chromium/third_party/blink/web_tests/external/wpt/css/css-anchor-position/anchor-scroll-vrl.html

<!DOCTYPE html>
<title>Tests that anchor positioned scrolling works in vertical-rl writing mode</title>
<link rel="author" href="mailto:[email protected]">
<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#scrolling">
<link rel="match" href="reference/anchor-scroll-vrl-ref.html">
<link rel="stylesheet" href="/fonts/ahem.css">
<style>
:root {
  /* Prevents creatings scrollbar on the viewport due to anchored element's
   * layout position being out of the viewport.
   * TODO(crbug.com/1309178): Revisit this behavior.
   */
  overflow: clip;
}

body {
  font: 20px/1 Ahem;
  margin: 0;
  writing-mode: vertical-rl;
  white-space: nowrap;
}

#scroll-container {
  width: 400px;
  height: 400px;
  overflow: scroll;
}

#scroll-contents {
  width: 1000px;
  height: 1000px;
  position: relative;
}

#placefiller-above-anchor {
  width: 500px;
}

#placefiller-before-anchor {
  display: inline-block;
  height: 500px;
}

#anchor {
  anchor-name: --anchor;
}

#inner-anchored {
  color: green;
  position: absolute;
  top: anchor(top);
  left: anchor(right);
  position-anchor: --anchor;
}

#outer-anchored {
  color: yellow;
  position: absolute;
  top: anchor(top);
  right: anchor(left);
  position-anchor: --anchor;
}
</style>

<div style="position: relative;">
  <div id="scroll-container">
    <div id="scroll-contents">
      <div id="placefiller-above-anchor"></div>
      <div id="placefiller-before-anchor"></div>
      <span id="anchor">anchor</span>
      <div id="inner-anchored">inner-anchored</div>
    </div>
  </div>
  <div id="outer-anchored">outer-anchored</div>
</div>

<script>
const scroller = document.getElementById('scroll-container');
scroller.scrollTop = 450;
scroller.scrollLeft = -300;
</script>