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61 | ><A |
62 | HREF="sdlunlocksurface.html" |
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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 |
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