css/css-contain/contain-paint-012.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Containment Test: Paint containment fixed positioned descendants</title>
<link rel="author" title="Manuel Rego Casasnovas" href="mailto:rego@igalia.com">
<link rel="help" href="https://drafts.csswg.org/css-contain-1/#containment-paint">
<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
<meta name=assert content="Paint containment doesn't apply to inline elements so they don't act as containing block for fixed positioned descendants.">
<style>
#containing-block {
  transform: translateX(0);
  background: red;
  width: 100px;
  height: 100px;
  padding: 20px;
  box-sizing: border-box;
}

#contain-paint {
  contain: paint;
  width: 50px;
  height: 50px;
}

#fixed {
  position: fixed;
  bottom: 0;
  right: 0;
  background: green;
  width: 100%;
  height: 100%;
}
</style>
<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
<div id="containing-block">
  <span id="contain-paint">
    <div id="fixed"></div>
  </span>
</div>