event

event(n)                     Tk Built-In Commands                     event(n)



______________________________________________________________________________

NAME
       event - Miscellaneous event facilities: define virtual events and
       generate events

SYNOPSIS
       event option ?arg arg ...?
_________________________________________________________________


DESCRIPTION
       The event command provides several facilities for dealing with window
       system events, such as defining virtual events and synthesizing events.
       The command has several different forms, determined by the first
       argument.  The following forms are currently supported:

       event add <<virtual>> sequence ?sequence ...?
              Associates the virtual event virtual with the physical event
              sequence(s) given by the sequence arguments, so that the virtual
              event will trigger whenever any one of the sequences occurs.
              Virtual may be any string value and sequence may have any of the
              values allowed for the sequence argument to the bind command.
              If virtual is already defined, the new physical event sequences
              add to the existing sequences for the event.

       event delete <<virtual>> ?sequence sequence ...?
              Deletes each of the sequences from those associated with the
              virtual event given by virtual.  Virtual may be any string value
              and sequence may have any of the values allowed for the sequence
              argument to the bind command.  Any sequences not currently
              associated with virtual are ignored.  If no sequence argument is
              provided, all physical event sequences are removed for virtual,
              so that the virtual event will not trigger anymore.

       event generate window event ?option value option value ...?
              Generates a window event and arranges for it to be processed
              just as if it had come from the window system.  Window gives the
              path name of the window for which the event will be generated;   │
              it may also be an identifier (such as returned by winfo id) as   │
              long as it is for a window in the current application.  Event
              provides a basic description of the event, such as <Shift-
              Button-2> or <<Paste>>.  If Window is empty the whole screen is
              meant, and coordinates are relative to the screen.  Event may
              have any of the forms allowed for the sequence argument of the
              bind command except that it must consist of a single event
              pattern, not a sequence.  Option-value pairs may be used to
              specify additional attributes of the event, such as the x and y
              mouse position;  see EVENT FIELDS below.  If the -when option is
              not specified, the event is processed immediately:  all of the
              handlers for the event will complete before the event generate
              command returns.  If the -when option is specified then it
              determines when the event is processed.  Certain events, such as
              key events, require that the window has focus to receive the
              event properly.

       event info ?<<virtual>>?
              Returns information about virtual events.  If the <<virtual>>
              argument is omitted, the return value is a list of all the
              virtual events that are currently defined.  If <<virtual>> is
              specified then the return value is a list whose elements are the
              physical event sequences currently defined for the given virtual
              event;  if the virtual event is not defined then an empty string
              is returned.


EVENT FIELDS
       The following options are supported for the event generate command.
       These correspond to the ``%'' expansions allowed in binding scripts for
       the bind command.

       -above window
              Window specifies the above field for the event, either as a
              window path name or as an integer window id.  Valid for
              Configure events.  Corresponds to the %a substitution for
              binding scripts.

       -borderwidth size
              Size must be a screen distance;  it specifies the border_width
              field for the event.  Valid for Configure events.  Corresponds
              to the %B substitution for binding scripts.

       -button number
              Number must be an integer;  it specifies the detail field for a
              ButtonPress or ButtonRelease event, overriding any button
              number provided in the base event argument.  Corresponds to the
              %b substitution for binding scripts.

       -count number
              Number must be an integer;  it specifies the count field for the
              event.  Valid for Expose events.  Corresponds to the %c
              substitution for binding scripts.

       -delta number
              Number must be an integer;  it specifies the delta field for the
              MouseWheel event.  The delta refers to the direction and
              magnitude the mouse wheel was rotated.  Note the value is not a
              screen distance but are units of motion in the mouse wheel.
              Typically these values are multiples of 120.  For example, 120
              should scroll the text widget up 4 lines and -240 would scroll
              the text widget down 8 lines.  Of course, other widgets may
              define different behaviors for mouse wheel motion.  This field
              corresponds to the %D substitution for binding scripts.

       -detail detail
              Detail specifies the detail field for the event and must be one
              of the following:
              NotifyAncestor          NotifyNonlinearVirtual
              NotifyDetailNone        NotifyPointer
              NotifyInferior          NotifyPointerRoot
              NotifyNonlinear         NotifyVirtual Valid for Enter, Leave,
              FocusIn and FocusOut events.  Corresponds to the %d substitution
              for binding scripts.

       -focus boolean
              Boolean must be a boolean value;  it specifies the focus field
              for the event.  Valid for Enter and Leave events.  Corresponds
              to the %f substitution for binding scripts.

       -height size
              Size must be a screen distance;  it specifies the height field
              for the event.  Valid for Configure events.  Corresponds to the
              %h substitution for binding scripts.

       -keycode number
              Number  must be an integer;  it specifies the keycode field for
              the event.  Valid for KeyPress and KeyRelease events.
              Corresponds to the %k substitution for binding scripts.

       -keysym name
              Name must be the name of a valid keysym, such as g, space, or
              Return;  its corresponding keycode value is used as the keycode
              field for event, overriding any detail specified in the base
              event argument.  Valid for KeyPress and KeyRelease events.
              Corresponds to the %K substitution for binding scripts.

       -mode notify
              Notify specifies the mode field for the event and must be one of
              NotifyNormal, NotifyGrab, NotifyUngrab, or NotifyWhileGrabbed.
              Valid for Enter, Leave, FocusIn, and FocusOut events.
              Corresponds to the %m substitution for binding scripts.

       -override boolean
              Boolean must be a boolean value;  it specifies the
              override_redirect field for the event.  Valid for Map, Reparent,
              and Configure events.  Corresponds to the %o substitution for
              binding scripts.

       -place where
              Where specifies the place field for the event;  it must be
              either PlaceOnTop or PlaceOnBottom.  Valid for Circulate events.
              Corresponds to the %p substitution for binding scripts.

       -root window
              Window must be either a window path name or an integer window
              identifier;  it specifies the root field for the event.  Valid
              for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter,
              Leave, and Motion events.  Corresponds to the %R substitution
              for binding scripts.

       -rootx coord
              Coord must be a screen distance;  it specifies the x_root field
              for the event.  Valid for KeyPress, KeyRelease, ButtonPress,
              ButtonRelease, Enter, Leave, and Motion events.  Corresponds to
              the %X substitution for binding scripts.

       -rooty coord
              Coord must be a screen distance;  it specifies th y_root field
              for the event.  Valid for KeyPress, KeyRelease, ButtonPress,
              ButtonRelease, Enter, Leave, and Motion events.  Corresponds to
              the %Y substitution for binding scripts.

       -sendevent boolean
              Boolean must be a boolean value;  it specifies the send_event
              field for the event.  Valid for all events.  Corresponds to the
              %E substitution for binding scripts.

       -serial number
              Number must be an integer;  it specifies the serial field for
              the event.  Valid for all events.  Corresponds to the %#
              substitution for binding scripts.

       -state state
              State specifies the state field for the event.  For KeyPress,
              KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion
              events it must be an integer value.  For Visibility events it
              must be one of VisibilityUnobscured,
              VisibilityPartiallyObscured, or VisibilityFullyObscured.  This
              option overrides any modifiers such as Meta or Control specified
              in the base event.  Corresponds to the %s substitution for
              binding scripts.

       -subwindow window
              Window specifies the subwindow field for the event, either as a
              path name for a Tk widget or as an integer window identifier.
              Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease,
              Enter, Leave, and Motion events.  Similar to %S substitution for
              binding scripts.

       -time integer
              Integer must be an integer value;  it specifies the time field
              for the event.  Valid for KeyPress, KeyRelease, ButtonPress,
              ButtonRelease, Enter, Leave, Motion, and Property events.
              Corresponds to the %t substitution for binding scripts.

       -warp boolean
              boolean must be a boolean value;  it specifies whether the
              screen pointer should be warped as well.  Valid for KeyPress,
              KeyRelease, ButtonPress, ButtonRelease, and Motion events.  The
              pointer will only warp to a window if it is mapped.

       -width size
              Size must be a screen distance;  it specifies the width field
              for the event.  Valid for Configure events.  Corresponds to the
              %w substitution for binding scripts.

       -when when
              When determines when the event will be processed;  it must have
              one of the following values:

              now       Process the event immediately, before the command
                        returns.  This also happens if the -when option is
                        omitted.

              tail      Place the event on Tcl's event queue behind any events
                        already queued for this application.

              head      Place the event at the front of Tcl's event queue, so
                        that it will be handled before any other events
                        already queued.

              mark      Place the event at the front of Tcl's event queue but
                        behind any other events already queued with -when
                        mark.  This option is useful when generating a series
                        of events that should be processed in order but at the
                        front of the queue.

       -x coord
              Coord must be a screen distance;  it specifies the x field for
              the event.  Valid for KeyPress, KeyRelease, ButtonPress,
              ButtonRelease, Motion, Enter, Leave, Expose, Configure, Gravity,
              and Reparent events.  Corresponds to the the %x substitution for
              binding scripts.  If Window is empty the coordinate is relative
              to the screen, and this option corresponds to the %X
              substitution for binding scripts.

       -y coord
              Coord must be a screen distance;  it specifies the y field for
              the event.  Valid for KeyPress, KeyRelease, ButtonPress,
              ButtonRelease, Motion, Enter, Leave, Expose, Configure, Gravity,
              and Reparent events.  Corresponds to the the %y substitution for
              binding scripts.  If Window is empty the coordinate is relative
              to the screen, and this option corresponds to the %Y
              substitution for binding scripts.

       Any options that are not specified when generating an event are filled
       with the value 0, except for serial, which is filled with the next X
       event serial number.


VIRTUAL EVENT EXAMPLES
       In order for a virtual event binding to trigger, two things must
       happen.  First, the virtual event must be defined with the event add
       command.  Second, a binding must be created for the virtual event with
       the bind command.  Consider the following virtual event definitions:
              event add <<Paste>> <Control-y>
              event add <<Paste>> <Button-2>
              event add <<Save>> <Control-X><Control-S>
              event add <<Save>> <Shift-F12>
       In the bind command, a virtual event can be bound like any other
       builtin event type as follows:
              bind Entry <<Paste>> {%W insert [selection get]}
       The double angle brackets are used to specify that a virtual event is
       being bound.  If the user types Control-y or presses button 2, or if a
       <<Paste>> virtual event is synthesized with event generate, then the
       <<Paste>> binding will be invoked.

       If a virtual binding has the exact same sequence as a separate physical
       binding, then the physical binding will take precedence.  Consider the
       following example:
              event add <<Paste>> <Control-y> <Meta-Control-y>
              bind Entry <Control-y> {puts Control-y}
              bind Entry <<Paste>> {puts Paste}
       When the user types Control-y the <Control-y> binding will be invoked,
       because a physical event is considered more specific than a virtual
       event, all other things being equal.  However, when the user types
       Meta-Control-y the <<Paste>> binding will be invoked, because the Meta
       modifier in the physical pattern associated with the virtual binding is
       more specific than the <Control-y> sequence for the physical event.

       Bindings on a virtual event may be created before the virtual event
       exists.  Indeed, the virtual event never actually needs to be defined,
       for instance, on platforms where the specific virtual event would
       meaningless or ungeneratable.

       When a definition of a virtual event changes at run time, all windows
       will respond immediately to the new definition.  Starting from the
       preceding example, if the following code is executed:
              bind <Entry> <Control-y> {}
              event add <<Paste>> <Key-F6>
       the behavior will change such in two ways.  First, the shadowed
       <<Paste>> binding will emerge.  Typing Control-y will no longer invoke
       the <Control-y> binding, but instead invoke the virtual event
       <<Paste>>.  Second, pressing the F6 key will now also invoke the
       <<Paste>> binding.


SEE ALSO
       bind


KEYWORDS
       event, binding, define, handle, virtual event



Tk                                    8.3                             event(n)