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>SDL_LockSurface< /TITLE
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>SDL Library Documentation< /TH
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>SDL_LockSurface< /H1
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>< A
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NAME="AEN1919"
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>< /A
>< H2
>Name< /H2
>SDL_LockSurface -- Lock a surface for directly access.< /DIV
>< DIV
CLASS="REFSYNOPSISDIV"
>< A
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NAME="AEN1922"
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>< /A
>< H2
>Synopsis< /H2
>< DIV
CLASS="FUNCSYNOPSIS"
>< A
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NAME="AEN1923"
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>< /A
>< P
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>< 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
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NAME="AEN1929"
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>< /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-> < TT
CLASS="STRUCTFIELD"
>< I
>pixels< /I
>< /TT
>< /I
>< /TT
>, using the pixel format stored in
< TT
CLASS="PARAMETER"
>< I
>surface-> < 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 < 1.1.8, the surface would have been */
/* no longer locked at this stage */
.
SDL_UnlockSurface( surface );
/* Surface is now unlocked */
.
.< /PRE
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>< A
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NAME="AEN1947"
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>< /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
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NAME="AEN1953"
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>< /A
>< H2
>See Also< /H2
>< P
>< A
HREF="sdlunlocksurface.html"
>< TT
CLASS="FUNCTION"
>SDL_UnlockSurface< /TT
>< /A
>< /P
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