onDragMove method
Called during a drag operation as the node moves.
Implementation
@override
void onDragMove(Offset delta, NodeDragContext context) {
// Move all contained nodes along with this group,
// excluding nodes that are already selected (they're being moved by selection drag)
if (_containedNodeIds != null && _containedNodeIds!.isNotEmpty) {
final nodesToMove = _containedNodeIds!.difference(
context.selectedNodeIds,
);
if (nodesToMove.isNotEmpty) {
context.moveNodes(nodesToMove, delta);
}
}
}