css/css-conditional/container-queries/scroll-state/scroll-state-scrollable-root.html

<!DOCTYPE html>
<title>@container: scroll-state(scrollable) matching viewport for root element</title>
<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#scrollable">
<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>
  :root {
    container-type: scroll-state;
  }
  #target {
    height: 5000px;
    --top: no;
    --bottom: no;
    @container scroll-state(scrollable: top) {
      --top: yes;
    }
    @container scroll-state(scrollable: bottom) {
      --bottom: yes;
    }
  }
</style>
<div id="target"></div>
<script>
  setup(() => assert_implements_scroll_state_container_queries());

  const root = document.documentElement;

  promise_test(async t => {
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target).getPropertyValue("--top"), "no");
    assert_equals(getComputedStyle(target).getPropertyValue("--bottom"), "yes");
    assert_equals(root.scrollTop, 0);
  }, "Check that scroll-state(scrollable) matches bottom before scroll");

  promise_test(async t => {
    root.scrollTop = 100;
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target).getPropertyValue("--top"), "yes");
    assert_equals(getComputedStyle(target).getPropertyValue("--bottom"), "yes");
  }, "Check that scroll-state(scrollable) matches both top and bottom in a middle position");

  promise_test(async t => {
    root.scrollTop = 5000;
    await waitForAnimationFrames(2);
    assert_equals(getComputedStyle(target).getPropertyValue("--top"), "yes");
    assert_equals(getComputedStyle(target).getPropertyValue("--bottom"), "no");
  }, "Check that scroll-state(scrollable) matches both top when scrolled to the end");

</script>