css/css-shadow-parts/part-after-combinator-invalidation.html

<!doctype html>
<meta charset="utf-8">
<link rel="help" href="https://drafts.csswg.org/css-shadow-parts">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1891296">
<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
<link rel="author" href="https://mozilla.org" title="Mozilla">
<link rel="match" href="part-after-combinator-invalidation-ref.html">
<style>
.inactive > ::part(content) {
  color: red;
}
</style>
<div class="inactive">
  <div id="host">
    <template shadowrootmode="open">
      <div part="content">What color am I?</div>
    </template>
  </div>
</div>
<script>
onload = () => {
  host.getBoundingClientRect();
  host.parentNode.className = "";
  host.getBoundingClientRect();
};
</script>