scroll-timeline-snapshotting.html

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /scroll-animations/scroll-timelines/scroll-timeline-snapshotting.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<meta charset="utf-8">

<title>ScrollTimeline snapshotting</title>

<link rel="help" href="https://drafts.csswg.org/scroll-animations-1/#event-loop">

<link rel="help" href="https://github.com/whatwg/html/pull/11613">

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<script src="/resources/testdriver.js"></script>

<script src="/resources/testdriver-vendor.js"></script>

<script src="/resources/testdriver-actions.js"></script>

<script src="/web-animations/testcommon.js"></script>

<script src="./testcommon.js"></script>

<script src="/css/css-scroll-snap/support/common.js"></script>

<style>

  body {

    height: 800px;

    width: 800px;

</style>

<div id="log"></div>

<script>

'use strict';

promise_test(async t => {

  const scroller = document.scrollingElement;

  const maxScroll = scroller.scrollHeight - scroller.clientHeight;

  const timeline = new ScrollTimeline({source: scroller});

  scroller.scrollTo(0, 0);

  assert_equals(scroller.scrollTop, 0, "verify test pre-condition");

  scroller.scrollBy({top: 100, behavior: 'smooth'});

  // Wait for the scroll to change.

  await waitForScrollEvent(document);

  // The next frame the scroll changes, the scroll-timelines should not be

  // updated before the scroll events are dispatched. Store the scroll position

  // from the previous frame to compare the timeline to.

  let scroll_percentage = (scroller.scrollTop / maxScroll) * 100;

  await waitForScrollEvent(document);

  assert_percents_equal(

      timeline.currentTime,

      scroll_percentage,

      'Scroll timeline current time corresponds to the scroll position.');

}, 'ScrollTimeline current time is updated after programmatic animated ' +

   'scroll.');

</script>