<!DOCTYPE html>
<title>CSS Overflow Reference: Root element's scrollbar-gutter is accounted for when computing hypothetical box in fixed-pos positioning</title>
<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
<style>
:root {
  scrollbar-gutter: stable both-edges;
  writing-mode: vertical-lr;
}
body {
  margin: 0;
}
.box {
  width: 100px;
  height: 100px;
  background: green;
}
</style>

<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div class="box"></div>