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<!DOCTYPE html>
<title>Tests position fallback with initially out-of-viewport anchor in vertial-lr</title>
<link rel="author" href="mailto:xiaochengh@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#scroll">
<link rel="help" href="https://drafts.csswg.org/css-anchor-1/#fallback-apply">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/test-common.js"></script>
<style>
body {
margin: 0;
width: 200vw;
height: 200vh;
}
html {
writing-mode: vertical-lr;
}
#anchor {
anchor-name: --a;
width: 100px;
height: 100px;
margin-block-start: 100vb;
margin-inline-start: 100vi;
background: orange;
}
#anchored {
position: fixed;
width: 100px;
height: 100px;
background: green;
position-anchor: --a;
position-try-options: --pf1, --pf2, --pf3;
inset-block-start: anchor(--a end);
inset-inline-start: anchor(--a end);
}
@position-try --pf1 {
inset: auto;
inset-block-end: anchor(--a start);
inset-inline-start: anchor(--a end);
}
@position-try --pf2 {
inset: auto;
inset-block-start: anchor(--a end);
inset-inline-end: anchor(--a start);
}
@position-try --pf3 {
inset: auto;
inset-block-end: anchor(--a start);
inset-inline-end: anchor(--a start);
}
</style>
<div id="anchor"></div>
<div id="anchored"></div>
<script>
promise_test(async () => {
await waitUntilNextAnimationFrame();
assert_fallback_position(anchored, anchor, 'top');
assert_fallback_position(anchored, anchor, 'left');
}, 'Should use the last fallback position initially');
promise_test(async () => {
// Scroll left to have enough space right to the anchor, but not enough below.
document.documentElement.scrollLeft = 250;
document.documentElement.scrollTop = 150;
await waitUntilNextAnimationFrame();
assert_fallback_position(anchored, anchor, 'right');
assert_fallback_position(anchored, anchor, 'top');
}, 'Should use the third fallback position with enough space right');
promise_test(async () => {
// Scroll down to have enough space below the anchor, but not enough right.
document.documentElement.scrollLeft = 150;
document.documentElement.scrollTop = 250;
await waitUntilNextAnimationFrame();
assert_fallback_position(anchored, anchor, 'left');
assert_fallback_position(anchored, anchor, 'bottom');
}, 'Should use the second fallback position with enough space below');
promise_test(async () => {
// Scroll down and right to have enough space on both axes.
document.documentElement.scrollLeft = 250;
document.documentElement.scrollTop = 250;
await waitUntilNextAnimationFrame();
assert_fallback_position(anchored, anchor, 'right');
assert_fallback_position(anchored, anchor, 'bottom');
}, 'Should use the first fallback position with enough space right and below');
</script>
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