css/css-overflow/column-scroll-marker-004.html

<!DOCTYPE html>
<title>::column::scroll-marker on multicol fieldset</title>
<link rel="author" title="Morten Stenshorne" href="mailto:mstensho@chromium.org">
<link rel="help" href="https://www.w3.org/TR/css-multicol-2/#column-pseudo">
<link rel="help" href="https://html.spec.whatwg.org/#anonymous-fieldset-content-box">
<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
<style>
  #container {
    overflow: hidden;
    columns: 3;
    column-fill: auto;
    gap: 0;
    height: 50px;
    margin: 0;
    border: 15px solid green;
    padding: 0;
    scroll-marker-group: before;
    background: red;
  }
  #container::scroll-marker-group {
    display: flex;
    height: 20px;
    background: red;
  }
  #container::column::scroll-marker {
    display: flex;
    width: 20px;
    height: 100%;
    background: green;
    content: "";
  }
</style>
<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div style="width:100px; height:100px; background:red;">
  <fieldset id="container">
    <legend style="width:50px; height:15px; background:green;"></legend>
    <div style="height:210px; background:green;"></div>
  </fieldset>
</div>