chromium/third_party/blink/web_tests/external/wpt/css/css-scroll-anchoring/position-change-heuristic-display-none-to-abspos-change.html

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:[email protected]">
<link rel="author" title="Mozilla" href="https://mozilla.org">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1568778">
<link rel="help" href="https://drafts.csswg.org/css-scroll-anchoring/#suppression-triggers">
<style>
#hidden {
  display: none;
  background: red;
}
#spacer {
  height: calc(100vh + 200px); /* At least 200px of scroll range */
}
</style>
<table>
  <thead>
    <tr>
      <th>1
      <th>1
      <th>1
      <th>1
    </tr>
  </thead>
  <thead id="hidden">
    <tr>
      <th>1
      <th>1
      <th>1
      <th>1
    </tr>
  </thead>
  <tbody>
    <tr><td>0 <td>0 <td>0 <td>0 </tr>
    <tr><td>0 <td>0 <td>0 <td>0 </tr>
    <tr><td>0 <td>0 <td>0 <td>0 </tr>
    <tr><td>0 <td>0 <td>0 <td>0 </tr>
    <tr><td>0 <td>0 <td>0 <td>0 </tr>
    <tr><td>0 <td>0 <td>0 <td>0 </tr>
    <tr><td>0 <td>0 <td>0 <td>0 </tr>
  </tbody>
</table>
<div id="spacer"></div>
<script>
let isFirstEvent = true;
const targetScrollPosition = 100;
const hidden = document.querySelector("#hidden");
const t = async_test("Scroll offset doesn't get stuck in infinite scroll events when an element goes back and forth to display: none while changing abspos style");
window.onscroll = t.step_func(function() {
  hidden.style.display = "block";
  hidden.style.position = "absolute";
  hidden.style.visibility = "hidden";
  window.unused = hidden.offsetHeight;
  hidden.style.display = "";
  hidden.style.position = "";
  hidden.style.visibility = "";

  assert_true(isFirstEvent, "Shouldn't get more than one scroll event");
  isFirstEvent = false;
  requestAnimationFrame(t.step_func(function() {
    requestAnimationFrame(t.step_func_done(function() {
      assert_equals(document.scrollingElement.scrollTop, targetScrollPosition);
    }));
  }));
});

window.onload = t.step_func(function() {
  window.scrollTo(0, targetScrollPosition);
});
</script>