[SDL] Flickering and division by zero in Windows

[Andre de Leiradella]

 >> >> >> I'm writing an SDL application but am having trouble with 
flickering.
 >> >> >> I tried all combinations of flags (SDL_SWSURFACE, SDL_HWSURFACE,
 >> >> >> SDL_DOUBLEBUF, SDL_NOFRAME, SDL_FULLSCREEN etc.) but with no luck.
 >> >> >>
 >> >> What about this one, any thoughts?

 >> Is it possible that you're drawing to one buffer and SDL_gfx is drawing
 >> to the other? Try removing SDL_DOUBLEBUF and see if it makes a 
difference.

I thought SDL handled the two buffers itself, exposing only one of them 
at a time to the host program. My program does the following:

1) blit the entire background on to the screen (SDL_BlitSurface)
2) draw the transparent rectangle on the screen covering a part of it 
(SDL_gfx's boxColor)
3) SDL_Flip or SDL_UpdateRect
4) Do it all again

I tried pretty much all combinations of SDL_SWSURFACE, SDL_HWSURFACE, 
SDL_DOUBLEBUF, SDL_NOFRAME and SDL_FULLSCREEN, all with SDL_UpdateRect 
and SDL_Flip. It flickered badly on all of them... :-(

 >> Also, if you need to touch pixels directly, SDL_HWSURFACE is probably
 >> going to slow you down...that's meant to be a speed boost if you're 
just
 >> doing SDL_FillRect() and SDL_BlitSurface() and the hardware supports 
it,
 >> but if you have to access the framebuffer directly (like SDL_gfx
 >> probably does), you're probably taking a speed hit here as it has to
 >> keep locking and unlocking the surface.

Yup, I'm aware of those. I only tried SDL_HWSURFACE to see if the 
flickering would go away.

Thanks for the tips, though. Could you just elaborate on "...you're 
drawing to one buffer and SDL_gfx is drawing to the other"? Maybe I have 
missed something while setting up the video mode...

Thanks again ryan,

André