extract tidy-tree layout into separate package

on-behalf-of: @Mermaid-Chart <hello@mermaidchart.com>

packages/mermaid-layout-tidy-tree/README.md

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+# @mermaid-js/layout-tidy-tree
+
+This package provides a bidirectional tidy tree layout engine for Mermaid based on the non-layered-tidy-tree-layout algorithm.
+
+> [!NOTE]
+> The Tidy Tree Layout engine will not be available in all providers that support mermaid by default.
+> The websites will have to install the @mermaid-js/layout-tidy-tree package to use the Tidy Tree layout engine.
+
+## Usage
+
+flowchart-tidy-tree TD
+A --> B
+A --> C
+
+---
+
+config:
+layout: tidy-tree
+
+---
+
+flowchart TD
+A --> B
+A --> C
+
+### With bundlers
+
+sh
+npm install @mermaid-js/layout-tidy-tree
+
+ts
+import mermaid from 'mermaid';
+import tidyTreeLayouts from '@mermaid-js/layout-tidy-tree';
+
+mermaid.registerLayoutLoaders(tidyTreeLayouts);
+
+### With CDN
+
+html
+
+<script type="module">
+  import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@11/dist/mermaid.esm.min.mjs';
+  import tidyTreeLayouts from 'https://cdn.jsdelivr.net/npm/@mermaid-js/layout-tidy-tree@0/dist/mermaid-layout-tidy-tree.esm.min.mjs';
+
+  mermaid.registerLayoutLoaders(tidyTreeLayouts);
+</script>
+
+## Supported layouts
+
+tidy-tree: The bidirectional tidy tree layout
+
+The bidirectional tidy tree layout algorithm creates two separate trees that grow horizontally in opposite directions from a central root node:
+Left tree: grows horizontally to the left (children alternate: 1st, 3rd, 5th...)
+Right tree: grows horizontally to the right (children alternate: 2nd, 4th, 6th...)
+
+This creates a balanced, symmetric layout that is ideal for mindmaps, organizational charts, and other tree-based diagrams.
+
+Layout Structure:
+[Child 3] ← [Child 1] ← [Root] → [Child 2] → [Child 4]
+↓ ↓ ↓ ↓
+[GrandChild] [GrandChild] [GrandChild] [GrandChild]

packages/mermaid-layout-tidy-tree/package.json

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+{
+  "name": "@mermaid-js/layout-tidy-tree",
+  "version": "0.1.0",
+  "description": "Tidy-tree layout engine for mermaid",
+  "module": "dist/mermaid-layout-tidy-tree.core.mjs",
+  "types": "dist/layouts.d.ts",
+  "type": "module",
+  "exports": {
+    ".": {
+      "import": "./dist/mermaid-layout-tidy-tree.core.mjs",
+      "types": "./dist/layouts.d.ts"
+    },
+    "./": "./"
+  },
+  "keywords": [
+    "diagram",
+    "markdown",
+    "tidy-tree",
+    "mermaid",
+    "layout"
+  ],
+  "scripts": {},
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/mermaid-js/mermaid"
+  },
+  "contributors": [
+    "Knut Sveidqvist",
+    "Sidharth Vinod"
+  ],
+  "license": "MIT",
+  "dependencies": {
+    "d3": "^7.9.0",
+    "non-layered-tidy-tree-layout": "^2.0.2"
+  },
+  "devDependencies": {
+    "@types/d3": "^7.4.3",
+    "mermaid": "workspace:^"
+  },
+  "peerDependencies": {
+    "mermaid": "^11.0.2"
+  },
+  "files": [
+    "dist"
+  ]
+}

packages/mermaid-layout-tidy-tree/src/index.ts

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+/**
+ * Bidirectional Tidy-Tree Layout Algorithm for Generic Diagrams
+ *
+ * This module provides a layout algorithm implementation using the
+ * non-layered-tidy-tree-layout algorithm for positioning nodes and edges
+ * in tree structures with a bidirectional approach.
+ *
+ * The algorithm creates two separate trees that grow horizontally in opposite
+ * directions from a central root node:
+ * - Left tree: grows horizontally to the left (children alternate: 1st, 3rd, 5th...)
+ * - Right tree: grows horizontally to the right (children alternate: 2nd, 4th, 6th...)
+ *
+ * This creates a balanced, symmetric layout that is ideal for mindmaps,
+ * organizational charts, and other tree-based diagrams.
+ *
+ * The algorithm follows the unified rendering pattern and can be used
+ * by any diagram type that provides compatible LayoutData.
+ */
+
+/**
+ * Render function for the bidirectional tidy-tree layout algorithm
+ *
+ * This function follows the unified rendering pattern used by all layout algorithms.
+ * It takes LayoutData, inserts nodes into DOM, runs the bidirectional tidy-tree layout algorithm,
+ * and renders the positioned elements to the SVG.
+ *
+ * Features:
+ * - Alternates root children between left and right trees
+ * - Left tree grows horizontally to the left (rotated 90° counterclockwise)
+ * - Right tree grows horizontally to the right (rotated 90° clockwise)
+ * - Uses tidy-tree algorithm for optimal spacing within each tree
+ * - Creates symmetric, balanced layouts
+ * - Maintains proper edge connections between all nodes
+ *
+ * Layout Structure:
+ * ```
+ * [Child 3] ← [Child 1] ← [Root] → [Child 2] → [Child 4]
+ *     ↓           ↓                     ↓           ↓
+ * [GrandChild]  [GrandChild]      [GrandChild]  [GrandChild]
+ * ```
+ *
+ * @param layoutData - Layout data containing nodes, edges, and configuration
+ * @param svg - SVG element to render to
+ * @param helpers - Internal helper functions for rendering
+ * @param options - Rendering options
+ */
+export { default } from './layouts.js';
+export * from './types.js';
+export * from './layout.js';
+export { render } from './render.js';

packages/mermaid-layout-tidy-tree/src/layout.test.ts

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+import { describe, it, expect, beforeEach, vi } from 'vitest';
+
+// Mock non-layered-tidy-tree-layout
+vi.mock('non-layered-tidy-tree-layout', () => ({
+  BoundingBox: vi.fn().mockImplementation(() => ({})),
+  Layout: vi.fn().mockImplementation(() => ({
+    layout: vi.fn().mockImplementation((treeData) => {
+      const result = { ...treeData };
+
+      if (result.id?.toString().startsWith('virtual-root')) {
+        result.x = 0;
+        result.y = 0;
+      } else {
+        result.x = 100;
+        result.y = 50;
+      }
+
+      if (result.children) {
+        result.children.forEach((child: any, index: number) => {
+          child.x = 50 + index * 100;
+          child.y = 100;
+
+          if (child.children) {
+            child.children.forEach((grandchild: any, gIndex: number) => {
+              grandchild.x = 25 + gIndex * 50;
+              grandchild.y = 200;
+            });
+          }
+        });
+      }
+
+      return {
+        result,
+        boundingBox: {
+          left: 0,
+          right: 200,
+          top: 0,
+          bottom: 250,
+        },
+      };
+    }),
+  })),
+}));
+
+import { executeTidyTreeLayout, validateLayoutData } from './layout.js';
+import type { LayoutResult } from './types.js';
+import type { LayoutData, MermaidConfig } from 'mermaid';
+
+describe('Tidy-Tree Layout Algorithm', () => {
+  let mockConfig: MermaidConfig;
+  let mockLayoutData: LayoutData;
+
+  beforeEach(() => {
+    mockConfig = {
+      theme: 'default',
+    } as MermaidConfig;
+
+    mockLayoutData = {
+      nodes: [
+        {
+          id: 'root',
+          label: 'Root',
+          isGroup: false,
+          shape: 'rect',
+          width: 100,
+          height: 50,
+          padding: 10,
+          x: 0,
+          y: 0,
+          cssClasses: '',
+          cssStyles: [],
+          look: 'default',
+        },
+        {
+          id: 'child1',
+          label: 'Child 1',
+          isGroup: false,
+          shape: 'rect',
+          width: 80,
+          height: 40,
+          padding: 10,
+          x: 0,
+          y: 0,
+          cssClasses: '',
+          cssStyles: [],
+          look: 'default',
+        },
+        {
+          id: 'child2',
+          label: 'Child 2',
+          isGroup: false,
+          shape: 'rect',
+          width: 80,
+          height: 40,
+          padding: 10,
+          x: 0,
+          y: 0,
+          cssClasses: '',
+          cssStyles: [],
+          look: 'default',
+        },
+        {
+          id: 'child3',
+          label: 'Child 3',
+          isGroup: false,
+          shape: 'rect',
+          width: 80,
+          height: 40,
+          padding: 10,
+          x: 0,
+          y: 0,
+          cssClasses: '',
+          cssStyles: [],
+          look: 'default',
+        },
+        {
+          id: 'child4',
+          label: 'Child 4',
+          isGroup: false,
+          shape: 'rect',
+          width: 80,
+          height: 40,
+          padding: 10,
+          x: 0,
+          y: 0,
+          cssClasses: '',
+          cssStyles: [],
+          look: 'default',
+        },
+      ],
+      edges: [
+        {
+          id: 'root_child1',
+          start: 'root',
+          end: 'child1',
+          type: 'edge',
+          classes: '',
+          style: [],
+          animate: false,
+          arrowTypeEnd: 'arrow_point',
+          arrowTypeStart: 'none',
+        },
+        {
+          id: 'root_child2',
+          start: 'root',
+          end: 'child2',
+          type: 'edge',
+          classes: '',
+          style: [],
+          animate: false,
+          arrowTypeEnd: 'arrow_point',
+          arrowTypeStart: 'none',
+        },
+        {
+          id: 'root_child3',
+          start: 'root',
+          end: 'child3',
+          type: 'edge',
+          classes: '',
+          style: [],
+          animate: false,
+          arrowTypeEnd: 'arrow_point',
+          arrowTypeStart: 'none',
+        },
+        {
+          id: 'root_child4',
+          start: 'root',
+          end: 'child4',
+          type: 'edge',
+          classes: '',
+          style: [],
+          animate: false,
+          arrowTypeEnd: 'arrow_point',
+          arrowTypeStart: 'none',
+        },
+      ],
+      config: mockConfig,
+      direction: 'TB',
+      type: 'test',
+      diagramId: 'test-diagram',
+      markers: [],
+    };
+  });
+
+  describe('validateLayoutData', () => {
+    it('should validate correct layout data', () => {
+      expect(() => validateLayoutData(mockLayoutData)).not.toThrow();
+    });
+
+    it('should throw error for missing data', () => {
+      expect(() => validateLayoutData(null as any)).toThrow('Layout data is required');
+    });
+
+    it('should throw error for missing config', () => {
+      const invalidData = { ...mockLayoutData, config: null as any };
+      expect(() => validateLayoutData(invalidData)).toThrow('Configuration is required');
+    });
+
+    it('should throw error for invalid nodes array', () => {
+      const invalidData = { ...mockLayoutData, nodes: null as any };
+      expect(() => validateLayoutData(invalidData)).toThrow('Nodes array is required');
+    });
+
+    it('should throw error for invalid edges array', () => {
+      const invalidData = { ...mockLayoutData, edges: null as any };
+      expect(() => validateLayoutData(invalidData)).toThrow('Edges array is required');
+    });
+  });
+
+  describe('executeTidyTreeLayout function', () => {
+    it('should execute layout algorithm successfully', async () => {
+      const result: LayoutResult = await executeTidyTreeLayout(mockLayoutData, mockConfig);
+
+      expect(result).toBeDefined();
+      expect(result.nodes).toBeDefined();
+      expect(result.edges).toBeDefined();
+      expect(Array.isArray(result.nodes)).toBe(true);
+      expect(Array.isArray(result.edges)).toBe(true);
+    });
+
+    it('should return positioned nodes with coordinates', async () => {
+      const result: LayoutResult = await executeTidyTreeLayout(mockLayoutData, mockConfig);
+
+      expect(result.nodes.length).toBeGreaterThan(0);
+      result.nodes.forEach((node) => {
+        expect(node.x).toBeDefined();
+        expect(node.y).toBeDefined();
+        expect(typeof node.x).toBe('number');
+        expect(typeof node.y).toBe('number');
+      });
+    });
+
+    it('should return positioned edges with coordinates', async () => {
+      const result: LayoutResult = await executeTidyTreeLayout(mockLayoutData, mockConfig);
+
+      expect(result.edges.length).toBeGreaterThan(0);
+      result.edges.forEach((edge) => {
+        expect(edge.startX).toBeDefined();
+        expect(edge.startY).toBeDefined();
+        expect(edge.midX).toBeDefined();
+        expect(edge.midY).toBeDefined();
+        expect(edge.endX).toBeDefined();
+        expect(edge.endY).toBeDefined();
+      });
+    });
+
+    it('should handle empty layout data gracefully', async () => {
+      const emptyData: LayoutData = {
+        ...mockLayoutData,
+        nodes: [],
+        edges: [],
+      };
+
+      await expect(executeTidyTreeLayout(emptyData, mockConfig)).rejects.toThrow(
+        'No nodes found in layout data'
+      );
+    });
+
+    it('should throw error for missing nodes', async () => {
+      const invalidData = { ...mockLayoutData, nodes: [] };
+
+      await expect(executeTidyTreeLayout(invalidData, mockConfig)).rejects.toThrow(
+        'No nodes found in layout data'
+      );
+    });
+
+    it('should handle empty edges (single node tree)', async () => {
+      const singleNodeData = {
+        ...mockLayoutData,
+        edges: [],
+        nodes: [mockLayoutData.nodes[0]],
+      };
+
+      const result = await executeTidyTreeLayout(singleNodeData, mockConfig);
+      expect(result).toBeDefined();
+      expect(result.nodes).toHaveLength(1);
+      expect(result.edges).toHaveLength(0);
+    });
+
+    it('should create bidirectional dual-tree layout with alternating left/right children', async () => {
+      const result = await executeTidyTreeLayout(mockLayoutData, mockConfig);
+
+      expect(result).toBeDefined();
+      expect(result.nodes).toHaveLength(5);
+
+      const rootNode = result.nodes.find((node) => node.id === 'root');
+      expect(rootNode).toBeDefined();
+      expect(rootNode!.x).toBe(0);
+      expect(rootNode!.y).toBe(20);
+
+      const child1 = result.nodes.find((node) => node.id === 'child1');
+      const child2 = result.nodes.find((node) => node.id === 'child2');
+      const child3 = result.nodes.find((node) => node.id === 'child3');
+      const child4 = result.nodes.find((node) => node.id === 'child4');
+
+      expect(child1).toBeDefined();
+      expect(child2).toBeDefined();
+      expect(child3).toBeDefined();
+      expect(child4).toBeDefined();
+
+      expect(child1!.x).toBeLessThan(rootNode!.x);
+      expect(child2!.x).toBeGreaterThan(rootNode!.x);
+      expect(child3!.x).toBeLessThan(rootNode!.x);
+      expect(child4!.x).toBeGreaterThan(rootNode!.x);
+
+      expect(child1!.x).toBeLessThan(-100);
+      expect(child3!.x).toBeLessThan(-100);
+
+      expect(child2!.x).toBeGreaterThan(100);
+      expect(child4!.x).toBeGreaterThan(100);
+    });
+
+    it('should correctly transpose coordinates to prevent high nodes from covering nodes above them', async () => {
+      const testData = {
+        ...mockLayoutData,
+        nodes: [
+          {
+            id: 'root',
+            label: 'Root',
+            isGroup: false,
+            shape: 'rect' as const,
+            width: 100,
+            height: 50,
+            padding: 10,
+            x: 0,
+            y: 0,
+            cssClasses: '',
+            cssStyles: [],
+            look: 'default',
+          },
+          {
+            id: 'tall-child',
+            label: 'Tall Child',
+            isGroup: false,
+            shape: 'rect' as const,
+            width: 80,
+            height: 120,
+            padding: 10,
+            x: 0,
+            y: 0,
+            cssClasses: '',
+            cssStyles: [],
+            look: 'default',
+          },
+          {
+            id: 'short-child',
+            label: 'Short Child',
+            isGroup: false,
+            shape: 'rect' as const,
+            width: 80,
+            height: 30,
+            padding: 10,
+            x: 0,
+            y: 0,
+            cssClasses: '',
+            cssStyles: [],
+            look: 'default',
+          },
+        ],
+        edges: [
+          {
+            id: 'root_tall',
+            start: 'root',
+            end: 'tall-child',
+            type: 'edge',
+            classes: '',
+            style: [],
+            animate: false,
+            arrowTypeEnd: 'arrow_point',
+            arrowTypeStart: 'none',
+          },
+          {
+            id: 'root_short',
+            start: 'root',
+            end: 'short-child',
+            type: 'edge',
+            classes: '',
+            style: [],
+            animate: false,
+            arrowTypeEnd: 'arrow_point',
+            arrowTypeStart: 'none',
+          },
+        ],
+      };
+
+      const result = await executeTidyTreeLayout(testData, mockConfig);
+
+      expect(result).toBeDefined();
+      expect(result.nodes).toHaveLength(3);
+
+      const rootNode = result.nodes.find((node) => node.id === 'root');
+      const tallChild = result.nodes.find((node) => node.id === 'tall-child');
+      const shortChild = result.nodes.find((node) => node.id === 'short-child');
+
+      expect(rootNode).toBeDefined();
+      expect(tallChild).toBeDefined();
+      expect(shortChild).toBeDefined();
+
+      expect(tallChild!.x).not.toBe(shortChild!.x);
+
+      expect(tallChild!.width).toBe(80);
+      expect(tallChild!.height).toBe(120);
+      expect(shortChild!.width).toBe(80);
+      expect(shortChild!.height).toBe(30);
+
+      const yDifference = Math.abs(tallChild!.y - shortChild!.y);
+      expect(yDifference).toBeGreaterThanOrEqual(0);
+    });
+  });
+});

packages/mermaid-layout-tidy-tree/src/layout.ts

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+import { BoundingBox, Layout } from 'non-layered-tidy-tree-layout';
+import type { MermaidConfig, LayoutData } from 'mermaid';
+import type {
+  LayoutResult,
+  TidyTreeNode,
+  PositionedNode,
+  PositionedEdge,
+  Node,
+  Edge,
+} from './types.js';
+
+/**
+ * Execute the tidy-tree layout algorithm on generic layout data
+ *
+ * This function takes layout data and uses the non-layered-tidy-tree-layout
+ * algorithm to calculate optimal node positions for tree structures.
+ *
+ * @param data - The layout data containing nodes, edges, and configuration
+ * @param config - Mermaid configuration object
+ * @returns Promise resolving to layout result with positioned nodes and edges
+ */
+export function executeTidyTreeLayout(
+  data: LayoutData,
+  _config: MermaidConfig
+): Promise<LayoutResult> {
+  let intersectionShift = 50;
+
+  return new Promise((resolve, reject) => {
+    try {
+      if (!data.nodes || !Array.isArray(data.nodes) || data.nodes.length === 0) {
+        throw new Error('No nodes found in layout data');
+      }
+
+      if (!data.edges || !Array.isArray(data.edges)) {
+        data.edges = [];
+      }
+
+      const { leftTree, rightTree, rootNode } = convertToDualTreeFormat(data);
+
+      const gap = 20;
+      const bottomPadding = 40;
+      intersectionShift = 30;
+
+      const bb = new BoundingBox(gap, bottomPadding);
+      const layout = new Layout(bb);
+
+      let leftResult = null;
+      let rightResult = null;
+      let leftBoundingBox = null;
+      let rightBoundingBox = null;
+
+      if (leftTree) {
+        const leftLayoutResult = layout.layout(leftTree);
+        leftResult = leftLayoutResult.result;
+        leftBoundingBox = leftLayoutResult.boundingBox;
+      }
+
+      if (rightTree) {
+        const rightLayoutResult = layout.layout(rightTree);
+        rightResult = rightLayoutResult.result;
+        rightBoundingBox = rightLayoutResult.boundingBox;
+      }
+
+      const positionedNodes = combineAndPositionTrees(
+        rootNode,
+        leftResult,
+        rightResult,
+        leftBoundingBox,
+        rightBoundingBox,
+        data
+      );
+      const positionedEdges = calculateEdgePositions(
+        data.edges,
+        positionedNodes,
+        intersectionShift
+      );
+
+      resolve({
+        nodes: positionedNodes,
+        edges: positionedEdges,
+      });
+    } catch (error) {
+      reject(error);
+    }
+  });
+}
+
+/**
+ * Convert LayoutData to dual-tree format (left and right trees)
+ *
+ * This function builds two separate tree structures from the nodes and edges,
+ * alternating children between left and right trees.
+ */
+function convertToDualTreeFormat(data: LayoutData): {
+  leftTree: TidyTreeNode | null;
+  rightTree: TidyTreeNode | null;
+  rootNode: TidyTreeNode;
+} {
+  const { nodes, edges } = data;
+
+  const nodeMap = new Map<string, Node>();
+  nodes.forEach((node) => nodeMap.set(node.id, node));
+
+  const children = new Map<string, string[]>();
+  const parents = new Map<string, string>();
+
+  edges.forEach((edge) => {
+    const parentId = edge.start;
+    const childId = edge.end;
+
+    if (parentId && childId) {
+      if (!children.has(parentId)) {
+        children.set(parentId, []);
+      }
+      children.get(parentId)!.push(childId);
+      parents.set(childId, parentId);
+    }
+  });
+
+  const rootNodeData = nodes.find((node) => !parents.has(node.id));
+  if (!rootNodeData && nodes.length === 0) {
+    throw new Error('No nodes available to create tree');
+  }
+
+  const actualRoot = rootNodeData ?? nodes[0];
+
+  const rootNode: TidyTreeNode = {
+    id: actualRoot.id,
+    width: actualRoot.width ?? 100,
+    height: actualRoot.height ?? 50,
+    _originalNode: actualRoot,
+  };
+
+  const rootChildren = children.get(actualRoot.id) ?? [];
+  const leftChildren: string[] = [];
+  const rightChildren: string[] = [];
+
+  rootChildren.forEach((childId, index) => {
+    if (index % 2 === 0) {
+      leftChildren.push(childId);
+    } else {
+      rightChildren.push(childId);
+    }
+  });
+
+  const leftTree = leftChildren.length > 0 ? buildSubTree(leftChildren, children, nodeMap) : null;
+
+  const rightTree =
+    rightChildren.length > 0 ? buildSubTree(rightChildren, children, nodeMap) : null;
+
+  return { leftTree, rightTree, rootNode };
+}
+
+/**
+ * Build a subtree from a list of root children
+ * For horizontal trees, we need to transpose width/height since the tree will be rotated 90°
+ */
+function buildSubTree(
+  rootChildren: string[],
+  children: Map<string, string[]>,
+  nodeMap: Map<string, Node>
+): TidyTreeNode {
+  const virtualRoot: TidyTreeNode = {
+    id: `virtual-root-${Math.random()}`,
+    width: 1,
+    height: 1,
+    children: rootChildren
+      .map((childId) => nodeMap.get(childId))
+      .filter((child): child is Node => child !== undefined)
+      .map((child) => convertNodeToTidyTreeTransposed(child, children, nodeMap)),
+  };
+
+  return virtualRoot;
+}
+
+/**
+ * Recursively convert a node and its children to tidy-tree format
+ * This version transposes width/height for horizontal tree layout
+ */
+function convertNodeToTidyTreeTransposed(
+  node: Node,
+  children: Map<string, string[]>,
+  nodeMap: Map<string, Node>
+): TidyTreeNode {
+  const childIds = children.get(node.id) ?? [];
+  const childNodes = childIds
+    .map((childId) => nodeMap.get(childId))
+    .filter((child): child is Node => child !== undefined)
+    .map((child) => convertNodeToTidyTreeTransposed(child, children, nodeMap));
+
+  return {
+    id: node.id,
+    width: node.height ?? 50,
+    height: node.width ?? 100,
+    children: childNodes.length > 0 ? childNodes : undefined,
+    _originalNode: node,
+  };
+}
+/**
+ * Combine and position the left and right trees around the root node
+ * Creates a bidirectional layout where left tree grows left and right tree grows right
+ */
+function combineAndPositionTrees(
+  rootNode: TidyTreeNode,
+  leftResult: TidyTreeNode | null,
+  rightResult: TidyTreeNode | null,
+  _leftBoundingBox: any,
+  _rightBoundingBox: any,
+  _data: LayoutData
+): PositionedNode[] {
+  const positionedNodes: PositionedNode[] = [];
+
+  const rootX = 0;
+  const rootY = 0;
+
+  const treeSpacing = rootNode.width / 2 + 30;
+  const leftTreeNodes: PositionedNode[] = [];
+  const rightTreeNodes: PositionedNode[] = [];
+
+  if (leftResult?.children) {
+    positionLeftTreeBidirectional(leftResult.children, leftTreeNodes, rootX - treeSpacing, rootY);
+  }
+
+  if (rightResult?.children) {
+    positionRightTreeBidirectional(
+      rightResult.children,
+      rightTreeNodes,
+      rootX + treeSpacing,
+      rootY
+    );
+  }
+
+  let leftTreeCenterY = 0;
+  let rightTreeCenterY = 0;
+
+  if (leftTreeNodes.length > 0) {
+    const leftTreeXPositions = [...new Set(leftTreeNodes.map((node) => node.x))].sort(
+      (a, b) => b - a
+    );
+    const firstLevelLeftX = leftTreeXPositions[0];
+    const firstLevelLeftNodes = leftTreeNodes.filter((node) => node.x === firstLevelLeftX);
+
+    if (firstLevelLeftNodes.length > 0) {
+      const leftMinY = Math.min(
+        ...firstLevelLeftNodes.map((node) => node.y - (node.height ?? 50) / 2)
+      );
+      const leftMaxY = Math.max(
+        ...firstLevelLeftNodes.map((node) => node.y + (node.height ?? 50) / 2)
+      );
+      leftTreeCenterY = (leftMinY + leftMaxY) / 2;
+    }
+  }
+
+  if (rightTreeNodes.length > 0) {
+    const rightTreeXPositions = [...new Set(rightTreeNodes.map((node) => node.x))].sort(
+      (a, b) => a - b
+    );
+    const firstLevelRightX = rightTreeXPositions[0];
+    const firstLevelRightNodes = rightTreeNodes.filter((node) => node.x === firstLevelRightX);
+
+    if (firstLevelRightNodes.length > 0) {
+      const rightMinY = Math.min(
+        ...firstLevelRightNodes.map((node) => node.y - (node.height ?? 50) / 2)
+      );
+      const rightMaxY = Math.max(
+        ...firstLevelRightNodes.map((node) => node.y + (node.height ?? 50) / 2)
+      );
+      rightTreeCenterY = (rightMinY + rightMaxY) / 2;
+    }
+  }
+
+  const leftTreeOffset = -leftTreeCenterY;
+  const rightTreeOffset = -rightTreeCenterY;
+
+  positionedNodes.push({
+    id: String(rootNode.id),
+    x: rootX,
+    y: rootY + 20,
+    section: 'root',
+    width: rootNode._originalNode?.width ?? rootNode.width,
+    height: rootNode._originalNode?.height ?? rootNode.height,
+    originalNode: rootNode._originalNode,
+  });
+
+  const leftTreeNodesWithOffset = leftTreeNodes.map((node) => ({
+    id: node.id,
+    x: node.x - (node.width ?? 0) / 2,
+    y: node.y + leftTreeOffset + (node.height ?? 0) / 2,
+    section: 'left' as const,
+    width: node.width,
+    height: node.height,
+    originalNode: node.originalNode,
+  }));
+
+  const rightTreeNodesWithOffset = rightTreeNodes.map((node) => ({
+    id: node.id,
+    x: node.x + (node.width ?? 0) / 2,
+    y: node.y + rightTreeOffset + (node.height ?? 0) / 2,
+    section: 'right' as const,
+    width: node.width,
+    height: node.height,
+    originalNode: node.originalNode,
+  }));
+
+  positionedNodes.push(...leftTreeNodesWithOffset);
+  positionedNodes.push(...rightTreeNodesWithOffset);
+
+  return positionedNodes;
+}
+
+/**
+ * Position nodes from the left tree in a bidirectional layout (grows to the left)
+ * Rotates the tree 90 degrees counterclockwise so it grows horizontally to the left
+ */
+function positionLeftTreeBidirectional(
+  nodes: TidyTreeNode[],
+  positionedNodes: PositionedNode[],
+  offsetX: number,
+  offsetY: number
+): void {
+  nodes.forEach((node) => {
+    const distanceFromRoot = node.y ?? 0;
+    const verticalPosition = node.x ?? 0;
+
+    const originalWidth = node._originalNode?.width ?? 100;
+    const originalHeight = node._originalNode?.height ?? 50;
+
+    const adjustedY = offsetY + verticalPosition;
+
+    positionedNodes.push({
+      id: String(node.id),
+      x: offsetX - distanceFromRoot,
+      y: adjustedY,
+      width: originalWidth,
+      height: originalHeight,
+      originalNode: node._originalNode,
+    });
+
+    if (node.children) {
+      positionLeftTreeBidirectional(node.children, positionedNodes, offsetX, offsetY);
+    }
+  });
+}
+
+/**
+ * Position nodes from the right tree in a bidirectional layout (grows to the right)
+ * Rotates the tree 90 degrees clockwise so it grows horizontally to the right
+ */
+function positionRightTreeBidirectional(
+  nodes: TidyTreeNode[],
+  positionedNodes: PositionedNode[],
+  offsetX: number,
+  offsetY: number
+): void {
+  nodes.forEach((node) => {
+    const distanceFromRoot = node.y ?? 0;
+    const verticalPosition = node.x ?? 0;
+
+    const originalWidth = node._originalNode?.width ?? 100;
+    const originalHeight = node._originalNode?.height ?? 50;
+
+    const adjustedY = offsetY + verticalPosition;
+
+    positionedNodes.push({
+      id: String(node.id),
+      x: offsetX + distanceFromRoot,
+      y: adjustedY,
+      width: originalWidth,
+      height: originalHeight,
+      originalNode: node._originalNode,
+    });
+
+    if (node.children) {
+      positionRightTreeBidirectional(node.children, positionedNodes, offsetX, offsetY);
+    }
+  });
+}
+
+/**
+ * Calculate the intersection point of a line with a circle
+ * @param circle - Circle coordinates and radius
+ * @param lineStart - Starting point of the line
+ * @param lineEnd - Ending point of the line
+ * @returns The intersection point
+ */
+function computeCircleEdgeIntersection(
+  circle: { x: number; y: number; width: number; height: number },
+  lineStart: { x: number; y: number },
+  lineEnd: { x: number; y: number }
+): { x: number; y: number } {
+  const radius = Math.min(circle.width, circle.height) / 2;
+
+  const dx = lineEnd.x - lineStart.x;
+  const dy = lineEnd.y - lineStart.y;
+  const length = Math.sqrt(dx * dx + dy * dy);
+
+  if (length === 0) {
+    return lineStart;
+  }
+
+  const nx = dx / length;
+  const ny = dy / length;
+
+  return {
+    x: circle.x - nx * radius,
+    y: circle.y - ny * radius,
+  };
+}
+
+/**
+ * Calculate intersection point of a line with a rectangle
+ * This is a simplified version that we'll use instead of importing from mermaid
+ */
+function intersection(
+  node: { x: number; y: number; width?: number; height?: number },
+  point1: { x: number; y: number },
+  point2: { x: number; y: number }
+): { x: number; y: number } {
+  const nodeWidth = node.width ?? 100;
+  const nodeHeight = node.height ?? 50;
+
+  const centerX = node.x;
+  const centerY = node.y;
+
+  const dx = point2.x - point1.x;
+  const dy = point2.y - point1.y;
+
+  if (dx === 0 && dy === 0) {
+    return { x: centerX, y: centerY };
+  }
+
+  const halfWidth = nodeWidth / 2;
+  const halfHeight = nodeHeight / 2;
+
+  let intersectionX = centerX;
+  let intersectionY = centerY;
+
+  if (Math.abs(dx) > Math.abs(dy)) {
+    if (dx > 0) {
+      intersectionX = centerX + halfWidth;
+      intersectionY = centerY + (halfWidth * dy) / dx;
+    } else {
+      intersectionX = centerX - halfWidth;
+      intersectionY = centerY - (halfWidth * dy) / dx;
+    }
+  } else {
+    if (dy > 0) {
+      intersectionY = centerY + halfHeight;
+      intersectionX = centerX + (halfHeight * dx) / dy;
+    } else {
+      intersectionY = centerY - halfHeight;
+      intersectionX = centerX - (halfHeight * dx) / dy;
+    }
+  }
+
+  return { x: intersectionX, y: intersectionY };
+}
+
+/**
+ * Calculate edge positions based on positioned nodes
+ * Now includes tree membership and node dimensions for precise edge calculations
+ * Edges now stop at shape boundaries instead of extending to centers
+ */
+function calculateEdgePositions(
+  edges: Edge[],
+  positionedNodes: PositionedNode[],
+  intersectionShift: number
+): PositionedEdge[] {
+  const nodeInfo = new Map<string, PositionedNode>();
+  positionedNodes.forEach((node) => {
+    nodeInfo.set(node.id, node);
+  });
+
+  return edges.map((edge) => {
+    const sourceNode = nodeInfo.get(edge.start ?? '');
+    const targetNode = nodeInfo.get(edge.end ?? '');
+
+    if (!sourceNode || !targetNode) {
+      return {
+        id: edge.id,
+        source: edge.start ?? '',
+        target: edge.end ?? '',
+        startX: 0,
+        startY: 0,
+        midX: 0,
+        midY: 0,
+        endX: 0,
+        endY: 0,
+        points: [{ x: 0, y: 0 }],
+        sourceSection: undefined,
+        targetSection: undefined,
+        sourceWidth: undefined,
+        sourceHeight: undefined,
+        targetWidth: undefined,
+        targetHeight: undefined,
+      };
+    }
+
+    const sourceCenter = { x: sourceNode.x, y: sourceNode.y };
+    const targetCenter = { x: targetNode.x, y: targetNode.y };
+
+    const isSourceRound = ['circle', 'cloud', 'bang'].includes(
+      sourceNode.originalNode?.shape ?? ''
+    );
+    const isTargetRound = ['circle', 'cloud', 'bang'].includes(
+      targetNode.originalNode?.shape ?? ''
+    );
+
+    let startPos = isSourceRound
+      ? computeCircleEdgeIntersection(
+          {
+            x: sourceNode.x,
+            y: sourceNode.y,
+            width: sourceNode.width ?? 100,
+            height: sourceNode.height ?? 100,
+          },
+          targetCenter,
+          sourceCenter
+        )
+      : intersection(sourceNode, sourceCenter, targetCenter);
+
+    let endPos = isTargetRound
+      ? computeCircleEdgeIntersection(
+          {
+            x: targetNode.x,
+            y: targetNode.y,
+            width: targetNode.width ?? 100,
+            height: targetNode.height ?? 100,
+          },
+          sourceCenter,
+          targetCenter
+        )
+      : intersection(targetNode, targetCenter, sourceCenter);
+
+    const midX = (startPos.x + endPos.x) / 2;
+    const midY = (startPos.y + endPos.y) / 2;
+
+    const points = [startPos];
+    if (sourceNode.section === 'left') {
+      points.push({
+        x: sourceNode.x - (sourceNode.width ?? 0) / 2 - intersectionShift,
+        y: sourceNode.y,
+      });
+    } else if (sourceNode.section === 'right') {
+      points.push({
+        x: sourceNode.x + (sourceNode.width ?? 0) / 2 + intersectionShift,
+        y: sourceNode.y,
+      });
+    }
+    if (targetNode.section === 'left') {
+      points.push({
+        x: targetNode.x + (targetNode.width ?? 0) / 2 + intersectionShift,
+        y: targetNode.y,
+      });
+    } else if (targetNode.section === 'right') {
+      points.push({
+        x: targetNode.x - (targetNode.width ?? 0) / 2 - intersectionShift,
+        y: targetNode.y,
+      });
+    }
+
+    points.push(endPos);
+
+    const secondPoint = points.length > 1 ? points[1] : targetCenter;
+    startPos = isSourceRound
+      ? computeCircleEdgeIntersection(
+          {
+            x: sourceNode.x,
+            y: sourceNode.y,
+            width: sourceNode.width ?? 100,
+            height: sourceNode.height ?? 100,
+          },
+          secondPoint,
+          sourceCenter
+        )
+      : intersection(sourceNode, secondPoint, sourceCenter);
+    points[0] = startPos;
+
+    const secondLastPoint = points.length > 1 ? points[points.length - 2] : sourceCenter;
+    endPos = isTargetRound
+      ? computeCircleEdgeIntersection(
+          {
+            x: targetNode.x,
+            y: targetNode.y,
+            width: targetNode.width ?? 100,
+            height: targetNode.height ?? 100,
+          },
+          secondLastPoint,
+          targetCenter
+        )
+      : intersection(targetNode, secondLastPoint, targetCenter);
+    points[points.length - 1] = endPos;
+
+    return {
+      id: edge.id,
+      source: edge.start ?? '',
+      target: edge.end ?? '',
+      startX: startPos.x,
+      startY: startPos.y,
+      midX,
+      midY,
+      endX: endPos.x,
+      endY: endPos.y,
+      points,
+      sourceSection: sourceNode?.section,
+      targetSection: targetNode?.section,
+      sourceWidth: sourceNode?.width,
+      sourceHeight: sourceNode?.height,
+      targetWidth: targetNode?.width,
+      targetHeight: targetNode?.height,
+    };
+  });
+}
+
+/**
+ * Validate layout data structure
+ * @param data - The data to validate
+ * @returns True if data is valid, throws error otherwise
+ */
+export function validateLayoutData(data: LayoutData): boolean {
+  if (!data) {
+    throw new Error('Layout data is required');
+  }
+
+  if (!data.config) {
+    throw new Error('Configuration is required in layout data');
+  }
+
+  if (!Array.isArray(data.nodes)) {
+    throw new Error('Nodes array is required in layout data');
+  }
+
+  if (!Array.isArray(data.edges)) {
+    throw new Error('Edges array is required in layout data');
+  }
+
+  return true;
+}

packages/mermaid-layout-tidy-tree/src/layouts.ts

@@ -0,0 +1,13 @@
+import type { LayoutLoaderDefinition } from 'mermaid';
+
+const loader = async () => await import(`./render.js`);
+
+const layouts: LayoutLoaderDefinition[] = [
+  {
+    name: 'tidy-tree',
+    loader,
+    algorithm: 'tidy-tree',
+  },
+];
+
+export default layouts;

packages/mermaid-layout-tidy-tree/src/non-layered-tidy-tree-layout.ts

@@ -0,0 +1,18 @@
+declare module 'non-layered-tidy-tree-layout' {
+  export class BoundingBox {
+    constructor(gap: number, bottomPadding: number);
+  }
+
+  export class Layout {
+    constructor(boundingBox: BoundingBox);
+    layout(data: any): {
+      result: any;
+      boundingBox: {
+        left: number;
+        right: number;
+        top: number;
+        bottom: number;
+      };
+    };
+  }
+}

packages/mermaid-layout-tidy-tree/src/render.ts

@@ -0,0 +1,175 @@
+import type { InternalHelpers, LayoutData, RenderOptions, SVG } from 'mermaid';
+import { executeTidyTreeLayout } from './layout.js';
+
+interface NodeWithPosition {
+  id: string;
+  x?: number;
+  y?: number;
+  width?: number;
+  height?: number;
+  domId?: any;
+  [key: string]: any;
+}
+
+/**
+ * Render function for bidirectional tidy-tree layout algorithm
+ *
+ * This follows the same pattern as ELK and dagre renderers:
+ * 1. Insert nodes into DOM to get their actual dimensions
+ * 2. Run the bidirectional tidy-tree layout algorithm to calculate positions
+ * 3. Position the nodes and edges based on layout results
+ *
+ * The bidirectional layout creates two trees that grow horizontally in opposite
+ * directions from a central root node:
+ * - Left tree: grows horizontally to the left (children: 1st, 3rd, 5th...)
+ * - Right tree: grows horizontally to the right (children: 2nd, 4th, 6th...)
+ */
+export const render = async (
+  data4Layout: LayoutData,
+  svg: SVG,
+  {
+    insertCluster,
+    insertEdge,
+    insertEdgeLabel,
+    insertMarkers,
+    insertNode,
+    log,
+    positionEdgeLabel,
+  }: InternalHelpers,
+  { algorithm: _algorithm }: RenderOptions
+) => {
+  const nodeDb: Record<string, NodeWithPosition> = {};
+  const clusterDb: Record<string, any> = {};
+
+  const element = svg.select('g');
+  insertMarkers(element, data4Layout.markers, data4Layout.type, data4Layout.diagramId);
+
+  const subGraphsEl = element.insert('g').attr('class', 'subgraphs');
+  const edgePaths = element.insert('g').attr('class', 'edgePaths');
+  const edgeLabels = element.insert('g').attr('class', 'edgeLabels');
+  const nodes = element.insert('g').attr('class', 'nodes');
+
+  log.debug('Inserting nodes into DOM for dimension calculation');
+
+  await Promise.all(
+    data4Layout.nodes.map(async (node) => {
+      if (node.isGroup) {
+        const clusterNode: NodeWithPosition = {
+          ...node,
+          id: node.id,
+          width: node.width,
+          height: node.height,
+        };
+        clusterDb[node.id] = clusterNode;
+        nodeDb[node.id] = clusterNode;
+
+        await insertCluster(subGraphsEl, node);
+      } else {
+        const nodeWithPosition: NodeWithPosition = {
+          ...node,
+          id: node.id,
+          width: node.width,
+          height: node.height,
+        };
+        nodeDb[node.id] = nodeWithPosition;
+
+        const nodeEl = await insertNode(nodes, node, {
+          config: data4Layout.config,
+          dir: data4Layout.direction || 'TB',
+        });
+
+        const boundingBox = nodeEl.node()!.getBBox();
+        nodeWithPosition.width = boundingBox.width;
+        nodeWithPosition.height = boundingBox.height;
+        nodeWithPosition.domId = nodeEl;
+
+        log.debug(`Node ${node.id} dimensions: ${boundingBox.width}x${boundingBox.height}`);
+      }
+    })
+  );
+
+  log.debug('Running bidirectional tidy-tree layout algorithm');
+
+  const updatedLayoutData = {
+    ...data4Layout,
+    nodes: data4Layout.nodes.map((node) => {
+      const nodeWithDimensions = nodeDb[node.id];
+      return {
+        ...node,
+        width: nodeWithDimensions.width ?? node.width ?? 100,
+        height: nodeWithDimensions.height ?? node.height ?? 50,
+      };
+    }),
+  };
+
+  const layoutResult = await executeTidyTreeLayout(updatedLayoutData, data4Layout.config);
+
+  log.debug('Positioning nodes based on bidirectional layout results');
+
+  layoutResult.nodes.forEach((positionedNode) => {
+    const node = nodeDb[positionedNode.id];
+    if (node?.domId) {
+      node.domId.attr('transform', `translate(${positionedNode.x}, ${positionedNode.y})`);
+
+      node.x = positionedNode.x;
+      node.y = positionedNode.y;
+
+      log.debug(`Positioned node ${node.id} at (${positionedNode.x}, ${positionedNode.y})`);
+    }
+  });
+
+  log.debug('Inserting and positioning edges');
+
+  await Promise.all(
+    data4Layout.edges.map(async (edge) => {
+      await insertEdgeLabel(edgeLabels, edge);
+
+      const startNode = nodeDb[edge.start ?? ''];
+      const endNode = nodeDb[edge.end ?? ''];
+
+      if (startNode && endNode) {
+        const positionedEdge = layoutResult.edges.find((e) => e.id === edge.id);
+
+        if (positionedEdge) {
+          log.debug('APA01 positionedEdge', positionedEdge);
+          const edgeWithPath = {
+            ...edge,
+            points: positionedEdge.points,
+          };
+          const paths = insertEdge(
+            edgePaths,
+            edgeWithPath,
+            clusterDb,
+            data4Layout.type,
+            startNode,
+            endNode,
+            data4Layout.diagramId
+          );
+
+          positionEdgeLabel(edgeWithPath, paths);
+        } else {
+          const edgeWithPath = {
+            ...edge,
+            points: [
+              { x: startNode.x ?? 0, y: startNode.y ?? 0 },
+              { x: endNode.x ?? 0, y: endNode.y ?? 0 },
+            ],
+          };
+
+          const paths = insertEdge(
+            edgePaths,
+            edgeWithPath,
+            clusterDb,
+            data4Layout.type,
+            startNode,
+            endNode,
+            data4Layout.diagramId
+          );
+          positionEdgeLabel(edgeWithPath, paths);
+        }
+      }
+    })
+  );
+
+  log.debug('Bidirectional tidy-tree rendering completed');
+};

packages/mermaid-layout-tidy-tree/src/types.ts

@@ -0,0 +1,71 @@
+import type { LayoutData } from 'mermaid';
+
+type Node = LayoutData['nodes'][number];
+type Edge = LayoutData['edges'][number];
+
+/**
+ * Positioned node after layout calculation
+ */
+export interface PositionedNode {
+  id: string;
+  x: number;
+  y: number;
+  section?: 'root' | 'left' | 'right';
+  width?: number;
+  height?: number;
+  originalNode?: Node;
+  [key: string]: unknown;
+}
+
+/**
+ * Positioned edge after layout calculation
+ */
+export interface PositionedEdge {
+  id: string;
+  source: string;
+  target: string;
+  startX: number;
+  startY: number;
+  midX: number;
+  midY: number;
+  endX: number;
+  endY: number;
+  sourceSection?: 'root' | 'left' | 'right';
+  targetSection?: 'root' | 'left' | 'right';
+  sourceWidth?: number;
+  sourceHeight?: number;
+  targetWidth?: number;
+  targetHeight?: number;
+  [key: string]: unknown;
+}
+
+/**
+ * Result of layout algorithm execution
+ */
+export interface LayoutResult {
+  nodes: PositionedNode[];
+  edges: PositionedEdge[];
+}
+
+/**
+ * Tidy-tree node structure compatible with non-layered-tidy-tree-layout
+ */
+export interface TidyTreeNode {
+  id: string | number;
+  width: number;
+  height: number;
+  x?: number;
+  y?: number;
+  children?: TidyTreeNode[];
+  _originalNode?: Node;
+}
+
+/**
+ * Tidy-tree layout configuration
+ */
+export interface TidyTreeLayoutConfig {
+  gap: number;
+  bottomPadding: number;
+}
+
+export type { Node, Edge };

packages/mermaid-layout-tidy-tree/tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "rootDir": "./src",
+    "outDir": "./dist",
+    "types": ["vitest/importMeta", "vitest/globals"]
+  },
+  "include": ["./src/**/*.ts"],
+  "typeRoots": ["./src/types"]
+}