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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;
iframe {
width: 100%;
height: 400px;
margin-top: 100px;
padding: 0px;
border: 0px;
display: block;
<iframe id="subdoc" srcdoc="<!DOCTYPE HTML>
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_scrollable' style='height: 5000px'></div>
<div id="make_root_scrollable" style="height: 5000px"></div>
<script type="application/javascript">
async function test() {
// Async scroll the root content document by 50 pixels.
// This test uses a touch-drag (with relevant prefs set in
// test_group_hittest-2.html to e.g. disable flings)
// rather than mousewheel so that we have control over the
// precise amount scrolled.
let transformEndPromise = promiseTransformEnd();
await synthesizeNativeTouchDrag(document.documentElement, 10, 10, 0, -50);
await transformEndPromise;
// Set up listeners that pass the test if we correctly hit |target|
// but fail it if we hit something else.
let target =;
let fixed = subdoc.contentWindow.fixed;
let clickPromise = new Promise(resolve => {
target.addEventListener("click", e => {
ok(true, "Target was hit");
e.stopPropagation(); // do not propagate event to ancestors
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|.
// TODO(bug 1786369): Ensure the parent is not hit once this is
// no longer an intermittent failure.
todo(false, "Fixed ancestor should not be hit");
window.addEventListener("click", e => {
// Similarly, the root content document's window should not be hit.
ok(false, "Root document should not be hit");
// Synthesize a click which should hit |target|.
// The y-coordinate relative to the window is:
// 100 pixel margin of iframe from top of root content doc
// + 100 pixel margin of target from top of iframe
// - 50 pixels async scrolled
// + 10 pixels to get us to the middle of the 20px-width target
await synthesizeNativeMouseEventWithAPZ({
type: "click",
target: window,
offsetX: 110,
offsetY: 160
await clickPromise;
.then(subtestDone, subtestFailed);