Cairo with glitz backend

[Paolo Bonzini]

What I actually like about Glitz is the abstraction of FBOs to surfaces
and drawables.  While there is basically no documentation about it, I
placed some examples in my glitz repository---both using OpenGL
rendering as a source for Cairo operations, and using the result of
cairo compositing as an OpenGL texture.  That is something that I would
expect from a cairo OpenGL surface.  Ideally, if I use some external
library (e.g. SDL) to set up my OpenGL context, I should be able to do
this in a completely portable way.

Its abstraction of the pixel format queries from all the OS bindings is
also relatively easy to use.  Probably, extracting the
platform-agnosticness support out of Glitz would also benefit other
implementations including Eric Anholt's.

If Cairo grows a native OpenGL surface that would be great.  However,
with all its shortcomings, I don't think Glitz should be dismissed
totally.  What it, unfortunately, is that there is a lot of stuff to
supported (Eric's backend still lacks clipping regions, for example) and
there is quite some code in Glitz, ready to be leveraged and under a
nice license.

> 2. A responsive and long-term maintainer (for both the cairo backend the
> glitz library).

I'm not sure there is that much need, since there is not much churn
going on there and I do expect it to die slowly.  It would be nice
however to have patches reviewed and applied from the people on the
cairo or xorg mailing lists.

Paolo