was scrolled.
%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 KeyRelease events.
%N The keysym corresponding to the event, substituted as a decimal
number. Valid only for KeyPress and KeyRelease 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, formatted 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 virtual root. Valid only for ButtonPress, But‐
tonRelease, 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 virtual root. Valid only for ButtonPress, But‐
tonRelease, KeyPress, KeyRelease, and Motion events.
The replacement string for a %-replacement is formatted as 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 replace‐
ments 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 executed 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 binding script to
control the processing of matching scripts. If continue is invoked,
then the current binding script is terminated but Tk will continue pro‐
cessing binding scripts associated with other tag's. If the break com‐
mand is invoked within a binding script, then that script terminates
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 pat‐ │
tern 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 pat‐ │
tern, then the pattern with more modifiers is more specific. (d) a │
virtual event whose physical pattern matches the sequence is less spe‐ │
cific than the same physical pattern that is not associated with a vir‐ │
tual event. (e) given a sequence that matches two or more virtual │
events, one of the virtual events will be chosen, but the order is │
undefined. │
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 win‐ │
ner, 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 considered 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 whenever 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 repeat‐
edly the sequence <Double-ButtonPress-1> will match each button press
but the first. If extraneous events that would prevent 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 number 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 modifier key. Finally, if several
Motion events occur in a row, only the last one is used for purposes of
matching binding sequences.
ERRORS
If an error occurs in executing the script for a binding then the bger‐
ror mechanism is used to report the error. The bgerror command will be
executed at global level (outside the context of any Tcl procedure).
SEE ALSO
bgerror
KEYWORDS
form, manual
Tk 8.0 bind(n)
