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'\" Copyright (c) 1998 by Scriptics Corporation.

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'\" RCS: @(#) $Id: bind.n,v 1.1.1.1 2002-01-16 10:25:48 markom Exp $

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.so man.macros

.TH bind n 8.0 Tk "Tk Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

bind \- Arrange for X events to invoke Tcl scripts

.SH SYNOPSIS

\fBbind\fI tag\fR

.sp

\fBbind\fI tag sequence\fR

.sp

\fBbind\fI tag sequence script\fR

.sp

\fBbind\fI tag sequence \fB+\fIscript\fR

.BE

.SH INTRODUCTION

.PP

The \fBbind\fR command associates Tcl scripts with X events.

If all three arguments are specified, \fBbind\fR will

arrange for \fIscript\fR (a Tcl script) to be evaluated whenever

the event(s) given by \fIsequence\fR occur in the window(s)

identified by \fItag\fR.

If \fIscript\fR is prefixed with a ``+'', then it is appended to

any existing binding for \fIsequence\fR;  otherwise \fIscript\fR replaces

any existing binding.

If \fIscript\fR is an empty string then the current binding for

\fIsequence\fR is destroyed, leaving \fIsequence\fR unbound.

In all of the cases where a \fIscript\fR argument is provided,

\fBbind\fR returns an empty string.

.PP

If \fIsequence\fR is specified without a \fIscript\fR, then the

script currently bound to \fIsequence\fR is returned, or

an empty string is returned if there is no binding for \fIsequence\fR.

If neither \fIsequence\fR nor \fIscript\fR is specified, then the

return value is a list whose elements are all the sequences

for which there exist bindings for \fItag\fR.

.PP

The \fItag\fR argument determines which window(s) the binding applies to.

If \fItag\fR begins with a dot, as in \fB.a.b.c\fR, 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 \fBbindtags\fR command may be used to assign an

arbitrary set of binding tags to a window, the default binding

tags provide the following behavior:

.IP

If a tag is the name of an internal window the binding applies

to that window.

.IP

If the tag is the name of a toplevel window the binding applies

to the toplevel window and all its internal windows.

.IP

If the tag is the name of a class of widgets, such as \fBButton\fR,

the binding applies to all widgets in that class;

.IP

If \fItag\fR has the value \fBall\fR,

the binding applies to all windows in the application.

.SH "EVENT PATTERNS"

.PP

The \fIsequence\fR argument specifies a sequence of one or more

event patterns, with optional white space between the patterns.  Each

.VS

event pattern may

take one of three forms.  In the simplest case it is a single

.VE

printing ASCII character, such as \fBa\fR or \fB[\fR.  The character

may not be a space character or the character \fB<\fR.  This form of

pattern matches a \fBKeyPress\fR event for the particular

character.  The second form of pattern is longer but more general.

It has the following syntax:

.CS

\fB<\fImodifier-modifier-type-detail\fB>\fR

.CE

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 (\fIdetail\fR) identifying

a particular button or keysym.  Any of the fields may be omitted,

as long as at least one of \fItype\fR and \fIdetail\fR is present.

The fields must be separated by white space or dashes.

.VS

.PP

The third form of pattern is used to specify a user-defined, named virtual

event.  It has the following syntax:

.CS

\fB<<\fIname\fB>>\fR

.CE

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 \fBShift\fR or \fBControl\fR, 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.

.VE

.SH "MODIFIERS"

.PP

Modifiers consist of any of the following values:

.DS

.ta 6c

\fBControl\fR   \fBMod2, M2\fR

\fBShift\fR     \fBMod3, M3\fR

\fBLock\fR      \fBMod4, M4\fR

\fBButton1, B1\fR       \fBMod5, M5\fR

\fBButton2, B2\fR       \fBMeta, M\fR

\fBButton3, B3\fR       \fBAlt\fR

\fBButton4, B4\fR       \fBDouble\fR

\fBButton5, B5\fR       \fBTriple\fR

\fBMod1, M1\fR

.DE

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, \fBButton1\fR 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 \fB\fR will match

the event, but \fB\fR will not.

If no modifiers are specified, then any combination of modifiers may

be present in the event.

.PP

\fBMeta\fR and \fBM\fR refer to whichever of the

\fBM1\fR through \fBM5\fR modifiers is associated with the meta

key(s) on the keyboard (keysyms \fBMeta_R\fR and \fBMeta_L\fR).

If there are no meta keys, or if they are not associated with any

modifiers, then \fBMeta\fR and \fBM\fR will not match any events.

Similarly, the \fBAlt\fR modifier refers to whichever modifier

is associated with the alt key(s) on the keyboard (keysyms

\fBAlt_L\fR and \fBAlt_R\fR).

.PP

The \fBDouble\fR and \fBTriple\fR 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 \fBDouble\fR

or \fBTriple\fR pattern, all of the events must occur close together

in time and without substantial mouse motion in between.

For example, \fB\fR

is equivalent to \fB\fR with the extra

time and space requirement.

.SH "EVENT TYPES"

.PP

The \fItype\fR field may be any of the standard X event types, with a

few extra abbreviations.  The \fItype\fR 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.

.DS C

.ta 5c 10c

\fBActivate     Enter   Map

ButtonPress, Button     Expose  Motion

.VS

ButtonRelease   FocusIn MouseWheel

.VE

Circulate       FocusOut        Property

Colormap        Gravity Reparent

Configure       KeyPress, Key   Unmap

Deactivate      KeyRelease      Visibility

Destroy Leave\fR

.DE

.PP

.VS

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:

.IP \fBActivate\fR 5

.IP \fBDeactivate\fR 5

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 \fBActivate\fR event is sent to all the

sub-windows in a toplevel when it changes from being deactive to

active.  Likewise, the \fBDeactive\fR 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.

.IP \fBMouseWheel\fR 5

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 \fBMouseWheel\fR events that the

application can use to scroll.  Like \fBKey\fR events the event is

always routed to the window that currently has focus. When the event

is received you can use the \fB%D\fR substitution to get the

\fIdelta\fR 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.

.VE

.PP

The last part of a long event specification is \fIdetail\fR.  In the

case of a \fBButtonPress\fR or \fBButtonRelease\fR 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 \fItype\fR may be omitted:  if will default

to \fBButtonPress\fR.  For example, the specifier \fB<1>\fR

is equivalent to \fB\fR.

.PP

If the event type is \fBKeyPress\fR or \fBKeyRelease\fR, then

\fIdetail\fR 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 \fB%K\fR notation described below

to print out the keysym name for a particular key.

If a keysym \fIdetail\fR is given, then the

\fItype\fR field may be omitted;  it will default to \fBKeyPress\fR.

For example, \fB\fR is equivalent to

\fB\fR.

.SH "BINDING SCRIPTS AND SUBSTITUTIONS"

.PP

The \fIscript\fR argument to \fBbind\fR is a Tcl script,

which will be executed whenever the given event sequence occurs.

\fICommand\fR will be executed in the same interpreter that the

\fBbind\fR command was executed in, and it will run at global

level (only global variables will be accessible).

If \fIscript\fR contains

any \fB%\fR characters, then the script will not be

executed directly.  Instead, a new script will be

generated by replacing each \fB%\fR, and the character following

it, with information from the current event.  The replacement

depends on the character following the \fB%\fR, 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.

.IP \fB%%\fR 5

Replaced with a single percent.

.IP \fB%#\fR 5

The number of the last client request processed by the server

(the \fIserial\fR field from the event).  Valid for all event

types.

.IP \fB%a\fR 5

The \fIabove\fR field from the event,

formatted as a hexadecimal number.

Valid only for \fBConfigure\fR events.

.IP \fB%b\fR 5

The number of the button that was pressed or released.  Valid only

for \fBButtonPress\fR and \fBButtonRelease\fR events.

.IP \fB%c\fR 5

The \fIcount\fR field from the event.  Valid only for \fBExpose\fR events.

.IP \fB%d\fR 5

The \fIdetail\fR field from the event.  The \fB%d\fR is replaced by

a string identifying the detail.  For \fBEnter\fR,

\fBLeave\fR, \fBFocusIn\fR, and \fBFocusOut\fR events,

the string will be one of the following:

.RS

.DS

.ta 6c

\fBNotifyAncestor       NotifyNonlinearVirtual

NotifyDetailNone        NotifyPointer

NotifyInferior  NotifyPointerRoot

NotifyNonlinear NotifyVirtual\fR

.DE

For events other than these, the substituted string is undefined.

.RE

.IP \fB%f\fR 5

The \fIfocus\fR field from the event (\fB0\fR or \fB1\fR).  Valid only

for \fBEnter\fR and \fBLeave\fR events.

.IP \fB%h\fR 5

.VS

The \fIheight\fR field from the event.  Valid for the \fBConfigure\fR and

\fBExpose\fR events.

.VE

.IP \fB%k\fR 5

The \fIkeycode\fR field from the event.  Valid only for \fBKeyPress\fR

and \fBKeyRelease\fR events.

.IP \fB%m\fR 5

The \fImode\fR field from the event.  The substituted string is one of

\fBNotifyNormal\fR, \fBNotifyGrab\fR, \fBNotifyUngrab\fR, or

.VS

\fBNotifyWhileGrabbed\fR.  Valid only for \fBEnter\fR,

\fBFocusIn\fR, \fBFocusOut\fR, and \fBLeave\fR events.

.VE

.IP \fB%o\fR 5

The \fIoverride_redirect\fR field from the event.  Valid only for

\fBMap\fR, \fBReparent\fR, and \fBConfigure\fR events.

.IP \fB%p\fR 5

The \fIplace\fR field from the event, substituted as one of the

strings \fBPlaceOnTop\fR or \fBPlaceOnBottom\fR.  Valid only

for \fBCirculate\fR events.

.IP \fB%s\fR 5

The \fIstate\fR field from the event.  For \fBButtonPress\fR,

\fBButtonRelease\fR, \fBEnter\fR, \fBKeyPress\fR, \fBKeyRelease\fR,

\fBLeave\fR, and \fBMotion\fR events, a decimal string

is substituted.  For \fBVisibility\fR, one of the strings

\fBVisibilityUnobscured\fR, \fBVisibilityPartiallyObscured\fR,

and \fBVisibilityFullyObscured\fR is substituted.

.IP \fB%t\fR 5

The \fItime\fR field from the event.  Valid only for events that

contain a \fItime\fR field.

.IP \fB%w\fR 5

The \fIwidth\fR field from the event.  Valid only for

.VS

\fBConfigure\fR and \fBExpose\fR events.

.VE

.IP \fB%x\fR 5

The \fIx\fR field from the event.  Valid only for events containing

an \fIx\fR field.

.IP \fB%y\fR 5

The \fIy\fR field from the event.  Valid only for events containing

a \fIy\fR field.

.IP \fB%A\fR 5

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).  \fBXLookupString\fR does all the

work of translating from the event to an ASCII character.

Valid only for \fBKeyPress\fR and \fBKeyRelease\fR events.

.IP \fB%B\fR 5

The \fIborder_width\fR field from the event.  Valid only for

\fBConfigure\fR events.

.VS

.IP \fB%D\fR 5

This reports the \fIdelta\fR value of a \fBMouseWheel\fR event.  The

\fIdelta\fR 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.

.VE

.IP \fB%E\fR 5

The \fIsend_event\fR field from the event.  Valid for all event types.

.IP \fB%K\fR 5

The keysym corresponding to the event, substituted as a textual

string.  Valid only for \fBKeyPress\fR and \fBKeyRelease\fR events.

.IP \fB%N\fR 5

The keysym corresponding to the event, substituted as a decimal

number.  Valid only for \fBKeyPress\fR and \fBKeyRelease\fR events.

.IP \fB%R\fR 5

The \fIroot\fR window identifier from the event.  Valid only for

events containing a \fIroot\fR field.

.IP \fB%S\fR 5

The \fIsubwindow\fR window identifier from the event,

formatted as a hexadecimal number.

Valid only for events containing a \fIsubwindow\fR field.

.IP \fB%T\fR 5

The \fItype\fR field from the event.  Valid for all event types.

.IP \fB%W\fR 5

The path name of the window to which the event was reported (the

\fIwindow\fR field from the event).  Valid for all event types.

.IP \fB%X\fR 5

The \fIx_root\fR 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

\fBButtonPress\fR, \fBButtonRelease\fR, \fBKeyPress\fR, \fBKeyRelease\fR,

and \fBMotion\fR events.

.IP \fB%Y\fR 5

The \fIy_root\fR 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

\fBButtonPress\fR, \fBButtonRelease\fR, \fBKeyPress\fR, \fBKeyRelease\fR,

and \fBMotion\fR events.

.LP

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 \fB$\fR and

\fB{\fR 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 \fBAbove\fR;  for these replacements no special formatting

is ever necessary.

The most common case where reformatting occurs is for the \fB%A\fR

substitution.  For example, if \fIscript\fR is

.CS

\fBinsert\0%A\fR

.CE

and the character typed is an open square bracket, then the script

actually executed will be

.CS

\fBinsert\0\e[\fR

.CE

This will cause the \fBinsert\fR 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.

.SH MULTIPLE MATCHES

.PP

It is possible for several bindings to match a given X event.

If the bindings are associated with different \fItag\fR'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 \fBall\fR binding.

The \fBbindtags\fR command may be used to change this order for

a particular window or to associate additional binding tags with

the window.

.PP

The \fBcontinue\fR and \fBbreak\fR commands may be used inside a

binding script to control the processing of matching scripts.

If \fBcontinue\fR is invoked, then the current binding script

is terminated but Tk will continue processing binding scripts

associated with other \fItag\fR's.

If the \fBbreak\fR command is invoked within a binding script,

then that script terminates and no other scripts will be invoked

for the event.

.VS

.PP

If more than one binding matches a particular event and they

have the same \fItag\fR, 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.

.VS

(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.

.PP

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.

.PP

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:

.CS

event add <> 

event add <> 

event add <> 

bind Entry <> {puts Paste}

bind Entry <> {puts Scroll}

.CE

If the user types Control-y, the \fB<>\fR binding

will be invoked, but if the user presses button 2 then one of

either the \fB<>\fR or the \fB<>\fR bindings will

be invoked, but exactly which one gets invoked is undefined.

.VE

.PP

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.

.SH "MULTI-EVENT SEQUENCES AND IGNORED EVENTS"

.PP

When a \fIsequence\fR specified in a \fBbind\fR 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 \fB\fR 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 \fBKeyPress\fR or \fBButtonPress\fR events.

For example, \fB\fR will match a sequence of

presses of button 1, even though there will be \fBButtonRelease\fR

events (and possibly \fBMotion\fR events) between the

\fBButtonPress\fR events.

Furthermore, a \fBKeyPress\fR event may be preceded by any number

of other \fBKeyPress\fR events for modifier keys without the

modifier keys preventing a match.

For example, the event sequence \fBaB\fR will match a press of the

\fBa\fR key, a release of the \fBa\fR key, a press of the \fBShift\fR

key, and a press of the \fBb\fR key:  the press of \fBShift\fR is

ignored because it is a modifier key.

Finally, if several \fBMotion\fR events occur in a row, only

the last one is used for purposes of matching binding sequences.

.SH ERRORS

.PP

If an error occurs in executing the script for a binding then the

\fBbgerror\fR mechanism is used to report the error.

The \fBbgerror\fR command will be executed at global level

(outside the context of any Tcl procedure).

.SH "SEE ALSO"

bgerror

.SH KEYWORDS

form, manual