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Test Info: Warnings

  • This test gets skipped with pattern: OR os == 'android'
<title>Test for relative scroll offset updates (Bug 1453425)</title>
<meta charset="utf-8">
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<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>
<style type="text/css">
#frame {
width: 200px;
height: 400px;
overflow: scroll;
border: 1px solid black;
#first {
width: 200px;
height: 108px;
background-color: red;
#second {
width: 200px;
height: 692px;
background-color: green;
<div id="frame">
<div id="first"></div>
<div id="second"></div>
<script type="application/javascript">
async function test() {
var utils = SpecialPowers.DOMWindowUtils;
var elm = document.querySelector("#frame");
// Set a zero-margin displayport to ensure that the element is async-scrollable
utils.setDisplayPortMarginsForElement(0, 0, 0, 0, elm, 0);
elm.scrollTop = 0;
// Take over control of the refresh driver and don't allow a layer
// transaction until the main thread and APZ have processed two different
// scrolls.
await promiseApzFlushedRepaints();
// Scroll instantly on the main thread by (0, 100).
elm.scrollBy(0, 100);
// We are not using `scroll-behavior`
is(elm.scrollTop, 100, "the main thread scroll should be instant");
// Dispatch a wheel event to have APZ scroll by (0, 8). Wait for the wheel
// event to ensure that the APZ has processed the scroll.
await promiseNativeWheelAndWaitForWheelEvent(elm, 40, 40, 0, -8);
// APZ should be handling the wheel scroll
is(elm.scrollTop, 100, "the wheel scroll should be handled by APZ");
// Restore control of the refresh driver, allowing the main thread to send a
// layer transaction containing the (0, 100) scroll.
// Wait for all paints to finish and for the main thread to receive pending
// repaint requests with the scroll offset from the wheel event.
await promiseApzFlushedRepaints();
// The main thread scroll should not have overidden the APZ scroll, and we
// should see the effects of both scrolls.
ok(elm.scrollTop > 100, `expected element.scrollTop > 100. got element.scrollTop = ${elm.scrollTop}`);
if (isApzEnabled()) {
// Receiving a relative scroll offset update can cause scroll animations to
// be cancelled. This should be fixed, but for now we can still test this
// by disabling smooth scrolling.
pushPrefs([["general.smoothScroll", false]])
.then(SimpleTest.finish, SimpleTest.finishWithFailure);