css/css-contain/content-visibility/content-visibility-with-popover-top-layer-006.html

<!doctype html>
<meta charset="utf8">
<title>CSS Content Visibility: offscreen c-v auto content is relevant when in top layer</title>
<link rel="author" title="Rob Buis" href="mailto:rbuis@igalia.com">
<link rel="help" href="https://drafts.csswg.org/css-contain/#content-visibility">
<meta name="assert" content="offscreen c-v auto content is relevant when in top layer">

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/common/rendering-utils.js"></script>

<style>
#inner {
    content-visibility: auto;
    contain-intrinsic-size: 100px 100px;
}
</style>

<div popover id="popover">
    <div id="spacer" style="height: 100000px;"></div>
    <div id="inner">
        <div style="height: 200px; width: 200px;">content</div>
    </div>
</div>

<script>
promise_test(async () => {
    popover.showPopover();
    // It takes at least one frame to determine the proximity to the viewport.
    await waitForAtLeastOneFrame();

    // Even though the element with `content-visibility: auto` has an ancestor
    // in the top layer, this element is not in the top layer list (although
    // it's in the top layer stacking context). This means it should not be
    // relevant to the user, because it is not onscreen.
    assert_equals(inner.getBoundingClientRect().height, 100);
});
</script>