Source code

Revision control

Copy as Markdown

Other Tools

<meta charset="utf-8">
<title>Async key scrolling test, helper page</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">
// --------------------------------------------------------------------
// Async key scrolling test
// This test checks that a key scroll occurs asynchronously.
// The page contains a <div> that is large enough to make the page
// scrollable. We first synthesize a page down to scroll to the bottom
// of the page. Once we have reached the bottom of the page, we synthesize
// a page up to get us back to the top of the page.
// Once at the top, we request test data from APZ, rebuild the APZC tree
// structure, and use it to check that async key scrolling happened.
// --------------------------------------------------------------------
async function test() {
// Sanity check
is(checkHasAsyncKeyScrolled(), false, "expected no async key scrolling before test");
// Send a key to initiate a page scroll to take us to the bottom of the
// page. This scroll is done synchronously because APZ doesn't have
// current focus state at page load.
let scrollBottomPromise = new Promise(resolve => {
let checkBottom = function(e) {
if (window.scrollY < window.scrollMaxY) {
info("Reached final scroll position of sync KEY_End scroll");
window.removeEventListener("scroll", checkBottom);
window.addEventListener("scroll", checkBottom);
await scrollBottomPromise;
// Spin the refresh driver a few times, so that the AsyncScroll instance
// that was running the main-thread scroll animation finishes up and
// triggers any repaints that it needs to.
var utils = SpecialPowers.DOMWindowUtils;
for (var i = 0; i < 10; i++) {
// Wait for the APZ to reach a stable state as well, before dispatching
// the next key input or the default action won't occur.
await promiseApzFlushedRepaints();
is(checkHasAsyncKeyScrolled(), false, "expected no async key scrolling before KEY_Home dispatch");
// This scroll should be asynchronous now that the focus state is up to date.
let scrollTopPromise = new Promise(resolve => {
let checkTop = function(e) {
if (window.scrollY > 0) {
info("Reached final scroll position of async KEY_Home scroll");
window.removeEventListener("scroll", checkTop);
window.addEventListener("scroll", checkTop);
await scrollTopPromise;
// Wait for APZ to settle and then check that async scrolling happened.
await promiseApzFlushedRepaints();
is(checkHasAsyncKeyScrolled(), true, "expected async key scrolling after test");
function checkHasAsyncKeyScrolled() {
// Reconstruct the APZC tree structure in the last paint.
var apzcTree = getLastApzcTree();
var rcd = findRcdNode(apzcTree);
if (rcd) {
return rcd.hasAsyncKeyScrolled === "1";
info("Last paint rcd is null");
return false;
.then(subtestDone, subtestFailed);
<body style="height: 500px; overflow: scroll">
<a target="_blank" href="">Async key scrolling test</a>
<!-- Put enough content into the page to make it have a nonzero scroll range -->
<div style="height: 5000px"></div>