bind

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 ?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
       called the “binding 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.

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 following 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
       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
       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.

   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              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. 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.

   EVENT DETAILS
       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>.

BINDING SCRIPTS AND SUBSTITUTIONS
       The script argument to bind is a Tcl script, called the “binding
       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. 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.

       %M   The number of script-based binding patterns matched so far for the
            event.  Valid for all event types.

       %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, Enter, KeyPress,
            KeyRelease, Leave 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
              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
       had not 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 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
       within a binding script, then this binding script, including all other
       “+” appended scripts, 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.

       Within a script called from the binding script, return -code ok may be
       used to continue processing (including “+” appended scripts), or return
       -code break may be used to stop processing all other binding scripts.

       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.

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-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.

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
       procedure).

EXAMPLES
       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"
              }

SEE ALSO
       bgerror(n), bindtags(n), event(n), focus(n), grab(n), keysyms(n)

KEYWORDS
       binding, event



Tk                                    8.0                              bind(n)