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)