* M12: stamps stick to the objects they land on
A stamp sticks to the topmost object under its centre (BoardItem::Stamp gains an optional on, left out when empty so older files open with stamps on nothing) and the board's normalize pass carries it when that object moves or turns, once when both move together. A stamp dragged onto another object sticks to that one, off everything to nothing; one whose object is deleted stays where it is. Gap 24.
* M12: the object a stamp will stick to is highlighted
While the stamp tool is over an object, or a stamp is dragged over one, the object it will stick to is outlined with the canvas's hover outline (Overlay::stamp_target, found by the same stamp_target as board.stamp and settle_stamps). A drag no longer drops what it moves into the auto layout of a sticky, shape with text or table: board objects take no drops; a stamp already inside its sticky moves with it once. Builds on #1671. Gap 24.
Every pointer move draws about three frames, and the canvas hit-tested the hover on each: a hover where nothing changed since the last (place, modifiers, zoom, file, page, revision, selection, tool and modes) is no longer sent to the tools again. Dragging an auto layout frame laid its contents out again on every move: a frame whose only change is its transform now keeps its own layout (its parent's still runs). ui.inspect reports frameTimes. Measured on a synthetic 1,900-layer file: hover UI pass 0.91 to 0.49 ms a frame and CPU 33% to 22% of a core; normalise while dragging 648 layers 3.8 to 2.1 ms a move.
Session::execute ran a command under guard::run but normalised what it
changed afterwards, outside it: a panic in normalisation escaped execute
instead of becoming EngineError::Internal with the edit rolled back. Inside
a batch it unwound through Session::grouped, which then never restored the
undo limit it had lifted or ended the group. Normalising is now the last
step of the guarded result chain, so a panic there fails the command like
one in the command itself (and a batch step fails like any other failed
step); live text previews normalise under the guard too.
The other half of #1085, restoring grouped()'s state when its closure
panics, is left alone: #1419 rewrites that function.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LvG6E2qDnjtMzfPVuEP7iH
BFlat