Re: [AD] Fw: Acquire/Release speed issue

[Eric Botcazou <ebotcazou@xxxxxxxxxx>]

> I investigated in the issue and found why I didn't reuse the screen on
> first create_video_bitmap() call. Since we're emulating page flipping,
> there is no real page flip at all, as the video bitmaps are copied onto
> the real screen.

The Windows windowed driver also emulates page flipping, and it does reuse 
the screen like the fullscreen one.

> With emulation how I did it, you have the real "screen" BITMAP, and each
> time you call create_video_bitmap(), it returns a new BITMAP. You draw into 
> one of these, then show_video_bitmap() copies onto "screen". If I reuse
> the screen, this doesn't work, as with emulation "screen" is always
> displayed, no matter if you call show_video_bitmap() to flip pages...

The technique is to swap the underlying surfaces on each call to 
show_video_bitmap():

Before:   BITMAPs   page1 == screen        page2
                        |                   |
          Surfaces    surface1           surface2

Flip:  the contents of surface2 are copied onto surface1, then surface1 is 
attached to page2 and surface2 to page1

After:   BITMAPs   page2 == screen        page1
                        |                   |
          Surfaces    surface1           surface2

-- 
Eric Botcazou