Default Layout (#15)

* Default Layout

Set and use a default layout if one or more of the nodes does not have a position.

* Update from notes in PR

lib/NodeGraphEditor.tsx

@@ -7,6 +7,7 @@ import {
   ReactFlowProps,
   ReactFlowProvider,
   useEdgesState,
+  useNodesInitialized,
   useNodesState,
   useReactFlow,
   useStoreApi,
@@ -23,6 +24,7 @@ import {
   useMemo,
   JSX,
   CSSProperties,
+  useEffect,
 } from 'react'
 import { defaultEdgeTypes } from './edge-types'
 import { IGraphConfig } from './config'
@@ -32,15 +34,15 @@ import { ClipboardItem } from './clipboard'
 import { LayoutEngine, useLayoutEngine } from './layout/layout'
 
 type NodeGraphEditorProps = Omit<FlowProps, 'edges' | 'nodes'> & {
-  onSave?: (data: any) => void
+  onSave?: (data: any) => void,
 }
 
 export const NodeGraphEditor = forwardRef<
   NodeGraphHandle,
   NodeGraphEditorProps
 >(
   (
-    { defaultNodes, defaultEdges, ...props }: NodeGraphEditorProps,
+    { defaultNodes, defaultEdges, layoutEngine, ...props }: NodeGraphEditorProps,
     ref,
   ): JSX.Element => {
     const [nodes, , onNodesChange] = useNodesState(defaultNodes ?? [])
@@ -81,15 +83,19 @@ export const ExampleNodeGraphEditor = forwardRef<
 })
 
 type FlowProps = ReactFlowProps & {
-  backgroundStyles?: CSSProperties
+  backgroundStyles?: CSSProperties,
+  /**
+   * The default layout engine to use when nodes are provided without positions.
+   */
+  layoutEngine?: LayoutEngine
 }
 export type NodeGraphHandle = {
   layout: () => void
 }
 
 const Flow = forwardRef<NodeGraphHandle, FlowProps>(
   (
-    { defaultNodes, defaultEdges, backgroundStyles, ...props }: FlowProps,
+    { backgroundStyles, layoutEngine, ...props }: FlowProps,
     ref,
   ) => {
     const nodeTypes = useNodeTypes()
@@ -98,6 +104,7 @@ const Flow = forwardRef<NodeGraphHandle, FlowProps>(
     const [config] = useGraphConfig()
     const { getState } = useStoreApi()
     const { setNodes, setEdges } = useReactFlow()
+
 
     // Handle clipboard events
     useHotkeys(
@@ -110,7 +117,7 @@ const Flow = forwardRef<NodeGraphHandle, FlowProps>(
     )
 
     // Provide methods to parent components
-    const layout = useLayoutEngine(LayoutEngine.Dagre)
+    const layout = useLayoutEngine(layoutEngine ?? LayoutEngine.Dagre)
     useImperativeHandle(
       ref,
       () => ({
@@ -119,6 +126,16 @@ const Flow = forwardRef<NodeGraphHandle, FlowProps>(
       [],
     )
 
+    const initialized = useNodesInitialized()
+    useEffect(() => {
+      const shouldLayout = !!getState().nodes.find(
+        (node) => node.position == undefined,
+      )
+      if (initialized && shouldLayout) {
+        layout()
+      }
+    }, [initialized])
+
     return (
       <div
         style={{

lib/NodeGraphEditorInputGroups.stories.tsx

@@ -228,7 +228,7 @@ export const InputGroups: Story = {
       {
         id: '1',
         type: 'bsdf',
-        position: { x: 350, y: 100 },
+        // position: { x: 350, y: 100 },
         data: {
           __inputGroupsExpanded: ['Specular'],
         },
@@ -251,7 +251,7 @@ export const InputGroups: Story = {
         position: { x: 100, y: 300 },
         data: {},
       },
-    ],
+    ] as Node[],
     edges: [
       {
         id: 'e1',

lib/layout/layout.ts

@@ -1,6 +1,6 @@
 import { useCallback } from 'react'
 import { computeDagreLayout } from './dagre'
-import { Instance, Node, useReactFlow } from '@xyflow/react'
+import { Edge, Instance, Node, useReactFlow } from '@xyflow/react'
 
 export enum LayoutEngine {
   Dagre,
@@ -20,10 +20,16 @@ function computeLayout(
   getNodes: Instance.GetNodes<any>,
   getEdges: Instance.GetEdges<any>,
 ): Node[] {
+  const layoutFn = getLayoutFunction(engine)
+  if (!layoutFn) throw new Error(`Unknown layout engine ${engine}`)
+  return layoutFn(getNodes(), getEdges())
+}
+
+export function getLayoutFunction(
+  engine: LayoutEngine | undefined,
+): ((nodes: Node[], edges: Edge[]) => Node[]) | undefined {
   switch (engine) {
     case LayoutEngine.Dagre:
-      return computeDagreLayout(getNodes(), getEdges())
-    default:
-      throw new Error(`Unknown layout engine ${engine}`)
+      return computeDagreLayout
   }
 }