Mercurial > sdl-ios-xcode
annotate docs/html/sdllocksurface.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 |
| children |
| rev | line source |
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| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_LockSurface</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="Video" | |
| 14 HREF="video.html"><LINK | |
| 15 REL="PREVIOUS" | |
| 16 TITLE="SDL_FreeSurface" | |
| 17 HREF="sdlfreesurface.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_UnlockSurface" | |
| 20 HREF="sdlunlocksurface.html"></HEAD | |
| 21 ><BODY | |
| 22 CLASS="REFENTRY" | |
| 23 BGCOLOR="#FFF8DC" | |
| 24 TEXT="#000000" | |
| 25 LINK="#0000ee" | |
| 26 VLINK="#551a8b" | |
| 27 ALINK="#ff0000" | |
| 28 ><DIV | |
| 29 CLASS="NAVHEADER" | |
| 30 ><TABLE | |
|
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31 SUMMARY="Header navigation table" |
| 0 | 32 WIDTH="100%" |
| 33 BORDER="0" | |
| 34 CELLPADDING="0" | |
| 35 CELLSPACING="0" | |
| 36 ><TR | |
| 37 ><TH | |
| 38 COLSPAN="3" | |
| 39 ALIGN="center" | |
| 40 >SDL Library Documentation</TH | |
| 41 ></TR | |
| 42 ><TR | |
| 43 ><TD | |
| 44 WIDTH="10%" | |
| 45 ALIGN="left" | |
| 46 VALIGN="bottom" | |
| 47 ><A | |
| 48 HREF="sdlfreesurface.html" | |
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49 ACCESSKEY="P" |
| 0 | 50 >Prev</A |
| 51 ></TD | |
| 52 ><TD | |
| 53 WIDTH="80%" | |
| 54 ALIGN="center" | |
| 55 VALIGN="bottom" | |
| 56 ></TD | |
| 57 ><TD | |
| 58 WIDTH="10%" | |
| 59 ALIGN="right" | |
| 60 VALIGN="bottom" | |
| 61 ><A | |
| 62 HREF="sdlunlocksurface.html" | |
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63 ACCESSKEY="N" |
| 0 | 64 >Next</A |
| 65 ></TD | |
| 66 ></TR | |
| 67 ></TABLE | |
| 68 ><HR | |
| 69 ALIGN="LEFT" | |
| 70 WIDTH="100%"></DIV | |
| 71 ><H1 | |
| 72 ><A | |
| 73 NAME="SDLLOCKSURFACE" | |
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74 ></A |
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75 >SDL_LockSurface</H1 |
| 0 | 76 ><DIV |
| 77 CLASS="REFNAMEDIV" | |
| 78 ><A | |
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79 NAME="AEN1919" |
| 0 | 80 ></A |
| 81 ><H2 | |
| 82 >Name</H2 | |
| 83 >SDL_LockSurface -- Lock a surface for directly access.</DIV | |
| 84 ><DIV | |
| 85 CLASS="REFSYNOPSISDIV" | |
| 86 ><A | |
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87 NAME="AEN1922" |
| 0 | 88 ></A |
| 89 ><H2 | |
| 90 >Synopsis</H2 | |
| 91 ><DIV | |
| 92 CLASS="FUNCSYNOPSIS" | |
| 93 ><A | |
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94 NAME="AEN1923" |
| 0 | 95 ></A |
| 96 ><P | |
| 97 ></P | |
| 98 ><PRE | |
| 99 CLASS="FUNCSYNOPSISINFO" | |
| 100 >#include "SDL.h"</PRE | |
| 101 ><P | |
| 102 ><CODE | |
| 103 ><CODE | |
| 104 CLASS="FUNCDEF" | |
| 105 >int <B | |
| 106 CLASS="FSFUNC" | |
| 107 >SDL_LockSurface</B | |
| 108 ></CODE | |
| 109 >(SDL_Surface *surface);</CODE | |
| 110 ></P | |
| 111 ><P | |
| 112 ></P | |
| 113 ></DIV | |
| 114 ></DIV | |
| 115 ><DIV | |
| 116 CLASS="REFSECT1" | |
| 117 ><A | |
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118 NAME="AEN1929" |
| 0 | 119 ></A |
| 120 ><H2 | |
| 121 >Description</H2 | |
| 122 ><P | |
| 123 ><TT | |
| 124 CLASS="FUNCTION" | |
| 125 >SDL_LockSurface</TT | |
| 126 > sets up a surface for directly | |
| 127 accessing the pixels. Between calls to <TT | |
| 128 CLASS="FUNCTION" | |
| 129 >SDL_LockSurface</TT | |
| 130 > | |
| 131 and <TT | |
| 132 CLASS="FUNCTION" | |
| 133 >SDL_UnlockSurface</TT | |
| 134 >, you can write to and read from | |
| 135 <TT | |
| 136 CLASS="PARAMETER" | |
| 137 ><I | |
| 138 >surface-><TT | |
| 139 CLASS="STRUCTFIELD" | |
| 140 ><I | |
| 141 >pixels</I | |
| 142 ></TT | |
| 143 ></I | |
| 144 ></TT | |
| 145 >, using the pixel format stored in | |
| 146 <TT | |
| 147 CLASS="PARAMETER" | |
| 148 ><I | |
| 149 >surface-><TT | |
| 150 CLASS="STRUCTFIELD" | |
| 151 ><I | |
| 152 >format</I | |
| 153 ></TT | |
| 154 ></I | |
| 155 ></TT | |
| 156 >. Once you are done accessing the | |
| 157 surface, you should use <TT | |
| 158 CLASS="FUNCTION" | |
| 159 >SDL_UnlockSurface</TT | |
| 160 > to release it.</P | |
| 161 ><P | |
| 162 >Not all surfaces require locking. | |
| 163 If <TT | |
| 164 CLASS="LITERAL" | |
| 165 >SDL_MUSTLOCK</TT | |
| 166 >(<TT | |
| 167 CLASS="PARAMETER" | |
| 168 ><I | |
| 169 >surface</I | |
| 170 ></TT | |
| 171 >) | |
| 172 evaluates to <SPAN | |
| 173 CLASS="RETURNVALUE" | |
| 174 >0</SPAN | |
| 175 >, then you can read and write to the | |
| 176 surface at any time, and the pixel format of the surface will not change. </P | |
| 177 ><P | |
| 178 >No operating system or library calls should be made between lock/unlock | |
| 179 pairs, as critical system locks may be held during this time.</P | |
| 180 ><P | |
| 181 >It should be noted, that since SDL 1.1.8 surface locks are recursive. This means that you can lock a surface multiple times, but each lock must have a match unlock. | |
| 182 <PRE | |
| 183 CLASS="PROGRAMLISTING" | |
| 184 > . | |
| 185 . | |
| 186 SDL_LockSurface( surface ); | |
| 187 . | |
| 188 /* Surface is locked */ | |
| 189 /* Direct pixel access on surface here */ | |
| 190 . | |
| 191 SDL_LockSurface( surface ); | |
| 192 . | |
| 193 /* More direct pixel access on surface */ | |
| 194 . | |
| 195 SDL_UnlockSurface( surface ); | |
| 196 /* Surface is still locked */ | |
| 197 /* Note: Is versions < 1.1.8, the surface would have been */ | |
| 198 /* no longer locked at this stage */ | |
| 199 . | |
| 200 SDL_UnlockSurface( surface ); | |
| 201 /* Surface is now unlocked */ | |
| 202 . | |
| 203 .</PRE | |
|
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204 ></P |
| 0 | 205 ></DIV |
| 206 ><DIV | |
| 207 CLASS="REFSECT1" | |
| 208 ><A | |
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209 NAME="AEN1947" |
| 0 | 210 ></A |
| 211 ><H2 | |
| 212 >Return Value</H2 | |
| 213 ><P | |
| 214 ><TT | |
| 215 CLASS="FUNCTION" | |
| 216 >SDL_LockSurface</TT | |
| 217 > returns <SPAN | |
| 218 CLASS="RETURNVALUE" | |
| 219 >0</SPAN | |
| 220 >, | |
| 221 or <SPAN | |
| 222 CLASS="RETURNVALUE" | |
| 223 >-1</SPAN | |
| 224 > if the surface couldn't be locked.</P | |
| 225 ></DIV | |
| 226 ><DIV | |
| 227 CLASS="REFSECT1" | |
| 228 ><A | |
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229 NAME="AEN1953" |
| 0 | 230 ></A |
| 231 ><H2 | |
| 232 >See Also</H2 | |
| 233 ><P | |
| 234 ><A | |
| 235 HREF="sdlunlocksurface.html" | |
| 236 ><TT | |
| 237 CLASS="FUNCTION" | |
| 238 >SDL_UnlockSurface</TT | |
| 239 ></A | |
| 240 ></P | |
| 241 ></DIV | |
| 242 ><DIV | |
| 243 CLASS="NAVFOOTER" | |
| 244 ><HR | |
| 245 ALIGN="LEFT" | |
| 246 WIDTH="100%"><TABLE | |
|
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247 SUMMARY="Footer navigation table" |
| 0 | 248 WIDTH="100%" |
| 249 BORDER="0" | |
| 250 CELLPADDING="0" | |
| 251 CELLSPACING="0" | |
| 252 ><TR | |
| 253 ><TD | |
| 254 WIDTH="33%" | |
| 255 ALIGN="left" | |
| 256 VALIGN="top" | |
| 257 ><A | |
| 258 HREF="sdlfreesurface.html" | |
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259 ACCESSKEY="P" |
| 0 | 260 >Prev</A |
| 261 ></TD | |
| 262 ><TD | |
| 263 WIDTH="34%" | |
| 264 ALIGN="center" | |
| 265 VALIGN="top" | |
| 266 ><A | |
| 267 HREF="index.html" | |
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268 ACCESSKEY="H" |
| 0 | 269 >Home</A |
| 270 ></TD | |
| 271 ><TD | |
| 272 WIDTH="33%" | |
| 273 ALIGN="right" | |
| 274 VALIGN="top" | |
| 275 ><A | |
| 276 HREF="sdlunlocksurface.html" | |
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277 ACCESSKEY="N" |
| 0 | 278 >Next</A |
| 279 ></TD | |
| 280 ></TR | |
| 281 ><TR | |
| 282 ><TD | |
| 283 WIDTH="33%" | |
| 284 ALIGN="left" | |
| 285 VALIGN="top" | |
| 286 >SDL_FreeSurface</TD | |
| 287 ><TD | |
| 288 WIDTH="34%" | |
| 289 ALIGN="center" | |
| 290 VALIGN="top" | |
| 291 ><A | |
| 292 HREF="video.html" | |
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293 ACCESSKEY="U" |
| 0 | 294 >Up</A |
| 295 ></TD | |
| 296 ><TD | |
| 297 WIDTH="33%" | |
| 298 ALIGN="right" | |
| 299 VALIGN="top" | |
| 300 >SDL_UnlockSurface</TD | |
| 301 ></TR | |
| 302 ></TABLE | |
| 303 ></DIV | |
| 304 ></BODY | |
| 305 ></HTML | |
| 306 > |