gfx/layers/apz/test/mochitest/helper_main_thread_smooth_scroll_scrollend.html


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<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <script src="apz_test_utils.js"></script>
  <script src="apz_test_native_event_utils.js"></script>
  <script src="/tests/SimpleTest/EventUtils.js"></script>
  <script src="/tests/SimpleTest/paint_listener.js"></script>
  <style>
  html {
    overflow: hidden;
  }
  #spacer {
    height: 200vh;
    width: 200vw;
    position: absolute;
    background: linear-gradient(green, blue);
  }
  </style>
</head>
<body>
<div id="spacer"></div>
</body>
<script>
async function test() {
  let scrollendCount = 0;

  window.addEventListener("scrollend", e => {
    scrollendCount += 1;
  });

  window.scrollTo({ top: window.scrollY, behavior: 'smooth' });

  await promiseFrame();

  is(scrollendCount, 0, "Scrollend is not fired for a main thread no-op smooth scroll");

  window.scrollTo({ top: window.scrollY + 200, behavior: 'smooth' });

  await promiseOneEvent(window, "scrollend");

  is(scrollendCount, 1, "Scrollend is fired for a main thread smooth scroll");
}
waitUntilApzStable()
.then(test)
.then(subtestDone, subtestFailed);
</script>