## NAME

Tk_CreateTimerHandler, Tk_DeleteTimerHandler - call a procedure at a given time

## SYNOPSIS

#include <tk.h>

Tk_TimerToken Tk_CreateTimerHandler(milliseconds, proc, clientData)

Tk_DeleteTimerHandler(token)

## ARGUMENTS

`int milliseconds` (in)
  How many milliseconds to wait before invoking proc.
`Tk_TimerProc *proc` (in)
  Procedure to invoke after milliseconds have elapsed.
`ClientData clientData` (in)
  Arbitrary one-word value to pass to proc.
`Tk_TimerToken token` (in)
  Token for previously-created timer handler (the return value from some previous call to Tk_CreateTimerHandler).

## DESCRIPTION

Tk_CreateTimerHandler arranges for proc to be invoked at a time milliseconds milliseconds in the future. The callback to proc will be made by Tk_DoOneEvent, so Tk_CreateTimerHandler is only useful in programs that dispatch events through Tk_DoOneEvent or through other Tk procedures that call Tk_DoOneEvent, such as Tk_MainLoop. 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 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 proc, then the call to proc will be delayed.

Proc should have arguments and return value that match the type Tk_TimerProc:
typedef void Tk_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.

Tk_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 Tk_DeleteTimerHandler does nothing.

## KEYWORDS

callback, clock, handler, timer