animation-offscreen-to-onscreen.html

<!DOCTYPE html>
<html class="reftest-wait">
<title>Validates rendering of a transformed element when the element is initially off screen</title>
<link rel="help" href="https://www.w3.org/TR/css-animations-1">
<link rel="help" href="https://www.w3.org/TR/web-animations-1/#the-current-ready-promise">
<link rel="match" href="animation-offscreen-to-onscreen-ref.html">
<style type="text/css" media="screen">
  body {
    margin: 0;
  }

  @keyframes anim {
    from { transform: translate(100px, 0px); }
    to { transform: translate(100px, 0px); }
  }

  #box {
    position: absolute;
    left: 0px;
    top: 100px;
    height: 100px;
    width: 100px;
    margin: 0;
    background-color: green;
    transform: translate(-2000px, 0px);
    animation-duration: 10s;
    animation-direction: normal;
    animation-timing-function: linear;
    animation-name: anim;
  }
</style>
<body>
  <div id="box"></div>
</body>
<script src="/common/reftest-wait.js"></script>
<script src="support/testcommon.js"></script>
<script type="text/javascript">
  window.onload = async () => {
    await document.getAnimations()[0].ready;
    await waitForNextFrame();
    takeScreenshot();
  }
</script>
</html>

chromium/third_party/blink/web_tests/external/wpt/css/css-animations/animation-offscreen-to-onscreen.html