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<title>CSS Images Module Level 4: parsing gradients with color interpolation methods</title>
<link rel="author" title="Sam Weinig" href="mailto:weinig@apple.com">
<link rel="help" href="https://drafts.csswg.org/css-images-4/#gradients">
<link rel="help" href="https://drafts.csswg.org/css-color-4/#color-interpolation-method">
<meta name="assert" content="gradients supports the addition of color-interpolation-method to the grammar">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/css/support/parsing-testcommon.js"></script>
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<script>

const LINEAR_GRADIENT_SPECIFIERS = [
    { input: '30deg' },
    { input: 'to right bottom' },
];

const RADIAL_GRADIENT_SPECIFIERS = [
    { input: '50px' },
    { input: 'ellipse 50% 40em', output: '50% 40em' },
    { input: 'at right center' },
];

const CONIC_GRADIENT_SPECIFIERS = [
    { input: 'from 30deg' },
    { input: 'at left 10px top 50em' },
];

const legacy_stops = "red, blue"
const legacy_stops_with_hint = "red, 50%, blue"
const non_legacy_stops = "color(srgb 1 0 0), blue"

function test_gradients_no_specified_interpolation_method(gradientFunction, specifiers, stops)
{
    for (const specifier of specifiers) {
        const input = specifier.input
        const output = specifier.output ? specifier.output : specifier.input
        test_valid_value(`background-image`, `${gradientFunction}(${input}, ${stops})`, `${gradientFunction}(${output}, ${stops})`)
    }
}

function test_gradients(gradientFunction, colorInterpolationMethod, colorInterpolationMethodResult, specifiers, stops) {
    const resultForNoSpecifierCase = (colorInterpolationMethodResult == "") ? "" : `in ${colorInterpolationMethodResult}, `
    test_valid_value(`background-image`, `${gradientFunction}(in ${colorInterpolationMethod}, ${stops})`, `${gradientFunction}(${resultForNoSpecifierCase}${stops})`)

    for (const specifier of specifiers) {
        const input = specifier.input
        const output = specifier.output ? specifier.output : specifier.input
        const result = colorInterpolationMethodResult == "" ? ", " : ` in ${colorInterpolationMethodResult}, `
        test_valid_value(`background-image`, `${gradientFunction}(${input} in ${colorInterpolationMethod}, ${stops})`, `${gradientFunction}(${output}${result}${stops})`)
        test_valid_value(`background-image`, `${gradientFunction}(in ${colorInterpolationMethod} ${input}, ${stops})`, `${gradientFunction}(${output}${result}${stops})`)
    }
}

function test_gradient_with_interpolation_method(gradientFunction, colorInterpolationMethod, colorInterpolationMethodResult, specifiers, stops) {
    const colorInterpolationMethodResultForLegacyStops = (colorInterpolationMethodResult == "srgb") ? "" : colorInterpolationMethodResult;
    test_gradients(gradientFunction, colorInterpolationMethod, colorInterpolationMethodResultForLegacyStops, specifiers, legacy_stops)
    test_gradients(gradientFunction, colorInterpolationMethod, colorInterpolationMethodResultForLegacyStops, specifiers, legacy_stops_with_hint)

    const colorInterpolationMethodResultForNonLegacyStops = (colorInterpolationMethodResult == "oklab") ? "" : colorInterpolationMethodResult;
    test_gradients(gradientFunction, colorInterpolationMethod, colorInterpolationMethodResultForNonLegacyStops, specifiers, non_legacy_stops)
}

function test_each_interpolation_method(gradientFunction, specifiers) {
    test_gradients_no_specified_interpolation_method(gradientFunction, specifiers, legacy_stops)
    test_gradients_no_specified_interpolation_method(gradientFunction, specifiers, legacy_stops_with_hint)
    test_gradients_no_specified_interpolation_method(gradientFunction, specifiers, non_legacy_stops)

    for (const colorSpace of [ "lab", "oklab", "srgb", "srgb-linear", "xyz", "xyz-d50", "xyz-d65" ]) {
        const colorInterpolationMethod = colorSpace
        const colorInterpolationMethodResult = colorSpace == "xyz" ? "xyz-d65" : colorInterpolationMethod

        test_gradient_with_interpolation_method(gradientFunction, colorInterpolationMethod, colorInterpolationMethodResult, specifiers)
    }

    for (const colorSpace of [ "hsl", "hwb", "lch", "oklch" ]) {
        for (const hueInterpolationMethod of [ "", " shorter hue", " longer hue", " increasing hue", " decreasing hue" ]) {
            const colorInterpolationMethod = `${colorSpace}${hueInterpolationMethod}`
            const colorInterpolationMethodResult = hueInterpolationMethod == " shorter hue" ? colorSpace : colorInterpolationMethod

            test_gradient_with_interpolation_method(gradientFunction, colorInterpolationMethod, colorInterpolationMethodResult, specifiers)
        }
    }
}

test_each_interpolation_method("linear-gradient", LINEAR_GRADIENT_SPECIFIERS)
test_each_interpolation_method("radial-gradient", RADIAL_GRADIENT_SPECIFIERS)
test_each_interpolation_method("conic-gradient", CONIC_GRADIENT_SPECIFIERS)

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