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event(3) User Contributed Perl Documentation 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 physi-
cal event sequences are removed for virtual, so that the virtual event will not trig-
ger 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
ton-2> or <>. 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 physi-
cal 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 Button-
Release 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 substitu-
tion 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 correspond-
ing keycode value is used as the keycode field for event, overriding any detail speci-
fied in the base event argument. Valid for KeyPress and KeyRelease events. Corre-
sponds to the %K substitution for binding scripts.

-mode notify
Notify specifies the mode field for the event and must be one of NotifyNormal, Notify-
Grab, NotifyUngrab, or NotifyWhileGrabbed. Valid for Enter, Leave, FocusIn, and Focu-
sOut 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 substi-
tution 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 speci-
fies the root field for the event. Valid for KeyPress, KeyRelease, ButtonPress, But-
tonRelease, 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 Visi-
bility 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, Button-
Press, 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 Prop-
erty 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 han-
dled 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, Con-
figure, 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 vir-
tual 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 defini-
tions:

$widget->eventAdd('<>' => '');
$widget->eventAdd('<>' => '');
$widget->eventAdd('<>' => '');
$widget->eventAdd('<>' => '');

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

$entry->bind('Tk::Entry', '<>' => 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 <> virtual event is synthesized
with eventGenerate, then the <> 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('<>' => '','');
$mw->bind('Tk::Entry', '' => sub{print 'Control-y'});
$mw->bind('Tk::Entry', '<>' => sub{print 'Paste'});

When the user types Control-y the 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 <> binding will be invoked, because
the Meta modifier in the physical pattern associated with the virtual binding is more spe-
cific than the > 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 immedi-
ately to the new definition. Starting from the preceding example, if the following code
is executed:

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

the behavior will change such in two ways. First, the shadowed <> binding will
emerge. Typing Control-y will no longer invoke the binding, but instead
invoke the virtual event <>. Second, pressing the F6 key will now also invoke the
<> binding.