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# Copyright (c) 1990 The Regents of the University of California.
# Copyright (c) 1994 Sun Microsystems, Inc.
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
#
# @(#) TimerHndlr.3 1.9 95/05/28 13:52:12
#
=head1 NAME
Tk_CreateTimerHandler, Tk_DeleteTimerHandler - call a procedure at a
given time
=for category C Programming
=head1 SYNOPSIS
B<#include E<lt>tk.hE<gt>>
Tk_TimerToken
B<Tk_CreateTimerHandler>(I<milliseconds, proc, clientData>)
B<Tk_DeleteTimerHandler>(I<token>)
=head1 ARGUMENTS
=over 4
=item int milliseconds (in)
How many milliseconds to wait before invoking I<proc>.
=item Tk_TimerProc *proc (in)
Procedure to invoke after I<milliseconds> have elapsed.
=item ClientData clientData (in)
Arbitrary one-word value to pass to I<proc>.
=item Tk_TimerToken token (in)
Token for previously-created timer handler (the return value
from some previous call to B<Tk_CreateTimerHandler>).
=back
=head1 DESCRIPTION
B<Tk_CreateTimerHandler> arranges for I<proc> to be
invoked at a time I<milliseconds> milliseconds in the
future.
The callback to I<proc> will be made by B<Tk_DoOneEvent>,
so B<Tk_CreateTimerHandler> is only useful in
programs that dispatch events
through B<Tk_DoOneEvent> or through other Tk procedures that
call B<Tk_DoOneEvent>, such as B<Tk_MainLoop>. The call
to I<proc> may not be made at the exact time given by
I<milliseconds>: it will be made at the next opportunity
after that time. For example, if B<Tk_DoOneEvent> isn't
called until long after the time has elapsed, or if there
are other pending events to process before the call to
I<proc>, then the call to I<proc> will be delayed.
I<Proc> should have arguments and return value that match
the type B<Tk_TimerProc>:
=over 4
typedef void Tk_TimerProc(ClientData I<clientData>);
=back
The I<clientData> parameter to I<proc> is a
copy of the I<clientData> argument given to
B<Tcl_CreateTimerHandler> when the callback
was created. Typically, I<clientData> points to a data
structure containing application-specific information about
what to do in I<proc>.
B<Tk_DeleteTimerHandler> may be called to delete a
previously-created timer handler. It deletes the handler
indicated by I<token> so that no call to I<proc>
will be made; if that handler no longer exists
(e.g. because the time period has already elapsed and I<proc>
has been invoked) then B<Tk_DeleteTimerHandler> does nothing.
=head1 KEYWORDS
callback, clock, handler, timer
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