react-flow-architecture
# React Flow Architecture
## When to Use React Flow
### Good Fit
- Visual programming interfaces
- Workflow builders and automation tools
- Diagram editors (flowcharts, org charts)
- Data pipeline visualization
- Mind mapping tools
- Node-based audio/video editors
- Decision tree builders
- State machine designers
### Consider Alternatives
- Simple static diagrams (use SVG or canvas directly)
- Heavy real-time collaboration (may need custom sync layer)
- 3D visualizations (use Three.js, react-three-fiber)
- Graph analysis with 10k+ nodes (use WebGL-based solutions like Sigma.js)
## Architecture Patterns
### Package Structure (xyflow)
```
@xyflow/system (vanilla TypeScript)
├── Core algorithms (edge paths, bounds, viewport)
├── xypanzoom (d3-based pan/zoom)
├── xydrag, xyhandle, xyminimap, xyresizer
└── Shared types
@xyflow/react (depends on @xyflow/system)
├── React components and hooks
├── Zustand store for state management
└── Framework-specific integrations
@xyflow/svelte (depends on @xyflow/system)
└── Svelte components and stores
```
**Implication**: Core logic is framework-agnostic. When contributing or debugging, check if issue is in @xyflow/system or framework-specific package.
### State Management Approaches
#### 1. Local State (Simple Apps)
```tsx
// useNodesState/useEdgesState for prototyping
const [nodes, setNodes, onNodesChange] = useNodesState(initialNodes);
const [edges, setEdges, onEdgesChange] = useEdgesState(initialEdges);
```
**Pros**: Simple, minimal boilerplate
**Cons**: State isolated to component tree
#### 2. External Store (Production)
```tsx
// Zustand store example
import { create } from 'zustand';
interface FlowStore {
nodes: Node[];
edges: Edge[];
setNodes: (nodes: Node[]) => void;
onNodesChange: OnNodesChange;
}
const useFlowStore = create<FlowStore>((set, get) => ({
nodes: initialNodes,
edges: initialEdges,
setNodes: (nodes) => set({ nodes }),
onNodesChange: (changes) => {
set({ nodes: applyNodeChanges(changes, get().nodes) });
},
}));
// In component
function Flow() {
const { nodes, edges, onNodesChange } = useFlowStore();
return <ReactFlow nodes={nodes} onNodesChange={onNodesChange} />;
}
```
**Pros**: State accessible anywhere, easier persistence/sync
**Cons**: More setup, need careful selector optimization
#### 3. Redux/Other State Libraries
```tsx
// Connect via selectors
const nodes = useSelector(selectNodes);
const dispatch = useDispatch();
const onNodesChange = useCallback((changes: NodeChange[]) => {
dispatch(nodesChanged(changes));
}, [dispatch]);
```
### Data Flow Architecture
```
User Input → Change Event → Reducer/Handler → State Update → Re-render
↓
[Drag node] → onNodesChange → applyNodeChanges → setNodes → ReactFlow
↓
[Connect] → onConnect → addEdge → setEdges → ReactFlow
↓
[Delete] → onNodesDelete → deleteElements → setNodes/setEdges → ReactFlow
```
### Sub-Flow Pattern (Nested Nodes)
```tsx
// Parent node containing child nodes
const nodes = [
{
id: 'group-1',
type: 'group',
position: { x: 0, y: 0 },
style: { width: 300, height: 200 },
},
{
id: 'child-1',
parentId: 'group-1', // Key: parent reference
extent: 'parent', // Key: constrain to parent
position: { x: 10, y: 30 }, // Relative to parent
data: { label: 'Child' },
},
];
```
**Considerations**:
- Use `extent: 'parent'` to constrain dragging
- Use `expandParent: true` to auto-expand parent
- Parent z-index affects child rendering order
### Viewport Persistence
```tsx
// Save viewport state
const { toObject, setViewport } = useReactFlow();
const handleSave = () => {
const flow = toObject();
// flow.nodes, flow.edges, flow.viewport
localStorage.setItem('flow', JSON.stringify(flow));
};
const handleRestore = () => {
const flow = JSON.parse(localStorage.getItem('flow'));
setNodes(flow.nodes);
setEdges(flow.edges);
setViewport(flow.viewport);
};
```
## Integration Patterns
### With Backend/API
```tsx
// Load from API
useEffect(() => {
fetch('/api/flow')
.then(r => r.json())
.then(({ nodes, edges }) => {
setNodes(nodes);
setEdges(edges);
});
}, []);
// Debounced auto-save
const debouncedSave = useMemo(
() => debounce((nodes, edges) => {
fetch('/api/flow', {
method: 'POST',
body: JSON.stringify({ nodes, edges }),
});
}, 1000),
[]
);
useEffect(() => {
debouncedSave(nodes, edges);
}, [nodes, edges]);
```
### With Layout Algorithms
```tsx
import dagre from 'dagre';
function getLayoutedElements(nodes: Node[], edges: Edge[]) {
const g = new dagre.graphlib.Graph();
g.setGraph({ rankdir: 'TB' });
g.setDefaultEdgeLabel(() => ({}));
nodes.forEach((node) => {
g.setNode(node.id, { width: 150, height: 50 });
});
edges.forEach((edge) => {
g.setEdge(edge.source, edge.target);
});
dagre.layout(g);
return {
nodes: nodes.map((node) => {
const pos = g.node(node.id);
return { ...node, position: { x: pos.x, y: pos.y } };
}),
edges,
};
}
```
## Performance Scaling
### Node Count Guidelines
| Nodes | Strategy |
|-------|----------|
| < 100 | Default settings |
| 100-500 | Enable `onlyRenderVisibleElements` |
| 500-1000 | Simplify custom nodes, reduce DOM elements |
| > 1000 | Consider virtualization, WebGL alternatives |
### Optimization Techniques
```tsx
<ReactFlow
// Only render nodes/edges in viewport
onlyRenderVisibleElements={true}
// Reduce node border radius (improves intersect calculations)
nodeExtent={[[-1000, -1000], [1000, 1000]]}
// Disable features not needed
elementsSelectable={false}
panOnDrag={false}
zoomOnScroll={false}
/>
```
## Trade-offs
### Controlled vs Uncontrolled
| Controlled | Uncontrolled |
|------------|--------------|
| More boilerplate | Less code |
| Full state control | Internal state |
| Easy persistence | Need `toObject()` |
| Better for complex apps | Good for prototypes |
### Connection Modes
| Strict (default) | Loose |
|------------------|-------|
| Source → Target only | Any handle → any handle |
| Predictable behavior | More flexible |
| Use for data flows | Use for diagrams |
```tsx
<ReactFlow connectionMode={ConnectionMode.Loose} />
```
### Edge Rendering
| Default edges | Custom edges |
|---------------|--------------|
| Fast rendering | More control |
| Limited styling | Any SVG/HTML |
| Simple use cases | Complex labels |
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