<!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) {
        CSS.registerProperty({
            name: name,
            syntax: '<length>',
            initialValue: '0px',
            inherits: false
        });
    }

    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');
</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);
    }

    #target {
        font-size: 11px;
    }
</style>

<div id=target></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');

</script>