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<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="author" title="Mozilla" href="https://mozilla.org">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1559627">
<link rel="help" href="https://drafts.csswg.org/css-scroll-anchoring/#suppression-triggers">
<style>
body, h1 {
margin: 0
}
.sticky {
width: 100%;
top: 0;
left: 0;
}
.sticky > div {
width: 100%;
height: 50px;
background: darkblue;
}
header {
background: lightblue;
}
main {
background: lightgrey;
height: 200vh;
}
</style>
<header>
<h1>Some title</h1>
<span class="sticky"><div>Sticky header</div></span>
</header>
<main>
Some actual content.
</main>
<script>
const sticky = document.querySelector(".sticky");
const nonStickyOffset = sticky.firstElementChild.offsetTop;
const t = async_test("Scroll offset adjustments are correctly suppressed when changing the position of an inline");
let firstEvent = true;
window.onscroll = t.step_func(function() {
sticky.style.position =
document.documentElement.scrollTop > nonStickyOffset ? "fixed" : "static";
if (firstEvent) {
firstEvent = false;
requestAnimationFrame(t.step_func(function() {
requestAnimationFrame(t.step_func_done(function() {
assert_equals(sticky.style.position, "fixed", "Element should become and remain fixed")
}));
}));
}
});
window.onload = t.step_func(function() {
window.scrollTo(0, nonStickyOffset + 1);
});
</script>
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