intersection-observer/multicol-2.html

<!doctype html>
<title>IntersectionObserver with a fragmented intersection root.</title>
<link rel="help" href="https://bugzil.la/2013439">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
.multicol {
  width: 200px;
  height: 100px;
  columns: 2;
  column-fill: auto;
  gap: 0;
  background: grey;
}
.io-root {
  width: 100px;
  height: 200px;
}
.content {
  width: 100px;
  height: 90px;
  background: purple;
}
</style>
<div class=multicol><div id=r class=io-root>
  <!-- Push the observed box beyond the first column. -->
  <div style="height: 110px;"></div>
  <div id=c class=content></div>
</div></div>
<script>
promise_test(async function() {
  const options = {
    root: r,
    threshold: 1.0,
  };
  let observer;
  let entries = await new Promise(resolve => {
    observer = new IntersectionObserver(entries => {
      resolve(entries);
      observer.disconnect();
    }, options);
    observer.observe(c);
  });

  assert_equals(entries.length, 1, "Expect one entry since we observe one element");
  assert_true(entries[0].isIntersecting, "Should be intersecting the root");
});
</script>