NodeDragContext<T> class

Context provided to nodes during drag and lifecycle operations.

This context allows nodes (including annotations that extend Node) to interact with other nodes during drag, enabling behaviors like moving contained nodes when a group is dragged, or refitting bounds when member nodes are deleted.

Example Usage

class MyGroupNode extends Node<GroupData> {
  Set<String>? _containedNodeIds;

  @override
  void onDragStart(NodeDragContext context) {
    // Capture nodes inside this group at drag start
    _containedNodeIds = context.findNodesInBounds(getBounds());
  }

  @override
  void onDragMove(Offset delta, NodeDragContext context) {
    // Move the contained nodes along with this group
    if (_containedNodeIds != null && _containedNodeIds!.isNotEmpty) {
      context.moveNodes(_containedNodeIds!, delta);
    }
  }

  @override
  void onDragEnd() {
    _containedNodeIds = null;
  }
}