Add 'canMoveNode(INode)'.

README.md

@@ -245,6 +245,7 @@ All props are detailed below.
 | `canDeleteSelected` | `func` | `false` | takes the place of `canDeleteNode` and `canDeleteEdge`. It accepts a `SelectionT` type as a parameter. It is called before a node or edge is deleted. The function should return a boolean.
 | `canCreateEdge`            | `func`                     | `false`      | Called before an edge is created.|
 | `canSwapEdge`              | `func`                     | `false`      | Called before an edge 'target' is swapped.
+| `canMoveNode`              | `func`                     | `false`      | Called before a node is moved (e.g. by being dragged). |
 | `afterRenderEdge`          | `func`                     | `false`      | Called after an edge is rendered.                                                                                                                                                           |
 | `renderNode`               | `func`                     | `false`      | Called to render node geometry.                                                                                                                                                             |
 | `renderNodeText`           | `func`                     | `false`      | Called to render the node text                                                                                                                                                              |

src/components/graph-view-props.js

@@ -71,6 +71,7 @@ export type IGraphViewProps = {
     hoveredNode: INode | null,
     swapEdge: IEdge
   ) => boolean,
+  canMoveNode?: (node: INode) => boolean,
   onBackgroundClick?: (x: number, y: number, event: any) => void,
   onCopySelected?: () => void,
   onCreateEdge?: (sourceNode: INode, targetNode: INode) => void,

src/components/graph-view.js

@@ -79,6 +79,7 @@ class GraphView extends React.Component<IGraphViewProps, IGraphViewState> {
     canCreateEdge: (startNode?: INode, endNode?: INode) => true,
     canSwapEdge: () => true,
     canDeleteSelected: () => true,
+    canMoveNode: () => true,
     allowMultiselect: true,
     edgeArrowSize: 8,
     gridSpacing: 36,
@@ -862,7 +863,14 @@ class GraphView extends React.Component<IGraphViewProps, IGraphViewState> {
   }
 
   handleNodeMove = (position: IPoint, nodeId: string, shiftKey: boolean) => {
-    const { canCreateEdge, readOnly, selected, nodeKey, onSelect } = this.props;
+    const {
+      canCreateEdge,
+      canMoveNode,
+      readOnly,
+      selected,
+      nodeKey,
+      onSelect,
+    } = this.props;
     const { draggingEdge, nodesMap } = this.state;
     const nodeMapNode: INodeMapNode | null = this.getNodeById(nodeId);
 
@@ -872,6 +880,10 @@ class GraphView extends React.Component<IGraphViewProps, IGraphViewState> {
 
     const node = nodeMapNode.node;
 
+    if (canMoveNode && !canMoveNode(node)) {
+      return;
+    }
+
     if (!shiftKey && !draggingEdge) {
       const originalX = node.x || 0;
       const originalY = node.y || 0;