css/cssom-view/client-props-root.html

<!doctype html>
<title>client* on the scrolling element</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<link rel="help" href="https://drafts.csswg.org/cssom-view/#extension-to-the-element-interface">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1654769">
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="author" title="Mozilla" href="https://mozilla.org">
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<style>
  :root {
    /* Ensure the width of the root element's box is smaller than the viewport. */
    margin: 5px;
    /* Remove the scrollbars so that we can test {Width, Height}. */
    scrollbar-width: none;
    /* Would love to add a border but https://github.com/w3c/csswg-drafts/issues/5363 */
  }
</style>
<div style="height: 200vh; width: 200vw"></div>
<script>
test(function() {
  scrollTo(100, 100);
  assert_equals(document.documentElement.clientTop, 0, "Client top doesn't depend on scrolling");
  assert_equals(document.documentElement.clientLeft, 0, "Client left doesn't depend on scrolling");
  assert_equals(document.documentElement.clientWidth, window.innerWidth, "Without scrollbars, client width should match viewport width");
  assert_equals(document.documentElement.clientHeight, window.innerHeight, "Without scrollbars, client height should match viewport height");
}, "client* properties on the root element");
</script>