clearShape method
Every placed point is dropped, and with them the preview, the placed points' rings and the notice: after the commit, on Esc and on deactivation.
Implementation
@override
void clearShape() {
super.clearShape();
_hasPreview = false;
_keyed = false;
_ring0 = _ring1 = false;
if (!_disposed) _notice.value = null;
}