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;
_pointerPosition.value = pointerGlobal;
_resolveAndNotify(session);
}