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<meta charset="utf-8">
<meta name="viewport" content="width=device-width; initial-scale=1.0">
<title>Simple wheel scroll cancellation</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="application/javascript">
async function test() {
let wheelEventPromise = new Promise(resolve => {
// Add a non-passive listener on the document, so that we have a document-level
// APZ-aware listener, and the entire document is put in the dispatch-to-content
// region
document.addEventListener("wheel", function(e) {
// spin for 2 seconds to give APZ time to scroll, if the event region override
// is broken and it decides not to wait for the main thread. Note that it's
// possible the APZ controller thread is busy for whatever reason so APZ
// may not scroll. That might cause this test to only fail intermittently
// instead of consistently if the behaviour being tested regresses.
var now =;
while ( - now < 2000);
// Cancel the scroll. If this works then we know APZ waited for this listener
// to run.
}, { passive: false });
// Ensure APZ gets a paint with the d-t-c region
await promiseApzFlushedRepaints();
await synthesizeNativeWheel(document.body, 100, 100, 0, -50);
dump("Finished native wheel, waiting for listener to run...\n");
await wheelEventPromise;
await promiseOnlyApzControllerFlushed();
is(window.scrollY, 0, "check that the window didn't scroll");
if ( != window) {
dump("Running inside an iframe! stealing functions from\n");
window.subtestDone =;
window.SimpleTest =; =;
window.ok =;
<body style="height: 5000px; background-image: linear-gradient(green,red);">
This page should not be wheel-scrollable.