event(3)

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.

-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