= bind: Arrange for events to invoke Tk scripts     bind tag sequence script     bind tag sequence +script The  bind  command  associates Tk scripts with window events.If all three arguments are specified, bind will  arrange  forscript  (a  Tk  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 toany existing binding for sequence;  otherwise script replacesany  existing binding.  If script is an empty string then thecurrent binding for sequence is destroyed,  leaving  sequenceunbound.  In all of the cases where a script argument is pro‐vided, bind returns an empty string.  If script  is  prefixedwith  a  ``-'', then any existing binding for sequence, whosescript is exactly the same as script, is  removed.   The  tagargument  gives  the pathname of the window to which sequenceis bound.    Event PatternsThe sequence argument specifies a sequence  of  one  or  moreevent  patterns,  with  optional white space between the pat‐terns.  Each event pattern may take one of two forms.  In thesimplest  case  it is a single printing ASCII character, suchas a or [.  The character may not be a space character or thecharacter  <.   This form of pattern matches a KeyPress eventfor the particular character.  The second form of pattern  islonger but more general.  It has the following syntax:        <event-event-...-event> The following events are accepted: Key or Keypress       This represents the press of the character in the fol‐       lowing event.  If there is no  following  event,  this       represents the press of any key. The key letter may be       escaped with a backslash (\) to prevent any  character       (e.g.  >) from being treated specially. Configure       This  event  occurs  whenever the widget is configured       such that its requested size changes. Control       This represents the press of the character in the fol‐       lowing event with the Control key pressed. The charac‐       ter may be quoted as for Key. ButtonPress or Button       This represents the pressed state of the mouse  button       given by the following event, which should be 1, 2, or       3. If there is no following event, this represents the       press  of  any  button.   If the mouse is moved with a       button pressed, the Button event is delivered in  com‐       bination  with  a  Motion  event so long as the button       remains pressed. ButtonRelease       Like ButtonPress, but represents the  release  of  any       button. Motion Mouse movement. Double Any events in the sequence representing button presses       must be double-clicked for the sequence to match. Map    The event that a toplevel widget is  mapped  onto  the       screen. Unmap  The  event that a toplevel widget is unmapped from the       screen. Enter  The event of the mouse entering the widget  from  out‐       side. Leave  The  event  of the mouse leaving the boundaries of the       widget. FocusIn       The event of the widget getting the keyboard focus. FocusOut       The event of the widget losing the keyboard focus. Destroy       The  event  of  the  widget  being   destroyed.    See       destroy(9) for details of widget destruction. The  event  sequence can contain any combination of the aboveevents. They are treated independently, and  if  any  of  theevents  occur,  the  sequence matches. You cannot combine keypresses of more than one key. Events will not be combined  ondelivery, except that Motion events may be combined with but‐ton presses (possibly doubled).    Binding Scripts and SubstitutionsThe script argument to bind is a Tk  script,  which  will  beexecuted whenever the given event sequence occurs.  If scriptcontains any % characters, then the script will not  be  exe‐cuted  directly.   Instead, a new script will be generated byreplacing each %, and the character following it, with infor‐mation  from  the  current event.  The replacement depends onthe character following the %, as defined in the list  below.Unless  otherwise  indicated,  the  replacement string is thedecimal value of the given  field  from  the  current  event.Some of the substitutions are only valid for certain types ofevents;  if they are used for other types of events the valuesubstituted is undefined. %%   Replaced with a single percent. %b   The  number  of the button that was pressed or released.     Valid only for ButtonPress and ButtonRelease events. %h   For Configure events, this is the old  requested  height     of the widget. %s   For  mouse  events,  this is the logical OR of the mouse     buttons; for keyboard events, it is the decimal value of     the pressed character. %w   For Configure events, this is the old requested width of     the widget. %x   The x coordinate from the event, relative to the  origin     of the toplevel window. Valid only for Enter, Leave, and     mouse events. %y   The y coordinate from the event, relative to the  origin     of the toplevel window. Valid only for Enter, Leave, and     mouse events. %A   The ASCII character corresponding to a Key event. %K   The pressed character for the event, as four hexadecimal     digits.  Valid only for Key events. %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   Same  as  %x except that the screen coordinate system is     used. %Y   Same as %y except that the screen coordinate  system  is     used. The  replacement string for a %-replacement is formatted as aproper Tk list element.  This means  that  it  will  be  sur‐rounded with braces if it contains spaces, or special charac‐ters such as $ and { may be preceded  by  backslashes.   Thisguarantees  that  the  string  will  be passed through the Tkparser when the binding script is evaluated. == bugsThe above scheme is not ideal, and will probably be fixed  in= the  future.   Quoting is a mess: in particular, the quotingprovided for the %A substitution does not work correctly whena quoted character is re-interpreted by Tk. The length of binding scripts is limited to 128 characters.