NAME
       bind - Arrange for X events to invoke Tcl scripts

SYNOPSIS
       bind tag

       bind tag sequence

       bind tag sequence script

       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)  identi-
       fied  by tag.  If script is prefixed with a ``+'', then it
       is appended to any existing binding for sequence;   other-
       wise  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.


EVENT PATTERNS
       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 ASCII charac-
       ter, 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 syn-
       tax:
              <<name>>
       The entire virtual event pattern is surrounded  by  double
       angle  brackets.   Inside  the angle brackets is the user-
       defined name of the virtual  event.   Modifiers,  such  as
       Shift or Control, may not be combined with a virtual event
       to modify it.  Bindings on a virtual event may be  created
       before the virtual event is defined, and if the definition
       of a virtual event changes dynamically, all windows  bound
       to  that virtual event will respond immediately to the new
       definition.

MODIFIERS
       Modifiers consist of any of the following values:

              Control                 Mod2, M2
              Shift                   Mod3, M3
              Lock                    Mod4, M4
              Button1, B1             Mod5, M5
              Button2, B2             Meta, M
              Button3, B3             Alt
              Button4, B4             Double
              Button5, B5             Triple
              Mod1, M1

       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  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-But-
       ton-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 modi-
       fiers is associated with the meta key(s) on  the  keyboard
       (keysyms  Meta_R  and Meta_L).  If there are no meta keys,
       or if they are not associated  with  any  modifiers,  then
       Meta  and M will not match any events.  Similarly, the Alt
       modifier refers to whichever modifier is  associated  with
       the  alt key(s) on the keyboard (keysyms Alt_L and Alt_R).

       The Double and Triple  modifiers  are  a  convenience  for
       specifying  double mouse clicks and other repeated events.
       They cause a particular event pattern to be repeated 2  or
       3  times,  and  also place a time and space requirement on
       the sequence:  for a sequence of events to match a  Double
       or  Triple  pattern,  all  of  the events must occur close
       together in time and without substantial mouse  motion  in
       between.   For example, <Double-Button-1> is equivalent to
       <Button-1><Button-1>  with  the  extra  time   and   space
       requirement.


EVENT TYPES
       The  type  field may be any of the standard X event types,
       with a few extra abbreviations.  The type field will  also
       accept a couple non-standard X event types that were added
       to better support the  Macintosh  and  Windows  platforms.
       Below  is  a  list of all the valid types; where two names
       appear together, they are synonyms.

              Activate            Enter              Map
              ButtonPress, Button Expose             Motion
              ButtonRelease       FocusIn            MouseWheel
              Circulate           FocusOut           Property
              Colormap            Gravity            Reparent
              Configure           KeyPress, Key      Unmap
              Deactivate          KeyRelease         Visibility
              Destroy             Leave


       Most of the above events have the same fields  and  behav-
       iors  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  win-
            dows.  The Activate event is sent to all the sub-win-
            dows in a toplevel when it changes from  being  deac-
            tive to active.  Likewise, the Deactive event is sent
            when the window's state changes from active to  deac-
            tive.   There are no useful percent substitutions you
            would make when binding to these events.

       MouseWheel
            Some mice on the Windows  platform  support  a  mouse
            wheel  which  is used for scrolling documents without
            using the scrollbars.  By rolling the wheel, the sys-
            tem will generate MouseWheel events that the applica-
            tion 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 substi-
            tution  to get the delta field for the event which is
            a integer value of motion that the  mouse  wheel  has
            moved.   The smallest value for which the system will
            report is defined by the OS.   On  Windows  95  &  98
            machines  this  value  is  at  least 120 before it is
            reported.  However, higher resolution devices may  be
            available  in  the  future.   The  sign  of the value
            determines which direction your widget should scroll.
            Positive  values should scroll up and negative values
            should scroll down.

       The last part of a long event specification is detail.  In
       the  case  of  a ButtonPress or ButtonRelease event, it is
       the number of a button  (1-5).   If  a  button  number  is
       given,  then  only an event on that particular button will
       match;  if no button number is given, then an event on any
       button will match.  Note:  giving a specific button number
       is different than specifying a  button  modifier;  in  the
       first  case,  it  refers  to  a  button  being  pressed or
       released, while in the second it refers to some other but-
       ton  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  key-
       board;  they include all the alphanumeric ASCII characters
       (e.g. ``a'' is the keysym for the ASCII character  ``a''),
       plus    descriptions   for   non-alphanumeric   characters
       (``comma'' is the keysym for the  comma  character),  plus
       descriptions  for  all  the non-ASCII keys on the keyboard
       (``Shift_L'' is the keysm for  the  left  shift  key,  and
       ``F1''  is  the  keysym  for  the  F1  function key, if it
       exists).  The complete list of keysyms  is  not  presented
       here;   it  is  available in other X documentation and may
       vary from system to system.  If necessary, you can use the
       %K  notation  described below to print out the keysym name
       for a particular key.  If a keysym detail is  given,  then
       the  type  field  may be omitted;  it will default to Key-
       Press.  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.   Com-
       mand  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 gen-
       erated by replacing each %, and  the  character  following
       it, with information from the current event.  The replace-
       ment 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 unde-
       fined.

       %%   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  hex-
            adecimal number.  Valid only for Configure events.

       %b   The   number  of  the  button  that  was  pressed  or
            released.  Valid only for ButtonPress  and  ButtonRe-
            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  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 Con-
            figure and Expose events.

       %k   The keycode field from the  event.   Valid  only  for
            KeyPress and KeyRelease events.

       %m   The  mode  field  from  the  event.   The substituted
            string is one of NotifyNormal, NotifyGrab,  NotifyUn-
            grab,  or  NotifyWhileGrabbed.  Valid only for Enter,
            FocusIn, FocusOut, and Leave events.

       %o   The override_redirect field from  the  event.   Valid
            only for Map, Reparent, and Configure events.

       %p   The place field from the event, substituted as one of
            the strings PlaceOnTop or PlaceOnBottom.  Valid  only
            for Circulate events.

       %s   The  state  field  from  the event.  For ButtonPress,
            ButtonRelease, Enter,  KeyPress,  KeyRelease,  Leave,
            and  Motion  events, a decimal string is substituted.
            For Visibility, one of  the  strings  VisibilityUnob-
            scured,  VisibilityPartiallyObscured, and Visibility-
            FullyObscured 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 Con-
            figure 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 ASCII character corresponding to  the
            event,  or the empty string if the event doesn't cor-
            respond to an ASCII character (e.g. the shift key was
            pressed).   XLookupString does all the work of trans-
            lating from the event to an ASCII  character.   Valid
            only for KeyPress and KeyRelease events.
       %B   The  border_width  field  from the event.  Valid only
            for Configure events.

       %D   This reports the delta value of a  MouseWheel  event.
            The  delta  value  represents  the rotation units the
            mouse wheel has been moved.  On Windows 95 & 98  sys-
            tems 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 direc-
            tion 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 KeyRe-
            lease events.

       %N   The keysym corresponding to the event, substituted as
            a decimal number.  Valid only for KeyPress and KeyRe-
            lease 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,  for-
            matted  as  a  hexadecimal  number.   Valid  only for
            events containing a subwindow field.

       %T   The type field from the event.  Valid for  all  event
            types.

       %W   The  path  name  of the window to which the event was
            reported (the window field from  the  event).   Valid
            for all event types.

       %X   The  x_root  field from the event.  If a virtual-root
            window manager is being  used  then  the  substituted
            value  is  the corresponding x-coordinate in the vir-
            tual root.  Valid  only  for  ButtonPress,  ButtonRe-
            lease, KeyPress, KeyRelease, and Motion events.

       %Y   The  y_root  field from the event.  If a virtual-root
            window manager is being  used  then  the  substituted
            value  is  the corresponding y-coordinate in the vir-
            tual root.  Valid  only  for  ButtonPress,  ButtonRe-
            lease, 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  exe-
       cuted  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 bind-
       ing  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 termi-
       nates 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 vir-
       tual 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 vir-
       tual 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 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 when-
       ever 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 pre-
       vent 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-Button-
       Press-1> will match a sequence of  presses  of  button  1,
       even though there will be ButtonRelease events (and possi-
       bly Motion events) between the ButtonPress  events.   Fur-
       thermore,  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  modi-
       fier  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 (out-
       side the context of any Tcl procedure).
SEE ALSO
       bgerror


KEYWORDS
       form, manual
