css/css-contain/content-visibility/content-visibility-044.html

<!doctype HTML>
<html>
<meta charset="utf8">
<title>Content Visibility: slot moved after container is hidden</title>
<link rel="author" title="Vladimir Levin" href="mailto:vmpstr@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-contain/#content-visibility">
<meta name="assert" content="ensure that hidden slotted element can be updated">

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

<body style="margin: 0">

<div id=host>
<input id=slotted style="margin: 0">
<script>

async_test((t) => {
  let container = document.createElement("div");
  container.innerHTML = "<slot></slot>";
  let shadowRoot = host.attachShadow({ mode: "open" });
  shadowRoot.innerHTML = "<style>.hidden { content-visibility: hidden }</style>";
  shadowRoot.appendChild(container);

  t.step(async () => {
    container.classList.add("hidden");
    requestAnimationFrame(() => {
      assert_equals(slotted.offsetTop, 0);
      container.innerHTML = "<div style='height: 20px;'></div><slot></slot>";
      t.done();
    });
  });
});
</script>