[Xr] XrMatrixGetAffine() function

[Keith Packard]

Around 12 o'clock on Jul 3, Soorya Kuloor wrote:

Thanks very much for your comments:

> * Text handling does not seem to be as good as the rest of the drawing,
> both API and speed-wise.

This is well known -- Xr is attempting to use Xft for text rendering and 
the result is quite horrible.  I'm hoping to get a chance to write down 
some ideas I've been mulling over to see if we can't start afresh and 
build something that better matches the Xr style and can be implemented 
efficiently.

> Especially, the initial query for a given font-transform combination
> seems to take long time too (the call into fontconfig).

Pango caches the results to make future queries faster, but fontconfig 
itself is not likely to improve dramatically in the near future.

Drawing the text will get a lot faster as we get a chance to optimize the 
underlying compositing routines.

> * We did a speed comparison of Xr against GDI+. For the ellipse drawing
> test (posted by Owen) with anti-aliasing GDI+ is approx 2-2.5 times
> faster than Xr.

That's actually very encouraging -- none of the Xr rendering codepaths 
have seen any optimization at all, and the trapezoid filling code is 
already scheduled for a complete rewrite which should make it a lot 
faster.  Combine that with optimizations in the compositng code and the 
tesselation code and getting a factor of 2 in performance should be very 
easy.

-keith