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<meta charset="utf-8">
<meta name="viewport" content="width=device-width; initial-scale=1.0">
<title>Dragging the mouse on a scrollbar for a transformed, filtered scrollframe</title>
<script type="application/javascript" src="apz_test_native_event_utils.js"></script>
<script type="application/javascript" src="apz_test_utils.js"></script>
<script src="/tests/SimpleTest/paint_listener.js"></script>
<script type="text/javascript">
async function test() {
var scrollableDiv = document.getElementById("scrollable");
let scrollPromise = new Promise(resolve => {
scrollableDiv.addEventListener("scroll", resolve, {once: true});
// Scroll down a small amount (10px). The bug in this case is that the
// scrollthumb "jumps" most of the way down the scroll track because with
// WR enabled the filter and transform display items combine to generate an
// incorrect APZC tree, and the mouse position gets untransformed incorrectly.
// Given the scrollable height of 2000px and scrollframe height of 400px,
// the scrollthumb should be approximately 80px tall, and dragging it 10px
// should scroll approximately 50 pixels. If the bug manifests, it will get
// dragged an extra ~150px and scroll to approximately 1250px.
var dragFinisher = await promiseVerticalScrollbarDrag(scrollableDiv, 10, 10);
if (!dragFinisher) {
ok(true, "No scrollbar, can't do this test");
// the events above might be stuck in APZ input queue for a bit until the
// layer is activated, so we wait here until the scroll event listener is
// triggered.
await scrollPromise;
await dragFinisher();
// Flush everything just to be safe
await promiseOnlyApzControllerFlushed();
// In this case we just want to make sure the scroll position moved from 0
// which indicates the thumb dragging worked properly.
ok(scrollableDiv.scrollTop < 100, "Scrollbar drag resulted in a scroll position of " + scrollableDiv.scrollTop);
.then(subtestDone, subtestFailed);
<div style="position: fixed; left: 100px; top: 100px; width: 400px; height: 600px">
<div style="transform: translateY(150px); will-change: transform">
<div style="filter: grayscale(80%)">
<div id="scrollable" style="height: 400px; overflow-y: auto">
<div style="min-height: 2000px">
yay text