chromium/third_party/blink/web_tests/external/wpt/css/css-anchor-position/position-anchor-002.html

<!DOCTYPE html>
<title>Tests that 'position-anchor' property value is tree-scoped</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#position-anchor">
<link rel="author" href="mailto:[email protected]">
<link rel="match" href="position-anchor-ref.html">
<style>
.anchor {
  width: 100px;
  height: 100px;
  background: orange;
}

.target {
  position: fixed;
  background: lime;
  position-try-fallbacks: --pf;
  left: 999999px; /* force fallback */
}

@position-try --pf {
  top: anchor(bottom, 0px);
  left: anchor(left, 0px);
  width: anchor-size(width, 0px);
  height: anchor-size(height, 0px);
}

body {
  margin: 0;
}

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

#anchor1 {
  margin-left: 100px;
}

#anchor2 {
  margin-left: 300px;
  margin-top: 100px;
}

</style>

<div id="fake-anchor"></div>

<div id="anchor1" class="anchor">
  anchor1
  <div id="target1" class="target">target1</div>
</div>

<div id="anchor2" class="anchor">
  anchor2
  <div id="target2" class="target">target2</div>
</div>

<script>
for (let host of document.querySelectorAll('.anchor')) {
  let shadow = host.attachShadow({mode: 'open'});
  shadow.innerHTML = `
    <style>
      :host { anchor-name: --a; }
      ::slotted(.target) { position-anchor: --a; }
    </style>
    <slot></slot>
  `;
}
</script>