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List:       kwin
Subject:    Re: Compositing manager
From:       Fredrik =?iso-8859-1?q?H=F6glund?= <fredrik () kde ! org>
Date:       2006-07-17 22:11:56
Message-ID: 200607180011.57036.fredrik () kde ! org
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On Monday 17 July 2006 23:29, Rivo Laks wrote:
> Ühel kenal päeval (esmaspäev 17 juuli 2006 9:37 pm) kirjutas Fredrik Höglund:
> > I don't think it's a good idea to borrow the code for this from compiz,
> > because the way compiz is currently written it only works with Xgl,
> > and KWin needs to work with AIGLX.
> 
> According to it's wikipedia page, Xgl works with AIGLX, though with some 
> modifications.

I assume you mean compiz here, not Xgl, but the key lies in those
modifications. Compiz renders its output to the root window, and
relies on a hack in Xgl that prevents the GL output from being
clipped to child windows.

This won't work in Xorg with AIGLX, because Xorg doesn't have
that hack (it's not part of the OpenGL or GLX standard), and also
because the root window may not be using a double buffered
visual (depending on the driver).

Composite overlay windows were added to the composite extension
to provide a rendering target for GL composite managers, so they
won't have to render to the root window, and to give the CM the
option of choosing the visual for the output window. But compiz
doesn't use an overlay window yet.

> > Metacity would be a better choice to borrow code from, but the
> > procedure for initializing GLX and creating a GLXWindow should be
> > well documented. I'm not sure if we can use QGLWidget in KWin.
> 
> I downloaded Metacity source code (2.15.8), but I didn't find any OpenGL code 
> in it, besides a repaint() function in c-screen.c . Maybe it's using 
> something else to initialize OpenGL?

I'm not familiar with the Metacity source code, so I can't comment
on that, but I do know that the Metacity compositor is designed
to work with AIGLX.

Fredrik

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