Dragging a direction handle with Direct Selection or the Anchor Point tool
sent the pointer position straight to path.setHandle: Shift did nothing and
the handle never snapped, while the Pen already constrains the handles it
pulls out.
guides::snap_handle places a dragged handle: with Shift at a multiple of
45° from its anchor (the Pen's constraint, keeping the dragged length),
otherwise snapped as a drawn point is (smart guides, the grid, pixels).
Both tools use it and show the smart guides while the handle moves.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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