fixed-position-change-out-of-view-in-view.html

<!DOCTYPE html>

<html>
<head>
  <style>
    #fixed1, #fixed2 {
        background-color: silver;
    }
  </style>
  <script type="text/javascript">
    if (window.testRunner && window.internals) {
      testRunner.dumpAsText();
      internals.settings.setPreferCompositingToLCDTextEnabled(true);

      addEventListener("load", function() {
        document.getElementById("layerTree1").innerText = internals.layerTreeAsText(document);
        document.getElementById("fixed1").style.top = "50px";
        document.getElementById("fixed2").style.height = "10px";
        document.getElementById("layerTree2").innerText = internals.layerTreeAsText(document);
        document.getElementById("fixed1").style.top = "-100px";
        document.getElementById("fixed2").style.height = "0px";
        document.getElementById("layerTree3").innerText = internals.layerTreeAsText(document);
      }, false);
    }
  </script>
</head>

<!-- Fixed position elements may skip compositing without a scrollable
ancestor. To make sure this test covers the intended scenario, we force the
body element to be tall, so that the FrameView is scrolling. -->
<body style="height: 4000px;">
  Layer tree when the fixed elements are out-of-view (should have just a root layer):
  <pre id="layerTree1"></pre>
  Layer tree when the fixed elements are in-view (both fixed elements should have layers):
  <pre id="layerTree2"></pre>
  Layer tree when the fixed elements are out-of-view again (should have just a root layer):
  <pre id="layerTree3"></pre>
  <div id="fixed1" style="position: fixed; top: -100px; left: 100px; width: 10px; height: 10px"></div>
  <div id="fixed2" style="position: fixed; top: 100px; left: 100px; width: 10px; height: 0px"></div>
</body>
</html>
chromium/third_party/blink/web_tests/compositing/layer-creation/fixed-position-change-out-of-view-in-view.html
