event(3pm) User Contributed Perl Documentation event(3pm)
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
perl v5.40.1 2025-04-13 event(3pm)
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