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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: Qemu 2D performance plunges below acceptable
	levels
Date: Fri, 20 Feb 2009 17:16:01 +0000
References: <7fac565a0902150510y1fb01c6awd1dcc3b6e7b8232d@mail.gmail.com>
	<200902201652.55386.paul@codesourcery.com>
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

> 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.

I guess it's possible that under a sufficiently lame implementation a partial 
update could be slower than an update of the whole screen. e.g. if your 
accelerated blit routines isn't capable of copying rectangular regions you 
have to do the partial update a line at a time, whereas a full update is a 
single blit operation. Seems a fairly unlikely corner case though, especially 
as we tend to update a whole number of lines.

Paul