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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 |