[cairo] Image scaling performance on X

[Boris Zbarsky]

Eric Anholt wrote:
> Much of Render can't be accelerated with XAA, which is what most 2d
> drivers use, resulting in awful performance.  We've been working on EXA
> to replace XAA, and I'm using it daily now, but most drivers still need
> some more love before EXA can be flipped to be the default on them.

Eric, that sounds wonderful, but if I understand correctly that's the plan going 
forward, right?  It won't apply to the existing install base?

The problem is that shipping a Cairo-based Gecko sometime in 2007 requires a 
solution that works with existing X installs....

If I'm misunderstanding and there are plans to backport EXA to what are 
currently stable releases of distros, that's great!

Is there any way to detect from inside Cairo whether EXA or XAA is used and fall 
back on something other than Render as needed?

-Boris