Does anyone know OTT how filling is performed?
Is it just the standard, sort the vertices and walk the inside edges down either side of the vertex a line at a time?
I can probably tell by making some shapes that don't fill in a uniform manner when you do that and see who inkscape fills them.
I've got a good collection of path segment functions together now for prototyping, and found the first SVG feature implemented on the GPU, or at least in OpenCL, filters. So, that's a positive.
I'll think I'll keep on working on the extension before doing any experimentation but I think I've to go a good outline of things to test to see how they fair in terms of rendering performance and enough SVG features down that I should be able to do a bit more than just a point line test.
I looked up Bézier length calculations again, and they are basically an approximation using lookup tables. Wikipedia said you could calculate them definitely using a partial integral when I looked a while back but it seems it was incorrect and I'm back where I started in high school calculating the sum of the magnitude of the segments.