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unit-cycles.html
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<!DOCTYPE html>
<link rel="help" href="https://drafts.css-houdini.org/css-properties-values-api-1/#dependency-cycles-via-relative-units" />
<meta name="assert" content="This test verifies that reference cycles via units are detected" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
function register_length(name, inherits=true) {
CSS.registerProperty({
name: name,
syntax: '<length>',
initialValue: '0px',
inherits: inherits
});
}
register_length('--font-size-em');
register_length('--font-size-rem');
register_length('--font-size-ex');
register_length('--font-size-ch');
register_length('--font-size-px');
register_length('--font-size-em-via-var');
register_length('--font-size-rem-via-var');
register_length('--font-size-ex-via-var');
register_length('--font-size-ch-via-var');
register_length('--font-size-em-inherited', true);
register_length('--font-size-ex-inherited', true);
register_length('--font-size-ch-inherited', true);
</script>
<style>
:root {
--unregistered-em: 10em;
--unregistered-rem: 10rem;
--unregistered-ex: 10ex;
--unregistered-ch: 10ch;
}
:root, #target {
--font-size-em: 2em;
--font-size-rem: 2rem;
--font-size-ex: 2ex;
--font-size-ch: 2ch;
--font-size-px: 42px;
--font-size-em-via-var: var(--unregistered-em);
--font-size-rem-via-var: var(--unregistered-rem);
--font-size-ex-via-var: var(--unregistered-ex);
--font-size-ch-via-var: var(--unregistered-ch);
}
#parent {
--font-size-em-inherited: 4em;
--font-size-ex-inherited: 4ex;
--font-size-ch-inherited: 4ch;
}
#target {
font-size: 11px;
}
</style>
<div id=parent>
<div id=target></div>
</div>
<div id=ref></div>
<script>
// Compute a dimension (e.g. 1em) given a certain fontSize.
function compute_dimension(dimension, fontSize, element = ref) {
try {
element.attributeStyleMap.set('font-size', fontSize);
element.attributeStyleMap.set('margin-bottom', dimension);
return getComputedStyle(element).marginBottom;
} finally {
element.attributeStyleMap.clear();
}
}
function assert_property_equals(name, value, element = target) {
var computedStyle = getComputedStyle(element);
assert_equals(computedStyle.getPropertyValue(name), value);
}
let unsetFontSize = compute_dimension('1em', 'unset');
add_result_callback(function(){
target.attributeStyleMap.clear();
document.documentElement.attributeStyleMap.clear();
});
test(function() {
target.style = 'font-size: var(--font-size-px);';
assert_property_equals('font-size', '42px');
assert_property_equals('--font-size-px', '42px');
}, 'Non-font-dependent variables can be used in font-size');
test(function() {
target.style = 'font-size: var(--font-size-em);';
assert_property_equals('font-size', unsetFontSize);
assert_property_equals('--font-size-em', compute_dimension('2em', 'unset'));
}, 'Lengths with em units may not be referenced from font-size');
test(function() {
target.style = 'font-size: var(--font-size-ex);';
assert_property_equals('font-size', unsetFontSize);
assert_property_equals('--font-size-ex', compute_dimension('2ex', 'unset'));
}, 'Lengths with ex units may not be referenced from font-size');
test(function() {
target.style = 'font-size: var(--font-size-ch);';
assert_property_equals('font-size', unsetFontSize);
assert_property_equals('--font-size-ch', compute_dimension('2ch', 'unset'));
}, 'Lengths with ch units may not be referenced from font-size');
test(function() {
target.style = 'font-size: var(--font-size-rem);';
let expected = compute_dimension('2rem', 'unset', document.documentElement);
assert_property_equals('--font-size-rem', expected);
assert_property_equals('font-size', expected);
}, 'Lengths with rem units may be referenced from font-size on non-root element');
test(function() {
let root = document.documentElement;
let expected1rem = compute_dimension('1rem', 'unset', root);
let expected2rem = compute_dimension('2rem', 'unset', root);
root.style = 'font-size: var(--font-size-rem);';
assert_property_equals('font-size', expected1rem, root);
assert_property_equals('--font-size-rem', expected2rem, root);
}, 'Lengths with rem units may not be referenced from font-size on root element');
test(function() {
target.style = 'font-size: var(--noexist, var(--font-size-em));';
assert_property_equals('font-size', unsetFontSize);
}, 'Fallback may not use font-relative units');
test(function() {
target.style = 'font-size: var(--font-size-em, 42px);';
assert_property_equals('font-size', '42px');
}, 'Fallback triggered when em unit cycle is detected');
test(function() {
target.style = 'font-size: var(--font-size-ex, 42px);';
assert_property_equals('font-size', '42px');
}, 'Fallback triggered when ex unit cycle is detected');
test(function() {
target.style = 'font-size: var(--font-size-ch, 42px);';
assert_property_equals('font-size', '42px');
}, 'Fallback triggered when ch unit cycle is detected');
test(function() {
let root = document.documentElement;
root.style = 'font-size: var(--font-size-rem, 42px);';
assert_property_equals('font-size', '42px', root);
root.style = 'font-size: unset;';
}, 'Fallback triggered when rem unit cycle is detected on root element');
test(function() {
target.style = 'font-size: var(--font-size-em-via-var);';
assert_property_equals('font-size', unsetFontSize);
assert_property_equals('--font-size-em-via-var', compute_dimension('10em', 'unset'));
}, 'Lengths with em units are detected via var references');
test(function() {
target.style = 'font-size: var(--font-size-ex-via-var);';
assert_property_equals('font-size', unsetFontSize);
assert_property_equals('--font-size-ex-via-var', compute_dimension('10ex', 'unset'));
}, 'Lengths with ex units are detected via var references');
test(function() {
target.style = 'font-size: var(--font-size-ch-via-var);';
assert_property_equals('font-size', unsetFontSize);
assert_property_equals('--font-size-ch-via-var', compute_dimension('10ch', 'unset'));
}, 'Lengths with ch units are detected via var references');
test(function() {
let root = document.documentElement;
let expected1rem = compute_dimension('1rem', 'unset', root);
let expected10rem = compute_dimension('10rem', 'unset', root);
root.style = 'font-size: var(--font-size-rem-via-var);';
assert_property_equals('font-size', expected1rem, root);
assert_property_equals('--font-size-rem-via-var', expected10rem, root);
}, 'Lengths with rem units are detected via var references');
test(function() {
let expected4em = compute_dimension('4em', 'unset');
target.style = 'font-size: var(--font-size-em-inherited);';
assert_property_equals('font-size', expected4em);
assert_property_equals('--font-size-em-inherited', expected4em);
}, 'Inherited lengths with em units may be used');
test(function() {
let expected4ex = compute_dimension('4ex', 'unset');
target.style = 'font-size: var(--font-size-ex-inherited);';
assert_property_equals('font-size', expected4ex);
assert_property_equals('--font-size-ex-inherited', expected4ex);
}, 'Inherited lengths with ex units may be used');
test(function() {
let expected4ch = compute_dimension('4ch', 'unset');
target.style = 'font-size: var(--font-size-ch-inherited);';
assert_property_equals('font-size', expected4ch);
assert_property_equals('--font-size-ch-inherited', expected4ch);
}, 'Inherited lengths with ch units may be used');
</script>