DRAFT

SDL_LockSurface

Use this function to set up a surface for directly accessing the pixels.

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.


CategoryAPI, CategorySurface

SDL_LockSurface (last edited 2010-08-09 18:57:23 by SheenaSmith)