Mercurial > sdl-ios-xcode
annotate docs/html/sdlblitsurface.html @ 765:4c2ba6161939
Editors Note: The original patch was modified to use SDL_Delay() instead of
nanosleep because nanosleep may not be portable to all systems
using SDL with the ALSA backend. This may be a moot point with
the switch to blocking writes anyway...
Date: Sat, 27 Dec 2003 21:47:36 +0100
From: Michel Daenzer
To: Debian Bug Tracking System
Subject: [SDL] Bug#225252: [PATCH] ALSA fixes
Package: libsdl1.2debian-all
Version: 1.2.6-2
Severity: normal
Tags: patch
For SDL 1.2.6, the ALSA backend was changed to call snd_pcm_open() with
SND_PCM_NONBLOCK. That's a good idea per se, however, it causes high CPU
usage, interrupted sound and stuttering in some games here. Taking a nanosleep
whenever snd_pcm_writei() returns -EAGAIN fixes this, but I think it's more
efficient to use blocking mode for the actual sound playback. Feedback from the
SDL and ALSA lists appreciated.
The patch also fixes the default ALSA device to be used.
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Sun, 04 Jan 2004 15:40:50 +0000 |
| parents | e5bc29de3f0a |
| children | 355632dca928 |
| rev | line source |
|---|---|
| 0 | 1 <HTML |
| 2 ><HEAD | |
| 3 ><TITLE | |
| 4 >SDL_BlitSurface</TITLE | |
| 5 ><META | |
| 6 NAME="GENERATOR" | |
|
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7 CONTENT="Modular DocBook HTML Stylesheet Version 1.64 |
| 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_ConvertSurface" | |
| 17 HREF="sdlconvertsurface.html"><LINK | |
| 18 REL="NEXT" | |
| 19 TITLE="SDL_FillRect" | |
| 20 HREF="sdlfillrect.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 | |
| 31 WIDTH="100%" | |
| 32 BORDER="0" | |
| 33 CELLPADDING="0" | |
| 34 CELLSPACING="0" | |
| 35 ><TR | |
| 36 ><TH | |
| 37 COLSPAN="3" | |
| 38 ALIGN="center" | |
| 39 >SDL Library Documentation</TH | |
| 40 ></TR | |
| 41 ><TR | |
| 42 ><TD | |
| 43 WIDTH="10%" | |
| 44 ALIGN="left" | |
| 45 VALIGN="bottom" | |
| 46 ><A | |
| 47 HREF="sdlconvertsurface.html" | |
| 48 >Prev</A | |
| 49 ></TD | |
| 50 ><TD | |
| 51 WIDTH="80%" | |
| 52 ALIGN="center" | |
| 53 VALIGN="bottom" | |
| 54 ></TD | |
| 55 ><TD | |
| 56 WIDTH="10%" | |
| 57 ALIGN="right" | |
| 58 VALIGN="bottom" | |
| 59 ><A | |
| 60 HREF="sdlfillrect.html" | |
| 61 >Next</A | |
| 62 ></TD | |
| 63 ></TR | |
| 64 ></TABLE | |
| 65 ><HR | |
| 66 ALIGN="LEFT" | |
| 67 WIDTH="100%"></DIV | |
| 68 ><H1 | |
| 69 ><A | |
| 70 NAME="SDLBLITSURFACE" | |
| 71 >SDL_BlitSurface</A | |
| 72 ></H1 | |
| 73 ><DIV | |
| 74 CLASS="REFNAMEDIV" | |
| 75 ><A | |
|
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76 NAME="AEN1915" |
| 0 | 77 ></A |
| 78 ><H2 | |
| 79 >Name</H2 | |
| 80 >SDL_BlitSurface -- This performs a fast blit from the source surface to the destination surface.</DIV | |
| 81 ><DIV | |
| 82 CLASS="REFSYNOPSISDIV" | |
| 83 ><A | |
|
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84 NAME="AEN1918" |
| 0 | 85 ></A |
| 86 ><H2 | |
| 87 >Synopsis</H2 | |
| 88 ><DIV | |
| 89 CLASS="FUNCSYNOPSIS" | |
| 90 ><A | |
|
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91 NAME="AEN1919" |
| 0 | 92 ></A |
| 93 ><P | |
| 94 ></P | |
| 95 ><PRE | |
| 96 CLASS="FUNCSYNOPSISINFO" | |
| 97 >#include "SDL.h"</PRE | |
| 98 ><P | |
| 99 ><CODE | |
| 100 ><CODE | |
| 101 CLASS="FUNCDEF" | |
| 102 >int <B | |
| 103 CLASS="FSFUNC" | |
| 104 >SDL_BlitSurface</B | |
| 105 ></CODE | |
| 106 >(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect);</CODE | |
| 107 ></P | |
| 108 ><P | |
| 109 ></P | |
| 110 ></DIV | |
| 111 ></DIV | |
| 112 ><DIV | |
| 113 CLASS="REFSECT1" | |
| 114 ><A | |
|
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115 NAME="AEN1925" |
| 0 | 116 ></A |
| 117 ><H2 | |
| 118 >Description</H2 | |
| 119 ><P | |
| 120 >This performs a fast blit from the source surface to the destination surface.</P | |
| 121 ><P | |
| 122 >Only the position is used in the <TT | |
| 123 CLASS="PARAMETER" | |
| 124 ><I | |
| 125 >dstrect</I | |
| 126 ></TT | |
| 127 > (the | |
| 128 width and height are ignored).</P | |
| 129 ><P | |
| 130 >If either <TT | |
| 131 CLASS="PARAMETER" | |
| 132 ><I | |
| 133 >srcrect</I | |
| 134 ></TT | |
| 135 > or | |
| 136 <TT | |
| 137 CLASS="PARAMETER" | |
| 138 ><I | |
| 139 >dstrect</I | |
| 140 ></TT | |
| 141 > are <TT | |
| 142 CLASS="LITERAL" | |
| 143 >NULL</TT | |
| 144 >, the entire | |
| 145 surface (<TT | |
| 146 CLASS="PARAMETER" | |
| 147 ><I | |
| 148 >src</I | |
| 149 ></TT | |
| 150 > or <TT | |
| 151 CLASS="PARAMETER" | |
| 152 ><I | |
| 153 >dst</I | |
| 154 ></TT | |
| 155 >) is | |
| 156 copied.</P | |
| 157 ><P | |
| 158 >The final blit rectangle is saved in | |
| 159 <TT | |
| 160 CLASS="PARAMETER" | |
| 161 ><I | |
| 162 >dstrect</I | |
| 163 ></TT | |
| 164 > after all clipping is performed | |
| 165 (<TT | |
| 166 CLASS="PARAMETER" | |
| 167 ><I | |
| 168 >srcrect</I | |
| 169 ></TT | |
| 170 > is not modified).</P | |
| 171 ><P | |
| 172 >The blit function should not be called on a locked surface.</P | |
| 173 ><P | |
| 174 >The results of blitting operations vary greatly depending on whether <TT | |
| 175 CLASS="LITERAL" | |
| 176 >SDL_SRCAPLHA</TT | |
| 177 > is set or not. See <A | |
| 178 HREF="sdlsetalpha.html" | |
| 179 >SDL_SetAlpha</A | |
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180 > for an explaination of how this affects your results. Colorkeying and alpha attributes also interact with surface blitting, as the following pseudo-code should hopefully explain. |
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181 <PRE |
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182 CLASS="PROGRAMLISTING" |
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183 >if (source surface has SDL_SRCALPHA set) { |
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184 if (source surface has alpha channel (that is, format->Amask != 0)) |
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185 blit using per-pixel alpha, ignoring any colour key |
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186 else { |
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187 if (source surface has SDL_SRCCOLORKEY set) |
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188 blit using the colour key AND the per-surface alpha value |
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189 else |
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190 blit using the per-surface alpha value |
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191 } |
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192 } else { |
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193 if (source surface has SDL_SRCCOLORKEY set) |
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194 blit using the colour key |
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195 else |
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196 ordinary opaque rectangular blit |
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197 }</PRE |
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198 ></P |
| 0 | 199 ></DIV |
| 200 ><DIV | |
| 201 CLASS="REFSECT1" | |
| 202 ><A | |
|
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203 NAME="AEN1944" |
| 0 | 204 ></A |
| 205 ><H2 | |
| 206 >Return Value</H2 | |
| 207 ><P | |
| 208 >If the blit is successful, it returns <SPAN | |
| 209 CLASS="RETURNVALUE" | |
| 210 >0</SPAN | |
| 211 >, | |
| 212 otherwise it returns <SPAN | |
| 213 CLASS="RETURNVALUE" | |
| 214 >-1</SPAN | |
| 215 >.</P | |
| 216 ><P | |
| 217 >If either of the surfaces were in video memory, and the blit returns | |
| 218 <SPAN | |
| 219 CLASS="RETURNVALUE" | |
| 220 >-2</SPAN | |
| 221 >, the video memory was lost, so it should be | |
| 222 reloaded with artwork and re-blitted: | |
| 223 <PRE | |
| 224 CLASS="PROGRAMLISTING" | |
| 225 > while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) { | |
| 226 while ( SDL_LockSurface(image)) < 0 ) | |
| 227 Sleep(10); | |
| 228 -- Write image pixels to image->pixels -- | |
| 229 SDL_UnlockSurface(image); | |
| 230 }</PRE | |
| 231 > | |
| 232 This happens under DirectX 5.0 when the system switches away from your | |
| 233 fullscreen application. Locking the surface will also fail until you | |
| 234 have access to the video memory again.</P | |
| 235 ></DIV | |
| 236 ><DIV | |
| 237 CLASS="REFSECT1" | |
| 238 ><A | |
|
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239 NAME="AEN1952" |
| 0 | 240 ></A |
| 241 ><H2 | |
| 242 >See Also</H2 | |
| 243 ><P | |
| 244 ><A | |
| 245 HREF="sdllocksurface.html" | |
| 246 ><TT | |
| 247 CLASS="FUNCTION" | |
| 248 >SDL_LockSurface</TT | |
| 249 ></A | |
| 250 >, | |
| 251 <A | |
| 252 HREF="sdlfillrect.html" | |
| 253 ><TT | |
| 254 CLASS="FUNCTION" | |
| 255 >SDL_FillRect</TT | |
| 256 ></A | |
| 257 >, | |
| 258 <A | |
| 259 HREF="sdlsurface.html" | |
| 260 ><SPAN | |
| 261 CLASS="STRUCTNAME" | |
| 262 >SDL_Surface</SPAN | |
| 263 ></A | |
| 264 >, | |
| 265 <A | |
| 266 HREF="sdlrect.html" | |
| 267 ><SPAN | |
| 268 CLASS="STRUCTNAME" | |
| 269 >SDL_Rect</SPAN | |
| 270 ></A | |
| 271 ></P | |
| 272 ></DIV | |
| 273 ><DIV | |
| 274 CLASS="NAVFOOTER" | |
| 275 ><HR | |
| 276 ALIGN="LEFT" | |
| 277 WIDTH="100%"><TABLE | |
| 278 WIDTH="100%" | |
| 279 BORDER="0" | |
| 280 CELLPADDING="0" | |
| 281 CELLSPACING="0" | |
| 282 ><TR | |
| 283 ><TD | |
| 284 WIDTH="33%" | |
| 285 ALIGN="left" | |
| 286 VALIGN="top" | |
| 287 ><A | |
| 288 HREF="sdlconvertsurface.html" | |
| 289 >Prev</A | |
| 290 ></TD | |
| 291 ><TD | |
| 292 WIDTH="34%" | |
| 293 ALIGN="center" | |
| 294 VALIGN="top" | |
| 295 ><A | |
| 296 HREF="index.html" | |
| 297 >Home</A | |
| 298 ></TD | |
| 299 ><TD | |
| 300 WIDTH="33%" | |
| 301 ALIGN="right" | |
| 302 VALIGN="top" | |
| 303 ><A | |
| 304 HREF="sdlfillrect.html" | |
| 305 >Next</A | |
| 306 ></TD | |
| 307 ></TR | |
| 308 ><TR | |
| 309 ><TD | |
| 310 WIDTH="33%" | |
| 311 ALIGN="left" | |
| 312 VALIGN="top" | |
| 313 >SDL_ConvertSurface</TD | |
| 314 ><TD | |
| 315 WIDTH="34%" | |
| 316 ALIGN="center" | |
| 317 VALIGN="top" | |
| 318 ><A | |
| 319 HREF="video.html" | |
| 320 >Up</A | |
| 321 ></TD | |
| 322 ><TD | |
| 323 WIDTH="33%" | |
| 324 ALIGN="right" | |
| 325 VALIGN="top" | |
| 326 >SDL_FillRect</TD | |
| 327 ></TR | |
| 328 ></TABLE | |
| 329 ></DIV | |
| 330 ></BODY | |
| 331 ></HTML | |
| 332 > |