chore(examples): add layouting

example/src/Layouting/index.js

@@ -0,0 +1,68 @@
+import React, { useEffect, useState } from 'react';
+import ReactFlow, { ReactFlowProvider, addEdge, removeElements, Controls, isNode } from 'react-flow-renderer';
+import dagre from 'dagre';
+
+import initialElements from './initial-elements';
+
+import './layouting.css';
+
+const dagreGraph = new dagre.graphlib.Graph();
+dagreGraph.setDefaultEdgeLabel(() => ({}));
+
+const LayoutFlow = () => {
+  const [elements, setElements] = useState(initialElements);
+  const onConnect = (params) => setElements((els) => addEdge(params, els));
+  const onElementsRemove = (elementsToRemove) => setElements((els) => removeElements(elementsToRemove, els));
+
+  const onLayout = (direction) => {
+    const isHorizontal = direction === 'LR';
+    dagreGraph.setGraph({ rankdir: direction });
+
+    elements.forEach((el) => {
+      if (isNode(el)) {
+        dagreGraph.setNode(el.id, { width: 150, height: 50 });
+      } else {
+        dagreGraph.setEdge(el.source, el.target);
+      }
+    });
+
+    dagre.layout(dagreGraph);
+
+    const layoutedElements = elements.map((el) => {
+      if (isNode(el)) {
+        const nodeWithPosition = dagreGraph.node(el.id);
+        el.targetPosition = isHorizontal ? 'left' : 'top';
+        el.sourcePosition = isHorizontal ? 'right' : 'bottom';
+        // we need to pass a slighltiy different position in order to notify react flow about the change
+        // @TODO how can we change the position handling so that we dont need this hack?
+        el.position = { x: nodeWithPosition.x + Math.random() / 1000, y: nodeWithPosition.y };
+      }
+
+      return el;
+    });
+
+    setElements(layoutedElements);
+  };
+
+  useEffect(() => {
+    onLayout('TB');
+  }, []);
+
+  return (
+    <div className="layoutflow">
+      <ReactFlowProvider>
+        <ReactFlow elements={elements} onConnect={onConnect} onElementsRemove={onElementsRemove}>
+          <Controls />
+        </ReactFlow>
+        <div className="controls">
+          <button onClick={() => onLayout('TB')} style={{ marginRight: 10 }}>
+            vertical layout
+          </button>
+          <button onClick={() => onLayout('LR')}>horizontal layout</button>
+        </div>
+      </ReactFlowProvider>
+    </div>
+  );
+};
+
+export default LayoutFlow;