[maemo-developers] [maemo-developers] SDL vertical blank (vbl) sync.

[From: Frantisek Dufka]

Tapani Pälli wrote:

> 
> I think there's no guarantee that you will get "HW surface" from SDL, it
> will silently fallback to SW surface if it cannot have HW one.
> 
> SDL draws to X, X draws to the framebuffer mapped by kernel which then
> updates that data to the lcd controller where screen gets finally
> updated. I would recommend to blit things in memory, then push only
> needed parts with SDL_UpdateRects trying to avoid fullscreen updates.

Yes. So to draw without tearing effect either X of framebuffer driver 
should report when to draw (vblank period or which line is currently 
drawn by hardware) or the controller has to have two buffers so single 
or multiple SDL_UpdateRects could be pushed to visible screen in one 
operation (SDL_Flip) in appropriate moment.

Frantisek