sdl_locksurface(3) [centos man page]

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)

SDL_BlitSurface(3)						 SDL API Reference						SDL_BlitSurface(3)

NAME

       SDL_BlitSurface - This performs a fast blit from the source surface to the destination surface.

SYNOPSIS

       #include "SDL.h"

       int SDL_BlitSurface(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect);

DESCRIPTION

       This performs a fast blit from the source surface to the destination surface.

       Only the position is used in the dstrect (the width and height are ignored).

       If either srcrect or dstrect are NULL, the entire surface (src or dst) is copied.

       The final blit rectangle is saved in dstrect after all clipping is performed (srcrect is not modified).

       The blit function should not be called on a locked surface.

       The  results  of  blitting operations vary greatly depending on whether SDL_SRCAPLHA is set or not. See SDL_SetAlpha for an explaination of
       how this affects your results. Colorkeying and alpha attributes also interact with surface blitting, as the  following  pseudo-code  should
       hopefully explain.

       if (source surface has SDL_SRCALPHA set) {
	   if (source surface has alpha channel (that is, format->Amask != 0))
	       blit using per-pixel alpha, ignoring any colour key
	   else {
	       if (source surface has SDL_SRCCOLORKEY set)
		   blit using the colour key AND the per-surface alpha value
	       else
		   blit using the per-surface alpha value
	   }
       } else {
	   if (source surface has SDL_SRCCOLORKEY set)
	       blit using the colour key
	   else
	       ordinary opaque rectangular blit
       }

RETURN VALUE

       If the blit is successful, it returns 0, otherwise it returns -1.

       If  either  of the surfaces were in video memory, and the blit returns -2, the video memory was lost, so it should be reloaded with artwork
       and re-blitted:

	       while ( SDL_BlitSurface(image, imgrect, screen, dstrect) == -2 ) {
		       while ( SDL_LockSurface(image)) < 0 )
			       Sleep(10);
		       -- Write image pixels to image->pixels --
		       SDL_UnlockSurface(image);
	       }

	This happens under DirectX 5.0 when the system switches away from your fullscreen application. Locking the surface will  also  fail  until
       you have access to the video memory again.

SEE ALSO

       SDL_LockSurface, SDL_FillRect, SDL_Surface, SDL_Rect

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