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<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Test for Bug 1637113</title>
<script src="/tests/SimpleTest/paint_listener.js"></script>
<script src="/tests/SimpleTest/EventUtils.js"></script>
<script type="application/javascript" src="apz_test_native_event_utils.js"></script>
<script type="application/javascript" src="apz_test_utils.js"></script>
iframe {
margin-top: 1000px;
<iframe id="subframe" srcdoc="<div id='target' style='width:100px;height:100px;'>" width="100px" height="100px"></iframe>
<script type="application/javascript">
async function test() {
let utils = SpecialPowers.getDOMWindowUtils(window);
// Reproducing the bug requires three ingredients:
// 1. A large layout viewport offset.
// 2. A large visual viewport offset relative to the layout viewport.
// 3. An event that's dispatched in the iframe's document.
// We make the first two happen by doing a large visual scroll that will
// also drag the layout viewport with it part of the way.
let visualScrollPromise = new Promise(resolve => {
window.visualViewport.addEventListener("scroll", resolve, { once: true });
utils.scrollToVisual(0, 900, utils.UPDATE_TYPE_MAIN_THREAD,
await visualScrollPromise;
await promiseApzFlushedRepaints();
let target = subframe.contentWindow.document.getElementById("target");
// To get an event that's dispatched in the iframe's document,
// synthesize a native tap. This will synthesize three events:
// a mouse-move, a mouse-down, and a mouse-up. The mouse-move
// and mouse-down are dispatched in the root content document.
// The mouse-down causes the iframe to "capture" the mouse, which
// leads the mouse-up to be dispatched in the iframe's document
// instead. We listen for the mouse-up.
let mouseUpEvent = null;
let mouseUpPromise = new Promise(resolve => {
target.addEventListener("mouseup", function(e) {
mouseUpEvent = e;
await synthesizeNativeTap(target, 10, 10);
await mouseUpPromise;
is(, target, "mouseup event targeted the correct element");
.then(subtestDone, subtestFailed);