root-to-shared-animation-start.html

<!DOCTYPE html>
<html class=reftest-wait>
<link rel="help" href="https://drafts.csswg.org/css-view-transitions-1/">
<link rel="author" href="mailto:[email protected]">
<link rel="match" href="root-to-shared-animation-start-ref.html">

<script src="/common/reftest-wait.js"></script>

<style>
body {
  background: lightgreen;
  padding: 0;
  margin: 0;
}
#box {
  width: 100px;
  height: 120px;
  background: blue;
  contain: paint;
}

html::view-transition-group(*) { animation-delay: 300s; }
html::view-transition-new(*) { animation: unset; opacity: 0; }
html::view-transition-old(*) { animation: unset; opacity: 1; }
</style>

<div id=box></div>

<script>
failIfNot(document.startViewTransition, "Missing document.startViewTransition");

async function runTest() {
  document.startViewTransition(() => {
    document.documentElement.style.viewTransitionName = "none";
    box.style.viewTransitionName = "root";
    // We should not see the "live" body at all.
    document.body.style.background = "red";

    requestAnimationFrame(() => requestAnimationFrame(takeScreenshot));
  });
}
onload = () => requestAnimationFrame(() => requestAnimationFrame(runTest));
</script>

chromium/third_party/blink/web_tests/external/wpt/css/css-view-transitions/root-to-shared-animation-start.html