<html>
<body>
<svg xmlns="http://www.w3.org/2000/svg" height="100%" width="100%">
  <!-- The FO should be visible and completely cover the red rect. -->
  <rect id="rect" width="100" height="100" fill="red"/>
  <g>
    <foreignObject id="fo" width="100" height="100">
      <div style="background-color: green; width: 100px; height: 100px;"/>
    </foreignObject>
  </g>
</svg>
<script>
    var pos = Math.round(window.innerWidth * 2 / 3);
    document.getElementById('rect').setAttribute('x', pos);
    document.getElementById('fo').setAttribute('x', pos);
</script>
</body>
</html>