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author | Sam Lantinga <slouken@libsdl.org> |
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date | Sat, 10 Oct 2009 08:59:28 +0000 |
parents | 355632dca928 |
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<HTML ><HEAD ><TITLE >SDL_SetTimer</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="SDL Library Documentation" HREF="index.html"><LINK REL="UP" TITLE="Time" HREF="time.html"><LINK REL="PREVIOUS" TITLE="SDL_RemoveTimer" HREF="sdlremovetimer.html"></HEAD ><BODY CLASS="REFENTRY" BGCOLOR="#FFF8DC" TEXT="#000000" LINK="#0000ee" VLINK="#551a8b" ALINK="#ff0000" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SDL Library Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="sdlremovetimer.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" > </TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><H1 ><A NAME="SDLSETTIMER" ></A >SDL_SetTimer</H1 ><DIV CLASS="REFNAMEDIV" ><A NAME="AEN8557" ></A ><H2 >Name</H2 >SDL_SetTimer -- Set a callback to run after the specified number of milliseconds has elapsed.</DIV ><DIV CLASS="REFSYNOPSISDIV" ><A NAME="AEN8560" ></A ><H2 >Synopsis</H2 ><DIV CLASS="FUNCSYNOPSIS" ><A NAME="AEN8561" ></A ><P ></P ><PRE CLASS="FUNCSYNOPSISINFO" >#include "SDL.h"</PRE ><P ><CODE ><CODE CLASS="FUNCDEF" >int <B CLASS="FSFUNC" >SDL_SetTimer</B ></CODE >(Uint32 interval, SDL_TimerCallback callback);</CODE ></P ><P ></P ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="SDLTIMERCALLBACK" ></A ><H2 >Callback</H2 ><P >/* Function prototype for the timer callback function */ typedef Uint32 (*SDL_TimerCallback)(Uint32 interval);</P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN8570" ></A ><H2 >Description</H2 ><P >Set a callback to run after the specified number of milliseconds has elapsed. The callback function is passed the current timer interval and returns the next timer interval. If the returned value is the same as the one passed in, the periodic alarm continues, otherwise a new alarm is scheduled.</P ><P >To cancel a currently running timer, call <TT CLASS="FUNCTION" >SDL_SetTimer(0, NULL);</TT ></P ><P >The timer callback function may run in a different thread than your main constant, and so shouldn't call any functions from within itself.</P ><P >The maximum resolution of this timer is 10 ms, which 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).</P ><P >If you use this function, you need to pass <TT CLASS="LITERAL" >SDL_INIT_TIMER</TT > to <TT CLASS="FUNCTION" >SDL_Init()</TT >.</P ><DIV CLASS="NOTE" ><BLOCKQUOTE CLASS="NOTE" ><P ><B >Note: </B >This function is kept for compatibility but has been superseded by the new timer functions <A HREF="sdladdtimer.html" >SDL_AddTimer</A > and <A HREF="sdlremovetimer.html" >SDL_RemoveTimer</A > which support multiple timers.</P ></BLOCKQUOTE ></DIV ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN8584" ></A ><H2 >Examples</H2 ><P ><PRE CLASS="PROGRAMLISTING" >SDL_SetTimer((33/10)*10, my_callback);</PRE ></P ></DIV ><DIV CLASS="REFSECT1" ><A NAME="AEN8588" ></A ><H2 >See Also</H2 ><P ><A HREF="sdladdtimer.html" ><TT CLASS="FUNCTION" >SDL_AddTimer</TT ></A ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="sdlremovetimer.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" > </TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SDL_RemoveTimer</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="time.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" > </TD ></TR ></TABLE ></DIV ></BODY ></HTML >