2 '\" Copyright (c) 1989-1993 The Regents of the University of California.
3 '\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
5 '\" See the file "license.terms" for information on usage and redistribution
6 '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
8 .TH Tcl_AsyncCreate 3 7.0 Tcl "Tcl Library Procedures"
9 .\" The -*- nroff -*- definitions below are for supplemental macros used
10 .\" in Tcl/Tk manual entries.
12 .\" .AP type name in/out ?indent?
13 .\" Start paragraph describing an argument to a library procedure.
14 .\" type is type of argument (int, etc.), in/out is either "in", "out",
15 .\" or "in/out" to describe whether procedure reads or modifies arg,
16 .\" and indent is equivalent to second arg of .IP (shouldn't ever be
17 .\" needed; use .AS below instead)
20 .\" Give maximum sizes of arguments for setting tab stops. Type and
21 .\" name are examples of largest possible arguments that will be passed
22 .\" to .AP later. If args are omitted, default tab stops are used.
25 .\" Start box enclosure. From here until next .BE, everything will be
26 .\" enclosed in one large box.
29 .\" End of box enclosure.
32 .\" Begin code excerpt.
37 .\" .VS ?version? ?br?
38 .\" Begin vertical sidebar, for use in marking newly-changed parts
39 .\" of man pages. The first argument is ignored and used for recording
40 .\" the version when the .VS was added, so that the sidebars can be
41 .\" found and removed when they reach a certain age. If another argument
42 .\" is present, then a line break is forced before starting the sidebar.
45 .\" End of vertical sidebar.
48 .\" Begin an indented unfilled display.
51 .\" End of indented unfilled display.
54 .\" Start of list of standard options for a Tk widget. The manpage
55 .\" argument defines where to look up the standard options; if
56 .\" omitted, defaults to "options". The options follow on successive
57 .\" lines, in three columns separated by tabs.
60 .\" End of list of standard options for a Tk widget.
62 .\" .OP cmdName dbName dbClass
63 .\" Start of description of a specific option. cmdName gives the
64 .\" option's name as specified in the class command, dbName gives
65 .\" the option's name in the option database, and dbClass gives
66 .\" the option's class in the option database.
69 .\" Print arg1 underlined, then print arg2 normally.
72 .\" Print arg1 in quotes, then arg2 normally (for trailing punctuation).
75 .\" Print an open parenthesis, arg1 in quotes, then arg2 normally
76 .\" (for trailing punctuation) and then a closing parenthesis.
78 .\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
82 .\" # Start an argument description
86 . ie !"\\$2"" .TP \\n()Cu
91 \&\\$1 \\fI\\$2\\fP (\\$3)
104 .\" # define tabbing values for .AP
107 .if !"\\$1"" .nr )A \\w'\\$1'u+3n
110 .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
111 .nr )C \\n()Bu+\\w'(in/out)'u+2n
113 .AS Tcl_Interp Tcl_CreateInterp in/out
114 .\" # BS - start boxed text
115 .\" # ^y = starting y location
123 .if n \l'\\n(.lu\(ul'
126 .\" # BE - end boxed text (draw box now)
131 .ie n \l'\\n(^lu\(ul'
133 .\" Draw four-sided box normally, but don't draw top of
134 .\" box if the box started on an earlier page.
136 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
139 \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
146 .\" # VS - start vertical sidebar
147 .\" # ^Y = starting y location
148 .\" # ^v = 1 (for troff; for nroff this doesn't matter)
152 .ie n 'mc \s12\(br\s0
155 .\" # VE - end of vertical sidebar
163 \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n'
170 .\" # Special macro to handle page bottom: finish off current
171 .\" # box/sidebar if in box/sidebar mode, then invoked standard
172 .\" # page bottom macro.
179 .\" Draw three-sided box if this is the box's first page,
180 .\" draw two sides but no top otherwise.
181 .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
182 .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
185 .nr ^x \\n(^tu+1v-\\n(^Yu
186 \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
199 .\" # DS - begin display
205 .\" # DE - end display
211 .\" # SO - start of list of standard options
213 'ie '\\$1'' .ds So \\fBoptions\\fR
214 'el .ds So \\fB\\$1\\fR
215 .SH "STANDARD OPTIONS"
221 .\" # SE - end of list of standard options
226 See the \\*(So manual entry for details on the standard options.
228 .\" # OP - start of full description for a single option
233 Command-Line Name: \\fB\\$1\\fR
234 Database Name: \\fB\\$2\\fR
235 Database Class: \\fB\\$3\\fR
239 .\" # CS - begin code excerpt
245 .\" # CE - end code excerpt
250 .\" # UL - underline word
254 .\" # QW - apply quotation marks to word
256 .ie '\\*(lq'"' ``\\$1''\\$2
257 .\"" fix emacs highlighting
258 .el \\*(lq\\$1\\*(rq\\$2
260 .\" # PQ - apply parens and quotation marks to word
262 .ie '\\*(lq'"' (``\\$1''\\$2)\\$3
263 .\"" fix emacs highlighting
264 .el (\\*(lq\\$1\\*(rq\\$2)\\$3
266 .\" # QR - quoted range
268 .ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3
269 .\"" fix emacs highlighting
270 .el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3
272 .\" # MT - "empty" string
278 Tcl_AsyncCreate, Tcl_AsyncMark, Tcl_AsyncInvoke, Tcl_AsyncDelete, Tcl_AsyncReady \- handle asynchronous events
281 \fB#include <tcl.h>\fR
284 \fBTcl_AsyncCreate\fR(\fIproc, clientData\fR)
286 \fBTcl_AsyncMark\fR(\fIasync\fR)
289 \fBTcl_AsyncInvoke\fR(\fIinterp, code\fR)
291 \fBTcl_AsyncDelete\fR(\fIasync\fR)
294 \fBTcl_AsyncReady\fR()
296 .AS Tcl_AsyncHandler clientData
297 .AP Tcl_AsyncProc *proc in
298 Procedure to invoke to handle an asynchronous event.
299 .AP ClientData clientData in
300 One-word value to pass to \fIproc\fR.
301 .AP Tcl_AsyncHandler async in
302 Token for asynchronous event handler.
303 .AP Tcl_Interp *interp in
304 Tcl interpreter in which command was being evaluated when handler was
305 invoked, or NULL if handler was invoked when there was no interpreter
308 Completion code from command that just completed in \fIinterp\fR,
309 or 0 if \fIinterp\fR is NULL.
314 These procedures provide a safe mechanism for dealing with
315 asynchronous events such as signals.
316 If an event such as a signal occurs while a Tcl script is being
317 evaluated then it is not safe to take any substantive action to
319 For example, it is not safe to evaluate a Tcl script since the
320 interpreter may already be in the middle of evaluating a script;
321 it may not even be safe to allocate memory, since a memory
322 allocation could have been in progress when the event occurred.
323 The only safe approach is to set a flag indicating that the event
324 occurred, then handle the event later when the world has returned
325 to a clean state, such as after the current Tcl command completes.
327 \fBTcl_AsyncCreate\fR, \fBTcl_AsyncDelete\fR, and \fBTcl_AsyncReady\fR
328 are thread sensitive. They access and/or set a thread-specific data
329 structure in the event of a core built with \fI\-\-enable\-threads\fR. The token
330 created by \fBTcl_AsyncCreate\fR contains the needed thread information it
331 was called from so that calling \fBTcl_AsyncMark\fR(\fItoken\fR) will only yield
332 the origin thread into the asynchronous handler.
334 \fBTcl_AsyncCreate\fR creates an asynchronous handler and returns
336 The asynchronous handler must be created before
337 any occurrences of the asynchronous event that it is intended
338 to handle (it is not safe to create a handler at the time of
340 When an asynchronous event occurs the code that detects the event
341 (such as a signal handler) should call \fBTcl_AsyncMark\fR with the
342 token for the handler.
343 \fBTcl_AsyncMark\fR will mark the handler as ready to execute, but it
344 will not invoke the handler immediately.
345 Tcl will call the \fIproc\fR associated with the handler later, when
346 the world is in a safe state, and \fIproc\fR can then carry out
347 the actions associated with the asynchronous event.
348 \fIProc\fR should have arguments and result that match the
349 type \fBTcl_AsyncProc\fR:
352 typedef int \fBTcl_AsyncProc\fR(
353 ClientData \fIclientData\fR,
354 Tcl_Interp *\fIinterp\fR,
358 The \fIclientData\fR will be the same as the \fIclientData\fR
359 argument passed to \fBTcl_AsyncCreate\fR when the handler was
361 If \fIproc\fR is invoked just after a command has completed
362 execution in an interpreter, then \fIinterp\fR will identify
363 the interpreter in which the command was evaluated and
364 \fIcode\fR will be the completion code returned by that
366 The command's result will be present in the interpreter's result.
367 When \fIproc\fR returns, whatever it leaves in the interpreter's result
368 will be returned as the result of the command and the integer
369 value returned by \fIproc\fR will be used as the new completion
370 code for the command.
372 It is also possible for \fIproc\fR to be invoked when no interpreter
374 This can happen, for example, if an asynchronous event occurs while
375 the application is waiting for interactive input or an X event.
376 In this case \fIinterp\fR will be NULL and \fIcode\fR will be
377 0, and the return value from \fIproc\fR will be ignored.
379 The procedure \fBTcl_AsyncInvoke\fR is called to invoke all of the
380 handlers that are ready.
381 The procedure \fBTcl_AsyncReady\fR will return non-zero whenever any
382 asynchronous handlers are ready; it can be checked to avoid calls
383 to \fBTcl_AsyncInvoke\fR when there are no ready handlers.
384 Tcl calls \fBTcl_AsyncReady\fR after each command is evaluated
385 and calls \fBTcl_AsyncInvoke\fR if needed.
386 Applications may also call \fBTcl_AsyncInvoke\fR at interesting
387 times for that application.
388 For example, Tcl's event handler calls \fBTcl_AsyncReady\fR
389 after each event and calls \fBTcl_AsyncInvoke\fR if needed.
390 The \fIinterp\fR and \fIcode\fR arguments to \fBTcl_AsyncInvoke\fR
391 have the same meaning as for \fIproc\fR: they identify the active
392 interpreter, if any, and the completion code from the command
395 \fBTcl_AsyncDelete\fR removes an asynchronous handler so that
396 its \fIproc\fR will never be invoked again.
397 A handler can be deleted even when ready, and it will still
400 If multiple handlers become active at the same time, the
401 handlers are invoked in the order they were created (oldest
403 The \fIcode\fR and the interpreter's result for later handlers
404 reflect the values returned by earlier handlers, so that
405 the most recently created handler has last say about
406 the interpreter's result and completion code.
407 If new handlers become ready while handlers are executing,
408 \fBTcl_AsyncInvoke\fR will invoke them all; at each point it
409 invokes the highest-priority (oldest) ready handler, repeating
410 this over and over until there are no longer any ready handlers.
413 It is almost always a bad idea for an asynchronous event
414 handler to modify the interpreter's result or return a code different
415 from its \fIcode\fR argument.
416 This sort of behavior can disrupt the execution of scripts in
417 subtle ways and result in bugs that are extremely difficult
419 If an asynchronous event handler needs to evaluate Tcl scripts
420 then it should first save the interpreter's state by calling
421 \fBTcl_SaveInterpState\fR, passing in the \fIcode\fR argument.
422 When the asynchronous handler is finished it should restore
423 the interpreter's state by calling \fBTcl_RestoreInterpState\fR,
424 and then returning the \fIcode\fR argument.
427 asynchronous event, handler, signal, Tcl_SaveInterpState, thread