updateDrag method
Updates the pointer position. Re-resolves the drop target and starts / stops the autoscroll ticker as needed.
Implementation
void updateDrag(Offset pointerGlobal) {
final session = _session;
if (session == null) return;
session.pointerGlobal = pointerGlobal;
final previous = session.currentTarget;
_recomputeDropTarget();
_updateAutoScroll();
if (!_targetsEqual(previous, session.currentTarget)) {
notifyListeners();
}
}