[sdl_omap.git] / docs / html / sdllocksurface.html

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><H1
><A
NAME="SDLLOCKSURFACE"
></A
>SDL_LockSurface</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1919"
></A
><H2
>Name</H2
>SDL_LockSurface&nbsp;--&nbsp;Lock a surface for directly access.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN1922"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN1923"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_LockSurface</B
></CODE
>(SDL_Surface *surface);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1929"
></A
><H2
>Description</H2
><P
><TT
CLASS="FUNCTION"
>SDL_LockSurface</TT
> sets up a surface for directly 
accessing the pixels.  Between calls to <TT
CLASS="FUNCTION"
>SDL_LockSurface</TT
>
and <TT
CLASS="FUNCTION"
>SDL_UnlockSurface</TT
>, you can write to and read from 
<TT
CLASS="PARAMETER"
><I
>surface-&#62;<TT
CLASS="STRUCTFIELD"
><I
>pixels</I
></TT
></I
></TT
>, using the pixel format stored in
<TT
CLASS="PARAMETER"
><I
>surface-&#62;<TT
CLASS="STRUCTFIELD"
><I
>format</I
></TT
></I
></TT
>.  Once you are done accessing the
surface, you should use <TT
CLASS="FUNCTION"
>SDL_UnlockSurface</TT
> to release it.</P
><P
>Not all surfaces require locking.  
If <TT
CLASS="LITERAL"
>SDL_MUSTLOCK</TT
>(<TT
CLASS="PARAMETER"
><I
>surface</I
></TT
>)
evaluates to <SPAN
CLASS="RETURNVALUE"
>0</SPAN
>, then you can read and write to the 
surface at any time, and the pixel format of the surface will not change. </P
><P
>No operating system or library calls should be made between lock/unlock
pairs, as critical system locks may be held during this time.</P
><P
>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.
<PRE
CLASS="PROGRAMLISTING"
>    .
    .
    SDL_LockSurface( surface );
    .
    /* Surface is locked */
    /* Direct pixel access on surface here */
    .
    SDL_LockSurface( surface );
    .
    /* More direct pixel access on surface */
    .
    SDL_UnlockSurface( surface );
    /* Surface is still locked */
    /* Note: Is versions &#60; 1.1.8, the surface would have been */
    /* no longer locked at this stage                         */
    .
    SDL_UnlockSurface( surface );
    /* Surface is now unlocked */
    .
    .</PRE
></P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1947"
></A
><H2
>Return Value</H2
><P
><TT
CLASS="FUNCTION"
>SDL_LockSurface</TT
> returns <SPAN
CLASS="RETURNVALUE"
>0</SPAN
>, 
or <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> if the surface couldn't be locked.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1953"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlunlocksurface.html"
><TT
CLASS="FUNCTION"
>SDL_UnlockSurface</TT
></A
></P
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>
Commit	Line	Data
e14743d1	1	<HTML
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	3	><TITLE
	4	>SDL_LockSurface</TITLE
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	7	CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
	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
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	23	BGCOLOR="#FFF8DC"
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	25	LINK="#0000ee"
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	31	SUMMARY="Header navigation table"
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	40	>SDL Library Documentation</TH
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	44	WIDTH="10%"
	45	ALIGN="left"
	46	VALIGN="bottom"
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	60	VALIGN="bottom"
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	62	HREF="sdlunlocksurface.html"
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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
242	><DIV
243	CLASS="NAVFOOTER"
244	><HR
245	ALIGN="LEFT"
246	WIDTH="100%"><TABLE
247	SUMMARY="Footer navigation table"
248	WIDTH="100%"
249	BORDER="0"
250	CELLPADDING="0"
251	CELLSPACING="0"
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254	WIDTH="33%"
255	ALIGN="left"
256	VALIGN="top"
257	><A
258	HREF="sdlfreesurface.html"
259	ACCESSKEY="P"
260	>Prev</A
261	></TD
262	><TD
263	WIDTH="34%"
264	ALIGN="center"
265	VALIGN="top"
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267	HREF="index.html"
268	ACCESSKEY="H"
269	>Home</A
270	></TD
271	><TD
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273	ALIGN="right"
274	VALIGN="top"
275	><A
276	HREF="sdlunlocksurface.html"
277	ACCESSKEY="N"
278	>Next</A
279	></TD
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281	><TR
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284	ALIGN="left"
285	VALIGN="top"
286	>SDL_FreeSurface</TD
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290	VALIGN="top"
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292	HREF="video.html"
293	ACCESSKEY="U"
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	>