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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 scrollframe inside nested transforms with a scale component</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 (7px). The bug in this case is that the
// scrollthumb "jumps" most of the way down the scroll track because with
// the bug, the code was incorrectly combining the transforms.
// Given the scrollable height of 0.7*2000px and scrollframe height of 0.7*400px,
// the scrollthumb should be approximately 0.7*80px = 56px tall. Dragging it 7px
// should scroll approximately 50 (unscaled) pixels. If the bug manifests, it will get
// dragged by a lot more and scroll to approximately 1300px.
var dragFinisher = await promiseVerticalScrollbarDrag(scrollableDiv, 7, 7, 0.7);
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();
// Ensure the scroll position ended up roughly where we wanted it (around
// 50px, but definitely less than 1300px).
ok(scrollableDiv.scrollTop < 100, "Scrollbar drag resulted in a scroll position of " + scrollableDiv.scrollTop);
.then(subtestDone, subtestFailed);
<div style="width: 500px; height: 300px; transform: translate(500px, 500px) scale(0.7)">
<div id="scrollable" style="transform: translate(-600px, -600px); overflow: scroll">
<div style="width: 600px; height: 400px">
<div style="width: 600px; height: 2000px; background-image: linear-gradient(red,blue)"></div>