<!DOCTYPE html>
<title>CSS Anchor Positioning: Transition to a flipped state</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/#fallback-apply">
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/#typedef-position-try-fallbacks-try-tactic">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
#cb {
display: inline-block;
position: relative;
width: 400px;
height: 250px;
border: 1px solid black;
}
#cb.shrink {
width: 325px;
}
#anchor {
position: absolute;
width: 50px;
height: 50px;
background: coral;
left: 250px;
top: 50px;
anchor-name: --a;
}
#target {
position-anchor: --a;
position: absolute;
left: anchor(right);
top: anchor(top);
width: 50px;
height: 50px;
background: skyblue;
position-try-fallbacks: flip-start;
}
#target.anim {
transition: left 1000s steps(2, start);
}
</style>
<div id=cb>
<div id=anchor></div>
<div id=target></div>
</div>
<script>
function cleanup() {
target.className = '';
cb.className = '';
}
test((t) => {
t.add_cleanup(cleanup);
assert_equals(target.offsetLeft, 300);
cb.classList.add('shrink');
target.classList.add('anim');
assert_equals(target.offsetLeft, 275);
}, 'Transition to a flipped state');
test((t) => {
t.add_cleanup(cleanup);
cb.classList.add('shrink');
assert_equals(target.offsetLeft, 250);
cb.classList.remove('shrink');
target.classList.add('anim');
assert_equals(target.offsetLeft, 275);
}, 'Transition to an unflipped state');
</script>
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