(This is the legacy documentation for SDL2, the previous stable version; SDL3 is the current stable version.)

SDL_AddTimer

Call a callback function at a future time.

Header File

Syntax

SDL_TimerID SDL_AddTimer(Uint32 interval,
                         SDL_TimerCallback callback,
                         void *param);

Function Parameters

Uint32	interval	the timer delay, in milliseconds, passed to `callback`.
SDL_TimerCallback	callback	the SDL_TimerCallback function to call when the specified `interval` elapses.
void *	param	a pointer that is passed to `callback`.

Return Value

(SDL_TimerID) Returns a timer ID or 0 if an error occurs; call SDL_GetError() for more information.

Remarks

If you use this function, you must pass SDL_INIT_TIMER to SDL_Init().

The callback function is passed the current timer interval and the user supplied parameter from the SDL_AddTimer() call and should return the next timer interval. If the value returned from the callback is 0, the timer is canceled.

The callback is run on a separate thread.

Timers take into account the amount of time it took to execute the callback. For example, if the callback took 250 ms to execute and returned 1000 (ms), the timer would only wait another 750 ms before its next iteration.

Timing may be inexact due to OS scheduling. Be sure to note the current time with SDL_GetTicks() or SDL_GetPerformanceCounter() in case your callback needs to adjust for variances.

Version

This function is available since SDL 2.0.0.