transition-ready-time-offscreen.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:
- /css/css-animations/transition-ready-time-offscreen.html - WPT Dashboard Interop Dashboard

<!doctype html>

<meta charset=utf-8>

<title>Transitions start at the same time regardless of on-screen status</title>

<link rel="help" href="https://drafts.csswg.org/css-animations-2/">

<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1888748">

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

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

<style>

.transition {

  width: 100px;

  height: 100px;

  background-color: blue;

  transition: translate 10000ms linear;

  will-change: translate;

  translate: 0;

.offscreen {

  background-color: purple;

  translate: -1000px;

</style>

<div class="transition"></div>

<div class="transition offscreen"></div>

<script>

'use strict';

promise_test(async t => {

  let [a, b] = document.querySelectorAll(".transition");

  // Ensure a paint happens to make sure a transition gets triggered (otherwise

  // getAnimations() would flush sync, and maybe not trigger a transition if

  // it's the first style of the elements).

  await new Promise(r => requestAnimationFrame(() => requestAnimationFrame(r)));

  // Trigger both transitions at the same time.

  a.style.translate = b.style.translate = "100px";

  let ta = a.getAnimations()[0];

  let tb = b.getAnimations()[0];

  await Promise.all([ta.ready, tb.ready]);

  assert_equals(ta.startTime, tb.startTime, "Both transitions should've started at the same time");

});

</script>