<!doctype HTML>
<html id=html>
<meta charset="utf8">
<title>Content Visibility: scroll position restoration</title>
<link rel="author" title="Vladimir Levin" href="mailto:vmpstr@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-contain/#content-visibility">
<meta name="assert" content="if an scroller is hidden via content-visibility and then shown again, its scroll offset should be restored">
<meta name="viewport" content="width=device-width">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/helper.js"></script>

<style>
.scroller {
  width: 100px;
  height: 500px;
  overflow-y: scroll;
}
.spacer { height: 3000px; }
.hidden { content-visibility: hidden; }
</style>

<div id=target class=scroller>
  <div class=spacer></div>
</div>
</style>

<script>
function removeHiddenAndScheduleTest(t) {
  target.classList.remove("hidden");
  requestAnimationFrame(() => {
    requestAnimationFrame(() => {
      testScrollTop(t);
    });
  });
}

function testScrollTop(t) {
  t.step(() => assert_equals(target.scrollTop, 2000));
  t.done();
}

async_test((t) => {
  target.scrollTop = 2000;
  target.classList.add("hidden");

  requestAnimationFrame(() => {
    requestAnimationFrame(() => {
      removeHiddenAndScheduleTest(t);
    });
  });
}, "Scroll offset is restored when content-visibility hidden is removed");
</script>
</html>
