opaque-fractional-displayport-2.html

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<!DOCTYPE html>

<html lang="en" reftest-async-scroll>

<meta charset="utf-8">

<title>Make sure the scrolled layer is opaque even if the scrolled area is fractional</title>

<style>

body {

  margin: 0;

.scrollbox {

  margin: 50px;

  width: 200px;

  height: 200px;

  overflow: auto;

  /* Make the background "non-uniform" so that the scrolled layer does not

   * pull up a background color. */

  background: linear-gradient(to bottom, white, transparent);

.scrolled-contents {

  height: 300.2px;

  background-color: lime;

  box-sizing: border-box;

  border: 1px solid lime;

.transparent-overlap-of-fractional-edge {

  margin: -10px 20px 0;

  height: 40px;

  background-color: rgba(0, 0, 255, 0.5);

</style>

<body>

<div class="scrollbox"

     reftest-displayport-x="0" reftest-displayport-y="-100.2"

     reftest-displayport-w="200" reftest-displayport-h="300.2"

     reftest-async-scroll-x="0" reftest-async-scroll-y="0">

  <div class="scrolled-contents">

    <div class="transparent-overlap-of-fractional-edge reftest-opaque-layer">

      <!-- This element has the magic "reftest-opaque-layer" class which

           constitutes the actual test here. -->

    </div>

  </div>

</div>

<script>

document.querySelector(".scrollbox").scrollTop = 100000; /* will end up at 100.2 */

</script>