author moz-wptsync-bot <>
Thu, 02 Feb 2023 17:56:40 +0000
changeset 651741 193873a769705e43125bf048e01f18ac964d91b4
parent 572521 ed5c38a59629d53b960a6973b4d16b8b959884f8
permissions -rw-r--r--
Bug 1814704 - [wpt-sync] Update web-platform-tests to cfdf7a3b7129de7f29c9ff9e9d63a4cfb56696fd, a=testonly MANUAL PUSH: wpt sync bot wpt-head: cfdf7a3b7129de7f29c9ff9e9d63a4cfb56696fd wpt-type: landing

  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width; initial-scale=1.0">
  <title>Test for scenario in bug 1228407</title>
  <script type="application/javascript" src="apz_test_native_event_utils.js"></script>
  <script type="application/javascript" src="apz_test_utils.js"></script>
  <script src="/tests/SimpleTest/paint_listener.js"></script>
  <script type="application/javascript">

async function test() {
  let utils = SpecialPowers.getDOMWindowUtils(window);

  // Part of the problem in bug 1228407 was that the main-thread scroll
  // generation counter was continually increasing (due to scrollBy calls in
  // quick succession), and so repaint requests from APZ would get ignored (due
  // to stale scroll generation), and so the main thread scroll position would
  // never actually get updated. This loop exercises that case. The expected
  // behaviour (pre-APZ) was that the scrollBy call would actually start the
  // scroll animation and advance the scroll position a little bit, so the next
  // scrollBy call would move the animation destination a little bit, and so
  // the loop would continue advancing the scroll position. The bug resulted
  // in the scroll position not advancing at all.
  for (let i = 0; i < 100; i++) {
    document.scrollingElement.scrollBy({top:60, behavior: "smooth"});
    await promiseOnlyApzControllerFlushed();

  await promiseOnlyApzControllerFlushed();

  let scrollPos = document.scrollingElement.scrollTop;
  ok(scrollPos > 60, `Scrolled ${scrollPos}px, should be more than 60`);

waitUntilApzStable().then(test).then(subtestDone, subtestFailed);

    body {
      height: 5000px;
      background: linear-gradient(red, black);