backdrop-filter-edge-mirror-ref.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>backdrop-filter: Sampled pixels beyond edge should mirror back into the content.</title>
<link rel="author" href="mailto:[email protected]">
<link rel="help" href="https://drafts.fxtf.org/filter-effects-2/#backdrop-filter-operation">
<script src="../support/simulate-backdrop-blur.js"></script>

<div class="box border"></div>
<div class="box filter"></div>
<div style="position:absolute;top:100px;will-change:transform;">
  <p>Expected above: A pure white box with a very small hint of the 1px blue border blurred inside.</p>
</div>

<style>
.box {
  position: absolute;
  width: 100px;
  height: 100px;
  top: 8px;
  left: 8px;
  box-sizing: border-box;
}
.border {
  border: 1px solid blue;
}
</style>
<script>
simulateBackdropBlur(document.querySelector('.filter'), [document.querySelector('.border')], 10);
</script>

chromium/third_party/blink/web_tests/external/wpt/css/filter-effects/reference/backdrop-filter-edge-mirror-ref.html