placedIn method
The live walls and separators, ascending, whose place box touches
box (closed: touching counts), as ParametricView.placedIn answers.
Implementation
@override
List<Handle> placedIn(Aabb2 box) {
_refresh();
return List.unmodifiable([
for (final (h, b) in _placed)
if (b.intersects(box)) h,
]);
}