GitHub Discussion #1854

https://github.com/clientIO/joint/discussions/1854

by Roman Bruckner

HTML

<html>
<head>
    <link rel="stylesheet" type="text/css" href="https://cdnjs.cloudflare.com/ajax/libs/jointjs/3.6.2/joint.css" />
</head>
<body>
      <!-- content -->
      <div id="paper"></div>

      <!-- dependencies -->
        <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.1/jquery.js"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.20/lodash.min.js"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.4.0/backbone.js"></script>
        <script src="https://cdnjs.cloudflare.com/ajax/libs/jointjs/3.6.2/joint.js"></script>
    
    </body>
</html>

JavaScript

var graph = new joint.dia.Graph({}, {
  cellNamespace: joint.shapes
});

const paper = new joint.dia.Paper({
  el: document.getElementById('paper'),
  width: 800,
  height: 900,
  model: graph,
  defaultConnectionPoint: {
    name: 'boundary'
  },
  cellViewNamespace: joint.shapes,
  gridSize: 10,
  async: true,
  sorting: joint.dia.Paper.sorting.APPROX,
  linkPinning: false,
  defaultLink: () => new joint.shapes.standard.DoubleLink(),
  defaultRouter: (vertices, opt, linkView) => {

    /* Alternative */

    // const sv = linkView.getEndView('source');
    // const sourceBBox = sv ? sv.model.getBBox() : new g.Rect(linkView.model.source());
    // const tv = linkView.getEndView('target');        
    // const targetBBox = tv ? tv.model.getBBox() : new g.Rect(linkView.model.target());

    const sv = linkView.getEndView('source');
    const tv = linkView.getEndView('target');
    if (!sv || !tv) {
      // the link is not connected either to source or target
      // we draw a straigth line
      return [];
    }

    const sourceBBox = sv.model.getBBox();
    const targetBBox = tv.model.getBBox();

    const sa = linkView.getEndAnchor('source');
    const ta = linkView.getEndAnchor('target');
    const length = 40;
    const p1 = {
      x: sourceBBox.x + sourceBBox.width / 2,
      y: sourceBBox.y + sourceBBox.height + length
    };
    const p4 = {
      x: targetBBox.x + targetBBox.width / 2,
      y: targetBBox.y - length
    }
    const p2 = {
      x: (p1.x + p4.x) / 2,
      y: p1.y
    };
    const p3 = {
      x: p2.x,
      y: p4.y
    };
    return [p1, p2, ...vertices, p3, p4];
  }
});

// Example

var el1 = new joint.shapes.standard.Rectangle({
  position: {
    x: 10,
    y: 170
  },
  size: {
    width: 100,
    height: 90
  },
  attrs: {
    label: {
      text: 'A'
    }
  }
});
var el2 = new joint.shapes.standard.Rectangle({
  position: {
    x: 400,
    y: 150
  },
  size: {
    width: 100,
    height: 90
  },
  attrs: {
    label: {
     ...