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Date: Fri, 20 Feb 2009 17:01:49 +0000
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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Subject: Re: [Qemu-devel] Re: Qemu 2D performance plunges below acceptable
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To: Paul Brook <paul@codesourcery.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

Paul Brook wrote:

>>      SDL_BlitSurface(guest_screen, &rec, real_screen, &rec);
>> -    SDL_UpdateRect(real_screen, x, y, w, h);
>> +    SDL_UpdateRects(real_screen, 1, &rec);
> 
> Have you actually tried this? I'd be amazed and dismayed if it made any 
> difference. I can believe that SDL_UpdateRects is better that *multiple* 
> calls to SDL_UpdateRect. However I see absolutely no justification for this 
> change.
> 

Of course I didn't: I don't have any MacOSX available and this is the
main reason I am asking other people to test this patch and doing it myself.

>>From the documentation I thought they were implemented differently
somehow but now that you make me think about it I went through the
actual code and SDL_UpdateRect is implemented using SDL_UpdateRects :(

Also I don't how to explain the fact that SDL_Flip is faster than
SDL_UpdateRect on MacOSX according to malc: the same libsdl macosx faq I
 linked before claims that SDL_DOUBLEBUF is not even supported on MacOsX.