docs/man3/SDL_AddTimer.3
author Sam Lantinga <slouken@libsdl.org>
Sat, 29 Dec 2007 03:25:11 +0000
changeset 2283 546f7c1eb755
parent 181 e5bc29de3f0a
child 4311 1238da4a7112
permissions -rw-r--r--
Merged revision 3472 from SDL 1.2, fixing bug #493
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.TH "SDL_AddTimer" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 
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.SH "NAME"
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SDL_AddTimer \- Add a timer which will call a callback after the specified number of milliseconds has elapsed\&.
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.SH "SYNOPSIS"
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.PP
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\fB#include "SDL\&.h"
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.sp
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\fBSDL_TimerID \fBSDL_AddTimer\fP\fR(\fBUint32 interval, SDL_NewTimerCallback callback, void *param\fR);
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.SH "CALLBACK"
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.PP
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.nf
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\f(CW/* type definition for the "new" timer callback function */
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typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);\fR
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.fi
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.PP
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.SH "DESCRIPTION"
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.PP
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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\&.
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.PP
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To cancel a currently running timer call \fISDL_RemoveTimer\fR with the timer ID returned from \fBSDL_AddTimer\fP\&.
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.PP
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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\&.
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.PP
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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\&.
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.SH "RETURN VALUE"
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.PP
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Returns an ID value for the added timer or \fBNULL\fR if there was an error\&.
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.SH "EXAMPLES"
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.PP
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.PP
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.nf
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\f(CWmy_timer_id = SDL_AddTimer((33/10)*10, my_callbackfunc, my_callback_param);\fR
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.fi
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.PP
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.SH "SEE ALSO"
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.PP
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\fI\fBSDL_RemoveTimer\fP\fR, \fI\fBSDL_PushEvent\fP\fR
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...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01