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<title>Test APZ hit-testing while overscrolled</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;
padding: 0;
#subframe {
width: 100px;
height: 100px;
overflow: scroll;
.spacer {
height: 5000px;
#target {
margin-left: 20px;
margin-top: 2px;
height: 4px;
width: 4px;
background: red;
<div id="subframe">
<div id="target"></div>
<div class="spacer"></div>
<div class="spacer"></div>
<script type="application/javascript">
async function test() {
var config = getHitTestConfig();
var utils = config.utils;
// Subframe hit testing of overscrolled APZCs does not yet work with WebRender
// (bug 1701831), so bail out early.
if (true) {
todo(false, "This test does not currently pass with WebRender");
// Activate the subframe. This both matches reality (if you're
// scrolling the subframe, it's active), and makes it easier
// to check for expected hit test outcomes.
utils.setDisplayPortForElement(0, 0, 500, 500, subframe, 1);
await promiseApzFlushedRepaints();
// Overscroll the subframe at the top, creating a gutter.
// Note that the size of the gutter will only be 8px, because
// setAsyncScrollOffset() applies the overscroll as a single delta,
// and current APZ logic that transforms a delta into an overscroll
// amount limits each delta to at most 8px.
utils.setAsyncScrollOffset(subframe, 0, -200);
// Check that the event hits the subframe frame in APZ.
// This is important because additional pan-gesture events in the gutter
// should continue to be handled and cause further overscroll (or
// relieving overscroll, depending on their direction).
let subframeBounds = subframe.getBoundingClientRect();
hitResult = hitTest({
x: subframeBounds.x + 50,
y: subframeBounds.y + 4
let subframeViewId = utils.getViewId(subframe);
"APZ hit-test in the subframe gutter");
// Now, perform a click in the gutter and check that APZ prevents
// the event from reaching Gecko.
// To be sure that no event was dispatched to Gecko, install the listener
// on the document, not the subframe.
// This makes sure we catch the case where the overscroll transform causes
// the event to incorrectly target the document.
let receivedClick = false;
let listener = function(e) {
receivedClick = true;
document.addEventListener("click", listener);
await synthesizeNativeMouseEventWithAPZ({
type: "click",
target: subframe,
offsetX: 50,
offsetY: 4
// Wait 10 frames for the event to maybe arrive, and if it
// hasn't, assume it won't.
for (let i = 0; i < 10; i++) {
await promiseFrame();
info("Finished waiting around for click event");
ok(!receivedClick, "Gecko received click event when it shouldn't have");
document.removeEventListener("click", listener);
// Finally, while still overscrolled, perform a click not in the gutter.
// This event should successfully go through to the web content, and
// be untransformed by the overscroll transform (such that it hits the
// content that is visually under the cursor).
let clickPromise = new Promise(resolve => {
document.addEventListener("click", function(e) {
info("event clientX = " + e.clientX);
info("event clientY = " + e.clientY);
is(, target, "Click while overscrolled hit intended target");
}, { once: true });
await synthesizeNativeMouseEventWithAPZ({
type: "click",
target: window,
offsetX: 22,
offsetY: 12
await clickPromise;
.then(subtestDone, subtestFailed);