| 1 | .TH "SDL_AddTimer" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" |
| 2 | .SH "NAME" |
| 3 | SDL_AddTimer \- Add a timer which will call a callback after the specified number of milliseconds has elapsed\&. |
| 4 | .SH "SYNOPSIS" |
| 5 | .PP |
| 6 | \fB#include "SDL\&.h" |
| 7 | .sp |
| 8 | \fBSDL_TimerID \fBSDL_AddTimer\fP\fR(\fBUint32 interval, SDL_NewTimerCallback callback, void *param\fR); |
| 9 | .SH "CALLBACK" |
| 10 | .PP |
| 11 | .nf |
| 12 | \f(CW/* type definition for the "new" timer callback function */ |
| 13 | typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);\fR |
| 14 | .fi |
| 15 | .PP |
| 16 | .SH "DESCRIPTION" |
| 17 | .PP |
| 18 | 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 \fBSDL_AddTimer\fP 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\&. |
| 19 | .PP |
| 20 | To cancel a currently running timer call \fISDL_RemoveTimer\fR with the timer ID returned from \fBSDL_AddTimer\fP\&. |
| 21 | .PP |
| 22 | 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 \fISDL_PushEvent\fR, however\&. |
| 23 | .PP |
| 24 | 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 \fBSDL_INIT_TIMER\fP to \fISDL_Init\fR\&. |
| 25 | .SH "RETURN VALUE" |
| 26 | .PP |
| 27 | Returns an ID value for the added timer or \fBNULL\fR if there was an error\&. |
| 28 | .SH "EXAMPLES" |
| 29 | .PP |
| 30 | .PP |
| 31 | .nf |
| 32 | \f(CWmy_timer_id = SDL_AddTimer((33/10)*10, my_callbackfunc, my_callback_param);\fR |
| 33 | .fi |
| 34 | .PP |
| 35 | .SH "SEE ALSO" |
| 36 | .PP |
| 37 | \fI\fBSDL_RemoveTimer\fP\fR, \fI\fBSDL_PushEvent\fP\fR |
| 38 | .\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01 |