.TH "SDL_LockSurface" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 

.SH "NAME"

SDL_LockSurface \- Lock a surface for directly access\&.

.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

...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01