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Initial revision
author Sam Lantinga <slouken@lokigames.com>
date Thu, 26 Apr 2001 16:45:43 +0000
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children 55f1f1b3e27d
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-1:000000000000 0:74212992fb08
1 <HTML
2 ><HEAD
3 ><TITLE
4 >SDL_LockSurface</TITLE
5 ><META
6 NAME="GENERATOR"
7 CONTENT="Modular DocBook HTML Stylesheet Version 1.61
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
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="sdlfreesurface.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="sdlunlocksurface.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="SDLLOCKSURFACE"
71 >SDL_LockSurface</A
72 ></H1
73 ><DIV
74 CLASS="REFNAMEDIV"
75 ><A
76 NAME="AEN1435"
77 ></A
78 ><H2
79 >Name</H2
80 >SDL_LockSurface&nbsp;--&nbsp;Lock a surface for directly access.</DIV
81 ><DIV
82 CLASS="REFSYNOPSISDIV"
83 ><A
84 NAME="AEN1438"
85 ></A
86 ><H2
87 >Synopsis</H2
88 ><DIV
89 CLASS="FUNCSYNOPSIS"
90 ><A
91 NAME="AEN1439"
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_LockSurface</B
105 ></CODE
106 >(SDL_Surface *surface);</CODE
107 ></P
108 ><P
109 ></P
110 ></DIV
111 ></DIV
112 ><DIV
113 CLASS="REFSECT1"
114 ><A
115 NAME="AEN1445"
116 ></A
117 ><H2
118 >Description</H2
119 ><P
120 ><TT
121 CLASS="FUNCTION"
122 >SDL_LockSurface</TT
123 > sets up a surface for directly
124 accessing the pixels. Between calls to <TT
125 CLASS="FUNCTION"
126 >SDL_LockSurface</TT
127 >
128 and <TT
129 CLASS="FUNCTION"
130 >SDL_UnlockSurface</TT
131 >, you can write to and read from
132 <TT
133 CLASS="PARAMETER"
134 ><I
135 >surface-&#62;<TT
136 CLASS="STRUCTFIELD"
137 ><I
138 >pixels</I
139 ></TT
140 ></I
141 ></TT
142 >, using the pixel format stored in
143 <TT
144 CLASS="PARAMETER"
145 ><I
146 >surface-&#62;<TT
147 CLASS="STRUCTFIELD"
148 ><I
149 >format</I
150 ></TT
151 ></I
152 ></TT
153 >. Once you are done accessing the
154 surface, you should use <TT
155 CLASS="FUNCTION"
156 >SDL_UnlockSurface</TT
157 > to release it.</P
158 ><P
159 >Not all surfaces require locking.
160 If <TT
161 CLASS="LITERAL"
162 >SDL_MUSTLOCK</TT
163 >(<TT
164 CLASS="PARAMETER"
165 ><I
166 >surface</I
167 ></TT
168 >)
169 evaluates to <SPAN
170 CLASS="RETURNVALUE"
171 >0</SPAN
172 >, then you can read and write to the
173 surface at any time, and the pixel format of the surface will not change. </P
174 ><P
175 >No operating system or library calls should be made between lock/unlock
176 pairs, as critical system locks may be held during this time.</P
177 ><P
178 >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.
179 <PRE
180 CLASS="PROGRAMLISTING"
181 > .
182 .
183 SDL_LockSurface( surface );
184 .
185 /* Surface is locked */
186 /* Direct pixel access on surface here */
187 .
188 SDL_LockSurface( surface );
189 .
190 /* More direct pixel access on surface */
191 .
192 SDL_UnlockSurface( surface );
193 /* Surface is still locked */
194 /* Note: Is versions &#60; 1.1.8, the surface would have been */
195 /* no longer locked at this stage */
196 .
197 SDL_UnlockSurface( surface );
198 /* Surface is now unlocked */
199 .
200 .</PRE
201 >
202 </P
203 ></DIV
204 ><DIV
205 CLASS="REFSECT1"
206 ><A
207 NAME="AEN1463"
208 ></A
209 ><H2
210 >Return Value</H2
211 ><P
212 ><TT
213 CLASS="FUNCTION"
214 >SDL_LockSurface</TT
215 > returns <SPAN
216 CLASS="RETURNVALUE"
217 >0</SPAN
218 >,
219 or <SPAN
220 CLASS="RETURNVALUE"
221 >-1</SPAN
222 > if the surface couldn't be locked.</P
223 ></DIV
224 ><DIV
225 CLASS="REFSECT1"
226 ><A
227 NAME="AEN1469"
228 ></A
229 ><H2
230 >See Also</H2
231 ><P
232 ><A
233 HREF="sdlunlocksurface.html"
234 ><TT
235 CLASS="FUNCTION"
236 >SDL_UnlockSurface</TT
237 ></A
238 ></P
239 ></DIV
240 ><DIV
241 CLASS="NAVFOOTER"
242 ><HR
243 ALIGN="LEFT"
244 WIDTH="100%"><TABLE
245 WIDTH="100%"
246 BORDER="0"
247 CELLPADDING="0"
248 CELLSPACING="0"
249 ><TR
250 ><TD
251 WIDTH="33%"
252 ALIGN="left"
253 VALIGN="top"
254 ><A
255 HREF="sdlfreesurface.html"
256 >Prev</A
257 ></TD
258 ><TD
259 WIDTH="34%"
260 ALIGN="center"
261 VALIGN="top"
262 ><A
263 HREF="index.html"
264 >Home</A
265 ></TD
266 ><TD
267 WIDTH="33%"
268 ALIGN="right"
269 VALIGN="top"
270 ><A
271 HREF="sdlunlocksurface.html"
272 >Next</A
273 ></TD
274 ></TR
275 ><TR
276 ><TD
277 WIDTH="33%"
278 ALIGN="left"
279 VALIGN="top"
280 >SDL_FreeSurface</TD
281 ><TD
282 WIDTH="34%"
283 ALIGN="center"
284 VALIGN="top"
285 ><A
286 HREF="video.html"
287 >Up</A
288 ></TD
289 ><TD
290 WIDTH="33%"
291 ALIGN="right"
292 VALIGN="top"
293 >SDL_UnlockSurface</TD
294 ></TR
295 ></TABLE
296 ></DIV
297 ></BODY
298 ></HTML
299 >