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