| 1 | # Copyright (c) 1990 The Regents of the University of California. |
| 2 | # Copyright (c) 1994-1996 Sun Microsystems, Inc. |
| 3 | # See the file "license.terms" for information on usage and redistribution |
| 4 | # of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
| 5 | # |
| 6 | # |
| 7 | |
| 8 | =head1 NAME |
| 9 | |
| 10 | Tk::bind - Arrange for X events to invoke callbacks |
| 11 | |
| 12 | =for category Binding Events and Callbacks |
| 13 | |
| 14 | =head1 SYNOPSIS |
| 15 | |
| 16 | Retrieve bindings: |
| 17 | |
| 18 | S< >I<$widget>-E<gt>B<bind> |
| 19 | |
| 20 | S< >I<$widget>-E<gt>B<bind>(I<tag>) |
| 21 | |
| 22 | S< >I<$widget>-E<gt>B<bind>(I<sequence>) |
| 23 | |
| 24 | S< >I<$widget>-E<gt>B<bind>(I<tag>,I<sequence>) |
| 25 | |
| 26 | Associate and destroy bindings: |
| 27 | |
| 28 | S< >I<$widget>-E<gt>B<bind>(I<sequence>,I<callback>) |
| 29 | |
| 30 | S< >I<$widget>-E<gt>B<bind>(I<tag>,I<sequence>,I<callback>) |
| 31 | |
| 32 | =head1 DESCRIPTION |
| 33 | |
| 34 | The B<bind> method associates callbacks with X events. |
| 35 | If I<callback> is specified, B<bind> will |
| 36 | arrange for I<callback> to be evaluated whenever |
| 37 | the event(s) given by I<sequence> occur in the window(s) |
| 38 | identified by I<$widget> or I<tag>. |
| 39 | If I<callback> is an empty string then the current binding for |
| 40 | I<sequence> is destroyed, leaving I<sequence> unbound. |
| 41 | In all of the cases where a I<callback> argument is provided, |
| 42 | B<bind> returns an empty string. |
| 43 | |
| 44 | If I<sequence> is specified without a I<callback>, then the |
| 45 | callback currently bound to I<sequence> is returned, or |
| 46 | B<undef> is returned if there is no binding for I<sequence>. |
| 47 | If neither I<sequence> nor I<callback> is specified, then the |
| 48 | return value is a list whose elements are all the sequences |
| 49 | for which there exist bindings for I<tag>. |
| 50 | |
| 51 | If no I<tag> is specified then the B<bind> refers to I<$widget>. |
| 52 | If I<tag> is specified then it is typically a class name and the B<bind> |
| 53 | refers to all instances of the class on the B<MainWindow> associated |
| 54 | with I<$widget>. (It is possible for I<tag> to be another "widget object" |
| 55 | but this practice is deprecated.) Perl's B<ref>(I<$object>) can be used |
| 56 | to get the class name of any object. |
| 57 | Each window has an associated list of tags, and a binding applies |
| 58 | to a particular window if its tag is among those specified for |
| 59 | the window. |
| 60 | Although the B<bindtags> method may be used to assign an |
| 61 | arbitrary set of binding tags to a window, the default binding |
| 62 | tags provide the following behavior: |
| 63 | |
| 64 | If a tag is the name of an internal window the binding applies |
| 65 | to that window. |
| 66 | |
| 67 | If the tag is the name of a toplevel window the binding applies |
| 68 | to the toplevel window and all its internal windows. |
| 69 | |
| 70 | If the tag is the name of a class of widgets, such as B<Tk::Button>, |
| 71 | the binding applies to all widgets in that class; |
| 72 | |
| 73 | If I<tag> has the value B<all>, |
| 74 | the binding applies to all windows descended from the MainWindow |
| 75 | of the application. |
| 76 | |
| 77 | =head1 EVENT PATTERNS |
| 78 | |
| 79 | The I<sequence> argument specifies a sequence of one or more |
| 80 | event patterns, with optional white space between the patterns. Each |
| 81 | event pattern has the following syntax: |
| 82 | |
| 83 | S< >'<modifier-modifier-type-detail>' |
| 84 | |
| 85 | The entire event pattern is surrounded by angle brackets, and normally |
| 86 | needs to be quoted, as angle brackets are special to perl. |
| 87 | Inside the angle brackets are zero or more modifiers, an event |
| 88 | type, and an extra piece of information (I<detail>) identifying |
| 89 | a particular button or keysym. Any of the fields may be omitted, |
| 90 | as long as at least one of I<type> and I<detail> is present. |
| 91 | The fields must be separated by white space or dashes. |
| 92 | |
| 93 | A second form of pattern is used to specify a user-defined, named virtual |
| 94 | event; see L<Tk::event> for details. It has the following syntax: |
| 95 | |
| 96 | S< ><<name>> |
| 97 | |
| 98 | The entire virtual event pattern is surrounded by double angle brackets. |
| 99 | Inside the angle brackets is the user-defined name of the virtual event. |
| 100 | Modifiers, such as B<Shift> or B<Control>, may not be combined with a |
| 101 | virtual event to modify it. Bindings on a virtual event may be created |
| 102 | before the virtual event is defined, and if the definition of a virtual |
| 103 | event changes dynamically, all windows bound to that virtual event will |
| 104 | respond immediately to the new definition. |
| 105 | |
| 106 | =head1 MODIFIERS |
| 107 | |
| 108 | Modifiers consist of any of the following values: |
| 109 | |
| 110 | Control Mod2, M2 |
| 111 | Shift Mod3, M3 |
| 112 | Lock Mod4, M4 |
| 113 | Button1, B1 Mod5, M5 |
| 114 | Button2, B2 Meta, M |
| 115 | Button3, B3 Alt |
| 116 | Button4, B4 Double |
| 117 | Button5, B5 Triple |
| 118 | Mod1, M1 |
| 119 | |
| 120 | Where more than one value is listed, separated by commas, the values |
| 121 | are equivalent. |
| 122 | Most of the modifiers have the obvious X meanings. |
| 123 | For example, B<Button1> requires that |
| 124 | button 1 be depressed when the event occurs. |
| 125 | For a binding to match a given event, the modifiers in the event |
| 126 | must include all of those specified in the event pattern. |
| 127 | An event may also contain additional modifiers not specified in |
| 128 | the binding. |
| 129 | For example, if button 1 is pressed while the shift and control keys |
| 130 | are down, the pattern B<E<lt>Control-Button-1E<gt>> will match |
| 131 | the event, but B<E<lt>Mod1-Button-1E<gt>> will not. |
| 132 | If no modifiers are specified, then any combination of modifiers may |
| 133 | be present in the event. |
| 134 | |
| 135 | B<Meta> and B<M> refer to whichever of the |
| 136 | B<M1> through B<M5> modifiers is associated with the meta |
| 137 | key(s) on the keyboard (keysyms B<Meta_R> and B<Meta_L>). |
| 138 | If there are no meta keys, or if they are not associated with any |
| 139 | modifiers, then B<Meta> and B<M> will not match any events. |
| 140 | Similarly, the B<Alt> modifier refers to whichever modifier |
| 141 | is associated with the alt key(s) on the keyboard (keysyms |
| 142 | B<Alt_L> and B<Alt_R>). |
| 143 | |
| 144 | The B<Double> and B<Triple> modifiers are a convenience |
| 145 | for specifying double mouse clicks and other repeated |
| 146 | events. They cause a particular event pattern to be |
| 147 | repeated 2 or 3 times, and also place a time and space requirement |
| 148 | on the sequence: for a sequence of events to match a B<Double> |
| 149 | or B<Triple> pattern, all of the events must occur close together |
| 150 | in time and without substantial mouse motion in between. |
| 151 | For example, B<E<lt>Double-Button-1E<gt>> |
| 152 | is equivalent to B<E<lt>Button-1E<gt>E<lt>Button-1E<gt>> with the extra |
| 153 | time and space requirement. |
| 154 | |
| 155 | =head1 EVENT TYPES |
| 156 | |
| 157 | The I<type> field may be any of the standard X event types, with a |
| 158 | few extra abbreviations. Below is a list of all the valid types; |
| 159 | where two names appear together, they are synonyms. |
| 160 | |
| 161 | ButtonPress, Button Expose Map |
| 162 | ButtonRelease FocusIn Motion |
| 163 | Circulate FocusOut Property |
| 164 | Colormap Gravity Reparent |
| 165 | Configure KeyPress, Key Unmap |
| 166 | Destroy KeyRelease Visibility |
| 167 | Enter Leave Activate |
| 168 | Deactivate |
| 169 | |
| 170 | The last part of a long event specification is I<detail>. In the |
| 171 | case of a B<ButtonPress> or B<ButtonRelease> event, it is the |
| 172 | number of a button (1-5). If a button number is given, then only an |
| 173 | event on that particular button will match; if no button number is |
| 174 | given, then an event on any button will match. Note: giving a |
| 175 | specific button number is different than specifying a button modifier; |
| 176 | in the first case, it refers to a button being pressed or released, |
| 177 | while in the second it refers to some other button that is already |
| 178 | depressed when the matching event occurs. If a button |
| 179 | number is given then I<type> may be omitted: if will default |
| 180 | to B<ButtonPress>. For example, the specifier B<E<lt>1E<gt>> |
| 181 | is equivalent to B<E<lt>ButtonPress-1E<gt>>. |
| 182 | |
| 183 | If the event type is B<KeyPress> or B<KeyRelease>, then |
| 184 | I<detail> may be specified in the form of an X keysym. Keysyms |
| 185 | are textual specifications for particular keys on the keyboard; |
| 186 | they include all the alphanumeric ASCII characters (e.g. ``a'' is |
| 187 | the keysym for the ASCII character ``a''), plus descriptions for |
| 188 | non-alphanumeric characters (``comma'' is the keysym for the comma |
| 189 | character), plus descriptions for all the non-ASCII keys on the |
| 190 | keyboard (``Shift_L'' is the keysm for the left shift key, and |
| 191 | ``F1'' is the keysym for the F1 function key, if it exists). The |
| 192 | complete list of keysyms is not presented here; it is |
| 193 | available in other X documentation and may vary from system to |
| 194 | system. |
| 195 | If necessary, you can use the B<'K'> notation described below |
| 196 | to print out the keysym name for a particular key. |
| 197 | If a keysym I<detail> is given, then the |
| 198 | I<type> field may be omitted; it will default to B<KeyPress>. |
| 199 | For example, B<E<lt>Control-commaE<gt>> is equivalent to |
| 200 | B<E<lt>Control-KeyPress-commaE<gt>>. |
| 201 | |
| 202 | =head1 BINDING CALLBACKS AND SUBSTITUTIONS |
| 203 | |
| 204 | The I<callback> argument to B<bind> is a perl/Tk callback. |
| 205 | which will be executed whenever the given event sequence occurs. |
| 206 | (See L<Tk::callbacks> for description of the possible forms.) |
| 207 | I<Callback> will be associated with the same B<MainWindow> |
| 208 | that is associated with the I<$widget> that was used to invoke |
| 209 | the B<bind> method, and it will run as though called from B<MainLoop>. |
| 210 | If I<callback> contains |
| 211 | any B<Ev>(I<%>) calls, then each "nested" B<Ev>(I<%>) |
| 212 | "callback" will be evaluated when the event occurs to form arguments |
| 213 | to be passed to the main I<callback>. |
| 214 | The replacement |
| 215 | depends on the character I<%>, as defined in the |
| 216 | list below. Unless otherwise indicated, the |
| 217 | replacement string is the numeric (decimal) value of the given field from |
| 218 | the current event. Perl/Tk has enhanced this mechanism slightly compared |
| 219 | to the comparable Tcl/Tk mechanism. The enhancements are not yet all |
| 220 | reflected in the list below. |
| 221 | Some of the substitutions are only valid for |
| 222 | certain types of events; if they are used for other types of events |
| 223 | the value substituted is undefined (not the same as B<undef>!). |
| 224 | |
| 225 | =over 4 |
| 226 | |
| 227 | =item B<'#'> |
| 228 | |
| 229 | The number of the last client request processed by the server |
| 230 | (the I<serial> field from the event). Valid for all event |
| 231 | types. |
| 232 | |
| 233 | =item B<'a'> |
| 234 | |
| 235 | The I<above> field from the event, |
| 236 | formatted as a hexadecimal number. |
| 237 | Valid only for B<Configure> events. |
| 238 | |
| 239 | =item B<'b'> |
| 240 | |
| 241 | The number of the button that was pressed or released. Valid only |
| 242 | for B<ButtonPress> and B<ButtonRelease> events. |
| 243 | |
| 244 | =item B<'c'> |
| 245 | |
| 246 | The I<count> field from the event. Valid only for B<Expose> events. |
| 247 | |
| 248 | =item B<'d'> |
| 249 | |
| 250 | The I<detail> field from the event. The B<'d'> is replaced by |
| 251 | a string identifying the detail. For B<Enter>, |
| 252 | B<Leave>, B<FocusIn>, and B<FocusOut> events, |
| 253 | the string will be one of the following: |
| 254 | |
| 255 | =over 8 |
| 256 | |
| 257 | NotifyAncestor NotifyNonlinearVirtual |
| 258 | NotifyDetailNone NotifyPointer |
| 259 | NotifyInferior NotifyPointerRoot |
| 260 | NotifyNonlinear NotifyVirtual |
| 261 | |
| 262 | For events other than these, the substituted string is undefined. |
| 263 | (Note that this is I<not> the same as Detail part of sequence |
| 264 | use to specify the event.) |
| 265 | |
| 266 | =back |
| 267 | |
| 268 | =item B<'f'> |
| 269 | |
| 270 | The I<focus> field from the event (B<0> or B<1>). Valid only |
| 271 | for B<Enter> and B<Leave> events. |
| 272 | |
| 273 | =item B<'h'> |
| 274 | |
| 275 | The I<height> field from the event. Valid only for B<Configure>, |
| 276 | B<Expose>, and B<GraphicsExpose> events. |
| 277 | |
| 278 | =item B<'k'> |
| 279 | |
| 280 | The I<keycode> field from the event. Valid only for B<KeyPress> |
| 281 | and B<KeyRelease> events. |
| 282 | |
| 283 | =item B<'m'> |
| 284 | |
| 285 | The I<mode> field from the event. The substituted string is one of |
| 286 | B<NotifyNormal>, B<NotifyGrab>, B<NotifyUngrab>, or |
| 287 | B<NotifyWhileGrabbed>. Valid only for B<EnterWindow>, |
| 288 | B<FocusIn>, B<FocusOut>, and B<LeaveWindow> events. |
| 289 | |
| 290 | =item B<'o'> |
| 291 | |
| 292 | The I<override_redirect> field from the event. Valid only for |
| 293 | B<Map>, B<Reparent>, and B<Configure> events. |
| 294 | |
| 295 | =item B<'p'> |
| 296 | |
| 297 | The I<place> field from the event, substituted as one of the |
| 298 | strings B<PlaceOnTop> or B<PlaceOnBottom>. Valid only |
| 299 | for B<Circulate> events. |
| 300 | |
| 301 | =item B<'s'> |
| 302 | |
| 303 | The I<state> field from the event. For B<ButtonPress>, |
| 304 | B<ButtonRelease>, B<Enter>, B<KeyPress>, B<KeyRelease>, |
| 305 | B<Leave>, and B<Motion> events, a decimal string |
| 306 | is substituted. For B<Visibility>, one of the strings |
| 307 | B<VisibilityUnobscured>, B<VisibilityPartiallyObscured>, |
| 308 | and B<VisibilityFullyObscured> is substituted. |
| 309 | |
| 310 | =item B<'t'> |
| 311 | |
| 312 | The I<time> field from the event. Valid only for events that |
| 313 | contain a I<time> field. |
| 314 | |
| 315 | =item B<'w'> |
| 316 | |
| 317 | The I<width> field from the event. Valid only for |
| 318 | B<Configure>, B<Expose>, and B<GraphicsExpose> events. |
| 319 | |
| 320 | =item B<'x'> |
| 321 | |
| 322 | The I<x> field from the event. Valid only for events containing |
| 323 | an I<x> field. |
| 324 | |
| 325 | =item B<'y'> |
| 326 | |
| 327 | The I<y> field from the event. Valid only for events containing |
| 328 | a I<y> field. |
| 329 | |
| 330 | =item B<'@'> |
| 331 | |
| 332 | The string "@I<x,y>" where I<x> and I<y> are as above. |
| 333 | Valid only for events containing I<x> and I<y> fields. |
| 334 | This format is used my methods of B<Tk::Text> and similar widgets. |
| 335 | |
| 336 | =item B<'A'> |
| 337 | |
| 338 | Substitutes the ASCII character corresponding to the event, or |
| 339 | the empty string if the event doesn't correspond to an ASCII character |
| 340 | (e.g. the shift key was pressed). B<XLookupString> does all the |
| 341 | work of translating from the event to an ASCII character. |
| 342 | Valid only for B<KeyPress> and B<KeyRelease> events. |
| 343 | |
| 344 | =item B<'B'> |
| 345 | |
| 346 | The I<border_width> field from the event. Valid only for |
| 347 | B<Configure> events. |
| 348 | |
| 349 | =item B<'E'> |
| 350 | |
| 351 | The I<send_event> field from the event. Valid for all event types. |
| 352 | |
| 353 | =item B<'K'> |
| 354 | |
| 355 | The keysym corresponding to the event, substituted as a textual |
| 356 | string. Valid only for B<KeyPress> and B<KeyRelease> events. |
| 357 | |
| 358 | =item B<'N'> |
| 359 | |
| 360 | The keysym corresponding to the event, substituted as |
| 361 | a decimal |
| 362 | number. Valid only for B<KeyPress> and B<KeyRelease> events. |
| 363 | |
| 364 | =item B<'R'> |
| 365 | |
| 366 | The I<root> window identifier from the event. Valid only for |
| 367 | events containing a I<root> field. |
| 368 | |
| 369 | =item B<'S'> |
| 370 | |
| 371 | The I<subwindow> window identifier from the event, |
| 372 | as an object if it is one otherwise as a hexadecimal number. |
| 373 | Valid only for events containing a I<subwindow> field. |
| 374 | |
| 375 | =item B<'T'> |
| 376 | |
| 377 | The I<type> field from the event. Valid for all event types. |
| 378 | |
| 379 | =item B<'W'> |
| 380 | |
| 381 | The window to which the event was reported (the |
| 382 | $widget field from the event) - as an perl/Tk object. |
| 383 | Valid for all event types. |
| 384 | |
| 385 | =item B<'X'> |
| 386 | |
| 387 | The I<x_root> field from the event. |
| 388 | If a virtual-root window manager is being used then the substituted |
| 389 | value is the corresponding x-coordinate in the virtual root. |
| 390 | Valid only for |
| 391 | B<ButtonPress>, B<ButtonRelease>, B<KeyPress>, B<KeyRelease>, |
| 392 | and B<Motion> events. |
| 393 | |
| 394 | =item B<'Y'> |
| 395 | |
| 396 | The I<y_root> field from the event. |
| 397 | If a virtual-root window manager is being used then the substituted |
| 398 | value is the corresponding y-coordinate in the virtual root. |
| 399 | Valid only for |
| 400 | B<ButtonPress>, B<ButtonRelease>, B<KeyPress>, B<KeyRelease>, |
| 401 | and B<Motion> events. |
| 402 | |
| 403 | =back |
| 404 | |
| 405 | =head1 MULTIPLE MATCHES |
| 406 | |
| 407 | It is possible for several bindings to match a given X event. |
| 408 | If the bindings are associated with different I<tag>'s, |
| 409 | then each of the bindings will be executed, in order. |
| 410 | By default, a class binding will be executed first, followed |
| 411 | by a binding for the widget, a binding for its toplevel, and |
| 412 | an B<all> binding. |
| 413 | The B<bindtags> method may be used to change this order for |
| 414 | a particular window or to associate additional binding tags with |
| 415 | the window. |
| 416 | |
| 417 | B<return> and B<Tk-E<gt>break> may be used inside a |
| 418 | callback to control the processing of matching callbacks. |
| 419 | If B<return> is invoked, then the current callback |
| 420 | is terminated but Tk will continue processing callbacks |
| 421 | associated with other I<tag>'s. |
| 422 | If B<Tk-E<gt>break> is invoked within a callback, |
| 423 | then that callback terminates and no other callbacks will be invoked |
| 424 | for the event. |
| 425 | (B<Tk-E<gt>break> is implemented via perl's B<die> with a special value |
| 426 | which is "caught" by the perl/Tk "glue" code.) |
| 427 | |
| 428 | If more than one binding matches a particular event and they |
| 429 | have the same I<tag>, then the most specific binding |
| 430 | is chosen and its callback is evaluated. |
| 431 | The following tests are applied, in order, to determine which of |
| 432 | several matching sequences is more specific: |
| 433 | (a) an event pattern that specifies a specific button or key is more specific |
| 434 | than one that doesn't; |
| 435 | (b) a longer sequence (in terms of number |
| 436 | of events matched) is more specific than a shorter sequence; |
| 437 | (c) if the modifiers specified in one pattern are a subset of the |
| 438 | modifiers in another pattern, then the pattern with more modifiers |
| 439 | is more specific. |
| 440 | (d) a virtual event whose physical pattern matches the sequence is less |
| 441 | specific than the same physical pattern that is not associated with a |
| 442 | virtual event. |
| 443 | (e) given a sequence that matches two or more virtual events, one |
| 444 | of the virtual events will be chosen, but the order is undefined. |
| 445 | |
| 446 | If the matching sequences contain more than one event, then tests |
| 447 | (c)-(e) are applied in order from the most recent event to the least recent |
| 448 | event in the sequences. If these tests fail to determine a winner, then the |
| 449 | most recently registered sequence is the winner. |
| 450 | |
| 451 | If there are two (or more) virtual events that are both triggered by the |
| 452 | same sequence, and both of those virtual events are bound to the same window |
| 453 | tag, then only one of the virtual events will be triggered, and it will |
| 454 | be picked at random: |
| 455 | |
| 456 | $widget->eventAdd('<<Paste>>' => '<Control-y>'); |
| 457 | $widget->eventAdd('<<Paste>>' => '<Button-2>'); |
| 458 | $widget->eventAdd <<Scroll>>' => '<Button-2>'); |
| 459 | $widget->bind('Tk::Entry','<<Paste>>',sub { print 'Paste'}); |
| 460 | $widget->bind('Tk::Entry','<<Scroll>>', sub {print 'Scroll'}); |
| 461 | |
| 462 | If the user types Control-y, the B<E<lt>E<lt>PasteE<gt>E<gt>> binding |
| 463 | will be invoked, but if the user presses button 2 then one of |
| 464 | either the B<E<lt>E<lt>PasteE<gt>E<gt>> or the B<E<lt>E<lt>ScrollE<gt>E<gt>> bindings will |
| 465 | be invoked, but exactly which one gets invoked is undefined. |
| 466 | |
| 467 | If an X event does not match any of the existing bindings, then the |
| 468 | event is ignored. |
| 469 | An unbound event is not considered to be an error. |
| 470 | |
| 471 | =head1 MULTI-EVENT SEQUENCES AND IGNORED EVENTS |
| 472 | |
| 473 | When a I<sequence> specified in a B<bind> method contains |
| 474 | more than one event pattern, then its callback is executed whenever |
| 475 | the recent events (leading up to and including the current event) |
| 476 | match the given sequence. This means, for example, that if button 1 is |
| 477 | clicked repeatedly the sequence B<E<lt>Double-ButtonPress-1E<gt>> will match |
| 478 | each button press but the first. |
| 479 | If extraneous events that would prevent a match occur in the middle |
| 480 | of an event sequence then the extraneous events are |
| 481 | ignored unless they are B<KeyPress> or B<ButtonPress> events. |
| 482 | For example, B<E<lt>Double-ButtonPress-1E<gt>> will match a sequence of |
| 483 | presses of button 1, even though there will be B<ButtonRelease> |
| 484 | events (and possibly B<Motion> events) between the |
| 485 | B<ButtonPress> events. |
| 486 | Furthermore, a B<KeyPress> event may be preceded by any number |
| 487 | of other B<KeyPress> events for modifier keys without the |
| 488 | modifier keys preventing a match. |
| 489 | For example, the event sequence B<aB> will match a press of the |
| 490 | B<a> key, a release of the B<a> key, a press of the B<Shift> |
| 491 | key, and a press of the B<b> key: the press of B<Shift> is |
| 492 | ignored because it is a modifier key. |
| 493 | Finally, if several B<Motion> events occur in a row, only |
| 494 | the last one is used for purposes of matching binding sequences. |
| 495 | |
| 496 | =head1 ERRORS |
| 497 | |
| 498 | If an error occurs in executing the callback for a binding then the |
| 499 | B<Tk::Error> mechanism is used to report the error. |
| 500 | The B<Tk::Error> mechanism will be executed at same call level, |
| 501 | and associated with the same B<MainWindow> as |
| 502 | as the callback was invoked. |
| 503 | |
| 504 | =head1 CAVEATS |
| 505 | |
| 506 | Note that for the B<Canvas> widget, the call to B<bind> has to be |
| 507 | fully qualified. This is because there is already a bind method for |
| 508 | the B<Canvas> widget, which binds individual canvas tags. |
| 509 | |
| 510 | S< >I<$canvas>-E<gt>B<Tk::bind> |
| 511 | |
| 512 | =head1 SEE ALSO |
| 513 | |
| 514 | L<Tk::Error|Tk::Error> |
| 515 | L<Tk::callbacks|Tk::callbacks> |
| 516 | L<Tk::bindtags|Tk::bindtags> |
| 517 | |
| 518 | =head1 KEYWORDS |
| 519 | |
| 520 | Event, binding |
| 521 | |
| 522 | =cut |
| 523 | |