<!doctype html>
<title>@container-dependent elements respond to iframe size changes</title>
<link rel="help" href="https://drafts.csswg.org/css-contain-3/#size-container">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/cq-testcommon.js"></script>
<style>
  iframe {
    width: 200px;
    height: 40px;
  }
</style>
<iframe id=iframe srcdoc="
  <style>
    div#container {
      container-type: size;
      height: 20px;
    }
    div#child { color: red; }
    @container (min-width: 300px) {
      div#child { color: green; }
    }
  </style>
  <div id=container>
    <div id=child>Test</div>
  </div>
"></iframe>
<script>
  setup(() => assert_implements_container_queries());

  function waitForLoad(w) {
    return new Promise(resolve => w.addEventListener('load', resolve));
  }

  promise_test(async () => {
    await waitForLoad(window);
    let inner_div = iframe.contentDocument.querySelector('div#child');
    assert_equals(getComputedStyle(inner_div).color, 'rgb(255, 0, 0)');

    iframe.style = 'width:400px';
    assert_equals(getComputedStyle(inner_div).color, 'rgb(0, 128, 0)');
  })
</script>
