<!DOCTYPE html>
<meta charset="utf8">
<link rel="author" title="Vladimir Levin" href="mailto:vmpstr@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-scroll-anchoring/">
<meta name="assert" content="ensures that scroll anchoring does not recurse into contained offscreen elements">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>
body { height: 10000px; }
#container { contain: paint; }
#overflow {
  position: relative;
  top: 300px;
  height: 10px;
}
#anchor {
  width: 10px;
  height: 50px;
}
</style>

<div style="height: 800px"></div>
<div id="container" style="height: 40px">
  <div id=overflow></div>
</div>
<div id="changer" style="height: 150px"></div>
<div id=anchor></div>

<script>
test(() => {
  // Ensure #anchor is the only thing on screen.
  // Note that #overflow would be on screen if container
  // did not have layout and paint containment.
  document.scrollingElement.scrollTop = 1000;

  // Ensure anchor doesn't move if #changer shrinks.
  const offset = anchor.getBoundingClientRect().y;
  document.querySelector("#changer").style.height = "50px";
  assert_equals(anchor.getBoundingClientRect().y, offset);
}, "Contain: style paint container offscreen.");
</script>
