NAME

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

SYNOPSIS

       $widget->eventAction(?arg, arg, ...?);

DESCRIPTION

       The eventAction methods provides several facilities for dealing with window system events, such as
       defining virtual events and synthesizing events.  Virtual events are shared by all widgets of the same
       MainWindow.  Different MainWindows can have different virtual event.

       The following methods are currently supported:

       $widget->eventAdd('<<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 method.  If virtual is already defined, the new physical event sequences add to the existing
           sequences for the event.

       $widget->eventDelete('<<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 method.  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.

       $widget->eventGenerate(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 is a reference to the window for which the event will be generated.  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 method 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 eventGenerate method returns.  If the -when option is specified then it determines when
           the event is processed.

       $widget->eventInfo(?'<<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 undef is returned.

EVENT FIELDS

       The following options are supported for the eventGenerate method.  These correspond to the ``%''
       expansions allowed in binding callback for the bind method.

       -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 the 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.

       -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 perl/Tk's event queue behind any events already queued for this
                   application.

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

           mark    Place the event at the front of perl/Tk'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 eventAdd method.  Second, a binding must be created for the virtual event with the
       bind method.  Consider the following virtual event definitions:

        $widget->eventAdd('<<Paste>>' => '<Control-y>');
        $widget->eventAdd('<<Paste>>' => '<Button-2>');
        $widget->eventAdd('<<Save>>' => '<Control-X><Control-S>');
        $widget->eventAdd('<<Save>>' => '<Shift-F12>');

       In the bind method, a virtual event can be bound like any other builtin event type as follows:

        $entry->bind('Tk::Entry', '<<Paste>>' => sub {
                       $entry->Insert($entry->selectionGet) });

       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 eventGenerate, 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:

        $mw->eventAdd('<<Paste>>' => '<Control-y>','<Meta-Control-y>');
        $mw->bind('Tk::Entry', '<Control-y>' => sub{print 'Control-y'});
        $mw->bind('Tk::Entry', '<<Paste>>'   => sub{print '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:

        $entry->bind(ref($entry), '<Control-y>' => undef);
        $entry->eventAdd('<<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

       Tk::bind Tk::callbacks

KEYWORDS

       event, binding, define, handle, virtual event