| 1 | <HTML |
| 2 | ><HEAD |
| 3 | ><TITLE |
| 4 | >SDL_LockSurface</TITLE |
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| 16 | TITLE="SDL_FreeSurface" |
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| 19 | TITLE="SDL_UnlockSurface" |
| 20 | HREF="sdlunlocksurface.html"></HEAD |
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| 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" |
| 49 | ACCESSKEY="P" |
| 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" |
| 63 | ACCESSKEY="N" |
| 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" |
| 74 | ></A |
| 75 | >SDL_LockSurface</H1 |
| 76 | ><DIV |
| 77 | CLASS="REFNAMEDIV" |
| 78 | ><A |
| 79 | NAME="AEN1919" |
| 80 | ></A |
| 81 | ><H2 |
| 82 | >Name</H2 |
| 83 | >SDL_LockSurface -- Lock a surface for directly access.</DIV |
| 84 | ><DIV |
| 85 | CLASS="REFSYNOPSISDIV" |
| 86 | ><A |
| 87 | NAME="AEN1922" |
| 88 | ></A |
| 89 | ><H2 |
| 90 | >Synopsis</H2 |
| 91 | ><DIV |
| 92 | CLASS="FUNCSYNOPSIS" |
| 93 | ><A |
| 94 | NAME="AEN1923" |
| 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 |
| 118 | NAME="AEN1929" |
| 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 |
| 204 | ></P |
| 205 | ></DIV |
| 206 | ><DIV |
| 207 | CLASS="REFSECT1" |
| 208 | ><A |
| 209 | NAME="AEN1947" |
| 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 |
| 229 | NAME="AEN1953" |
| 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 |
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| 256 | VALIGN="top" |
| 257 | ><A |
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| 272 | WIDTH="33%" |
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| 274 | VALIGN="top" |
| 275 | ><A |
| 276 | HREF="sdlunlocksurface.html" |
| 277 | ACCESSKEY="N" |
| 278 | >Next</A |
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| 286 | >SDL_FreeSurface</TD |
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| 294 | >Up</A |
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| 300 | >SDL_UnlockSurface</TD |
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| 306 | > |