css/css-conditional/container-queries/scroll-state/scroll-state-stuck-layout-change.html

<!DOCTYPE html>
<title>@container: scroll-state(stuck) layout change</title>
<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#stuck">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/css/css-conditional/container-queries/support/cq-testcommon.js"></script>
<script src="/css/css-transitions/support/helper.js"></script>
<style>
  #scroller {
    overflow-y: scroll;
    height: 300px;
  }
  #filler {
    height: 100px;
  }
  #stuck {
    container-type: scroll-state;
    position: sticky;
    bottom: 0;
    height: 100px;
    background-color: teal;
  }
  #target {
    --stuck: no;
    @container scroll-state(stuck: bottom) {
      --stuck: yes;
    }
  }
</style>
<div id="scroller">
  <div id="filler"></div>
  <div id="stuck">
    <span id="target"></span>
  </div>
</div>
<script>
  setup(() => assert_implements_scroll_state_container_queries());

  promise_test(async t => {
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target).getPropertyValue("--stuck"), "no", "Initially not stuck");
  });

  promise_test(async t => {
    filler.style.height = "400px";
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target).getPropertyValue("--stuck"), "yes", "Stuck after #filler height changed");
  });
</script>