Mercurial > sdl-ios-xcode
annotate docs/html/sdlsettimer.html @ 1157:baf35853ad54
Date: Mon, 10 Oct 2005 13:09:32 +0300
From: Tommi Kyntola <tommi.kyntola@ray.fi>
To: sdl@libsdl.org
Subject: [SDL] [RFC] get_ticks broken on linux
It uses gettimeofday to calculate the timedifference.
Gettimeofday returns current time which is seldom monotonous.
This breaks SDL timer subsystem. (time callbacks and all that
get borked when the time difference ms is suddenly ~ 2^32)
I posted a message about this earlier but got no response.
Some thoughts on this matter would be appreciated.
(Or even an explanation for the lack of interest.)
A patch below would use the posix timers that have been around
since posix 93 and do provide a good source of monotonous time
on linux boxes (and on few others too).
The following patch is also availabe at:
http://www.hut.fi/u/tkyntola/SDL-1.2.9-clockfix.patch
It's against 1.2.9, but I can easily rediffit against
the cvs branch is needed.
cheers,
Tommi Kyntola tommi.kyntola@ray.fi
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Tue, 11 Oct 2005 18:16:12 +0000 |
| parents | 355632dca928 |
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| rev | line source |
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| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_SetTimer</TITLE | |
| 5 ><META | |
| 6 NAME="GENERATOR" | |
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ |
| 0 | 8 "><LINK |
| 9 REL="HOME" | |
| 10 TITLE="SDL Library Documentation" | |
| 11 HREF="index.html"><LINK | |
| 12 REL="UP" | |
| 13 TITLE="Time" | |
| 14 HREF="time.html"><LINK | |
| 15 REL="PREVIOUS" | |
| 16 TITLE="SDL_RemoveTimer" | |
| 17 HREF="sdlremovetimer.html"></HEAD | |
| 18 ><BODY | |
| 19 CLASS="REFENTRY" | |
| 20 BGCOLOR="#FFF8DC" | |
| 21 TEXT="#000000" | |
| 22 LINK="#0000ee" | |
| 23 VLINK="#551a8b" | |
| 24 ALINK="#ff0000" | |
| 25 ><DIV | |
| 26 CLASS="NAVHEADER" | |
| 27 ><TABLE | |
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28 SUMMARY="Header navigation table" |
| 0 | 29 WIDTH="100%" |
| 30 BORDER="0" | |
| 31 CELLPADDING="0" | |
| 32 CELLSPACING="0" | |
| 33 ><TR | |
| 34 ><TH | |
| 35 COLSPAN="3" | |
| 36 ALIGN="center" | |
| 37 >SDL Library Documentation</TH | |
| 38 ></TR | |
| 39 ><TR | |
| 40 ><TD | |
| 41 WIDTH="10%" | |
| 42 ALIGN="left" | |
| 43 VALIGN="bottom" | |
| 44 ><A | |
| 45 HREF="sdlremovetimer.html" | |
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46 ACCESSKEY="P" |
| 0 | 47 >Prev</A |
| 48 ></TD | |
| 49 ><TD | |
| 50 WIDTH="80%" | |
| 51 ALIGN="center" | |
| 52 VALIGN="bottom" | |
| 53 ></TD | |
| 54 ><TD | |
| 55 WIDTH="10%" | |
| 56 ALIGN="right" | |
| 57 VALIGN="bottom" | |
| 58 > </TD | |
| 59 ></TR | |
| 60 ></TABLE | |
| 61 ><HR | |
| 62 ALIGN="LEFT" | |
| 63 WIDTH="100%"></DIV | |
| 64 ><H1 | |
| 65 ><A | |
| 66 NAME="SDLSETTIMER" | |
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67 ></A |
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68 >SDL_SetTimer</H1 |
| 0 | 69 ><DIV |
| 70 CLASS="REFNAMEDIV" | |
| 71 ><A | |
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72 NAME="AEN8557" |
| 0 | 73 ></A |
| 74 ><H2 | |
| 75 >Name</H2 | |
| 76 >SDL_SetTimer -- Set a callback to run after the specified number of milliseconds has | |
| 77 elapsed.</DIV | |
| 78 ><DIV | |
| 79 CLASS="REFSYNOPSISDIV" | |
| 80 ><A | |
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81 NAME="AEN8560" |
| 0 | 82 ></A |
| 83 ><H2 | |
| 84 >Synopsis</H2 | |
| 85 ><DIV | |
| 86 CLASS="FUNCSYNOPSIS" | |
| 87 ><A | |
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88 NAME="AEN8561" |
| 0 | 89 ></A |
| 90 ><P | |
| 91 ></P | |
| 92 ><PRE | |
| 93 CLASS="FUNCSYNOPSISINFO" | |
| 94 >#include "SDL.h"</PRE | |
| 95 ><P | |
| 96 ><CODE | |
| 97 ><CODE | |
| 98 CLASS="FUNCDEF" | |
| 99 >int <B | |
| 100 CLASS="FSFUNC" | |
| 101 >SDL_SetTimer</B | |
| 102 ></CODE | |
| 103 >(Uint32 interval, SDL_TimerCallback callback);</CODE | |
| 104 ></P | |
| 105 ><P | |
| 106 ></P | |
| 107 ></DIV | |
| 108 ></DIV | |
| 109 ><DIV | |
| 110 CLASS="REFSECT1" | |
| 111 ><A | |
| 112 NAME="SDLTIMERCALLBACK" | |
| 113 ></A | |
| 114 ><H2 | |
| 115 >Callback</H2 | |
| 116 ><P | |
| 117 >/* Function prototype for the timer callback function */ | |
| 118 typedef Uint32 (*SDL_TimerCallback)(Uint32 interval);</P | |
| 119 ></DIV | |
| 120 ><DIV | |
| 121 CLASS="REFSECT1" | |
| 122 ><A | |
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123 NAME="AEN8570" |
| 0 | 124 ></A |
| 125 ><H2 | |
| 126 >Description</H2 | |
| 127 ><P | |
| 128 >Set a callback to run after the specified number of milliseconds has | |
| 129 elapsed. The callback function is passed the current timer interval | |
| 130 and returns the next timer interval. If the returned value is the | |
| 131 same as the one passed in, the periodic alarm continues, otherwise a | |
| 132 new alarm is scheduled.</P | |
| 133 ><P | |
| 134 >To cancel a currently running timer, call | |
| 135 <TT | |
| 136 CLASS="FUNCTION" | |
| 137 >SDL_SetTimer(0, NULL);</TT | |
| 138 ></P | |
| 139 ><P | |
| 140 >The timer callback function may run in a different thread than your | |
| 141 main constant, and so shouldn't call any functions from within itself.</P | |
| 142 ><P | |
| 143 >The maximum resolution of this timer is 10 ms, which means that if | |
| 144 you request a 16 ms timer, your callback will run approximately 20 ms | |
| 145 later on an unloaded system. If you wanted to set a flag signaling | |
| 146 a frame update at 30 frames per second (every 33 ms), you might set a | |
| 147 timer for 30 ms (see example below).</P | |
| 148 ><P | |
| 149 >If you use this function, you need to pass <TT | |
| 150 CLASS="LITERAL" | |
| 151 >SDL_INIT_TIMER</TT | |
| 152 > | |
| 153 to <TT | |
| 154 CLASS="FUNCTION" | |
| 155 >SDL_Init()</TT | |
| 156 >.</P | |
| 157 ><DIV | |
| 158 CLASS="NOTE" | |
| 159 ><BLOCKQUOTE | |
| 160 CLASS="NOTE" | |
| 161 ><P | |
| 162 ><B | |
| 163 >Note: </B | |
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164 >This function is kept for compatibility but has been superseded |
| 0 | 165 by the new timer functions |
| 166 <A | |
| 167 HREF="sdladdtimer.html" | |
| 168 >SDL_AddTimer</A | |
| 169 > and | |
| 170 <A | |
| 171 HREF="sdlremovetimer.html" | |
| 172 >SDL_RemoveTimer</A | |
| 173 > which support | |
| 174 multiple timers.</P | |
| 175 ></BLOCKQUOTE | |
| 176 ></DIV | |
| 177 ></DIV | |
| 178 ><DIV | |
| 179 CLASS="REFSECT1" | |
| 180 ><A | |
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181 NAME="AEN8584" |
| 0 | 182 ></A |
| 183 ><H2 | |
| 184 >Examples</H2 | |
| 185 ><P | |
| 186 ><PRE | |
| 187 CLASS="PROGRAMLISTING" | |
| 188 >SDL_SetTimer((33/10)*10, my_callback);</PRE | |
| 189 ></P | |
| 190 ></DIV | |
| 191 ><DIV | |
| 192 CLASS="REFSECT1" | |
| 193 ><A | |
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194 NAME="AEN8588" |
| 0 | 195 ></A |
| 196 ><H2 | |
| 197 >See Also</H2 | |
| 198 ><P | |
| 199 ><A | |
| 200 HREF="sdladdtimer.html" | |
| 201 ><TT | |
| 202 CLASS="FUNCTION" | |
| 203 >SDL_AddTimer</TT | |
| 204 ></A | |
| 205 ></P | |
| 206 ></DIV | |
| 207 ><DIV | |
| 208 CLASS="NAVFOOTER" | |
| 209 ><HR | |
| 210 ALIGN="LEFT" | |
| 211 WIDTH="100%"><TABLE | |
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212 SUMMARY="Footer navigation table" |
| 0 | 213 WIDTH="100%" |
| 214 BORDER="0" | |
| 215 CELLPADDING="0" | |
| 216 CELLSPACING="0" | |
| 217 ><TR | |
| 218 ><TD | |
| 219 WIDTH="33%" | |
| 220 ALIGN="left" | |
| 221 VALIGN="top" | |
| 222 ><A | |
| 223 HREF="sdlremovetimer.html" | |
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224 ACCESSKEY="P" |
| 0 | 225 >Prev</A |
| 226 ></TD | |
| 227 ><TD | |
| 228 WIDTH="34%" | |
| 229 ALIGN="center" | |
| 230 VALIGN="top" | |
| 231 ><A | |
| 232 HREF="index.html" | |
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233 ACCESSKEY="H" |
| 0 | 234 >Home</A |
| 235 ></TD | |
| 236 ><TD | |
| 237 WIDTH="33%" | |
| 238 ALIGN="right" | |
| 239 VALIGN="top" | |
| 240 > </TD | |
| 241 ></TR | |
| 242 ><TR | |
| 243 ><TD | |
| 244 WIDTH="33%" | |
| 245 ALIGN="left" | |
| 246 VALIGN="top" | |
| 247 >SDL_RemoveTimer</TD | |
| 248 ><TD | |
| 249 WIDTH="34%" | |
| 250 ALIGN="center" | |
| 251 VALIGN="top" | |
| 252 ><A | |
| 253 HREF="time.html" | |
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254 ACCESSKEY="U" |
| 0 | 255 >Up</A |
| 256 ></TD | |
| 257 ><TD | |
| 258 WIDTH="33%" | |
| 259 ALIGN="right" | |
| 260 VALIGN="top" | |
| 261 > </TD | |
| 262 ></TR | |
| 263 ></TABLE | |
| 264 ></DIV | |
| 265 ></BODY | |
| 266 ></HTML | |
| 267 > |