Stroke Single Rectangle Side

Using `stroke-dasharray` to display the rectangle stroke at a single side.

by Roman Bruckner

HTML

<html>
<head>
    <link rel="stylesheet" type="text/css" href="https://cdnjs.cloudflare.com/ajax/libs/jointjs/3.4.4/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/3.4.4/joint.js"></script>
    
    </body>
</html>

JavaScript

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

const paper = new joint.dia.Paper({
  el: document.getElementById('paper'),
  width: 800,
  height: 900,
  model: graph,
  cellViewNamespace: joint.shapes,
  async: true,
  sorting: joint.dia.Paper.sorting.APPROX
});

const rect = new joint.shapes.standard.Rectangle({
  position: {
    x: 50,
    y: 50
  },
  size: {
    width: 100,
    height: 100
  },
  attrs: {
    body: {
      fill: 'transparent'
    }
  }
});

joint.dia.attributes.strokeSide = {
  offset: function(side, bbox, node) {
    let dasharray = 'none';
    const width = bbox.width;
    const height = bbox.height;
    switch (side) {
      case 'left': {
        dasharray = `0,${width * 2 + height},${height}`
        break;
      }
      case 'right': {
        dasharray = `0,${width},${height},${width + height}`
        break;
      }
      case 'top': {
        dasharray = `${width},${height * 2 + width}`
        break;
      }
      case 'bottom': {
        dasharray = `0,${width + height},${width},${height}`
        break;
      }
    }
    node.setAttribute('stroke-dasharray', dasharray);
  }
}
// Alternatively when using ESM modules
// dia.Element.define(attributes, prototype, { attributes: { ... }})

rect.clone().attr({
  body: {
    strokeSide: 'bottom',
    stroke: 'gray'
  }
}).addTo(graph);

rect.clone().attr({
  body: {
    strokeSide: 'left',
    stroke: 'red'
  }
}).addTo(graph);

rect.clone().attr({
  body: {
    strokeSide: 'top',
    stroke: 'blue'
  }
}).addTo(graph);

rect.clone().attr({
  body: {
    strokeSide: 'right',
    stroke: 'green'
  }
}).addTo(graph);