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| >SDL_AddTimer</H1 |
| ><DIV |
| CLASS="REFNAMEDIV" |
| ><A |
| NAME="AEN8482" |
| ></A |
| ><H2 |
| >Name</H2 |
| >SDL_AddTimer -- Add a timer which will call a callback after the specified number of milliseconds has |
| elapsed.</DIV |
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| CLASS="REFSYNOPSISDIV" |
| ><A |
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| >Synopsis</H2 |
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| ><PRE |
| CLASS="FUNCSYNOPSISINFO" |
| >#include "SDL.h"</PRE |
| ><P |
| ><CODE |
| ><CODE |
| CLASS="FUNCDEF" |
| >SDL_TimerID <B |
| CLASS="FSFUNC" |
| >SDL_AddTimer</B |
| ></CODE |
| >(Uint32 interval, SDL_NewTimerCallback callback, void *param);</CODE |
| ></P |
| ><P |
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| ><A |
| NAME="SDLNEWTIMERCALLBACK" |
| ></A |
| ><H2 |
| >Callback</H2 |
| ><PRE |
| CLASS="PROGRAMLISTING" |
| >/* type definition for the "new" timer callback function */ |
| typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);</PRE |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8495" |
| ></A |
| ><H2 |
| >Description</H2 |
| ><P |
| >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 |
| <TT |
| CLASS="FUNCTION" |
| >SDL_AddTimer</TT |
| > 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.</P |
| ><P |
| >To cancel a currently running timer call |
| <A |
| HREF="sdlremovetimer.html" |
| >SDL_RemoveTimer</A |
| > with the |
| timer ID returned from |
| <TT |
| CLASS="FUNCTION" |
| >SDL_AddTimer</TT |
| >.</P |
| ><P |
| >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 <A |
| HREF="sdlpushevent.html" |
| >SDL_PushEvent</A |
| >, however.</P |
| ><P |
| >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 <TT |
| CLASS="LITERAL" |
| >SDL_INIT_TIMER</TT |
| > |
| to <A |
| HREF="sdlinit.html" |
| >SDL_Init</A |
| >.</P |
| ></DIV |
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| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8507" |
| ></A |
| ><H2 |
| >Return Value</H2 |
| ><P |
| >Returns an ID value for the added timer or |
| <SPAN |
| CLASS="RETURNVALUE" |
| >NULL</SPAN |
| > if there was an error.</P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8511" |
| ></A |
| ><H2 |
| >Examples</H2 |
| ><P |
| ><PRE |
| CLASS="PROGRAMLISTING" |
| >my_timer_id = SDL_AddTimer((33/10)*10, my_callbackfunc, my_callback_param);</PRE |
| ></P |
| ></DIV |
| ><DIV |
| CLASS="REFSECT1" |
| ><A |
| NAME="AEN8515" |
| ></A |
| ><H2 |
| >See Also</H2 |
| ><P |
| ><A |
| HREF="sdlremovetimer.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_RemoveTimer</TT |
| ></A |
| >, |
| <A |
| HREF="sdlpushevent.html" |
| ><TT |
| CLASS="FUNCTION" |
| >SDL_PushEvent</TT |
| ></A |
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