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<title>Test hit-testing on content which is revealed by async scrolling</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"/>
#parent {
width: 400px;
height: 400px;
overflow: auto;
#child {
margin-top: 200px;
width: 100%;
height: 100px;
overflow: auto;
#obscurer {
position: absolute;
top: 200px;
width: 400px;
height: 200px;
background: blue;
.spacer {
width: 100%;
height: 1000px;
background: green;
<div id="parent">
<div id="child">
<div class="spacer"></div>
<div class="spacer"></div>
<div id="obscurer"></div>
<script type="application/javascript">
async function test() {
var config = getHitTestConfig();
var utils = config.utils;
// Create APZCs for parent and child scrollers.
let parent = document.getElementById("parent"); // otherwise parent refers to window.parent
utils.setDisplayPortForElement(0, 0, 400, 1000, parent, 1);
utils.setDisplayPortForElement(0, 0, 400, 1000, child, 1);
await promiseApzFlushedRepaints();
// Async-scroll the parent scroller by 100 pixels, thereby revealing
// the child which was previous covered by "obscurer".
utils.setAsyncScrollOffset(parent, 0, 100);
// Give WebRender a chance to sample the test async scroll offset.
// Check that hit-testing on the region where the child scroller's
// contents are now revealed, successfully hits the scroller.
checkHitResult(hitTest({x: 200, y: 150}),
"child scroller");
.then(subtestDone, subtestFailed);