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Diffstat (limited to 'tcl8.6/doc/DoWhenIdle.3')
-rw-r--r-- | tcl8.6/doc/DoWhenIdle.3 | 87 |
1 files changed, 87 insertions, 0 deletions
diff --git a/tcl8.6/doc/DoWhenIdle.3 b/tcl8.6/doc/DoWhenIdle.3 new file mode 100644 index 0000000..3e28b4d --- /dev/null +++ b/tcl8.6/doc/DoWhenIdle.3 @@ -0,0 +1,87 @@ +'\" +'\" Copyright (c) 1990 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_DoWhenIdle 3 7.5 Tcl "Tcl Library Procedures" +.so man.macros +.BS +.SH NAME +Tcl_DoWhenIdle, Tcl_CancelIdleCall \- invoke a procedure when there are no pending events +.SH SYNOPSIS +.nf +\fB#include <tcl.h>\fR +.sp +\fBTcl_DoWhenIdle\fR(\fIproc, clientData\fR) +.sp +\fBTcl_CancelIdleCall\fR(\fIproc, clientData\fR) +.SH ARGUMENTS +.AS Tcl_IdleProc clientData +.AP Tcl_IdleProc *proc in +Procedure to invoke. +.AP ClientData clientData in +Arbitrary one-word value to pass to \fIproc\fR. +.BE +.SH DESCRIPTION +.PP +\fBTcl_DoWhenIdle\fR arranges for \fIproc\fR to be invoked +when the application becomes idle. The application is +considered to be idle when \fBTcl_DoOneEvent\fR has been +called, could not find any events to handle, and is about +to go to sleep waiting for an event to occur. At this +point all pending \fBTcl_DoWhenIdle\fR handlers are +invoked. For each call to \fBTcl_DoWhenIdle\fR there will +be a single call to \fIproc\fR; after \fIproc\fR is +invoked the handler is automatically removed. +\fBTcl_DoWhenIdle\fR is only usable in programs that +use \fBTcl_DoOneEvent\fR to dispatch events. +.PP +\fIProc\fR should have arguments and result that match the +type \fBTcl_IdleProc\fR: +.PP +.CS +typedef void \fBTcl_IdleProc\fR( + ClientData \fIclientData\fR); +.CE +.PP +The \fIclientData\fR parameter to \fIproc\fR is a copy of the \fIclientData\fR +argument given to \fBTcl_DoWhenIdle\fR. Typically, \fIclientData\fR +points to a data structure containing application-specific information about +what \fIproc\fR should do. +.PP +\fBTcl_CancelIdleCall\fR +may be used to cancel one or more previous +calls to \fBTcl_DoWhenIdle\fR: if there is a \fBTcl_DoWhenIdle\fR +handler registered for \fIproc\fR and \fIclientData\fR, then it +is removed without invoking it. If there is more than one +handler on the idle list that refers to \fIproc\fR and \fIclientData\fR, +all of the handlers are removed. If no existing handlers match +\fIproc\fR and \fIclientData\fR then nothing happens. +.PP +\fBTcl_DoWhenIdle\fR is most useful in situations where +(a) a piece of work will have to be done but (b) it is +possible that something will happen in the near future +that will change what has to be done or require something +different to be done. \fBTcl_DoWhenIdle\fR allows the +actual work to be deferred until all pending events have +been processed. At this point the exact work to be done +will presumably be known and it can be done exactly once. +.PP +For example, \fBTcl_DoWhenIdle\fR might be used by an editor +to defer display updates until all pending commands have +been processed. Without this feature, redundant redisplays +might occur in some situations, such as the processing of +a command file. +.SH BUGS +.PP +At present it is not safe for an idle callback to reschedule itself +continuously. This will interact badly with certain features of Tk +that attempt to wait for all idle callbacks to complete. If you would +like for an idle callback to reschedule itself continuously, it is +better to use a timer handler with a zero timeout period. +.SH "SEE ALSO" +after(n), Tcl_CreateFileHandler(3), Tcl_CreateTimerHandler(3) +.SH KEYWORDS +callback, defer, idle callback |