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<title>APZ hit-testing of fixed content when async-scrolled</title>
<script type="application/javascript" src="apz_test_utils.js"></script>
<script type="application/javascript" src="apz_test_native_event_utils.js"></script>
<script src="/tests/SimpleTest/paint_listener.js"></script>
<meta name="viewport" content="width=device-width"/>
html, body {
margin: 0;
#fixed {
position: fixed;
height: 300px;
width: 100%;
top: 0;
background: blue;
#target {
margin-top: 100px;
margin-left: 100px;
height: 20px;
width: 20px;
background: red;
<div id="fixed">
<div id="target"></div>
<div id="make_root_scrollable" style="height: 5000px"></div>
<script type="application/javascript">
async function test() {
// Async scroll the page by 50 pixels using the mouse-wheel.
await promiseMoveMouseAndScrollWheelOver(document.body, 10, 10,
/* waitForScroll = */ false, /* scrollDelta = */ 50);
let clickPromise = new Promise(resolve => {
target.addEventListener("click", e => {
ok(true, "Target was hit");
e.stopPropagation(); // do not propagate event to |fixed| ancestor
fixed.addEventListener("click", e => {
// Since target's listener calls stopPropagation(), if we get here
// then the coordinates of the click event did not correspond to
// |target|, but somewhere else on |fixed|.
ok(false, "Fixed ancestor should not be hit");
// Synthesize a click at (110, 110), which should hit |target| (a
// descendant of |fixed|) regardless of the async scroll.
await synthesizeNativeMouseEventWithAPZ({
type: "click",
target: window,
offsetX: 110,
offsetY: 110
await clickPromise;
.then(subtestDone, subtestFailed);