diff options
Diffstat (limited to 'doc/DoOneEvent.3')
| -rw-r--r-- | doc/DoOneEvent.3 | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/doc/DoOneEvent.3 b/doc/DoOneEvent.3 new file mode 100644 index 0000000..d48afd0 --- /dev/null +++ b/doc/DoOneEvent.3 @@ -0,0 +1,106 @@ +'\" +'\" Copyright (c) 1990-1992 The Regents of the University of California. +'\" Copyright (c) 1994-1996 Sun Microsystems, Inc. +'\" +'\" See the file "license.terms" for information on usage and redistribution +'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. +'\" +.TH Tcl_DoOneEvent 3 7.5 Tcl "Tcl Library Procedures" +.so man.macros +.BS +.SH NAME +Tcl_DoOneEvent \- wait for events and invoke event handlers +.SH SYNOPSIS +.nf +\fB#include <tcl.h>\fR +.sp +int +\fBTcl_DoOneEvent\fR(\fIflags\fR) +.SH ARGUMENTS +.AS int flags +.AP int flags in +This parameter is normally zero. It may be an OR-ed combination +of any of the following flag bits: +\fBTCL_WINDOW_EVENTS\fR, \fBTCL_FILE_EVENTS\fR, +\fBTCL_TIMER_EVENTS\fR, \fBTCL_IDLE_EVENTS\fR, \fBTCL_ALL_EVENTS\fR, +or \fBTCL_DONT_WAIT\fR. +.BE + +.SH DESCRIPTION +.PP +This procedure is the entry point to Tcl's event loop; it is responsible for +waiting for events and dispatching event handlers created with +procedures such as \fBTk_CreateEventHandler\fR, \fBTcl_CreateFileHandler\fR, +\fBTcl_CreateTimerHandler\fR, and \fBTcl_DoWhenIdle\fR. +\fBTcl_DoOneEvent\fR checks to see if +events are already present on the Tcl event queue; if so, +it calls the handler(s) for the first (oldest) event, removes it from +the queue, and returns. +If there are no events ready to be handled, then \fBTcl_DoOneEvent\fR +checks for new events from all possible sources. +If any are found, it puts all of them on Tcl's event queue, calls +handlers for the first event on the queue, and returns. +If no events are found, \fBTcl_DoOneEvent\fR checks for \fBTcl_DoWhenIdle\fR +callbacks; if any are found, it invokes all of them and returns. +Finally, if no events or idle callbacks have been found, then +\fBTcl_DoOneEvent\fR sleeps until an event occurs; then it adds any +new events to the Tcl event queue, calls handlers for the first event, +and returns. +The normal return value is 1 to signify that some event +was processed (see below for other alternatives). +.PP +If the \fIflags\fR argument to \fBTcl_DoOneEvent\fR is non-zero, +it restricts the kinds of events that will be processed by +\fBTcl_DoOneEvent\fR. +\fIFlags\fR may be an OR-ed combination of any of the following bits: +.TP 27 +\fBTCL_WINDOW_EVENTS\fR \- +Process window system events. +.TP 27 +\fBTCL_FILE_EVENTS\fR \- +Process file events. +.TP 27 +\fBTCL_TIMER_EVENTS\fR \- +Process timer events. +.TP 27 +\fBTCL_IDLE_EVENTS\fR \- +Process idle callbacks. +.TP 27 +\fBTCL_ALL_EVENTS\fR \- +Process all kinds of events: equivalent to OR-ing together all of the +above flags or specifying none of them. +.TP 27 +\fBTCL_DONT_WAIT\fR \- +Do not sleep: process only events that are ready at the time of the +call. +.LP +If any of the flags \fBTCL_WINDOW_EVENTS\fR, \fBTCL_FILE_EVENTS\fR, +\fBTCL_TIMER_EVENTS\fR, or \fBTCL_IDLE_EVENTS\fR is set, then the only +events that will be considered are those for which flags are set. +Setting none of these flags is equivalent to the value +\fBTCL_ALL_EVENTS\fR, which causes all event types to be processed. +If an application has defined additional event sources with +\fBTcl_CreateEventSource\fR, then additional \fIflag\fR values +may also be valid, depending on those event sources. +.PP +The \fBTCL_DONT_WAIT\fR flag causes \fBTcl_DoOneEvent\fR not to put +the process to sleep: it will check for events but if none are found +then it returns immediately with a return value of 0 to indicate +that no work was done. +\fBTcl_DoOneEvent\fR will also return 0 without doing anything if +the only alternative is to block forever (this can happen, for example, +if \fIflags\fR is \fBTCL_IDLE_EVENTS\fR and there are no +\fBTcl_DoWhenIdle\fR callbacks pending, or if no event handlers or +timer handlers exist). +.PP +\fBTcl_DoOneEvent\fR may be invoked recursively. For example, +it is possible to invoke \fBTcl_DoOneEvent\fR recursively +from a handler called by \fBTcl_DoOneEvent\fR. This sort +of operation is useful in some modal situations, such +as when a +notification dialog has been popped up and an application wishes to +wait for the user to click a button in the dialog before +doing anything else. + +.SH KEYWORDS +callback, event, handler, idle, timer |