<!doctype html>
<meta charset="utf-8">
<div id="before-print">Before print</div>
<canvas id="canvas" width="100" height="100"></canvas>
<script>
  onload = function() {
    // window.print() is special until after the load event is finished firing.
    setTimeout(function() {
      // This fires a timer which would trigger a navigation and prevent the
      // test from completing if it happens during window.print().
      let meta = document.createElement("meta");
      meta.setAttribute("http-equiv", "refresh");
      meta.setAttribute("content", "0; url=/unlikely-to-be-found");
      document.head.appendChild(meta);
      // This one should block until we're done printing, and block the
      // navigation too.
      window.print();
      meta.remove();
      document.body.insertAdjacentHTML('beforeend', `<div id="after-first-print">After first print</div>`);

      let canvas = document.getElementById("canvas");
      canvas.mozPrintCallback = function() {};

      // This one shouldn't, because the print callbacks need to run.
      window.print();

      document.body.insertAdjacentHTML('beforeend', `<div id="after-second-print">After second print</div>`);
    }, 0);
  }
</script>
