bind - Arrange for X events to invoke Tcl scripts
bind tag ?
sequence? ?
+??
script?
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.
- •
- 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.
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:
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 consist of any of the following values:
Control Mod1, M1, Command
Alt Mod2, M2, Option
Shift Mod3, M3
Lock Mod4, M4
Extended Mod5, M5
Button1, B1 Meta, M
Button2, B2 Double
Button3, B3 Triple
Button4, B4 Quadruple
Button5, B5
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,
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,
<Double-Button-1> is equivalent
to
<Button-1><Button-1> with the extra time and space
requirement.
The
Command and
Option modifiers are equivalents of
Mod1
resp.
Mod2, they correspond to Macintosh-specific modifier keys.
The
Extended modifier is, at present, specific to Windows. It appears on
events that are associated with the keys on the “extended
keyboard”. On a US keyboard, the extended keys include the
Alt
and
Control keys at the right of the keyboard, the cursor keys in the
cluster to the left of the numeric pad, the
NumLock key, the
Break key, the
PrintScreen key, and the
/ and
Enter keys in the numeric keypad.
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 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
- Many contemporary mice 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 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. 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 whenever 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 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
normal 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 ancestors 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 overlaps 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 normally 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.
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 windows,
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 property
belonging to that window is changed or deleted. Property events are
not normally delivered to Tk applications 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 specifying a
-colormap
option; the window manager is responsible for installing and uninstalling
colormaps as necessary.
Note that Tk provides no useful details for this event type.
- MapRequest, CirculateRequest, ResizeRequest,
ConfigureRequest, Create
- These events are not normally delivered to Tk applications. 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.
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
<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 (e.g.
“Shift_L” 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 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>.
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. Indicates the sibling window
immediately below the receiving 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 or user_data 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
ConfigureRequest events, the string will be one of:
Above Opposite
Below None
BottomIf TopIf
For virtual events, the string will be whatever value is stored in the
user_data field when the event was created (typically with
event
generate), or the empty string if the field is NULL. Virtual events
corresponding to key sequence presses (see
event add for
details) set the
user_data to NULL. 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 window, 0
otherwise.
- %h
- The height field from the event. Valid for the Configure,
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 hexadecimal
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 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
and CirculateRequest 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. For Property events, substituted 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 for most events.
- %w
- The width field from the event. Indicates the new or requested
width of the window. Valid only for Configure,
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 does not 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 border_width 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 send_event 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.) 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, 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, %Y
- The x_root and y_root fields from the event. If a
virtual-root window manager is being used then the substituted values are
the corresponding x-coordinate and y-coordinate in the virtual root. Valid
only for ButtonPress, ButtonRelease, KeyPress,
KeyRelease, and Motion events. Same meaning as %x and
%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 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
and the character typed is an open square bracket, then the script actually
executed will be
This will cause the
insert to receive the original replacement string
(open square bracket) as its first argument. If the extra backslash had not
been added, Tcl would not have been able to parse the script correctly.
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 does not;
- (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
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.
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
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.
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).
Arrange for a string describing the motion of the mouse to be printed out when
the mouse is double-clicked:
bind . <Double-1> {
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 . <Key> {
set keysym "You pressed %K"
}
bgerror(n), bindtags(n), event(n), focus(n), grab(n), keysyms(n)
binding, event