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| Between calls to [[SDL_LockSurface]]() / [[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. | Between calls to [[SDL_LockSurface]]() / [[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. |
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SDL_LockSurface
Use this function to set up a surface for directly accessing the pixels.
Contents
Syntax
int SDL_LockSurface(SDL_Surface* surface)
Function Parameters
surface |
a pointer to the SDL_Surface to be locked |
Return Value
Returns 0, or -1 if the surface couldn't be locked; call SDL_GetError() for more information.
Code Examples
*
SDL_Surface* surface = NULL;
/* Assign a surface pointer to surface */
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: In versions < 1.1.8, the surface would have been */
/* no longer locked at this stage */
SDL_UnlockSurface( surface );
/* Surface is now unlocked */
SDL_FreeSurface( surface );
surface = NULL;
*
Remarks
Between calls to SDL_LockSurface() / 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.
