examples/resizable-demo/overlay.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>Blockly Demo: Resizable Blockly (Part 2)</title>
  <script src="./node_modules/blockly/blockly_compressed.js"></script>
  <script src="./node_modules/blockly/blocks_compressed.js"></script>
  <script src="./node_modules/blockly/msg/en.js"></script>
  <style>
    html, body {
      height: 100%;
      margin: 0;
    }
    body {
      background-color: #fff;
      font-family: sans-serif;
      overflow: hidden;
    }
    h1 {
      font-weight: normal;
      font-size: 140%;
    }
    table {
      height: 100%;
      width: 100%;
    }
    #blocklyArea {
      height: 99%;
    }
  </style>
</head>
<body>
  <table>
    <tr>
      <td>
        <p>
          Once an <a href="index.html">area is defined</a>, Blockly can be
          injected and positioned over the area.
          A resize handler keeps it in position as the page changes.
        </p>

        <p>&rarr; More info on <a href="https://developers.google.com/blockly/guides/configure/web/resizable">injecting resizable Blockly</a>&hellip;</p>
      </td>
    </tr>
    <tr>
      <td id="blocklyArea">
      </td>
    </tr>
  </table>

  <div id="blocklyDiv" style="position: absolute"></div>

  <script>
    var toolbox = {
        "kind":"flyoutToolbox",
        "contents": [
          {
            "kind": "block",
            "type": "controls_if"
          },
          {
            "kind": "block",
            "type": "logic_compare"
          },
          {
            "kind": "block",
            "type": "controls_repeat_ext"
          },
          {
            "kind": "block",
            "type": "math_number",
            "fields": {"NUM": 123}
          },
          {
            "kind": "block",
            "type": "math_arithmetic"
          },
          {
            "kind": "block",
            "type": "text"
          },
          {
            "kind": "block",
            "type": "text_print"
          },
        ]
      };

    var blocklyArea = document.getElementById('blocklyArea');
    var blocklyDiv = document.getElementById('blocklyDiv');
    var demoWorkspace = Blockly.inject(blocklyDiv,
        {media: './node_modules/blockly/media/',
         toolbox: toolbox});
    var onresize = function(e) {
      // Compute the absolute coordinates and dimensions of blocklyArea.
      var element = blocklyArea;
      var x = 0;
      var y = 0;
      do {
        x += element.offsetLeft;
        y += element.offsetTop;
        element = element.offsetParent;
      } while (element);
      // Position blocklyDiv over blocklyArea.
      blocklyDiv.style.left = x + 'px';
      blocklyDiv.style.top = y + 'px';
      blocklyDiv.style.width = blocklyArea.offsetWidth + 'px';
      blocklyDiv.style.height = blocklyArea.offsetHeight + 'px';
      Blockly.svgResize(demoWorkspace);

      console.log('resize');
    };
    window.addEventListener('resize', onresize, false);
    onresize();
  </script>
</body>
</html>