mousewheel-scroll-adjusted.html | Explore in Territory

<!DOCTYPE html>
<script src="../../../../../resources/testharness.js"></script>
<script src="../../../../../resources/testharnessreport.js"></script>
<script src='../../../../../resources/gesture-util.js'></script>
<style>
  html {
    height: 2000px;
    width: 2000px;
  }
</style>

<script>
const programmaticScrollY = 10;

// Schedule programmatic scroll once the user scroll has started. 
function instantScrollPromise() {
  return new Promise((resolve, reject) => {
    const scrollListener = () => {
      if (document.scrollingElement.scrollTop > 0) {
        document.scrollingElement.scrollBy({
            top: programmaticScrollY, behavior: "instant"});
        resolve();
      } else {
        reject('failed to scroll');
      }
    }
    window.addEventListener('scroll', scrollListener, { once: true });
  });
}

// Wait for 2 scrollend events to arrive. One from programmatic instant scroll,
// and another one from the smooth user scroll. 
function scrollendPromise() {
  return new Promise((resolve, reject) => {
    let scrollendCount = 0;
    window.addEventListener('scrollend', () => {
      scrollendCount++;
      if (scrollendCount == 2) {
        resolve();
      }
    })
  });
}

promise_test(async () => {
  await waitForCompositorCommit();
  await waitForScrollReset(document.scrollingElement);
  const pos = {x: 20, y: 20};
  await Promise.all([
    wheelTick(/*scroll_tick_x=*/0, /*scroll_tick_y=*/1, pos, SPEED_INSTANT),
    instantScrollPromise(),
    scrollendPromise(),
  ]);
  assert_equals(
      document.scrollingElement.scrollTop,
      pixelsPerTick() + programmaticScrollY);
}, "This test ensures that smooth input driven user scrolls get adjusted " +
   "by programmatic instant scrolls.");
</script>
chromium/third_party/blink/web_tests/virtual/threaded-prefer-compositing/fast/scroll-behavior/smooth-scroll/mousewheel-scroll-adjusted.html
