[cairo] GSoC/scan converting rasteriser update

[M Joonas Pihlaja]

Hey cairo-l,

I got friendly reminder from my mentor to keep you guys updated
on the status of my GSoC project.  I guess he really meant "yo
dude, you haven't made a peep even on the mailing list yet!", so
to make up for lost time, I've bootstrapped a blog about it on
http://people.freedesktop.org/~joonas/status-blog/.

The work so far is available at
git://people.freedesktop.org/~joonas/spans, and consists of a
horizontal span container, and mono/analytic span generators.
That's an independent code base that has nothing to do with cairo
yet, so my plan for this week is to cairoise it and clean it up a
little to get a slow and correct polygon rasteriser.

In the slow and correct version I plan to punt on both span
generation and compositing.  For span generation, I'm going to go
via the tessellator, because the analytic rasteriser gets pixels
with intersections slightly wrong.  I'll also punt on compositing
spans and instead first rasterise an alpha mask of the polygon
and then call pixman to do the actual tricky bits.  So yes, very
slow, but hopefully "obviously" correct once done, at least in
principle, yes?

Cheers,

Joonas