Fixes #602. Collinear-edge merging, piece naming and the dialog preview each work in one pass instead of quadratic loops; the issue's example goes from 86 s to 5.1 s.
Fixes #602. Collinear-edge merging, piece naming and the dialog preview each work in one pass instead of quadratic loops; the issue's example goes from 86 s to 5.1 s.