* M4: arc handles on the canvas
A selected ellipse shows its arc handles with the Move tool, as public
documentation of Figma-class tools describes them:
- Sweep, inside the right edge on the centre line: dragged round the ellipse
it opens an arc (positive up, negative down, continuous through a full
turn) and closes again back at the start.
- Start (a dot inside), once there is an arc: turns the arc, keeping its sweep.
- Ratio, at the centre or the inner edge halfway round a ring: drags out to a
ring, and into the gap to show the other part.
- Shift snaps angles to 15 degree steps and the ratio to 5% steps; a live
readout (Sweep 75%, Start 90 degrees, Ratio 40%) shows beside the handle.
- Rotated and flipped ellipses, any zoom; hidden under 40 px on screen.
One undo step per drag through node.set's arcStart/arcSweep/arcInner;
Escape cancels.
The geometry lives in crates/engine/src/arc_handles.rs (tests in
arc_handles_tests.rs); the gesture in tools.rs; ui.inspect / inspect_ui list
tool.arcHandles and the overlay's arc readout. Docs, README and ROADMAP
updated.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* Merge origin/main into feat/arc-handles; weighted depth 78%
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
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