Many high-level functions with unrelated code were templated based on
the color attribute domain and type. In the end, those were just a few
branches though, similar to other branches. So to reduce binary bloat
and clarify code, move tempates to the point where separate types are
actually needed. Also move constant code out of loops, and use generic
arrays and spans to store some caches. The binary ended up 53 KB
smaller for me, which isn't much but it's in the right direction.
Performance wise nothing really changes. The vast majority of time in
vertex paint is spent on unrelated things like calculating normals or
uploading GPU buffers anyway.
The one ugly part I didn't account for when I started is the casting
between the "ColorGeometry" and "ColorPaint" types. I'm not sure that
this is correct, but it's just a more explicit version of what was
there already.
Pull Request: https://projects.blender.org/blender/blender/pulls/109941
Hans Goudey
087612c042