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<title>Test for bug 1695598</title>
<script src="/tests/SimpleTest/EventUtils.js"></script>
<script src="/tests/SimpleTest/paint_listener.js"></script>
<script type="application/javascript" src="apz_test_utils.js"></script>
<script type="application/javascript" src="apz_test_native_event_utils.js"></script>
<script type="text/javascript">
let scrollEvents = 100;
let i = 0;
// Scroll points
let numscrolls = 0;
let last_numscrolls = 0;
let start_scrolly = 0;
let missed_events = 0;
let missed_scroll_updates = 0;
let utils = SpecialPowers.getDOMWindowUtils(window);
let timeStamp = document.timeline.currentTime;
async function sendScrollEvent(aRafTimestamp) {
if (i < scrollEvents) {
if (timeStamp == document.timeline.currentTime) {
// If we are in a rAF callback at the same time stamp we've already
// sent a key event, skip it, otherwise we will not get the
// corresponding scroll event for the key event since it will be
// coalesced into a single scroll event.
timeStamp = document.timeline.currentTime;
// Sent a key event in a setTimeout callback so that it will be
// processed in between nsRefreshDriver::Tick calls, thus the async
// scroll triggered by the key event is going to be processed on the
// main-thread before RepaintRequests are processed inside
// nsRefreshDriver::Tick, which results there's an async scroll when
// RepaintRequests are processed.
setTimeout(async () => {
// "apz-repaints-flush" is notified in an early runner of
// nsRefreshDriver, which means it will be delivered inside
// a nsRefreshDriver::Tick call before rAF callbacks.
await promiseOnlyApzControllerFlushedWithoutSetTimeout();
// Wait an animationiteration event since animation events are fired
// before rAF callbacks and after scroll events so that it's a good
// place to tell whether the expected scroll event got fired or not.
await promiseOneEvent(document.getElementById("animation"),
"animationiteration", null);
if (numscrolls == last_numscrolls) {
if (window.scrollY <= start_scrolly) {
last_numscrolls = numscrolls;
start_scrolly = window.scrollY;
}, 0);
} else {
// There's a race condition even if we got an "apz-repaints-flush"
// notification but any scroll event isn't fired and scroll position
// isn't updated since the notification was corresponding to a layers
// update triggered by the key event above, which means there was no
// repaint request corresponding to APZ animation sample in the time
// frame. We allow the case here in the half of key events.
ok(missed_events < scrollEvents / 2, `missed event firing ${missed_events} times`);
ok(missed_scroll_updates < scrollEvents / 2, `missed scroll update ${missed_scroll_updates} times`);
async function endTest() {
document.removeEventListener("scroll", gotScroll);
function gotScroll() {
function startTest() {
document.addEventListener("scroll", gotScroll);
if (!isApzEnabled()) {
ok(true, "APZ not enabled, skipping test");
#content {
height: 10000vh;
background: repeating-linear-gradient(#EEE, #EEE 100px, #DDD 100px, #DDD 200px);
@keyframes anim {
from { opacity: 0; }; /* To avoid churning this scroll test */
to { opacity: 0; };
#animation {
position: absolute;
width: 100px;
height: 100px;
visibility: hidden; /* for skipping restyles on the main-thread */
animation-name: anim;
animation-iteration-count: infinite;
animation-duration: 1ms; /* to get an animationiteration event in each tick */
<div id="animation"></div>
<div id="content">