SDL_LockSurface(3) SDL API Reference SDL_LockSurface(3)

NAME

SDL_LockSurface - Lock a surface for directly access.

SYNOPSIS

#include "SDL.h"

int SDL_LockSurface(SDL_Surface *surface);

DESCRIPTION

SDL_LockSurface sets up a surface for directly accessing the pixels.
Between calls to SDL_LockSurface and SDL_UnlockSurface, you can write
to and read from surface->pixels, using the pixel format stored in
surface->format. Once you are done accessing the surface, you should
use SDL_UnlockSurface to release it.

Not all surfaces require locking. If SDL_MUSTLOCK(surface) evaluates
to 0, then you can read and write to the surface at any time, and the
pixel format of the surface will not change.

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

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.

.
.
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 */
.
.

RETURN VALUE

SDL_LockSurface returns 0, or -1 if the surface couldn't be locked.

SEE ALSO

SDL_UnlockSurface

SDL Tue 11 Sep 2001, 23:01 SDL_LockSurface(3)