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List:       freedesktop-xorg
Subject:    Re: What is ShadowFB?
From:       "Alex Deucher" <alexdeucher () gmail ! com>
Date:       2007-06-01 12:50:44
Message-ID: a728f9f90706010550m3563748x4651979ea9ad5cb8 () mail ! gmail ! com
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On 6/1/07, Rob Kramer <robk@starhub.net.sg> wrote:
> Hi,
>
> I've been googling and source-browsing around, trying to find out what
> exactly the purpose of shadowfb is (with respect to rotation), without much
> success. Can someone tell me if it is documented somewhere?
>

A shadow framebuffer is a copy of the framebuffer that exists in
system ram or elsewhere in video ram.  It's useful for rotation
because the shadowed copy can be rotated when it's copied to the front
buffer for scan out.  The rotation can be handled by hardware if the
drawing engine supports rotated blits or using the 3D engine for
transforms.

Alex
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