[cairo] Mozilla on Cairo

[mental at rydia.net]

Quoting Robert O'Callahan <rocallahan at novell.com>:

> But FSAA is a combination of "turn off pixel-coverage
> antialiasing" and "render to a larger buffer and scale down with
> pixel averaging".  So the first step to supporting FSAA is to be
> able to turn off the coverage antialiasing. Then, when resources
> permit, we can add supersampling.

Well, that's only one of many approaches to doing FSAA.

One alternative would be storing all the trapezoids to be rendered
in a BSP tree and then rendering them in a single pass at the end. 
That would permit you to do the partial coverage calculations "for
real", rather than faking it through accumulating alpha
compositing.

Depending on the complexity of the scene, it may be more or less
efficient than FSAA via supersampling.

-mental