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Test Info:
- Manifest: layout/base/tests/mochitest.toml
<!DOCTYPE HTML>
<html>
<!--
-->
<head>
  <meta charset="utf-8">
  <script src="/tests/SimpleTest/SimpleTest.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
  <style>
    @keyframes growWidth {
      from { width: 20px; }
      to   { width: 30px; }
    }
    .animating {
      animation: 1s growWidth infinite alternate;
    }
    #sometimesAnimated {
      background: blue;
      width: 10px;
      height: 10px;
    }
  </style>
</head>
<body onload="run()">
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1756269">Mozilla Bug 1756269</a>
<div id="display">
  <div id="sometimesAnimated"></div>
</div>
<pre id="test">
<script>
"use strict";
SimpleTest.waitForExplicitFinish();
SimpleTest.requestFlakyTimeout("need to allow time to pass so that we can " +
                               "detect unwanted extra refresh driver ticks");
const gUtils = SpecialPowers.getDOMWindowUtils(window);
async function startAnimAndExpectTick() {
  // Start an animation:
  sometimesAnimated.classList.add("animating");
  // double-rAF to flush pending paints:
  await new Promise(r => requestAnimationFrame(r));
  await new Promise(r => requestAnimationFrame(r));
  ok(gUtils.refreshDriverHasPendingTick,
     "Expecting refresh driver to be ticking when animated content is present");
  // clean up, i.e. remove animation:
  sometimesAnimated.classList.remove("animating");
  // double-rAF to flush pending paints:
  await new Promise(r => requestAnimationFrame(r));
  await new Promise(r => requestAnimationFrame(r));
}
async function expectTicksToStop() {
  let didStopTicking = false;
  // Note: The maximum loop count here is an arbitrary large value, just to let
  // us gracefully handle edge cases where multiple setTimeouts resolve before
  // a pending refresh driver tick.  Really, we just want to be sure the refresh
  // driver *eventually* stops ticking, and we can do so gracefully by polling
  // with some generous-but-finite number of checks here.
  for (var i = 0; i < 100; i++) {
    await new Promise(r => setTimeout(r, 8));
    if(!gUtils.refreshDriverHasPendingTick) {
      didStopTicking = true;
      break;
    }
  }
  ok(didStopTicking, "refresh driver should have eventually stopped ticking");
}
async function run() {
  // By default, the refresh driver ticks on its own for some period of time
  // after pageload.  Turn that off so we don't have to wait it out:
  await SpecialPowers.pushPrefEnv({'set':
                                   [['layout.keep_ticking_after_load_ms', 0]]});
  // Start out with a double-rAF, to flush paints from pageload:
  await new Promise(r => requestAnimationFrame(r));
  await new Promise(r => requestAnimationFrame(r));
  await startAnimAndExpectTick();
  await expectTicksToStop();
  await startAnimAndExpectTick();
  await expectTicksToStop();
  SimpleTest.finish();
}
</script>
</pre>
</body>
</html>