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<!DOCTYPE html>
<title>Tests the CSSOM interfaces of @position-fallback and @try rules</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/#interfaces">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<div id="anchor"></div>
<div id="not-anchor"></div>
<div id="target"></div>
<script>
function createStyle(t, text) {
const style = document.createElement('style');
style.textContent = text;
t.add_cleanup(() => style.remove());
document.head.appendChild(style);
return style;
}
test(t => {
const style = createStyle(
t, '@position-fallback --pf { @try { left: anchor(right); } }');
const positionFallbackRule = style.sheet.cssRules[0];
assert_true(positionFallbackRule instanceof CSSPositionFallbackRule);
assert_equals(positionFallbackRule.name, '--pf');
assert_equals(positionFallbackRule.cssRules.length, 1);
const tryRule = positionFallbackRule.cssRules[0];
assert_true(tryRule instanceof CSSTryRule);
assert_true(tryRule.style instanceof CSSStyleDeclaration);
assert_equals(tryRule.style.length, 1);
assert_equals(tryRule.style.left, 'anchor(right)');
}, 'CSSPositionFallbackRule and CSSTryRule attribute values');
test(t => {
const style = createStyle(t, '@position-fallback --pf {}');
const positionFallbackRule = style.sheet.cssRules[0];
assert_equals(positionFallbackRule.insertRule('@try {}', 0), 0,
'@try rules can be inserted');
assert_throws_dom('HierarchyRequestError',
() => positionFallbackRule.insertRule('#target { color: red; }', 1),
'style rules cannot be inserted');
assert_throws_dom('HierarchyRequestError',
() => positionFallbackRule.insertRule('@keyframes foo {}', 1),
'other at-rules cannot be inserted');
}, 'CSSPositionFallbackRule.insertRule can insert @try rules only');
test(t => {
const style = createStyle(t, `
@position-fallback --pf { @try { top: anchor(top); } }
#anchor, #not-anchor, #target {
position: absolute; width: 100px; height: 100px; left: 0;
}
#anchor { top: 100px; anchor-name: --a; }
#not-anchor { top: 200px; anchor-name: --b; }
#target { position-fallback: --pf; anchor-default: --a; }
`);
const positionFallbackRule = style.sheet.cssRules[0];
const tryRule = positionFallbackRule.cssRules[0];
// Check the initial position fallback result
assert_equals(target.getBoundingClientRect().left, 0);
assert_equals(target.getBoundingClientRect().top, 100);
// `left` is an allowed property in `@try` and should affect position fallback.
tryRule.style.setProperty('left', 'anchor(right)');
assert_equals(target.getBoundingClientRect().left, 100);
assert_equals(target.getBoundingClientRect().top, 100);
// These properties are disallowed in `@try` rule, and hence should not affect
// position fallback.
tryRule.style.setProperty('anchor-default', '--b');
tryRule.style.setProperty('position', 'static');
assert_equals(target.getBoundingClientRect().left, 100);
assert_equals(target.getBoundingClientRect().top, 100);
}, 'CSSTryRule.style.setProperty setting allowed and disallowed properties');
</script>
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