chromium/third_party/blink/web_tests/external/wpt/css/css-conditional/container-queries/display-contents.html

<!doctype html>
<title>@container and display:contents</title>
<link rel="help" href="https://drafts.csswg.org/css-conditional-5/#size-container">
<link rel="help" href="https://drafts.csswg.org/css-contain-2/#containment-size">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/cq-testcommon.js"></script>
<script>
  setup(() => assert_implements_container_queries());
</script>
<style>
  .container {
    container-type: inline-size;
    width: 30px;
    height: 30px;
    background: tomato;
  }
  .big {
    width: 50px;
    height: 50px;
    background: skyblue;
  }
  .contents {
    display: contents;
  }

  @container (width: 30px) {
    .target { --x:30; }
  }

  @container (width: 50px) {
    .target { --x:50; }
  }

  main {
    display: flex;
    flex-wrap: wrap;
  }

</style>

<main>
  <!-- Container is display:contents -->
  <div class="container contents">
    <div>
      <div class="target" id=target1></div>
    </div>
  </div>
  <script>
    test(function() {
      let s = getComputedStyle(target1);
      assert_equals(s.getPropertyValue('--x'), '');
    }, 'getComputedStyle when container is display:contents');
  </script>

  <!-- Container becomes display:contents -->
  <div id=container2 class="container">
    <div>
      <div class="target" id=target2></div>
    </div>
  </div>
  <script>
    test(function() {
      let s = getComputedStyle(target2);
      assert_equals(s.getPropertyValue('--x'), '30');
      container2.classList.add('contents');
      assert_equals(s.getPropertyValue('--x'), '');
      container2.classList.remove('contents');
      assert_equals(s.getPropertyValue('--x'), '30');
    }, 'getComputedStyle when container becomes display:contents');
  </script>

  <!-- Intermediate container becomes display:contents -->
  <div class="container">
    <div>
      <div id=container3 class="container">
        <div>
          <div class="target" id=target3></div>
        </div>
      </div>
    </div>
  </div>
  <script>
    test(function() {
      let s = getComputedStyle(target3);
      assert_equals(s.getPropertyValue('--x'), '30');
      container3.classList.add('contents');
      assert_equals(s.getPropertyValue('--x'), '');
      container3.classList.remove('contents');
      assert_equals(s.getPropertyValue('--x'), '30');
    }, 'getComputedStyle when intermediate container becomes display:contents');
  </script>
</main>