fuseDragEffect function
Calls fn when a drag start event occurs.
The fn may optionally return a cleanup function that is called when the drag ends.
Implementation
void fuseDragEffect(FuseDragEffectFn fn) {
Function(DragEndEvent)? cleanup;
fuseDragStart((event) {
cleanup = fn(event);
});
fuseDragEnd((event) {
cleanup?.call(event);
cleanup = null;
});
}