Blender Git Loki

Cleanup 'make vertex parent' operator code.

More localized variables, avoid ugly 'offset by one' index usage in
favor of explicit `INDEX_UNSET` define, etc.

No behavior change expected from this commit.

Fix T80135: Duplicate doesn't preserve active spline

Checks to preserve the active spline on duplication
required an active vertex too.

Now having no active vertex doesn't prevent duplicate
from keeping the spline active.

Reviewed by: @mano-wii

Ref D8729

Cleanup: use doxy sections in interface_panels.c

Cleanup: spelling

LineArt: Slope throw away threshold in lineart_LineIntersectTest2d()

LineArt: More fluent viewport manipulation (canceling sequence optimization)

LineArt: Better manuverability with quick cancel.

LineArt: Feature line compatible clipping.

Merge remote-tracking branch 'origin/master' into lanpr-under-gp

Merge remote-tracking branch 'origin/master' into lanpr-under-gp

LineArt: Splitting limit for dense triangle situations.

LineArt: Prompt on baking finish.

Merge remote-tracking branch 'origin/master' into lanpr-under-gp

LineArt: Basic background task canceling.

LineArt: Back-transform strokes to allow gp to sit at other positions.

LineArt: Disable line art object viewport selection by default.

LineArt: Prevent crash when using any sort of moving operators.

Merge remote-tracking branch 'origin/master' into lanpr-under-gp

Merge branch 'master' into lanpr-under-gp

Merge branch 'master' into lanpr-under-gp