<!DOCTYPE html>
<title>CSS Positioned Layout Module Test: 'overlay' is transitioned in and out of 'auto'</title>
<link rel="help" href="https://drafts.csswg.org/css-position-4/#overlay">
<link rel="help" href="https://html.spec.whatwg.org/multipage/popover.html">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#transition-in, #transition-out {
/* Force display:block both popover open or closed to not rely on
@starting-style or display transitions. */
display: block;
}
.enable-transitions :is(#transition-in, #transition-out) {
transition: overlay 60s step-end;
transition-behavior: allow-discrete;
}
</style>
<div id="container">
<div id="transition-in" popover></div>
<div id="transition-out" popover></div>
</div>
<script>
let transition_in = document.querySelector("#transition-in");
let transition_out = document.querySelector("#transition-out");
test(() => {
transition_out.showPopover();
assert_equals(getComputedStyle(transition_in).overlay, "none");
assert_equals(getComputedStyle(transition_out).overlay, "auto");
}, "Open the popover to be closed and verify computed overlay for both popovers");
container.className = "enable-transitions";
test(() => {
assert_true(transition_out.matches(':popover-open'));
assert_false(transition_in.matches(':popover-open'));
transition_in.showPopover();
assert_true(transition_in.matches(':popover-open'));
assert_false(transition_out.matches(':popover-open'));
assert_equals(getComputedStyle(transition_in).overlay, "none",
'Transition in should be delayed');
assert_equals(getComputedStyle(transition_out).overlay, "auto",
'Transition out should be delayed');
}, "Transition overlays");
</script>
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