The selected shapes' outlines split the canvas into regions, computed as the faces of their
arrangement with linesweeper (curves kept, per-shape fill rules, holes and islands handled) and
cached per document version and selection.
- Engine: shapeBuilder.regions / merge / remove / mode commands, ToolId::ShapeBuilder and
tool.shapeBuilder (catalog: Tools > Shape builder, Shift+M). Merge makes one vector from the
picked regions styled like the top-most shape over the first; every shape covering a picked
region loses that area (becomes a vector, or is deleted when nothing is left). One gesture or
command is one undo step. Session::tool_key routes Enter (finish) and vector edit keys.
- Pathops: faces() (arrangement faces with their covering inputs) and union_faces().
- UI: region edges on the canvas, hovered/collected regions hatched (danger colour to remove),
no transform box while building, a toolbar pill with Merge/Remove modes, a hint and Done; shared
pill/tool-cell/divider/Done helpers; original merge/remove icons drawn in code.
- Tests: pathops faces; engine regions, merge, remove, curves, groups, rotation, pointer
click/drag/Alt, modes, Escape/Enter, cache, junk parameters and degenerate geometry.
- Docs: ROADMAP, README, docs/mcp.md, docs/control-protocol.md, docs/parity.md.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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