forked from KolibriOS/kolibrios
288 lines
4.4 KiB
HTML
288 lines
4.4 KiB
HTML
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<HTML
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><HEAD
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><TITLE
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>SDL_AddTimer</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.64
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"><LINK
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REL="HOME"
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TITLE="SDL Library Documentation"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="Time"
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HREF="time.html"><LINK
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REL="PREVIOUS"
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TITLE="SDL_Delay"
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HREF="sdldelay.html"><LINK
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REL="NEXT"
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TITLE="SDL_RemoveTimer"
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HREF="sdlremovetimer.html"></HEAD
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><BODY
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CLASS="REFENTRY"
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BGCOLOR="#FFF8DC"
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TEXT="#000000"
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LINK="#0000ee"
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VLINK="#551a8b"
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ALINK="#ff0000"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>SDL Library Documentation</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="sdldelay.html"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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></TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="sdlremovetimer.html"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><H1
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><A
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NAME="SDLADDTIMER"
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>SDL_AddTimer</A
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></H1
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><DIV
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CLASS="REFNAMEDIV"
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><A
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NAME="AEN7933"
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></A
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><H2
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>Name</H2
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>SDL_AddTimer -- Add a timer which will call a callback after the specified number of milliseconds has
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elapsed.</DIV
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><DIV
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CLASS="REFSYNOPSISDIV"
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><A
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NAME="AEN7936"
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></A
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><H2
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>Synopsis</H2
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><DIV
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CLASS="FUNCSYNOPSIS"
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><A
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NAME="AEN7937"
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></A
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><P
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></P
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><PRE
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CLASS="FUNCSYNOPSISINFO"
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>#include "SDL.h"</PRE
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><P
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><CODE
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><CODE
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CLASS="FUNCDEF"
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>SDL_TimerID <B
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CLASS="FSFUNC"
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>SDL_AddTimer</B
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></CODE
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>(Uint32 interval, SDL_NewTimerCallback callback, void *param);</CODE
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></P
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><P
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></P
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></DIV
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="SDLNEWTIMERCALLBACK"
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></A
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><H2
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>Callback</H2
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><PRE
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CLASS="PROGRAMLISTING"
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>/* type definition for the "new" timer callback function */
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typedef Uint32 (*SDL_NewTimerCallback)(Uint32 interval, void *param);</PRE
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN7946"
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></A
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><H2
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>Description</H2
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><P
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>Adds a callback function to be run after the specified number of
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milliseconds has elapsed. The callback function is passed the current
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timer interval and the user supplied parameter from the
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<TT
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CLASS="FUNCTION"
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>SDL_AddTimer</TT
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> call and returns the next timer
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interval. If the returned value from the callback is the same as the one
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passed in, the periodic alarm continues, otherwise a new alarm is
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scheduled.</P
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><P
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>To cancel a currently running timer call
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<A
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HREF="sdlremovetimer.html"
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>SDL_RemoveTimer</A
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> with the
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timer ID returned from
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<TT
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CLASS="FUNCTION"
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>SDL_AddTimer</TT
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>.</P
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><P
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>The timer callback function may run in a different thread than your
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main program, and so shouldn't call any functions from within itself.
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You may always call <A
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HREF="sdlpushevent.html"
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>SDL_PushEvent</A
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>, however.</P
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><P
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>The granularity of the timer is platform-dependent, but you should count
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on it being at least 10 ms as this is the most common number.
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This means that if
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you request a 16 ms timer, your callback will run approximately 20 ms
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later on an unloaded system. If you wanted to set a flag signaling
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a frame update at 30 frames per second (every 33 ms), you might set a
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timer for 30 ms (see example below).
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If you use this function, you need to pass <TT
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CLASS="LITERAL"
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>SDL_INIT_TIMER</TT
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>
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to <A
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HREF="sdlinit.html"
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>SDL_Init</A
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>.</P
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN7958"
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></A
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><H2
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>Return Value</H2
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><P
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>Returns an ID value for the added timer or
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<SPAN
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CLASS="RETURNVALUE"
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>NULL</SPAN
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> if there was an error.</P
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN7962"
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></A
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><H2
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>Examples</H2
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><P
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><PRE
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CLASS="PROGRAMLISTING"
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>my_timer_id = SDL_AddTimer((33/10)*10, my_callbackfunc, my_callback_param);</PRE
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></P
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN7966"
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></A
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><H2
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>See Also</H2
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><P
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><A
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HREF="sdlremovetimer.html"
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><TT
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CLASS="FUNCTION"
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>SDL_RemoveTimer</TT
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></A
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>,
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<A
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HREF="sdlpushevent.html"
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><TT
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CLASS="FUNCTION"
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>SDL_PushEvent</TT
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></A
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></P
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="sdldelay.html"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="sdlremovetimer.html"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>SDL_Delay</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="time.html"
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>SDL_RemoveTimer</TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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>
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