bind(n) Tk (8.0) bind(n)
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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) 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 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.
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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 patterns, with optional white space between the
patterns. Each event pattern 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 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 syntax: |
<<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
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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 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 modifiers
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. 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.
Activate Enter Map
ButtonPress, Button Expose Motion
ButtonRelease FocusIn MouseWheel |
Circulate FocusOut Property
Colormap Gravity Reparent
Configure KeyPress, Key Unmap
Deactivate 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 |
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bind(n) Tk (8.0) bind(n)
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 appearance 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 |
useful 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 particular button will match; if no
button number is given, then an event on any button will
match. Note: giving a specific button number 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 button that is already
depressed when the matching event occurs. If a button
number is given then type may be omitted: if will default
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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 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
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 KeyPress. 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. 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
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bind(n) Tk (8.0) bind(n)
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 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 VisibilityUnobscured,
VisibilityPartiallyObscured, and
VisibilityFullyObscured 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.
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%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, ButtonRelease, KeyPress,
KeyRelease, and Motion events.
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%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, ButtonRelease, 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 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 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 processing binding scripts
associated with other tag's. If the break command 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 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; |
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(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 virtual 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 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 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
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 repeatedly 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
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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 bgerror 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
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