Tk Built-In Commands bind(1T)
NAME
bind - Arrange for X events to invoke Tcl scripts
SYNOPSIS
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 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 argu-
ment 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:
]o If a tag is the name of an internal window the binding
applies to that window.
]o If the tag is the name of a toplevel window the binding
applies to the toplevel window and all its internal win-
dows.
]o If the tag is the name of a class of widgets, such as
Button, the binding applies to all widgets in that class;
]o If tag has the value all, the binding applies to all win-
dows in the application.
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Tk Built-In Commands bind(1T)
EVENT PATERNS
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 ASCI 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 syn-
tax:
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) iden-
tifying 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:
<>
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.
Some widgets (e.g. menu and text) issue virtual events when
their internal state is updated in some ways. Please see
the manual page for each widget for details.
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 Quadruple
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
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Tk Built-In Commands bind(1T)
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 will match the event, but 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
MetaR and MetaL). 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 AltL and AltR).
The Double, Triple and Quadruple modifiers are a convenience
for specifying double mouse clicks and other repeated
events. They cause a particular event pattern to be repeated
2, 3 or 4 times, and also place a time and space requirement
on the sequence: for a sequence of events to match a Double,
Triple or Quadruple pattern, all of the events must occur
close together in time and without substantial mouse motion
in between. For example, is equivalent to
with the extra time and space require-
ment.
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 Destroy Map
ButtonPress, Button Enter MapRequest
ButtonRelease Expose Motion
Circulate FocusIn MouseWheel
CirculateRequest FocusOut Property
Colormap Gravity Reparent
Configure KeyPress, Key ResizeRequest
ConfigureRequest KeyRelease Unmap
Create Leave Visibility
Deactivate
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
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programming book. A couple of the events are extensions to
the X event system to support features unique to the Macin-
tosh 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 plat-
forms 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 dif-
ferent 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 bind-
ing 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 gen-
erate MouseWheel events that the application can use to
scroll. On Windows, the event is always routed to the
window that currently has focus (like Key events.) On
Mac OS X, the event is routed to the window under the
pointer. When the event is received you can use the %D
substitution to get the delta field for the event,
which is a integer value describing how 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. On Mac OS X, the value is not
scaled by 120, but a value of 1 corresponds to roughly
one text line. The sign of the value determines which
direction your widget should scroll. Positive values
should scroll up and negative values should scroll
down.
KeyPress, KeyRelease
The KeyPress and KeyRelease events are generated when-
ever a key is pressed or released. KeyPress and
KeyRelease events are sent to the window which
currently has the keyboard focus.
ButtonPress, ButtonRelease, Motion
The ButtonPress and ButtonRelease events are generated
when the user presses or releases a mouse button.
Motion events are generated whenever the pointer is
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Tk Built-In Commands bind(1T)
moved. ButtonPress, ButtonRelease, and Motion events
are normally sent to the window containing the pointer.
When a mouse button is pressed, the window containing
the pointer automatically obtains a temporary pointer
grab. Subsequent ButtonPress, ButtonRelease, and
Motion events will be sent to that window, regardless
of which window contains the pointer, until all buttons
have been released.
Configure
A Configure event is sent to a window whenever its
size, position, or border width changes, and sometimes
when it has changed position in the stacking order.
Map, Unmap
The Map and Unmap events are generated whenever the
mapping state of a window changes.
Windows are created in the unmapped state. Top-level
windows become mapped when they transition to the nor-
mal state, and are unmapped in the withdrawn and iconic
states. Other windows become mapped when they are
placed under control of a geometry manager (for example
pack or grid).
A window is viewable only if it and all of its ances-
tors are mapped. Note that geometry managers typically
do not map their children until they have been mapped
themselves, and unmap all children when they become
unmapped; hence in Tk Map and Unmap events indicate
whether or not a window is viewable.
Visibility
A window is said to be obscured when another window
above it in the stacking order fully or partially over-
laps it. Visibility events are generated whenever a
window's obscurity state changes; the state field (%s)
specifies the new state.
Expose
An Expose event is generated whenever all or part of a
window should be redrawn (for example, when a window is
first mapped or if it becomes unobscured). It is nor-
mally not necessary for client applications to handle
Expose events, since Tk handles them internally.
Destroy
A Destroy event is delivered to a window when it is
destroyed.
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When the Destroy event is delivered to a widget, it is
in a ``half-dead'' state: the widget still exists, but
most operations on it will fail.
FocusIn, FocusOut
The FocusIn and FocusOut events are generated whenever
the keyboard focus changes. A FocusOut event is sent
to the old focus window, and a FocusIn event is sent to
the new one.
In addition, if the old and new focus windows do not
share a common parent, ``virtual crossing'' focus
events are sent to the intermediate windows in the
hierarchy. Thus a FocusIn event indicates that the
target window or one of its descendants has acquired
the focus, and a FocusOut event indicates that the
focus has been changed to a window outside the target
window's hierarchy.
The keyboard focus may be changed explicitly by a call
to focus, or implicitly by the window manager.
Enter, Leave
An Enter event is sent to a window when the pointer
enters that window, and a Leave event is sent when the
pointer leaves it.
If there is a pointer grab in effect, Enter and Leave
events are only delivered to the window owning the
grab.
In addition, when the pointer moves between two win-
dows, Enter and Leave ``virtual crossing'' events are
sent to intermediate windows in the hierarchy in the
same manner as for FocusIn and FocusOut events.
Property
A Property event is sent to a window whenever an X pro-
perty belonging to that window is changed or deleted.
Property events are not normally delivered to Tk appli-
cations as they are handled by the Tk core.
Colormap
A Colormap event is generated whenever the colormap
associated with a window has been changed, installed,
or uninstalled.
Widgets may be assigned a private colormap by specify-
ing a -colormap option; the window manager is responsi-
ble for installing and uninstalling colormaps as neces-
sary.
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Tk Built-In Commands bind(1T)
Note that Tk provides no useful details for this event
type.
Create
MapRequest, CirculateRequest, ResizeRequest, ConfigureRequest,
These events are not normally delivered to Tk applica-
tions. They are included for completeness, to make it
possible to write X11 window managers in Tk. (These
events are only delivered when a client has selected
SubstructureRedirectMask on a window; the Tk core does
not use this mask.)
Gravity, Reparent, Circulate
The events Gravity and Reparent are not normally
delivered to Tk applications. They are included for
completeness.
A Circulate event indicates that the window has moved
to the top or to the bottom of the stacking order as a
result of an XCirculateSubwindows protocol request.
Note that the stacking order may be changed for other
reasons which do not generate a Circulate event, and
that Tk does not use XCirculateSubwindows() internally.
This event type is included only for completeness;
there is no reliable way to track changes to a window's
position in the stacking order.
EVENT DETAILS
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
to ButtonPress. For example, the specifier <1> is
equivalent to .
If the event type is KeyPress or KeyRelease, then detail may
be specified in the form of an X keysym. Keysyms are tex-
tual specifications for particular keys on the keyboard;
they include all the alphanumeric ASCI characters (e.g.
``a'' is the keysym for the ASCI character ``a''), plus
descriptions for non-alphanumeric characters (``comma'' is
the keysym for the comma character), plus descriptions for
all the non-ASCI keys on the keyboard (``ShiftL'' is the
keysym for the left shift key, and ``F1'' is the keysym for
the F1 function key, if it exists). The complete list of
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Tk Built-In Commands bind(1T)
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 example, is
equivalent to .
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 com-
mand 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 hexade-
cimal number. Valid only for Configure events. Indi-
cates the sibling window immediately below the receiv-
ing window in the stacking order, or 0 if the receiving
window is at the bottom.
%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. Indicates that there are count pending Expose
events which have not yet been delivered to the window.
%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
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Tk Built-In Commands bind(1T)
NotifyNonlinear NotifyVirtual
For ConfigureRequest events, the string will be one of:
Above Opposite
Below None
BottomIf TopIf
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. 1 if the receiving window
is the focus window or a descendant of the focus win-
dow, 0 otherwise.
%h The height field from the event. Valid for the Config-
ure, ConfigureRequest, Create, ResizeRequest, and
Expose events. Indicates the new or requested height
of the window.
%i The window field from the event, represented as a hexa-
decimal integer. Valid for all event types.
%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 overrideredirect 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 and CirculateRequest events.
%s The state field from the event. For ButtonPress, But-
tonRelease, Enter, KeyPress, KeyRelease, Leave, and
Motion events, a decimal string is substituted. For
Visibility, one of the strings VisibilityUnobscured,
VisibilityPartiallyObscured, and VisibilityFullyOb-
scured is substituted. For Property events, substi-
tuted with either the string NewValue (indicating that
the property has been created or modified) or Delete
(indicating that the property has been removed).
%t The time field from the event. This is the X server
timestamp (typically the time since the last server
reset) in milliseconds, when the event occurred. Valid
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Tk Built-In Commands bind(1T)
for most events.
%w The width field from the event. Indicates the new or
requested width of the window. Valid only for Config-
ure, ConfigureRequest, Create, ResizeRequest, and
Expose events.
%x, %y
The x and y fields from the event. For ButtonPress,
ButtonRelease, Motion, KeyPress, KeyRelease, and
MouseWheel events, %x and %y indicate the position of
the mouse pointer relative to the receiving window.
For Enter and Leave events, the position where the
mouse pointer crossed the window, relative to the
receiving window. For Configure and Create requests,
the x and y coordinates of the window relative to its
parent window.
%A Substitutes the UNICODE character corresponding to the
event, or the empty string if the event doesn't
correspond to a UNICODE character (e.g. the shift key
was pressed). XmbLookupString (or XLookupString when
input method support is turned off) does all the work
of translating from the event to a UNICODE character.
Valid only for KeyPress and KeyRelease events.
%B The borderwidth field from the event. Valid only for
Configure, ConfigureRequest, and Create 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 sendevent field from the event. Valid for all
event types. 0 indicates that this is a ``normal''
event, 1 indicates that it is a ``synthetic'' event
generated by SendEvent.
%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.
%P The name of the property being updated or deleted
(which may be converted to an XAtom using winfo atom.)
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Tk Built-In Commands bind(1T)
Valid only for Property 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, format-
ted 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 xroot 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. Same meaning as %x,
except relative to the (virtual) root window.
%Y The yroot 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. Same meaning as %y,
except relative to the (virtual) root window.
The replacement string for a %-replacement is formatted as a
proper Tcl list element. This means that it will be sur-
rounded with braces if it contains spaces, or special char-
acters 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 replace-
ments are numbers or well-defined strings such as Above;
for these replacements no special formatting is ever neces-
sary. 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 replace-
ment 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,
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Tk Built-In Commands bind(1T)
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 addi-
tional 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 ter-
minated 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;
(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 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 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 <>
event add <>
event add <>
bind Entry <> {puts Paste}
bind Entry <> {puts Scroll}
If the user types Control-y, the <> binding will be
invoked, but if the user presses button 2 then one of either
the <> or the <> bindings will be invoked,
but exactly which one gets invoked is undefined.
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Tk Built-In Commands bind(1T)
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 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
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, 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.
ERORS
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).
EXAMPLES
Arrange for a string describing the motion of the mouse to
be printed out when the mouse is double-clicked:
bind . {
puts "hi from (%x,%y)"
}
A little GUI that displays what the keysym name of the last
key pressed is:
set keysym "Press any key"
pack [label .l -textvariable keysym -padx 2m -pady 1m]
bind . {
set keysym "You pressed %K"
}
SEE ALSO
bgerror(1T), bindtags(1T), event(1T), focus(1T), grab(1T),
keysyms(1T)
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KEYWORDS
binding, event
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWTk
Interface Stability Uncommitted
NOTES
Source for Tk is available on http:/opensolaris.org.
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