mermaid/instructions.md

Please help me to implement the tidy-tree algorithm.

• I have added a placeholder with the correct signature in packages/mermaid/src/rendering-util/layout-algorithms/tidy-tree/.

Replace the cytoscape layout with one using tidy-tree.

This is the API for tidy-tree:

# non-layered-tidy-tree-layout

Draw non-layered tidy trees in linear time.

> This a JavaScript port from the project [cwi-swat/non-layered-tidy-trees](https://github.com/cwi-swat/non-layered-tidy-trees), which is written in Java. The algorithm used in that project is from the paper by _A.J. van der Ploeg_, [Drawing Non-layered Tidy Trees in Linear Time](http://oai.cwi.nl/oai/asset/21856/21856B.pdf). There is another JavaScript port from that project [d3-flextree](https://github.com/Klortho/d3-flextree), which depends on _d3-hierarchy_. This project is dependency free.

## Getting started

### Installation

npm install non-layered-tidy-tree-layout

Or

yarn add non-layered-tidy-tree-layout

There's also a built verison: `dist/non-layered-tidy-tree-layout.js` for use with browser `<script>` tag, or as a Javascript module.

### Usage

```js
import { BoundingBox, Layout } from 'non-layered-tidy-tree-layout'

// BoundingBox(gap, bottomPadding)
const bb = new BoundingBox(10, 20)
const layout = new Layout(bb)
const treeData = {
  id: 0,
  width: 40,
  height: 40,
  children: [
    {
      id: 1,
      width: 40,
      height: 40,
      children: [{ id: 6, width: 400, height: 40 }]
    },
    { id: 2, width: 40, height: 40 },
    { id: 3, width: 40, height: 40 },
    { id: 4, width: 40, height: 40 },
    { id: 5, width: 40, height: 80 }
  ]
}
const { result, boundingBox } = layout.layout(treeData)

// result:
// {
//   id: 0,
//   x: 300,
//   y: 0,
//   width: 40,
//   height: 40,
//   children: [
//     {
//       id: 1,
//       x: 185,
//       y: 60,
//       width: 40,
//       height: 40,
//       children: [
//         { id: 6, x: 5, y: 120, width: 400, height: 40 }
//       ]
//     },
//     { id: 2, x: 242.5, y: 60, width: 40, height: 40 },
//     { id: 3, x: 300, y: 60, width: 40, height: 40 },
//     { id: 4, x: 357.5, y: 60, width: 40, height: 40 },
//     { id: 5, x: 415, y: 60, width: 40, height: 80 }
//   ]
// }
//
// boundingBox:
// {
//   left: 5,
//   right: 455,
//   top: 0,
//   bottom: 160
// }

The method Layout.layout modifies treeData inplace. It returns an object like { result: treeData, boundingBox: {left: num, right: num, top: num, bottom: num} }. result is the same object treeData with calculated coordinates, boundingBox are the coordinates for the whole tree:

The red dashed lines are the bounding boxes for each node. Layout.layout() produces coordinates to draw nodes, which are the grey boxes with black border.

The library also provides a class Tree and a method layout.

/**
 * Constructor for Tree.
 * @param {number} width - width of bounding box
 * @param {number} height - height of bounding box
 * @param {number} y - veritcal coordinate of bounding box
 * @param {array} children - a list of Tree instances
 */
new Tree(width, height, y, children)

/**
 * Calculate x, y coordindates and assign them to tree.
 * @param {Object} tree - a Tree object
 */
layout(tree)

In case your data structure are not the same as provided by the example above, you can refer to src/helpers.js to implement a Layout class that converts your data to a Tree, then call layout to calculate the coordinates for drawing.

License

MIT

Changelog

[2.0.1]

• Fixed bounding box calculation in Layout.getSize and Layout.assignLayout and Layout.layout

[2.0.0]

• Added Layout.layout
• Removed Layout.layoutTreeData

[1.0.0]

• Added Layout, BoundingBox, layout, Tree