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<!DOCTYPE html>
<title>Tests basic interaction between 'position-fallback-bounds' and scrolling</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/#fallback-bounds">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/test-common.js"></script>
<style>
body {
position: relative;
width: 200vw;
height: 200vh;
}
#bounds {
position: fixed;
inset: 50px;
background: gray;
opacity: 0.1;
z-index: -1;
anchor-name: --bounds;
}
#anchor {
position: absolute;
width: 100px;
height: 100px;
left: 200px;
top: 200px;
background-color: orange;
anchor-name: --a;
}
#target {
position: fixed;
width: 100px;
height: 100px;
background-color: lime;
anchor-default: --a;
position-fallback-bounds: --bounds;
position-fallback: --corners;
}
@position-fallback --corners {
@try {
bottom: anchor(top);
right: anchor(left);
}
@try {
top: anchor(bottom);
right: anchor(left);
}
@try {
bottom: anchor(top);
left: anchor(right);
}
@try {
top: anchor(bottom);
left: anchor(right);
}
}
</style>
<div id="bounds"></div>
<div id="anchor"></div>
<div id="target"></div>
<script>
promise_test(async () => {
await waitUntilNextAnimationFrame();
assert_fallback_position(target, anchor, 'top');
assert_fallback_position(target, anchor, 'left');
}, "Target is at anchor's top-left corner at initial scroll position");
promise_test(async () => {
document.documentElement.scrollTop = 100;
await waitUntilNextAnimationFrame();
assert_fallback_position(target, anchor, 'bottom');
assert_fallback_position(target, anchor, 'left');
}, "Target falls back to anchor's bottom-left corner after anchor is scrolled upwards");
promise_test(async () => {
document.documentElement.scrollLeft = 100;
await waitUntilNextAnimationFrame();
assert_fallback_position(target, anchor, 'bottom');
assert_fallback_position(target, anchor, 'right');
}, "Target falls back to anchor's bottom-right corner after anchor is further scrolled leftwards");
promise_test(async () => {
document.documentElement.scrollTop = 0;
await waitUntilNextAnimationFrame();
assert_fallback_position(target, anchor, 'top');
assert_fallback_position(target, anchor, 'right');
}, "Target falls back to anchor's top-left corner after anchor is scrolled back downwards");
</script>
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