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Test Info:

<!DOCTYPE HTML>
<html>
<!--
-->
<head>
<meta charset="utf-8">
<title>Test for Bug 1756118: A removed ResizeObserver shouldn't keep the refresh driver ticking</title>
<script src="/tests/SimpleTest/SimpleTest.js"></script>
<link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
</head>
<body onload="run()">
<div id="display">
<div id="resizeMe"></div>
</div>
<pre id="test">
<script>
"use strict";
SimpleTest.waitForExplicitFinish();
SimpleTest.requestFlakyTimeout("need to allow time to pass so that we can " +
"detect unwanted extra refresh driver ticks");
const gUtils = SpecialPowers.getDOMWindowUtils(window);
async function addAndRemoveResizeObserver(shouldResizeTarget) {
// Register a resize observer:
let ro = new ResizeObserver(function() { info("ResizeObserver callback"); });
ro.observe(resizeMe);
// double-rAF to flush pending paints:
await new Promise(r => requestAnimationFrame(r));
await new Promise(r => requestAnimationFrame(r));
ok(gUtils.refreshDriverHasPendingTick,
"Expecting refresh driver to be ticking, with ResizeObserver registered");
// Unregister resize observer:
ro.unobserve(resizeMe);
// double-rAF to flush pending paints:
await new Promise(r => requestAnimationFrame(r));
await new Promise(r => requestAnimationFrame(r));
// ...and importantly: make one additional change to the document.
// This causes a refresh driver tick, which in buggy builds causes
// the refresh driver to keep ticking indefinitely. (In buggy builds, this
// bonus tick notifies our ResizeObserverController, and it never unregisters
// and hence keeps the refresh driver ticking from that point on.)
resizeMe.style.height = "100px";
}
async function expectTicksToStop() {
let didStopTicking = false;
// Note: The maximum loop count here is an arbitrary large value, just to let
// us gracefully handle edge cases where multiple setTimeouts resolve before
// a pending refresh driver tick. Really, we just want to be sure the refresh
// driver *eventually* stops ticking, and we can do so gracefully by polling
// with some generous-but-finite number of checks here.
for (var i = 0; i < 100; i++) {
await new Promise(r => setTimeout(r, 8));
if(!gUtils.refreshDriverHasPendingTick) {
didStopTicking = true;
break;
}
}
ok(didStopTicking, "refresh driver should have eventually stopped ticking");
}
async function run() {
// By default, the refresh driver ticks on its own for some period of time
// after pageload. Turn that off so we don't have to wait it out:
await SpecialPowers.pushPrefEnv({'set':
[['layout.keep_ticking_after_load_ms', 0]]});
// Start out with a double-rAF, to flush paints from pageload:
await new Promise(r => requestAnimationFrame(r));
await new Promise(r => requestAnimationFrame(r));
await addAndRemoveResizeObserver(true);
await expectTicksToStop();
SimpleTest.finish();
}
</script>
</pre>
</body>
</html>