The Live Paint faces were right; the Pathfinder regions over-counted.
Two small circles inside a big one, touching each other at one point,
gave the big circle's region only one of its two holes, and the other
hole came out as a region of its own.
linesweeper walks the boundary of the two touching holes as one loop
and, when the walk comes back to the shared point, cuts the second
hole off as a child of the first and flags it outer, as if it were an
island inside it. face_groups trusted that flag, so the hole started a
face. The same cut goes wrong the other way when an outer contour
touches its own hole: the outer contour comes out as an island inside
the hole.
Such a loop winds the same way as the contour it was cut from, against
its flag. face_groups now checks every contour's flag against its
winding; a pass where any disagrees is grouped by geometry instead
(each hole goes with the smallest outer contour of its mask around it).
Passes where they all agree keep the sweep's tree as before, at the
cost of one area per contour.
Adds deterministic tests for both shapes of the bug and checks in the
proptest regression seed.
Capture sweep-piece source attribution before endpoint pinning can move its
midpoint off the original outlines. Keep the existing lookup after pinning
when the original piece has no source.
Add planar coverage and native compound Make/Expand/undo regressions, and
document the existing front-most source-fill rule.
Where a line lies under the outline of a closed path in front of it (such as
a shape an earlier merge made, which takes the place of the art in front of
the lines), the planar map gave that stretch only to the closed path, so the
line had no piece there. A merge or an erase across it left the line whole,
and the next map split the new shape along it into two regions.
- pathops: each planar edge records every input it lies on, and
BuilderArrangement::lines_under holds the lines' pieces under a closed
outline in front of them. lines, edges and Live Paint are unchanged.
- tools: BuilderMap adds those pieces to its lines, so a merge or an erase
removes the stretch between the regions it takes, as it does elsewhere.
An Alt-click where a line lies under an edge hits the one in front.
bflatastic