1event(3)              User Contributed Perl Documentation             event(3)
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NAME

6       Tk::event - Miscellaneous event facilities: define virtual events and
7       generate events
8

SYNOPSIS

10       $widget->eventAction(?arg, arg, ...?);
11

DESCRIPTION

13       The eventAction methods provides several facilities for dealing with
14       window system events, such as defining virtual events and synthesizing
15       events.  Virtual events are shared by all widgets of the same
16       MainWindow.  Different MainWindows can have different virtual event.
17
18       The following methods are currently supported:
19
20       $widget->eventAdd('<<virtual>>', sequence ?,sequence, ...?)
21           Associates the virtual event virtual with the physical event
22           sequence(s) given by the sequence arguments, so that the virtual
23           event will trigger whenever any one of the sequences occurs.
24           Virtual may be any string value and sequence may have any of the
25           values allowed for the sequence argument to the bind method.  If
26           virtual is already defined, the new physical event sequences add to
27           the existing sequences for the event.
28
29       $widget->eventDelete('<<virtual>>' ?,sequence, sequence, ...?)
30           Deletes each of the sequences from those associated with the
31           virtual event given by virtual.  Virtual may be any string value
32           and sequence may have any of the values allowed for the sequence
33           argument to the bind method.  Any sequences not currently
34           associated with virtual are ignored.  If no sequence argument is
35           provided, all physical event sequences are removed for virtual, so
36           that the virtual event will not trigger anymore.
37
38       $widget->eventGenerate(event ?,option => value, option => value, ...?)
39           Generates a window event and arranges for it to be processed just
40           as if it had come from the window system.  $window is a reference
41           to the window for which the event will be generated.  Event
42           provides a basic description of the event, such as <Shift-Button-2>
43           or <<Paste>>.  If Window is empty the whole screen is meant, and
44           coordinates are relative to the screen.  Event may have any of the
45           forms allowed for the sequence argument of the bind method except
46           that it must consist of a single event pattern, not a sequence.
47           Option-value pairs may be used to specify additional attributes of
48           the event, such as the x and y mouse position; see "EVENT FIELDS"
49           below.  If the -when option is not specified, the event is
50           processed immediately:  all of the handlers for the event will
51           complete before the eventGenerate method returns.  If the -when
52           option is specified then it determines when the event is processed.
53
54       $widget->eventInfo(?'<<virtual>>'?)
55           Returns information about virtual events.  If the <<virtual>>
56           argument is omitted, the return value is a list of all the virtual
57           events that are currently defined.  If <<virtual>> is specified
58           then the return value is a list whose elements are the physical
59           event sequences currently defined for the given virtual event;  if
60           the virtual event is not defined then undef is returned.
61

EVENT FIELDS

63       The following options are supported for the eventGenerate method.
64       These correspond to the ``%'' expansions allowed in binding callback
65       for the bind method.
66
67       -above => window
68           Window specifies the above field for the event, either as a window
69           path name or as an integer window id.  Valid for Configure events.
70           Corresponds to the %a substitution for binding scripts.
71
72       -borderwidth => size
73           Size must be a screen distance;  it specifies the border_width
74           field for the event.  Valid for Configure events.  Corresponds to
75           the %B substitution for binding scripts.
76
77       -button => number
78           Number must be an integer;  it specifies the detail field for a
79           ButtonPress or ButtonRelease event, overriding any button  number
80           provided in the base event argument.  Corresponds to the %b
81           substitution for binding scripts.
82
83       -count => number
84           Number must be an integer;  it specifies the count field for the
85           event.  Valid for Expose events.  Corresponds to the %c
86           substitution for binding scripts.
87
88       -delta => number
89           number must be an integer; it specifies the delta field for the
90           MouseWheel event.  The delta refers to the direction and magnitude
91           the mouse wheel was rotated.  Note the value is not a screen
92           distance but are units of motion in the mouse wheel.  Typically
93           these values are multiples of 120.  For example, 120 should scroll
94           the text widget up 4 lines and -240 would scroll the text widget
95           down 8 lines.  Of course, other widgets may define different
96           behaviors for mouse wheel motion.  This field corresponds to the %D
97           substitution for binding scripts.
98
99       -detail => detail
100           Detail specifies the detail field for the event and must be one of
101           the following:
102
103            NotifyAncestor         NotifyNonlinearVirtual
104            NotifyDetailNone       NotifyPointer
105            NotifyInferior         NotifyPointerRoot
106            NotifyNonlinear        NotifyVirtual
107
108           Valid for Enter, Leave, FocusIn and FocusOut events.  Corresponds
109           to the %d substitution for binding scripts.
110
111       -focus boolean
112           Boolean must be a boolean value;  it specifies the focus field for
113           the event.  Valid for Enter and Leave events.  Corresponds to the
114           %f substitution for binding scripts.
115
116       -height size
117           Size must be a screen distance;  it specifies the height field for
118           the event.  Valid for Configure events.  Corresponds to the %h
119           substitution for binding scripts.
120
121       -keycode number
122           Number  must be an integer;  it specifies the keycode field for the
123           event.  Valid for KeyPress and KeyRelease events.  Corresponds to
124           the %k substitution for binding scripts.
125
126       -keysym name
127           Name must be the name of a valid keysym, such as g, space, or
128           Return;  its corresponding keycode value is used as the keycode
129           field for event, overriding any detail specified in the base event
130           argument.  Valid for KeyPress and KeyRelease events.  Corresponds
131           to the %K substitution for binding scripts.
132
133       -mode notify
134           Notify specifies the mode field for the event and must be one of
135           NotifyNormal, NotifyGrab, NotifyUngrab, or NotifyWhileGrabbed.
136           Valid for Enter, Leave, FocusIn, and FocusOut events.  Corresponds
137           to the %m substitution for binding scripts.
138
139       -override boolean
140           Boolean must be a boolean value;  it specifies the
141           override_redirect field for the event.  Valid for Map, Reparent,
142           and Configure events.  Corresponds to the %o substitution for
143           binding scripts.
144
145       -place where
146           Where specifies the place field for the event;  it must be either
147           PlaceOnTop or PlaceOnBottom.  Valid for Circulate events.
148           Corresponds to the %p substitution for binding scripts.
149
150       -root window
151           Window must be either a window path name or an integer window
152           identifier;  it specifies the root field for the event.  Valid for
153           KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and
154           Motion events.  Corresponds to the %R substitution for binding
155           scripts.
156
157       -rootx coord
158           Coord must be a screen distance;  it specifies the x_root field for
159           the event.  Valid for KeyPress, KeyRelease, ButtonPress,
160           ButtonRelease, Enter, Leave, and Motion events.  Corresponds to the
161           %X substitution for binding scripts.
162
163       -rooty coord
164           Coord must be a screen distance;  it specifies the y_root field for
165           the event.  Valid for KeyPress, KeyRelease, ButtonPress,
166           ButtonRelease, Enter, Leave, and Motion events.  Corresponds to the
167           %Y substitution for binding scripts.
168
169       -sendevent boolean
170           Boolean must be a boolean value;  it specifies the send_event field
171           for the event.  Valid for all events.  Corresponds to the %E
172           substitution for binding scripts.
173
174       -serial number
175           Number must be an integer;  it specifies the serial field for the
176           event.  Valid for all events.  Corresponds to the %# substitution
177           for binding scripts.
178
179       -state state
180           State specifies the state field for the event.  For KeyPress,
181           KeyRelease, ButtonPress, ButtonRelease, Enter, Leave, and Motion
182           events it must be an integer value.  For Visibility events it must
183           be one of VisibilityUnobscured, VisibilityPartiallyObscured, or
184           VisibilityFullyObscured.  This option overrides any modifiers such
185           as Meta or Control specified in the base event.  Corresponds to the
186           %s substitution for binding scripts.
187
188       -subwindow window
189           Window specifies the subwindow field for the event, either as a
190           path name for a Tk widget or as an integer window identifier.
191           Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease, Enter,
192           Leave, and Motion events.  Similar to %S substitution for binding
193           scripts.
194
195       -time integer
196           Integer must be an integer value;  it specifies the time field for
197           the event.  Valid for KeyPress, KeyRelease, ButtonPress,
198           ButtonRelease, Enter, Leave, Motion, and Property events.
199           Corresponds to the %t substitution for binding scripts.
200
201       -warp boolean
202           boolean must be a boolean value;  it specifies whether the screen
203           pointer should be warped as well.  Valid for KeyPress, KeyRelease,
204           ButtonPress, ButtonRelease, and Motion events.
205
206       -width size
207           Size must be a screen distance;  it specifies the width field for
208           the event.  Valid for Configure events.  Corresponds to the %w
209           substitution for binding scripts.
210
211       -when when
212           When determines when the event will be processed;  it must have one
213           of the following values:
214
215           now     Process the event immediately, before the command returns.
216                   This also happens if the -when option is omitted.
217
218           tail    Place the event on perl/Tk's event queue behind any events
219                   already queued for this application.
220
221           head    Place the event at the front of perl/Tk's event queue, so
222                   that it will be handled before any other events already
223                   queued.
224
225           mark    Place the event at the front of perl/Tk's event queue but
226                   behind any other events already queued with -when mark.
227                   This option is useful when generating a series of events
228                   that should be processed in order but at the front of the
229                   queue.
230
231       -x coord
232           Coord must be a screen distance;  it specifies the x field for the
233           event.  Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease,
234           Motion, Enter, Leave, Expose, Configure, Gravity, and Reparent
235           events.  Corresponds to the the %x substitution for binding
236           scripts.  If Window is empty the coordinate is relative to the
237           screen, and this option corresponds to the %X substitution for
238           binding scripts.
239
240       -y coord
241           Coord must be a screen distance;  it specifies the y field for the
242           event.  Valid for KeyPress, KeyRelease, ButtonPress, ButtonRelease,
243           Motion, Enter, Leave, Expose, Configure, Gravity, and Reparent
244           events.  Corresponds to the the %y substitution for binding
245           scripts.  If Window is empty the coordinate is relative to the
246           screen, and this option corresponds to the %Y substitution for
247           binding scripts.
248
249           Any options that are not specified when generating an event are
250           filled with the value 0, except for serial, which is filled with
251           the next X event serial number.
252

VIRTUAL EVENT EXAMPLES

254       In order for a virtual event binding to trigger, two things must
255       happen.  First, the virtual event must be defined with the eventAdd
256       method.  Second, a binding must be created for the virtual event with
257       the bind method.  Consider the following virtual event definitions:
258
259        $widget->eventAdd('<<Paste>>' => '<Control-y>');
260        $widget->eventAdd('<<Paste>>' => '<Button-2>');
261        $widget->eventAdd('<<Save>>' => '<Control-X><Control-S>');
262        $widget->eventAdd('<<Save>>' => '<Shift-F12>');
263
264       In the bind method, a virtual event can be bound like any other builtin
265       event type as follows:
266
267        $entry->bind('Tk::Entry', '<<Paste>>' => sub {
268                       $entry->Insert($entry->selectionGet) });
269
270       The double angle brackets are used to specify that a virtual event is
271       being bound.  If the user types Control-y or presses button 2, or if a
272       <<Paste>> virtual event is synthesized with eventGenerate, then the
273       <<Paste>> binding will be invoked.
274
275       If a virtual binding has the exact same sequence as a separate physical
276       binding, then the physical binding will take precedence.  Consider the
277       following example:
278
279        $mw->eventAdd('<<Paste>>' => '<Control-y>','<Meta-Control-y>');
280        $mw->bind('Tk::Entry', '<Control-y>' => sub{print 'Control-y'});
281        $mw->bind('Tk::Entry', '<<Paste>>'   => sub{print 'Paste'});
282
283       When the user types Control-y the <Control-y> binding will be invoked,
284       because a physical event is considered more specific than a virtual
285       event, all other things being equal.  However, when the user types
286       Meta-Control-y the <<Paste>> binding will be invoked, because the Meta
287       modifier in the physical pattern associated with the virtual binding is
288       more specific than the <Control-y> sequence for the physical event.
289
290       Bindings on a virtual event may be created before the virtual event
291       exists.  Indeed, the virtual event never actually needs to be defined,
292       for instance, on platforms where the specific virtual event would
293       meaningless or ungeneratable.
294
295       When a definition of a virtual event changes at run time, all windows
296       will respond immediately to the new definition.  Starting from the
297       preceding example, if the following code is executed:
298
299        $entry->bind(ref($entry), '<Control-y>' => undef);
300        $entry->eventAdd('<<Paste>>' => '<Key-F6>');
301
302       the behavior will change such in two ways.  First, the shadowed
303       <<Paste>> binding will emerge.  Typing Control-y will no longer invoke
304       the <Control-y> binding, but instead invoke the virtual event
305       <<Paste>>.  Second, pressing the F6 key will now also invoke the
306       <<Paste>> binding.
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SEE ALSO

309       Tk::bind Tk::callbacks
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KEYWORDS

312       event, binding, define, handle, virtual event
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316perl v5.30.0                      2019-07-26                          event(3)
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