<!DOCTYPE html>
<title>Sticky positioned element should be observable by getBoundingClientRect.</title>
<link rel="help" href="https://www.w3.org/TR/css-position-3/#sticky-pos" />
<meta name="assert" content="This test checks that sticky positioned element
should be observable by getBoundingClientRect." />

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

<style>
body {
  margin: 0;
}

.container {
  overflow: scroll;
  width: 200px;
  height: 200px;
}

.spacer {
  width: 2000px;
  height: 2000px;
}

.box {
  width: 100px;
  height: 100px;
  background-color: green;
}

.sticky {
  position: sticky;
  top: 50px;
  left: 20px;
}
</style>

<div id="scroller1" class="container">
  <div id="sticky1" class="sticky box"></div>
  <div class="spacer"></div>
</div>

<script>
test(() => {
  var sticky = document.getElementById('sticky1');
  assert_equals(sticky.getBoundingClientRect().top, 50);
  document.getElementById('scroller1').scrollTop = 100;
  assert_equals(sticky.getBoundingClientRect().top, 50);
  sticky.style.position = 'relative';
  assert_equals(sticky.getBoundingClientRect().top, -50);
  sticky.style.position = 'sticky';
  assert_equals(sticky.getBoundingClientRect().top, 50);
}, 'sticky positioned element should be observable by getBoundingClientRect.');
</script>

<div id="scroller2" class="container">
  <div class="spacer"></div>
</div>

<script>
test(() => {
  var scroller = document.getElementById('scroller2');
  scroller.scrollTop = 100;
  scroller.scrollLeft = 75;

  var sticky = document.createElement('div');
  sticky.className = 'sticky box';
  scroller.insertBefore(sticky, scroller.querySelector('.spacer'));

  var sticky_bounds = sticky.getBoundingClientRect();
  var scroller_bounds = scroller.getBoundingClientRect();
  assert_equals(sticky_bounds.top, scroller_bounds.top + 50);
  assert_equals(sticky_bounds.left, scroller_bounds.left + 20);
}, 'getBoundingClientRect should be correct for sticky after script insertion');
</script>

<div id="scroller3" class="container">
  <div id="sticky3" class="sticky box"></div>
  <div class="spacer"></div>
</div>

<script>
test(() => {
  var scroller = document.getElementById('scroller3');
  var sticky = document.getElementById('sticky3');
  scroller.scrollTop = 100;
  scroller.scrollLeft = 75;

  var div = document.createElement('div');
  div.style.height = '65px';
  scroller.insertBefore(div, sticky);

  var sticky_bounds = sticky.getBoundingClientRect();
  var scroller_bounds = scroller.getBoundingClientRect();
  assert_equals(sticky_bounds.top, scroller_bounds.top + 50);
  assert_equals(sticky_bounds.left, scroller_bounds.left + 20);
}, 'getBoundingClientRect should be correct for sticky after script-caused layout');
</script>