.SH "SYNOPSIS"

.PP

\fB#include "SDL\&.h"

.sp

\fBint \fBSDL_LockSurface\fP\fR(\fBSDL_Surface *surface\fR);

.SH "DESCRIPTION"

.PP

\fBSDL_LockSurface\fP sets up a surface for directly accessing the pixels\&. Between calls to \fBSDL_LockSurface\fP and \fBSDL_UnlockSurface\fP, you can write to and read from \fBsurface->\fBpixels\fR\fR, using the pixel format stored in \fBsurface->\fBformat\fR\fR\&. Once you are done accessing the surface, you should use \fBSDL_UnlockSurface\fP to release it\&.

.PP

Not all surfaces require locking\&. If \fBSDL_MUSTLOCK\fP(\fBsurface\fR) evaluates to \fB0\fR, then you can read and write to the surface at any time, and the pixel format of the surface will not change\&.

.PP

No operating system or library calls should be made between lock/unlock pairs, as critical system locks may be held during this time\&.

.PP

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\&.

.PP

.nf

\f(CW \&.

\&.

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 */

\&.

\&.\fR

.fi

.PP

.SH "RETURN VALUE"

.PP

\fBSDL_LockSurface\fP returns \fB0\fR, or \fB-1\fR if the surface couldn\&'t be locked\&.

.SH "SEE ALSO"

.PP

\fI\fBSDL_UnlockSurface\fP\fR