| 1 | '\" |
| 2 | '\" Copyright (c) 1992 The Regents of the University of California. |
| 3 | '\" Copyright (c) 1994-1996 Sun Microsystems, Inc. |
| 4 | '\" |
| 5 | '\" See the file "license.terms" for information on usage and redistribution |
| 6 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
| 7 | '\" |
| 8 | '\" RCS: @(#) $Id: grab.n,v 1.2.26.1 2004/10/28 10:19:29 dkf Exp $ |
| 9 | '\" |
| 10 | '\" The definitions below are for supplemental macros used in Tcl/Tk |
| 11 | '\" manual entries. |
| 12 | '\" |
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| 40 | '\" of man pages. The first argument is ignored and used for recording |
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| 71 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ |
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| 73 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. |
| 74 | .if t .wh -1.3i ^B |
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| 77 | '\" # Start an argument description |
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| 206 | '\" # SO - start of list of standard options |
| 207 | .de SO |
| 208 | .SH "STANDARD OPTIONS" |
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| 218 | .LP |
| 219 | See the \\fBoptions\\fR manual entry for details on the standard options. |
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| 223 | .LP |
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| 226 | Command-Line Name: \\fB\\$1\\fR |
| 227 | Database Name: \\fB\\$2\\fR |
| 228 | Database Class: \\fB\\$3\\fR |
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| 230 | .IP |
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| 243 | .de UL |
| 244 | \\$1\l'|0\(ul'\\$2 |
| 245 | .. |
| 246 | .TH grab n "" Tk "Tk Built-In Commands" |
| 247 | .BS |
| 248 | '\" Note: do not modify the .SH NAME line immediately below! |
| 249 | .SH NAME |
| 250 | grab \- Confine pointer and keyboard events to a window sub-tree |
| 251 | .SH SYNOPSIS |
| 252 | \fBgrab \fR?\fB\-global\fR? \fIwindow\fR |
| 253 | .sp |
| 254 | \fBgrab \fIoption \fR?\fIarg arg \fR...? |
| 255 | .BE |
| 256 | |
| 257 | .SH DESCRIPTION |
| 258 | .PP |
| 259 | This command implements simple pointer and keyboard grabs for Tk. |
| 260 | Tk's grabs are different than the grabs |
| 261 | described in the Xlib documentation. |
| 262 | When a grab is set for a particular window, Tk restricts all pointer |
| 263 | events to the grab window and its descendants in Tk's window hierarchy. |
| 264 | Whenever the pointer is within the grab window's subtree, the pointer |
| 265 | will behave exactly the same as if there had been no grab at all |
| 266 | and all events will be reported in the normal fashion. |
| 267 | When the pointer is outside \fIwindow\fR's tree, button presses and |
| 268 | releases and |
| 269 | mouse motion events are reported to \fIwindow\fR, and window entry |
| 270 | and window exit events are ignored. |
| 271 | The grab subtree ``owns'' the pointer: |
| 272 | windows outside the grab subtree will be visible on the screen |
| 273 | but they will be insensitive until the grab is released. |
| 274 | The tree of windows underneath the grab window can include top-level |
| 275 | windows, in which case all of those top-level windows |
| 276 | and their descendants will continue to receive mouse events |
| 277 | during the grab. |
| 278 | .PP |
| 279 | Two forms of grabs are possible: local and global. |
| 280 | A local grab affects only the grabbing application: events will |
| 281 | be reported to other applications as if the grab had never occurred. |
| 282 | Grabs are local by default. |
| 283 | A global grab locks out all applications on the screen, |
| 284 | so that only the given subtree of the grabbing application will be |
| 285 | sensitive to pointer events (mouse button presses, mouse button releases, |
| 286 | pointer motions, window entries, and window exits). |
| 287 | During global grabs the window manager will not receive pointer |
| 288 | events either. |
| 289 | .PP |
| 290 | During local grabs, keyboard events (key presses and key releases) |
| 291 | are delivered as usual: the window |
| 292 | manager controls which application receives keyboard events, and |
| 293 | if they are sent to any window in the grabbing application then they are |
| 294 | redirected to the focus window. |
| 295 | During a global grab Tk grabs the keyboard so that all keyboard events |
| 296 | are always sent to the grabbing application. |
| 297 | The \fBfocus\fR command is still used to determine which window in the |
| 298 | application receives the keyboard events. |
| 299 | The keyboard grab is released when the grab is released. |
| 300 | .PP |
| 301 | Grabs apply to particular displays. If an application has windows |
| 302 | on multiple displays then it can establish a separate grab on each |
| 303 | display. |
| 304 | The grab on a particular display affects only the windows on |
| 305 | that display. |
| 306 | It is possible for different applications on a single display to have |
| 307 | simultaneous local grabs, but only one application can have a global |
| 308 | grab on a given display at once. |
| 309 | .PP |
| 310 | The \fBgrab\fR command can take any of the following forms: |
| 311 | .TP |
| 312 | \fBgrab \fR?\fB\-global\fR? \fIwindow\fR |
| 313 | Same as \fBgrab set\fR, described below. |
| 314 | .TP |
| 315 | \fBgrab current \fR?\fIwindow\fR? |
| 316 | If \fIwindow\fR is specified, returns the name of the current grab |
| 317 | window in this application for \fIwindow\fR's display, or an empty |
| 318 | string if there is no such window. |
| 319 | If \fIwindow\fR is omitted, the command returns a list whose elements |
| 320 | are all of the windows grabbed by this application for all displays, |
| 321 | or an empty string if the application has no grabs. |
| 322 | .TP |
| 323 | \fBgrab release \fIwindow\fR |
| 324 | Releases the grab on \fIwindow\fR if there is one, otherwise does |
| 325 | nothing. Returns an empty string. |
| 326 | .TP |
| 327 | \fBgrab set \fR?\fB\-global\fR? \fIwindow\fR |
| 328 | Sets a grab on \fIwindow\fR. If \fB\-global\fR is specified then the |
| 329 | grab is global, otherwise it is local. |
| 330 | If a grab was already in effect for this application on |
| 331 | \fIwindow\fR's display then it is automatically released. |
| 332 | If there is already a grab on \fIwindow\fR and it has the same |
| 333 | global/local form as the requested grab, then the command |
| 334 | does nothing. Returns an empty string. |
| 335 | .TP |
| 336 | \fBgrab status \fIwindow\fR |
| 337 | Returns \fBnone\fR if no grab is currently set on \fIwindow\fR, |
| 338 | \fBlocal\fR if a local grab is set on \fIwindow\fR, and |
| 339 | \fBglobal\fR if a global grab is set. |
| 340 | .SH WARNING |
| 341 | It is very easy to use global grabs to render a display completely |
| 342 | unusable (e.g. by setting a grab on a widget which does not respond to |
| 343 | events and not providing any mechanism for releasing the grab). Take |
| 344 | \fIextreme\fR care when using them! |
| 345 | .SH BUGS |
| 346 | .PP |
| 347 | It took an incredibly complex and gross implementation to produce |
| 348 | the simple grab effect described above. |
| 349 | Given the current implementation, it isn't safe for applications |
| 350 | to use the Xlib grab facilities at all except through the Tk grab |
| 351 | procedures. |
| 352 | If applications try to manipulate X's grab mechanisms directly, |
| 353 | things will probably break. |
| 354 | .PP |
| 355 | If a single process is managing several different Tk applications, |
| 356 | only one of those applications can have a local grab for a given |
| 357 | display at any given time. If the applications are in different |
| 358 | processes, this restriction doesn't exist. |
| 359 | .SH EXAMPLE |
| 360 | Set a grab so that only one button may be clicked out of a group. The |
| 361 | other buttons are unresponsive to the mouse until the middle button is |
| 362 | clicked. |
| 363 | .CS |
| 364 | pack [button .b1 \-text "Click me! #1" \-command {destroy .b1}] |
| 365 | pack [button .b2 \-text "Click me! #2" \-command {destroy .b2}] |
| 366 | pack [button .b3 \-text "Click me! #3" \-command {destroy .b3}] |
| 367 | \fBgrab\fR .b2 |
| 368 | .CE |
| 369 | |
| 370 | .SH KEYWORDS |
| 371 | grab, keyboard events, pointer events, window |