css/css-overflow/column-scroll-marker-013.html

<!DOCTYPE html>
<html class="reftest-wait">
<title>multicol ::column::scroll-marker, add columns, keep target-current</title>
<link rel="author" title="Morten Stenshorne" href="mailto:mstensho@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-overflow-5/#scroll-marker-group-pseudo">
<link rel="help" href="https://drafts.csswg.org/css-overflow-5/#active-scroll-marker">
<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<style>
  #container {
    overflow: hidden;
    columns: 1;
    column-fill: auto;
    gap: 0;
    width: 100px;
    height: 100px;
    scroll-marker-group: before;
  }
  #container::scroll-marker-group {
    position: relative;
    left: -200px;
    display: flex;
    height: 100px;
  }
  #container::column::scroll-marker {
    width: 100px;
    height: 100px;
    flex: none;
    content: "";
  }
  #container::column::scroll-marker:target-current {
    background: green;
  }
</style>
<div style="position:absolute; width:100px; height:100px; background:red;"></div>
<div id="container">
  <div style="height:400px;"></div>
</div>
<script>
  container.scrollTo(200, 0);
  requestAnimationFrame(()=> {
    requestAnimationFrame(()=> {
      document.documentElement.classList.remove("reftest-wait");
      container.style.height = "150px";
    });
  });
</script>