Link to Link Connection

by Roman Bruckner

HTML

<html>
<head>
    <link rel="stylesheet" type="text/css" href="https://cdnjs.cloudflare.com/ajax/libs/jointjs/3.6.5/joint.css" />
</head>
<body>
      <!-- content -->
      <div id="paper"></div>

      <!-- dependencies -->
        <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/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/3.6.5/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,
//  connectionStrategy: joint.connectionStrategies.pinAbsolute,
  defaultLink: (elementView, magnet) => {
    return new joint.shapes.standard.Link({
      attrs: {
        line: {
          stroke: 'red'
        }
      }
    });
  },
  connectionStrategy: (
    end,
    view,
    magnet,
    coords
  ) => {
    const bbox = view.getNodeUnrotatedBBox(magnet);
    const p = bbox.pointNearestToPoint(coords);
    return joint.connectionStrategies.pinRelative(end, view, magnet, p);
  },

  validateConnection: (srcView, _, tgtView) => {
    const src = srcView.model;
    const tgt = tgtView.model;
    if (src === tgt) return false;
    return true;
  },
});



// Example

var el1 = new joint.shapes.standard.Rectangle({
  position: {
    x: 10,
    y: 170
  },
  size: {
    width: 100,
    height: 90
  }
});

var el2 = el1.clone().position(300, 100);
var el3 = el1.clone().position(300, 400);


const l1 = new joint.shapes.standard.Link({
  source: {
    id: el2.id
  },
  target: {
    id: el3.id
  },
  attrs: {
/*   root: {
    magnet: false
  }, */
    line: {
      stroke: 'blue'
    }
  }
});

graph.resetCells([el1, el2, el3, l1]);

paper.unfreeze();

el1.findView(paper).addTools(new joint.dia.ToolsView({
  tools: [new joint.linkTools.Connect({
    x: 'calc(w)',
    y: 'calc(h/2)'
  })]
}))