With several layers selected, After Effects applies a property edit to the same property of
every selected layer; we changed only the layer whose row was edited (the Properties panel
showed only the first selected layer), so a stopwatch switched on one layer and later moves
of the others had nothing to keyframe (#355), and scaling or rotating a selection changed
one layer (#491).
- Engine: `prop.set`, `prop.toggleAnimation` and `prop.toggleKey` take `selected: true`:
the change also goes to the same property (by match path, `transform/scale`,
`effects/<effect>#n/<param>`) of every other selected, unlocked layer whose value has the
same kind, in one undo step (a scrub keeps folding into it through its `merge` key). With
`offset: true` (a scrub) each layer changes by the same amount from its own value; a typed
value sets them all. Position with Separate Dimensions is handled per layer.
- The Timeline, Properties and Effect Controls panels pass `selected` (and `offset` while a
value is dragged). The Properties panel heads "(N) Selected Objects" (zh-CN / zh-TW / ja /
uk rows).
- Viewer: a bounding-box handle drag scales every selected layer by the same ratio about its
own anchor point; the Rotation tool turns them all by the same angle (one undo step).
Tests: engine test (stopwatch, scrub offset, typed value, keyframe button, one undo step,
unselected layers untouched); kittests: the Properties panel with three layers selected
(header, stopwatch on all three undone in one step, a scrub moving all three by the same
amount) and a handle drag scaling two selected layers.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QiAJeFttZp83Fh7YuzAR5f
657f34d40b