bind(n) Tk Built-In Commands 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 arbi-trary arbitrary
trary 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 wid-gets widgets
gets 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 follow- |
ing 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 com- |
bined with a virtual event to modify it. Bindings on a virtual event may be created before the vir- |
tual 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 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 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 speci-fied specified
fied in the binding. For example, if button 1 is pressed while the shift and control keys are down,
the pattern <Control-Button-1> will match the event, but <Mod1-Button-1> will not. If no modifiers
are specified, then any combination of modifiers may be present in the event.
Meta and M refer to whichever of the M1 through M5 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 substan-tial substantial
tial 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 Mac-intosh Macintosh
intosh 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 Win- |
dows platforms. We provide a little more detail on these events here. These include: |
Acti- |
vate | |
Deacti- |
vate | |
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. |
Mouse- |
Wheel | |
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. On Windows, the event is always routed to the window |
that currently has focus. 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 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. |
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.
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 alphanu-meric alphanumeric
meric 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 ButtonRe-lease ButtonRelease
lease events.
%c The count field from the event. Valid only for Expose events.
%d The detail field from the event. The %d is replaced by a string identifying the detail. For
Enter, Leave, FocusIn, and FocusOut events, the string will be one of the following:
NotifyAncestor NotifyNonlinearVirtual
NotifyDetailNone NotifyPointer
NotifyInferior NotifyPointerRoot
NotifyNonlinear NotifyVirtual
For 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.
%h The height field from the event. Valid for the Configure, ConfigureRequest, Create, Resiz- |
eRequest, and Expose events.
%i The window field from the event, represented as a hexadecimal integer.
%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, Noti-fyUngrab, NotifyUngrab,
fyUngrab, 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.
%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, ConfigureRequest, Create, Resiz- |
eRequest, 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 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 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.
%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 sub-stituted substituted
stituted value is the corresponding x-coordinate in the virtual root. Valid only for Button-Press, ButtonPress,
Press, ButtonRelease, KeyPress, KeyRelease, and Motion events.
%Y The y_root field from the event. If a virtual-root window manager is being used then the sub-stituted substituted
stituted value is the corresponding y-coordinate in the virtual root. Valid only for Button-Press, ButtonPress,
Press, 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 asso-ciate associate
ciate 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 spe-cific specific
cific 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 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 unde-fined. undefined.
fined.
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-But-
tonPress-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 bgerror mechanism is used to report
the error. The bgerror command will be executed at global level (outside the context of any Tcl pro-cedure). procedure).
cedure).
SEE ALSO
bgerror, keysyms
KEYWORDS
form, manual
Tk 8.0 bind(n)
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