scrollIntoView-fixed-outside-of-viewport.html

<!DOCTYPE html>
<html>
<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1947223">
<style>
html {
  width: 200vw;
  height: 200vh;
}
.fixed {
  position: fixed;
  top: 0px;
  left: -200px;
  width: 100px;
  height: 100px;
  overflow: scroll;
}
#target {
  width: 100px;
  height: 100px;
}
</style>
<div class="fixed">
  <div id="target"></div>
  <div style="height: 200vh"></div>
</div>
<script>
promise_test(async t => {
  assert_equals(window.scrollY, 0);
  assert_equals(visualViewport.pageTop, 0);

  // Scroll the root scroll container a bit.
  const scrollPromise =
      new Promise(resolve => window.addEventListener("scroll", resolve));
  window.scrollTo(0, 10);
  await scrollPromise;
  assert_equals(window.scrollY, 10);
  assert_equals(visualViewport.pageTop, 10);

  window.addEventListener("scroll", () => {
    assert_unreached("Any scroll event should not be observed");
  });

  // Now trigger a scrollIntoView call to an element inside a position:fixed element.
  // NOTE: smooth scroll is a trigger of the firefox bug.
  document.querySelector('#target').scrollIntoView({ behavior: "smooth" });

  // Wait four rAFs to give a chance the scrollIntoView scrolls this document.
  await new Promise(resolve => requestAnimationFrame(resolve));
  await new Promise(resolve => requestAnimationFrame(resolve));
  await new Promise(resolve => requestAnimationFrame(resolve));
  await new Promise(resolve => requestAnimationFrame(resolve));

  assert_equals(window.scrollY, 10);
  assert_equals(visualViewport.pageTop, 10);
}, "Element.scrollIntoView doesn't scroll a position:fixed element outside of the layout viewport");
</script>