<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>

body { height: 2000px; }
#scroller { overflow: scroll; width: 500px; height: 300px; }
.anchor {
  position: relative; height: 100px; width: 150px;
  background-color: #afa; border: 1px solid gray;
}
#forceScrolling { height: 500px; background-color: #fcc; }

</style>
<div id="scroller">
  <div id="innerChanger"></div>
  <div id="innerAnchor" class="anchor"></div>
  <div id="forceScrolling"></div>
</div>
<div id="outerChanger"></div>
<div id="outerAnchor" class="anchor"></div>
<script>

// Test that we ignore the clipped content when computing visibility otherwise
// we may end up with an anchor that we think is in the viewport but is not.

test(() => {
  document.querySelector("#scroller").scrollTop = 100;
  document.scrollingElement.scrollTop = 350;

  document.querySelector("#innerChanger").style.height = "200px";
  document.querySelector("#outerChanger").style.height = "150px";

  assert_equals(document.querySelector("#scroller").scrollTop, 300);
  assert_equals(document.scrollingElement.scrollTop, 500);
}, "Anchor selection with nested scrollers.");

</script>
