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

6       Tk::bind - Arrange for X events to invoke callbacks
7

SYNOPSIS

9       Retrieve bindings:
10
11           $widget->bind
12
13           $widget->bind(tag)
14
15           $widget->bind(sequence)
16
17           $widget->bind(tag,sequence)
18
19       Associate and destroy bindings:
20
21           $widget->bind(sequence,callback)
22
23           $widget->bind(tag,sequence,callback)
24

DESCRIPTION

26       The bind method associates callbacks with X events.  If callback is
27       specified, bind will arrange for callback to be evaluated whenever the
28       event(s) given by sequence occur in the window(s) identified by $widget
29       or tag.  If callback is an empty string then the current binding for
30       sequence is destroyed, leaving sequence unbound.  In all of the cases
31       where a callback argument is provided, bind returns an empty string.
32
33       If sequence is specified without a callback, then the callback
34       currently bound to sequence is returned, or undef is returned if there
35       is no binding for sequence.  If neither sequence nor callback is
36       specified, then the return value is a list whose elements are all the
37       sequences for which there exist bindings for tag.
38
39       If no tag is specified then the bind refers to $widget.  If tag is
40       specified then it is typically a class name and the bind refers to all
41       instances of the class on the MainWindow associated with $widget. (It
42       is possible for tag to be another "widget object" but this practice is
43       deprecated.) Perl's ref($object) can be used to get the class name of
44       any object.  Each window has an associated list of tags, and a binding
45       applies to a particular window if its tag is among those specified for
46       the window.  Although the bindtags method may be used to assign an
47       arbitrary set of binding tags to a window, the default binding tags
48       provide the following behavior:
49
50       If a tag is the name of an internal window the binding applies to that
51       window.
52
53       If the tag is the name of a toplevel window the binding applies to the
54       toplevel window and all its internal windows.
55
56       If the tag is the name of a class of widgets, such as Tk::Button, the
57       binding applies to all widgets in that class;
58
59       If tag has the value all, the binding applies to all windows descended
60       from the MainWindow of the application.
61

EVENT PATTERNS

63       The sequence argument specifies a sequence of one or more event
64       patterns, with optional white space between the patterns.  Each event
65       pat may take one of three forms.  In the simplest case it is a single
66       printing ASCII character, such as a or [.  The character may not be a
67       space character or the character <.  This form of pattern matches a
68       KeyPress event for the particular character.  The second form of
69       pattern is longer but more general.  It has the following syntax:
70
71           '<modifier-modifier-type-detail>'
72
73       The entire event pattern is surrounded by angle brackets, and normally
74       needs to be quoted, as angle brackets are special to perl.  Inside the
75       angle brackets are zero or more modifiers, an event type, and an extra
76       piece of information (detail) identifying a particular button or
77       keysym.  Any of the fields may be omitted, as long as at least one of
78       type and detail is present.  The fields must be separated by white
79       space or dashes.
80
81       The third form of pattern is used to specify a user-defined, named
82       virtual event; see Tk::event for details.  It has the following syntax:
83
84           '<<name>>'
85
86       The entire virtual event pattern is surrounded by double angle
87       brackets.  Inside the angle brackets is the user-defined name of the
88       virtual event.  Modifiers, such as Shift or Control, may not be
89       combined with a virtual event to modify it.  Bindings on a virtual
90       event may be created before the virtual event is defined, and if the
91       definition of a virtual event changes dynamically, all windows bound to
92       that virtual event will respond immediately to the new definition.
93

MODIFIERS

95       Modifiers consist of any of the following values:
96
97        Control        Mod2, M2
98        Shift          Mod3, M3
99        Lock           Mod4, M4
100        Button1, B1    Mod5, M5
101        Button2, B2    Meta, M
102        Button3, B3    Alt
103        Button4, B4    Double
104        Button5, B5    Triple
105        Mod1,    M1    Quadruple
106
107       Where more than one value is listed, separated by commas, the values
108       are equivalent.  Most of the modifiers have the obvious X meanings.
109       For example, Button1 requires that button 1 be depressed when the event
110       occurs.  For a binding to match a given event, the modifiers in the
111       event must include all of those specified in the event pattern.  An
112       event may also contain additional modifiers not specified in the
113       binding.  For example, if button 1 is pressed while the shift and
114       control keys are down, the pattern <Control-Button-1> will match the
115       event, but <Mod1-Button-1> will not.  If no modifiers are specified,
116       then any combination of modifiers may be present in the event.
117
118       Meta and M refer to whichever of the M1 through M5 modifiers is
119       associated with the meta key(s) on the keyboard (keysyms Meta_R and
120       Meta_L).  If there are no meta keys, or if they are not associated with
121       any modifiers, then Meta and M will not match any events.  Similarly,
122       the Alt modifier refers to whichever modifier is associated with the
123       alt key(s) on the keyboard (keysyms Alt_L and Alt_R).
124
125       The Double, Triple and Quadruple modifiers are a convenience for
126       specifying double mouse clicks and other repeated events. They cause a
127       particular event pattern to be repeated 2, 3 or 4 times, and also place
128       a time and space requirement on the sequence: for a sequence of events
129       to match a Double, Triple or Quadruple pattern, all of the events must
130       occur close together in time and without substantial mouse motion in
131       between.  For example, <Double-Button-1> is equivalent to
132       <Button-1><Button-1> with the extra time and space requirement.
133

EVENT TYPES

135       The type field may be any of the standard X event types, with a few
136       extra abbreviations.  Below is a list of all the valid types; where two
137       names appear together, they are synonyms.
138
139           Activate            Destroy            Map
140           ButtonPress, Button Enter              MapRequest
141           ButtonRelease       Expose             Motion
142           Circulate           FocusIn            MouseWheel
143           CirculateRequest    FocusOut           Property
144           Colormap            Gravity            Reparent
145           Configure           KeyPress, Key      ResizeRequest
146           ConfigureRequest    KeyRelease         Unmap
147           Create              Leave              Visibility
148           Deactivate
149
150       Most of the above events have the same fields and behaviors  as  events
151       in  the X Windowing system.  You can find more detailed descriptions of
152       these events in any X window programming book.  A couple of the  events
153       are  extensions to the X event system to support features unique to the
154       Macintosh and Windows platforms.  We provide a little  more  detail  on
155       these events here.  These include:
156
157           Activate
158           Deactivate
159
160       These two events are sent to every sub-window of a toplevel when they
161       change state.  In addition to the focus Window, the Macintosh platform
162       and Windows platforms have a notion of an active window (which often
163       has but is not required to have the focus).  On the Macintosh, widgets
164       in the active window have a different appearance than widgets in
165       deactive windows.  The Activate event is sent to all the sub-windows in
166       a toplevel when it changes from being deactive to active.  Likewise,
167       the Deactive event is sent when the window's state changes from active
168       to deactive.  There are no use- ful percent substitutions you would
169       make when binding to these events.
170
171           MouseWheel
172
173       Some mice on the Windows platform support a mouse wheel  which  is used
174       for  scrolling  documents  without using the scrollbars.  By rolling
175       the wheel, the system will generate MouseWheel events that the
176       application  can use to scroll.  Like Key events the event is always
177       routed to the window that currently  has  focus.  When  the event is
178       received you can use the %D substitution to get the delta field for the
179       event which is a integer value of  motion  that  the mouse  wheel  has
180       moved.  The smallest value for which the system will report is defined
181       by the OS.  On Windows  95  &  98  machines this value is at least 120
182       before it is reported.  However, higher resolution devices may be
183       available in the future.   The  sign  of the  value  determines  which
184       direction your widget should scroll.  Positive values should scroll up
185       and negative values should scroll down.
186
187       The last part of a long event specification is detail.  In the case of
188       a ButtonPress or ButtonRelease event, it is the number of a button
189       (1-5).  If a button number is given, then only an event on that
190       particular button will match;  if no button number is given, then an
191       event on any button will match.  Note:  giving a specific button number
192       is different than specifying a button modifier; in the first case, it
193       refers to a button being pressed or released, while in the second it
194       refers to some other button that is already depressed when the matching
195       event occurs.  If a button number is given then type may be omitted:
196       if will default to ButtonPress.  For example, the specifier <1> is
197       equivalent to <ButtonPress-1>.
198
199       If the event type is KeyPress or KeyRelease, then detail may be
200       specified in the form of an X keysym.  Keysyms are textual
201       specifications for particular keys on the keyboard; they include all
202       the alphanumeric ASCII characters (e.g. ``a'' is the keysym for the
203       ASCII character ``a''), plus descriptions for non-alphanumeric
204       characters (``comma'' is the keysym for the comma character), plus
205       descriptions for all the non-ASCII keys on the keyboard (``Shift_L'' is
206       the keysm for the left shift key, and ``F1'' is the keysym for the F1
207       function key, if it exists).  The complete list of keysyms is not
208       presented here;  it is available in other X documentation and may vary
209       from system to system.  If necessary, you can use the 'K' notation
210       described below to print out the keysym name for a particular key.  If
211       a keysym detail is given, then the type field may be omitted;  it will
212       default to KeyPress.  For example, <Control-comma> is equivalent to
213       <Control-KeyPress-comma>.
214

BINDING CALLBACKS AND SUBSTITUTIONS

216       The callback argument to bind is a perl/Tk callback.  which will be
217       executed whenever the given event sequence occurs.  (See Tk::callbacks
218       for description of the possible forms.)  Callback will be associated
219       with the same MainWindow that is associated with the $widget that was
220       used to invoke the bind method, and it will run as though called from
221       MainLoop.  If callback contains any Ev(%) calls, then each "nested"
222       Ev(%) "callback" will be evaluated when the event occurs to form
223       arguments to be passed to the main callback.  The replacement depends
224       on the character %, as defined in the list below.  Unless otherwise
225       indicated, the replacement string is the numeric (decimal) value of the
226       given field from the current event. Perl/Tk has enhanced this mechanism
227       slightly compared to the comparable Tcl/Tk mechanism. The enhancements
228       are not yet all reflected in the list below.  Some of the substitutions
229       are only valid for certain types of events;  if they are used for other
230       types of events the value substituted is undefined (not the same as
231       undef!).
232
233       '#' The number of the last client request processed by the server (the
234           serial field from the event).  Valid for all event types.
235
236       'a' The above field from the event, formatted as a hexadecimal number.
237           Valid only for Configure events.
238
239       'b' The number of the button that was pressed or released.  Valid only
240           for ButtonPress and ButtonRelease events.
241
242       'c' The count field from the event.  Valid only for Expose events.
243
244       'd' The detail field from the event.  The 'd' is replaced by a string
245           identifying the detail.  For Enter, Leave, FocusIn, and FocusOut
246           events, the string will be one of the following:
247
248            NotifyAncestor          NotifyNonlinearVirtual
249            NotifyDetailNone        NotifyPointer
250            NotifyInferior          NotifyPointerRoot
251            NotifyNonlinear         NotifyVirtual
252
253           For ConfigureRequest events, the string will be one of:
254
255            Above                   Opposite
256            Below                   None
257            BottomIf                TopIf
258
259           For events other than these, the substituted string is undefined.
260           (Note that this is not the same as Detail part of sequence use to
261           specify the event.)
262
263       'f' The focus field from the event (0 or 1).  Valid only for Enter and
264           Leave events.
265
266       'h' The height field from the event.  Valid only for Configure,
267           ConfigureRequest, Create, Expose, and ResizeRequest events.
268
269       'i' The window field from the  event,  represented  as  a  hexadecimal
270           integer.
271
272       'k' The keycode field from the event.  Valid only for KeyPress and
273           KeyRelease events.
274
275       'm' The mode field from the event.  The substituted string is one of
276           NotifyNormal, NotifyGrab, NotifyUngrab, or NotifyWhileGrabbed.
277           Valid only for Enter, FocusIn, FocusOut, and Leave events.
278
279       'o' The override_redirect field from the event.  Valid only for Map,
280           Reparent, and Configure events.
281
282       'p' The place field from the event, substituted as one of the strings
283           PlaceOnTop or PlaceOnBottom.  Valid only for Circulate and
284           CirculateRequest events.
285
286       's' The state field from the event.  For ButtonPress, ButtonRelease,
287           Enter, KeyPress, KeyRelease, Leave, and Motion events, a decimal
288           string is substituted.  For Visibility, one of the strings
289           VisibilityUnobscured, VisibilityPartiallyObscured, and
290           VisibilityFullyObscured is substituted.
291
292       't' The time field from the event.  Valid only for events that contain
293           a time field.
294
295       'w' The width field from the event.  Valid only for Configure,
296           ConfigueRequest, Create, Expose, and ResizeREquest events.
297
298       'x' The x field from the event.  Valid only for events containing an x
299           field.
300
301       'y' The y field from the event.  Valid only for events containing a y
302           field.
303
304       '@' The string "@x,y" where x and y are as above.  Valid only for
305           events containing x and y fields.  This format is used my methods
306           of Tk::Text and similar widgets.
307
308       'A' Substitutes the UNICODE character corresponding to the event, or
309           the empty string if the event doesn't correspond to a UNICODE
310           character (e.g. the shift key was pressed).  XmbLookupString does
311           all the work of translating from the event to a UNICODE character.
312           Valid only for KeyPress and KeyRelease events.
313
314       'B' The border_width field from the event.  Valid only for Configure,
315           ConfigureRequest and Create events.
316
317       'D' This reports the delta value of a  MouseWheel  event.   The  delta
318           value  represents  the  rotation  units  the  mouse wheel has been
319           moved.  On Windows 95 & 98 systems  the  smallest  value  for  the
320           delta is 120.  Future systems may support higher resolution values
321           for the delta.  The sign of the value represents the direction the
322           mouse wheel was scrolled.
323
324       'E' The send_event field from the event.  Valid for all event types.
325
326       'K' The keysym corresponding to the event, substituted as a textual
327           string.  Valid only for KeyPress and KeyRelease events.
328
329       'N' The keysym corresponding to the event, substituted as a decimal
330           number.  Valid only for KeyPress and KeyRelease events.
331
332       'R' The root window identifier from the event.  Valid only for events
333           containing a root field.
334
335       'S' The subwindow window identifier from the event, as an object if it
336           is one otherwise as a hexadecimal number.  Valid only for events
337           containing a subwindow field.
338
339       'T' The type field from the event.  Valid for all event types.
340
341       'W' The window to which the event was reported (the $widget field from
342           the event) - as an perl/Tk object.  Valid for all event types.
343
344       'X' The x_root field from the event.  If a virtual-root window manager
345           is being used then the substituted value is the corresponding
346           x-coordinate in the virtual root.  Valid only for ButtonPress,
347           ButtonRelease, KeyPress, KeyRelease, and Motion events.
348
349       'Y' The y_root field from the event.  If a virtual-root window manager
350           is being used then the substituted value is the corresponding
351           y-coordinate in the virtual root.  Valid only for ButtonPress,
352           ButtonRelease, KeyPress, KeyRelease, and Motion events.
353

MULTIPLE MATCHES

355       It is possible for several bindings to match a given X event.  If the
356       bindings are associated with different tag's, then each of the bindings
357       will be executed, in order.  By default, a class binding will be
358       executed first, followed by a binding for the widget, a binding for its
359       toplevel, and an all binding.  The bindtags method may be used to
360       change this order for a particular window or to associate additional
361       binding tags with the window.
362
363       return and Tk->break may be used inside a callback to control the
364       processing of matching callbacks.  If return is invoked, then the
365       current callback is terminated but Tk will continue processing
366       callbacks associated with other tag's.  If Tk->break is invoked within
367       a callback, then that callback terminates and no other callbacks will
368       be invoked for the event.  (Tk->break is implemented via perl's die
369       with a special value which is "caught" by the perl/Tk "glue" code.)
370
371       If more than one binding matches a particular event and they have the
372       same tag, then the most specific binding is chosen and its callback is
373       evaluated.  The following tests are applied, in order, to determine
374       which of several matching sequences is more specific: (a) an event
375       pattern that specifies a specific button or key is more specific than
376       one that doesn't; (b) a longer sequence (in terms of number of events
377       matched) is more specific than a shorter sequence; (c) if the modifiers
378       specified in one pattern are a subset of the modifiers in another
379       pattern, then the pattern with more modifiers is more specific.  (d) a
380       virtual event whose physical pattern matches the sequence is less
381       specific than the same physical pattern that is not associated with a
382       virtual event.  (e) given a sequence that matches two or more virtual
383       events, one of the virtual events will be chosen, but the order is
384       undefined.
385
386       If the matching sequences contain more than one event, then tests
387       (c)-(e) are applied in order from the most recent event to the least
388       recent event in the sequences.  If these tests fail to determine a
389       winner, then the most recently registered sequence is the winner.
390
391       If there are two (or more) virtual events that are both triggered by
392       the same sequence, and both of those virtual events are bound to the
393       same window tag, then only one of the virtual events will be triggered,
394       and it will be picked at random:
395
396        $widget->eventAdd('<<Paste>>' => '<Control-y>');
397        $widget->eventAdd('<<Paste>>' => '<Button-2>');
398        $widget->eventAdd <<Scroll>>' => '<Button-2>');
399        $widget->bind('Tk::Entry','<<Paste>>',sub { print 'Paste'});
400        $widget->bind('Tk::Entry','<<Scroll>>', sub {print 'Scroll'});
401
402       If the user types Control-y, the <<Paste>> binding will be invoked, but
403       if the user presses button 2 then one of either the <<Paste>> or the
404       <<Scroll>> bindings will be invoked, but exactly which one gets invoked
405       is undefined.
406
407       If an X event does not match any of the existing bindings, then the
408       event is ignored.  An unbound event is not considered to be an error.
409

MULTI-EVENT SEQUENCES AND IGNORED EVENTS

411       When a sequence specified in a bind method contains more than one event
412       pattern, then its callback is executed whenever the recent events
413       (leading up to and including the current event) match the given
414       sequence.  This means, for example, that if button 1 is clicked
415       repeatedly the sequence <Double-ButtonPress-1> will match each button
416       press but the first.  If extraneous events that would prevent a match
417       occur in the middle of an event sequence then the extraneous events are
418       ignored unless they are KeyPress or ButtonPress events.  For example,
419       <Double-ButtonPress-1> will match a sequence of presses of button 1,
420       even though there will be ButtonRelease events (and possibly Motion
421       events) between the ButtonPress events.  Furthermore, a KeyPress event
422       may be preceded by any number of other KeyPress events for modifier
423       keys without the modifier keys preventing a match.  For example, the
424       event sequence aB will match a press of the a key, a release of the a
425       key, a press of the Shift key, and a press of the b key:  the press of
426       Shift is ignored because it is a modifier key.  Finally, if several
427       Motion events occur in a row, only the last one is used for purposes of
428       matching binding sequences.
429

ERRORS

431       If an error occurs in executing the callback for a binding then the
432       Tk::Error mechanism is used to report the error.  The Tk::Error
433       mechanism will be executed at same call level, and associated with the
434       same MainWindow as as the callback was invoked.
435

CAVEATS

437       Note that for the Canvas widget, the call to bind has to be fully
438       qualified. This is because there is already a bind method for the
439       Canvas widget, which binds individual canvas tags.
440
441           $canvas->Tk::bind
442

SEE ALSO

444       Tk::Error Tk::callbacks Tk::bindtags
445

KEYWORDS

447       Event, binding
448
449
450
451perl v5.36.0                      2022-07-22                           bind(3)
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