NAME¶
SDL_AddTimer - Add a timer which will call a callback after the specified number
of milliseconds has elapsed.
SYNOPSIS¶
#include "SDL.h"
SDL_TimerID SDL_AddTimer(
Uint32 interval,
SDL_NewTimerCallback callback, void *param);
CALLBACK¶
/* type definition for the "new" timer callback function */
typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);
DESCRIPTION¶
Adds a callback function to be run after the specified number of milliseconds
has elapsed. The callback function is passed the current timer interval and
the user supplied parameter from the
SDL_AddTimer call and returns the
next timer interval. If the returned value from the callback is the same as
the one passed in, the periodic alarm continues, otherwise a new alarm is
scheduled.
To cancel a currently running timer call
SDL_RemoveTimer with the timer
ID returned from
SDL_AddTimer.
The timer callback function may run in a different thread than your main
program, and so shouldn't call any functions from within itself. You may
always call
SDL_PushEvent, however.
The granularity of the timer is platform-dependent, but you should count on it
being at least 10 ms as this is the most common number. This means that if you
request a 16 ms timer, your callback will run approximately 20 ms later on an
unloaded system. If you wanted to set a flag signaling a frame update at 30
frames per second (every 33 ms), you might set a timer for 30 ms (see example
below). If you use this function, you need to pass
SDL_INIT_TIMER to
SDL_Init.
RETURN VALUE¶
Returns an ID value for the added timer or
NULL if there was an error.
EXAMPLES¶
my_timer_id = SDL_AddTimer((33/10)*10, my_callbackfunc, my_callback_param);
SEE ALSO¶
SDL_RemoveTimer,
SDL_PushEvent