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<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-scroll-snap/#re-snap" />
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1948861">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#scroller {
scroll-snap-type: y mandatory;
width: 500px;
height: 200px;
overflow-y: scroll;
overflow-x: hidden;
scrollbar-width: none;
}
.child {
scroll-snap-align: start;
width: 500px;
height: 100%;
}
video {
height: 100%;
}
</style>
<div id="container">
<div id="scroller">
<div class="child">
<video src="dummy.webm" controls autoplay>
</div>
<div class="child">
<video src="dummy.webm" controls autoplay>
</div>
<div class="child">
<video src="dummy.webm" controls autoplay>
</div>
</div>
</div>
<script>
promise_test(async () => {
// Ensure this document has been already loaded.
if (document.readyState != "complete") {
await new Promise(resolve => window.addEventListener("load", resolve));
}
assert_equals(scroller.scrollTop, 0);
const scrollendPromise = new Promise(resolve => {
scroller.addEventListener("scrollend", resolve);
});
// Try to scroll downward, it will snap to the second green box.
scroller.scrollBy({ top: 100, behavior: "smooth" });
await scrollendPromise;
// Change the parent position style so that the scroll container will
// be reconstructed.
container.style.position = "fixed";
assert_equals(scroller.scrollTop, 200, "Should stay at the last snap point");
}, "Stay at the last snap point even after reconstrucing the scroll container");
</script>
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