GLX redirection extension

Kristian Høgsberg krh at
Thu Jul 20 10:57:43 PDT 2006

On 7/20/06, Felix Bellaby <felix at> wrote:
> I think that I may have found a potentially useful way out of some
> problems within the current compositing framework. Basically, the server
> has information that the compositor would find useful.

I'm not sure what problems you're trying to solve here, but we don't
need extra protocol for redirecting GLX.  When a window is redirected
with COMPOSITE, all rendering to that window is supposed to go to an
offscreen pixmap.  The two big issues with COMPOSITE today is that
accelerated OpenGL (direct or indirect) and Xv doesn't respect this
and render directly to the front buffer.  Extra protocol or API won't
solve this, we "just" need to fix the implementation to consistently
redirect all kinds of rendering for a redirected window.

There is one case where we will need extra protocol (this will be an
extension to the XF86DRI protocol): when doing direct OpenGL rendering
to a redirected window.  In this case all the rendering happens in the
client without the X server knowing, but the compositing manager will
need damage events for the pixmap in order to be able to recomposite
it as changes happen.  For this, we need an XF86DRI request that
allows libGL (the direct rendering client) to post damage on a window.
 But note, none of this will be visible in the API.


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