Tcl_CreateTimerHandler(3) Tcl Library Procedures Tcl_CreateTimerHandler(3)

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NAME

Tcl_CreateTimerHandler, Tcl_DeleteTimerHandler - call a procedure at
a given time

SYNOPSIS

#include <tcl.h>

Tcl_TimerToken
Tcl_CreateTimerHandler(milliseconds, proc, clientData)

Tcl_DeleteTimerHandler(token)

ARGUMENTS

int milliseconds (in) How many milliseconds to
wait before invoking proc.

Tcl_TimerProc *proc (in) Procedure to invoke after
milliseconds have elapsed.

ClientData clientData (in) Arbitrary one-word value to
pass to proc.

Tcl_TimerToken token (in) Token for previously
created timer handler (the
return value from some
previous call to
Tcl_CreateTimerHandler).
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DESCRIPTION

Tcl_CreateTimerHandler arranges for proc to be invoked at a time
milliseconds milliseconds in the future. The callback to proc will
be made by Tcl_DoOneEvent, so Tcl_CreateTimerHandler is only useful
in programs that dispatch events through Tcl_DoOneEvent or through
Tcl commands such as vwait. The call to proc may not be made at the
exact time given by milliseconds: it will be made at the next
opportunity after that time. For example, if Tcl_DoOneEvent is not
called until long after the time has elapsed, or if there are other
pending events to process before the call to proc, then the call to
proc will be delayed.

Proc should have arguments and return value that match the type
Tcl_TimerProc:

typedef void Tcl_TimerProc(
ClientData clientData);

The clientData parameter to proc is a copy of the clientData argument
given to Tcl_CreateTimerHandler when the callback was created.
Typically, clientData points to a data structure containing
application-specific information about what to do in proc.

Tcl_DeleteTimerHandler may be called to delete a previously created
timer handler. It deletes the handler indicated by token so that no
call to proc will be made; if that handler no longer exists (e.g.
because the time period has already elapsed and proc has been invoked
then Tcl_DeleteTimerHandler does nothing. The tokens returned by
Tcl_CreateTimerHandler never have a value of NULL, so if NULL is
passed to Tcl_DeleteTimerHandler then the procedure does nothing.

SEE ALSO

after(n), Tcl_CreateFileHandler(3), Tcl_DoWhenIdle(3)

KEYWORDS

callback, clock, handler, timer

Tcl 7.5 Tcl_CreateTimerHandler(3)