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);
DESCRIPTIONSDL_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 sur-
face->pixels, using the pixel format stored in sur-
face->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 VALUESDL_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)
