Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

109 files changed, 37545 insertions, 0 deletions

diff --git a/servo/components/style/values/animated/color.rs b/servo/components/style/values/animated/color.rs
new file mode 100644
index 0000000000..ac3a2ad2d3
--- /dev/null
+++ b/servo/components/style/values/animated/color.rs
@@ -0,0 +1,841 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Animated types for CSS colors.
+
+use crate::values::animated::{Animate, Procedure, ToAnimatedZero};
+use crate::values::computed::Percentage;
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::color::{
+    ColorInterpolationMethod, ColorSpace, GenericColor, GenericColorMix, HueInterpolationMethod,
+};
+use euclid::default::{Transform3D, Vector3D};
+use std::f32::consts::PI;
+
+/// An animated RGBA color.
+///
+/// Unlike in computed values, each component value may exceed the
+/// range `[0.0, 1.0]`.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToAnimatedZero, ToAnimatedValue)]
+#[repr(C)]
+pub struct AnimatedRGBA {
+    /// The red component.
+    pub red: f32,
+    /// The green component.
+    pub green: f32,
+    /// The blue component.
+    pub blue: f32,
+    /// The alpha component.
+    pub alpha: f32,
+}
+
+use self::AnimatedRGBA as RGBA;
+
+const RAD_PER_DEG: f32 = PI / 180.0;
+const DEG_PER_RAD: f32 = 180.0 / PI;
+
+impl RGBA {
+    /// Returns a transparent color.
+    #[inline]
+    pub fn transparent() -> Self {
+        Self::new(0., 0., 0., 0.)
+    }
+
+    /// Returns a new color.
+    #[inline]
+    pub fn new(red: f32, green: f32, blue: f32, alpha: f32) -> Self {
+        RGBA {
+            red,
+            green,
+            blue,
+            alpha,
+        }
+    }
+}
+
+impl Animate for RGBA {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let (left_weight, right_weight) = procedure.weights();
+        Ok(Color::mix(
+            &ColorInterpolationMethod::srgb(),
+            self,
+            left_weight as f32,
+            other,
+            right_weight as f32,
+            /* normalize_weights = */ false,
+        ))
+    }
+}
+
+impl ComputeSquaredDistance for RGBA {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let start = [
+            self.alpha,
+            self.red * self.alpha,
+            self.green * self.alpha,
+            self.blue * self.alpha,
+        ];
+        let end = [
+            other.alpha,
+            other.red * other.alpha,
+            other.green * other.alpha,
+            other.blue * other.alpha,
+        ];
+        start
+            .iter()
+            .zip(&end)
+            .map(|(this, other)| this.compute_squared_distance(other))
+            .sum()
+    }
+}
+
+/// An animated value for `<color>`.
+pub type Color = GenericColor<RGBA, Percentage>;
+
+/// An animated value for `<color-mix>`.
+pub type ColorMix = GenericColorMix<Color, Percentage>;
+
+impl Color {
+    fn to_rgba(&self, current_color: RGBA) -> RGBA {
+        let mut clone = self.clone();
+        clone.simplify(Some(&current_color));
+        *clone.as_numeric().unwrap()
+    }
+
+    /// Mix two colors into one.
+    pub fn mix(
+        interpolation: &ColorInterpolationMethod,
+        left_color: &RGBA,
+        mut left_weight: f32,
+        right_color: &RGBA,
+        mut right_weight: f32,
+        normalize_weights: bool,
+    ) -> RGBA {
+        // https://drafts.csswg.org/css-color-5/#color-mix-percent-norm
+        let mut alpha_multiplier = 1.0;
+        if normalize_weights {
+            let sum = left_weight + right_weight;
+            if sum != 1.0 {
+                let scale = 1.0 / sum;
+                left_weight *= scale;
+                right_weight *= scale;
+                if sum < 1.0 {
+                    alpha_multiplier = sum;
+                }
+            }
+        }
+
+        let mix_function = match interpolation.space {
+            ColorSpace::Srgb => Self::mix_in::<RGBA>,
+            ColorSpace::LinearSrgb => Self::mix_in::<LinearRGBA>,
+            ColorSpace::Xyz => Self::mix_in::<XYZD65A>,
+            ColorSpace::XyzD50 => Self::mix_in::<XYZD50A>,
+            ColorSpace::Lab => Self::mix_in::<LABA>,
+            ColorSpace::Hwb => Self::mix_in::<HWBA>,
+            ColorSpace::Hsl => Self::mix_in::<HSLA>,
+            ColorSpace::Lch => Self::mix_in::<LCHA>,
+        };
+        mix_function(
+            left_color,
+            left_weight,
+            right_color,
+            right_weight,
+            interpolation.hue,
+            alpha_multiplier,
+        )
+    }
+
+    fn mix_in<S>(
+        left_color: &RGBA,
+        left_weight: f32,
+        right_color: &RGBA,
+        right_weight: f32,
+        hue_interpolation: HueInterpolationMethod,
+        alpha_multiplier: f32,
+    ) -> RGBA
+    where
+        S: ModelledColor,
+    {
+        let left = S::from(*left_color);
+        let right = S::from(*right_color);
+
+        let color = S::lerp(&left, left_weight, &right, right_weight, hue_interpolation);
+        let mut rgba = RGBA::from(color.into());
+        if alpha_multiplier != 1.0 {
+            rgba.alpha *= alpha_multiplier;
+        }
+
+        rgba
+    }
+}
+
+impl Animate for Color {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let (left_weight, right_weight) = procedure.weights();
+        let mut color = Color::ColorMix(Box::new(ColorMix {
+            interpolation: ColorInterpolationMethod::srgb(),
+            left: self.clone(),
+            left_percentage: Percentage(left_weight as f32),
+            right: other.clone(),
+            right_percentage: Percentage(right_weight as f32),
+            // See https://github.com/w3c/csswg-drafts/issues/7324
+            normalize_weights: false,
+        }));
+        color.simplify(None);
+        Ok(color)
+    }
+}
+
+impl ComputeSquaredDistance for Color {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let current_color = RGBA::transparent();
+        self.to_rgba(current_color)
+            .compute_squared_distance(&other.to_rgba(current_color))
+    }
+}
+
+impl ToAnimatedZero for Color {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(Color::rgba(RGBA::transparent()))
+    }
+}
+
+/// A color modelled in a specific color space (such as sRGB or CIE XYZ).
+///
+/// For now, colors modelled in other spaces need to be convertible to and from
+/// `RGBA` because we use sRGB for displaying colors.
+trait ModelledColor: Clone + Copy + From<RGBA> + Into<RGBA> {
+    /// Linearly interpolate between the left and right colors.
+    ///
+    /// The HueInterpolationMethod parameter is only for color spaces where the hue is
+    /// represented as an angle (e.g., CIE LCH).
+    fn lerp(
+        left_bg: &Self,
+        left_weight: f32,
+        right_bg: &Self,
+        right_weight: f32,
+        hue_interpolation: HueInterpolationMethod,
+    ) -> Self;
+}
+
+fn interpolate_premultiplied_component(
+    left: f32,
+    left_weight: f32,
+    left_alpha: f32,
+    right: f32,
+    right_weight: f32,
+    right_alpha: f32,
+    inverse_of_result_alpha: f32,
+) -> f32 {
+    (left * left_weight * left_alpha + right * right_weight * right_alpha) * inverse_of_result_alpha
+}
+
+// Normalize hue into [0, 360)
+fn normalize_hue(v: f32) -> f32 {
+    v - 360. * (v / 360.).floor()
+}
+
+fn adjust_hue(left: &mut f32, right: &mut f32, hue_interpolation: HueInterpolationMethod) {
+    // Adjust the hue angle as per
+    // https://drafts.csswg.org/css-color/#hue-interpolation.
+    //
+    // If both hue angles are NAN, they should be set to 0. Otherwise, if a
+    // single hue angle is NAN, it should use the other hue angle.
+    if left.is_nan() {
+        if right.is_nan() {
+            *left = 0.;
+            *right = 0.;
+        } else {
+            *left = *right;
+        }
+    } else if right.is_nan() {
+        *right = *left;
+    }
+
+    if hue_interpolation == HueInterpolationMethod::Specified {
+        // Angles are not adjusted. They are interpolated like any other
+        // component.
+        return;
+    }
+
+    *left = normalize_hue(*left);
+    *right = normalize_hue(*right);
+
+    match hue_interpolation {
+        // https://drafts.csswg.org/css-color/#shorter
+        HueInterpolationMethod::Shorter => {
+            let delta = *right - *left;
+
+            if delta > 180. {
+                *left += 360.;
+            } else if delta < -180. {
+                *right += 360.;
+            }
+        },
+        // https://drafts.csswg.org/css-color/#longer
+        HueInterpolationMethod::Longer => {
+            let delta = *right - *left;
+            if 0. < delta && delta < 180. {
+                *left += 360.;
+            } else if -180. < delta && delta < 0. {
+                *right += 360.;
+            }
+        },
+        // https://drafts.csswg.org/css-color/#increasing
+        HueInterpolationMethod::Increasing => {
+            if *right < *left {
+                *right += 360.;
+            }
+        },
+        // https://drafts.csswg.org/css-color/#decreasing
+        HueInterpolationMethod::Decreasing => {
+            if *left < *right {
+                *left += 360.;
+            }
+        },
+        HueInterpolationMethod::Specified => unreachable!("Handled above"),
+    }
+}
+
+fn interpolate_hue(
+    mut left: f32,
+    left_weight: f32,
+    mut right: f32,
+    right_weight: f32,
+    hue_interpolation: HueInterpolationMethod,
+) -> f32 {
+    adjust_hue(&mut left, &mut right, hue_interpolation);
+    left * left_weight + right * right_weight
+}
+
+fn interpolate_premultiplied(
+    left: &[f32; 4],
+    left_weight: f32,
+    right: &[f32; 4],
+    right_weight: f32,
+    hue_index: Option<usize>,
+    hue_interpolation: HueInterpolationMethod,
+) -> [f32; 4] {
+    let left_alpha = left[3];
+    let right_alpha = right[3];
+    let result_alpha = (left_alpha * left_weight + right_alpha * right_weight).min(1.);
+    let mut result = [0.; 4];
+    if result_alpha <= 0. {
+        return result;
+    }
+
+    let inverse_of_result_alpha = 1. / result_alpha;
+    for i in 0..3 {
+        let is_hue = hue_index == Some(i);
+        result[i] = if is_hue {
+            interpolate_hue(
+                left[i],
+                left_weight,
+                right[i],
+                right_weight,
+                hue_interpolation,
+            )
+        } else {
+            interpolate_premultiplied_component(
+                left[i],
+                left_weight,
+                left_alpha,
+                right[i],
+                right_weight,
+                right_alpha,
+                inverse_of_result_alpha,
+            )
+        };
+    }
+    result[3] = result_alpha;
+
+    result
+}
+
+macro_rules! impl_lerp {
+    ($ty:ident, $hue_index:expr) => {
+        // These ensure the transmutes below are sound.
+        const_assert_eq!(std::mem::size_of::<$ty>(), std::mem::size_of::<f32>() * 4);
+        const_assert_eq!(std::mem::align_of::<$ty>(), std::mem::align_of::<f32>());
+        impl ModelledColor for $ty {
+            fn lerp(
+                left: &Self,
+                left_weight: f32,
+                right: &Self,
+                right_weight: f32,
+                hue_interpolation: HueInterpolationMethod,
+            ) -> Self {
+                use std::mem::transmute;
+                unsafe {
+                    transmute::<[f32; 4], Self>(interpolate_premultiplied(
+                        transmute::<&Self, &[f32; 4]>(left),
+                        left_weight,
+                        transmute::<&Self, &[f32; 4]>(right),
+                        right_weight,
+                        $hue_index,
+                        hue_interpolation,
+                    ))
+                }
+            }
+        }
+    };
+}
+
+impl_lerp!(RGBA, None);
+
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct LinearRGBA {
+    red: f32,
+    green: f32,
+    blue: f32,
+    alpha: f32,
+}
+
+impl_lerp!(LinearRGBA, None);
+
+/// An animated XYZ D65 colour.
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct XYZD65A {
+    x: f32,
+    y: f32,
+    z: f32,
+    alpha: f32,
+}
+
+impl_lerp!(XYZD65A, None);
+
+/// An animated XYZ D50 colour.
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct XYZD50A {
+    x: f32,
+    y: f32,
+    z: f32,
+    alpha: f32,
+}
+
+impl_lerp!(XYZD50A, None);
+
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct LABA {
+    lightness: f32,
+    a: f32,
+    b: f32,
+    alpha: f32,
+}
+
+impl_lerp!(LABA, None);
+
+/// An animated LCHA colour.
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct LCHA {
+    lightness: f32,
+    chroma: f32,
+    hue: f32,
+    alpha: f32,
+}
+
+impl_lerp!(LCHA, Some(2));
+
+/// An animated hwb() color.
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct HWBA {
+    hue: f32,
+    white: f32,
+    black: f32,
+    alpha: f32,
+}
+
+impl_lerp!(HWBA, Some(0));
+
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+struct HSLA {
+    hue: f32,
+    sat: f32,
+    light: f32,
+    alpha: f32,
+}
+
+impl_lerp!(HSLA, Some(0));
+
+// https://drafts.csswg.org/css-color/#rgb-to-hsl
+//
+// We also return min/max for the hwb conversion.
+fn rgb_to_hsl(rgba: RGBA) -> (HSLA, f32, f32) {
+    let RGBA {
+        red,
+        green,
+        blue,
+        alpha,
+    } = rgba;
+    let max = red.max(green).max(blue);
+    let min = red.min(green).min(blue);
+    let mut hue = std::f32::NAN;
+    let mut sat = 0.;
+    let light = (min + max) / 2.;
+    let d = max - min;
+
+    if d != 0. {
+        sat = if light == 0.0 || light == 1.0 {
+            0.
+        } else {
+            (max - light) / light.min(1. - light)
+        };
+
+        if max == red {
+            hue = (green - blue) / d + if green < blue { 6. } else { 0. }
+        } else if max == green {
+            hue = (blue - red) / d + 2.;
+        } else {
+            hue = (red - green) / d + 4.;
+        }
+
+        hue *= 60.;
+    }
+
+    (
+        HSLA {
+            hue,
+            sat,
+            light,
+            alpha,
+        },
+        min,
+        max,
+    )
+}
+
+impl From<RGBA> for HSLA {
+    fn from(rgba: RGBA) -> Self {
+        rgb_to_hsl(rgba).0
+    }
+}
+
+impl From<HSLA> for RGBA {
+    fn from(hsla: HSLA) -> Self {
+        // cssparser expects hue in the 0..1 range.
+        let hue_normalized = normalize_hue(hsla.hue) / 360.;
+        let (r, g, b) = cssparser::hsl_to_rgb(hue_normalized, hsla.sat, hsla.light);
+        RGBA::new(r, g, b, hsla.alpha)
+    }
+}
+
+impl From<RGBA> for HWBA {
+    // https://drafts.csswg.org/css-color/#rgb-to-hwb
+    fn from(rgba: RGBA) -> Self {
+        let (hsl, min, max) = rgb_to_hsl(rgba);
+        Self {
+            hue: hsl.hue,
+            white: min,
+            black: 1. - max,
+            alpha: rgba.alpha,
+        }
+    }
+}
+
+impl From<HWBA> for RGBA {
+    fn from(hwba: HWBA) -> Self {
+        let hue_normalized = normalize_hue(hwba.hue) / 360.;
+        let (r, g, b) = cssparser::hwb_to_rgb(hue_normalized, hwba.white, hwba.black);
+        RGBA::new(r, g, b, hwba.alpha)
+    }
+}
+
+impl From<RGBA> for LinearRGBA {
+    fn from(rgba: RGBA) -> Self {
+        fn linearize(value: f32) -> f32 {
+            let sign = if value < 0. { -1. } else { 1. };
+            let abs = value.abs();
+            if abs < 0.04045 {
+                return value / 12.92;
+            }
+
+            sign * ((abs + 0.055) / 1.055).powf(2.4)
+        }
+        Self {
+            red: linearize(rgba.red),
+            green: linearize(rgba.green),
+            blue: linearize(rgba.blue),
+            alpha: rgba.alpha,
+        }
+    }
+}
+
+impl From<LinearRGBA> for RGBA {
+    fn from(lrgba: LinearRGBA) -> Self {
+        fn delinearize(value: f32) -> f32 {
+            let sign = if value < 0. { -1. } else { 1. };
+            let abs = value.abs();
+
+            if abs > 0.0031308 {
+                sign * (1.055 * abs.powf(1. / 2.4) - 0.055)
+            } else {
+                12.92 * value
+            }
+        }
+        Self {
+            red: delinearize(lrgba.red),
+            green: delinearize(lrgba.green),
+            blue: delinearize(lrgba.blue),
+            alpha: lrgba.alpha,
+        }
+    }
+}
+
+impl From<XYZD65A> for XYZD50A {
+    fn from(d65: XYZD65A) -> Self {
+        // https://drafts.csswg.org/css-color-4/#color-conversion-code
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const BRADFORD: Transform3D<f32> = Transform3D::new(
+             1.0479298208405488,    0.029627815688159344, -0.009243058152591178,  0.,
+             0.022946793341019088,  0.990434484573249,     0.015055144896577895,  0.,
+            -0.05019222954313557,  -0.01707382502938514,   0.7518742899580008,    0.,
+             0.,                    0.,                    0.,                    1.,
+        );
+        let d50 = BRADFORD.transform_vector3d(Vector3D::new(d65.x, d65.y, d65.z));
+        Self {
+            x: d50.x,
+            y: d50.y,
+            z: d50.z,
+            alpha: d65.alpha,
+        }
+    }
+}
+
+impl From<XYZD50A> for XYZD65A {
+    fn from(d50: XYZD50A) -> Self {
+        // https://drafts.csswg.org/css-color-4/#color-conversion-code
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const BRADFORD_INVERSE: Transform3D<f32> = Transform3D::new(
+            0.9554734527042182,   -0.028369706963208136,  0.012314001688319899,  0.,
+           -0.023098536874261423,  1.0099954580058226,   -0.020507696433477912,  0.,
+            0.0632593086610217,    0.021041398966943008,  1.3303659366080753,    0.,
+            0.,                    0.,                    0.,                    1.,
+        );
+        let d65 = BRADFORD_INVERSE.transform_vector3d(Vector3D::new(d50.x, d50.y, d50.z));
+        Self {
+            x: d65.x,
+            y: d65.y,
+            z: d65.z,
+            alpha: d50.alpha,
+        }
+    }
+}
+
+impl From<LinearRGBA> for XYZD65A {
+    fn from(lrgba: LinearRGBA) -> Self {
+        // https://drafts.csswg.org/css-color-4/#color-conversion-code
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const LSRGB_TO_XYZ: Transform3D<f32> = Transform3D::new(
+            0.41239079926595934,  0.21263900587151027,  0.01933081871559182,  0.,
+            0.357584339383878,    0.715168678767756,    0.11919477979462598,  0.,
+            0.1804807884018343,   0.07219231536073371,  0.9505321522496607,   0.,
+            0.,                   0.,                   0.,                   1.,
+        );
+        let linear_rgb = Vector3D::new(lrgba.red, lrgba.green, lrgba.blue);
+        let xyz = LSRGB_TO_XYZ.transform_vector3d(linear_rgb);
+        Self {
+            x: xyz.x,
+            y: xyz.y,
+            z: xyz.z,
+            alpha: lrgba.alpha,
+        }
+    }
+}
+
+impl From<XYZD65A> for LinearRGBA {
+    fn from(d65: XYZD65A) -> Self {
+        // https://drafts.csswg.org/css-color-4/#color-conversion-code
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        const XYZ_TO_LSRGB: Transform3D<f32> = Transform3D::new(
+             3.2409699419045226,  -0.9692436362808796,   0.05563007969699366,  0.,
+            -1.537383177570094,    1.8759675015077202,  -0.20397695888897652,  0.,
+            -0.4986107602930034,   0.04155505740717559,  1.0569715142428786,   0.,
+             0.,                   0.,                   0.,                   1.,
+        );
+
+        let xyz = Vector3D::new(d65.x, d65.y, d65.z);
+        let rgb = XYZ_TO_LSRGB.transform_vector3d(xyz);
+        Self {
+            red: rgb.x,
+            green: rgb.y,
+            blue: rgb.z,
+            alpha: d65.alpha,
+        }
+    }
+}
+
+impl From<XYZD65A> for RGBA {
+    fn from(d65: XYZD65A) -> Self {
+        Self::from(LinearRGBA::from(d65))
+    }
+}
+
+impl From<RGBA> for XYZD65A {
+    /// Convert an RGBA colour to XYZ as specified in [1].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#rgb-to-lab
+    fn from(rgba: RGBA) -> Self {
+        Self::from(LinearRGBA::from(rgba))
+    }
+}
+
+impl From<XYZD50A> for LABA {
+    /// Convert an XYZ colour to LAB as specified in [1] and [2].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#rgb-to-lab
+    /// [2]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(xyza: XYZD50A) -> Self {
+        const WHITE: [f32; 3] = [0.96422, 1., 0.82521];
+
+        fn compute_f(value: f32) -> f32 {
+            const EPSILON: f32 = 216. / 24389.;
+            const KAPPA: f32 = 24389. / 27.;
+
+            if value > EPSILON {
+                value.cbrt()
+            } else {
+                (KAPPA * value + 16.) / 116.
+            }
+        }
+
+        // 4. Convert D50-adapted XYZ to Lab.
+        let f = [
+            compute_f(xyza.x / WHITE[0]),
+            compute_f(xyza.y / WHITE[1]),
+            compute_f(xyza.z / WHITE[2]),
+        ];
+
+        let lightness = 116. * f[1] - 16.;
+        let a = 500. * (f[0] - f[1]);
+        let b = 200. * (f[1] - f[2]);
+
+        LABA {
+            lightness,
+            a,
+            b,
+            alpha: xyza.alpha,
+        }
+    }
+}
+
+impl From<LABA> for LCHA {
+    /// Convert a LAB color to LCH as specified in [1].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(laba: LABA) -> Self {
+        let hue = laba.b.atan2(laba.a) * DEG_PER_RAD;
+        let chroma = (laba.a * laba.a + laba.b * laba.b).sqrt();
+        LCHA {
+            lightness: laba.lightness,
+            chroma,
+            hue,
+            alpha: laba.alpha,
+        }
+    }
+}
+
+impl From<LCHA> for LABA {
+    /// Convert a LCH color to LAB as specified in [1].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(lcha: LCHA) -> Self {
+        let hue_radians = lcha.hue * RAD_PER_DEG;
+        let a = lcha.chroma * hue_radians.cos();
+        let b = lcha.chroma * hue_radians.sin();
+        LABA {
+            lightness: lcha.lightness,
+            a,
+            b,
+            alpha: lcha.alpha,
+        }
+    }
+}
+
+impl From<LABA> for XYZD50A {
+    /// Convert a CIELAB color to XYZ as specified in [1] and [2].
+    ///
+    /// [1]: https://drafts.csswg.org/css-color/#lab-to-predefined
+    /// [2]: https://drafts.csswg.org/css-color/#color-conversion-code
+    fn from(laba: LABA) -> Self {
+        // 1. Convert LAB to (D50-adapated) XYZ.
+        const KAPPA: f32 = 24389. / 27.;
+        const EPSILON: f32 = 216. / 24389.;
+        const WHITE: [f32; 3] = [0.96422, 1., 0.82521];
+
+        let f1 = (laba.lightness + 16f32) / 116f32;
+        let f0 = (laba.a / 500.) + f1;
+        let f2 = f1 - laba.b / 200.;
+
+        let x = if f0.powf(3.) > EPSILON {
+            f0.powf(3.)
+        } else {
+            (116. * f0 - 16.) / KAPPA
+        };
+        let y = if laba.lightness > KAPPA * EPSILON {
+            ((laba.lightness + 16.) / 116.).powf(3.)
+        } else {
+            laba.lightness / KAPPA
+        };
+        let z = if f2.powf(3.) > EPSILON {
+            f2.powf(3.)
+        } else {
+            (116. * f2 - 16.) / KAPPA
+        };
+
+        Self {
+            x: x * WHITE[0],
+            y: y * WHITE[1],
+            z: z * WHITE[2],
+            alpha: laba.alpha,
+        }
+    }
+}
+
+impl From<XYZD50A> for RGBA {
+    fn from(d50: XYZD50A) -> Self {
+        Self::from(XYZD65A::from(d50))
+    }
+}
+
+impl From<RGBA> for XYZD50A {
+    fn from(rgba: RGBA) -> Self {
+        Self::from(XYZD65A::from(rgba))
+    }
+}
+
+impl From<RGBA> for LABA {
+    fn from(rgba: RGBA) -> Self {
+        Self::from(XYZD50A::from(rgba))
+    }
+}
+
+impl From<LABA> for RGBA {
+    fn from(laba: LABA) -> Self {
+        Self::from(XYZD50A::from(laba))
+    }
+}
+
+impl From<RGBA> for LCHA {
+    fn from(rgba: RGBA) -> Self {
+        Self::from(LABA::from(rgba))
+    }
+}
+
+impl From<LCHA> for RGBA {
+    fn from(lcha: LCHA) -> Self {
+        Self::from(LABA::from(lcha))
+    }
+}
diff --git a/servo/components/style/values/animated/effects.rs b/servo/components/style/values/animated/effects.rs
new file mode 100644
index 0000000000..67557e54b7
--- /dev/null
+++ b/servo/components/style/values/animated/effects.rs
@@ -0,0 +1,27 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Animated types for CSS values related to effects.
+
+use crate::values::animated::color::Color;
+use crate::values::computed::length::Length;
+#[cfg(feature = "gecko")]
+use crate::values::computed::url::ComputedUrl;
+use crate::values::computed::{Angle, Number};
+use crate::values::generics::effects::Filter as GenericFilter;
+use crate::values::generics::effects::SimpleShadow as GenericSimpleShadow;
+#[cfg(not(feature = "gecko"))]
+use crate::values::Impossible;
+
+/// An animated value for the `drop-shadow()` filter.
+pub type AnimatedSimpleShadow = GenericSimpleShadow<Color, Length, Length>;
+
+/// An animated value for a single `filter`.
+#[cfg(feature = "gecko")]
+pub type AnimatedFilter =
+    GenericFilter<Angle, Number, Number, Length, AnimatedSimpleShadow, ComputedUrl>;
+
+/// An animated value for a single `filter`.
+#[cfg(not(feature = "gecko"))]
+pub type AnimatedFilter = GenericFilter<Angle, Number, Number, Length, Impossible, Impossible>;
diff --git a/servo/components/style/values/animated/font.rs b/servo/components/style/values/animated/font.rs
new file mode 100644
index 0000000000..f890a3b2bd
--- /dev/null
+++ b/servo/components/style/values/animated/font.rs
@@ -0,0 +1,151 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Animation implementation for various font-related types.
+
+use super::{Animate, Procedure, ToAnimatedZero};
+use crate::values::computed::font::FontVariationSettings;
+use crate::values::computed::Number;
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::font::{FontSettings as GenericFontSettings, FontTag, VariationValue};
+
+/// <https://drafts.csswg.org/css-fonts-4/#font-variation-settings-def>
+impl Animate for FontVariationSettings {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        FontSettingTagIter::new(self, other)?
+            .map(|r| r.and_then(|(st, ot)| st.animate(&ot, procedure)))
+            .collect::<Result<Vec<ComputedVariationValue>, ()>>()
+            .map(|v| GenericFontSettings(v.into_boxed_slice()))
+    }
+}
+
+impl ComputeSquaredDistance for FontVariationSettings {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        FontSettingTagIter::new(self, other)?
+            .map(|r| r.and_then(|(st, ot)| st.compute_squared_distance(&ot)))
+            .sum()
+    }
+}
+
+impl ToAnimatedZero for FontVariationSettings {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+type ComputedVariationValue = VariationValue<Number>;
+
+// FIXME: Could do a rename, this is only used for font variations.
+struct FontSettingTagIterState<'a> {
+    tags: Vec<&'a ComputedVariationValue>,
+    index: usize,
+    prev_tag: FontTag,
+}
+
+impl<'a> FontSettingTagIterState<'a> {
+    fn new(tags: Vec<&'a ComputedVariationValue>) -> FontSettingTagIterState<'a> {
+        FontSettingTagIterState {
+            index: tags.len(),
+            tags,
+            prev_tag: FontTag(0),
+        }
+    }
+}
+
+/// Iterator for font-variation-settings tag lists
+///
+/// [CSS fonts level 4](https://drafts.csswg.org/css-fonts-4/#descdef-font-face-font-variation-settings)
+/// defines the animation of font-variation-settings as follows:
+///
+///   Two declarations of font-feature-settings[sic] can be animated between if
+///   they are "like".  "Like" declarations are ones where the same set of
+///   properties appear (in any order).  Because succesive[sic] duplicate
+///   properties are applied instead of prior duplicate properties, two
+///   declarations can be "like" even if they have differing number of
+///   properties. If two declarations are "like" then animation occurs pairwise
+///   between corresponding values in the declarations.
+///
+/// In other words if we have the following lists:
+///
+///   "wght" 1.4, "wdth" 5, "wght" 2
+///   "wdth" 8, "wght" 4, "wdth" 10
+///
+/// We should animate between:
+///
+///   "wdth" 5, "wght" 2
+///   "wght" 4, "wdth" 10
+///
+/// This iterator supports this by sorting the two lists, then iterating them in
+/// reverse, and skipping entries with repeated tag names. It will return
+/// Some(Err()) if it reaches the end of one list before the other, or if the
+/// tag names do not match.
+///
+/// For the above example, this iterator would return:
+///
+///   Some(Ok("wght" 2, "wght" 4))
+///   Some(Ok("wdth" 5, "wdth" 10))
+///   None
+///
+struct FontSettingTagIter<'a> {
+    a_state: FontSettingTagIterState<'a>,
+    b_state: FontSettingTagIterState<'a>,
+}
+
+impl<'a> FontSettingTagIter<'a> {
+    fn new(
+        a_settings: &'a FontVariationSettings,
+        b_settings: &'a FontVariationSettings,
+    ) -> Result<FontSettingTagIter<'a>, ()> {
+        if a_settings.0.is_empty() || b_settings.0.is_empty() {
+            return Err(());
+        }
+
+        fn as_new_sorted_tags(tags: &[ComputedVariationValue]) -> Vec<&ComputedVariationValue> {
+            use std::iter::FromIterator;
+            let mut sorted_tags = Vec::from_iter(tags.iter());
+            sorted_tags.sort_by_key(|k| k.tag.0);
+            sorted_tags
+        }
+
+        Ok(FontSettingTagIter {
+            a_state: FontSettingTagIterState::new(as_new_sorted_tags(&a_settings.0)),
+            b_state: FontSettingTagIterState::new(as_new_sorted_tags(&b_settings.0)),
+        })
+    }
+
+    fn next_tag(state: &mut FontSettingTagIterState<'a>) -> Option<&'a ComputedVariationValue> {
+        if state.index == 0 {
+            return None;
+        }
+
+        state.index -= 1;
+        let tag = state.tags[state.index];
+        if tag.tag == state.prev_tag {
+            FontSettingTagIter::next_tag(state)
+        } else {
+            state.prev_tag = tag.tag;
+            Some(tag)
+        }
+    }
+}
+
+impl<'a> Iterator for FontSettingTagIter<'a> {
+    type Item = Result<(&'a ComputedVariationValue, &'a ComputedVariationValue), ()>;
+
+    fn next(
+        &mut self,
+    ) -> Option<Result<(&'a ComputedVariationValue, &'a ComputedVariationValue), ()>> {
+        match (
+            FontSettingTagIter::next_tag(&mut self.a_state),
+            FontSettingTagIter::next_tag(&mut self.b_state),
+        ) {
+            (Some(at), Some(bt)) if at.tag == bt.tag => Some(Ok((at, bt))),
+            (None, None) => None,
+            _ => Some(Err(())), // Mismatch number of unique tags or tag names.
+        }
+    }
+}
diff --git a/servo/components/style/values/animated/grid.rs b/servo/components/style/values/animated/grid.rs
new file mode 100644
index 0000000000..7b9417a08c
--- /dev/null
+++ b/servo/components/style/values/animated/grid.rs
@@ -0,0 +1,166 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Animation implementation for various grid-related types.
+
+// Note: we can implement Animate on their generic types directly, but in this case we need to
+// make sure two trait bounds, L: Clone and I: PartialEq, are satisfied on almost all the
+// grid-related types and their other trait implementations because Animate needs them. So in
+// order to avoid adding these two trait bounds (or maybe more..) everywhere, we implement
+// Animate for the computed types, instead of the generic types.
+
+use super::{Animate, Procedure, ToAnimatedZero};
+use crate::values::computed::Integer;
+use crate::values::computed::LengthPercentage;
+use crate::values::computed::{GridTemplateComponent, TrackList, TrackSize};
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::grid as generics;
+
+fn discrete<T: Clone>(from: &T, to: &T, procedure: Procedure) -> Result<T, ()> {
+    if let Procedure::Interpolate { progress } = procedure {
+        Ok(if progress < 0.5 {
+            from.clone()
+        } else {
+            to.clone()
+        })
+    } else {
+        Err(())
+    }
+}
+
+fn animate_with_discrete_fallback<T: Animate + Clone>(
+    from: &T,
+    to: &T,
+    procedure: Procedure,
+) -> Result<T, ()> {
+    from.animate(to, procedure)
+        .or_else(|_| discrete(from, to, procedure))
+}
+
+impl Animate for TrackSize {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        match (self, other) {
+            (&generics::TrackSize::Breadth(ref from), &generics::TrackSize::Breadth(ref to)) => {
+                animate_with_discrete_fallback(from, to, procedure)
+                    .map(generics::TrackSize::Breadth)
+            },
+            (
+                &generics::TrackSize::Minmax(ref from_min, ref from_max),
+                &generics::TrackSize::Minmax(ref to_min, ref to_max),
+            ) => Ok(generics::TrackSize::Minmax(
+                animate_with_discrete_fallback(from_min, to_min, procedure)?,
+                animate_with_discrete_fallback(from_max, to_max, procedure)?,
+            )),
+            (
+                &generics::TrackSize::FitContent(ref from),
+                &generics::TrackSize::FitContent(ref to),
+            ) => animate_with_discrete_fallback(from, to, procedure)
+                .map(generics::TrackSize::FitContent),
+            (_, _) => discrete(self, other, procedure),
+        }
+    }
+}
+
+impl Animate for generics::TrackRepeat<LengthPercentage, Integer> {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        // If the keyword, auto-fit/fill, is the same it can result in different
+        // number of tracks. For both auto-fit/fill, the number of columns isn't
+        // known until you do layout since it depends on the container size, item
+        // placement and other factors, so we cannot do the correct interpolation
+        // by computed values. Therefore, return Err(()) if it's keywords. If it
+        // is Number, we support animation only if the count is the same and the
+        // length of track_sizes is the same.
+        // https://github.com/w3c/csswg-drafts/issues/3503
+        match (&self.count, &other.count) {
+            (&generics::RepeatCount::Number(from), &generics::RepeatCount::Number(to))
+                if from == to =>
+            {
+                ()
+            },
+            (_, _) => return Err(()),
+        }
+
+        // The length of track_sizes should be matched.
+        if self.track_sizes.len() != other.track_sizes.len() {
+            return Err(());
+        }
+
+        let count = self.count;
+        let track_sizes = self
+            .track_sizes
+            .iter()
+            .zip(other.track_sizes.iter())
+            .map(|(a, b)| a.animate(b, procedure))
+            .collect::<Result<Vec<_>, _>>()?;
+
+        // The length of |line_names| is always 0 or N+1, where N is the length
+        // of |track_sizes|. Besides, <line-names> is always discrete.
+        let line_names = discrete(&self.line_names, &other.line_names, procedure)?;
+
+        Ok(generics::TrackRepeat {
+            count,
+            line_names,
+            track_sizes: track_sizes.into(),
+        })
+    }
+}
+
+impl Animate for TrackList {
+    // Based on https://github.com/w3c/csswg-drafts/issues/3201:
+    // 1. Check interpolation type per track, so we need to handle discrete animations
+    //    in TrackSize, so any Err(()) returned from TrackSize doesn't make all TrackSize
+    //    fallback to discrete animation.
+    // 2. line-names is always discrete.
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        if self.values.len() != other.values.len() {
+            return Err(());
+        }
+
+        if self.is_explicit() != other.is_explicit() {
+            return Err(());
+        }
+
+        // For now, repeat(auto-fill/auto-fit, ...) is not animatable.
+        // TrackRepeat will return Err(()) if we use keywords. Therefore, we can
+        // early return here to avoid traversing |values| in <auto-track-list>.
+        // This may be updated in the future.
+        // https://github.com/w3c/csswg-drafts/issues/3503
+        if self.has_auto_repeat() || other.has_auto_repeat() {
+            return Err(());
+        }
+
+        let values = self
+            .values
+            .iter()
+            .zip(other.values.iter())
+            .map(|(a, b)| a.animate(b, procedure))
+            .collect::<Result<Vec<_>, _>>()?;
+        // The length of |line_names| is always 0 or N+1, where N is the length
+        // of |track_sizes|. Besides, <line-names> is always discrete.
+        let line_names = discrete(&self.line_names, &other.line_names, procedure)?;
+
+        Ok(TrackList {
+            values: values.into(),
+            line_names,
+            auto_repeat_index: self.auto_repeat_index,
+        })
+    }
+}
+
+impl ComputeSquaredDistance for GridTemplateComponent {
+    #[inline]
+    fn compute_squared_distance(&self, _other: &Self) -> Result<SquaredDistance, ()> {
+        // TODO: Bug 1518585, we should implement ComputeSquaredDistance.
+        Err(())
+    }
+}
+
+impl ToAnimatedZero for GridTemplateComponent {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        // It's not clear to get a zero grid track list based on the current definition
+        // of spec, so we return Err(()) directly.
+        Err(())
+    }
+}
diff --git a/servo/components/style/values/animated/mod.rs b/servo/components/style/values/animated/mod.rs
new file mode 100644
index 0000000000..b36946c492
--- /dev/null
+++ b/servo/components/style/values/animated/mod.rs
@@ -0,0 +1,489 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Animated values.
+//!
+//! Some values, notably colors, cannot be interpolated directly with their
+//! computed values and need yet another intermediate representation. This
+//! module's raison d'être is to ultimately contain all these types.
+
+use crate::properties::PropertyId;
+use crate::values::computed::length::LengthPercentage;
+use crate::values::computed::url::ComputedUrl;
+use crate::values::computed::Angle as ComputedAngle;
+use crate::values::computed::Image;
+use crate::values::specified::SVGPathData;
+use crate::values::CSSFloat;
+use app_units::Au;
+use smallvec::SmallVec;
+use std::cmp;
+
+pub mod color;
+pub mod effects;
+mod font;
+mod grid;
+mod svg;
+pub mod transform;
+
+/// The category a property falls into for ordering purposes.
+///
+/// https://drafts.csswg.org/web-animations/#calculating-computed-keyframes
+#[derive(Clone, Copy, Eq, Ord, PartialEq, PartialOrd)]
+enum PropertyCategory {
+    Custom,
+    PhysicalLonghand,
+    LogicalLonghand,
+    Shorthand,
+}
+
+impl PropertyCategory {
+    fn of(id: &PropertyId) -> Self {
+        match *id {
+            PropertyId::Shorthand(..) | PropertyId::ShorthandAlias(..) => {
+                PropertyCategory::Shorthand
+            },
+            PropertyId::Longhand(id) | PropertyId::LonghandAlias(id, ..) => {
+                if id.is_logical() {
+                    PropertyCategory::LogicalLonghand
+                } else {
+                    PropertyCategory::PhysicalLonghand
+                }
+            },
+            PropertyId::Custom(..) => PropertyCategory::Custom,
+        }
+    }
+}
+
+/// A comparator to sort PropertyIds such that physical longhands are sorted
+/// before logical longhands and shorthands, shorthands with fewer components
+/// are sorted before shorthands with more components, and otherwise shorthands
+/// are sorted by IDL name as defined by [Web Animations][property-order].
+///
+/// Using this allows us to prioritize values specified by longhands (or smaller
+/// shorthand subsets) when longhands and shorthands are both specified on the
+/// one keyframe.
+///
+/// [property-order] https://drafts.csswg.org/web-animations/#calculating-computed-keyframes
+pub fn compare_property_priority(a: &PropertyId, b: &PropertyId) -> cmp::Ordering {
+    let a_category = PropertyCategory::of(a);
+    let b_category = PropertyCategory::of(b);
+
+    if a_category != b_category {
+        return a_category.cmp(&b_category);
+    }
+
+    if a_category != PropertyCategory::Shorthand {
+        return cmp::Ordering::Equal;
+    }
+
+    let a = a.as_shorthand().unwrap();
+    let b = b.as_shorthand().unwrap();
+    // Within shorthands, sort by the number of subproperties, then by IDL
+    // name.
+    let subprop_count_a = a.longhands().count();
+    let subprop_count_b = b.longhands().count();
+    subprop_count_a
+        .cmp(&subprop_count_b)
+        .then_with(|| a.idl_name_sort_order().cmp(&b.idl_name_sort_order()))
+}
+
+/// A helper function to animate two multiplicative factor.
+pub fn animate_multiplicative_factor(
+    this: CSSFloat,
+    other: CSSFloat,
+    procedure: Procedure,
+) -> Result<CSSFloat, ()> {
+    Ok((this - 1.).animate(&(other - 1.), procedure)? + 1.)
+}
+
+/// Animate from one value to another.
+///
+/// This trait is derivable with `#[derive(Animate)]`. The derived
+/// implementation uses a `match` expression with identical patterns for both
+/// `self` and `other`, calling `Animate::animate` on each fields of the values.
+/// If a field is annotated with `#[animation(constant)]`, the two values should
+/// be equal or an error is returned.
+///
+/// If a variant is annotated with `#[animation(error)]`, the corresponding
+/// `match` arm returns an error.
+///
+/// Trait bounds for type parameter `Foo` can be opted out of with
+/// `#[animation(no_bound(Foo))]` on the type definition, trait bounds for
+/// fields can be opted into with `#[animation(field_bound)]` on the field.
+pub trait Animate: Sized {
+    /// Animate a value towards another one, given an animation procedure.
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()>;
+}
+
+/// An animation procedure.
+///
+/// <https://drafts.csswg.org/web-animations/#procedures-for-animating-properties>
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Procedure {
+    /// <https://drafts.csswg.org/web-animations/#animation-interpolation>
+    Interpolate { progress: f64 },
+    /// <https://drafts.csswg.org/web-animations/#animation-addition>
+    Add,
+    /// <https://drafts.csswg.org/web-animations/#animation-accumulation>
+    Accumulate { count: u64 },
+}
+
+/// Conversion between computed values and intermediate values for animations.
+///
+/// Notably, colors are represented as four floats during animations.
+///
+/// This trait is derivable with `#[derive(ToAnimatedValue)]`.
+pub trait ToAnimatedValue {
+    /// The type of the animated value.
+    type AnimatedValue;
+
+    /// Converts this value to an animated value.
+    fn to_animated_value(self) -> Self::AnimatedValue;
+
+    /// Converts back an animated value into a computed value.
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self;
+}
+
+/// Returns a value similar to `self` that represents zero.
+///
+/// This trait is derivable with `#[derive(ToAnimatedValue)]`. If a field is
+/// annotated with `#[animation(constant)]`, a clone of its value will be used
+/// instead of calling `ToAnimatedZero::to_animated_zero` on it.
+///
+/// If a variant is annotated with `#[animation(error)]`, the corresponding
+/// `match` arm is not generated.
+///
+/// Trait bounds for type parameter `Foo` can be opted out of with
+/// `#[animation(no_bound(Foo))]` on the type definition.
+pub trait ToAnimatedZero: Sized {
+    /// Returns a value that, when added with an underlying value, will produce the underlying
+    /// value. This is used for SMIL animation's "by-animation" where SMIL first interpolates from
+    /// the zero value to the 'by' value, and then adds the result to the underlying value.
+    ///
+    /// This is not the necessarily the same as the initial value of a property. For example, the
+    /// initial value of 'stroke-width' is 1, but the zero value is 0, since adding 1 to the
+    /// underlying value will not produce the underlying value.
+    fn to_animated_zero(&self) -> Result<Self, ()>;
+}
+
+impl Procedure {
+    /// Returns this procedure as a pair of weights.
+    ///
+    /// This is useful for animations that don't animate differently
+    /// depending on the used procedure.
+    #[inline]
+    pub fn weights(self) -> (f64, f64) {
+        match self {
+            Procedure::Interpolate { progress } => (1. - progress, progress),
+            Procedure::Add => (1., 1.),
+            Procedure::Accumulate { count } => (count as f64, 1.),
+        }
+    }
+}
+
+/// <https://drafts.csswg.org/css-transitions/#animtype-number>
+impl Animate for i32 {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(((*self as f64).animate(&(*other as f64), procedure)? + 0.5).floor() as i32)
+    }
+}
+
+/// <https://drafts.csswg.org/css-transitions/#animtype-number>
+impl Animate for f32 {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        use std::f32;
+
+        let ret = (*self as f64).animate(&(*other as f64), procedure)?;
+        Ok(ret.min(f32::MAX as f64).max(f32::MIN as f64) as f32)
+    }
+}
+
+/// <https://drafts.csswg.org/css-transitions/#animtype-number>
+impl Animate for f64 {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        use std::f64;
+
+        let (self_weight, other_weight) = procedure.weights();
+
+        let ret = *self * self_weight + *other * other_weight;
+        Ok(ret.min(f64::MAX).max(f64::MIN))
+    }
+}
+
+impl<T> Animate for Option<T>
+where
+    T: Animate,
+{
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        match (self.as_ref(), other.as_ref()) {
+            (Some(ref this), Some(ref other)) => Ok(Some(this.animate(other, procedure)?)),
+            (None, None) => Ok(None),
+            _ => Err(()),
+        }
+    }
+}
+
+impl Animate for Au {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(Au::new(self.0.animate(&other.0, procedure)?))
+    }
+}
+
+impl<T: Animate> Animate for Box<T> {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(Box::new((**self).animate(&other, procedure)?))
+    }
+}
+
+impl<T> ToAnimatedValue for Option<T>
+where
+    T: ToAnimatedValue,
+{
+    type AnimatedValue = Option<<T as ToAnimatedValue>::AnimatedValue>;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.map(T::to_animated_value)
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        animated.map(T::from_animated_value)
+    }
+}
+
+impl<T> ToAnimatedValue for Vec<T>
+where
+    T: ToAnimatedValue,
+{
+    type AnimatedValue = Vec<<T as ToAnimatedValue>::AnimatedValue>;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.into_iter().map(T::to_animated_value).collect()
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        animated.into_iter().map(T::from_animated_value).collect()
+    }
+}
+
+impl<T> ToAnimatedValue for Box<T>
+where
+    T: ToAnimatedValue,
+{
+    type AnimatedValue = Box<<T as ToAnimatedValue>::AnimatedValue>;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        Box::new((*self).to_animated_value())
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        Box::new(T::from_animated_value(*animated))
+    }
+}
+
+impl<T> ToAnimatedValue for Box<[T]>
+where
+    T: ToAnimatedValue,
+{
+    type AnimatedValue = Box<[<T as ToAnimatedValue>::AnimatedValue]>;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.into_vec()
+            .into_iter()
+            .map(T::to_animated_value)
+            .collect::<Vec<_>>()
+            .into_boxed_slice()
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        animated
+            .into_vec()
+            .into_iter()
+            .map(T::from_animated_value)
+            .collect::<Vec<_>>()
+            .into_boxed_slice()
+    }
+}
+
+impl<T> ToAnimatedValue for crate::OwnedSlice<T>
+where
+    T: ToAnimatedValue,
+{
+    type AnimatedValue = crate::OwnedSlice<<T as ToAnimatedValue>::AnimatedValue>;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.into_box().to_animated_value().into()
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        Self::from(Box::from_animated_value(animated.into_box()))
+    }
+}
+
+impl<T> ToAnimatedValue for SmallVec<[T; 1]>
+where
+    T: ToAnimatedValue,
+{
+    type AnimatedValue = SmallVec<[T::AnimatedValue; 1]>;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.into_iter().map(T::to_animated_value).collect()
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        animated.into_iter().map(T::from_animated_value).collect()
+    }
+}
+
+macro_rules! trivial_to_animated_value {
+    ($ty:ty) => {
+        impl $crate::values::animated::ToAnimatedValue for $ty {
+            type AnimatedValue = Self;
+
+            #[inline]
+            fn to_animated_value(self) -> Self {
+                self
+            }
+
+            #[inline]
+            fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+                animated
+            }
+        }
+    };
+}
+
+trivial_to_animated_value!(Au);
+trivial_to_animated_value!(LengthPercentage);
+trivial_to_animated_value!(ComputedAngle);
+trivial_to_animated_value!(ComputedUrl);
+trivial_to_animated_value!(bool);
+trivial_to_animated_value!(f32);
+trivial_to_animated_value!(i32);
+// Note: This implementation is for ToAnimatedValue of ShapeSource.
+//
+// SVGPathData uses Box<[T]>. If we want to derive ToAnimatedValue for all the
+// types, we have to do "impl ToAnimatedValue for Box<[T]>" first.
+// However, the general version of "impl ToAnimatedValue for Box<[T]>" needs to
+// clone |T| and convert it into |T::AnimatedValue|. However, for SVGPathData
+// that is unnecessary--moving |T| is sufficient. So here, we implement this
+// trait manually.
+trivial_to_animated_value!(SVGPathData);
+// FIXME: Bug 1514342, Image is not animatable, but we still need to implement
+// this to avoid adding this derive to generic::Image and all its arms. We can
+// drop this after landing Bug 1514342.
+trivial_to_animated_value!(Image);
+
+impl ToAnimatedZero for Au {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(Au(0))
+    }
+}
+
+impl ToAnimatedZero for f32 {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(0.)
+    }
+}
+
+impl ToAnimatedZero for f64 {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(0.)
+    }
+}
+
+impl ToAnimatedZero for i32 {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(0)
+    }
+}
+
+impl<T> ToAnimatedZero for Box<T>
+where
+    T: ToAnimatedZero,
+{
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(Box::new((**self).to_animated_zero()?))
+    }
+}
+
+impl<T> ToAnimatedZero for Option<T>
+where
+    T: ToAnimatedZero,
+{
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        match *self {
+            Some(ref value) => Ok(Some(value.to_animated_zero()?)),
+            None => Ok(None),
+        }
+    }
+}
+
+impl<T> ToAnimatedZero for Vec<T>
+where
+    T: ToAnimatedZero,
+{
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        self.iter().map(|v| v.to_animated_zero()).collect()
+    }
+}
+
+impl<T> ToAnimatedZero for Box<[T]>
+where
+    T: ToAnimatedZero,
+{
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        self.iter().map(|v| v.to_animated_zero()).collect()
+    }
+}
+
+impl<T> ToAnimatedZero for crate::OwnedSlice<T>
+where
+    T: ToAnimatedZero,
+{
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        self.iter().map(|v| v.to_animated_zero()).collect()
+    }
+}
+
+impl<T> ToAnimatedZero for crate::ArcSlice<T>
+where
+    T: ToAnimatedZero,
+{
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        let v = self
+            .iter()
+            .map(|v| v.to_animated_zero())
+            .collect::<Result<Vec<_>, _>>()?;
+        Ok(crate::ArcSlice::from_iter(v.into_iter()))
+    }
+}
diff --git a/servo/components/style/values/animated/svg.rs b/servo/components/style/values/animated/svg.rs
new file mode 100644
index 0000000000..13ad10174b
--- /dev/null
+++ b/servo/components/style/values/animated/svg.rs
@@ -0,0 +1,45 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Animation implementations for various SVG-related types.
+
+use super::{Animate, Procedure};
+use crate::properties::animated_properties::ListAnimation;
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::svg::SVGStrokeDashArray;
+
+/// <https://www.w3.org/TR/SVG11/painting.html#StrokeDasharrayProperty>
+impl<L> Animate for SVGStrokeDashArray<L>
+where
+    L: Clone + Animate,
+{
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        if matches!(procedure, Procedure::Add | Procedure::Accumulate { .. }) {
+            // Non-additive.
+            return Err(());
+        }
+        match (self, other) {
+            (&SVGStrokeDashArray::Values(ref this), &SVGStrokeDashArray::Values(ref other)) => Ok(
+                SVGStrokeDashArray::Values(this.animate_repeatable_list(other, procedure)?),
+            ),
+            _ => Err(()),
+        }
+    }
+}
+
+impl<L> ComputeSquaredDistance for SVGStrokeDashArray<L>
+where
+    L: ComputeSquaredDistance,
+{
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        match (self, other) {
+            (&SVGStrokeDashArray::Values(ref this), &SVGStrokeDashArray::Values(ref other)) => {
+                this.squared_distance_repeatable_list(other)
+            },
+            _ => Err(()),
+        }
+    }
+}
diff --git a/servo/components/style/values/animated/transform.rs b/servo/components/style/values/animated/transform.rs
new file mode 100644
index 0000000000..bb1b4e910c
--- /dev/null
+++ b/servo/components/style/values/animated/transform.rs
@@ -0,0 +1,1484 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Animated types for transform.
+// There are still some implementation on Matrix3D in animated_properties.mako.rs
+// because they still need mako to generate the code.
+
+use super::animate_multiplicative_factor;
+use super::{Animate, Procedure, ToAnimatedZero};
+use crate::properties::animated_properties::ListAnimation;
+use crate::values::computed::transform::Rotate as ComputedRotate;
+use crate::values::computed::transform::Scale as ComputedScale;
+use crate::values::computed::transform::Transform as ComputedTransform;
+use crate::values::computed::transform::TransformOperation as ComputedTransformOperation;
+use crate::values::computed::transform::Translate as ComputedTranslate;
+use crate::values::computed::transform::{DirectionVector, Matrix, Matrix3D};
+use crate::values::computed::Angle;
+use crate::values::computed::{Length, LengthPercentage};
+use crate::values::computed::{Number, Percentage};
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::transform::{self, Transform, TransformOperation};
+use crate::values::generics::transform::{Rotate, Scale, Translate};
+use crate::values::CSSFloat;
+use crate::Zero;
+use std::cmp;
+
+// ------------------------------------
+// Animations for Matrix/Matrix3D.
+// ------------------------------------
+/// A 2d matrix for interpolation.
+#[derive(Clone, ComputeSquaredDistance, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+#[allow(missing_docs)]
+// FIXME: We use custom derive for ComputeSquaredDistance. However, If possible, we should convert
+// the InnerMatrix2D into types with physical meaning. This custom derive computes the squared
+// distance from each matrix item, and this makes the result different from that in Gecko if we
+// have skew factor in the Matrix3D.
+pub struct InnerMatrix2D {
+    pub m11: CSSFloat,
+    pub m12: CSSFloat,
+    pub m21: CSSFloat,
+    pub m22: CSSFloat,
+}
+
+impl Animate for InnerMatrix2D {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(InnerMatrix2D {
+            m11: animate_multiplicative_factor(self.m11, other.m11, procedure)?,
+            m12: self.m12.animate(&other.m12, procedure)?,
+            m21: self.m21.animate(&other.m21, procedure)?,
+            m22: animate_multiplicative_factor(self.m22, other.m22, procedure)?,
+        })
+    }
+}
+
+/// A 2d translation function.
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+#[derive(Animate, Clone, ComputeSquaredDistance, Copy, Debug)]
+pub struct Translate2D(f32, f32);
+
+/// A 2d scale function.
+#[derive(Clone, ComputeSquaredDistance, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+pub struct Scale2D(f32, f32);
+
+impl Animate for Scale2D {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(Scale2D(
+            animate_multiplicative_factor(self.0, other.0, procedure)?,
+            animate_multiplicative_factor(self.1, other.1, procedure)?,
+        ))
+    }
+}
+
+/// A decomposed 2d matrix.
+#[derive(Clone, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+pub struct MatrixDecomposed2D {
+    /// The translation function.
+    pub translate: Translate2D,
+    /// The scale function.
+    pub scale: Scale2D,
+    /// The rotation angle.
+    pub angle: f32,
+    /// The inner matrix.
+    pub matrix: InnerMatrix2D,
+}
+
+impl Animate for MatrixDecomposed2D {
+    /// <https://drafts.csswg.org/css-transforms/#interpolation-of-decomposed-2d-matrix-values>
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        // If x-axis of one is flipped, and y-axis of the other,
+        // convert to an unflipped rotation.
+        let mut scale = self.scale;
+        let mut angle = self.angle;
+        let mut other_angle = other.angle;
+        if (scale.0 < 0.0 && other.scale.1 < 0.0) || (scale.1 < 0.0 && other.scale.0 < 0.0) {
+            scale.0 = -scale.0;
+            scale.1 = -scale.1;
+            angle += if angle < 0.0 { 180. } else { -180. };
+        }
+
+        // Don't rotate the long way around.
+        if angle == 0.0 {
+            angle = 360.
+        }
+        if other_angle == 0.0 {
+            other_angle = 360.
+        }
+
+        if (angle - other_angle).abs() > 180. {
+            if angle > other_angle {
+                angle -= 360.
+            } else {
+                other_angle -= 360.
+            }
+        }
+
+        // Interpolate all values.
+        let translate = self.translate.animate(&other.translate, procedure)?;
+        let scale = scale.animate(&other.scale, procedure)?;
+        let angle = angle.animate(&other_angle, procedure)?;
+        let matrix = self.matrix.animate(&other.matrix, procedure)?;
+
+        Ok(MatrixDecomposed2D {
+            translate,
+            scale,
+            angle,
+            matrix,
+        })
+    }
+}
+
+impl ComputeSquaredDistance for MatrixDecomposed2D {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        // Use Radian to compute the distance.
+        const RAD_PER_DEG: f64 = std::f64::consts::PI / 180.0;
+        let angle1 = self.angle as f64 * RAD_PER_DEG;
+        let angle2 = other.angle as f64 * RAD_PER_DEG;
+        Ok(self.translate.compute_squared_distance(&other.translate)? +
+            self.scale.compute_squared_distance(&other.scale)? +
+            angle1.compute_squared_distance(&angle2)? +
+            self.matrix.compute_squared_distance(&other.matrix)?)
+    }
+}
+
+impl From<Matrix3D> for MatrixDecomposed2D {
+    /// Decompose a 2D matrix.
+    /// <https://drafts.csswg.org/css-transforms/#decomposing-a-2d-matrix>
+    fn from(matrix: Matrix3D) -> MatrixDecomposed2D {
+        let mut row0x = matrix.m11;
+        let mut row0y = matrix.m12;
+        let mut row1x = matrix.m21;
+        let mut row1y = matrix.m22;
+
+        let translate = Translate2D(matrix.m41, matrix.m42);
+        let mut scale = Scale2D(
+            (row0x * row0x + row0y * row0y).sqrt(),
+            (row1x * row1x + row1y * row1y).sqrt(),
+        );
+
+        // If determinant is negative, one axis was flipped.
+        let determinant = row0x * row1y - row0y * row1x;
+        if determinant < 0. {
+            if row0x < row1y {
+                scale.0 = -scale.0;
+            } else {
+                scale.1 = -scale.1;
+            }
+        }
+
+        // Renormalize matrix to remove scale.
+        if scale.0 != 0.0 {
+            row0x *= 1. / scale.0;
+            row0y *= 1. / scale.0;
+        }
+        if scale.1 != 0.0 {
+            row1x *= 1. / scale.1;
+            row1y *= 1. / scale.1;
+        }
+
+        // Compute rotation and renormalize matrix.
+        let mut angle = row0y.atan2(row0x);
+        if angle != 0.0 {
+            let sn = -row0y;
+            let cs = row0x;
+            let m11 = row0x;
+            let m12 = row0y;
+            let m21 = row1x;
+            let m22 = row1y;
+            row0x = cs * m11 + sn * m21;
+            row0y = cs * m12 + sn * m22;
+            row1x = -sn * m11 + cs * m21;
+            row1y = -sn * m12 + cs * m22;
+        }
+
+        let m = InnerMatrix2D {
+            m11: row0x,
+            m12: row0y,
+            m21: row1x,
+            m22: row1y,
+        };
+
+        // Convert into degrees because our rotation functions expect it.
+        angle = angle.to_degrees();
+        MatrixDecomposed2D {
+            translate: translate,
+            scale: scale,
+            angle: angle,
+            matrix: m,
+        }
+    }
+}
+
+impl From<MatrixDecomposed2D> for Matrix3D {
+    /// Recompose a 2D matrix.
+    /// <https://drafts.csswg.org/css-transforms/#recomposing-to-a-2d-matrix>
+    fn from(decomposed: MatrixDecomposed2D) -> Matrix3D {
+        let mut computed_matrix = Matrix3D::identity();
+        computed_matrix.m11 = decomposed.matrix.m11;
+        computed_matrix.m12 = decomposed.matrix.m12;
+        computed_matrix.m21 = decomposed.matrix.m21;
+        computed_matrix.m22 = decomposed.matrix.m22;
+
+        // Translate matrix.
+        computed_matrix.m41 = decomposed.translate.0;
+        computed_matrix.m42 = decomposed.translate.1;
+
+        // Rotate matrix.
+        let angle = decomposed.angle.to_radians();
+        let cos_angle = angle.cos();
+        let sin_angle = angle.sin();
+
+        let mut rotate_matrix = Matrix3D::identity();
+        rotate_matrix.m11 = cos_angle;
+        rotate_matrix.m12 = sin_angle;
+        rotate_matrix.m21 = -sin_angle;
+        rotate_matrix.m22 = cos_angle;
+
+        // Multiplication of computed_matrix and rotate_matrix
+        computed_matrix = rotate_matrix.multiply(&computed_matrix);
+
+        // Scale matrix.
+        computed_matrix.m11 *= decomposed.scale.0;
+        computed_matrix.m12 *= decomposed.scale.0;
+        computed_matrix.m21 *= decomposed.scale.1;
+        computed_matrix.m22 *= decomposed.scale.1;
+        computed_matrix
+    }
+}
+
+impl Animate for Matrix {
+    #[cfg(feature = "servo")]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let this = Matrix3D::from(*self);
+        let other = Matrix3D::from(*other);
+        let this = MatrixDecomposed2D::from(this);
+        let other = MatrixDecomposed2D::from(other);
+        Ok(Matrix3D::from(this.animate(&other, procedure)?).into_2d()?)
+    }
+
+    #[cfg(feature = "gecko")]
+    // Gecko doesn't exactly follow the spec here; we use a different procedure
+    // to match it
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let from = decompose_2d_matrix(&(*self).into());
+        let to = decompose_2d_matrix(&(*other).into());
+        match (from, to) {
+            (Ok(from), Ok(to)) => Matrix3D::from(from.animate(&to, procedure)?).into_2d(),
+            // Matrices can be undecomposable due to couple reasons, e.g.,
+            // non-invertible matrices. In this case, we should report Err here,
+            // and let the caller do the fallback procedure.
+            _ => Err(()),
+        }
+    }
+}
+
+/// A 3d translation.
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+#[derive(Animate, Clone, ComputeSquaredDistance, Copy, Debug)]
+pub struct Translate3D(pub f32, pub f32, pub f32);
+
+/// A 3d scale function.
+#[derive(Clone, ComputeSquaredDistance, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+pub struct Scale3D(pub f32, pub f32, pub f32);
+
+impl Scale3D {
+    /// Negate self.
+    fn negate(&mut self) {
+        self.0 *= -1.0;
+        self.1 *= -1.0;
+        self.2 *= -1.0;
+    }
+}
+
+impl Animate for Scale3D {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(Scale3D(
+            animate_multiplicative_factor(self.0, other.0, procedure)?,
+            animate_multiplicative_factor(self.1, other.1, procedure)?,
+            animate_multiplicative_factor(self.2, other.2, procedure)?,
+        ))
+    }
+}
+
+/// A 3d skew function.
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+#[derive(Animate, Clone, Copy, Debug)]
+pub struct Skew(f32, f32, f32);
+
+impl ComputeSquaredDistance for Skew {
+    // We have to use atan() to convert the skew factors into skew angles, so implement
+    // ComputeSquaredDistance manually.
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        Ok(self.0.atan().compute_squared_distance(&other.0.atan())? +
+            self.1.atan().compute_squared_distance(&other.1.atan())? +
+            self.2.atan().compute_squared_distance(&other.2.atan())?)
+    }
+}
+
+/// A 3d perspective transformation.
+#[derive(Clone, ComputeSquaredDistance, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+pub struct Perspective(pub f32, pub f32, pub f32, pub f32);
+
+impl Animate for Perspective {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(Perspective(
+            self.0.animate(&other.0, procedure)?,
+            self.1.animate(&other.1, procedure)?,
+            self.2.animate(&other.2, procedure)?,
+            animate_multiplicative_factor(self.3, other.3, procedure)?,
+        ))
+    }
+}
+
+/// A quaternion used to represent a rotation.
+#[derive(Clone, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+pub struct Quaternion(f64, f64, f64, f64);
+
+impl Quaternion {
+    /// Return a quaternion from a unit direction vector and angle (unit: radian).
+    #[inline]
+    fn from_direction_and_angle(vector: &DirectionVector, angle: f64) -> Self {
+        debug_assert!(
+            (vector.length() - 1.).abs() < 0.0001,
+            "Only accept an unit direction vector to create a quaternion"
+        );
+        // Reference:
+        // https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation
+        //
+        // if the direction axis is (x, y, z) = xi + yj + zk,
+        // and the angle is |theta|, this formula can be done using
+        // an extension of Euler's formula:
+        //   q = cos(theta/2) + (xi + yj + zk)(sin(theta/2))
+        //     = cos(theta/2) +
+        //       x*sin(theta/2)i + y*sin(theta/2)j + z*sin(theta/2)k
+        Quaternion(
+            vector.x as f64 * (angle / 2.).sin(),
+            vector.y as f64 * (angle / 2.).sin(),
+            vector.z as f64 * (angle / 2.).sin(),
+            (angle / 2.).cos(),
+        )
+    }
+
+    /// Calculate the dot product.
+    #[inline]
+    fn dot(&self, other: &Self) -> f64 {
+        self.0 * other.0 + self.1 * other.1 + self.2 * other.2 + self.3 * other.3
+    }
+
+    /// Return the scaled quaternion by a factor.
+    #[inline]
+    fn scale(&self, factor: f64) -> Self {
+        Quaternion(
+            self.0 * factor,
+            self.1 * factor,
+            self.2 * factor,
+            self.3 * factor,
+        )
+    }
+}
+
+impl Animate for Quaternion {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        use std::f64;
+
+        let (this_weight, other_weight) = procedure.weights();
+        debug_assert!(
+            // Doule EPSILON since both this_weight and other_weght have calculation errors
+            // which are approximately equal to EPSILON.
+            (this_weight + other_weight - 1.0f64).abs() <= f64::EPSILON * 2.0 ||
+                other_weight == 1.0f64 ||
+                other_weight == 0.0f64,
+            "animate should only be used for interpolating or accumulating transforms"
+        );
+
+        // We take a specialized code path for accumulation (where other_weight
+        // is 1).
+        if let Procedure::Accumulate { .. } = procedure {
+            debug_assert_eq!(other_weight, 1.0);
+            if this_weight == 0.0 {
+                return Ok(*other);
+            }
+
+            let clamped_w = self.3.min(1.0).max(-1.0);
+
+            // Determine the scale factor.
+            let mut theta = clamped_w.acos();
+            let mut scale = if theta == 0.0 { 0.0 } else { 1.0 / theta.sin() };
+            theta *= this_weight;
+            scale *= theta.sin();
+
+            // Scale the self matrix by this_weight.
+            let mut scaled_self = *self;
+            scaled_self.0 *= scale;
+            scaled_self.1 *= scale;
+            scaled_self.2 *= scale;
+            scaled_self.3 = theta.cos();
+
+            // Multiply scaled-self by other.
+            let a = &scaled_self;
+            let b = other;
+            return Ok(Quaternion(
+                a.3 * b.0 + a.0 * b.3 + a.1 * b.2 - a.2 * b.1,
+                a.3 * b.1 - a.0 * b.2 + a.1 * b.3 + a.2 * b.0,
+                a.3 * b.2 + a.0 * b.1 - a.1 * b.0 + a.2 * b.3,
+                a.3 * b.3 - a.0 * b.0 - a.1 * b.1 - a.2 * b.2,
+            ));
+        }
+
+        // Straight from gfxQuaternion::Slerp.
+        //
+        // Dot product, clamped between -1 and 1.
+        let dot = (self.0 * other.0 + self.1 * other.1 + self.2 * other.2 + self.3 * other.3)
+            .min(1.0)
+            .max(-1.0);
+
+        if dot.abs() == 1.0 {
+            return Ok(*self);
+        }
+
+        let theta = dot.acos();
+        let rsintheta = 1.0 / (1.0 - dot * dot).sqrt();
+
+        let right_weight = (other_weight * theta).sin() * rsintheta;
+        let left_weight = (other_weight * theta).cos() - dot * right_weight;
+
+        let left = self.scale(left_weight);
+        let right = other.scale(right_weight);
+
+        Ok(Quaternion(
+            left.0 + right.0,
+            left.1 + right.1,
+            left.2 + right.2,
+            left.3 + right.3,
+        ))
+    }
+}
+
+impl ComputeSquaredDistance for Quaternion {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        // Use quaternion vectors to get the angle difference. Both q1 and q2 are unit vectors,
+        // so we can get their angle difference by:
+        // cos(theta/2) = (q1 dot q2) / (|q1| * |q2|) = q1 dot q2.
+        let distance = self.dot(other).max(-1.0).min(1.0).acos() * 2.0;
+        Ok(SquaredDistance::from_sqrt(distance))
+    }
+}
+
+/// A decomposed 3d matrix.
+#[derive(Animate, Clone, ComputeSquaredDistance, Copy, Debug)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+pub struct MatrixDecomposed3D {
+    /// A translation function.
+    pub translate: Translate3D,
+    /// A scale function.
+    pub scale: Scale3D,
+    /// The skew component of the transformation.
+    pub skew: Skew,
+    /// The perspective component of the transformation.
+    pub perspective: Perspective,
+    /// The quaternion used to represent the rotation.
+    pub quaternion: Quaternion,
+}
+
+impl From<MatrixDecomposed3D> for Matrix3D {
+    /// Recompose a 3D matrix.
+    /// <https://drafts.csswg.org/css-transforms/#recomposing-to-a-3d-matrix>
+    fn from(decomposed: MatrixDecomposed3D) -> Matrix3D {
+        let mut matrix = Matrix3D::identity();
+
+        // Apply perspective
+        matrix.set_perspective(&decomposed.perspective);
+
+        // Apply translation
+        matrix.apply_translate(&decomposed.translate);
+
+        // Apply rotation
+        {
+            let x = decomposed.quaternion.0;
+            let y = decomposed.quaternion.1;
+            let z = decomposed.quaternion.2;
+            let w = decomposed.quaternion.3;
+
+            // Construct a composite rotation matrix from the quaternion values
+            // rotationMatrix is a identity 4x4 matrix initially
+            let mut rotation_matrix = Matrix3D::identity();
+            rotation_matrix.m11 = 1.0 - 2.0 * (y * y + z * z) as f32;
+            rotation_matrix.m12 = 2.0 * (x * y + z * w) as f32;
+            rotation_matrix.m13 = 2.0 * (x * z - y * w) as f32;
+            rotation_matrix.m21 = 2.0 * (x * y - z * w) as f32;
+            rotation_matrix.m22 = 1.0 - 2.0 * (x * x + z * z) as f32;
+            rotation_matrix.m23 = 2.0 * (y * z + x * w) as f32;
+            rotation_matrix.m31 = 2.0 * (x * z + y * w) as f32;
+            rotation_matrix.m32 = 2.0 * (y * z - x * w) as f32;
+            rotation_matrix.m33 = 1.0 - 2.0 * (x * x + y * y) as f32;
+
+            matrix = rotation_matrix.multiply(&matrix);
+        }
+
+        // Apply skew
+        {
+            let mut temp = Matrix3D::identity();
+            if decomposed.skew.2 != 0.0 {
+                temp.m32 = decomposed.skew.2;
+                matrix = temp.multiply(&matrix);
+                temp.m32 = 0.0;
+            }
+
+            if decomposed.skew.1 != 0.0 {
+                temp.m31 = decomposed.skew.1;
+                matrix = temp.multiply(&matrix);
+                temp.m31 = 0.0;
+            }
+
+            if decomposed.skew.0 != 0.0 {
+                temp.m21 = decomposed.skew.0;
+                matrix = temp.multiply(&matrix);
+            }
+        }
+
+        // Apply scale
+        matrix.apply_scale(&decomposed.scale);
+
+        matrix
+    }
+}
+
+/// Decompose a 3D matrix.
+/// https://drafts.csswg.org/css-transforms-2/#decomposing-a-3d-matrix
+/// http://www.realtimerendering.com/resources/GraphicsGems/gemsii/unmatrix.c
+fn decompose_3d_matrix(mut matrix: Matrix3D) -> Result<MatrixDecomposed3D, ()> {
+    // Combine 2 point.
+    let combine = |a: [f32; 3], b: [f32; 3], ascl: f32, bscl: f32| {
+        [
+            (ascl * a[0]) + (bscl * b[0]),
+            (ascl * a[1]) + (bscl * b[1]),
+            (ascl * a[2]) + (bscl * b[2]),
+        ]
+    };
+    // Dot product.
+    let dot = |a: [f32; 3], b: [f32; 3]| a[0] * b[0] + a[1] * b[1] + a[2] * b[2];
+    // Cross product.
+    let cross = |row1: [f32; 3], row2: [f32; 3]| {
+        [
+            row1[1] * row2[2] - row1[2] * row2[1],
+            row1[2] * row2[0] - row1[0] * row2[2],
+            row1[0] * row2[1] - row1[1] * row2[0],
+        ]
+    };
+
+    if matrix.m44 == 0.0 {
+        return Err(());
+    }
+
+    let scaling_factor = matrix.m44;
+
+    // Normalize the matrix.
+    matrix.scale_by_factor(1.0 / scaling_factor);
+
+    // perspective_matrix is used to solve for perspective, but it also provides
+    // an easy way to test for singularity of the upper 3x3 component.
+    let mut perspective_matrix = matrix;
+
+    perspective_matrix.m14 = 0.0;
+    perspective_matrix.m24 = 0.0;
+    perspective_matrix.m34 = 0.0;
+    perspective_matrix.m44 = 1.0;
+
+    if perspective_matrix.determinant() == 0.0 {
+        return Err(());
+    }
+
+    // First, isolate perspective.
+    let perspective = if matrix.m14 != 0.0 || matrix.m24 != 0.0 || matrix.m34 != 0.0 {
+        let right_hand_side: [f32; 4] = [matrix.m14, matrix.m24, matrix.m34, matrix.m44];
+
+        perspective_matrix = perspective_matrix.inverse().unwrap().transpose();
+        let perspective = perspective_matrix.pre_mul_point4(&right_hand_side);
+        // NOTE(emilio): Even though the reference algorithm clears the
+        // fourth column here (matrix.m14..matrix.m44), they're not used below
+        // so it's not really needed.
+        Perspective(
+            perspective[0],
+            perspective[1],
+            perspective[2],
+            perspective[3],
+        )
+    } else {
+        Perspective(0.0, 0.0, 0.0, 1.0)
+    };
+
+    // Next take care of translation (easy).
+    let translate = Translate3D(matrix.m41, matrix.m42, matrix.m43);
+
+    // Now get scale and shear. 'row' is a 3 element array of 3 component vectors
+    let mut row = matrix.get_matrix_3x3_part();
+
+    // Compute X scale factor and normalize first row.
+    let row0len = (row[0][0] * row[0][0] + row[0][1] * row[0][1] + row[0][2] * row[0][2]).sqrt();
+    let mut scale = Scale3D(row0len, 0.0, 0.0);
+    row[0] = [
+        row[0][0] / row0len,
+        row[0][1] / row0len,
+        row[0][2] / row0len,
+    ];
+
+    // Compute XY shear factor and make 2nd row orthogonal to 1st.
+    let mut skew = Skew(dot(row[0], row[1]), 0.0, 0.0);
+    row[1] = combine(row[1], row[0], 1.0, -skew.0);
+
+    // Now, compute Y scale and normalize 2nd row.
+    let row1len = (row[1][0] * row[1][0] + row[1][1] * row[1][1] + row[1][2] * row[1][2]).sqrt();
+    scale.1 = row1len;
+    row[1] = [
+        row[1][0] / row1len,
+        row[1][1] / row1len,
+        row[1][2] / row1len,
+    ];
+    skew.0 /= scale.1;
+
+    // Compute XZ and YZ shears, orthogonalize 3rd row
+    skew.1 = dot(row[0], row[2]);
+    row[2] = combine(row[2], row[0], 1.0, -skew.1);
+    skew.2 = dot(row[1], row[2]);
+    row[2] = combine(row[2], row[1], 1.0, -skew.2);
+
+    // Next, get Z scale and normalize 3rd row.
+    let row2len = (row[2][0] * row[2][0] + row[2][1] * row[2][1] + row[2][2] * row[2][2]).sqrt();
+    scale.2 = row2len;
+    row[2] = [
+        row[2][0] / row2len,
+        row[2][1] / row2len,
+        row[2][2] / row2len,
+    ];
+    skew.1 /= scale.2;
+    skew.2 /= scale.2;
+
+    // At this point, the matrix (in rows) is orthonormal.
+    // Check for a coordinate system flip.  If the determinant
+    // is -1, then negate the matrix and the scaling factors.
+    if dot(row[0], cross(row[1], row[2])) < 0.0 {
+        scale.negate();
+        for i in 0..3 {
+            row[i][0] *= -1.0;
+            row[i][1] *= -1.0;
+            row[i][2] *= -1.0;
+        }
+    }
+
+    // Now, get the rotations out.
+    let mut quaternion = Quaternion(
+        0.5 * ((1.0 + row[0][0] - row[1][1] - row[2][2]).max(0.0) as f64).sqrt(),
+        0.5 * ((1.0 - row[0][0] + row[1][1] - row[2][2]).max(0.0) as f64).sqrt(),
+        0.5 * ((1.0 - row[0][0] - row[1][1] + row[2][2]).max(0.0) as f64).sqrt(),
+        0.5 * ((1.0 + row[0][0] + row[1][1] + row[2][2]).max(0.0) as f64).sqrt(),
+    );
+
+    if row[2][1] > row[1][2] {
+        quaternion.0 = -quaternion.0
+    }
+    if row[0][2] > row[2][0] {
+        quaternion.1 = -quaternion.1
+    }
+    if row[1][0] > row[0][1] {
+        quaternion.2 = -quaternion.2
+    }
+
+    Ok(MatrixDecomposed3D {
+        translate,
+        scale,
+        skew,
+        perspective,
+        quaternion,
+    })
+}
+
+/// Decompose a 2D matrix for Gecko.
+// Use the algorithm from nsStyleTransformMatrix::Decompose2DMatrix() in Gecko.
+#[cfg(feature = "gecko")]
+fn decompose_2d_matrix(matrix: &Matrix3D) -> Result<MatrixDecomposed3D, ()> {
+    // The index is column-major, so the equivalent transform matrix is:
+    // | m11 m21  0 m41 |  =>  | m11 m21 | and translate(m41, m42)
+    // | m12 m22  0 m42 |      | m12 m22 |
+    // |   0   0  1   0 |
+    // |   0   0  0   1 |
+    let (mut m11, mut m12) = (matrix.m11, matrix.m12);
+    let (mut m21, mut m22) = (matrix.m21, matrix.m22);
+    // Check if this is a singular matrix.
+    if m11 * m22 == m12 * m21 {
+        return Err(());
+    }
+
+    let mut scale_x = (m11 * m11 + m12 * m12).sqrt();
+    m11 /= scale_x;
+    m12 /= scale_x;
+
+    let mut shear_xy = m11 * m21 + m12 * m22;
+    m21 -= m11 * shear_xy;
+    m22 -= m12 * shear_xy;
+
+    let scale_y = (m21 * m21 + m22 * m22).sqrt();
+    m21 /= scale_y;
+    m22 /= scale_y;
+    shear_xy /= scale_y;
+
+    let determinant = m11 * m22 - m12 * m21;
+    // Determinant should now be 1 or -1.
+    if 0.99 > determinant.abs() || determinant.abs() > 1.01 {
+        return Err(());
+    }
+
+    if determinant < 0. {
+        m11 = -m11;
+        m12 = -m12;
+        shear_xy = -shear_xy;
+        scale_x = -scale_x;
+    }
+
+    Ok(MatrixDecomposed3D {
+        translate: Translate3D(matrix.m41, matrix.m42, 0.),
+        scale: Scale3D(scale_x, scale_y, 1.),
+        skew: Skew(shear_xy, 0., 0.),
+        perspective: Perspective(0., 0., 0., 1.),
+        quaternion: Quaternion::from_direction_and_angle(
+            &DirectionVector::new(0., 0., 1.),
+            m12.atan2(m11) as f64,
+        ),
+    })
+}
+
+impl Animate for Matrix3D {
+    #[cfg(feature = "servo")]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        if self.is_3d() || other.is_3d() {
+            let decomposed_from = decompose_3d_matrix(*self);
+            let decomposed_to = decompose_3d_matrix(*other);
+            match (decomposed_from, decomposed_to) {
+                (Ok(this), Ok(other)) => Ok(Matrix3D::from(this.animate(&other, procedure)?)),
+                // Matrices can be undecomposable due to couple reasons, e.g.,
+                // non-invertible matrices. In this case, we should report Err
+                // here, and let the caller do the fallback procedure.
+                _ => Err(()),
+            }
+        } else {
+            let this = MatrixDecomposed2D::from(*self);
+            let other = MatrixDecomposed2D::from(*other);
+            Ok(Matrix3D::from(this.animate(&other, procedure)?))
+        }
+    }
+
+    #[cfg(feature = "gecko")]
+    // Gecko doesn't exactly follow the spec here; we use a different procedure
+    // to match it
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        let (from, to) = if self.is_3d() || other.is_3d() {
+            (decompose_3d_matrix(*self), decompose_3d_matrix(*other))
+        } else {
+            (decompose_2d_matrix(self), decompose_2d_matrix(other))
+        };
+        match (from, to) {
+            (Ok(from), Ok(to)) => Ok(Matrix3D::from(from.animate(&to, procedure)?)),
+            // Matrices can be undecomposable due to couple reasons, e.g.,
+            // non-invertible matrices. In this case, we should report Err here,
+            // and let the caller do the fallback procedure.
+            _ => Err(()),
+        }
+    }
+}
+
+impl ComputeSquaredDistance for Matrix3D {
+    #[inline]
+    #[cfg(feature = "servo")]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        if self.is_3d() || other.is_3d() {
+            let from = decompose_3d_matrix(*self)?;
+            let to = decompose_3d_matrix(*other)?;
+            from.compute_squared_distance(&to)
+        } else {
+            let from = MatrixDecomposed2D::from(*self);
+            let to = MatrixDecomposed2D::from(*other);
+            from.compute_squared_distance(&to)
+        }
+    }
+
+    #[inline]
+    #[cfg(feature = "gecko")]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let (from, to) = if self.is_3d() || other.is_3d() {
+            (decompose_3d_matrix(*self)?, decompose_3d_matrix(*other)?)
+        } else {
+            (decompose_2d_matrix(self)?, decompose_2d_matrix(other)?)
+        };
+        from.compute_squared_distance(&to)
+    }
+}
+
+// ------------------------------------
+// Animation for Transform list.
+// ------------------------------------
+fn is_matched_operation(
+    first: &ComputedTransformOperation,
+    second: &ComputedTransformOperation,
+) -> bool {
+    match (first, second) {
+        (&TransformOperation::Matrix(..), &TransformOperation::Matrix(..)) |
+        (&TransformOperation::Matrix3D(..), &TransformOperation::Matrix3D(..)) |
+        (&TransformOperation::Skew(..), &TransformOperation::Skew(..)) |
+        (&TransformOperation::SkewX(..), &TransformOperation::SkewX(..)) |
+        (&TransformOperation::SkewY(..), &TransformOperation::SkewY(..)) |
+        (&TransformOperation::Rotate(..), &TransformOperation::Rotate(..)) |
+        (&TransformOperation::Rotate3D(..), &TransformOperation::Rotate3D(..)) |
+        (&TransformOperation::RotateX(..), &TransformOperation::RotateX(..)) |
+        (&TransformOperation::RotateY(..), &TransformOperation::RotateY(..)) |
+        (&TransformOperation::RotateZ(..), &TransformOperation::RotateZ(..)) |
+        (&TransformOperation::Perspective(..), &TransformOperation::Perspective(..)) => true,
+        // Match functions that have the same primitive transform function
+        (a, b) if a.is_translate() && b.is_translate() => true,
+        (a, b) if a.is_scale() && b.is_scale() => true,
+        (a, b) if a.is_rotate() && b.is_rotate() => true,
+        // InterpolateMatrix and AccumulateMatrix are for mismatched transforms
+        _ => false,
+    }
+}
+
+/// <https://drafts.csswg.org/css-transforms/#interpolation-of-transforms>
+impl Animate for ComputedTransform {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        use std::borrow::Cow;
+
+        // Addition for transforms simply means appending to the list of
+        // transform functions. This is different to how we handle the other
+        // animation procedures so we treat it separately here rather than
+        // handling it in TransformOperation.
+        if procedure == Procedure::Add {
+            let result = self.0.iter().chain(&*other.0).cloned().collect();
+            return Ok(Transform(result));
+        }
+
+        let this = Cow::Borrowed(&self.0);
+        let other = Cow::Borrowed(&other.0);
+
+        // Interpolate the common prefix
+        let mut result = this
+            .iter()
+            .zip(other.iter())
+            .take_while(|(this, other)| is_matched_operation(this, other))
+            .map(|(this, other)| this.animate(other, procedure))
+            .collect::<Result<Vec<_>, _>>()?;
+
+        // Deal with the remainders
+        let this_remainder = if this.len() > result.len() {
+            Some(&this[result.len()..])
+        } else {
+            None
+        };
+        let other_remainder = if other.len() > result.len() {
+            Some(&other[result.len()..])
+        } else {
+            None
+        };
+
+        match (this_remainder, other_remainder) {
+            // If there is a remainder from *both* lists we must have had mismatched functions.
+            // => Add the remainders to a suitable ___Matrix function.
+            (Some(this_remainder), Some(other_remainder)) => {
+                result.push(TransformOperation::animate_mismatched_transforms(
+                    this_remainder,
+                    other_remainder,
+                    procedure,
+                )?);
+            },
+            // If there is a remainder from just one list, then one list must be shorter but
+            // completely match the type of the corresponding functions in the longer list.
+            // => Interpolate the remainder with identity transforms.
+            (Some(remainder), None) | (None, Some(remainder)) => {
+                let fill_right = this_remainder.is_some();
+                result.append(
+                    &mut remainder
+                        .iter()
+                        .map(|transform| {
+                            let identity = transform.to_animated_zero().unwrap();
+
+                            match transform {
+                                TransformOperation::AccumulateMatrix { .. } |
+                                TransformOperation::InterpolateMatrix { .. } => {
+                                    let (from, to) = if fill_right {
+                                        (transform, &identity)
+                                    } else {
+                                        (&identity, transform)
+                                    };
+
+                                    TransformOperation::animate_mismatched_transforms(
+                                        &[from.clone()],
+                                        &[to.clone()],
+                                        procedure,
+                                    )
+                                },
+                                _ => {
+                                    let (lhs, rhs) = if fill_right {
+                                        (transform, &identity)
+                                    } else {
+                                        (&identity, transform)
+                                    };
+                                    lhs.animate(rhs, procedure)
+                                },
+                            }
+                        })
+                        .collect::<Result<Vec<_>, _>>()?,
+                );
+            },
+            (None, None) => {},
+        }
+
+        Ok(Transform(result.into()))
+    }
+}
+
+impl ComputeSquaredDistance for ComputedTransform {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let squared_dist = self.0.squared_distance_with_zero(&other.0);
+
+        // Roll back to matrix interpolation if there is any Err(()) in the
+        // transform lists, such as mismatched transform functions.
+        //
+        // FIXME: Using a zero size here seems a bit sketchy but matches the
+        // previous behavior.
+        if squared_dist.is_err() {
+            let rect = euclid::Rect::zero();
+            let matrix1: Matrix3D = self.to_transform_3d_matrix(Some(&rect))?.0.into();
+            let matrix2: Matrix3D = other.to_transform_3d_matrix(Some(&rect))?.0.into();
+            return matrix1.compute_squared_distance(&matrix2);
+        }
+
+        squared_dist
+    }
+}
+
+/// <http://dev.w3.org/csswg/css-transforms/#interpolation-of-transforms>
+impl Animate for ComputedTransformOperation {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        match (self, other) {
+            (&TransformOperation::Matrix3D(ref this), &TransformOperation::Matrix3D(ref other)) => {
+                Ok(TransformOperation::Matrix3D(
+                    this.animate(other, procedure)?,
+                ))
+            },
+            (&TransformOperation::Matrix(ref this), &TransformOperation::Matrix(ref other)) => {
+                Ok(TransformOperation::Matrix(this.animate(other, procedure)?))
+            },
+            (
+                &TransformOperation::Skew(ref fx, ref fy),
+                &TransformOperation::Skew(ref tx, ref ty),
+            ) => Ok(TransformOperation::Skew(
+                fx.animate(tx, procedure)?,
+                fy.animate(ty, procedure)?,
+            )),
+            (&TransformOperation::SkewX(ref f), &TransformOperation::SkewX(ref t)) => {
+                Ok(TransformOperation::SkewX(f.animate(t, procedure)?))
+            },
+            (&TransformOperation::SkewY(ref f), &TransformOperation::SkewY(ref t)) => {
+                Ok(TransformOperation::SkewY(f.animate(t, procedure)?))
+            },
+            (
+                &TransformOperation::Translate3D(ref fx, ref fy, ref fz),
+                &TransformOperation::Translate3D(ref tx, ref ty, ref tz),
+            ) => Ok(TransformOperation::Translate3D(
+                fx.animate(tx, procedure)?,
+                fy.animate(ty, procedure)?,
+                fz.animate(tz, procedure)?,
+            )),
+            (
+                &TransformOperation::Translate(ref fx, ref fy),
+                &TransformOperation::Translate(ref tx, ref ty),
+            ) => Ok(TransformOperation::Translate(
+                fx.animate(tx, procedure)?,
+                fy.animate(ty, procedure)?,
+            )),
+            (&TransformOperation::TranslateX(ref f), &TransformOperation::TranslateX(ref t)) => {
+                Ok(TransformOperation::TranslateX(f.animate(t, procedure)?))
+            },
+            (&TransformOperation::TranslateY(ref f), &TransformOperation::TranslateY(ref t)) => {
+                Ok(TransformOperation::TranslateY(f.animate(t, procedure)?))
+            },
+            (&TransformOperation::TranslateZ(ref f), &TransformOperation::TranslateZ(ref t)) => {
+                Ok(TransformOperation::TranslateZ(f.animate(t, procedure)?))
+            },
+            (
+                &TransformOperation::Scale3D(ref fx, ref fy, ref fz),
+                &TransformOperation::Scale3D(ref tx, ref ty, ref tz),
+            ) => Ok(TransformOperation::Scale3D(
+                animate_multiplicative_factor(*fx, *tx, procedure)?,
+                animate_multiplicative_factor(*fy, *ty, procedure)?,
+                animate_multiplicative_factor(*fz, *tz, procedure)?,
+            )),
+            (&TransformOperation::ScaleX(ref f), &TransformOperation::ScaleX(ref t)) => Ok(
+                TransformOperation::ScaleX(animate_multiplicative_factor(*f, *t, procedure)?),
+            ),
+            (&TransformOperation::ScaleY(ref f), &TransformOperation::ScaleY(ref t)) => Ok(
+                TransformOperation::ScaleY(animate_multiplicative_factor(*f, *t, procedure)?),
+            ),
+            (&TransformOperation::ScaleZ(ref f), &TransformOperation::ScaleZ(ref t)) => Ok(
+                TransformOperation::ScaleZ(animate_multiplicative_factor(*f, *t, procedure)?),
+            ),
+            (
+                &TransformOperation::Scale(ref fx, ref fy),
+                &TransformOperation::Scale(ref tx, ref ty),
+            ) => Ok(TransformOperation::Scale(
+                animate_multiplicative_factor(*fx, *tx, procedure)?,
+                animate_multiplicative_factor(*fy, *ty, procedure)?,
+            )),
+            (
+                &TransformOperation::Rotate3D(fx, fy, fz, fa),
+                &TransformOperation::Rotate3D(tx, ty, tz, ta),
+            ) => {
+                let animated = Rotate::Rotate3D(fx, fy, fz, fa)
+                    .animate(&Rotate::Rotate3D(tx, ty, tz, ta), procedure)?;
+                let (fx, fy, fz, fa) = ComputedRotate::resolve(&animated);
+                Ok(TransformOperation::Rotate3D(fx, fy, fz, fa))
+            },
+            (&TransformOperation::RotateX(fa), &TransformOperation::RotateX(ta)) => {
+                Ok(TransformOperation::RotateX(fa.animate(&ta, procedure)?))
+            },
+            (&TransformOperation::RotateY(fa), &TransformOperation::RotateY(ta)) => {
+                Ok(TransformOperation::RotateY(fa.animate(&ta, procedure)?))
+            },
+            (&TransformOperation::RotateZ(fa), &TransformOperation::RotateZ(ta)) => {
+                Ok(TransformOperation::RotateZ(fa.animate(&ta, procedure)?))
+            },
+            (&TransformOperation::Rotate(fa), &TransformOperation::Rotate(ta)) => {
+                Ok(TransformOperation::Rotate(fa.animate(&ta, procedure)?))
+            },
+            (&TransformOperation::Rotate(fa), &TransformOperation::RotateZ(ta)) => {
+                Ok(TransformOperation::Rotate(fa.animate(&ta, procedure)?))
+            },
+            (&TransformOperation::RotateZ(fa), &TransformOperation::Rotate(ta)) => {
+                Ok(TransformOperation::Rotate(fa.animate(&ta, procedure)?))
+            },
+            (
+                &TransformOperation::Perspective(ref fd),
+                &TransformOperation::Perspective(ref td),
+            ) => {
+                use crate::values::computed::CSSPixelLength;
+                use crate::values::generics::transform::create_perspective_matrix;
+
+                // From https://drafts.csswg.org/css-transforms-2/#interpolation-of-transform-functions:
+                //
+                //    The transform functions matrix(), matrix3d() and
+                //    perspective() get converted into 4x4 matrices first and
+                //    interpolated as defined in section Interpolation of
+                //    Matrices afterwards.
+                //
+                let from = create_perspective_matrix(fd.infinity_or(|l| l.px()));
+                let to = create_perspective_matrix(td.infinity_or(|l| l.px()));
+
+                let interpolated = Matrix3D::from(from).animate(&Matrix3D::from(to), procedure)?;
+
+                let decomposed = decompose_3d_matrix(interpolated)?;
+                let perspective_z = decomposed.perspective.2;
+                // Clamp results outside of the -1 to 0 range so that we get perspective
+                // function values between 1 and infinity.
+                let used_value = if perspective_z >= 0. {
+                    transform::PerspectiveFunction::None
+                } else {
+                    transform::PerspectiveFunction::Length(CSSPixelLength::new(
+                        if perspective_z <= -1. {
+                            1.
+                        } else {
+                            -1. / perspective_z
+                        },
+                    ))
+                };
+                Ok(TransformOperation::Perspective(used_value))
+            },
+            _ if self.is_translate() && other.is_translate() => self
+                .to_translate_3d()
+                .animate(&other.to_translate_3d(), procedure),
+            _ if self.is_scale() && other.is_scale() => {
+                self.to_scale_3d().animate(&other.to_scale_3d(), procedure)
+            },
+            _ if self.is_rotate() && other.is_rotate() => self
+                .to_rotate_3d()
+                .animate(&other.to_rotate_3d(), procedure),
+            _ => Err(()),
+        }
+    }
+}
+
+impl ComputedTransformOperation {
+    /// If there are no size dependencies, we try to animate in-place, to avoid
+    /// creating deeply nested Interpolate* operations.
+    fn try_animate_mismatched_transforms_in_place(
+        left: &[Self],
+        right: &[Self],
+        procedure: Procedure,
+    ) -> Result<Self, ()> {
+        let (left, _left_3d) = Transform::components_to_transform_3d_matrix(left, None)?;
+        let (right, _right_3d) = Transform::components_to_transform_3d_matrix(right, None)?;
+        ComputedTransformOperation::Matrix3D(left.into()).animate(
+            &ComputedTransformOperation::Matrix3D(right.into()),
+            procedure,
+        )
+    }
+
+    fn animate_mismatched_transforms(
+        left: &[Self],
+        right: &[Self],
+        procedure: Procedure,
+    ) -> Result<Self, ()> {
+        if let Ok(op) = Self::try_animate_mismatched_transforms_in_place(left, right, procedure) {
+            return Ok(op);
+        }
+        let from_list = Transform(left.to_vec().into());
+        let to_list = Transform(right.to_vec().into());
+        Ok(match procedure {
+            Procedure::Add => {
+                debug_assert!(false, "Addition should've been handled earlier");
+                return Err(());
+            },
+            Procedure::Interpolate { progress } => Self::InterpolateMatrix {
+                from_list,
+                to_list,
+                progress: Percentage(progress as f32),
+            },
+            Procedure::Accumulate { count } => Self::AccumulateMatrix {
+                from_list,
+                to_list,
+                count: cmp::min(count, i32::max_value() as u64) as i32,
+            },
+        })
+    }
+}
+
+// This might not be the most useful definition of distance. It might be better, for example,
+// to trace the distance travelled by a point as its transform is interpolated between the two
+// lists. That, however, proves to be quite complicated so we take a simple approach for now.
+// See https://bugzilla.mozilla.org/show_bug.cgi?id=1318591#c0.
+impl ComputeSquaredDistance for ComputedTransformOperation {
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        match (self, other) {
+            (&TransformOperation::Matrix3D(ref this), &TransformOperation::Matrix3D(ref other)) => {
+                this.compute_squared_distance(other)
+            },
+            (&TransformOperation::Matrix(ref this), &TransformOperation::Matrix(ref other)) => {
+                let this: Matrix3D = (*this).into();
+                let other: Matrix3D = (*other).into();
+                this.compute_squared_distance(&other)
+            },
+            (
+                &TransformOperation::Skew(ref fx, ref fy),
+                &TransformOperation::Skew(ref tx, ref ty),
+            ) => Ok(fx.compute_squared_distance(&tx)? + fy.compute_squared_distance(&ty)?),
+            (&TransformOperation::SkewX(ref f), &TransformOperation::SkewX(ref t)) |
+            (&TransformOperation::SkewY(ref f), &TransformOperation::SkewY(ref t)) => {
+                f.compute_squared_distance(&t)
+            },
+            (
+                &TransformOperation::Translate3D(ref fx, ref fy, ref fz),
+                &TransformOperation::Translate3D(ref tx, ref ty, ref tz),
+            ) => {
+                // For translate, We don't want to require doing layout in order
+                // to calculate the result, so drop the percentage part.
+                //
+                // However, dropping percentage makes us impossible to compute
+                // the distance for the percentage-percentage case, but Gecko
+                // uses the same formula, so it's fine for now.
+                let basis = Length::new(0.);
+                let fx = fx.resolve(basis).px();
+                let fy = fy.resolve(basis).px();
+                let tx = tx.resolve(basis).px();
+                let ty = ty.resolve(basis).px();
+
+                Ok(fx.compute_squared_distance(&tx)? +
+                    fy.compute_squared_distance(&ty)? +
+                    fz.compute_squared_distance(&tz)?)
+            },
+            (
+                &TransformOperation::Scale3D(ref fx, ref fy, ref fz),
+                &TransformOperation::Scale3D(ref tx, ref ty, ref tz),
+            ) => Ok(fx.compute_squared_distance(&tx)? +
+                fy.compute_squared_distance(&ty)? +
+                fz.compute_squared_distance(&tz)?),
+            (
+                &TransformOperation::Rotate3D(fx, fy, fz, fa),
+                &TransformOperation::Rotate3D(tx, ty, tz, ta),
+            ) => Rotate::Rotate3D(fx, fy, fz, fa)
+                .compute_squared_distance(&Rotate::Rotate3D(tx, ty, tz, ta)),
+            (&TransformOperation::RotateX(fa), &TransformOperation::RotateX(ta)) |
+            (&TransformOperation::RotateY(fa), &TransformOperation::RotateY(ta)) |
+            (&TransformOperation::RotateZ(fa), &TransformOperation::RotateZ(ta)) |
+            (&TransformOperation::Rotate(fa), &TransformOperation::Rotate(ta)) => {
+                fa.compute_squared_distance(&ta)
+            },
+            (
+                &TransformOperation::Perspective(ref fd),
+                &TransformOperation::Perspective(ref td),
+            ) => fd
+                .infinity_or(|l| l.px())
+                .compute_squared_distance(&td.infinity_or(|l| l.px())),
+            (&TransformOperation::Perspective(ref p), &TransformOperation::Matrix3D(ref m)) |
+            (&TransformOperation::Matrix3D(ref m), &TransformOperation::Perspective(ref p)) => {
+                // FIXME(emilio): Is this right? Why interpolating this with
+                // Perspective but not with anything else?
+                let mut p_matrix = Matrix3D::identity();
+                let p = p.infinity_or(|p| p.px());
+                if p >= 0. {
+                    p_matrix.m34 = -1. / p.max(1.);
+                }
+                p_matrix.compute_squared_distance(&m)
+            },
+            // Gecko cross-interpolates amongst all translate and all scale
+            // functions (See ToPrimitive in layout/style/StyleAnimationValue.cpp)
+            // without falling back to InterpolateMatrix
+            _ if self.is_translate() && other.is_translate() => self
+                .to_translate_3d()
+                .compute_squared_distance(&other.to_translate_3d()),
+            _ if self.is_scale() && other.is_scale() => self
+                .to_scale_3d()
+                .compute_squared_distance(&other.to_scale_3d()),
+            _ if self.is_rotate() && other.is_rotate() => self
+                .to_rotate_3d()
+                .compute_squared_distance(&other.to_rotate_3d()),
+            _ => Err(()),
+        }
+    }
+}
+
+// ------------------------------------
+// Individual transforms.
+// ------------------------------------
+/// <https://drafts.csswg.org/css-transforms-2/#propdef-rotate>
+impl ComputedRotate {
+    fn resolve(&self) -> (Number, Number, Number, Angle) {
+        // According to the spec:
+        // https://drafts.csswg.org/css-transforms-2/#individual-transforms
+        //
+        // If the axis is unspecified, it defaults to "0 0 1"
+        match *self {
+            Rotate::None => (0., 0., 1., Angle::zero()),
+            Rotate::Rotate3D(rx, ry, rz, angle) => (rx, ry, rz, angle),
+            Rotate::Rotate(angle) => (0., 0., 1., angle),
+        }
+    }
+}
+
+impl Animate for ComputedRotate {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        match (self, other) {
+            (&Rotate::None, &Rotate::None) => Ok(Rotate::None),
+            (&Rotate::Rotate3D(fx, fy, fz, fa), &Rotate::None) => {
+                // We always normalize direction vector for rotate3d() first, so we should also
+                // apply the same rule for rotate property. In other words, we promote none into
+                // a 3d rotate, and normalize both direction vector first, and then do
+                // interpolation.
+                let (fx, fy, fz, fa) = transform::get_normalized_vector_and_angle(fx, fy, fz, fa);
+                Ok(Rotate::Rotate3D(
+                    fx,
+                    fy,
+                    fz,
+                    fa.animate(&Angle::zero(), procedure)?,
+                ))
+            },
+            (&Rotate::None, &Rotate::Rotate3D(tx, ty, tz, ta)) => {
+                // Normalize direction vector first.
+                let (tx, ty, tz, ta) = transform::get_normalized_vector_and_angle(tx, ty, tz, ta);
+                Ok(Rotate::Rotate3D(
+                    tx,
+                    ty,
+                    tz,
+                    Angle::zero().animate(&ta, procedure)?,
+                ))
+            },
+            (&Rotate::Rotate3D(_, ..), _) | (_, &Rotate::Rotate3D(_, ..)) => {
+                let (from, to) = (self.resolve(), other.resolve());
+                let (mut fx, mut fy, mut fz, fa) =
+                    transform::get_normalized_vector_and_angle(from.0, from.1, from.2, from.3);
+                let (mut tx, mut ty, mut tz, ta) =
+                    transform::get_normalized_vector_and_angle(to.0, to.1, to.2, to.3);
+
+                if fa == Angle::from_degrees(0.) {
+                    fx = tx;
+                    fy = ty;
+                    fz = tz;
+                } else if ta == Angle::from_degrees(0.) {
+                    tx = fx;
+                    ty = fy;
+                    tz = fz;
+                }
+
+                if (fx, fy, fz) == (tx, ty, tz) {
+                    return Ok(Rotate::Rotate3D(fx, fy, fz, fa.animate(&ta, procedure)?));
+                }
+
+                let fv = DirectionVector::new(fx, fy, fz);
+                let tv = DirectionVector::new(tx, ty, tz);
+                let fq = Quaternion::from_direction_and_angle(&fv, fa.radians64());
+                let tq = Quaternion::from_direction_and_angle(&tv, ta.radians64());
+
+                let rq = Quaternion::animate(&fq, &tq, procedure)?;
+                let (x, y, z, angle) = transform::get_normalized_vector_and_angle(
+                    rq.0 as f32,
+                    rq.1 as f32,
+                    rq.2 as f32,
+                    rq.3.acos() as f32 * 2.0,
+                );
+
+                Ok(Rotate::Rotate3D(x, y, z, Angle::from_radians(angle)))
+            },
+            (&Rotate::Rotate(_), _) | (_, &Rotate::Rotate(_)) => {
+                // If this is a 2D rotation, we just animate the <angle>
+                let (from, to) = (self.resolve().3, other.resolve().3);
+                Ok(Rotate::Rotate(from.animate(&to, procedure)?))
+            },
+        }
+    }
+}
+
+impl ComputeSquaredDistance for ComputedRotate {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        match (self, other) {
+            (&Rotate::None, &Rotate::None) => Ok(SquaredDistance::from_sqrt(0.)),
+            (&Rotate::Rotate3D(_, _, _, a), &Rotate::None) |
+            (&Rotate::None, &Rotate::Rotate3D(_, _, _, a)) => {
+                a.compute_squared_distance(&Angle::zero())
+            },
+            (&Rotate::Rotate3D(_, ..), _) | (_, &Rotate::Rotate3D(_, ..)) => {
+                let (from, to) = (self.resolve(), other.resolve());
+                let (mut fx, mut fy, mut fz, angle1) =
+                    transform::get_normalized_vector_and_angle(from.0, from.1, from.2, from.3);
+                let (mut tx, mut ty, mut tz, angle2) =
+                    transform::get_normalized_vector_and_angle(to.0, to.1, to.2, to.3);
+
+                if angle1 == Angle::zero() {
+                    fx = tx;
+                    fy = ty;
+                    fz = tz;
+                } else if angle2 == Angle::zero() {
+                    tx = fx;
+                    ty = fy;
+                    tz = fz;
+                }
+
+                if (fx, fy, fz) == (tx, ty, tz) {
+                    angle1.compute_squared_distance(&angle2)
+                } else {
+                    let v1 = DirectionVector::new(fx, fy, fz);
+                    let v2 = DirectionVector::new(tx, ty, tz);
+                    let q1 = Quaternion::from_direction_and_angle(&v1, angle1.radians64());
+                    let q2 = Quaternion::from_direction_and_angle(&v2, angle2.radians64());
+                    q1.compute_squared_distance(&q2)
+                }
+            },
+            (&Rotate::Rotate(_), _) | (_, &Rotate::Rotate(_)) => self
+                .resolve()
+                .3
+                .compute_squared_distance(&other.resolve().3),
+        }
+    }
+}
+
+/// <https://drafts.csswg.org/css-transforms-2/#propdef-translate>
+impl ComputedTranslate {
+    fn resolve(&self) -> (LengthPercentage, LengthPercentage, Length) {
+        // According to the spec:
+        // https://drafts.csswg.org/css-transforms-2/#individual-transforms
+        //
+        // Unspecified translations default to 0px
+        match *self {
+            Translate::None => (
+                LengthPercentage::zero(),
+                LengthPercentage::zero(),
+                Length::zero(),
+            ),
+            Translate::Translate(ref tx, ref ty, ref tz) => (tx.clone(), ty.clone(), tz.clone()),
+        }
+    }
+}
+
+impl Animate for ComputedTranslate {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        match (self, other) {
+            (&Translate::None, &Translate::None) => Ok(Translate::None),
+            (&Translate::Translate(_, ..), _) | (_, &Translate::Translate(_, ..)) => {
+                let (from, to) = (self.resolve(), other.resolve());
+                Ok(Translate::Translate(
+                    from.0.animate(&to.0, procedure)?,
+                    from.1.animate(&to.1, procedure)?,
+                    from.2.animate(&to.2, procedure)?,
+                ))
+            },
+        }
+    }
+}
+
+impl ComputeSquaredDistance for ComputedTranslate {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let (from, to) = (self.resolve(), other.resolve());
+        Ok(from.0.compute_squared_distance(&to.0)? +
+            from.1.compute_squared_distance(&to.1)? +
+            from.2.compute_squared_distance(&to.2)?)
+    }
+}
+
+/// <https://drafts.csswg.org/css-transforms-2/#propdef-scale>
+impl ComputedScale {
+    fn resolve(&self) -> (Number, Number, Number) {
+        // According to the spec:
+        // https://drafts.csswg.org/css-transforms-2/#individual-transforms
+        //
+        // Unspecified scales default to 1
+        match *self {
+            Scale::None => (1.0, 1.0, 1.0),
+            Scale::Scale(sx, sy, sz) => (sx, sy, sz),
+        }
+    }
+}
+
+impl Animate for ComputedScale {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        match (self, other) {
+            (&Scale::None, &Scale::None) => Ok(Scale::None),
+            (&Scale::Scale(_, ..), _) | (_, &Scale::Scale(_, ..)) => {
+                let (from, to) = (self.resolve(), other.resolve());
+                // For transform lists, we add by appending to the list of
+                // transform functions. However, ComputedScale cannot be
+                // simply concatenated, so we have to calculate the additive
+                // result here.
+                if procedure == Procedure::Add {
+                    // scale(x1,y1,z1)*scale(x2,y2,z2) = scale(x1*x2, y1*y2, z1*z2)
+                    return Ok(Scale::Scale(from.0 * to.0, from.1 * to.1, from.2 * to.2));
+                }
+                Ok(Scale::Scale(
+                    animate_multiplicative_factor(from.0, to.0, procedure)?,
+                    animate_multiplicative_factor(from.1, to.1, procedure)?,
+                    animate_multiplicative_factor(from.2, to.2, procedure)?,
+                ))
+            },
+        }
+    }
+}
+
+impl ComputeSquaredDistance for ComputedScale {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        let (from, to) = (self.resolve(), other.resolve());
+        Ok(from.0.compute_squared_distance(&to.0)? +
+            from.1.compute_squared_distance(&to.1)? +
+            from.2.compute_squared_distance(&to.2)?)
+    }
+}
diff --git a/servo/components/style/values/computed/align.rs b/servo/components/style/values/computed/align.rs
new file mode 100644
index 0000000000..94847fd80f
--- /dev/null
+++ b/servo/components/style/values/computed/align.rs
@@ -0,0 +1,91 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Values for CSS Box Alignment properties
+//!
+//! https://drafts.csswg.org/css-align/
+
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::specified;
+
+pub use super::specified::{
+    AlignContent, AlignItems, AlignTracks, ContentDistribution, JustifyContent, JustifyTracks,
+    SelfAlignment,
+};
+pub use super::specified::{AlignSelf, JustifySelf};
+
+/// The computed value for the `justify-items` property.
+///
+/// Need to carry around both the specified and computed value to handle the
+/// special legacy keyword without destroying style sharing.
+///
+/// In particular, `justify-items` is a reset property, so we ought to be able
+/// to share its computed representation across elements as long as they match
+/// the same rules. Except that it's not true if the specified value for
+/// `justify-items` is `legacy` and the computed value of the parent has the
+/// `legacy` modifier.
+///
+/// So instead of computing `legacy` "normally" looking at get_parent_position(),
+/// marking it as uncacheable, we carry the specified value around and handle
+/// the special case in `StyleAdjuster` instead, only when the result of the
+/// computation would vary.
+///
+/// Note that we also need to special-case this property in matching.rs, in
+/// order to properly handle changes to the legacy keyword... This all kinda
+/// sucks :(.
+///
+/// See the discussion in https://bugzil.la/1384542.
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToCss, ToResolvedValue)]
+#[repr(C)]
+pub struct ComputedJustifyItems {
+    /// The specified value for the property. Can contain the bare `legacy`
+    /// keyword.
+    #[css(skip)]
+    pub specified: specified::JustifyItems,
+    /// The computed value for the property. Cannot contain the bare `legacy`
+    /// keyword, but note that it could contain it in combination with other
+    /// keywords like `left`, `right` or `center`.
+    pub computed: specified::JustifyItems,
+}
+
+pub use self::ComputedJustifyItems as JustifyItems;
+
+impl JustifyItems {
+    /// Returns the `legacy` value.
+    pub fn legacy() -> Self {
+        Self {
+            specified: specified::JustifyItems::legacy(),
+            computed: specified::JustifyItems::normal(),
+        }
+    }
+}
+
+impl ToComputedValue for specified::JustifyItems {
+    type ComputedValue = JustifyItems;
+
+    /// <https://drafts.csswg.org/css-align/#valdef-justify-items-legacy>
+    fn to_computed_value(&self, _context: &Context) -> JustifyItems {
+        use crate::values::specified::align;
+        let specified = *self;
+        let computed = if self.0 != align::AlignFlags::LEGACY {
+            *self
+        } else {
+            // If the inherited value of `justify-items` includes the
+            // `legacy` keyword, `legacy` computes to the inherited value, but
+            // we assume it computes to `normal`, and handle that special-case
+            // in StyleAdjuster.
+            Self::normal()
+        };
+
+        JustifyItems {
+            specified,
+            computed,
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &JustifyItems) -> Self {
+        computed.specified
+    }
+}
diff --git a/servo/components/style/values/computed/angle.rs b/servo/components/style/values/computed/angle.rs
new file mode 100644
index 0000000000..ea321d2233
--- /dev/null
+++ b/servo/components/style/values/computed/angle.rs
@@ -0,0 +1,101 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed angles.
+
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::CSSFloat;
+use crate::Zero;
+use std::f64::consts::PI;
+use std::fmt::{self, Write};
+use std::{f32, f64};
+use style_traits::{CssWriter, ToCss};
+
+/// A computed angle in degrees.
+#[derive(
+    Add,
+    Animate,
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    Serialize,
+    ToAnimatedZero,
+    ToResolvedValue,
+)]
+#[repr(C)]
+pub struct Angle(CSSFloat);
+
+impl ToCss for Angle {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.degrees().to_css(dest)?;
+        dest.write_str("deg")
+    }
+}
+
+const RAD_PER_DEG: f64 = PI / 180.0;
+
+impl Angle {
+    /// Creates a computed `Angle` value from a radian amount.
+    pub fn from_radians(radians: CSSFloat) -> Self {
+        Angle(radians / RAD_PER_DEG as f32)
+    }
+
+    /// Creates a computed `Angle` value from a degrees amount.
+    #[inline]
+    pub fn from_degrees(degrees: CSSFloat) -> Self {
+        Angle(degrees)
+    }
+
+    /// Returns the amount of radians this angle represents.
+    #[inline]
+    pub fn radians(&self) -> CSSFloat {
+        self.radians64().min(f32::MAX as f64).max(f32::MIN as f64) as f32
+    }
+
+    /// Returns the amount of radians this angle represents as a `f64`.
+    ///
+    /// Gecko stores angles as singles, but does this computation using doubles.
+    ///
+    /// This is significant enough to mess up rounding to the nearest
+    /// quarter-turn for 225 degrees, for example.
+    #[inline]
+    pub fn radians64(&self) -> f64 {
+        self.0 as f64 * RAD_PER_DEG
+    }
+
+    /// Return the value in degrees.
+    #[inline]
+    pub fn degrees(&self) -> CSSFloat {
+        self.0
+    }
+}
+
+impl Zero for Angle {
+    #[inline]
+    fn zero() -> Self {
+        Angle(0.0)
+    }
+
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.0 == 0.
+    }
+}
+
+impl ComputeSquaredDistance for Angle {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        // Use the formula for calculating the distance between angles defined in SVG:
+        // https://www.w3.org/TR/SVG/animate.html#complexDistances
+        self.radians64()
+            .compute_squared_distance(&other.radians64())
+    }
+}
diff --git a/servo/components/style/values/computed/background.rs b/servo/components/style/values/computed/background.rs
new file mode 100644
index 0000000000..e2a58f8b74
--- /dev/null
+++ b/servo/components/style/values/computed/background.rs
@@ -0,0 +1,13 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS values related to backgrounds.
+
+use crate::values::computed::length::NonNegativeLengthPercentage;
+use crate::values::generics::background::BackgroundSize as GenericBackgroundSize;
+
+pub use crate::values::specified::background::BackgroundRepeat;
+
+/// A computed value for the `background-size` property.
+pub type BackgroundSize = GenericBackgroundSize<NonNegativeLengthPercentage>;
diff --git a/servo/components/style/values/computed/basic_shape.rs b/servo/components/style/values/computed/basic_shape.rs
new file mode 100644
index 0000000000..fa30220157
--- /dev/null
+++ b/servo/components/style/values/computed/basic_shape.rs
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the computed value of
+//! [`basic-shape`][basic-shape]s
+//!
+//! [basic-shape]: https://drafts.csswg.org/css-shapes/#typedef-basic-shape
+
+use crate::values::computed::url::ComputedUrl;
+use crate::values::computed::{Image, LengthPercentage, NonNegativeLengthPercentage};
+use crate::values::generics::basic_shape as generic;
+
+/// A computed alias for FillRule.
+pub use crate::values::generics::basic_shape::FillRule;
+
+/// A computed `clip-path` value.
+pub type ClipPath = generic::GenericClipPath<BasicShape, ComputedUrl>;
+
+/// A computed `shape-outside` value.
+pub type ShapeOutside = generic::GenericShapeOutside<BasicShape, Image>;
+
+/// A computed basic shape.
+pub type BasicShape = generic::GenericBasicShape<
+    LengthPercentage,
+    LengthPercentage,
+    LengthPercentage,
+    NonNegativeLengthPercentage,
+>;
+
+/// The computed value of `inset()`
+pub type InsetRect = generic::InsetRect<LengthPercentage, NonNegativeLengthPercentage>;
+
+/// A computed circle.
+pub type Circle = generic::Circle<LengthPercentage, LengthPercentage, NonNegativeLengthPercentage>;
+
+/// A computed ellipse.
+pub type Ellipse =
+    generic::Ellipse<LengthPercentage, LengthPercentage, NonNegativeLengthPercentage>;
+
+/// The computed value of `ShapeRadius`
+pub type ShapeRadius = generic::GenericShapeRadius<NonNegativeLengthPercentage>;
diff --git a/servo/components/style/values/computed/border.rs b/servo/components/style/values/computed/border.rs
new file mode 100644
index 0000000000..abdc28ad84
--- /dev/null
+++ b/servo/components/style/values/computed/border.rs
@@ -0,0 +1,78 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS values related to borders.
+
+use crate::values::computed::length::{NonNegativeLength, NonNegativeLengthPercentage};
+use crate::values::computed::{NonNegativeNumber, NonNegativeNumberOrPercentage};
+use crate::values::generics::border::BorderCornerRadius as GenericBorderCornerRadius;
+use crate::values::generics::border::BorderImageSlice as GenericBorderImageSlice;
+use crate::values::generics::border::BorderRadius as GenericBorderRadius;
+use crate::values::generics::border::BorderSpacing as GenericBorderSpacing;
+use crate::values::generics::border::GenericBorderImageSideWidth;
+use crate::values::generics::rect::Rect;
+use crate::values::generics::size::Size2D;
+use crate::values::generics::NonNegative;
+use crate::Zero;
+use app_units::Au;
+
+pub use crate::values::specified::border::BorderImageRepeat;
+
+/// A computed value for the `border-image-width` property.
+pub type BorderImageWidth = Rect<BorderImageSideWidth>;
+
+/// A computed value for a single side of a `border-image-width` property.
+pub type BorderImageSideWidth =
+    GenericBorderImageSideWidth<NonNegativeLengthPercentage, NonNegativeNumber>;
+
+/// A computed value for the `border-image-slice` property.
+pub type BorderImageSlice = GenericBorderImageSlice<NonNegativeNumberOrPercentage>;
+
+/// A computed value for the `border-radius` property.
+pub type BorderRadius = GenericBorderRadius<NonNegativeLengthPercentage>;
+
+/// A computed value for the `border-*-radius` longhand properties.
+pub type BorderCornerRadius = GenericBorderCornerRadius<NonNegativeLengthPercentage>;
+
+/// A computed value for the `border-spacing` longhand property.
+pub type BorderSpacing = GenericBorderSpacing<NonNegativeLength>;
+
+impl BorderImageSideWidth {
+    /// Returns `1`.
+    #[inline]
+    pub fn one() -> Self {
+        GenericBorderImageSideWidth::Number(NonNegative(1.))
+    }
+}
+
+impl BorderImageSlice {
+    /// Returns the `100%` value.
+    #[inline]
+    pub fn hundred_percent() -> Self {
+        GenericBorderImageSlice {
+            offsets: Rect::all(NonNegativeNumberOrPercentage::hundred_percent()),
+            fill: false,
+        }
+    }
+}
+
+impl BorderSpacing {
+    /// Returns `0 0`.
+    pub fn zero() -> Self {
+        GenericBorderSpacing(Size2D::new(
+            NonNegativeLength::zero(),
+            NonNegativeLength::zero(),
+        ))
+    }
+
+    /// Returns the horizontal spacing.
+    pub fn horizontal(&self) -> Au {
+        Au::from(*self.0.width())
+    }
+
+    /// Returns the vertical spacing.
+    pub fn vertical(&self) -> Au {
+        Au::from(*self.0.height())
+    }
+}
diff --git a/servo/components/style/values/computed/box.rs b/servo/components/style/values/computed/box.rs
new file mode 100644
index 0000000000..a390d69a02
--- /dev/null
+++ b/servo/components/style/values/computed/box.rs
@@ -0,0 +1,268 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for box properties.
+
+use crate::values::animated::{Animate, Procedure};
+use crate::values::computed::length::{LengthPercentage, NonNegativeLength};
+use crate::values::computed::{Context, Integer, Number, ToComputedValue};
+use crate::values::generics::box_::AnimationIterationCount as GenericAnimationIterationCount;
+use crate::values::generics::box_::{
+    GenericContainIntrinsicSize, GenericLineClamp, GenericPerspective, GenericVerticalAlign,
+};
+use crate::values::specified::box_ as specified;
+
+pub use crate::values::specified::box_::{
+    AnimationName, AnimationTimeline, Appearance, BreakBetween, BreakWithin,
+    Clear as SpecifiedClear, Contain, ContainerName, ContainerType, ContentVisibility, Display,
+    Float as SpecifiedFloat, Overflow, OverflowAnchor, OverflowClipBox, OverscrollBehavior,
+    ScrollAxis, ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStop, ScrollSnapStrictness,
+    ScrollSnapType, ScrollTimelineName, ScrollbarGutter, TouchAction, TransitionProperty,
+    WillChange,
+};
+
+/// A computed value for the `vertical-align` property.
+pub type VerticalAlign = GenericVerticalAlign<LengthPercentage>;
+
+/// A computed value for the `animation-iteration-count` property.
+pub type AnimationIterationCount = GenericAnimationIterationCount<Number>;
+
+/// A computed value for the `contain-intrinsic-size` property.
+pub type ContainIntrinsicSize = GenericContainIntrinsicSize<NonNegativeLength>;
+
+/// A computed value for the `line-clamp` property.
+pub type LineClamp = GenericLineClamp<Integer>;
+
+impl Animate for LineClamp {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        if self.is_none() != other.is_none() {
+            return Err(());
+        }
+        if self.is_none() {
+            return Ok(Self::none());
+        }
+        Ok(Self(self.0.animate(&other.0, procedure)?.max(1)))
+    }
+}
+
+impl AnimationIterationCount {
+    /// Returns the value `1.0`.
+    #[inline]
+    pub fn one() -> Self {
+        GenericAnimationIterationCount::Number(1.0)
+    }
+}
+
+/// A computed value for the `perspective` property.
+pub type Perspective = GenericPerspective<NonNegativeLength>;
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToResolvedValue,
+)]
+#[repr(u8)]
+/// A computed value for the `float` property.
+pub enum Float {
+    Left,
+    Right,
+    None,
+}
+
+impl Float {
+    /// Returns true if `self` is not `None`.
+    pub fn is_floating(self) -> bool {
+        self != Self::None
+    }
+}
+
+impl ToComputedValue for SpecifiedFloat {
+    type ComputedValue = Float;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        let ltr = context.style().writing_mode.is_bidi_ltr();
+        // https://drafts.csswg.org/css-logical-props/#float-clear
+        match *self {
+            SpecifiedFloat::InlineStart => {
+                context
+                    .rule_cache_conditions
+                    .borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Float::Left
+                } else {
+                    Float::Right
+                }
+            },
+            SpecifiedFloat::InlineEnd => {
+                context
+                    .rule_cache_conditions
+                    .borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Float::Right
+                } else {
+                    Float::Left
+                }
+            },
+            SpecifiedFloat::Left => Float::Left,
+            SpecifiedFloat::Right => Float::Right,
+            SpecifiedFloat::None => Float::None,
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> SpecifiedFloat {
+        match *computed {
+            Float::Left => SpecifiedFloat::Left,
+            Float::Right => SpecifiedFloat::Right,
+            Float::None => SpecifiedFloat::None,
+        }
+    }
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToResolvedValue,
+)]
+/// A computed value for the `clear` property.
+#[repr(u8)]
+pub enum Clear {
+    None,
+    Left,
+    Right,
+    Both,
+}
+
+impl ToComputedValue for SpecifiedClear {
+    type ComputedValue = Clear;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        let ltr = context.style().writing_mode.is_bidi_ltr();
+        // https://drafts.csswg.org/css-logical-props/#float-clear
+        match *self {
+            SpecifiedClear::InlineStart => {
+                context
+                    .rule_cache_conditions
+                    .borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Clear::Left
+                } else {
+                    Clear::Right
+                }
+            },
+            SpecifiedClear::InlineEnd => {
+                context
+                    .rule_cache_conditions
+                    .borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if ltr {
+                    Clear::Right
+                } else {
+                    Clear::Left
+                }
+            },
+            SpecifiedClear::None => Clear::None,
+            SpecifiedClear::Left => Clear::Left,
+            SpecifiedClear::Right => Clear::Right,
+            SpecifiedClear::Both => Clear::Both,
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> SpecifiedClear {
+        match *computed {
+            Clear::None => SpecifiedClear::None,
+            Clear::Left => SpecifiedClear::Left,
+            Clear::Right => SpecifiedClear::Right,
+            Clear::Both => SpecifiedClear::Both,
+        }
+    }
+}
+
+/// A computed value for the `resize` property.
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq, ToCss, ToResolvedValue)]
+#[repr(u8)]
+pub enum Resize {
+    None,
+    Both,
+    Horizontal,
+    Vertical,
+}
+
+impl ToComputedValue for specified::Resize {
+    type ComputedValue = Resize;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Resize {
+        let is_vertical = context.style().writing_mode.is_vertical();
+        match self {
+            specified::Resize::Inline => {
+                context
+                    .rule_cache_conditions
+                    .borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if is_vertical {
+                    Resize::Vertical
+                } else {
+                    Resize::Horizontal
+                }
+            },
+            specified::Resize::Block => {
+                context
+                    .rule_cache_conditions
+                    .borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if is_vertical {
+                    Resize::Horizontal
+                } else {
+                    Resize::Vertical
+                }
+            },
+            specified::Resize::None => Resize::None,
+            specified::Resize::Both => Resize::Both,
+            specified::Resize::Horizontal => Resize::Horizontal,
+            specified::Resize::Vertical => Resize::Vertical,
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Resize) -> specified::Resize {
+        match computed {
+            Resize::None => specified::Resize::None,
+            Resize::Both => specified::Resize::Both,
+            Resize::Horizontal => specified::Resize::Horizontal,
+            Resize::Vertical => specified::Resize::Vertical,
+        }
+    }
+}
diff --git a/servo/components/style/values/computed/color.rs b/servo/components/style/values/computed/color.rs
new file mode 100644
index 0000000000..dd15ec41d3
--- /dev/null
+++ b/servo/components/style/values/computed/color.rs
@@ -0,0 +1,87 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed color values.
+
+use crate::values::animated::color::AnimatedRGBA;
+use crate::values::animated::ToAnimatedValue;
+use crate::values::computed::percentage::Percentage;
+use crate::values::generics::color::{GenericCaretColor, GenericColor, GenericColorOrAuto};
+use cssparser::{Color as CSSParserColor, RGBA};
+use std::fmt;
+use style_traits::{CssWriter, ToCss};
+
+pub use crate::values::specified::color::{ColorScheme, PrintColorAdjust};
+
+/// The computed value of the `color` property.
+pub type ColorPropertyValue = RGBA;
+
+/// The computed value of `-moz-font-smoothing-background-color`.
+pub type MozFontSmoothingBackgroundColor = RGBA;
+
+/// A computed value for `<color>`.
+pub type Color = GenericColor<RGBA, Percentage>;
+
+impl ToCss for Color {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        match *self {
+            Self::Numeric(ref c) => c.to_css(dest),
+            Self::CurrentColor => CSSParserColor::CurrentColor.to_css(dest),
+            Self::ColorMix(ref m) => m.to_css(dest),
+        }
+    }
+}
+
+impl Color {
+    /// Returns a complex color value representing transparent.
+    pub fn transparent() -> Color {
+        Color::rgba(RGBA::transparent())
+    }
+
+    /// Returns opaque black.
+    pub fn black() -> Color {
+        Color::rgba(RGBA::new(0, 0, 0, 255))
+    }
+
+    /// Returns opaque white.
+    pub fn white() -> Color {
+        Color::rgba(RGBA::new(255, 255, 255, 255))
+    }
+
+    /// Combine this complex color with the given foreground color into
+    /// a numeric RGBA color.
+    pub fn into_rgba(mut self, current_color: RGBA) -> RGBA {
+        self.simplify(Some(&current_color));
+        *self.as_numeric().unwrap()
+    }
+}
+
+impl ToAnimatedValue for RGBA {
+    type AnimatedValue = AnimatedRGBA;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        AnimatedRGBA::new(
+            self.red_f32(),
+            self.green_f32(),
+            self.blue_f32(),
+            self.alpha_f32(),
+        )
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        // RGBA::from_floats clamps each component values.
+        RGBA::from_floats(animated.red, animated.green, animated.blue, animated.alpha)
+    }
+}
+
+/// auto | <color>
+pub type ColorOrAuto = GenericColorOrAuto<Color>;
+
+/// caret-color
+pub type CaretColor = GenericCaretColor<Color>;
diff --git a/servo/components/style/values/computed/column.rs b/servo/components/style/values/computed/column.rs
new file mode 100644
index 0000000000..38437ea110
--- /dev/null
+++ b/servo/components/style/values/computed/column.rs
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for the column properties.
+
+use crate::values::computed::PositiveInteger;
+use crate::values::generics::column::ColumnCount as GenericColumnCount;
+
+/// A computed type for `column-count` values.
+pub type ColumnCount = GenericColumnCount<PositiveInteger>;
diff --git a/servo/components/style/values/computed/counters.rs b/servo/components/style/values/computed/counters.rs
new file mode 100644
index 0000000000..fd5e915c4a
--- /dev/null
+++ b/servo/components/style/values/computed/counters.rs
@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed values for counter properties
+
+use crate::values::computed::image::Image;
+use crate::values::generics::counters as generics;
+use crate::values::generics::counters::CounterIncrement as GenericCounterIncrement;
+use crate::values::generics::counters::CounterReset as GenericCounterReset;
+use crate::values::generics::counters::CounterSet as GenericCounterSet;
+
+/// A computed value for the `counter-increment` property.
+pub type CounterIncrement = GenericCounterIncrement<i32>;
+
+/// A computed value for the `counter-reset` property.
+pub type CounterReset = GenericCounterReset<i32>;
+
+/// A computed value for the `counter-set` property.
+pub type CounterSet = GenericCounterSet<i32>;
+
+/// A computed value for the `content` property.
+pub type Content = generics::GenericContent<Image>;
+
+/// A computed content item.
+pub type ContentItem = generics::GenericContentItem<Image>;
diff --git a/servo/components/style/values/computed/easing.rs b/servo/components/style/values/computed/easing.rs
new file mode 100644
index 0000000000..06916b5001
--- /dev/null
+++ b/servo/components/style/values/computed/easing.rs
@@ -0,0 +1,97 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS Easing functions.
+
+use euclid::approxeq::ApproxEq;
+
+use crate::bezier::Bezier;
+use crate::piecewise_linear::PiecewiseLinearFunction;
+use crate::values::computed::{Integer, Number};
+use crate::values::generics::easing::{self, BeforeFlag, StepPosition, TimingKeyword};
+
+/// A computed timing function.
+pub type ComputedTimingFunction = easing::TimingFunction<Integer, Number, PiecewiseLinearFunction>;
+
+/// An alias of the computed timing function.
+pub type TimingFunction = ComputedTimingFunction;
+
+impl ComputedTimingFunction {
+    fn calculate_step_output(
+        steps: i32,
+        pos: StepPosition,
+        progress: f64,
+        before_flag: BeforeFlag,
+    ) -> f64 {
+        // User specified values can cause overflow (bug 1706157). Increments/decrements
+        // should be gravefully handled.
+        let mut current_step = (progress * (steps as f64)).floor() as i32;
+
+        // Increment current step if it is jump-start or start.
+        if pos == StepPosition::Start ||
+            pos == StepPosition::JumpStart ||
+            pos == StepPosition::JumpBoth
+        {
+            current_step = current_step.checked_add(1).unwrap_or(current_step);
+        }
+
+        // If the "before flag" is set and we are at a transition point,
+        // drop back a step
+        if before_flag == BeforeFlag::Set &&
+            (progress * steps as f64).rem_euclid(1.0).approx_eq(&0.0)
+        {
+            current_step = current_step.checked_sub(1).unwrap_or(current_step);
+        }
+
+        // We should not produce a result outside [0, 1] unless we have an
+        // input outside that range. This takes care of steps that would otherwise
+        // occur at boundaries.
+        if progress >= 0.0 && current_step < 0 {
+            current_step = 0;
+        }
+
+        // |jumps| should always be in [1, i32::MAX].
+        let jumps = if pos == StepPosition::JumpBoth {
+            steps.checked_add(1).unwrap_or(steps)
+        } else if pos == StepPosition::JumpNone {
+            steps.checked_sub(1).unwrap_or(steps)
+        } else {
+            steps
+        };
+
+        if progress <= 1.0 && current_step > jumps {
+            current_step = jumps;
+        }
+
+        (current_step as f64) / (jumps as f64)
+    }
+
+    /// The output of the timing function given the progress ratio of this animation.
+    pub fn calculate_output(&self, progress: f64, before_flag: BeforeFlag, epsilon: f64) -> f64 {
+        match self {
+            TimingFunction::CubicBezier { x1, y1, x2, y2 } => {
+                Bezier::calculate_bezier_output(progress, epsilon, *x1, *y1, *x2, *y2)
+            },
+            TimingFunction::Steps(steps, pos) => {
+                Self::calculate_step_output(*steps, *pos, progress, before_flag)
+            },
+            TimingFunction::LinearFunction(function) => function.at(progress as f32).into(),
+            TimingFunction::Keyword(keyword) => match keyword {
+                TimingKeyword::Linear => return progress,
+                TimingKeyword::Ease => {
+                    Bezier::calculate_bezier_output(progress, epsilon, 0.25, 0.1, 0.25, 1.)
+                },
+                TimingKeyword::EaseIn => {
+                    Bezier::calculate_bezier_output(progress, epsilon, 0.42, 0., 1., 1.)
+                },
+                TimingKeyword::EaseOut => {
+                    Bezier::calculate_bezier_output(progress, epsilon, 0., 0., 0.58, 1.)
+                },
+                TimingKeyword::EaseInOut => {
+                    Bezier::calculate_bezier_output(progress, epsilon, 0.42, 0., 0.58, 1.)
+                },
+            },
+        }
+    }
+}
diff --git a/servo/components/style/values/computed/effects.rs b/servo/components/style/values/computed/effects.rs
new file mode 100644
index 0000000000..b0a92024ca
--- /dev/null
+++ b/servo/components/style/values/computed/effects.rs
@@ -0,0 +1,44 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS values related to effects.
+
+use crate::values::computed::color::Color;
+use crate::values::computed::length::{Length, NonNegativeLength};
+#[cfg(feature = "gecko")]
+use crate::values::computed::url::ComputedUrl;
+use crate::values::computed::{Angle, NonNegativeNumber, ZeroToOneNumber};
+use crate::values::generics::effects::BoxShadow as GenericBoxShadow;
+use crate::values::generics::effects::Filter as GenericFilter;
+use crate::values::generics::effects::SimpleShadow as GenericSimpleShadow;
+#[cfg(not(feature = "gecko"))]
+use crate::values::Impossible;
+
+/// A computed value for a single shadow of the `box-shadow` property.
+pub type BoxShadow = GenericBoxShadow<Color, Length, NonNegativeLength, Length>;
+
+/// A computed value for a single `filter`.
+#[cfg(feature = "gecko")]
+pub type Filter = GenericFilter<
+    Angle,
+    NonNegativeNumber,
+    ZeroToOneNumber,
+    NonNegativeLength,
+    SimpleShadow,
+    ComputedUrl,
+>;
+
+/// A computed value for a single `filter`.
+#[cfg(feature = "servo")]
+pub type Filter = GenericFilter<
+    Angle,
+    NonNegativeNumber,
+    ZeroToOneNumber,
+    NonNegativeLength,
+    Impossible,
+    Impossible,
+>;
+
+/// A computed value for the `drop-shadow()` filter.
+pub type SimpleShadow = GenericSimpleShadow<Color, Length, NonNegativeLength>;
diff --git a/servo/components/style/values/computed/flex.rs b/servo/components/style/values/computed/flex.rs
new file mode 100644
index 0000000000..95c497ecf6
--- /dev/null
+++ b/servo/components/style/values/computed/flex.rs
@@ -0,0 +1,19 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS values related to flexbox.
+
+use crate::values::computed::Size;
+use crate::values::generics::flex::FlexBasis as GenericFlexBasis;
+
+/// A computed value for the `flex-basis` property.
+pub type FlexBasis = GenericFlexBasis<Size>;
+
+impl FlexBasis {
+    /// `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        GenericFlexBasis::Size(Size::auto())
+    }
+}
diff --git a/servo/components/style/values/computed/font.rs b/servo/components/style/values/computed/font.rs
new file mode 100644
index 0000000000..c792cd97cf
--- /dev/null
+++ b/servo/components/style/values/computed/font.rs
@@ -0,0 +1,1148 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed values for font properties
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::animated::ToAnimatedValue;
+use crate::values::computed::{
+    Angle, Context, Integer, Length, NonNegativeLength, NonNegativeNumber, Number, Percentage,
+    ToComputedValue,
+};
+use crate::values::generics::font::{FeatureTagValue, FontSettings, VariationValue};
+use crate::values::generics::{font as generics, NonNegative};
+use crate::values::specified::font::{
+    self as specified, KeywordInfo, MAX_FONT_WEIGHT, MIN_FONT_WEIGHT,
+};
+use crate::values::specified::length::{FontBaseSize, NoCalcLength};
+use crate::Atom;
+use cssparser::{serialize_identifier, CssStringWriter, Parser};
+#[cfg(feature = "gecko")]
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ParseError, ToCss};
+
+pub use crate::values::computed::Length as MozScriptMinSize;
+pub use crate::values::specified::font::FontPalette;
+pub use crate::values::specified::font::{FontSynthesis, MozScriptSizeMultiplier};
+pub use crate::values::specified::font::{FontVariantAlternates, FontVariantEastAsian, FontVariantLigatures, FontVariantNumeric, XLang, XTextZoom};
+pub use crate::values::specified::Integer as SpecifiedInteger;
+
+/// Generic template for font property type classes that use a fixed-point
+/// internal representation with `FRACTION_BITS` for the fractional part.
+///
+/// Values are constructed from and exposed as floating-point, but stored
+/// internally as fixed point, so there will be a quantization effect on
+/// fractional values, depending on the number of fractional bits used.
+///
+/// Using (16-bit) fixed-point types rather than floats for these style
+/// attributes reduces the memory footprint of gfxFontEntry and gfxFontStyle; it
+/// will also tend to reduce the number of distinct font instances that get
+/// created, particularly when styles are animated or set to arbitrary values
+/// (e.g. by sliders in the UI), which should reduce pressure on graphics
+/// resources and improve cache hit rates.
+///
+/// cbindgen:derive-lt
+/// cbindgen:derive-lte
+/// cbindgen:derive-gt
+/// cbindgen:derive-gte
+#[repr(C)]
+#[derive(
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    ToResolvedValue,
+)]
+pub struct FixedPoint<T, const FRACTION_BITS: u16> {
+    value: T,
+}
+
+impl<T, const FRACTION_BITS: u16> FixedPoint<T, FRACTION_BITS>
+where
+    T: num_traits::cast::AsPrimitive<f32>,
+    f32: num_traits::cast::AsPrimitive<T>,
+{
+    const SCALE: u16 = 1 << FRACTION_BITS;
+    const INVERSE_SCALE: f32 = 1.0 / Self::SCALE as f32;
+
+    /// Returns a fixed-point bit from a floating-point context.
+    fn from_float(v: f32) -> Self {
+        use num_traits::cast::AsPrimitive;
+        Self {
+            value: (v * Self::SCALE as f32).round().as_(),
+        }
+    }
+
+    /// Returns the floating-point representation.
+    fn to_float(&self) -> f32 {
+        self.value.as_() * Self::INVERSE_SCALE
+    }
+}
+
+/// font-weight: range 1..1000, fractional values permitted; keywords
+/// 'normal', 'bold' aliased to 400, 700 respectively.
+///
+/// We use an unsigned 10.6 fixed-point value (range 0.0 - 1023.984375)
+pub const FONT_WEIGHT_FRACTION_BITS: u16 = 6;
+
+/// This is an alias which is useful mostly as a cbindgen / C++ inference
+/// workaround.
+pub type FontWeightFixedPoint = FixedPoint<u16, FONT_WEIGHT_FRACTION_BITS>;
+
+/// A value for the font-weight property per:
+///
+/// https://drafts.csswg.org/css-fonts-4/#propdef-font-weight
+///
+/// cbindgen:derive-lt
+/// cbindgen:derive-lte
+/// cbindgen:derive-gt
+/// cbindgen:derive-gte
+#[derive(
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    ToResolvedValue,
+)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[repr(C)]
+pub struct FontWeight(FontWeightFixedPoint);
+impl ToAnimatedValue for FontWeight {
+    type AnimatedValue = Number;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.value()
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        FontWeight::from_float(animated)
+    }
+}
+
+impl ToCss for FontWeight {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        self.value().to_css(dest)
+    }
+}
+
+impl FontWeight {
+    /// The `normal` keyword.
+    pub const NORMAL: FontWeight = FontWeight(FontWeightFixedPoint {
+        value: 400 << FONT_WEIGHT_FRACTION_BITS,
+    });
+
+    /// The `bold` value.
+    pub const BOLD: FontWeight = FontWeight(FontWeightFixedPoint {
+        value: 700 << FONT_WEIGHT_FRACTION_BITS,
+    });
+
+    /// The threshold from which we consider a font bold.
+    pub const BOLD_THRESHOLD: FontWeight = FontWeight(FontWeightFixedPoint {
+        value: 600 << FONT_WEIGHT_FRACTION_BITS,
+    });
+
+    /// Returns the `normal` keyword value.
+    pub fn normal() -> Self {
+        Self::NORMAL
+    }
+
+    /// Weither this weight is bold
+    pub fn is_bold(&self) -> bool {
+        *self >= Self::BOLD_THRESHOLD
+    }
+
+    /// Returns the value as a float.
+    pub fn value(&self) -> f32 {
+        self.0.to_float()
+    }
+
+    /// Construct a valid weight from a float value.
+    pub fn from_float(v: f32) -> Self {
+        Self(FixedPoint::from_float(
+            v.max(MIN_FONT_WEIGHT).min(MAX_FONT_WEIGHT),
+        ))
+    }
+
+    /// Return the bolder weight.
+    ///
+    /// See the table in:
+    /// https://drafts.csswg.org/css-fonts-4/#font-weight-numeric-values
+    pub fn bolder(self) -> Self {
+        let value = self.value();
+        if value < 350. {
+            return Self::NORMAL;
+        }
+        if value < 550. {
+            return Self::BOLD;
+        }
+        Self::from_float(value.max(900.))
+    }
+
+    /// Return the lighter weight.
+    ///
+    /// See the table in:
+    /// https://drafts.csswg.org/css-fonts-4/#font-weight-numeric-values
+    pub fn lighter(self) -> Self {
+        let value = self.value();
+        if value < 550. {
+            return Self::from_float(value.min(100.));
+        }
+        if value < 750. {
+            return Self::NORMAL;
+        }
+        Self::BOLD
+    }
+}
+
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+)]
+#[cfg_attr(feature = "servo", derive(Serialize, Deserialize))]
+/// The computed value of font-size
+pub struct FontSize {
+    /// The computed size, that we use to compute ems etc. This accounts for
+    /// e.g., text-zoom.
+    pub computed_size: NonNegativeLength,
+    /// The actual used size. This is the computed font size, potentially
+    /// constrained by other factors like minimum font-size settings and so on.
+    #[css(skip)]
+    pub used_size: NonNegativeLength,
+    /// If derived from a keyword, the keyword and additional transformations applied to it
+    #[css(skip)]
+    pub keyword_info: KeywordInfo,
+}
+
+impl FontSize {
+    /// The actual computed font size.
+    #[inline]
+    pub fn computed_size(&self) -> Length {
+        self.computed_size.0
+    }
+
+    /// The actual used font size.
+    #[inline]
+    pub fn used_size(&self) -> Length {
+        self.used_size.0
+    }
+
+    #[inline]
+    /// Get default value of font size.
+    pub fn medium() -> Self {
+        Self {
+            computed_size: NonNegative(Length::new(specified::FONT_MEDIUM_PX)),
+            used_size: NonNegative(Length::new(specified::FONT_MEDIUM_PX)),
+            keyword_info: KeywordInfo::medium(),
+        }
+    }
+}
+
+impl ToAnimatedValue for FontSize {
+    type AnimatedValue = Length;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.computed_size.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        FontSize {
+            computed_size: NonNegative(animated.clamp_to_non_negative()),
+            used_size: NonNegative(animated.clamp_to_non_negative()),
+            keyword_info: KeywordInfo::none(),
+        }
+    }
+}
+
+#[derive(Clone, Debug, Eq, PartialEq, ToComputedValue, ToResolvedValue)]
+#[cfg_attr(feature = "servo", derive(Hash, MallocSizeOf, Serialize, Deserialize))]
+/// Specifies a prioritized list of font family names or generic family names.
+#[repr(C)]
+pub struct FontFamily {
+    /// The actual list of family names.
+    pub families: FontFamilyList,
+    /// Whether this font-family came from a specified system-font.
+    pub is_system_font: bool,
+    /// Whether this is the initial font-family that might react to language
+    /// changes.
+    pub is_initial: bool,
+}
+
+macro_rules! static_font_family {
+    ($ident:ident, $family:expr) => {
+        lazy_static! {
+            static ref $ident: FontFamily = FontFamily {
+                families: FontFamilyList {
+                    list: crate::ArcSlice::from_iter_leaked(std::iter::once($family)),
+                },
+                is_system_font: false,
+                is_initial: false,
+            };
+        }
+    };
+}
+
+impl FontFamily {
+    #[inline]
+    /// Get default font family as `serif` which is a generic font-family
+    pub fn serif() -> Self {
+        Self::generic(GenericFontFamily::Serif).clone()
+    }
+
+    /// Returns the font family for `-moz-bullet-font`.
+    pub(crate) fn moz_bullet() -> &'static Self {
+        static_font_family!(
+            MOZ_BULLET,
+            SingleFontFamily::FamilyName(FamilyName {
+                name: atom!("-moz-bullet-font"),
+                syntax: FontFamilyNameSyntax::Identifiers,
+            })
+        );
+
+        &*MOZ_BULLET
+    }
+
+    /// Returns a font family for a single system font.
+    pub fn for_system_font(name: &str) -> Self {
+        Self {
+            families: FontFamilyList {
+                list: crate::ArcSlice::from_iter(std::iter::once(SingleFontFamily::FamilyName(
+                    FamilyName {
+                        name: Atom::from(name),
+                        syntax: FontFamilyNameSyntax::Identifiers,
+                    },
+                ))),
+            },
+            is_system_font: true,
+            is_initial: false,
+        }
+    }
+
+    /// Returns a generic font family.
+    pub fn generic(generic: GenericFontFamily) -> &'static Self {
+        macro_rules! generic_font_family {
+            ($ident:ident, $family:ident) => {
+                static_font_family!(
+                    $ident,
+                    SingleFontFamily::Generic(GenericFontFamily::$family)
+                )
+            };
+        }
+
+        generic_font_family!(SERIF, Serif);
+        generic_font_family!(SANS_SERIF, SansSerif);
+        generic_font_family!(MONOSPACE, Monospace);
+        generic_font_family!(CURSIVE, Cursive);
+        generic_font_family!(FANTASY, Fantasy);
+        generic_font_family!(MOZ_EMOJI, MozEmoji);
+        generic_font_family!(SYSTEM_UI, SystemUi);
+
+        match generic {
+            GenericFontFamily::None => {
+                debug_assert!(false, "Bogus caller!");
+                &*SERIF
+            },
+            GenericFontFamily::Serif => &*SERIF,
+            GenericFontFamily::SansSerif => &*SANS_SERIF,
+            GenericFontFamily::Monospace => &*MONOSPACE,
+            GenericFontFamily::Cursive => &*CURSIVE,
+            GenericFontFamily::Fantasy => &*FANTASY,
+            GenericFontFamily::MozEmoji => &*MOZ_EMOJI,
+            GenericFontFamily::SystemUi => &*SYSTEM_UI,
+        }
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl MallocSizeOf for FontFamily {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        use malloc_size_of::MallocUnconditionalSizeOf;
+        // SharedFontList objects are generally measured from the pointer stored
+        // in the specified value. So only count this if the SharedFontList is
+        // unshared.
+        let shared_font_list = &self.families.list;
+        if shared_font_list.is_unique() {
+            shared_font_list.unconditional_size_of(ops)
+        } else {
+            0
+        }
+    }
+}
+
+impl ToCss for FontFamily {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        let mut iter = self.families.iter();
+        match iter.next() {
+            Some(f) => f.to_css(dest)?,
+            None => return Ok(()),
+        }
+        for family in iter {
+            dest.write_str(", ")?;
+            family.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+/// The name of a font family of choice.
+#[derive(
+    Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[repr(C)]
+pub struct FamilyName {
+    /// Name of the font family.
+    pub name: Atom,
+    /// Syntax of the font family.
+    pub syntax: FontFamilyNameSyntax,
+}
+
+impl ToCss for FamilyName {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        match self.syntax {
+            FontFamilyNameSyntax::Quoted => {
+                dest.write_char('"')?;
+                write!(CssStringWriter::new(dest), "{}", self.name)?;
+                dest.write_char('"')
+            },
+            FontFamilyNameSyntax::Identifiers => {
+                let mut first = true;
+                for ident in self.name.to_string().split(' ') {
+                    if first {
+                        first = false;
+                    } else {
+                        dest.write_char(' ')?;
+                    }
+                    debug_assert!(
+                        !ident.is_empty(),
+                        "Family name with leading, \
+                         trailing, or consecutive white spaces should \
+                         have been marked quoted by the parser"
+                    );
+                    serialize_identifier(ident, dest)?;
+                }
+                Ok(())
+            },
+        }
+    }
+}
+
+#[derive(
+    Clone, Copy, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+/// Font family names must either be given quoted as strings,
+/// or unquoted as a sequence of one or more identifiers.
+#[repr(u8)]
+pub enum FontFamilyNameSyntax {
+    /// The family name was specified in a quoted form, e.g. "Font Name"
+    /// or 'Font Name'.
+    Quoted,
+
+    /// The family name was specified in an unquoted form as a sequence of
+    /// identifiers.
+    Identifiers,
+}
+
+/// A set of faces that vary in weight, width or slope.
+/// cbindgen:derive-mut-casts=true
+#[derive(
+    Clone, Debug, Eq, MallocSizeOf, PartialEq, ToCss, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize, Hash))]
+#[repr(u8)]
+pub enum SingleFontFamily {
+    /// The name of a font family of choice.
+    FamilyName(FamilyName),
+    /// Generic family name.
+    Generic(GenericFontFamily),
+}
+
+fn system_ui_enabled(_: &ParserContext) -> bool {
+    static_prefs::pref!("layout.css.system-ui.enabled")
+}
+
+/// A generic font-family name.
+///
+/// The order here is important, if you change it make sure that
+/// `gfxPlatformFontList.h`s ranged array and `gfxFontFamilyList`'s
+/// sSingleGenerics are updated as well.
+///
+/// NOTE(emilio): Should be u8, but it's a u32 because of ABI issues between GCC
+/// and LLVM see https://bugs.llvm.org/show_bug.cgi?id=44228 / bug 1600735 /
+/// bug 1726515.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[repr(u32)]
+#[allow(missing_docs)]
+pub enum GenericFontFamily {
+    /// No generic family specified, only for internal usage.
+    ///
+    /// NOTE(emilio): Gecko code relies on this variant being zero.
+    #[css(skip)]
+    None = 0,
+    Serif,
+    SansSerif,
+    #[parse(aliases = "-moz-fixed")]
+    Monospace,
+    Cursive,
+    Fantasy,
+    #[parse(condition = "system_ui_enabled")]
+    SystemUi,
+    /// An internal value for emoji font selection.
+    #[css(skip)]
+    #[cfg(feature = "gecko")]
+    MozEmoji,
+}
+
+impl GenericFontFamily {
+    /// When we disallow websites to override fonts, we ignore some generic
+    /// families that the website might specify, since they're not configured by
+    /// the user. See bug 789788 and bug 1730098.
+    pub(crate) fn valid_for_user_font_prioritization(self) -> bool {
+        match self {
+            Self::None | Self::Fantasy | Self::Cursive | Self::SystemUi | Self::MozEmoji => false,
+
+            Self::Serif | Self::SansSerif | Self::Monospace => true,
+        }
+    }
+}
+
+impl Parse for SingleFontFamily {
+    /// Parse a font-family value.
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(value) = input.try_parse(|i| i.expect_string_cloned()) {
+            return Ok(SingleFontFamily::FamilyName(FamilyName {
+                name: Atom::from(&*value),
+                syntax: FontFamilyNameSyntax::Quoted,
+            }));
+        }
+
+        if let Ok(generic) = input.try_parse(|i| GenericFontFamily::parse(context, i)) {
+            return Ok(SingleFontFamily::Generic(generic));
+        }
+
+        let first_ident = input.expect_ident_cloned()?;
+        let reserved = match_ignore_ascii_case! { &first_ident,
+            // https://drafts.csswg.org/css-fonts/#propdef-font-family
+            // "Font family names that happen to be the same as a keyword value
+            //  (`inherit`, `serif`, `sans-serif`, `monospace`, `fantasy`, and `cursive`)
+            //  must be quoted to prevent confusion with the keywords with the same names.
+            //  The keywords ‘initial’ and ‘default’ are reserved for future use
+            //  and must also be quoted when used as font names.
+            //  UAs must not consider these keywords as matching the <family-name> type."
+            "inherit" | "initial" | "unset" | "revert" | "default" => true,
+            _ => false,
+        };
+
+        let mut value = first_ident.as_ref().to_owned();
+        let mut serialize_quoted = value.contains(' ');
+
+        // These keywords are not allowed by themselves.
+        // The only way this value can be valid with with another keyword.
+        if reserved {
+            let ident = input.expect_ident()?;
+            serialize_quoted = serialize_quoted || ident.contains(' ');
+            value.push(' ');
+            value.push_str(&ident);
+        }
+        while let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            serialize_quoted = serialize_quoted || ident.contains(' ');
+            value.push(' ');
+            value.push_str(&ident);
+        }
+        let syntax = if serialize_quoted {
+            // For font family names which contains special white spaces, e.g.
+            // `font-family: \ a\ \ b\ \ c\ ;`, it is tricky to serialize them
+            // as identifiers correctly. Just mark them quoted so we don't need
+            // to worry about them in serialization code.
+            FontFamilyNameSyntax::Quoted
+        } else {
+            FontFamilyNameSyntax::Identifiers
+        };
+        Ok(SingleFontFamily::FamilyName(FamilyName {
+            name: Atom::from(value),
+            syntax,
+        }))
+    }
+}
+
+#[cfg(feature = "servo")]
+impl SingleFontFamily {
+    /// Get the corresponding font-family with Atom
+    pub fn from_atom(input: Atom) -> SingleFontFamily {
+        match input {
+            atom!("serif") => return SingleFontFamily::Generic(GenericFontFamily::Serif),
+            atom!("sans-serif") => return SingleFontFamily::Generic(GenericFontFamily::SansSerif),
+            atom!("cursive") => return SingleFontFamily::Generic(GenericFontFamily::Cursive),
+            atom!("fantasy") => return SingleFontFamily::Generic(GenericFontFamily::Fantasy),
+            atom!("monospace") => return SingleFontFamily::Generic(GenericFontFamily::Monospace),
+            _ => {},
+        }
+
+        match_ignore_ascii_case! { &input,
+            "serif" => return SingleFontFamily::Generic(GenericFontFamily::Serif),
+            "sans-serif" => return SingleFontFamily::Generic(GenericFontFamily::SansSerif),
+            "cursive" => return SingleFontFamily::Generic(GenericFontFamily::Cursive),
+            "fantasy" => return SingleFontFamily::Generic(GenericFontFamily::Fantasy),
+            "monospace" => return SingleFontFamily::Generic(GenericFontFamily::Monospace),
+            _ => {}
+        }
+
+        // We don't know if it's quoted or not. So we set it to
+        // quoted by default.
+        SingleFontFamily::FamilyName(FamilyName {
+            name: input,
+            syntax: FontFamilyNameSyntax::Quoted,
+        })
+    }
+}
+
+/// A list of font families.
+#[derive(Clone, Debug, ToComputedValue, ToResolvedValue, ToShmem, PartialEq, Eq)]
+#[repr(C)]
+pub struct FontFamilyList {
+    /// The actual list of font families specified.
+    pub list: crate::ArcSlice<SingleFontFamily>,
+}
+
+impl FontFamilyList {
+    /// Return iterator of SingleFontFamily
+    pub fn iter(&self) -> impl Iterator<Item = &SingleFontFamily> {
+        self.list.iter()
+    }
+
+    /// If there's a generic font family on the list which is suitable for user
+    /// font prioritization, then move it to the front of the list. Otherwise,
+    /// prepend the default generic.
+    pub(crate) fn prioritize_first_generic_or_prepend(&mut self, generic: GenericFontFamily) {
+        let index_of_first_generic = self.iter().position(|f| match *f {
+            SingleFontFamily::Generic(f) => f.valid_for_user_font_prioritization(),
+            _ => false,
+        });
+
+        if let Some(0) = index_of_first_generic {
+            return; // Already first
+        }
+
+        let mut new_list = self.list.iter().cloned().collect::<Vec<_>>();
+        let element_to_prepend = match index_of_first_generic {
+            Some(i) => new_list.remove(i),
+            None => SingleFontFamily::Generic(generic),
+        };
+
+        new_list.insert(0, element_to_prepend);
+        self.list = crate::ArcSlice::from_iter(new_list.into_iter());
+    }
+
+    /// Returns whether we need to prioritize user fonts.
+    pub(crate) fn needs_user_font_prioritization(&self) -> bool {
+        self.iter().next().map_or(true, |f| match f {
+            SingleFontFamily::Generic(f) => !f.valid_for_user_font_prioritization(),
+            _ => true,
+        })
+    }
+
+    /// Return the generic ID if it is a single generic font
+    pub fn single_generic(&self) -> Option<GenericFontFamily> {
+        let mut iter = self.iter();
+        if let Some(SingleFontFamily::Generic(f)) = iter.next() {
+            if iter.next().is_none() {
+                return Some(*f);
+            }
+        }
+        None
+    }
+}
+
+/// Preserve the readability of text when font fallback occurs
+pub type FontSizeAdjust = generics::GenericFontSizeAdjust<NonNegativeNumber>;
+
+impl FontSizeAdjust {
+    #[inline]
+    /// Default value of font-size-adjust
+    pub fn none() -> Self {
+        FontSizeAdjust::None
+    }
+}
+
+/// Use FontSettings as computed type of FontFeatureSettings.
+pub type FontFeatureSettings = FontSettings<FeatureTagValue<Integer>>;
+
+/// The computed value for font-variation-settings.
+pub type FontVariationSettings = FontSettings<VariationValue<Number>>;
+
+/// font-language-override can only have a single three-letter
+/// OpenType "language system" tag, so we should be able to compute
+/// it and store it as a 32-bit integer
+/// (see http://www.microsoft.com/typography/otspec/languagetags.htm).
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToResolvedValue)]
+#[repr(C)]
+pub struct FontLanguageOverride(pub u32);
+
+impl FontLanguageOverride {
+    #[inline]
+    /// Get computed default value of `font-language-override` with 0
+    pub fn zero() -> FontLanguageOverride {
+        FontLanguageOverride(0)
+    }
+
+    /// Returns this value as a `&str`, backed by `storage`.
+    #[inline]
+    pub(crate) fn to_str(self, storage: &mut [u8; 4]) -> &str {
+        *storage = u32::to_be_bytes(self.0);
+        // Safe because we ensure it's ASCII during computing
+        let slice = if cfg!(debug_assertions) {
+            std::str::from_utf8(&storage[..]).unwrap()
+        } else {
+            unsafe { std::str::from_utf8_unchecked(&storage[..]) }
+        };
+        slice.trim_end()
+    }
+
+    /// Parses a str, return `Self::zero()` if the input isn't a valid OpenType
+    /// "language system" tag.
+    #[inline]
+    pub fn from_str(lang: &str) -> Self {
+        if lang.is_empty() || lang.len() > 4 {
+            return Self::zero();
+        }
+        let mut bytes = [b' '; 4];
+        for (byte, lang_byte) in bytes.iter_mut().zip(lang.as_bytes()) {
+            if !lang_byte.is_ascii() {
+                return Self::zero();
+            }
+            *byte = *lang_byte;
+        }
+        Self(u32::from_be_bytes(bytes))
+    }
+
+    /// Unsafe because `Self::to_str` requires the value to represent a UTF-8
+    /// string.
+    #[inline]
+    pub unsafe fn from_u32(value: u32) -> Self {
+        Self(value)
+    }
+}
+
+impl ToCss for FontLanguageOverride {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        if self.0 == 0 {
+            return dest.write_str("normal");
+        }
+        self.to_str(&mut [0; 4]).to_css(dest)
+    }
+}
+
+// FIXME(emilio): Make Gecko use the cbindgen'd fontLanguageOverride, then
+// remove this.
+#[cfg(feature = "gecko")]
+impl From<u32> for FontLanguageOverride {
+    fn from(v: u32) -> Self {
+        unsafe { Self::from_u32(v) }
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl From<FontLanguageOverride> for u32 {
+    fn from(v: FontLanguageOverride) -> u32 {
+        v.0
+    }
+}
+
+impl ToComputedValue for specified::MozScriptMinSize {
+    type ComputedValue = MozScriptMinSize;
+
+    fn to_computed_value(&self, cx: &Context) -> MozScriptMinSize {
+        // this value is used in the computation of font-size, so
+        // we use the parent size
+        let base_size = FontBaseSize::InheritedStyle;
+        match self.0 {
+            NoCalcLength::FontRelative(value) => value.to_computed_value(cx, base_size),
+            NoCalcLength::ServoCharacterWidth(value) => {
+                value.to_computed_value(base_size.resolve(cx).computed_size())
+            },
+            ref l => l.to_computed_value(cx),
+        }
+    }
+
+    fn from_computed_value(other: &MozScriptMinSize) -> Self {
+        specified::MozScriptMinSize(ToComputedValue::from_computed_value(other))
+    }
+}
+
+/// The computed value of the math-depth property.
+pub type MathDepth = i8;
+
+#[cfg(feature = "gecko")]
+impl ToComputedValue for specified::MathDepth {
+    type ComputedValue = MathDepth;
+
+    fn to_computed_value(&self, cx: &Context) -> i8 {
+        use crate::properties::longhands::math_style::SpecifiedValue as MathStyleValue;
+        use std::{cmp, i8};
+
+        let int = match *self {
+            specified::MathDepth::AutoAdd => {
+                let parent = cx.builder.get_parent_font().clone_math_depth() as i32;
+                let style = cx.builder.get_parent_font().clone_math_style();
+                if style == MathStyleValue::Compact {
+                    parent.saturating_add(1)
+                } else {
+                    parent
+                }
+            },
+            specified::MathDepth::Add(rel) => {
+                let parent = cx.builder.get_parent_font().clone_math_depth();
+                (parent as i32).saturating_add(rel.to_computed_value(cx))
+            },
+            specified::MathDepth::Absolute(abs) => abs.to_computed_value(cx),
+        };
+        cmp::min(int, i8::MAX as i32) as i8
+    }
+
+    fn from_computed_value(other: &i8) -> Self {
+        let computed_value = *other as i32;
+        specified::MathDepth::Absolute(SpecifiedInteger::from_computed_value(&computed_value))
+    }
+}
+
+/// - Use a signed 8.8 fixed-point value (representable range -128.0..128)
+///
+/// Values of <angle> below -90 or above 90 not permitted, so we use out of
+/// range values to represent normal | oblique
+pub const FONT_STYLE_FRACTION_BITS: u16 = 8;
+
+/// This is an alias which is useful mostly as a cbindgen / C++ inference
+/// workaround.
+pub type FontStyleFixedPoint = FixedPoint<i16, FONT_STYLE_FRACTION_BITS>;
+
+/// The computed value of `font-style`.
+///
+/// - Define out of range values min value (-128.0) as meaning 'normal'
+/// - Define max value (127.99609375) as 'italic'
+/// - Other values represent 'oblique <angle>'
+/// - Note that 'oblique 0deg' is distinct from 'normal' (should it be?)
+///
+/// cbindgen:derive-lt
+/// cbindgen:derive-lte
+/// cbindgen:derive-gt
+/// cbindgen:derive-gte
+#[derive(
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    ToResolvedValue,
+)]
+#[repr(C)]
+pub struct FontStyle(FontStyleFixedPoint);
+
+impl FontStyle {
+    /// The normal keyword.
+    pub const NORMAL: FontStyle = FontStyle(FontStyleFixedPoint {
+        value: 100 << FONT_STYLE_FRACTION_BITS,
+    });
+    /// The italic keyword.
+    pub const ITALIC: FontStyle = FontStyle(FontStyleFixedPoint {
+        value: 101 << FONT_STYLE_FRACTION_BITS,
+    });
+
+    /// The default angle for `font-style: oblique`.
+    /// See also https://github.com/w3c/csswg-drafts/issues/2295
+    pub const DEFAULT_OBLIQUE_DEGREES: i16 = 14;
+
+    /// The `oblique` keyword with the default degrees.
+    pub const OBLIQUE: FontStyle = FontStyle(FontStyleFixedPoint {
+        value: Self::DEFAULT_OBLIQUE_DEGREES << FONT_STYLE_FRACTION_BITS,
+    });
+
+    /// The `normal` value.
+    #[inline]
+    pub fn normal() -> Self {
+        Self::NORMAL
+    }
+
+    /// Returns the oblique angle for this style.
+    pub fn oblique(degrees: f32) -> Self {
+        Self(FixedPoint::from_float(
+            degrees
+                .max(specified::FONT_STYLE_OBLIQUE_MIN_ANGLE_DEGREES)
+                .min(specified::FONT_STYLE_OBLIQUE_MAX_ANGLE_DEGREES),
+        ))
+    }
+
+    /// Returns the oblique angle for this style.
+    pub fn oblique_degrees(&self) -> f32 {
+        debug_assert_ne!(*self, Self::NORMAL);
+        debug_assert_ne!(*self, Self::ITALIC);
+        self.0.to_float()
+    }
+}
+
+impl ToCss for FontStyle {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        if *self == Self::NORMAL {
+            return dest.write_str("normal");
+        }
+        if *self == Self::ITALIC {
+            return dest.write_str("italic");
+        }
+        if *self == Self::OBLIQUE {
+            return dest.write_str("oblique");
+        }
+        dest.write_str("oblique ")?;
+        let angle = Angle::from_degrees(self.oblique_degrees());
+        angle.to_css(dest)?;
+        Ok(())
+    }
+}
+
+impl ToAnimatedValue for FontStyle {
+    type AnimatedValue = generics::FontStyle<Angle>;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        if self == Self::NORMAL {
+            // This allows us to animate between normal and oblique values. Per spec,
+            // https://drafts.csswg.org/css-fonts-4/#font-style-prop:
+            //   Animation type: by computed value type; 'normal' animates as 'oblique 0deg'
+            return generics::FontStyle::Oblique(Angle::from_degrees(0.0))
+        }
+        if self == Self::ITALIC {
+            return generics::FontStyle::Italic;
+        }
+        generics::FontStyle::Oblique(Angle::from_degrees(self.oblique_degrees()))
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        match animated {
+            generics::FontStyle::Normal => Self::NORMAL,
+            generics::FontStyle::Italic => Self::ITALIC,
+            generics::FontStyle::Oblique(ref angle) =>
+                if angle.degrees() == 0.0 {
+                    // Reverse the conversion done in to_animated_value()
+                    Self::NORMAL
+                } else {
+                    Self::oblique(angle.degrees())
+                },
+        }
+    }
+}
+
+/// font-stretch is a percentage relative to normal.
+///
+/// We use an unsigned 10.6 fixed-point value (range 0.0 - 1023.984375)
+///
+/// We arbitrarily limit here to 1000%. (If that becomes a problem, we could
+/// reduce the number of fractional bits and increase the limit.)
+pub const FONT_STRETCH_FRACTION_BITS: u16 = 6;
+
+/// This is an alias which is useful mostly as a cbindgen / C++ inference
+/// workaround.
+pub type FontStretchFixedPoint = FixedPoint<u16, FONT_STRETCH_FRACTION_BITS>;
+
+/// A value for the font-stretch property per:
+///
+/// https://drafts.csswg.org/css-fonts-4/#propdef-font-stretch
+///
+/// cbindgen:derive-lt
+/// cbindgen:derive-lte
+/// cbindgen:derive-gt
+/// cbindgen:derive-gte
+#[derive(
+    Clone, ComputeSquaredDistance, Copy, Debug, MallocSizeOf, PartialEq, PartialOrd, ToResolvedValue,
+)]
+#[repr(C)]
+pub struct FontStretch(pub FontStretchFixedPoint);
+
+impl FontStretch {
+    /// The fraction bits, as an easy-to-access-constant.
+    pub const FRACTION_BITS: u16 = FONT_STRETCH_FRACTION_BITS;
+    /// 0.5 in our floating point representation.
+    pub const HALF: u16 = 1 << (Self::FRACTION_BITS - 1);
+
+    /// The `ultra-condensed` keyword.
+    pub const ULTRA_CONDENSED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: 50 << Self::FRACTION_BITS,
+    });
+    /// The `extra-condensed` keyword.
+    pub const EXTRA_CONDENSED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: (62 << Self::FRACTION_BITS) + Self::HALF,
+    });
+    /// The `condensed` keyword.
+    pub const CONDENSED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: 75 << Self::FRACTION_BITS,
+    });
+    /// The `semi-condensed` keyword.
+    pub const SEMI_CONDENSED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: (87 << Self::FRACTION_BITS) + Self::HALF,
+    });
+    /// The `normal` keyword.
+    pub const NORMAL: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: 100 << Self::FRACTION_BITS,
+    });
+    /// The `semi-expanded` keyword.
+    pub const SEMI_EXPANDED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: (112 << Self::FRACTION_BITS) + Self::HALF,
+    });
+    /// The `expanded` keyword.
+    pub const EXPANDED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: 125 << Self::FRACTION_BITS,
+    });
+    /// The `extra-expanded` keyword.
+    pub const EXTRA_EXPANDED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: 150 << Self::FRACTION_BITS,
+    });
+    /// The `ultra-expanded` keyword.
+    pub const ULTRA_EXPANDED: FontStretch = FontStretch(FontStretchFixedPoint {
+        value: 200 << Self::FRACTION_BITS,
+    });
+
+    /// 100%
+    pub fn hundred() -> Self {
+        Self::NORMAL
+    }
+
+    /// Converts to a computed percentage.
+    #[inline]
+    pub fn to_percentage(&self) -> Percentage {
+        Percentage(self.0.to_float() / 100.0)
+    }
+
+    /// Converts from a computed percentage value.
+    pub fn from_percentage(p: f32) -> Self {
+        Self(FixedPoint::from_float((p * 100.).max(0.0).min(1000.0)))
+    }
+
+    /// Returns a relevant stretch value from a keyword.
+    /// https://drafts.csswg.org/css-fonts-4/#font-stretch-prop
+    pub fn from_keyword(kw: specified::FontStretchKeyword) -> Self {
+        use specified::FontStretchKeyword::*;
+        match kw {
+            UltraCondensed => Self::ULTRA_CONDENSED,
+            ExtraCondensed => Self::EXTRA_CONDENSED,
+            Condensed => Self::CONDENSED,
+            SemiCondensed => Self::SEMI_CONDENSED,
+            Normal => Self::NORMAL,
+            SemiExpanded => Self::SEMI_EXPANDED,
+            Expanded => Self::EXPANDED,
+            ExtraExpanded => Self::EXTRA_EXPANDED,
+            UltraExpanded => Self::ULTRA_EXPANDED,
+        }
+    }
+
+    /// Returns the stretch keyword if we map to one of the relevant values.
+    pub fn as_keyword(&self) -> Option<specified::FontStretchKeyword> {
+        use specified::FontStretchKeyword::*;
+        // TODO: Can we use match here?
+        if *self == Self::ULTRA_CONDENSED {
+            return Some(UltraCondensed);
+        }
+        if *self == Self::EXTRA_CONDENSED {
+            return Some(ExtraCondensed);
+        }
+        if *self == Self::CONDENSED {
+            return Some(Condensed);
+        }
+        if *self == Self::SEMI_CONDENSED {
+            return Some(SemiCondensed);
+        }
+        if *self == Self::NORMAL {
+            return Some(Normal);
+        }
+        if *self == Self::SEMI_EXPANDED {
+            return Some(SemiExpanded);
+        }
+        if *self == Self::EXPANDED {
+            return Some(Expanded);
+        }
+        if *self == Self::EXTRA_EXPANDED {
+            return Some(ExtraExpanded);
+        }
+        if *self == Self::ULTRA_EXPANDED {
+            return Some(UltraExpanded);
+        }
+        None
+    }
+}
+
+impl ToCss for FontStretch {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        self.to_percentage().to_css(dest)
+    }
+}
+
+impl ToAnimatedValue for FontStretch {
+    type AnimatedValue = Percentage;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.to_percentage()
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        Self::from_percentage(animated.0)
+    }
+}
diff --git a/servo/components/style/values/computed/image.rs b/servo/components/style/values/computed/image.rs
new file mode 100644
index 0000000000..c12cbd1a2a
--- /dev/null
+++ b/servo/components/style/values/computed/image.rs
@@ -0,0 +1,211 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the computed value of
+//! [`image`][image]s
+//!
+//! [image]: https://drafts.csswg.org/css-images/#image-values
+
+use crate::values::computed::percentage::Percentage;
+use crate::values::computed::position::Position;
+use crate::values::computed::url::ComputedImageUrl;
+#[cfg(feature = "gecko")]
+use crate::values::computed::NumberOrPercentage;
+use crate::values::computed::{Angle, Color, Context};
+use crate::values::computed::{
+    AngleOrPercentage, LengthPercentage, NonNegativeLength, NonNegativeLengthPercentage,
+    Resolution, ToComputedValue,
+};
+use crate::values::generics::image::{self as generic, GradientCompatMode};
+use crate::values::specified::image as specified;
+use crate::values::specified::position::{HorizontalPositionKeyword, VerticalPositionKeyword};
+use std::f32::consts::PI;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+pub use specified::ImageRendering;
+
+/// Computed values for an image according to CSS-IMAGES.
+/// <https://drafts.csswg.org/css-images/#image-values>
+pub type Image =
+    generic::GenericImage<Gradient, MozImageRect, ComputedImageUrl, Color, Percentage, Resolution>;
+
+// Images should remain small, see https://github.com/servo/servo/pull/18430
+size_of_test!(Image, 16);
+
+/// Computed values for a CSS gradient.
+/// <https://drafts.csswg.org/css-images/#gradients>
+pub type Gradient = generic::GenericGradient<
+    LineDirection,
+    LengthPercentage,
+    NonNegativeLength,
+    NonNegativeLengthPercentage,
+    Position,
+    Angle,
+    AngleOrPercentage,
+    Color,
+>;
+
+/// Computed values for CSS cross-fade
+/// <https://drafts.csswg.org/css-images-4/#cross-fade-function>
+pub type CrossFade = generic::CrossFade<Image, Color, Percentage>;
+
+/// A computed radial gradient ending shape.
+pub type EndingShape = generic::GenericEndingShape<NonNegativeLength, NonNegativeLengthPercentage>;
+
+/// A computed gradient line direction.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToResolvedValue)]
+#[repr(C, u8)]
+pub enum LineDirection {
+    /// An angle.
+    Angle(Angle),
+    /// A horizontal direction.
+    Horizontal(HorizontalPositionKeyword),
+    /// A vertical direction.
+    Vertical(VerticalPositionKeyword),
+    /// A corner.
+    Corner(HorizontalPositionKeyword, VerticalPositionKeyword),
+}
+
+/// The computed value for an `image-set()` image.
+pub type ImageSet = generic::GenericImageSet<Image, Resolution>;
+
+impl ToComputedValue for specified::ImageSet {
+    type ComputedValue = ImageSet;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        let items = self.items.to_computed_value(context);
+        let dpr = context.device().device_pixel_ratio().get();
+
+        // If no item have a supported MIME type, the behavior is undefined by the standard
+        // By default, we select the first item
+        let mut supported_image = false;
+        let mut selected_index = 0;
+        let mut selected_resolution = items[0].resolution.dppx();
+
+        for (i, item) in items.iter().enumerate() {
+            // If the MIME type is not supported, we discard the ImageSetItem
+            if item.has_mime_type && !context.device().is_supported_mime_type(&item.mime_type) {
+                continue;
+            }
+
+            let candidate_resolution = item.resolution.dppx();
+
+            // https://drafts.csswg.org/css-images-4/#image-set-notation:
+            //
+            //     Make a UA-specific choice of which to load, based on whatever
+            //     criteria deemed relevant (such as the resolution of the
+            //     display, connection speed, etc).
+            //
+            // For now, select the lowest resolution greater than display
+            // density, otherwise the greatest resolution available
+            let better_candidate = || {
+                if selected_resolution < dpr && candidate_resolution > selected_resolution {
+                    return true;
+                }
+                if candidate_resolution < selected_resolution && candidate_resolution >= dpr {
+                    return true;
+                }
+                false
+            };
+
+            // The first item with a supported MIME type is obviously the current best candidate
+            if !supported_image || better_candidate() {
+                supported_image = true;
+                selected_index = i;
+                selected_resolution = candidate_resolution;
+            }
+        }
+
+        ImageSet {
+            selected_index,
+            items,
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Self {
+            selected_index: 0,
+            items: ToComputedValue::from_computed_value(&computed.items),
+        }
+    }
+}
+
+/// Computed values for `-moz-image-rect(...)`.
+#[cfg(feature = "gecko")]
+pub type MozImageRect = generic::GenericMozImageRect<NumberOrPercentage, ComputedImageUrl>;
+
+/// Empty enum on non-gecko
+#[cfg(not(feature = "gecko"))]
+pub type MozImageRect = specified::MozImageRect;
+
+impl generic::LineDirection for LineDirection {
+    fn points_downwards(&self, compat_mode: GradientCompatMode) -> bool {
+        match *self {
+            LineDirection::Angle(angle) => angle.radians() == PI,
+            LineDirection::Vertical(VerticalPositionKeyword::Bottom) => {
+                compat_mode == GradientCompatMode::Modern
+            },
+            LineDirection::Vertical(VerticalPositionKeyword::Top) => {
+                compat_mode != GradientCompatMode::Modern
+            },
+            _ => false,
+        }
+    }
+
+    fn to_css<W>(&self, dest: &mut CssWriter<W>, compat_mode: GradientCompatMode) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            LineDirection::Angle(ref angle) => angle.to_css(dest),
+            LineDirection::Horizontal(x) => {
+                if compat_mode == GradientCompatMode::Modern {
+                    dest.write_str("to ")?;
+                }
+                x.to_css(dest)
+            },
+            LineDirection::Vertical(y) => {
+                if compat_mode == GradientCompatMode::Modern {
+                    dest.write_str("to ")?;
+                }
+                y.to_css(dest)
+            },
+            LineDirection::Corner(x, y) => {
+                if compat_mode == GradientCompatMode::Modern {
+                    dest.write_str("to ")?;
+                }
+                x.to_css(dest)?;
+                dest.write_str(" ")?;
+                y.to_css(dest)
+            },
+        }
+    }
+}
+
+impl ToComputedValue for specified::LineDirection {
+    type ComputedValue = LineDirection;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            specified::LineDirection::Angle(ref angle) => {
+                LineDirection::Angle(angle.to_computed_value(context))
+            },
+            specified::LineDirection::Horizontal(x) => LineDirection::Horizontal(x),
+            specified::LineDirection::Vertical(y) => LineDirection::Vertical(y),
+            specified::LineDirection::Corner(x, y) => LineDirection::Corner(x, y),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        match *computed {
+            LineDirection::Angle(ref angle) => {
+                specified::LineDirection::Angle(ToComputedValue::from_computed_value(angle))
+            },
+            LineDirection::Horizontal(x) => specified::LineDirection::Horizontal(x),
+            LineDirection::Vertical(y) => specified::LineDirection::Vertical(y),
+            LineDirection::Corner(x, y) => specified::LineDirection::Corner(x, y),
+        }
+    }
+}
diff --git a/servo/components/style/values/computed/length.rs b/servo/components/style/values/computed/length.rs
new file mode 100644
index 0000000000..8c42748ed5
--- /dev/null
+++ b/servo/components/style/values/computed/length.rs
@@ -0,0 +1,520 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! `<length>` computed values, and related ones.
+
+use super::{Context, Number, ToComputedValue};
+use crate::values::animated::ToAnimatedValue;
+use crate::values::computed::NonNegativeNumber;
+use crate::values::generics::length as generics;
+use crate::values::generics::length::{
+    GenericLengthOrNumber, GenericLengthPercentageOrNormal, GenericMaxSize, GenericSize,
+};
+use crate::values::generics::NonNegative;
+use crate::values::specified::length::{AbsoluteLength, FontBaseSize};
+use crate::values::{specified, CSSFloat};
+use crate::Zero;
+use app_units::Au;
+use std::fmt::{self, Write};
+use std::ops::{Add, AddAssign, Div, Mul, MulAssign, Neg, Sub};
+use style_traits::{CSSPixel, CssWriter, ToCss};
+
+pub use super::image::Image;
+pub use super::length_percentage::{LengthPercentage, NonNegativeLengthPercentage};
+pub use crate::values::specified::url::UrlOrNone;
+pub use crate::values::specified::{Angle, BorderStyle, Time};
+
+impl ToComputedValue for specified::NoCalcLength {
+    type ComputedValue = Length;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        self.to_computed_value_with_base_size(context, FontBaseSize::CurrentStyle)
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        specified::NoCalcLength::Absolute(AbsoluteLength::Px(computed.px()))
+    }
+}
+
+impl specified::NoCalcLength {
+    /// Computes a length with a given font-relative base size.
+    pub fn to_computed_value_with_base_size(
+        &self,
+        context: &Context,
+        base_size: FontBaseSize,
+    ) -> Length {
+        match *self {
+            specified::NoCalcLength::Absolute(length) => length.to_computed_value(context),
+            specified::NoCalcLength::FontRelative(length) => {
+                length.to_computed_value(context, base_size)
+            },
+            specified::NoCalcLength::ViewportPercentage(length) => {
+                length.to_computed_value(context)
+            },
+            specified::NoCalcLength::ContainerRelative(length) => {
+                length.to_computed_value(context)
+            },
+            specified::NoCalcLength::ServoCharacterWidth(length) => {
+                length.to_computed_value(context.style().get_font().clone_font_size().computed_size())
+            },
+        }
+    }
+}
+
+impl ToComputedValue for specified::Length {
+    type ComputedValue = Length;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            specified::Length::NoCalc(l) => l.to_computed_value(context),
+            specified::Length::Calc(ref calc) => {
+                calc.to_computed_value(context).to_length().unwrap()
+            },
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        specified::Length::NoCalc(specified::NoCalcLength::from_computed_value(computed))
+    }
+}
+
+/// Some boilerplate to share between negative and non-negative
+/// length-percentage or auto.
+macro_rules! computed_length_percentage_or_auto {
+    ($inner:ty) => {
+        /// Returns the used value.
+        #[inline]
+        pub fn to_used_value(&self, percentage_basis: Au) -> Option<Au> {
+            match *self {
+                generics::GenericLengthPercentageOrAuto::Auto => None,
+                generics::GenericLengthPercentageOrAuto::LengthPercentage(ref lp) => {
+                    Some(lp.to_used_value(percentage_basis))
+                },
+            }
+        }
+
+        /// Returns true if the computed value is absolute 0 or 0%.
+        #[inline]
+        pub fn is_definitely_zero(&self) -> bool {
+            use crate::values::generics::length::LengthPercentageOrAuto::*;
+            match *self {
+                LengthPercentage(ref l) => l.is_definitely_zero(),
+                Auto => false,
+            }
+        }
+    };
+}
+
+/// A computed type for `<length-percentage> | auto`.
+pub type LengthPercentageOrAuto = generics::GenericLengthPercentageOrAuto<LengthPercentage>;
+
+impl LengthPercentageOrAuto {
+    /// Clamps the value to a non-negative value.
+    pub fn clamp_to_non_negative(self) -> Self {
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
+        match self {
+            LengthPercentage(l) => LengthPercentage(l.clamp_to_non_negative()),
+            Auto => Auto,
+        }
+    }
+
+    /// Convert to have a borrow inside the enum
+    pub fn as_ref(&self) -> generics::GenericLengthPercentageOrAuto<&LengthPercentage> {
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
+        match *self {
+            LengthPercentage(ref lp) => LengthPercentage(lp),
+            Auto => Auto,
+        }
+    }
+
+    computed_length_percentage_or_auto!(LengthPercentage);
+}
+
+impl generics::GenericLengthPercentageOrAuto<&LengthPercentage> {
+    /// Resolves the percentage.
+    #[inline]
+    pub fn percentage_relative_to(&self, basis: Length) -> LengthOrAuto {
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
+        match self {
+            LengthPercentage(length_percentage) => {
+                LengthPercentage(length_percentage.percentage_relative_to(basis))
+            },
+            Auto => Auto,
+        }
+    }
+
+    /// Maybe resolves the percentage.
+    #[inline]
+    pub fn maybe_percentage_relative_to(&self, basis: Option<Length>) -> LengthOrAuto {
+        use crate::values::generics::length::LengthPercentageOrAuto::*;
+        match self {
+            LengthPercentage(length_percentage) => length_percentage
+                .maybe_percentage_relative_to(basis)
+                .map_or(Auto, LengthPercentage),
+            Auto => Auto,
+        }
+    }
+}
+
+/// A wrapper of LengthPercentageOrAuto, whose value must be >= 0.
+pub type NonNegativeLengthPercentageOrAuto =
+    generics::GenericLengthPercentageOrAuto<NonNegativeLengthPercentage>;
+
+impl NonNegativeLengthPercentageOrAuto {
+    computed_length_percentage_or_auto!(NonNegativeLengthPercentage);
+}
+
+#[cfg(feature = "servo")]
+impl MaxSize {
+    /// Convert the computed value into used value.
+    #[inline]
+    pub fn to_used_value(&self, percentage_basis: Au) -> Option<Au> {
+        match *self {
+            GenericMaxSize::None => None,
+            GenericMaxSize::LengthPercentage(ref lp) => Some(lp.to_used_value(percentage_basis)),
+        }
+    }
+}
+
+impl Size {
+    /// Convert the computed value into used value.
+    #[inline]
+    #[cfg(feature = "servo")]
+    pub fn to_used_value(&self, percentage_basis: Au) -> Option<Au> {
+        match *self {
+            GenericSize::Auto => None,
+            GenericSize::LengthPercentage(ref lp) => Some(lp.to_used_value(percentage_basis)),
+        }
+    }
+
+    /// Returns true if the computed value is absolute 0 or 0%.
+    #[inline]
+    pub fn is_definitely_zero(&self) -> bool {
+        match *self {
+            GenericSize::Auto => false,
+            GenericSize::LengthPercentage(ref lp) => lp.is_definitely_zero(),
+            #[cfg(feature = "gecko")]
+            GenericSize::MinContent |
+            GenericSize::MaxContent |
+            GenericSize::FitContent |
+            GenericSize::MozAvailable |
+            GenericSize::FitContentFunction(_) => false,
+        }
+    }
+}
+
+/// The computed `<length>` value.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    Serialize,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct CSSPixelLength(CSSFloat);
+
+impl fmt::Debug for CSSPixelLength {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)?;
+        f.write_str(" px")
+    }
+}
+
+impl CSSPixelLength {
+    /// Return a new CSSPixelLength.
+    #[inline]
+    pub fn new(px: CSSFloat) -> Self {
+        CSSPixelLength(px)
+    }
+
+    /// Returns a normalized (NaN turned to zero) version of this length.
+    #[inline]
+    pub fn normalized(self) -> Self {
+        Self::new(crate::values::normalize(self.0))
+    }
+
+    /// Scale the length by a given amount.
+    #[inline]
+    pub fn scale_by(self, scale: CSSFloat) -> Self {
+        CSSPixelLength(self.0 * scale)
+    }
+
+    /// Return the containing pixel value.
+    #[inline]
+    pub fn px(self) -> CSSFloat {
+        self.0
+    }
+
+    /// Return the length with app_unit i32 type.
+    #[inline]
+    pub fn to_i32_au(self) -> i32 {
+        Au::from(self).0
+    }
+
+    /// Return the absolute value of this length.
+    #[inline]
+    pub fn abs(self) -> Self {
+        CSSPixelLength::new(self.0.abs())
+    }
+
+    /// Return the clamped value of this length.
+    #[inline]
+    pub fn clamp_to_non_negative(self) -> Self {
+        CSSPixelLength::new(self.0.max(0.))
+    }
+
+    /// Returns the minimum between `self` and `other`.
+    #[inline]
+    pub fn min(self, other: Self) -> Self {
+        CSSPixelLength::new(self.0.min(other.0))
+    }
+
+    /// Returns the maximum between `self` and `other`.
+    #[inline]
+    pub fn max(self, other: Self) -> Self {
+        CSSPixelLength::new(self.0.max(other.0))
+    }
+
+    /// Sets `self` to the maximum between `self` and `other`.
+    #[inline]
+    pub fn max_assign(&mut self, other: Self) {
+        *self = self.max(other);
+    }
+
+    /// Clamp the value to a lower bound and an optional upper bound.
+    ///
+    /// Can be used for example with `min-width` and `max-width`.
+    #[inline]
+    pub fn clamp_between_extremums(self, min_size: Self, max_size: Option<Self>) -> Self {
+        self.clamp_below_max(max_size).max(min_size)
+    }
+
+    /// Clamp the value to an optional upper bound.
+    ///
+    /// Can be used for example with `max-width`.
+    #[inline]
+    pub fn clamp_below_max(self, max_size: Option<Self>) -> Self {
+        match max_size {
+            None => self,
+            Some(max_size) => self.min(max_size),
+        }
+    }
+}
+
+impl num_traits::Zero for CSSPixelLength {
+    fn zero() -> Self {
+        CSSPixelLength::new(0.)
+    }
+
+    fn is_zero(&self) -> bool {
+        self.px() == 0.
+    }
+}
+
+impl ToCss for CSSPixelLength {
+    #[inline]
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0.to_css(dest)?;
+        dest.write_str("px")
+    }
+}
+
+impl std::iter::Sum for CSSPixelLength {
+    fn sum<I: Iterator<Item = Self>>(iter: I) -> Self {
+        iter.fold(Length::zero(), Add::add)
+    }
+}
+
+impl Add for CSSPixelLength {
+    type Output = Self;
+
+    #[inline]
+    fn add(self, other: Self) -> Self {
+        Self::new(self.px() + other.px())
+    }
+}
+
+impl AddAssign for CSSPixelLength {
+    #[inline]
+    fn add_assign(&mut self, other: Self) {
+        self.0 += other.0;
+    }
+}
+
+impl Div for CSSPixelLength {
+    type Output = CSSFloat;
+
+    #[inline]
+    fn div(self, other: Self) -> CSSFloat {
+        self.px() / other.px()
+    }
+}
+
+impl Div<CSSFloat> for CSSPixelLength {
+    type Output = Self;
+
+    #[inline]
+    fn div(self, other: CSSFloat) -> Self {
+        Self::new(self.px() / other)
+    }
+}
+
+impl MulAssign<CSSFloat> for CSSPixelLength {
+    #[inline]
+    fn mul_assign(&mut self, other: CSSFloat) {
+        self.0 *= other;
+    }
+}
+
+impl Mul<CSSFloat> for CSSPixelLength {
+    type Output = Self;
+
+    #[inline]
+    fn mul(self, other: CSSFloat) -> Self {
+        Self::new(self.px() * other)
+    }
+}
+
+impl Neg for CSSPixelLength {
+    type Output = Self;
+
+    #[inline]
+    fn neg(self) -> Self {
+        CSSPixelLength::new(-self.0)
+    }
+}
+
+impl Sub for CSSPixelLength {
+    type Output = Self;
+
+    #[inline]
+    fn sub(self, other: Self) -> Self {
+        Self::new(self.px() - other.px())
+    }
+}
+
+impl From<CSSPixelLength> for Au {
+    #[inline]
+    fn from(len: CSSPixelLength) -> Self {
+        Au::from_f32_px(len.0)
+    }
+}
+
+impl From<Au> for CSSPixelLength {
+    #[inline]
+    fn from(len: Au) -> Self {
+        CSSPixelLength::new(len.to_f32_px())
+    }
+}
+
+impl From<CSSPixelLength> for euclid::Length<CSSFloat, CSSPixel> {
+    #[inline]
+    fn from(length: CSSPixelLength) -> Self {
+        Self::new(length.0)
+    }
+}
+
+/// An alias of computed `<length>` value.
+pub type Length = CSSPixelLength;
+
+/// Either a computed `<length>` or the `auto` keyword.
+pub type LengthOrAuto = generics::GenericLengthPercentageOrAuto<Length>;
+
+/// Either a non-negative `<length>` or the `auto` keyword.
+pub type NonNegativeLengthOrAuto = generics::GenericLengthPercentageOrAuto<NonNegativeLength>;
+
+/// Either a computed `<length>` or a `<number>` value.
+pub type LengthOrNumber = GenericLengthOrNumber<Length, Number>;
+
+/// A wrapper of Length, whose value must be >= 0.
+pub type NonNegativeLength = NonNegative<Length>;
+
+impl ToAnimatedValue for NonNegativeLength {
+    type AnimatedValue = Length;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        NonNegativeLength::new(animated.px().max(0.))
+    }
+}
+
+impl NonNegativeLength {
+    /// Create a NonNegativeLength.
+    #[inline]
+    pub fn new(px: CSSFloat) -> Self {
+        NonNegative(Length::new(px.max(0.)))
+    }
+
+    /// Return the pixel value of |NonNegativeLength|.
+    #[inline]
+    pub fn px(&self) -> CSSFloat {
+        self.0.px()
+    }
+
+    #[inline]
+    /// Ensures it is non negative
+    pub fn clamp(self) -> Self {
+        if (self.0).0 < 0. {
+            Self::zero()
+        } else {
+            self
+        }
+    }
+}
+
+impl From<Length> for NonNegativeLength {
+    #[inline]
+    fn from(len: Length) -> Self {
+        NonNegative(len)
+    }
+}
+
+impl From<Au> for NonNegativeLength {
+    #[inline]
+    fn from(au: Au) -> Self {
+        NonNegative(au.into())
+    }
+}
+
+impl From<NonNegativeLength> for Au {
+    #[inline]
+    fn from(non_negative_len: NonNegativeLength) -> Self {
+        Au::from(non_negative_len.0)
+    }
+}
+
+/// Either a computed NonNegativeLengthPercentage or the `normal` keyword.
+pub type NonNegativeLengthPercentageOrNormal =
+    GenericLengthPercentageOrNormal<NonNegativeLengthPercentage>;
+
+/// Either a non-negative `<length>` or a `<number>`.
+pub type NonNegativeLengthOrNumber = GenericLengthOrNumber<NonNegativeLength, NonNegativeNumber>;
+
+/// A computed value for `min-width`, `min-height`, `width` or `height` property.
+pub type Size = GenericSize<NonNegativeLengthPercentage>;
+
+/// A computed value for `max-width` or `min-height` property.
+pub type MaxSize = GenericMaxSize<NonNegativeLengthPercentage>;
diff --git a/servo/components/style/values/computed/length_percentage.rs b/servo/components/style/values/computed/length_percentage.rs
new file mode 100644
index 0000000000..0afa1014d9
--- /dev/null
+++ b/servo/components/style/values/computed/length_percentage.rs
@@ -0,0 +1,895 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! `<length-percentage>` computed values, and related ones.
+//!
+//! The over-all design is a tagged pointer, with the lower bits of the pointer
+//! being non-zero if it is a non-calc value.
+//!
+//! It is expected to take 64 bits both in x86 and x86-64. This is implemented
+//! as a `union`, with 4 different variants:
+//!
+//!  * The length and percentage variants have a { tag, f32 } (effectively)
+//!    layout. The tag has to overlap with the lower 2 bits of the calc variant.
+//!
+//!  * The `calc()` variant is a { tag, pointer } in x86 (so same as the
+//!    others), or just a { pointer } in x86-64 (so that the two bits of the tag
+//!    can be obtained from the lower bits of the pointer).
+//!
+//!  * There's a `tag` variant just to make clear when only the tag is intended
+//!    to be read. Note that the tag needs to be masked always by `TAG_MASK`, to
+//!    deal with the pointer variant in x86-64.
+//!
+//! The assertions in the constructor methods ensure that the tag getter matches
+//! our expectations.
+
+use super::{Context, Length, Percentage, ToComputedValue};
+use crate::values::animated::{Animate, Procedure, ToAnimatedValue, ToAnimatedZero};
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::{calc, NonNegative};
+use crate::values::specified::length::FontBaseSize;
+use crate::values::{specified, CSSFloat};
+use crate::{Zero, ZeroNoPercent};
+use app_units::Au;
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps};
+use serde::{Deserialize, Serialize};
+use std::borrow::Cow;
+use std::fmt::{self, Write};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ToCss};
+
+#[doc(hidden)]
+#[derive(Clone, Copy)]
+#[repr(C)]
+pub struct LengthVariant {
+    tag: u8,
+    length: Length,
+}
+
+#[doc(hidden)]
+#[derive(Clone, Copy)]
+#[repr(C)]
+pub struct PercentageVariant {
+    tag: u8,
+    percentage: Percentage,
+}
+
+// NOTE(emilio): cbindgen only understands the #[cfg] on the top level
+// definition.
+#[doc(hidden)]
+#[derive(Clone, Copy)]
+#[repr(C)]
+#[cfg(target_pointer_width = "32")]
+pub struct CalcVariant {
+    tag: u8,
+    ptr: *mut CalcLengthPercentage,
+}
+
+#[doc(hidden)]
+#[derive(Clone, Copy)]
+#[repr(C)]
+#[cfg(target_pointer_width = "64")]
+pub struct CalcVariant {
+    ptr: usize, // In little-endian byte order
+}
+
+// `CalcLengthPercentage` is `Send + Sync` as asserted below.
+unsafe impl Send for CalcVariant {}
+unsafe impl Sync for CalcVariant {}
+
+#[doc(hidden)]
+#[derive(Clone, Copy)]
+#[repr(C)]
+pub struct TagVariant {
+    tag: u8,
+}
+
+/// A `<length-percentage>` value. This can be either a `<length>`, a
+/// `<percentage>`, or a combination of both via `calc()`.
+///
+/// cbindgen:private-default-tagged-enum-constructor=false
+/// cbindgen:derive-mut-casts=true
+///
+/// https://drafts.csswg.org/css-values-4/#typedef-length-percentage
+///
+/// The tag is stored in the lower two bits.
+///
+/// We need to use a struct instead of the union directly because unions with
+/// Drop implementations are unstable, looks like.
+///
+/// Also we need the union and the variants to be `pub` (even though the member
+/// is private) so that cbindgen generates it. They're not part of the public
+/// API otherwise.
+#[repr(transparent)]
+pub struct LengthPercentage(LengthPercentageUnion);
+
+#[doc(hidden)]
+#[repr(C)]
+pub union LengthPercentageUnion {
+    length: LengthVariant,
+    percentage: PercentageVariant,
+    calc: CalcVariant,
+    tag: TagVariant,
+}
+
+impl LengthPercentageUnion {
+    #[doc(hidden)] // Need to be public so that cbindgen generates it.
+    pub const TAG_CALC: u8 = 0;
+    #[doc(hidden)]
+    pub const TAG_LENGTH: u8 = 1;
+    #[doc(hidden)]
+    pub const TAG_PERCENTAGE: u8 = 2;
+    #[doc(hidden)]
+    pub const TAG_MASK: u8 = 0b11;
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+#[repr(u8)]
+enum Tag {
+    Calc = LengthPercentageUnion::TAG_CALC,
+    Length = LengthPercentageUnion::TAG_LENGTH,
+    Percentage = LengthPercentageUnion::TAG_PERCENTAGE,
+}
+
+// All the members should be 64 bits, even in 32-bit builds.
+#[allow(unused)]
+unsafe fn static_assert() {
+    fn assert_send_and_sync<T: Send + Sync>() {}
+    std::mem::transmute::<u64, LengthVariant>(0u64);
+    std::mem::transmute::<u64, PercentageVariant>(0u64);
+    std::mem::transmute::<u64, CalcVariant>(0u64);
+    std::mem::transmute::<u64, LengthPercentage>(0u64);
+    assert_send_and_sync::<LengthVariant>();
+    assert_send_and_sync::<PercentageVariant>();
+    assert_send_and_sync::<CalcLengthPercentage>();
+}
+
+impl Drop for LengthPercentage {
+    fn drop(&mut self) {
+        if self.tag() == Tag::Calc {
+            let _ = unsafe { Box::from_raw(self.calc_ptr()) };
+        }
+    }
+}
+
+impl MallocSizeOf for LengthPercentage {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        match self.unpack() {
+            Unpacked::Length(..) | Unpacked::Percentage(..) => 0,
+            Unpacked::Calc(c) => unsafe { ops.malloc_size_of(c) },
+        }
+    }
+}
+
+/// An unpacked `<length-percentage>` that borrows the `calc()` variant.
+#[derive(Clone, Debug, PartialEq, ToCss)]
+enum Unpacked<'a> {
+    Calc(&'a CalcLengthPercentage),
+    Length(Length),
+    Percentage(Percentage),
+}
+
+/// An unpacked `<length-percentage>` that mutably borrows the `calc()` variant.
+enum UnpackedMut<'a> {
+    Calc(&'a mut CalcLengthPercentage),
+    Length(Length),
+    Percentage(Percentage),
+}
+
+/// An unpacked `<length-percentage>` that owns the `calc()` variant, for
+/// serialization purposes.
+#[derive(Deserialize, PartialEq, Serialize)]
+enum Serializable {
+    Calc(CalcLengthPercentage),
+    Length(Length),
+    Percentage(Percentage),
+}
+
+impl LengthPercentage {
+    /// 1px length value for SVG defaults
+    #[inline]
+    pub fn one() -> Self {
+        Self::new_length(Length::new(1.))
+    }
+
+    /// 0%
+    #[inline]
+    pub fn zero_percent() -> Self {
+        Self::new_percent(Percentage::zero())
+    }
+
+    fn to_calc_node(&self) -> Cow<CalcNode> {
+        match self.unpack() {
+            Unpacked::Length(l) => Cow::Owned(CalcNode::Leaf(CalcLengthPercentageLeaf::Length(l))),
+            Unpacked::Percentage(p) => {
+                Cow::Owned(CalcNode::Leaf(CalcLengthPercentageLeaf::Percentage(p)))
+            },
+            Unpacked::Calc(p) => Cow::Borrowed(&p.node),
+        }
+    }
+
+    /// Constructs a length value.
+    #[inline]
+    pub fn new_length(length: Length) -> Self {
+        let length = Self(LengthPercentageUnion {
+            length: LengthVariant {
+                tag: LengthPercentageUnion::TAG_LENGTH,
+                length,
+            },
+        });
+        debug_assert_eq!(length.tag(), Tag::Length);
+        length
+    }
+
+    /// Constructs a percentage value.
+    #[inline]
+    pub fn new_percent(percentage: Percentage) -> Self {
+        let percent = Self(LengthPercentageUnion {
+            percentage: PercentageVariant {
+                tag: LengthPercentageUnion::TAG_PERCENTAGE,
+                percentage,
+            },
+        });
+        debug_assert_eq!(percent.tag(), Tag::Percentage);
+        percent
+    }
+
+    /// Given a `LengthPercentage` value `v`, construct the value representing
+    /// `calc(100% - v)`.
+    pub fn hundred_percent_minus(v: Self, clamping_mode: AllowedNumericType) -> Self {
+        // TODO: This could in theory take ownership of the calc node in `v` if
+        // possible instead of cloning.
+        let mut node = v.to_calc_node().into_owned();
+        node.negate();
+
+        let new_node = CalcNode::Sum(
+            vec![
+                CalcNode::Leaf(CalcLengthPercentageLeaf::Percentage(Percentage::hundred())),
+                node,
+            ]
+            .into(),
+        );
+
+        Self::new_calc(new_node, clamping_mode)
+    }
+
+    /// Constructs a `calc()` value.
+    #[inline]
+    pub fn new_calc(mut node: CalcNode, clamping_mode: AllowedNumericType) -> Self {
+        node.simplify_and_sort();
+
+        match node {
+            CalcNode::Leaf(l) => {
+                return match l {
+                    CalcLengthPercentageLeaf::Length(l) => {
+                        Self::new_length(Length::new(clamping_mode.clamp(l.px())).normalized())
+                    },
+                    CalcLengthPercentageLeaf::Percentage(p) => Self::new_percent(Percentage(
+                        clamping_mode.clamp(crate::values::normalize(p.0)),
+                    )),
+                }
+            },
+            _ => Self::new_calc_unchecked(Box::new(CalcLengthPercentage {
+                clamping_mode,
+                node,
+            })),
+        }
+    }
+
+    /// Private version of new_calc() that constructs a calc() variant without
+    /// checking.
+    fn new_calc_unchecked(calc: Box<CalcLengthPercentage>) -> Self {
+        let ptr = Box::into_raw(calc);
+
+        #[cfg(target_pointer_width = "32")]
+        let calc = CalcVariant {
+            tag: LengthPercentageUnion::TAG_CALC,
+            ptr,
+        };
+
+        #[cfg(target_pointer_width = "64")]
+        let calc = CalcVariant {
+            #[cfg(target_endian = "little")]
+            ptr: ptr as usize,
+            #[cfg(target_endian = "big")]
+            ptr: (ptr as usize).swap_bytes(),
+        };
+
+        let calc = Self(LengthPercentageUnion { calc });
+        debug_assert_eq!(calc.tag(), Tag::Calc);
+        calc
+    }
+
+    #[inline]
+    fn tag(&self) -> Tag {
+        match unsafe { self.0.tag.tag & LengthPercentageUnion::TAG_MASK } {
+            LengthPercentageUnion::TAG_CALC => Tag::Calc,
+            LengthPercentageUnion::TAG_LENGTH => Tag::Length,
+            LengthPercentageUnion::TAG_PERCENTAGE => Tag::Percentage,
+            _ => unsafe { debug_unreachable!("Bogus tag?") },
+        }
+    }
+
+    #[inline]
+    fn unpack_mut<'a>(&'a mut self) -> UnpackedMut<'a> {
+        unsafe {
+            match self.tag() {
+                Tag::Calc => UnpackedMut::Calc(&mut *self.calc_ptr()),
+                Tag::Length => UnpackedMut::Length(self.0.length.length),
+                Tag::Percentage => UnpackedMut::Percentage(self.0.percentage.percentage),
+            }
+        }
+    }
+
+    #[inline]
+    fn unpack<'a>(&'a self) -> Unpacked<'a> {
+        unsafe {
+            match self.tag() {
+                Tag::Calc => Unpacked::Calc(&*self.calc_ptr()),
+                Tag::Length => Unpacked::Length(self.0.length.length),
+                Tag::Percentage => Unpacked::Percentage(self.0.percentage.percentage),
+            }
+        }
+    }
+
+    #[inline]
+    unsafe fn calc_ptr(&self) -> *mut CalcLengthPercentage {
+        #[cfg(not(all(target_endian = "big", target_pointer_width = "64")))]
+        {
+            self.0.calc.ptr as *mut _
+        }
+        #[cfg(all(target_endian = "big", target_pointer_width = "64"))]
+        {
+            self.0.calc.ptr.swap_bytes() as *mut _
+        }
+    }
+
+    #[inline]
+    fn to_serializable(&self) -> Serializable {
+        match self.unpack() {
+            Unpacked::Calc(c) => Serializable::Calc(c.clone()),
+            Unpacked::Length(l) => Serializable::Length(l),
+            Unpacked::Percentage(p) => Serializable::Percentage(p),
+        }
+    }
+
+    #[inline]
+    fn from_serializable(s: Serializable) -> Self {
+        match s {
+            Serializable::Calc(c) => Self::new_calc_unchecked(Box::new(c)),
+            Serializable::Length(l) => Self::new_length(l),
+            Serializable::Percentage(p) => Self::new_percent(p),
+        }
+    }
+
+    /// Returns true if the computed value is absolute 0 or 0%.
+    #[inline]
+    pub fn is_definitely_zero(&self) -> bool {
+        match self.unpack() {
+            Unpacked::Length(l) => l.px() == 0.0,
+            Unpacked::Percentage(p) => p.0 == 0.0,
+            Unpacked::Calc(..) => false,
+        }
+    }
+
+    /// Resolves the percentage.
+    #[inline]
+    pub fn resolve(&self, basis: Length) -> Length {
+        match self.unpack() {
+            Unpacked::Length(l) => l,
+            Unpacked::Percentage(p) => (basis * p.0).normalized(),
+            Unpacked::Calc(ref c) => c.resolve(basis),
+        }
+    }
+
+    /// Resolves the percentage. Just an alias of resolve().
+    #[inline]
+    pub fn percentage_relative_to(&self, basis: Length) -> Length {
+        self.resolve(basis)
+    }
+
+    /// Return whether there's any percentage in this value.
+    #[inline]
+    pub fn has_percentage(&self) -> bool {
+        match self.unpack() {
+            Unpacked::Length(..) => false,
+            Unpacked::Percentage(..) | Unpacked::Calc(..) => true,
+        }
+    }
+
+    /// Converts to a `<length>` if possible.
+    pub fn to_length(&self) -> Option<Length> {
+        match self.unpack() {
+            Unpacked::Length(l) => Some(l),
+            Unpacked::Percentage(..) | Unpacked::Calc(..) => {
+                debug_assert!(self.has_percentage());
+                return None;
+            },
+        }
+    }
+
+    /// Converts to a `<percentage>` if possible.
+    #[inline]
+    pub fn to_percentage(&self) -> Option<Percentage> {
+        match self.unpack() {
+            Unpacked::Percentage(p) => Some(p),
+            Unpacked::Length(..) | Unpacked::Calc(..) => None,
+        }
+    }
+
+    /// Returns the used value.
+    #[inline]
+    pub fn to_used_value(&self, containing_length: Au) -> Au {
+        Au::from(self.to_pixel_length(containing_length))
+    }
+
+    /// Returns the used value as CSSPixelLength.
+    #[inline]
+    pub fn to_pixel_length(&self, containing_length: Au) -> Length {
+        self.resolve(containing_length.into())
+    }
+
+    /// Convert the computed value into used value.
+    #[inline]
+    pub fn maybe_to_used_value(&self, container_len: Option<Length>) -> Option<Au> {
+        self.maybe_percentage_relative_to(container_len)
+            .map(Au::from)
+    }
+
+    /// If there are special rules for computing percentages in a value (e.g.
+    /// the height property), they apply whenever a calc() expression contains
+    /// percentages.
+    pub fn maybe_percentage_relative_to(&self, container_len: Option<Length>) -> Option<Length> {
+        if let Unpacked::Length(l) = self.unpack() {
+            return Some(l);
+        }
+        Some(self.resolve(container_len?))
+    }
+
+    /// Returns the clamped non-negative values.
+    #[inline]
+    pub fn clamp_to_non_negative(mut self) -> Self {
+        match self.unpack_mut() {
+            UnpackedMut::Length(l) => Self::new_length(l.clamp_to_non_negative()),
+            UnpackedMut::Percentage(p) => Self::new_percent(p.clamp_to_non_negative()),
+            UnpackedMut::Calc(ref mut c) => {
+                c.clamping_mode = AllowedNumericType::NonNegative;
+                self
+            },
+        }
+    }
+}
+
+impl PartialEq for LengthPercentage {
+    fn eq(&self, other: &Self) -> bool {
+        self.unpack() == other.unpack()
+    }
+}
+
+impl fmt::Debug for LengthPercentage {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        self.unpack().fmt(formatter)
+    }
+}
+
+impl ToAnimatedZero for LengthPercentage {
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(match self.unpack() {
+            Unpacked::Length(l) => Self::new_length(l.to_animated_zero()?),
+            Unpacked::Percentage(p) => Self::new_percent(p.to_animated_zero()?),
+            Unpacked::Calc(c) => Self::new_calc_unchecked(Box::new(c.to_animated_zero()?)),
+        })
+    }
+}
+
+impl Clone for LengthPercentage {
+    fn clone(&self) -> Self {
+        match self.unpack() {
+            Unpacked::Length(l) => Self::new_length(l),
+            Unpacked::Percentage(p) => Self::new_percent(p),
+            Unpacked::Calc(c) => Self::new_calc_unchecked(Box::new(c.clone())),
+        }
+    }
+}
+
+impl ToComputedValue for specified::LengthPercentage {
+    type ComputedValue = LengthPercentage;
+
+    fn to_computed_value(&self, context: &Context) -> LengthPercentage {
+        match *self {
+            specified::LengthPercentage::Length(ref value) => {
+                LengthPercentage::new_length(value.to_computed_value(context))
+            },
+            specified::LengthPercentage::Percentage(value) => LengthPercentage::new_percent(value),
+            specified::LengthPercentage::Calc(ref calc) => (**calc).to_computed_value(context),
+        }
+    }
+
+    fn from_computed_value(computed: &LengthPercentage) -> Self {
+        match computed.unpack() {
+            Unpacked::Length(ref l) => {
+                specified::LengthPercentage::Length(ToComputedValue::from_computed_value(l))
+            },
+            Unpacked::Percentage(p) => specified::LengthPercentage::Percentage(p),
+            Unpacked::Calc(c) => {
+                // We simplify before constructing the LengthPercentage if
+                // needed, so this is always fine.
+                specified::LengthPercentage::Calc(Box::new(
+                    specified::CalcLengthPercentage::from_computed_value(c),
+                ))
+            },
+        }
+    }
+}
+
+impl ComputeSquaredDistance for LengthPercentage {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        // A somewhat arbitrary base, it doesn't really make sense to mix
+        // lengths with percentages, but we can't do much better here, and this
+        // ensures that the distance between length-only and percentage-only
+        // lengths makes sense.
+        let basis = Length::new(100.);
+        self.resolve(basis)
+            .compute_squared_distance(&other.resolve(basis))
+    }
+}
+
+impl ToCss for LengthPercentage {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.unpack().to_css(dest)
+    }
+}
+
+impl Zero for LengthPercentage {
+    fn zero() -> Self {
+        LengthPercentage::new_length(Length::zero())
+    }
+
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.is_definitely_zero()
+    }
+}
+
+impl ZeroNoPercent for LengthPercentage {
+    #[inline]
+    fn is_zero_no_percent(&self) -> bool {
+        self.is_definitely_zero() && !self.has_percentage()
+    }
+}
+
+impl Serialize for LengthPercentage {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        self.to_serializable().serialize(serializer)
+    }
+}
+
+impl<'de> Deserialize<'de> for LengthPercentage {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        Ok(Self::from_serializable(Serializable::deserialize(
+            deserializer,
+        )?))
+    }
+}
+
+/// The leaves of a `<length-percentage>` calc expression.
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+)]
+#[allow(missing_docs)]
+#[repr(u8)]
+pub enum CalcLengthPercentageLeaf {
+    Length(Length),
+    Percentage(Percentage),
+}
+
+impl CalcLengthPercentageLeaf {
+    fn is_zero_length(&self) -> bool {
+        match *self {
+            Self::Length(ref l) => l.is_zero(),
+            Self::Percentage(..) => false,
+        }
+    }
+}
+
+impl PartialOrd for CalcLengthPercentageLeaf {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        use self::CalcLengthPercentageLeaf::*;
+        // NOTE: Percentages can't be compared reasonably here because the
+        // percentage basis might be negative, see bug 1709018.
+        match (self, other) {
+            (&Length(ref one), &Length(ref other)) => one.partial_cmp(other),
+            _ => None,
+        }
+    }
+}
+
+impl calc::CalcNodeLeaf for CalcLengthPercentageLeaf {
+    fn unitless_value(&self) -> f32 {
+        match *self {
+            Self::Length(ref l) => l.px(),
+            Self::Percentage(ref p) => p.0,
+        }
+    }
+
+    fn try_sum_in_place(&mut self, other: &Self) -> Result<(), ()> {
+        use self::CalcLengthPercentageLeaf::*;
+
+        // 0px plus anything else is equal to the right hand side.
+        if self.is_zero_length() {
+            *self = other.clone();
+            return Ok(());
+        }
+
+        if other.is_zero_length() {
+            return Ok(());
+        }
+
+        match (self, other) {
+            (&mut Length(ref mut one), &Length(ref other)) => {
+                *one += *other;
+            },
+            (&mut Percentage(ref mut one), &Percentage(ref other)) => {
+                one.0 += other.0;
+            },
+            _ => return Err(()),
+        }
+
+        Ok(())
+    }
+
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        match (self, other) {
+            (
+                &CalcLengthPercentageLeaf::Length(ref one),
+                &CalcLengthPercentageLeaf::Length(ref other),
+            ) => Ok(CalcLengthPercentageLeaf::Length(Length::new(op(
+                one.px(),
+                other.px(),
+            )))),
+            (
+                &CalcLengthPercentageLeaf::Percentage(one),
+                &CalcLengthPercentageLeaf::Percentage(other),
+            ) => Ok(CalcLengthPercentageLeaf::Percentage(Percentage(op(
+                one.0, other.0,
+            )))),
+            _ => Err(()),
+        }
+    }
+
+    fn mul_by(&mut self, scalar: f32) {
+        match *self {
+            Self::Length(ref mut l) => *l = *l * scalar,
+            Self::Percentage(ref mut p) => p.0 *= scalar,
+        }
+    }
+
+    fn simplify(&mut self) {}
+
+    fn sort_key(&self) -> calc::SortKey {
+        match *self {
+            Self::Length(..) => calc::SortKey::Px,
+            Self::Percentage(..) => calc::SortKey::Percentage,
+        }
+    }
+}
+
+/// The computed version of a calc() node for `<length-percentage>` values.
+pub type CalcNode = calc::GenericCalcNode<CalcLengthPercentageLeaf>;
+
+/// The representation of a calc() function with mixed lengths and percentages.
+#[derive(
+    Clone, Debug, Deserialize, MallocSizeOf, Serialize, ToAnimatedZero, ToResolvedValue, ToCss,
+)]
+#[repr(C)]
+pub struct CalcLengthPercentage {
+    #[animation(constant)]
+    #[css(skip)]
+    clamping_mode: AllowedNumericType,
+    node: CalcNode,
+}
+
+impl CalcLengthPercentage {
+    /// Resolves the percentage.
+    #[inline]
+    fn resolve(&self, basis: Length) -> Length {
+        // unwrap() is fine because the conversion below is infallible.
+        let px = self
+            .node
+            .resolve(|l| {
+                Ok(match *l {
+                    CalcLengthPercentageLeaf::Length(l) => l.px(),
+                    CalcLengthPercentageLeaf::Percentage(ref p) => basis.px() * p.0,
+                })
+            })
+            .unwrap();
+        Length::new(self.clamping_mode.clamp(px)).normalized()
+    }
+}
+
+// NOTE(emilio): We don't compare `clamping_mode` since we want to preserve the
+// invariant that `from_computed_value(length).to_computed_value(..) == length`.
+//
+// Right now for e.g. a non-negative length, we set clamping_mode to `All`
+// unconditionally for non-calc values, and to `NonNegative` for calc.
+//
+// If we determine that it's sound, from_computed_value() can generate an
+// absolute length, which then would get `All` as the clamping mode.
+//
+// We may want to just eagerly-detect whether we can clamp in
+// `LengthPercentage::new` and switch to `AllowedNumericType::NonNegative` then,
+// maybe.
+impl PartialEq for CalcLengthPercentage {
+    fn eq(&self, other: &Self) -> bool {
+        self.node == other.node
+    }
+}
+
+impl specified::CalcLengthPercentage {
+    /// Compute the value, zooming any absolute units by the zoom function.
+    fn to_computed_value_with_zoom<F>(
+        &self,
+        context: &Context,
+        zoom_fn: F,
+        base_size: FontBaseSize,
+    ) -> LengthPercentage
+    where
+        F: Fn(Length) -> Length,
+    {
+        use crate::values::specified::calc::Leaf;
+
+        let node = self.node.map_leaves(|leaf| match *leaf {
+            Leaf::Percentage(p) => CalcLengthPercentageLeaf::Percentage(Percentage(p)),
+            Leaf::Length(l) => CalcLengthPercentageLeaf::Length({
+                let result = l.to_computed_value_with_base_size(context, base_size);
+                if l.should_zoom_text() {
+                    zoom_fn(result)
+                } else {
+                    result
+                }
+            }),
+            Leaf::Number(..) | Leaf::Angle(..) | Leaf::Time(..) => {
+                unreachable!("Shouldn't have parsed")
+            },
+        });
+
+        LengthPercentage::new_calc(node, self.clamping_mode)
+    }
+
+    /// Compute font-size or line-height taking into account text-zoom if necessary.
+    pub fn to_computed_value_zoomed(
+        &self,
+        context: &Context,
+        base_size: FontBaseSize,
+    ) -> LengthPercentage {
+        self.to_computed_value_with_zoom(context, |abs| context.maybe_zoom_text(abs), base_size)
+    }
+
+    /// Compute the value into pixel length as CSSFloat without context,
+    /// so it returns Err(()) if there is any non-absolute unit.
+    pub fn to_computed_pixel_length_without_context(&self) -> Result<CSSFloat, ()> {
+        use crate::values::specified::calc::Leaf;
+        use crate::values::specified::length::NoCalcLength;
+
+        // Simplification should've turned this into an absolute length,
+        // otherwise it wouldn't have been able to.
+        match self.node {
+            calc::CalcNode::Leaf(Leaf::Length(NoCalcLength::Absolute(ref l))) => Ok(l.to_px()),
+            _ => Err(()),
+        }
+    }
+
+    /// Compute the calc using the current font-size (and without text-zoom).
+    pub fn to_computed_value(&self, context: &Context) -> LengthPercentage {
+        self.to_computed_value_with_zoom(context, |abs| abs, FontBaseSize::CurrentStyle)
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &CalcLengthPercentage) -> Self {
+        use crate::values::specified::calc::Leaf;
+        use crate::values::specified::length::NoCalcLength;
+
+        specified::CalcLengthPercentage {
+            clamping_mode: computed.clamping_mode,
+            node: computed.node.map_leaves(|l| match l {
+                CalcLengthPercentageLeaf::Length(ref l) => {
+                    Leaf::Length(NoCalcLength::from_px(l.px()))
+                },
+                CalcLengthPercentageLeaf::Percentage(ref p) => Leaf::Percentage(p.0),
+            }),
+        }
+    }
+}
+
+/// https://drafts.csswg.org/css-transitions/#animtype-lpcalc
+/// https://drafts.csswg.org/css-values-4/#combine-math
+/// https://drafts.csswg.org/css-values-4/#combine-mixed
+impl Animate for LengthPercentage {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        Ok(match (self.unpack(), other.unpack()) {
+            (Unpacked::Length(one), Unpacked::Length(other)) => {
+                Self::new_length(one.animate(&other, procedure)?)
+            },
+            (Unpacked::Percentage(one), Unpacked::Percentage(other)) => {
+                Self::new_percent(one.animate(&other, procedure)?)
+            },
+            _ => {
+                let mut one = self.to_calc_node().into_owned();
+                let mut other = other.to_calc_node().into_owned();
+                let (l, r) = procedure.weights();
+
+                one.mul_by(l as f32);
+                other.mul_by(r as f32);
+
+                Self::new_calc(
+                    CalcNode::Sum(vec![one, other].into()),
+                    AllowedNumericType::All,
+                )
+            },
+        })
+    }
+}
+
+/// A wrapper of LengthPercentage, whose value must be >= 0.
+pub type NonNegativeLengthPercentage = NonNegative<LengthPercentage>;
+
+impl ToAnimatedValue for NonNegativeLengthPercentage {
+    type AnimatedValue = LengthPercentage;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        NonNegative(animated.clamp_to_non_negative())
+    }
+}
+
+impl NonNegativeLengthPercentage {
+    /// Returns true if the computed value is absolute 0 or 0%.
+    #[inline]
+    pub fn is_definitely_zero(&self) -> bool {
+        self.0.is_definitely_zero()
+    }
+
+    /// Returns the used value.
+    #[inline]
+    pub fn to_used_value(&self, containing_length: Au) -> Au {
+        let resolved = self.0.to_used_value(containing_length);
+        std::cmp::max(resolved, Au(0))
+    }
+
+    /// Convert the computed value into used value.
+    #[inline]
+    pub fn maybe_to_used_value(&self, containing_length: Option<Au>) -> Option<Au> {
+        let resolved = self
+            .0
+            .maybe_to_used_value(containing_length.map(|v| v.into()))?;
+        Some(std::cmp::max(resolved, Au(0)))
+    }
+}
diff --git a/servo/components/style/values/computed/list.rs b/servo/components/style/values/computed/list.rs
new file mode 100644
index 0000000000..3e5d1eb220
--- /dev/null
+++ b/servo/components/style/values/computed/list.rs
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! `list` computed values.
+
+#[cfg(feature = "gecko")]
+pub use crate::values::specified::list::ListStyleType;
+pub use crate::values::specified::list::Quotes;
+
+impl Quotes {
+    /// Initial value for `quotes`.
+    #[inline]
+    pub fn get_initial_value() -> Quotes {
+        Quotes::Auto
+    }
+}
diff --git a/servo/components/style/values/computed/mod.rs b/servo/components/style/values/computed/mod.rs
new file mode 100644
index 0000000000..dac4c4f246
--- /dev/null
+++ b/servo/components/style/values/computed/mod.rs
@@ -0,0 +1,996 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed values.
+
+use self::transform::DirectionVector;
+use super::animated::ToAnimatedValue;
+use super::generics::grid::GridTemplateComponent as GenericGridTemplateComponent;
+use super::generics::grid::ImplicitGridTracks as GenericImplicitGridTracks;
+use super::generics::grid::{GenericGridLine, GenericTrackBreadth};
+use super::generics::grid::{GenericTrackSize, TrackList as GenericTrackList};
+use super::generics::transform::IsParallelTo;
+use super::generics::{self, GreaterThanOrEqualToOne, NonNegative, ZeroToOne};
+use super::specified;
+use super::{CSSFloat, CSSInteger};
+use crate::computed_value_flags::ComputedValueFlags;
+use crate::context::QuirksMode;
+use crate::font_metrics::{FontMetrics, FontMetricsOrientation};
+use crate::media_queries::Device;
+#[cfg(feature = "gecko")]
+use crate::properties;
+use crate::properties::{ComputedValues, LonghandId, StyleBuilder};
+use crate::rule_cache::RuleCacheConditions;
+use crate::stylesheets::container_rule::{
+    ContainerInfo, ContainerSizeQuery, ContainerSizeQueryResult,
+};
+use crate::values::specified::length::FontBaseSize;
+use crate::{ArcSlice, Atom, One};
+use euclid::{default, Point2D, Rect, Size2D};
+use servo_arc::Arc;
+use std::cell::RefCell;
+use std::cmp;
+use std::f32;
+use std::ops::{Add, Sub};
+
+#[cfg(feature = "gecko")]
+pub use self::align::{
+    AlignContent, AlignItems, AlignTracks, JustifyContent, JustifyItems, JustifyTracks,
+    SelfAlignment,
+};
+#[cfg(feature = "gecko")]
+pub use self::align::{AlignSelf, JustifySelf};
+pub use self::angle::Angle;
+pub use self::background::{BackgroundRepeat, BackgroundSize};
+pub use self::basic_shape::FillRule;
+pub use self::border::{BorderCornerRadius, BorderRadius, BorderSpacing};
+pub use self::border::{BorderImageRepeat, BorderImageSideWidth};
+pub use self::border::{BorderImageSlice, BorderImageWidth};
+pub use self::box_::{
+    AnimationIterationCount, AnimationName, AnimationTimeline, Contain, ContainerName,
+    ContainerType,
+};
+pub use self::box_::{
+    Appearance, BreakBetween, BreakWithin, Clear, ContainIntrinsicSize, ContentVisibility, Float,
+};
+pub use self::box_::{Display, LineClamp, Overflow, OverflowAnchor, TransitionProperty};
+pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize, ScrollbarGutter};
+pub use self::box_::{ScrollAxis, ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStop};
+pub use self::box_::{ScrollSnapStrictness, ScrollSnapType, ScrollTimelineName};
+pub use self::box_::{TouchAction, VerticalAlign, WillChange};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, ColorScheme, PrintColorAdjust};
+pub use self::column::ColumnCount;
+pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset, CounterSet};
+pub use self::easing::TimingFunction;
+pub use self::effects::{BoxShadow, Filter, SimpleShadow};
+pub use self::flex::FlexBasis;
+pub use self::font::{FontFamily, FontLanguageOverride, FontStyle, FontPalette};
+pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumeric};
+pub use self::font::{FontSize, FontSizeAdjust, FontStretch, FontSynthesis};
+pub use self::font::{FontVariantAlternates, FontWeight};
+pub use self::font::{FontVariantEastAsian, FontVariationSettings};
+pub use self::font::{MathDepth, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextZoom};
+pub use self::image::{Gradient, Image, ImageRendering, LineDirection, MozImageRect};
+pub use self::length::{CSSPixelLength, NonNegativeLength};
+pub use self::length::{Length, LengthOrNumber, LengthPercentage, NonNegativeLengthOrNumber};
+pub use self::length::{LengthOrAuto, LengthPercentageOrAuto, MaxSize, Size};
+pub use self::length::{NonNegativeLengthPercentage, NonNegativeLengthPercentageOrAuto};
+#[cfg(feature = "gecko")]
+pub use self::list::ListStyleType;
+pub use self::list::Quotes;
+pub use self::motion::{OffsetPath, OffsetRotate};
+pub use self::outline::OutlineStyle;
+pub use self::page::{PageName, PageSize, PageSizeOrientation, PaperSize};
+pub use self::percentage::{NonNegativePercentage, Percentage};
+pub use self::position::AspectRatio;
+pub use self::position::{
+    GridAutoFlow, GridTemplateAreas, MasonryAutoFlow, Position, PositionOrAuto, ZIndex,
+};
+pub use self::ratio::Ratio;
+pub use self::rect::NonNegativeLengthOrNumberRect;
+pub use self::resolution::Resolution;
+pub use self::svg::{DProperty, MozContextProperties};
+pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind};
+pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
+pub use self::text::HyphenateCharacter;
+pub use self::text::TextUnderlinePosition;
+pub use self::text::{InitialLetter, LetterSpacing, LineBreak, LineHeight};
+pub use self::text::{OverflowWrap, RubyPosition, TextOverflow, WordBreak, WordSpacing};
+pub use self::text::{TextAlign, TextAlignLast, TextEmphasisPosition, TextEmphasisStyle};
+pub use self::text::{TextDecorationLength, TextDecorationSkipInk, TextJustify};
+pub use self::time::Time;
+pub use self::transform::{Rotate, Scale, Transform, TransformOperation};
+pub use self::transform::{TransformOrigin, TransformStyle, Translate};
+#[cfg(feature = "gecko")]
+pub use self::ui::CursorImage;
+pub use self::ui::{BoolInteger, Cursor, UserSelect};
+pub use super::specified::TextTransform;
+pub use super::specified::ViewportVariant;
+pub use super::specified::{BorderStyle, TextDecorationLine};
+pub use app_units::Au;
+
+#[cfg(feature = "gecko")]
+pub mod align;
+pub mod angle;
+pub mod background;
+pub mod basic_shape;
+pub mod border;
+#[path = "box.rs"]
+pub mod box_;
+pub mod color;
+pub mod column;
+pub mod counters;
+pub mod easing;
+pub mod effects;
+pub mod flex;
+pub mod font;
+pub mod image;
+pub mod length;
+pub mod length_percentage;
+pub mod list;
+pub mod motion;
+pub mod outline;
+pub mod page;
+pub mod percentage;
+pub mod position;
+pub mod ratio;
+pub mod rect;
+pub mod resolution;
+pub mod svg;
+pub mod table;
+pub mod text;
+pub mod time;
+pub mod transform;
+pub mod ui;
+pub mod url;
+
+/// A `Context` is all the data a specified value could ever need to compute
+/// itself and be transformed to a computed value.
+pub struct Context<'a> {
+    /// Values accessed through this need to be in the properties "computed
+    /// early": color, text-decoration, font-size, display, position, float,
+    /// border-*-style, outline-style, font-family, writing-mode...
+    pub builder: StyleBuilder<'a>,
+
+    /// A cached computed system font value, for use by gecko.
+    ///
+    /// See properties/longhands/font.mako.rs
+    #[cfg(feature = "gecko")]
+    pub cached_system_font: Option<properties::longhands::system_font::ComputedSystemFont>,
+
+    /// A dummy option for servo so initializing a computed::Context isn't
+    /// painful.
+    ///
+    /// TODO(emilio): Make constructors for Context, and drop this.
+    #[cfg(feature = "servo")]
+    pub cached_system_font: Option<()>,
+
+    /// Whether or not we are computing the media list in a media query.
+    pub in_media_query: bool,
+
+    /// Whether or not we are computing the container query condition.
+    pub in_container_query: bool,
+
+    /// The quirks mode of this context.
+    pub quirks_mode: QuirksMode,
+
+    /// Whether this computation is being done for a SMIL animation.
+    ///
+    /// This is used to allow certain properties to generate out-of-range
+    /// values, which SMIL allows.
+    pub for_smil_animation: bool,
+
+    /// Returns the container information to evaluate a given container query.
+    pub container_info: Option<ContainerInfo>,
+
+    /// The property we are computing a value for, if it is a non-inherited
+    /// property.  None if we are computed a value for an inherited property
+    /// or not computing for a property at all (e.g. in a media query
+    /// evaluation).
+    pub for_non_inherited_property: Option<LonghandId>,
+
+    /// The conditions to cache a rule node on the rule cache.
+    ///
+    /// FIXME(emilio): Drop the refcell.
+    pub rule_cache_conditions: RefCell<&'a mut RuleCacheConditions>,
+
+    /// Container size query for this context.
+    container_size_query: RefCell<ContainerSizeQuery<'a>>,
+}
+
+impl<'a> Context<'a> {
+    /// Lazily evaluate the container size query, returning the result.
+    pub fn get_container_size_query(&self) -> ContainerSizeQueryResult {
+        let mut resolved = self.container_size_query.borrow_mut();
+        resolved.get().clone()
+    }
+
+    /// Creates a suitable context for media query evaluation, in which
+    /// font-relative units compute against the system_font, and executes `f`
+    /// with it.
+    pub fn for_media_query_evaluation<F, R>(device: &Device, quirks_mode: QuirksMode, f: F) -> R
+    where
+        F: FnOnce(&Context) -> R,
+    {
+        let mut conditions = RuleCacheConditions::default();
+        let context = Context {
+            builder: StyleBuilder::for_inheritance(device, None, None),
+            cached_system_font: None,
+            in_media_query: true,
+            in_container_query: false,
+            quirks_mode,
+            for_smil_animation: false,
+            container_info: None,
+            for_non_inherited_property: None,
+            rule_cache_conditions: RefCell::new(&mut conditions),
+            container_size_query: RefCell::new(ContainerSizeQuery::none()),
+        };
+        f(&context)
+    }
+
+    /// Creates a suitable context for container query evaluation for the style
+    /// specified.
+    pub fn for_container_query_evaluation<F, R>(
+        device: &Device,
+        container_info_and_style: Option<(ContainerInfo, Arc<ComputedValues>)>,
+        container_size_query: ContainerSizeQuery,
+        f: F,
+    ) -> R
+    where
+        F: FnOnce(&Context) -> R,
+    {
+        let mut conditions = RuleCacheConditions::default();
+
+        let (container_info, style) = match container_info_and_style {
+            Some((ci, s)) => (Some(ci), Some(s)),
+            None => (None, None),
+        };
+
+        let style = style.as_ref().map(|s| &**s);
+        let quirks_mode = device.quirks_mode();
+        let context = Context {
+            builder: StyleBuilder::for_inheritance(device, style, None),
+            cached_system_font: None,
+            in_media_query: false,
+            in_container_query: true,
+            quirks_mode,
+            for_smil_animation: false,
+            container_info,
+            for_non_inherited_property: None,
+            rule_cache_conditions: RefCell::new(&mut conditions),
+            container_size_query: RefCell::new(container_size_query),
+        };
+
+        f(&context)
+    }
+
+    /// Creates a context suitable for more general cases.
+    pub fn new(
+        builder: StyleBuilder<'a>,
+        quirks_mode: QuirksMode,
+        rule_cache_conditions: &'a mut RuleCacheConditions,
+        container_size_query: ContainerSizeQuery<'a>,
+    ) -> Self {
+        Self {
+            builder,
+            cached_system_font: None,
+            in_media_query: false,
+            in_container_query: false,
+            quirks_mode,
+            container_info: None,
+            for_smil_animation: false,
+            for_non_inherited_property: None,
+            rule_cache_conditions: RefCell::new(rule_cache_conditions),
+            container_size_query: RefCell::new(container_size_query),
+        }
+    }
+
+    /// Creates a context suitable for computing animations.
+    pub fn new_for_animation(
+        builder: StyleBuilder<'a>,
+        for_smil_animation: bool,
+        quirks_mode: QuirksMode,
+        rule_cache_conditions: &'a mut RuleCacheConditions,
+        container_size_query: ContainerSizeQuery<'a>,
+    ) -> Self {
+        Self {
+            builder,
+            cached_system_font: None,
+            in_media_query: false,
+            in_container_query: false,
+            quirks_mode,
+            container_info: None,
+            for_smil_animation,
+            for_non_inherited_property: None,
+            rule_cache_conditions: RefCell::new(rule_cache_conditions),
+            container_size_query: RefCell::new(container_size_query),
+        }
+    }
+
+    /// The current device.
+    pub fn device(&self) -> &Device {
+        self.builder.device
+    }
+
+    /// Queries font metrics.
+    pub fn query_font_metrics(
+        &self,
+        base_size: FontBaseSize,
+        orientation: FontMetricsOrientation,
+        retrieve_math_scales: bool,
+    ) -> FontMetrics {
+        if self.for_non_inherited_property.is_some() {
+            self.rule_cache_conditions.borrow_mut().set_uncacheable();
+        }
+        self.builder.add_flags(match base_size {
+            FontBaseSize::CurrentStyle => ComputedValueFlags::DEPENDS_ON_SELF_FONT_METRICS,
+            FontBaseSize::InheritedStyle => ComputedValueFlags::DEPENDS_ON_INHERITED_FONT_METRICS,
+        });
+        let size = base_size.resolve(self).used_size();
+        let style = self.style();
+
+        let (wm, font) = match base_size {
+            FontBaseSize::CurrentStyle => (style.writing_mode, style.get_font()),
+            // This is only used for font-size computation.
+            FontBaseSize::InheritedStyle => {
+                (*style.inherited_writing_mode(), style.get_parent_font())
+            },
+        };
+
+        let vertical = match orientation {
+            FontMetricsOrientation::MatchContextPreferHorizontal => {
+                wm.is_vertical() && wm.is_upright()
+            },
+            FontMetricsOrientation::MatchContextPreferVertical => {
+                wm.is_vertical() && !wm.is_sideways()
+            },
+            FontMetricsOrientation::Horizontal => false,
+        };
+        self.device().query_font_metrics(
+            vertical,
+            font,
+            size,
+            self.in_media_or_container_query(),
+            retrieve_math_scales,
+        )
+    }
+
+    /// The current viewport size, used to resolve viewport units.
+    pub fn viewport_size_for_viewport_unit_resolution(
+        &self,
+        variant: ViewportVariant,
+    ) -> default::Size2D<Au> {
+        self.builder
+            .add_flags(ComputedValueFlags::USES_VIEWPORT_UNITS);
+        self.builder
+            .device
+            .au_viewport_size_for_viewport_unit_resolution(variant)
+    }
+
+    /// Whether we're in a media or container query.
+    pub fn in_media_or_container_query(&self) -> bool {
+        self.in_media_query || self.in_container_query
+    }
+
+    /// The default computed style we're getting our reset style from.
+    pub fn default_style(&self) -> &ComputedValues {
+        self.builder.default_style()
+    }
+
+    /// The current style.
+    pub fn style(&self) -> &StyleBuilder {
+        &self.builder
+    }
+
+    /// Apply text-zoom if enabled.
+    #[cfg(feature = "gecko")]
+    pub fn maybe_zoom_text(&self, size: CSSPixelLength) -> CSSPixelLength {
+        // We disable zoom for <svg:text> by unsetting the
+        // -x-text-zoom property, which leads to a false value
+        // in mAllowZoomAndMinSize
+        if self.style().get_font().gecko.mAllowZoomAndMinSize {
+            self.device().zoom_text(size)
+        } else {
+            size
+        }
+    }
+
+    /// (Servo doesn't do text-zoom)
+    #[cfg(feature = "servo")]
+    pub fn maybe_zoom_text(&self, size: CSSPixelLength) -> CSSPixelLength {
+        size
+    }
+}
+
+/// An iterator over a slice of computed values
+#[derive(Clone)]
+pub struct ComputedVecIter<'a, 'cx, 'cx_a: 'cx, S: ToComputedValue + 'a> {
+    cx: &'cx Context<'cx_a>,
+    values: &'a [S],
+}
+
+impl<'a, 'cx, 'cx_a: 'cx, S: ToComputedValue + 'a> ComputedVecIter<'a, 'cx, 'cx_a, S> {
+    /// Construct an iterator from a slice of specified values and a context
+    pub fn new(cx: &'cx Context<'cx_a>, values: &'a [S]) -> Self {
+        ComputedVecIter { cx, values }
+    }
+}
+
+impl<'a, 'cx, 'cx_a: 'cx, S: ToComputedValue + 'a> ExactSizeIterator
+    for ComputedVecIter<'a, 'cx, 'cx_a, S>
+{
+    fn len(&self) -> usize {
+        self.values.len()
+    }
+}
+
+impl<'a, 'cx, 'cx_a: 'cx, S: ToComputedValue + 'a> Iterator for ComputedVecIter<'a, 'cx, 'cx_a, S> {
+    type Item = S::ComputedValue;
+    fn next(&mut self) -> Option<Self::Item> {
+        if let Some((next, rest)) = self.values.split_first() {
+            let ret = next.to_computed_value(self.cx);
+            self.values = rest;
+            Some(ret)
+        } else {
+            None
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.values.len(), Some(self.values.len()))
+    }
+}
+
+/// A trait to represent the conversion between computed and specified values.
+///
+/// This trait is derivable with `#[derive(ToComputedValue)]`. The derived
+/// implementation just calls `ToComputedValue::to_computed_value` on each field
+/// of the passed value. The deriving code assumes that if the type isn't
+/// generic, then the trait can be implemented as simple `Clone::clone` calls,
+/// this means that a manual implementation with `ComputedValue = Self` is bogus
+/// if it returns anything else than a clone.
+pub trait ToComputedValue {
+    /// The computed value type we're going to be converted to.
+    type ComputedValue;
+
+    /// Convert a specified value to a computed value, using itself and the data
+    /// inside the `Context`.
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue;
+
+    /// Convert a computed value to specified value form.
+    ///
+    /// This will be used for recascading during animation.
+    /// Such from_computed_valued values should recompute to the same value.
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self;
+}
+
+impl<A, B> ToComputedValue for (A, B)
+where
+    A: ToComputedValue,
+    B: ToComputedValue,
+{
+    type ComputedValue = (
+        <A as ToComputedValue>::ComputedValue,
+        <B as ToComputedValue>::ComputedValue,
+    );
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        (
+            self.0.to_computed_value(context),
+            self.1.to_computed_value(context),
+        )
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        (
+            A::from_computed_value(&computed.0),
+            B::from_computed_value(&computed.1),
+        )
+    }
+}
+
+impl<T> ToComputedValue for Option<T>
+where
+    T: ToComputedValue,
+{
+    type ComputedValue = Option<<T as ToComputedValue>::ComputedValue>;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        self.as_ref().map(|item| item.to_computed_value(context))
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        computed.as_ref().map(T::from_computed_value)
+    }
+}
+
+impl<T> ToComputedValue for default::Size2D<T>
+where
+    T: ToComputedValue,
+{
+    type ComputedValue = default::Size2D<<T as ToComputedValue>::ComputedValue>;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        Size2D::new(
+            self.width.to_computed_value(context),
+            self.height.to_computed_value(context),
+        )
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Size2D::new(
+            T::from_computed_value(&computed.width),
+            T::from_computed_value(&computed.height),
+        )
+    }
+}
+
+impl<T> ToComputedValue for Vec<T>
+where
+    T: ToComputedValue,
+{
+    type ComputedValue = Vec<<T as ToComputedValue>::ComputedValue>;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        self.iter()
+            .map(|item| item.to_computed_value(context))
+            .collect()
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        computed.iter().map(T::from_computed_value).collect()
+    }
+}
+
+impl<T> ToComputedValue for Box<T>
+where
+    T: ToComputedValue,
+{
+    type ComputedValue = Box<<T as ToComputedValue>::ComputedValue>;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        Box::new(T::to_computed_value(self, context))
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Box::new(T::from_computed_value(computed))
+    }
+}
+
+impl<T> ToComputedValue for Box<[T]>
+where
+    T: ToComputedValue,
+{
+    type ComputedValue = Box<[<T as ToComputedValue>::ComputedValue]>;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        self.iter()
+            .map(|item| item.to_computed_value(context))
+            .collect::<Vec<_>>()
+            .into_boxed_slice()
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        computed
+            .iter()
+            .map(T::from_computed_value)
+            .collect::<Vec<_>>()
+            .into_boxed_slice()
+    }
+}
+
+impl<T> ToComputedValue for crate::OwnedSlice<T>
+where
+    T: ToComputedValue,
+{
+    type ComputedValue = crate::OwnedSlice<<T as ToComputedValue>::ComputedValue>;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        self.iter()
+            .map(|item| item.to_computed_value(context))
+            .collect()
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        computed.iter().map(T::from_computed_value).collect()
+    }
+}
+
+// NOTE(emilio): This is implementable more generically, but it's unlikely
+// what you want there, as it forces you to have an extra allocation.
+//
+// We could do that if needed, ideally with specialization for the case where
+// ComputedValue = T. But we don't need it for now.
+impl<T> ToComputedValue for Arc<T>
+where
+    T: ToComputedValue<ComputedValue = T>,
+{
+    type ComputedValue = Self;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> Self {
+        self.clone()
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self) -> Self {
+        computed.clone()
+    }
+}
+
+// Same caveat as above applies.
+impl<T> ToComputedValue for ArcSlice<T>
+where
+    T: ToComputedValue<ComputedValue = T>,
+{
+    type ComputedValue = Self;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> Self {
+        self.clone()
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self) -> Self {
+        computed.clone()
+    }
+}
+
+trivial_to_computed_value!(());
+trivial_to_computed_value!(bool);
+trivial_to_computed_value!(f32);
+trivial_to_computed_value!(i32);
+trivial_to_computed_value!(u8);
+trivial_to_computed_value!(u16);
+trivial_to_computed_value!(u32);
+trivial_to_computed_value!(usize);
+trivial_to_computed_value!(Atom);
+trivial_to_computed_value!(crate::values::AtomIdent);
+#[cfg(feature = "servo")]
+trivial_to_computed_value!(crate::Namespace);
+#[cfg(feature = "servo")]
+trivial_to_computed_value!(crate::Prefix);
+trivial_to_computed_value!(String);
+trivial_to_computed_value!(Box<str>);
+trivial_to_computed_value!(crate::OwnedStr);
+trivial_to_computed_value!(style_traits::values::specified::AllowedNumericType);
+
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+)]
+#[repr(C, u8)]
+pub enum AngleOrPercentage {
+    Percentage(Percentage),
+    Angle(Angle),
+}
+
+impl ToComputedValue for specified::AngleOrPercentage {
+    type ComputedValue = AngleOrPercentage;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> AngleOrPercentage {
+        match *self {
+            specified::AngleOrPercentage::Percentage(percentage) => {
+                AngleOrPercentage::Percentage(percentage.to_computed_value(context))
+            },
+            specified::AngleOrPercentage::Angle(angle) => {
+                AngleOrPercentage::Angle(angle.to_computed_value(context))
+            },
+        }
+    }
+    #[inline]
+    fn from_computed_value(computed: &AngleOrPercentage) -> Self {
+        match *computed {
+            AngleOrPercentage::Percentage(percentage) => specified::AngleOrPercentage::Percentage(
+                ToComputedValue::from_computed_value(&percentage),
+            ),
+            AngleOrPercentage::Angle(angle) => {
+                specified::AngleOrPercentage::Angle(ToComputedValue::from_computed_value(&angle))
+            },
+        }
+    }
+}
+
+/// A `<number>` value.
+pub type Number = CSSFloat;
+
+impl IsParallelTo for (Number, Number, Number) {
+    fn is_parallel_to(&self, vector: &DirectionVector) -> bool {
+        use euclid::approxeq::ApproxEq;
+        // If a and b is parallel, the angle between them is 0deg, so
+        // a x b = |a|*|b|*sin(0)*n = 0 * n, |a x b| == 0.
+        let self_vector = DirectionVector::new(self.0, self.1, self.2);
+        self_vector
+            .cross(*vector)
+            .square_length()
+            .approx_eq(&0.0f32)
+    }
+}
+
+/// A wrapper of Number, but the value >= 0.
+pub type NonNegativeNumber = NonNegative<CSSFloat>;
+
+impl ToAnimatedValue for NonNegativeNumber {
+    type AnimatedValue = CSSFloat;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        animated.max(0.).into()
+    }
+}
+
+impl From<CSSFloat> for NonNegativeNumber {
+    #[inline]
+    fn from(number: CSSFloat) -> NonNegativeNumber {
+        NonNegative::<CSSFloat>(number)
+    }
+}
+
+impl From<NonNegativeNumber> for CSSFloat {
+    #[inline]
+    fn from(number: NonNegativeNumber) -> CSSFloat {
+        number.0
+    }
+}
+
+impl One for NonNegativeNumber {
+    #[inline]
+    fn one() -> Self {
+        NonNegative(1.0)
+    }
+
+    #[inline]
+    fn is_one(&self) -> bool {
+        self.0 == 1.0
+    }
+}
+
+/// A wrapper of Number, but the value between 0 and 1
+pub type ZeroToOneNumber = ZeroToOne<CSSFloat>;
+
+impl ToAnimatedValue for ZeroToOneNumber {
+    type AnimatedValue = CSSFloat;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        Self(animated.max(0.).min(1.))
+    }
+}
+
+impl From<CSSFloat> for ZeroToOneNumber {
+    #[inline]
+    fn from(number: CSSFloat) -> Self {
+        Self(number)
+    }
+}
+
+/// A wrapper of Number, but the value >= 1.
+pub type GreaterThanOrEqualToOneNumber = GreaterThanOrEqualToOne<CSSFloat>;
+
+impl ToAnimatedValue for GreaterThanOrEqualToOneNumber {
+    type AnimatedValue = CSSFloat;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        animated.max(1.).into()
+    }
+}
+
+impl From<CSSFloat> for GreaterThanOrEqualToOneNumber {
+    #[inline]
+    fn from(number: CSSFloat) -> GreaterThanOrEqualToOneNumber {
+        GreaterThanOrEqualToOne::<CSSFloat>(number)
+    }
+}
+
+impl From<GreaterThanOrEqualToOneNumber> for CSSFloat {
+    #[inline]
+    fn from(number: GreaterThanOrEqualToOneNumber) -> CSSFloat {
+        number.0
+    }
+}
+
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+)]
+#[repr(C, u8)]
+pub enum NumberOrPercentage {
+    Percentage(Percentage),
+    Number(Number),
+}
+
+impl NumberOrPercentage {
+    fn clamp_to_non_negative(self) -> Self {
+        match self {
+            NumberOrPercentage::Percentage(p) => {
+                NumberOrPercentage::Percentage(p.clamp_to_non_negative())
+            },
+            NumberOrPercentage::Number(n) => NumberOrPercentage::Number(n.max(0.)),
+        }
+    }
+}
+
+impl ToComputedValue for specified::NumberOrPercentage {
+    type ComputedValue = NumberOrPercentage;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> NumberOrPercentage {
+        match *self {
+            specified::NumberOrPercentage::Percentage(percentage) => {
+                NumberOrPercentage::Percentage(percentage.to_computed_value(context))
+            },
+            specified::NumberOrPercentage::Number(number) => {
+                NumberOrPercentage::Number(number.to_computed_value(context))
+            },
+        }
+    }
+    #[inline]
+    fn from_computed_value(computed: &NumberOrPercentage) -> Self {
+        match *computed {
+            NumberOrPercentage::Percentage(percentage) => {
+                specified::NumberOrPercentage::Percentage(ToComputedValue::from_computed_value(
+                    &percentage,
+                ))
+            },
+            NumberOrPercentage::Number(number) => {
+                specified::NumberOrPercentage::Number(ToComputedValue::from_computed_value(&number))
+            },
+        }
+    }
+}
+
+/// A non-negative <number-percentage>.
+pub type NonNegativeNumberOrPercentage = NonNegative<NumberOrPercentage>;
+
+impl NonNegativeNumberOrPercentage {
+    /// Returns the `100%` value.
+    #[inline]
+    pub fn hundred_percent() -> Self {
+        NonNegative(NumberOrPercentage::Percentage(Percentage::hundred()))
+    }
+}
+
+impl ToAnimatedValue for NonNegativeNumberOrPercentage {
+    type AnimatedValue = NumberOrPercentage;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        NonNegative(animated.clamp_to_non_negative())
+    }
+}
+
+/// A type used for opacity.
+pub type Opacity = CSSFloat;
+
+/// A `<integer>` value.
+pub type Integer = CSSInteger;
+
+/// A wrapper of Integer, but only accept a value >= 1.
+pub type PositiveInteger = GreaterThanOrEqualToOne<CSSInteger>;
+
+impl ToAnimatedValue for PositiveInteger {
+    type AnimatedValue = CSSInteger;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        cmp::max(animated, 1).into()
+    }
+}
+
+impl From<CSSInteger> for PositiveInteger {
+    #[inline]
+    fn from(int: CSSInteger) -> PositiveInteger {
+        GreaterThanOrEqualToOne::<CSSInteger>(int)
+    }
+}
+
+/// rect(...) | auto
+pub type ClipRect = generics::GenericClipRect<LengthOrAuto>;
+
+/// rect(...) | auto
+pub type ClipRectOrAuto = generics::GenericClipRectOrAuto<ClipRect>;
+
+/// The computed value of a grid `<track-breadth>`
+pub type TrackBreadth = GenericTrackBreadth<LengthPercentage>;
+
+/// The computed value of a grid `<track-size>`
+pub type TrackSize = GenericTrackSize<LengthPercentage>;
+
+/// The computed value of a grid `<track-size>+`
+pub type ImplicitGridTracks = GenericImplicitGridTracks<TrackSize>;
+
+/// The computed value of a grid `<track-list>`
+/// (could also be `<auto-track-list>` or `<explicit-track-list>`)
+pub type TrackList = GenericTrackList<LengthPercentage, Integer>;
+
+/// The computed value of a `<grid-line>`.
+pub type GridLine = GenericGridLine<Integer>;
+
+/// `<grid-template-rows> | <grid-template-columns>`
+pub type GridTemplateComponent = GenericGridTemplateComponent<LengthPercentage, Integer>;
+
+impl ClipRect {
+    /// Given a border box, resolves the clip rect against the border box
+    /// in the same space the border box is in
+    pub fn for_border_rect<T: Copy + From<Length> + Add<Output = T> + Sub<Output = T>, U>(
+        &self,
+        border_box: Rect<T, U>,
+    ) -> Rect<T, U> {
+        fn extract_clip_component<T: From<Length>>(p: &LengthOrAuto, or: T) -> T {
+            match *p {
+                LengthOrAuto::Auto => or,
+                LengthOrAuto::LengthPercentage(ref length) => T::from(*length),
+            }
+        }
+
+        let clip_origin = Point2D::new(
+            From::from(self.left.auto_is(|| Length::new(0.))),
+            From::from(self.top.auto_is(|| Length::new(0.))),
+        );
+        let right = extract_clip_component(&self.right, border_box.size.width);
+        let bottom = extract_clip_component(&self.bottom, border_box.size.height);
+        let clip_size = Size2D::new(right - clip_origin.x, bottom - clip_origin.y);
+
+        Rect::new(clip_origin, clip_size).translate(border_box.origin.to_vector())
+    }
+}
diff --git a/servo/components/style/values/computed/motion.rs b/servo/components/style/values/computed/motion.rs
new file mode 100644
index 0000000000..e2565ff346
--- /dev/null
+++ b/servo/components/style/values/computed/motion.rs
@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS values that are related to motion path.
+
+use crate::values::computed::Angle;
+use crate::values::generics::motion::GenericOffsetPath;
+use crate::Zero;
+
+/// The computed value of `offset-path`.
+pub type OffsetPath = GenericOffsetPath<Angle>;
+
+#[inline]
+fn is_auto_zero_angle(auto: &bool, angle: &Angle) -> bool {
+    *auto && angle.is_zero()
+}
+
+/// A computed offset-rotate.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+)]
+#[repr(C)]
+pub struct OffsetRotate {
+    /// If auto is false, this is a fixed angle which indicates a
+    /// constant clockwise rotation transformation applied to it by this
+    /// specified rotation angle. Otherwise, the angle will be added to
+    /// the angle of the direction in layout.
+    #[animation(constant)]
+    #[css(represents_keyword)]
+    pub auto: bool,
+    /// The angle value.
+    #[css(contextual_skip_if = "is_auto_zero_angle")]
+    pub angle: Angle,
+}
+
+impl OffsetRotate {
+    /// Returns "auto 0deg".
+    #[inline]
+    pub fn auto() -> Self {
+        OffsetRotate {
+            auto: true,
+            angle: Zero::zero(),
+        }
+    }
+}
diff --git a/servo/components/style/values/computed/outline.rs b/servo/components/style/values/computed/outline.rs
new file mode 100644
index 0000000000..f872176529
--- /dev/null
+++ b/servo/components/style/values/computed/outline.rs
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed values for outline properties
+
+pub use crate::values::specified::OutlineStyle;
diff --git a/servo/components/style/values/computed/page.rs b/servo/components/style/values/computed/page.rs
new file mode 100644
index 0000000000..d54fca329b
--- /dev/null
+++ b/servo/components/style/values/computed/page.rs
@@ -0,0 +1,74 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed @page at-rule properties and named-page style properties
+
+use crate::values::computed::length::NonNegativeLength;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics;
+use crate::values::generics::size::Size2D;
+
+use crate::values::specified::page as specified;
+pub use generics::page::GenericPageSize;
+pub use generics::page::PageSizeOrientation;
+pub use generics::page::PaperSize;
+pub use specified::PageName;
+
+/// Computed value of the @page size descriptor
+///
+/// The spec says that the computed value should be the same as the specified
+/// value but with all absolute units, but it's not currently possibly observe
+/// the computed value of page-size.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToResolvedValue, ToShmem)]
+#[repr(C, u8)]
+pub enum PageSize {
+    /// Specified size, paper size, or paper size and orientation.
+    Size(Size2D<NonNegativeLength>),
+    /// `landscape` or `portrait` value, no specified size.
+    Orientation(PageSizeOrientation),
+    /// `auto` value
+    Auto,
+}
+
+impl ToComputedValue for specified::PageSize {
+    type ComputedValue = PageSize;
+
+    fn to_computed_value(&self, ctx: &Context) -> Self::ComputedValue {
+        match &*self {
+            Self::Size(s) => PageSize::Size(s.to_computed_value(ctx)),
+            Self::PaperSize(p, PageSizeOrientation::Landscape) => PageSize::Size(Size2D {
+                width: p.long_edge().to_computed_value(ctx),
+                height: p.short_edge().to_computed_value(ctx),
+            }),
+            Self::PaperSize(p, PageSizeOrientation::Portrait) => PageSize::Size(Size2D {
+                width: p.short_edge().to_computed_value(ctx),
+                height: p.long_edge().to_computed_value(ctx),
+            }),
+            Self::Orientation(o) => PageSize::Orientation(*o),
+            Self::Auto => PageSize::Auto,
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        match *computed {
+            PageSize::Size(s) => Self::Size(ToComputedValue::from_computed_value(&s)),
+            PageSize::Orientation(o) => Self::Orientation(o),
+            PageSize::Auto => Self::Auto,
+        }
+    }
+}
+
+impl PageSize {
+    /// `auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        PageSize::Auto
+    }
+
+    /// Whether this is the `auto` value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, PageSize::Auto)
+    }
+}
diff --git a/servo/components/style/values/computed/percentage.rs b/servo/components/style/values/computed/percentage.rs
new file mode 100644
index 0000000000..30ef5ab0f0
--- /dev/null
+++ b/servo/components/style/values/computed/percentage.rs
@@ -0,0 +1,136 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed percentages.
+
+use crate::values::animated::ToAnimatedValue;
+use crate::values::generics::NonNegative;
+use crate::values::specified::percentage::ToPercentage;
+use crate::values::{serialize_percentage, CSSFloat};
+use crate::Zero;
+use std::fmt;
+use style_traits::{CssWriter, ToCss};
+
+/// A computed percentage.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Default,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct Percentage(pub CSSFloat);
+
+impl Percentage {
+    /// 100%
+    #[inline]
+    pub fn hundred() -> Self {
+        Percentage(1.)
+    }
+
+    /// Returns the absolute value for this percentage.
+    #[inline]
+    pub fn abs(&self) -> Self {
+        Percentage(self.0.abs())
+    }
+
+    /// Clamps this percentage to a non-negative percentage.
+    #[inline]
+    pub fn clamp_to_non_negative(self) -> Self {
+        Percentage(self.0.max(0.))
+    }
+}
+
+impl Zero for Percentage {
+    fn zero() -> Self {
+        Percentage(0.)
+    }
+
+    fn is_zero(&self) -> bool {
+        self.0 == 0.
+    }
+}
+
+impl ToPercentage for Percentage {
+    fn to_percentage(&self) -> CSSFloat {
+        self.0
+    }
+}
+
+impl std::ops::AddAssign for Percentage {
+    fn add_assign(&mut self, other: Self) {
+        self.0 += other.0
+    }
+}
+
+impl std::ops::Add for Percentage {
+    type Output = Self;
+
+    fn add(self, other: Self) -> Self {
+        Percentage(self.0 + other.0)
+    }
+}
+
+impl std::ops::Sub for Percentage {
+    type Output = Self;
+
+    fn sub(self, other: Self) -> Self {
+        Percentage(self.0 - other.0)
+    }
+}
+
+impl std::ops::Rem for Percentage {
+    type Output = Self;
+
+    fn rem(self, other: Self) -> Self {
+        Percentage(self.0 % other.0)
+    }
+}
+
+impl ToCss for Percentage {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        serialize_percentage(self.0, dest)
+    }
+}
+
+/// A wrapper over a `Percentage`, whose value should be clamped to 0.
+pub type NonNegativePercentage = NonNegative<Percentage>;
+
+impl NonNegativePercentage {
+    /// 100%
+    #[inline]
+    pub fn hundred() -> Self {
+        NonNegative(Percentage::hundred())
+    }
+}
+
+impl ToAnimatedValue for NonNegativePercentage {
+    type AnimatedValue = Percentage;
+
+    #[inline]
+    fn to_animated_value(self) -> Self::AnimatedValue {
+        self.0
+    }
+
+    #[inline]
+    fn from_animated_value(animated: Self::AnimatedValue) -> Self {
+        NonNegative(animated.clamp_to_non_negative())
+    }
+}
diff --git a/servo/components/style/values/computed/position.rs b/servo/components/style/values/computed/position.rs
new file mode 100644
index 0000000000..6d09e327e6
--- /dev/null
+++ b/servo/components/style/values/computed/position.rs
@@ -0,0 +1,74 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the computed value of
+//! [`position`][position] values.
+//!
+//! [position]: https://drafts.csswg.org/css-backgrounds-3/#position
+
+use crate::values::computed::{Integer, LengthPercentage, NonNegativeNumber, Percentage};
+use crate::values::generics::position::AspectRatio as GenericAspectRatio;
+use crate::values::generics::position::Position as GenericPosition;
+use crate::values::generics::position::PositionComponent as GenericPositionComponent;
+use crate::values::generics::position::PositionOrAuto as GenericPositionOrAuto;
+use crate::values::generics::position::ZIndex as GenericZIndex;
+pub use crate::values::specified::position::{GridAutoFlow, GridTemplateAreas, MasonryAutoFlow};
+use crate::Zero;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// The computed value of a CSS `<position>`
+pub type Position = GenericPosition<HorizontalPosition, VerticalPosition>;
+
+/// The computed value of an `auto | <position>`
+pub type PositionOrAuto = GenericPositionOrAuto<Position>;
+
+/// The computed value of a CSS horizontal position.
+pub type HorizontalPosition = LengthPercentage;
+
+/// The computed value of a CSS vertical position.
+pub type VerticalPosition = LengthPercentage;
+
+impl Position {
+    /// `50% 50%`
+    #[inline]
+    pub fn center() -> Self {
+        Self::new(
+            LengthPercentage::new_percent(Percentage(0.5)),
+            LengthPercentage::new_percent(Percentage(0.5)),
+        )
+    }
+
+    /// `0% 0%`
+    #[inline]
+    pub fn zero() -> Self {
+        Self::new(LengthPercentage::zero(), LengthPercentage::zero())
+    }
+}
+
+impl ToCss for Position {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.horizontal.to_css(dest)?;
+        dest.write_str(" ")?;
+        self.vertical.to_css(dest)
+    }
+}
+
+impl GenericPositionComponent for LengthPercentage {
+    fn is_center(&self) -> bool {
+        match self.to_percentage() {
+            Some(Percentage(per)) => per == 0.5,
+            _ => false,
+        }
+    }
+}
+
+/// A computed value for the `z-index` property.
+pub type ZIndex = GenericZIndex<Integer>;
+
+/// A computed value for the `aspect-ratio` property.
+pub type AspectRatio = GenericAspectRatio<NonNegativeNumber>;
diff --git a/servo/components/style/values/computed/ratio.rs b/servo/components/style/values/computed/ratio.rs
new file mode 100644
index 0000000000..ae8997cfc0
--- /dev/null
+++ b/servo/components/style/values/computed/ratio.rs
@@ -0,0 +1,115 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! `<ratio>` computed values.
+
+use crate::values::animated::{Animate, Procedure};
+use crate::values::computed::NonNegativeNumber;
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::ratio::Ratio as GenericRatio;
+use crate::{One, Zero};
+use std::cmp::{Ordering, PartialOrd};
+
+/// A computed <ratio> value.
+pub type Ratio = GenericRatio<NonNegativeNumber>;
+
+impl PartialOrd for Ratio {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        f64::partial_cmp(
+            &((self.0).0 as f64 * (other.1).0 as f64),
+            &((self.1).0 as f64 * (other.0).0 as f64),
+        )
+    }
+}
+
+/// https://drafts.csswg.org/css-values/#combine-ratio
+impl Animate for Ratio {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        // If either <ratio> is degenerate, the values cannot be interpolated.
+        if self.is_degenerate() || other.is_degenerate() {
+            return Err(());
+        }
+
+        // Addition of <ratio>s is not possible, and based on
+        // https://drafts.csswg.org/css-values-4/#not-additive,
+        // we simply use the first value as the result value.
+        // Besides, the procedure for accumulation should be identical to addition here.
+        if matches!(procedure, Procedure::Add | Procedure::Accumulate { .. }) {
+            return Ok(self.clone());
+        }
+
+        // The interpolation of a <ratio> is defined by converting each <ratio> to a number by
+        // dividing the first value by the second (so a ratio of 3 / 2 would become 1.5), taking
+        // the logarithm of that result (so the 1.5 would become approximately 0.176), then
+        // interpolating those values.
+        //
+        // The result during the interpolation is converted back to a <ratio> by inverting the
+        // logarithm, then interpreting the result as a <ratio> with the result as the first value
+        // and 1 as the second value.
+        let start = self.to_f32().ln();
+        let end = other.to_f32().ln();
+        let e = std::f32::consts::E;
+        let result = e.powf(start.animate(&end, procedure)?);
+        // The range of the result is [0, inf), based on the easing function.
+        if result.is_zero() || result.is_infinite() {
+            return Err(());
+        }
+        Ok(Ratio::new(result, 1.0f32))
+    }
+}
+
+impl ComputeSquaredDistance for Ratio {
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        if self.is_degenerate() || other.is_degenerate() {
+            return Err(());
+        }
+        // Use the distance of their logarithm values. (This is used by testing, so don't need to
+        // care about the base. Here we use the same base as that in animate().)
+        self.to_f32()
+            .ln()
+            .compute_squared_distance(&other.to_f32().ln())
+    }
+}
+
+impl Zero for Ratio {
+    fn zero() -> Self {
+        Self::new(Zero::zero(), One::one())
+    }
+
+    fn is_zero(&self) -> bool {
+        self.0.is_zero()
+    }
+}
+
+impl Ratio {
+    /// Returns a new Ratio.
+    #[inline]
+    pub fn new(a: f32, b: f32) -> Self {
+        GenericRatio(a.into(), b.into())
+    }
+
+    /// Returns the used value. A ratio of 0/0 behaves as the ratio 1/0.
+    /// https://drafts.csswg.org/css-values-4/#ratios
+    pub fn used_value(self) -> Self {
+        if self.0.is_zero() && self.1.is_zero() {
+            Ratio::new(One::one(), Zero::zero())
+        } else {
+            self
+        }
+    }
+
+    /// Returns true if this is a degenerate ratio.
+    /// https://drafts.csswg.org/css-values/#degenerate-ratio
+    #[inline]
+    pub fn is_degenerate(&self) -> bool {
+        self.0.is_zero() || self.1.is_zero()
+    }
+
+    /// Returns the f32 value by dividing the first value by the second one.
+    #[inline]
+    fn to_f32(&self) -> f32 {
+        debug_assert!(!self.is_degenerate());
+        (self.0).0 / (self.1).0
+    }
+}
diff --git a/servo/components/style/values/computed/rect.rs b/servo/components/style/values/computed/rect.rs
new file mode 100644
index 0000000000..ec44360fc8
--- /dev/null
+++ b/servo/components/style/values/computed/rect.rs
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS borders.
+
+use crate::values::computed::length::NonNegativeLengthOrNumber;
+use crate::values::generics::rect::Rect;
+
+/// A specified rectangle made of four `<length-or-number>` values.
+pub type NonNegativeLengthOrNumberRect = Rect<NonNegativeLengthOrNumber>;
diff --git a/servo/components/style/values/computed/resolution.rs b/servo/components/style/values/computed/resolution.rs
new file mode 100644
index 0000000000..72580635b8
--- /dev/null
+++ b/servo/components/style/values/computed/resolution.rs
@@ -0,0 +1,56 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Resolution values:
+//!
+//! https://drafts.csswg.org/css-values/#resolution
+
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::specified;
+use crate::values::CSSFloat;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// A computed `<resolution>`.
+#[repr(C)]
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToResolvedValue, ToShmem)]
+pub struct Resolution(CSSFloat);
+
+impl Resolution {
+    /// Returns this resolution value as dppx.
+    #[inline]
+    pub fn dppx(&self) -> CSSFloat {
+        self.0
+    }
+
+    /// Return a computed `resolution` value from a dppx float value.
+    #[inline]
+    pub fn from_dppx(dppx: CSSFloat) -> Self {
+        Resolution(dppx)
+    }
+}
+
+impl ToComputedValue for specified::Resolution {
+    type ComputedValue = Resolution;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
+        Resolution(self.to_dppx())
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        specified::Resolution::Dppx(computed.dppx())
+    }
+}
+
+impl ToCss for Resolution {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        self.dppx().to_css(dest)?;
+        dest.write_str("dppx")
+    }
+}
diff --git a/servo/components/style/values/computed/svg.rs b/servo/components/style/values/computed/svg.rs
new file mode 100644
index 0000000000..640c3bfda7
--- /dev/null
+++ b/servo/components/style/values/computed/svg.rs
@@ -0,0 +1,68 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for SVG properties.
+
+use crate::values::computed::color::Color;
+use crate::values::computed::url::ComputedUrl;
+use crate::values::computed::{LengthPercentage, NonNegativeLengthPercentage, Opacity};
+use crate::values::generics::svg as generic;
+use crate::Zero;
+
+pub use crate::values::specified::{DProperty, MozContextProperties, SVGPaintOrder};
+
+/// Computed SVG Paint value
+pub type SVGPaint = generic::GenericSVGPaint<Color, ComputedUrl>;
+
+/// Computed SVG Paint Kind value
+pub type SVGPaintKind = generic::GenericSVGPaintKind<Color, ComputedUrl>;
+
+impl SVGPaint {
+    /// Opaque black color
+    pub fn black() -> Self {
+        SVGPaint {
+            kind: generic::SVGPaintKind::Color(Color::black()),
+            fallback: generic::SVGPaintFallback::Unset,
+        }
+    }
+}
+
+/// <length> | <percentage> | <number> | context-value
+pub type SVGLength = generic::GenericSVGLength<LengthPercentage>;
+
+impl SVGLength {
+    /// `0px`
+    pub fn zero() -> Self {
+        generic::SVGLength::LengthPercentage(LengthPercentage::zero())
+    }
+}
+
+/// An non-negative wrapper of SVGLength.
+pub type SVGWidth = generic::GenericSVGLength<NonNegativeLengthPercentage>;
+
+impl SVGWidth {
+    /// `1px`.
+    pub fn one() -> Self {
+        use crate::values::generics::NonNegative;
+        generic::SVGLength::LengthPercentage(NonNegative(LengthPercentage::one()))
+    }
+}
+
+/// [ <length> | <percentage> | <number> ]# | context-value
+pub type SVGStrokeDashArray = generic::GenericSVGStrokeDashArray<NonNegativeLengthPercentage>;
+
+impl Default for SVGStrokeDashArray {
+    fn default() -> Self {
+        generic::SVGStrokeDashArray::Values(Default::default())
+    }
+}
+
+/// <opacity-value> | context-fill-opacity | context-stroke-opacity
+pub type SVGOpacity = generic::GenericSVGOpacity<Opacity>;
+
+impl Default for SVGOpacity {
+    fn default() -> Self {
+        generic::SVGOpacity::Opacity(1.)
+    }
+}
diff --git a/servo/components/style/values/computed/table.rs b/servo/components/style/values/computed/table.rs
new file mode 100644
index 0000000000..47109e20ec
--- /dev/null
+++ b/servo/components/style/values/computed/table.rs
@@ -0,0 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS values related to tables.
+
+pub use super::specified::table::CaptionSide;
diff --git a/servo/components/style/values/computed/text.rs b/servo/components/style/values/computed/text.rs
new file mode 100644
index 0000000000..c2b017f397
--- /dev/null
+++ b/servo/components/style/values/computed/text.rs
@@ -0,0 +1,229 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for text properties.
+
+#[cfg(feature = "servo")]
+use crate::properties::StyleBuilder;
+use crate::values::computed::length::{Length, LengthPercentage};
+use crate::values::computed::{Context, NonNegativeLength, NonNegativeNumber, ToComputedValue};
+use crate::values::generics::text::InitialLetter as GenericInitialLetter;
+use crate::values::generics::text::LineHeight as GenericLineHeight;
+use crate::values::generics::text::{GenericTextDecorationLength, Spacing};
+use crate::values::specified::text::{self as specified, TextOverflowSide};
+use crate::values::specified::text::{TextEmphasisFillMode, TextEmphasisShapeKeyword};
+use crate::values::{CSSFloat, CSSInteger};
+use crate::Zero;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+pub use crate::values::specified::text::{
+    MozControlCharacterVisibility, TextAlignLast, TextUnderlinePosition,
+};
+pub use crate::values::specified::HyphenateCharacter;
+pub use crate::values::specified::{LineBreak, OverflowWrap, RubyPosition, WordBreak};
+pub use crate::values::specified::{TextDecorationLine, TextEmphasisPosition};
+pub use crate::values::specified::{TextDecorationSkipInk, TextJustify, TextTransform};
+
+/// A computed value for the `initial-letter` property.
+pub type InitialLetter = GenericInitialLetter<CSSFloat, CSSInteger>;
+
+/// Implements type for `text-decoration-thickness` property.
+pub type TextDecorationLength = GenericTextDecorationLength<LengthPercentage>;
+
+/// The computed value of `text-align`.
+pub type TextAlign = specified::TextAlignKeyword;
+
+/// A computed value for the `letter-spacing` property.
+#[repr(transparent)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToResolvedValue,
+)]
+pub struct LetterSpacing(pub Length);
+
+impl LetterSpacing {
+    /// Return the `normal` computed value, which is just zero.
+    #[inline]
+    pub fn normal() -> Self {
+        LetterSpacing(Length::zero())
+    }
+}
+
+impl ToCss for LetterSpacing {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        // https://drafts.csswg.org/css-text/#propdef-letter-spacing
+        //
+        // For legacy reasons, a computed letter-spacing of zero yields a
+        // resolved value (getComputedStyle() return value) of normal.
+        if self.0.is_zero() {
+            return dest.write_str("normal");
+        }
+        self.0.to_css(dest)
+    }
+}
+
+impl ToComputedValue for specified::LetterSpacing {
+    type ComputedValue = LetterSpacing;
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            Spacing::Normal => LetterSpacing(Length::zero()),
+            Spacing::Value(ref v) => LetterSpacing(v.to_computed_value(context)),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        if computed.0.is_zero() {
+            return Spacing::Normal;
+        }
+        Spacing::Value(ToComputedValue::from_computed_value(&computed.0))
+    }
+}
+
+/// A computed value for the `word-spacing` property.
+pub type WordSpacing = LengthPercentage;
+
+impl ToComputedValue for specified::WordSpacing {
+    type ComputedValue = WordSpacing;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            Spacing::Normal => LengthPercentage::zero(),
+            Spacing::Value(ref v) => v.to_computed_value(context),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Spacing::Value(ToComputedValue::from_computed_value(computed))
+    }
+}
+
+/// A computed value for the `line-height` property.
+pub type LineHeight = GenericLineHeight<NonNegativeNumber, NonNegativeLength>;
+
+impl WordSpacing {
+    /// Return the `normal` computed value, which is just zero.
+    #[inline]
+    pub fn normal() -> Self {
+        LengthPercentage::zero()
+    }
+}
+
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToResolvedValue)]
+#[repr(C)]
+/// text-overflow.
+/// When the specified value only has one side, that's the "second"
+/// side, and the sides are logical, so "second" means "end".  The
+/// start side is Clip in that case.
+///
+/// When the specified value has two sides, those are our "first"
+/// and "second" sides, and they are physical sides ("left" and
+/// "right").
+pub struct TextOverflow {
+    /// First side
+    pub first: TextOverflowSide,
+    /// Second side
+    pub second: TextOverflowSide,
+    /// True if the specified value only has one side.
+    pub sides_are_logical: bool,
+}
+
+impl TextOverflow {
+    /// Returns the initial `text-overflow` value
+    pub fn get_initial_value() -> TextOverflow {
+        TextOverflow {
+            first: TextOverflowSide::Clip,
+            second: TextOverflowSide::Clip,
+            sides_are_logical: true,
+        }
+    }
+}
+
+impl ToCss for TextOverflow {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.sides_are_logical {
+            debug_assert_eq!(self.first, TextOverflowSide::Clip);
+            self.second.to_css(dest)?;
+        } else {
+            self.first.to_css(dest)?;
+            dest.write_str(" ")?;
+            self.second.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+/// A struct that represents the _used_ value of the text-decoration property.
+///
+/// FIXME(emilio): This is done at style resolution time, though probably should
+/// be done at layout time, otherwise we need to account for display: contents
+/// and similar stuff when we implement it.
+///
+/// FIXME(emilio): Also, should be just a bitfield instead of three bytes.
+#[derive(Clone, Copy, Debug, Default, MallocSizeOf, PartialEq, ToResolvedValue)]
+pub struct TextDecorationsInEffect {
+    /// Whether an underline is in effect.
+    pub underline: bool,
+    /// Whether an overline decoration is in effect.
+    pub overline: bool,
+    /// Whether a line-through style is in effect.
+    pub line_through: bool,
+}
+
+impl TextDecorationsInEffect {
+    /// Computes the text-decorations in effect for a given style.
+    #[cfg(feature = "servo")]
+    pub fn from_style(style: &StyleBuilder) -> Self {
+        // Start with no declarations if this is an atomic inline-level box;
+        // otherwise, start with the declarations in effect and add in the text
+        // decorations that this block specifies.
+        let mut result = if style.get_box().clone_display().is_atomic_inline_level() {
+            Self::default()
+        } else {
+            style
+                .get_parent_inherited_text()
+                .text_decorations_in_effect
+                .clone()
+        };
+
+        let line = style.get_text().clone_text_decoration_line();
+
+        result.underline |= line.contains(TextDecorationLine::UNDERLINE);
+        result.overline |= line.contains(TextDecorationLine::OVERLINE);
+        result.line_through |= line.contains(TextDecorationLine::LINE_THROUGH);
+
+        result
+    }
+}
+
+/// Computed value for the text-emphasis-style property
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToCss, ToResolvedValue)]
+#[allow(missing_docs)]
+#[repr(C, u8)]
+pub enum TextEmphasisStyle {
+    /// [ <fill> || <shape> ]
+    Keyword {
+        #[css(skip_if = "TextEmphasisFillMode::is_filled")]
+        fill: TextEmphasisFillMode,
+        shape: TextEmphasisShapeKeyword,
+    },
+    /// `none`
+    None,
+    /// `<string>` (of which only the first grapheme cluster will be used).
+    String(crate::OwnedStr),
+}
diff --git a/servo/components/style/values/computed/time.rs b/servo/components/style/values/computed/time.rs
new file mode 100644
index 0000000000..5681f6fab5
--- /dev/null
+++ b/servo/components/style/values/computed/time.rs
@@ -0,0 +1,44 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed time values.
+
+use crate::values::CSSFloat;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// A computed `<time>` value.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, PartialOrd, ToResolvedValue)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+pub struct Time {
+    seconds: CSSFloat,
+}
+
+impl Time {
+    /// Creates a time value from a seconds amount.
+    pub fn from_seconds(seconds: CSSFloat) -> Self {
+        Time { seconds: seconds }
+    }
+
+    /// Returns `0s`.
+    pub fn zero() -> Self {
+        Self::from_seconds(0.0)
+    }
+
+    /// Returns the amount of seconds this time represents.
+    #[inline]
+    pub fn seconds(&self) -> CSSFloat {
+        self.seconds
+    }
+}
+
+impl ToCss for Time {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.seconds().to_css(dest)?;
+        dest.write_str("s")
+    }
+}
diff --git a/servo/components/style/values/computed/transform.rs b/servo/components/style/values/computed/transform.rs
new file mode 100644
index 0000000000..d70349ee0f
--- /dev/null
+++ b/servo/components/style/values/computed/transform.rs
@@ -0,0 +1,558 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed types for CSS values that are related to transformations.
+
+use super::CSSFloat;
+use crate::values::animated::transform::{Perspective, Scale3D, Translate3D};
+use crate::values::animated::ToAnimatedZero;
+use crate::values::computed::{Angle, Integer, Length, LengthPercentage, Number, Percentage};
+use crate::values::generics::transform as generic;
+use crate::Zero;
+use euclid::default::{Transform3D, Vector3D};
+
+pub use crate::values::generics::transform::TransformStyle;
+
+/// A single operation in a computed CSS `transform`
+pub type TransformOperation =
+    generic::GenericTransformOperation<Angle, Number, Length, Integer, LengthPercentage>;
+/// A computed CSS `transform`
+pub type Transform = generic::GenericTransform<TransformOperation>;
+
+/// The computed value of a CSS `<transform-origin>`
+pub type TransformOrigin =
+    generic::GenericTransformOrigin<LengthPercentage, LengthPercentage, Length>;
+
+/// The computed value of the `perspective()` transform function.
+pub type PerspectiveFunction = generic::PerspectiveFunction<Length>;
+
+/// A vector to represent the direction vector (rotate axis) for Rotate3D.
+pub type DirectionVector = Vector3D<CSSFloat>;
+
+impl TransformOrigin {
+    /// Returns the initial computed value for `transform-origin`.
+    #[inline]
+    pub fn initial_value() -> Self {
+        Self::new(
+            LengthPercentage::new_percent(Percentage(0.5)),
+            LengthPercentage::new_percent(Percentage(0.5)),
+            Length::new(0.),
+        )
+    }
+}
+
+/// computed value of matrix3d()
+pub type Matrix3D = generic::Matrix3D<Number>;
+
+/// computed value of matrix()
+pub type Matrix = generic::Matrix<Number>;
+
+// we rustfmt_skip here because we want the matrices to look like
+// matrices instead of being split across lines
+#[cfg_attr(rustfmt, rustfmt_skip)]
+impl Matrix3D {
+    /// Get an identity matrix
+    #[inline]
+    pub fn identity() -> Self {
+        Self {
+            m11: 1.0, m12: 0.0, m13: 0.0, m14: 0.0,
+            m21: 0.0, m22: 1.0, m23: 0.0, m24: 0.0,
+            m31: 0.0, m32: 0.0, m33: 1.0, m34: 0.0,
+            m41: 0., m42: 0., m43: 0., m44: 1.0
+        }
+    }
+
+    /// Convert to a 2D Matrix
+    #[inline]
+    pub fn into_2d(self) -> Result<Matrix, ()> {
+        if self.m13 == 0. && self.m23 == 0. &&
+           self.m31 == 0. && self.m32 == 0. &&
+           self.m33 == 1. && self.m34 == 0. &&
+           self.m14 == 0. && self.m24 == 0. &&
+           self.m43 == 0. && self.m44 == 1. {
+            Ok(Matrix {
+                a: self.m11, c: self.m21, e: self.m41,
+                b: self.m12, d: self.m22, f: self.m42,
+            })
+        } else {
+            Err(())
+        }
+    }
+
+    /// Return true if this has 3D components.
+    #[inline]
+    pub fn is_3d(&self) -> bool {
+        self.m13 != 0.0 || self.m14 != 0.0 ||
+        self.m23 != 0.0 || self.m24 != 0.0 ||
+        self.m31 != 0.0 || self.m32 != 0.0 ||
+        self.m33 != 1.0 || self.m34 != 0.0 ||
+        self.m43 != 0.0 || self.m44 != 1.0
+    }
+
+    /// Return determinant value.
+    #[inline]
+    pub fn determinant(&self) -> CSSFloat {
+        self.m14 * self.m23 * self.m32 * self.m41 -
+        self.m13 * self.m24 * self.m32 * self.m41 -
+        self.m14 * self.m22 * self.m33 * self.m41 +
+        self.m12 * self.m24 * self.m33 * self.m41 +
+        self.m13 * self.m22 * self.m34 * self.m41 -
+        self.m12 * self.m23 * self.m34 * self.m41 -
+        self.m14 * self.m23 * self.m31 * self.m42 +
+        self.m13 * self.m24 * self.m31 * self.m42 +
+        self.m14 * self.m21 * self.m33 * self.m42 -
+        self.m11 * self.m24 * self.m33 * self.m42 -
+        self.m13 * self.m21 * self.m34 * self.m42 +
+        self.m11 * self.m23 * self.m34 * self.m42 +
+        self.m14 * self.m22 * self.m31 * self.m43 -
+        self.m12 * self.m24 * self.m31 * self.m43 -
+        self.m14 * self.m21 * self.m32 * self.m43 +
+        self.m11 * self.m24 * self.m32 * self.m43 +
+        self.m12 * self.m21 * self.m34 * self.m43 -
+        self.m11 * self.m22 * self.m34 * self.m43 -
+        self.m13 * self.m22 * self.m31 * self.m44 +
+        self.m12 * self.m23 * self.m31 * self.m44 +
+        self.m13 * self.m21 * self.m32 * self.m44 -
+        self.m11 * self.m23 * self.m32 * self.m44 -
+        self.m12 * self.m21 * self.m33 * self.m44 +
+        self.m11 * self.m22 * self.m33 * self.m44
+    }
+
+    /// Transpose a matrix.
+    #[inline]
+    pub fn transpose(&self) -> Self {
+        Self {
+            m11: self.m11, m12: self.m21, m13: self.m31, m14: self.m41,
+            m21: self.m12, m22: self.m22, m23: self.m32, m24: self.m42,
+            m31: self.m13, m32: self.m23, m33: self.m33, m34: self.m43,
+            m41: self.m14, m42: self.m24, m43: self.m34, m44: self.m44,
+        }
+    }
+
+    /// Return inverse matrix.
+    pub fn inverse(&self) -> Result<Matrix3D, ()> {
+        let mut det = self.determinant();
+
+        if det == 0.0 {
+            return Err(());
+        }
+
+        det = 1.0 / det;
+        let x = Matrix3D {
+            m11: det *
+            (self.m23 * self.m34 * self.m42 - self.m24 * self.m33 * self.m42 +
+             self.m24 * self.m32 * self.m43 - self.m22 * self.m34 * self.m43 -
+             self.m23 * self.m32 * self.m44 + self.m22 * self.m33 * self.m44),
+            m12: det *
+            (self.m14 * self.m33 * self.m42 - self.m13 * self.m34 * self.m42 -
+             self.m14 * self.m32 * self.m43 + self.m12 * self.m34 * self.m43 +
+             self.m13 * self.m32 * self.m44 - self.m12 * self.m33 * self.m44),
+            m13: det *
+            (self.m13 * self.m24 * self.m42 - self.m14 * self.m23 * self.m42 +
+             self.m14 * self.m22 * self.m43 - self.m12 * self.m24 * self.m43 -
+             self.m13 * self.m22 * self.m44 + self.m12 * self.m23 * self.m44),
+            m14: det *
+            (self.m14 * self.m23 * self.m32 - self.m13 * self.m24 * self.m32 -
+             self.m14 * self.m22 * self.m33 + self.m12 * self.m24 * self.m33 +
+             self.m13 * self.m22 * self.m34 - self.m12 * self.m23 * self.m34),
+            m21: det *
+            (self.m24 * self.m33 * self.m41 - self.m23 * self.m34 * self.m41 -
+             self.m24 * self.m31 * self.m43 + self.m21 * self.m34 * self.m43 +
+             self.m23 * self.m31 * self.m44 - self.m21 * self.m33 * self.m44),
+            m22: det *
+            (self.m13 * self.m34 * self.m41 - self.m14 * self.m33 * self.m41 +
+             self.m14 * self.m31 * self.m43 - self.m11 * self.m34 * self.m43 -
+             self.m13 * self.m31 * self.m44 + self.m11 * self.m33 * self.m44),
+            m23: det *
+            (self.m14 * self.m23 * self.m41 - self.m13 * self.m24 * self.m41 -
+             self.m14 * self.m21 * self.m43 + self.m11 * self.m24 * self.m43 +
+             self.m13 * self.m21 * self.m44 - self.m11 * self.m23 * self.m44),
+            m24: det *
+            (self.m13 * self.m24 * self.m31 - self.m14 * self.m23 * self.m31 +
+             self.m14 * self.m21 * self.m33 - self.m11 * self.m24 * self.m33 -
+             self.m13 * self.m21 * self.m34 + self.m11 * self.m23 * self.m34),
+            m31: det *
+            (self.m22 * self.m34 * self.m41 - self.m24 * self.m32 * self.m41 +
+             self.m24 * self.m31 * self.m42 - self.m21 * self.m34 * self.m42 -
+             self.m22 * self.m31 * self.m44 + self.m21 * self.m32 * self.m44),
+            m32: det *
+            (self.m14 * self.m32 * self.m41 - self.m12 * self.m34 * self.m41 -
+             self.m14 * self.m31 * self.m42 + self.m11 * self.m34 * self.m42 +
+             self.m12 * self.m31 * self.m44 - self.m11 * self.m32 * self.m44),
+            m33: det *
+            (self.m12 * self.m24 * self.m41 - self.m14 * self.m22 * self.m41 +
+             self.m14 * self.m21 * self.m42 - self.m11 * self.m24 * self.m42 -
+             self.m12 * self.m21 * self.m44 + self.m11 * self.m22 * self.m44),
+            m34: det *
+            (self.m14 * self.m22 * self.m31 - self.m12 * self.m24 * self.m31 -
+             self.m14 * self.m21 * self.m32 + self.m11 * self.m24 * self.m32 +
+             self.m12 * self.m21 * self.m34 - self.m11 * self.m22 * self.m34),
+            m41: det *
+            (self.m23 * self.m32 * self.m41 - self.m22 * self.m33 * self.m41 -
+             self.m23 * self.m31 * self.m42 + self.m21 * self.m33 * self.m42 +
+             self.m22 * self.m31 * self.m43 - self.m21 * self.m32 * self.m43),
+            m42: det *
+            (self.m12 * self.m33 * self.m41 - self.m13 * self.m32 * self.m41 +
+             self.m13 * self.m31 * self.m42 - self.m11 * self.m33 * self.m42 -
+             self.m12 * self.m31 * self.m43 + self.m11 * self.m32 * self.m43),
+            m43: det *
+            (self.m13 * self.m22 * self.m41 - self.m12 * self.m23 * self.m41 -
+             self.m13 * self.m21 * self.m42 + self.m11 * self.m23 * self.m42 +
+             self.m12 * self.m21 * self.m43 - self.m11 * self.m22 * self.m43),
+            m44: det *
+            (self.m12 * self.m23 * self.m31 - self.m13 * self.m22 * self.m31 +
+             self.m13 * self.m21 * self.m32 - self.m11 * self.m23 * self.m32 -
+             self.m12 * self.m21 * self.m33 + self.m11 * self.m22 * self.m33),
+        };
+
+        Ok(x)
+    }
+
+    /// Multiply `pin * self`.
+    #[inline]
+    pub fn pre_mul_point4(&self, pin: &[f32; 4]) -> [f32; 4] {
+        [
+            pin[0] * self.m11 + pin[1] * self.m21 + pin[2] * self.m31 + pin[3] * self.m41,
+            pin[0] * self.m12 + pin[1] * self.m22 + pin[2] * self.m32 + pin[3] * self.m42,
+            pin[0] * self.m13 + pin[1] * self.m23 + pin[2] * self.m33 + pin[3] * self.m43,
+            pin[0] * self.m14 + pin[1] * self.m24 + pin[2] * self.m34 + pin[3] * self.m44,
+        ]
+    }
+
+    /// Return the multiplication of two 4x4 matrices.
+    #[inline]
+    pub fn multiply(&self, other: &Self) -> Self {
+        Matrix3D {
+            m11: self.m11 * other.m11 + self.m12 * other.m21 +
+                 self.m13 * other.m31 + self.m14 * other.m41,
+            m12: self.m11 * other.m12 + self.m12 * other.m22 +
+                 self.m13 * other.m32 + self.m14 * other.m42,
+            m13: self.m11 * other.m13 + self.m12 * other.m23 +
+                 self.m13 * other.m33 + self.m14 * other.m43,
+            m14: self.m11 * other.m14 + self.m12 * other.m24 +
+                 self.m13 * other.m34 + self.m14 * other.m44,
+            m21: self.m21 * other.m11 + self.m22 * other.m21 +
+                 self.m23 * other.m31 + self.m24 * other.m41,
+            m22: self.m21 * other.m12 + self.m22 * other.m22 +
+                 self.m23 * other.m32 + self.m24 * other.m42,
+            m23: self.m21 * other.m13 + self.m22 * other.m23 +
+                 self.m23 * other.m33 + self.m24 * other.m43,
+            m24: self.m21 * other.m14 + self.m22 * other.m24 +
+                 self.m23 * other.m34 + self.m24 * other.m44,
+            m31: self.m31 * other.m11 + self.m32 * other.m21 +
+                 self.m33 * other.m31 + self.m34 * other.m41,
+            m32: self.m31 * other.m12 + self.m32 * other.m22 +
+                 self.m33 * other.m32 + self.m34 * other.m42,
+            m33: self.m31 * other.m13 + self.m32 * other.m23 +
+                 self.m33 * other.m33 + self.m34 * other.m43,
+            m34: self.m31 * other.m14 + self.m32 * other.m24 +
+                 self.m33 * other.m34 + self.m34 * other.m44,
+            m41: self.m41 * other.m11 + self.m42 * other.m21 +
+                 self.m43 * other.m31 + self.m44 * other.m41,
+            m42: self.m41 * other.m12 + self.m42 * other.m22 +
+                 self.m43 * other.m32 + self.m44 * other.m42,
+            m43: self.m41 * other.m13 + self.m42 * other.m23 +
+                 self.m43 * other.m33 + self.m44 * other.m43,
+            m44: self.m41 * other.m14 + self.m42 * other.m24 +
+                 self.m43 * other.m34 + self.m44 * other.m44,
+        }
+    }
+
+    /// Scale the matrix by a factor.
+    #[inline]
+    pub fn scale_by_factor(&mut self, scaling_factor: CSSFloat) {
+        self.m11 *= scaling_factor;
+        self.m12 *= scaling_factor;
+        self.m13 *= scaling_factor;
+        self.m14 *= scaling_factor;
+        self.m21 *= scaling_factor;
+        self.m22 *= scaling_factor;
+        self.m23 *= scaling_factor;
+        self.m24 *= scaling_factor;
+        self.m31 *= scaling_factor;
+        self.m32 *= scaling_factor;
+        self.m33 *= scaling_factor;
+        self.m34 *= scaling_factor;
+        self.m41 *= scaling_factor;
+        self.m42 *= scaling_factor;
+        self.m43 *= scaling_factor;
+        self.m44 *= scaling_factor;
+    }
+
+    /// Return the matrix 3x3 part (top-left corner).
+    /// This is used by retrieving the scale and shear factors
+    /// during decomposing a 3d matrix.
+    #[inline]
+    pub fn get_matrix_3x3_part(&self) -> [[f32; 3]; 3] {
+        [
+            [ self.m11, self.m12, self.m13 ],
+            [ self.m21, self.m22, self.m23 ],
+            [ self.m31, self.m32, self.m33 ],
+        ]
+    }
+
+    /// Set perspective on the matrix.
+    #[inline]
+    pub fn set_perspective(&mut self, perspective: &Perspective) {
+        self.m14 = perspective.0;
+        self.m24 = perspective.1;
+        self.m34 = perspective.2;
+        self.m44 = perspective.3;
+    }
+
+    /// Apply translate on the matrix.
+    #[inline]
+    pub fn apply_translate(&mut self, translate: &Translate3D) {
+        self.m41 += translate.0 * self.m11 + translate.1 * self.m21 + translate.2 * self.m31;
+        self.m42 += translate.0 * self.m12 + translate.1 * self.m22 + translate.2 * self.m32;
+        self.m43 += translate.0 * self.m13 + translate.1 * self.m23 + translate.2 * self.m33;
+        self.m44 += translate.0 * self.m14 + translate.1 * self.m24 + translate.2 * self.m34;
+    }
+
+    /// Apply scale on the matrix.
+    #[inline]
+    pub fn apply_scale(&mut self, scale: &Scale3D) {
+        self.m11 *= scale.0;
+        self.m12 *= scale.0;
+        self.m13 *= scale.0;
+        self.m14 *= scale.0;
+        self.m21 *= scale.1;
+        self.m22 *= scale.1;
+        self.m23 *= scale.1;
+        self.m24 *= scale.1;
+        self.m31 *= scale.2;
+        self.m32 *= scale.2;
+        self.m33 *= scale.2;
+        self.m34 *= scale.2;
+    }
+}
+
+#[cfg_attr(rustfmt, rustfmt_skip)]
+impl Matrix {
+    #[inline]
+    /// Get an identity matrix
+    pub fn identity() -> Self {
+        Self {
+            a: 1., c: 0., /* 0      0*/
+            b: 0., d: 1., /* 0      0*/
+            /* 0      0      1      0 */
+            e: 0., f: 0., /* 0      1 */
+        }
+    }
+}
+
+#[cfg_attr(rustfmt, rustfmt_skip)]
+impl From<Matrix> for Matrix3D {
+    fn from(m: Matrix) -> Self {
+        Self {
+            m11: m.a, m12: m.b, m13: 0.0, m14: 0.0,
+            m21: m.c, m22: m.d, m23: 0.0, m24: 0.0,
+            m31: 0.0, m32: 0.0, m33: 1.0, m34: 0.0,
+            m41: m.e, m42: m.f, m43: 0.0, m44: 1.0
+        }
+    }
+}
+
+#[cfg_attr(rustfmt, rustfmt_skip)]
+impl From<Transform3D<CSSFloat>> for Matrix3D {
+    #[inline]
+    fn from(m: Transform3D<CSSFloat>) -> Self {
+        Matrix3D {
+            m11: m.m11, m12: m.m12, m13: m.m13, m14: m.m14,
+            m21: m.m21, m22: m.m22, m23: m.m23, m24: m.m24,
+            m31: m.m31, m32: m.m32, m33: m.m33, m34: m.m34,
+            m41: m.m41, m42: m.m42, m43: m.m43, m44: m.m44
+        }
+    }
+}
+
+impl TransformOperation {
+    /// Convert to a Translate3D.
+    ///
+    /// Must be called on a Translate function
+    pub fn to_translate_3d(&self) -> Self {
+        match *self {
+            generic::TransformOperation::Translate3D(..) => self.clone(),
+            generic::TransformOperation::TranslateX(ref x) => {
+                generic::TransformOperation::Translate3D(
+                    x.clone(),
+                    LengthPercentage::zero(),
+                    Length::zero(),
+                )
+            },
+            generic::TransformOperation::Translate(ref x, ref y) => {
+                generic::TransformOperation::Translate3D(x.clone(), y.clone(), Length::zero())
+            },
+            generic::TransformOperation::TranslateY(ref y) => {
+                generic::TransformOperation::Translate3D(
+                    LengthPercentage::zero(),
+                    y.clone(),
+                    Length::zero(),
+                )
+            },
+            generic::TransformOperation::TranslateZ(ref z) => {
+                generic::TransformOperation::Translate3D(
+                    LengthPercentage::zero(),
+                    LengthPercentage::zero(),
+                    z.clone(),
+                )
+            },
+            _ => unreachable!(),
+        }
+    }
+
+    /// Convert to a Rotate3D.
+    ///
+    /// Must be called on a Rotate function.
+    pub fn to_rotate_3d(&self) -> Self {
+        match *self {
+            generic::TransformOperation::Rotate3D(..) => self.clone(),
+            generic::TransformOperation::RotateZ(ref angle) |
+            generic::TransformOperation::Rotate(ref angle) => {
+                generic::TransformOperation::Rotate3D(0., 0., 1., angle.clone())
+            },
+            generic::TransformOperation::RotateX(ref angle) => {
+                generic::TransformOperation::Rotate3D(1., 0., 0., angle.clone())
+            },
+            generic::TransformOperation::RotateY(ref angle) => {
+                generic::TransformOperation::Rotate3D(0., 1., 0., angle.clone())
+            },
+            _ => unreachable!(),
+        }
+    }
+
+    /// Convert to a Scale3D.
+    ///
+    /// Must be called on a Scale function
+    pub fn to_scale_3d(&self) -> Self {
+        match *self {
+            generic::TransformOperation::Scale3D(..) => self.clone(),
+            generic::TransformOperation::Scale(x, y) => {
+                generic::TransformOperation::Scale3D(x, y, 1.)
+            },
+            generic::TransformOperation::ScaleX(x) => {
+                generic::TransformOperation::Scale3D(x, 1., 1.)
+            },
+            generic::TransformOperation::ScaleY(y) => {
+                generic::TransformOperation::Scale3D(1., y, 1.)
+            },
+            generic::TransformOperation::ScaleZ(z) => {
+                generic::TransformOperation::Scale3D(1., 1., z)
+            },
+            _ => unreachable!(),
+        }
+    }
+}
+
+/// Build an equivalent 'identity transform function list' based
+/// on an existing transform list.
+/// http://dev.w3.org/csswg/css-transforms/#none-transform-animation
+impl ToAnimatedZero for TransformOperation {
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        match *self {
+            generic::TransformOperation::Matrix3D(..) => {
+                Ok(generic::TransformOperation::Matrix3D(Matrix3D::identity()))
+            },
+            generic::TransformOperation::Matrix(..) => {
+                Ok(generic::TransformOperation::Matrix(Matrix::identity()))
+            },
+            generic::TransformOperation::Skew(sx, sy) => Ok(generic::TransformOperation::Skew(
+                sx.to_animated_zero()?,
+                sy.to_animated_zero()?,
+            )),
+            generic::TransformOperation::SkewX(s) => {
+                Ok(generic::TransformOperation::SkewX(s.to_animated_zero()?))
+            },
+            generic::TransformOperation::SkewY(s) => {
+                Ok(generic::TransformOperation::SkewY(s.to_animated_zero()?))
+            },
+            generic::TransformOperation::Translate3D(ref tx, ref ty, ref tz) => {
+                Ok(generic::TransformOperation::Translate3D(
+                    tx.to_animated_zero()?,
+                    ty.to_animated_zero()?,
+                    tz.to_animated_zero()?,
+                ))
+            },
+            generic::TransformOperation::Translate(ref tx, ref ty) => {
+                Ok(generic::TransformOperation::Translate(
+                    tx.to_animated_zero()?,
+                    ty.to_animated_zero()?,
+                ))
+            },
+            generic::TransformOperation::TranslateX(ref t) => Ok(
+                generic::TransformOperation::TranslateX(t.to_animated_zero()?),
+            ),
+            generic::TransformOperation::TranslateY(ref t) => Ok(
+                generic::TransformOperation::TranslateY(t.to_animated_zero()?),
+            ),
+            generic::TransformOperation::TranslateZ(ref t) => Ok(
+                generic::TransformOperation::TranslateZ(t.to_animated_zero()?),
+            ),
+            generic::TransformOperation::Scale3D(..) => {
+                Ok(generic::TransformOperation::Scale3D(1.0, 1.0, 1.0))
+            },
+            generic::TransformOperation::Scale(_, _) => {
+                Ok(generic::TransformOperation::Scale(1.0, 1.0))
+            },
+            generic::TransformOperation::ScaleX(..) => Ok(generic::TransformOperation::ScaleX(1.0)),
+            generic::TransformOperation::ScaleY(..) => Ok(generic::TransformOperation::ScaleY(1.0)),
+            generic::TransformOperation::ScaleZ(..) => Ok(generic::TransformOperation::ScaleZ(1.0)),
+            generic::TransformOperation::Rotate3D(x, y, z, a) => {
+                let (x, y, z, _) = generic::get_normalized_vector_and_angle(x, y, z, a);
+                Ok(generic::TransformOperation::Rotate3D(
+                    x,
+                    y,
+                    z,
+                    Angle::zero(),
+                ))
+            },
+            generic::TransformOperation::RotateX(_) => {
+                Ok(generic::TransformOperation::RotateX(Angle::zero()))
+            },
+            generic::TransformOperation::RotateY(_) => {
+                Ok(generic::TransformOperation::RotateY(Angle::zero()))
+            },
+            generic::TransformOperation::RotateZ(_) => {
+                Ok(generic::TransformOperation::RotateZ(Angle::zero()))
+            },
+            generic::TransformOperation::Rotate(_) => {
+                Ok(generic::TransformOperation::Rotate(Angle::zero()))
+            },
+            generic::TransformOperation::Perspective(_) => Ok(
+                generic::TransformOperation::Perspective(generic::PerspectiveFunction::None),
+            ),
+            generic::TransformOperation::AccumulateMatrix { .. } |
+            generic::TransformOperation::InterpolateMatrix { .. } => {
+                // AccumulateMatrix/InterpolateMatrix: We do interpolation on
+                //     AccumulateMatrix/InterpolateMatrix by reading it as a ComputedMatrix
+                //     (with layout information), and then do matrix interpolation.
+                //
+                // Therefore, we use an identity matrix to represent the identity transform list.
+                // http://dev.w3.org/csswg/css-transforms/#identity-transform-function
+                Ok(generic::TransformOperation::Matrix3D(Matrix3D::identity()))
+            },
+        }
+    }
+}
+
+impl ToAnimatedZero for Transform {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Ok(generic::Transform(
+            self.0
+                .iter()
+                .map(|op| op.to_animated_zero())
+                .collect::<Result<crate::OwnedSlice<_>, _>>()?,
+        ))
+    }
+}
+
+/// A computed CSS `rotate`
+pub type Rotate = generic::GenericRotate<Number, Angle>;
+
+/// A computed CSS `translate`
+pub type Translate = generic::GenericTranslate<LengthPercentage, Length>;
+
+/// A computed CSS `scale`
+pub type Scale = generic::GenericScale<Number>;
diff --git a/servo/components/style/values/computed/ui.rs b/servo/components/style/values/computed/ui.rs
new file mode 100644
index 0000000000..6fa5137adf
--- /dev/null
+++ b/servo/components/style/values/computed/ui.rs
@@ -0,0 +1,22 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Computed values for UI properties
+
+use crate::values::computed::color::Color;
+use crate::values::computed::image::Image;
+use crate::values::computed::Number;
+use crate::values::generics::ui as generics;
+
+pub use crate::values::specified::ui::CursorKind;
+pub use crate::values::specified::ui::{BoolInteger, UserSelect};
+
+/// A computed value for the `cursor` property.
+pub type Cursor = generics::GenericCursor<CursorImage>;
+
+/// A computed value for item of `image cursors`.
+pub type CursorImage = generics::GenericCursorImage<Image, Number>;
+
+/// A computed value for `scrollbar-color` property.
+pub type ScrollbarColor = generics::GenericScrollbarColor<Color>;
diff --git a/servo/components/style/values/computed/url.rs b/servo/components/style/values/computed/url.rs
new file mode 100644
index 0000000000..9f0d8f5bb3
--- /dev/null
+++ b/servo/components/style/values/computed/url.rs
@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Common handling for the computed value CSS url() values.
+
+use crate::values::generics::url::UrlOrNone as GenericUrlOrNone;
+
+#[cfg(feature = "gecko")]
+pub use crate::gecko::url::{ComputedImageUrl, ComputedUrl};
+#[cfg(feature = "servo")]
+pub use crate::servo::url::{ComputedImageUrl, ComputedUrl};
+
+/// Computed <url> | <none>
+pub type UrlOrNone = GenericUrlOrNone<ComputedUrl>;
diff --git a/servo/components/style/values/distance.rs b/servo/components/style/values/distance.rs
new file mode 100644
index 0000000000..fef376cf5f
--- /dev/null
+++ b/servo/components/style/values/distance.rs
@@ -0,0 +1,138 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Machinery to compute distances between animatable values.
+
+use app_units::Au;
+use euclid::default::Size2D;
+use std::iter::Sum;
+use std::ops::Add;
+
+/// A trait to compute squared distances between two animatable values.
+///
+/// This trait is derivable with `#[derive(ComputeSquaredDistance)]`. The derived
+/// implementation uses a `match` expression with identical patterns for both
+/// `self` and `other`, calling `ComputeSquaredDistance::compute_squared_distance`
+/// on each fields of the values.
+///
+/// If a variant is annotated with `#[animation(error)]`, the corresponding
+/// `match` arm returns an error.
+///
+/// Trait bounds for type parameter `Foo` can be opted out of with
+/// `#[animation(no_bound(Foo))]` on the type definition, trait bounds for
+/// fields can be opted into with `#[distance(field_bound)]` on the field.
+pub trait ComputeSquaredDistance {
+    /// Computes the squared distance between two animatable values.
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()>;
+}
+
+/// A distance between two animatable values.
+#[derive(Add, Clone, Copy, Debug, From)]
+pub struct SquaredDistance {
+    value: f64,
+}
+
+impl SquaredDistance {
+    /// Returns a squared distance from its square root.
+    #[inline]
+    pub fn from_sqrt(sqrt: f64) -> Self {
+        Self { value: sqrt * sqrt }
+    }
+}
+
+impl ComputeSquaredDistance for u16 {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        Ok(SquaredDistance::from_sqrt(
+            ((*self as f64) - (*other as f64)).abs(),
+        ))
+    }
+}
+
+impl ComputeSquaredDistance for i16 {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        Ok(SquaredDistance::from_sqrt((*self - *other).abs() as f64))
+    }
+}
+
+impl ComputeSquaredDistance for i32 {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        Ok(SquaredDistance::from_sqrt((*self - *other).abs() as f64))
+    }
+}
+
+impl ComputeSquaredDistance for f32 {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        Ok(SquaredDistance::from_sqrt((*self - *other).abs() as f64))
+    }
+}
+
+impl ComputeSquaredDistance for f64 {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        Ok(SquaredDistance::from_sqrt((*self - *other).abs()))
+    }
+}
+
+impl ComputeSquaredDistance for Au {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        self.0.compute_squared_distance(&other.0)
+    }
+}
+
+impl<T> ComputeSquaredDistance for Box<T>
+where
+    T: ComputeSquaredDistance,
+{
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        (**self).compute_squared_distance(&**other)
+    }
+}
+
+impl<T> ComputeSquaredDistance for Option<T>
+where
+    T: ComputeSquaredDistance,
+{
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        match (self.as_ref(), other.as_ref()) {
+            (Some(this), Some(other)) => this.compute_squared_distance(other),
+            (None, None) => Ok(SquaredDistance::from_sqrt(0.)),
+            _ => Err(()),
+        }
+    }
+}
+
+impl<T> ComputeSquaredDistance for Size2D<T>
+where
+    T: ComputeSquaredDistance,
+{
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        Ok(self.width.compute_squared_distance(&other.width)? +
+            self.height.compute_squared_distance(&other.height)?)
+    }
+}
+
+impl SquaredDistance {
+    /// Returns the square root of this squared distance.
+    #[inline]
+    pub fn sqrt(self) -> f64 {
+        self.value.sqrt()
+    }
+}
+
+impl Sum for SquaredDistance {
+    fn sum<I>(iter: I) -> Self
+    where
+        I: Iterator<Item = Self>,
+    {
+        iter.fold(SquaredDistance::from_sqrt(0.), Add::add)
+    }
+}
diff --git a/servo/components/style/values/generics/background.rs b/servo/components/style/values/generics/background.rs
new file mode 100644
index 0000000000..d9b6624595
--- /dev/null
+++ b/servo/components/style/values/generics/background.rs
@@ -0,0 +1,54 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to backgrounds.
+
+use crate::values::generics::length::{GenericLengthPercentageOrAuto, LengthPercentageOrAuto};
+
+/// A generic value for the `background-size` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericBackgroundSize<LengthPercent> {
+    /// `<width> <height>`
+    ExplicitSize {
+        /// Explicit width.
+        width: GenericLengthPercentageOrAuto<LengthPercent>,
+        /// Explicit height.
+        #[css(skip_if = "GenericLengthPercentageOrAuto::is_auto")]
+        height: GenericLengthPercentageOrAuto<LengthPercent>,
+    },
+    /// `cover`
+    #[animation(error)]
+    Cover,
+    /// `contain`
+    #[animation(error)]
+    Contain,
+}
+
+pub use self::GenericBackgroundSize as BackgroundSize;
+
+impl<LengthPercentage> BackgroundSize<LengthPercentage> {
+    /// Returns `auto auto`.
+    pub fn auto() -> Self {
+        GenericBackgroundSize::ExplicitSize {
+            width: LengthPercentageOrAuto::Auto,
+            height: LengthPercentageOrAuto::Auto,
+        }
+    }
+}
diff --git a/servo/components/style/values/generics/basic_shape.rs b/servo/components/style/values/generics/basic_shape.rs
new file mode 100644
index 0000000000..5af1580ffd
--- /dev/null
+++ b/servo/components/style/values/generics/basic_shape.rs
@@ -0,0 +1,535 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the [`basic-shape`](https://drafts.csswg.org/css-shapes/#typedef-basic-shape)
+//! types that are generic over their `ToCss` implementations.
+
+use crate::values::animated::{Animate, Procedure, ToAnimatedZero};
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::generics::border::GenericBorderRadius;
+use crate::values::generics::position::GenericPosition;
+use crate::values::generics::rect::Rect;
+use crate::values::specified::SVGPathData;
+use crate::Zero;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// <https://drafts.fxtf.org/css-masking-1/#typedef-geometry-box>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ShapeGeometryBox {
+    /// Depending on which kind of element this style value applied on, the
+    /// default value of the reference-box can be different.  For an HTML
+    /// element, the default value of reference-box is border-box; for an SVG
+    /// element, the default value is fill-box.  Since we can not determine the
+    /// default value at parsing time, we keep this value to make a decision on
+    /// it.
+    #[css(skip)]
+    ElementDependent,
+    FillBox,
+    StrokeBox,
+    ViewBox,
+    ShapeBox(ShapeBox),
+}
+
+impl Default for ShapeGeometryBox {
+    fn default() -> Self {
+        Self::ElementDependent
+    }
+}
+
+/// https://drafts.csswg.org/css-shapes-1/#typedef-shape-box
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    Copy,
+    ComputeSquaredDistance,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ShapeBox {
+    MarginBox,
+    BorderBox,
+    PaddingBox,
+    ContentBox,
+}
+
+impl Default for ShapeBox {
+    fn default() -> Self {
+        ShapeBox::MarginBox
+    }
+}
+
+/// A value for the `clip-path` property.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[animation(no_bound(U))]
+#[repr(u8)]
+pub enum GenericClipPath<BasicShape, U> {
+    #[animation(error)]
+    None,
+    #[animation(error)]
+    Url(U),
+    #[css(function)]
+    Path(Path),
+    Shape(
+        Box<BasicShape>,
+        #[css(skip_if = "is_default")] ShapeGeometryBox,
+    ),
+    #[animation(error)]
+    Box(ShapeGeometryBox),
+}
+
+pub use self::GenericClipPath as ClipPath;
+
+/// A value for the `shape-outside` property.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[animation(no_bound(I))]
+#[repr(u8)]
+pub enum GenericShapeOutside<BasicShape, I> {
+    #[animation(error)]
+    None,
+    #[animation(error)]
+    Image(I),
+    Shape(Box<BasicShape>, #[css(skip_if = "is_default")] ShapeBox),
+    #[animation(error)]
+    Box(ShapeBox),
+}
+
+pub use self::GenericShapeOutside as ShapeOutside;
+
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericBasicShape<H, V, LengthPercentage, NonNegativeLengthPercentage> {
+    Inset(
+        #[css(field_bound)]
+        #[shmem(field_bound)]
+        InsetRect<LengthPercentage, NonNegativeLengthPercentage>,
+    ),
+    Circle(
+        #[css(field_bound)]
+        #[shmem(field_bound)]
+        Circle<H, V, NonNegativeLengthPercentage>,
+    ),
+    Ellipse(
+        #[css(field_bound)]
+        #[shmem(field_bound)]
+        Ellipse<H, V, NonNegativeLengthPercentage>,
+    ),
+    Polygon(GenericPolygon<LengthPercentage>),
+}
+
+pub use self::GenericBasicShape as BasicShape;
+
+/// <https://drafts.csswg.org/css-shapes/#funcdef-inset>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function = "inset")]
+#[repr(C)]
+pub struct InsetRect<LengthPercentage, NonNegativeLengthPercentage> {
+    pub rect: Rect<LengthPercentage>,
+    #[shmem(field_bound)]
+    pub round: GenericBorderRadius<NonNegativeLengthPercentage>,
+}
+
+/// <https://drafts.csswg.org/css-shapes/#funcdef-circle>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function)]
+#[repr(C)]
+pub struct Circle<H, V, NonNegativeLengthPercentage> {
+    pub position: GenericPosition<H, V>,
+    pub radius: GenericShapeRadius<NonNegativeLengthPercentage>,
+}
+
+/// <https://drafts.csswg.org/css-shapes/#funcdef-ellipse>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function)]
+#[repr(C)]
+pub struct Ellipse<H, V, NonNegativeLengthPercentage> {
+    pub position: GenericPosition<H, V>,
+    pub semiaxis_x: GenericShapeRadius<NonNegativeLengthPercentage>,
+    pub semiaxis_y: GenericShapeRadius<NonNegativeLengthPercentage>,
+}
+
+/// <https://drafts.csswg.org/css-shapes/#typedef-shape-radius>
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericShapeRadius<NonNegativeLengthPercentage> {
+    Length(NonNegativeLengthPercentage),
+    #[animation(error)]
+    ClosestSide,
+    #[animation(error)]
+    FarthestSide,
+}
+
+pub use self::GenericShapeRadius as ShapeRadius;
+
+/// A generic type for representing the `polygon()` function
+///
+/// <https://drafts.csswg.org/css-shapes/#funcdef-polygon>
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma, function = "polygon")]
+#[repr(C)]
+pub struct GenericPolygon<LengthPercentage> {
+    /// The filling rule for a polygon.
+    #[css(skip_if = "is_default")]
+    pub fill: FillRule,
+    /// A collection of (x, y) coordinates to draw the polygon.
+    #[css(iterable)]
+    pub coordinates: crate::OwnedSlice<PolygonCoord<LengthPercentage>>,
+}
+
+pub use self::GenericPolygon as Polygon;
+
+/// Coordinates for Polygon.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct PolygonCoord<LengthPercentage>(pub LengthPercentage, pub LengthPercentage);
+
+// https://drafts.csswg.org/css-shapes/#typedef-fill-rule
+// NOTE: Basic shapes spec says that these are the only two values, however
+// https://www.w3.org/TR/SVG/painting.html#FillRuleProperty
+// says that it can also be `inherit`
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum FillRule {
+    Nonzero,
+    Evenodd,
+}
+
+/// The path function defined in css-shape-2.
+///
+/// https://drafts.csswg.org/css-shapes-2/#funcdef-path
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma)]
+#[repr(C)]
+pub struct Path {
+    /// The filling rule for the svg path.
+    #[css(skip_if = "is_default")]
+    #[animation(constant)]
+    pub fill: FillRule,
+    /// The svg path data.
+    pub path: SVGPathData,
+}
+
+impl<B, U> ToAnimatedZero for ClipPath<B, U> {
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+impl<B, U> ToAnimatedZero for ShapeOutside<B, U> {
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+impl<Length, NonNegativeLength> ToCss for InsetRect<Length, NonNegativeLength>
+where
+    Length: ToCss + PartialEq,
+    NonNegativeLength: ToCss + PartialEq + Zero,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("inset(")?;
+        self.rect.to_css(dest)?;
+        if !self.round.is_zero() {
+            dest.write_str(" round ")?;
+            self.round.to_css(dest)?;
+        }
+        dest.write_str(")")
+    }
+}
+
+impl<H, V, NonNegativeLengthPercentage> ToCss for Circle<H, V, NonNegativeLengthPercentage>
+where
+    GenericPosition<H, V>: ToCss,
+    NonNegativeLengthPercentage: ToCss + PartialEq,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("circle(")?;
+        if self.radius != Default::default() {
+            self.radius.to_css(dest)?;
+            dest.write_str(" ")?;
+        }
+        dest.write_str("at ")?;
+        self.position.to_css(dest)?;
+        dest.write_str(")")
+    }
+}
+
+impl<H, V, NonNegativeLengthPercentage> ToCss for Ellipse<H, V, NonNegativeLengthPercentage>
+where
+    GenericPosition<H, V>: ToCss,
+    NonNegativeLengthPercentage: ToCss + PartialEq,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("ellipse(")?;
+        if self.semiaxis_x != Default::default() || self.semiaxis_y != Default::default() {
+            self.semiaxis_x.to_css(dest)?;
+            dest.write_str(" ")?;
+            self.semiaxis_y.to_css(dest)?;
+            dest.write_str(" ")?;
+        }
+        dest.write_str("at ")?;
+        self.position.to_css(dest)?;
+        dest.write_str(")")
+    }
+}
+
+impl<L> Default for ShapeRadius<L> {
+    #[inline]
+    fn default() -> Self {
+        ShapeRadius::ClosestSide
+    }
+}
+
+impl<L> Animate for Polygon<L>
+where
+    L: Animate,
+{
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        if self.fill != other.fill {
+            return Err(());
+        }
+        if self.coordinates.len() != other.coordinates.len() {
+            return Err(());
+        }
+        let coordinates = self
+            .coordinates
+            .iter()
+            .zip(other.coordinates.iter())
+            .map(|(this, other)| {
+                Ok(PolygonCoord(
+                    this.0.animate(&other.0, procedure)?,
+                    this.1.animate(&other.1, procedure)?,
+                ))
+            })
+            .collect::<Result<Vec<_>, _>>()?
+            .into();
+        Ok(Polygon {
+            fill: self.fill,
+            coordinates,
+        })
+    }
+}
+
+impl<L> ComputeSquaredDistance for Polygon<L>
+where
+    L: ComputeSquaredDistance,
+{
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        if self.fill != other.fill {
+            return Err(());
+        }
+        if self.coordinates.len() != other.coordinates.len() {
+            return Err(());
+        }
+        self.coordinates
+            .iter()
+            .zip(other.coordinates.iter())
+            .map(|(this, other)| {
+                let d1 = this.0.compute_squared_distance(&other.0)?;
+                let d2 = this.1.compute_squared_distance(&other.1)?;
+                Ok(d1 + d2)
+            })
+            .sum()
+    }
+}
+
+impl Default for FillRule {
+    #[inline]
+    fn default() -> Self {
+        FillRule::Nonzero
+    }
+}
+
+#[inline]
+fn is_default<T: Default + PartialEq>(fill: &T) -> bool {
+    *fill == Default::default()
+}
diff --git a/servo/components/style/values/generics/border.rs b/servo/components/style/values/generics/border.rs
new file mode 100644
index 0000000000..e4e78e3122
--- /dev/null
+++ b/servo/components/style/values/generics/border.rs
@@ -0,0 +1,257 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to borders.
+
+use crate::values::generics::rect::Rect;
+use crate::values::generics::size::Size2D;
+use crate::Zero;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// A generic value for a single side of a `border-image-width` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericBorderImageSideWidth<LP, N> {
+    /// `<number>`
+    ///
+    /// NOTE: Numbers need to be before length-percentagess, in order to parse
+    /// them first, since `0` should be a number, not the `0px` length.
+    Number(N),
+    /// `<length-or-percentage>`
+    LengthPercentage(LP),
+    /// `auto`
+    Auto,
+}
+
+pub use self::GenericBorderImageSideWidth as BorderImageSideWidth;
+
+/// A generic value for the `border-image-slice` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericBorderImageSlice<NumberOrPercentage> {
+    /// The offsets.
+    #[css(field_bound)]
+    pub offsets: Rect<NumberOrPercentage>,
+    /// Whether to fill the middle part.
+    #[animation(constant)]
+    #[css(represents_keyword)]
+    pub fill: bool,
+}
+
+pub use self::GenericBorderImageSlice as BorderImageSlice;
+
+/// A generic value for the `border-*-radius` longhand properties.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericBorderCornerRadius<L>(
+    #[css(field_bound)]
+    #[shmem(field_bound)]
+    pub Size2D<L>,
+);
+
+pub use self::GenericBorderCornerRadius as BorderCornerRadius;
+
+impl<L> BorderCornerRadius<L> {
+    /// Trivially create a `BorderCornerRadius`.
+    pub fn new(w: L, h: L) -> Self {
+        BorderCornerRadius(Size2D::new(w, h))
+    }
+}
+
+impl<L: Zero> Zero for BorderCornerRadius<L> {
+    fn zero() -> Self {
+        BorderCornerRadius(Size2D::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        self.0.is_zero()
+    }
+}
+
+/// A generic value for the `border-spacing` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct BorderSpacing<L>(
+    #[css(field_bound)]
+    #[shmem(field_bound)]
+    pub Size2D<L>,
+);
+
+impl<L> BorderSpacing<L> {
+    /// Trivially create a `BorderCornerRadius`.
+    pub fn new(w: L, h: L) -> Self {
+        BorderSpacing(Size2D::new(w, h))
+    }
+}
+
+/// A generic value for `border-radius` and `inset()`.
+///
+/// <https://drafts.csswg.org/css-backgrounds-3/#border-radius>
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericBorderRadius<LengthPercentage> {
+    /// The top left radius.
+    #[shmem(field_bound)]
+    pub top_left: GenericBorderCornerRadius<LengthPercentage>,
+    /// The top right radius.
+    pub top_right: GenericBorderCornerRadius<LengthPercentage>,
+    /// The bottom right radius.
+    pub bottom_right: GenericBorderCornerRadius<LengthPercentage>,
+    /// The bottom left radius.
+    pub bottom_left: GenericBorderCornerRadius<LengthPercentage>,
+}
+
+pub use self::GenericBorderRadius as BorderRadius;
+
+impl<L> BorderRadius<L> {
+    /// Returns a new `BorderRadius<L>`.
+    #[inline]
+    pub fn new(
+        tl: BorderCornerRadius<L>,
+        tr: BorderCornerRadius<L>,
+        br: BorderCornerRadius<L>,
+        bl: BorderCornerRadius<L>,
+    ) -> Self {
+        BorderRadius {
+            top_left: tl,
+            top_right: tr,
+            bottom_right: br,
+            bottom_left: bl,
+        }
+    }
+
+    /// Serialises two given rects following the syntax of the `border-radius``
+    /// property.
+    pub fn serialize_rects<W>(
+        widths: Rect<&L>,
+        heights: Rect<&L>,
+        dest: &mut CssWriter<W>,
+    ) -> fmt::Result
+    where
+        L: PartialEq + ToCss,
+        W: Write,
+    {
+        widths.to_css(dest)?;
+        if widths != heights {
+            dest.write_str(" / ")?;
+            heights.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+impl<L: Zero> Zero for BorderRadius<L> {
+    fn zero() -> Self {
+        Self::new(
+            BorderCornerRadius::<L>::zero(),
+            BorderCornerRadius::<L>::zero(),
+            BorderCornerRadius::<L>::zero(),
+            BorderCornerRadius::<L>::zero(),
+        )
+    }
+
+    fn is_zero(&self) -> bool {
+        self.top_left.is_zero() &&
+            self.top_right.is_zero() &&
+            self.bottom_right.is_zero() &&
+            self.bottom_left.is_zero()
+    }
+}
+
+impl<L> ToCss for BorderRadius<L>
+where
+    L: PartialEq + ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let BorderRadius {
+            top_left: BorderCornerRadius(ref tl),
+            top_right: BorderCornerRadius(ref tr),
+            bottom_right: BorderCornerRadius(ref br),
+            bottom_left: BorderCornerRadius(ref bl),
+        } = *self;
+
+        let widths = Rect::new(&tl.width, &tr.width, &br.width, &bl.width);
+        let heights = Rect::new(&tl.height, &tr.height, &br.height, &bl.height);
+
+        Self::serialize_rects(widths, heights, dest)
+    }
+}
diff --git a/servo/components/style/values/generics/box.rs b/servo/components/style/values/generics/box.rs
new file mode 100644
index 0000000000..1885017cc2
--- /dev/null
+++ b/servo/components/style/values/generics/box.rs
@@ -0,0 +1,229 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for box properties.
+
+use crate::values::animated::ToAnimatedZero;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    FromPrimitive,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+#[allow(missing_docs)]
+pub enum VerticalAlignKeyword {
+    Baseline,
+    Sub,
+    Super,
+    Top,
+    TextTop,
+    Middle,
+    Bottom,
+    TextBottom,
+    #[cfg(feature = "gecko")]
+    MozMiddleWithBaseline,
+}
+
+/// A generic value for the `vertical-align` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericVerticalAlign<LengthPercentage> {
+    /// One of the vertical-align keywords.
+    Keyword(VerticalAlignKeyword),
+    /// `<length-percentage>`
+    Length(LengthPercentage),
+}
+
+pub use self::GenericVerticalAlign as VerticalAlign;
+
+impl<L> VerticalAlign<L> {
+    /// Returns `baseline`.
+    #[inline]
+    pub fn baseline() -> Self {
+        VerticalAlign::Keyword(VerticalAlignKeyword::Baseline)
+    }
+}
+
+impl<L> ToAnimatedZero for VerticalAlign<L> {
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+/// https://drafts.csswg.org/css-sizing-4/#intrinsic-size-override
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[value_info(other_values = "auto")]
+#[repr(C, u8)]
+pub enum GenericContainIntrinsicSize<L> {
+    /// The keyword `none`.
+    None,
+    /// A non-negative length.
+    Length(L),
+    /// "auto <Length>"
+    AutoLength(L),
+}
+
+pub use self::GenericContainIntrinsicSize as ContainIntrinsicSize;
+
+impl<L: ToCss> ToCss for ContainIntrinsicSize<L> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            Self::None => dest.write_str("none"),
+            Self::Length(ref l) => l.to_css(dest),
+            Self::AutoLength(ref l) => {
+                dest.write_str("auto ")?;
+                l.to_css(dest)
+            },
+        }
+    }
+}
+
+/// Note that we only implement -webkit-line-clamp as a single, longhand
+/// property for now, but the spec defines line-clamp as a shorthand for
+/// separate max-lines, block-ellipsis, and continue properties.
+///
+/// https://drafts.csswg.org/css-overflow-3/#line-clamp
+#[derive(
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+#[value_info(other_values = "none")]
+pub struct GenericLineClamp<I>(pub I);
+
+pub use self::GenericLineClamp as LineClamp;
+
+impl<I: crate::Zero> LineClamp<I> {
+    /// Returns the `none` value.
+    pub fn none() -> Self {
+        Self(crate::Zero::zero())
+    }
+
+    /// Returns whether we're the `none` value.
+    pub fn is_none(&self) -> bool {
+        self.0.is_zero()
+    }
+}
+
+impl<I: crate::Zero + ToCss> ToCss for LineClamp<I> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.is_none() {
+            return dest.write_str("none");
+        }
+        self.0.to_css(dest)
+    }
+}
+
+/// https://drafts.csswg.org/css-animations/#animation-iteration-count
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum GenericAnimationIterationCount<Number> {
+    /// A `<number>` value.
+    Number(Number),
+    /// The `infinite` keyword.
+    Infinite,
+}
+
+pub use self::GenericAnimationIterationCount as AnimationIterationCount;
+
+/// A generic value for the `perspective` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericPerspective<NonNegativeLength> {
+    /// A non-negative length.
+    Length(NonNegativeLength),
+    /// The keyword `none`.
+    None,
+}
+
+pub use self::GenericPerspective as Perspective;
+
+impl<L> Perspective<L> {
+    /// Returns `none`.
+    #[inline]
+    pub fn none() -> Self {
+        Perspective::None
+    }
+}
diff --git a/servo/components/style/values/generics/calc.rs b/servo/components/style/values/generics/calc.rs
new file mode 100644
index 0000000000..24b0cf23a3
--- /dev/null
+++ b/servo/components/style/values/generics/calc.rs
@@ -0,0 +1,1104 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! [Calc expressions][calc].
+//!
+//! [calc]: https://drafts.csswg.org/css-values/#calc-notation
+
+use num_traits::{Float, Zero};
+use smallvec::SmallVec;
+use std::fmt::{self, Write};
+use std::ops::{Add, Div, Mul, Rem, Sub};
+use std::{cmp, mem};
+use style_traits::{CssWriter, ToCss};
+
+/// Whether we're a `min` or `max` function.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    ToAnimatedZero,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum MinMaxOp {
+    /// `min()`
+    Min,
+    /// `max()`
+    Max,
+}
+
+/// Whether we're a `mod` or `rem` function.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    ToAnimatedZero,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ModRemOp {
+    /// `mod()`
+    Mod,
+    /// `rem()`
+    Rem,
+}
+
+/// The strategy used in `round()`
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    ToAnimatedZero,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum RoundingStrategy {
+    /// `round(nearest, a, b)`
+    /// round a to the nearest multiple of b
+    Nearest,
+    /// `round(up, a, b)`
+    /// round a up to the nearest multiple of b
+    Up,
+    /// `round(down, a, b)`
+    /// round a down to the nearest multiple of b
+    Down,
+    /// `round(to-zero, a, b)`
+    /// round a to the nearest multiple of b that is towards zero
+    ToZero,
+}
+
+/// This determines the order in which we serialize members of a calc() sum.
+///
+/// See https://drafts.csswg.org/css-values-4/#sort-a-calculations-children
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
+#[allow(missing_docs)]
+pub enum SortKey {
+    Number,
+    Percentage,
+    Cap,
+    Ch,
+    Cqb,
+    Cqh,
+    Cqi,
+    Cqmax,
+    Cqmin,
+    Cqw,
+    Deg,
+    Dvb,
+    Dvh,
+    Dvi,
+    Dvmax,
+    Dvmin,
+    Dvw,
+    Em,
+    Ex,
+    Ic,
+    Lvb,
+    Lvh,
+    Lvi,
+    Lvmax,
+    Lvmin,
+    Lvw,
+    Px,
+    Rem,
+    Sec,
+    Svb,
+    Svh,
+    Svi,
+    Svmax,
+    Svmin,
+    Svw,
+    Vb,
+    Vh,
+    Vi,
+    Vmax,
+    Vmin,
+    Vw,
+    Other,
+}
+
+/// A generic node in a calc expression.
+///
+/// FIXME: This would be much more elegant if we used `Self` in the types below,
+/// but we can't because of https://github.com/serde-rs/serde/issues/1565.
+///
+/// FIXME: The following annotations are to workaround an LLVM inlining bug, see
+/// bug 1631929.
+///
+/// cbindgen:destructor-attributes=MOZ_NEVER_INLINE
+/// cbindgen:copy-constructor-attributes=MOZ_NEVER_INLINE
+/// cbindgen:eq-attributes=MOZ_NEVER_INLINE
+#[repr(u8)]
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    ToAnimatedZero,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum GenericCalcNode<L> {
+    /// A leaf node.
+    Leaf(L),
+    /// A sum node, representing `a + b + c` where a, b, and c are the
+    /// arguments.
+    Sum(crate::OwnedSlice<GenericCalcNode<L>>),
+    /// A `min` or `max` function.
+    MinMax(crate::OwnedSlice<GenericCalcNode<L>>, MinMaxOp),
+    /// A `clamp()` function.
+    Clamp {
+        /// The minimum value.
+        min: Box<GenericCalcNode<L>>,
+        /// The central value.
+        center: Box<GenericCalcNode<L>>,
+        /// The maximum value.
+        max: Box<GenericCalcNode<L>>,
+    },
+    /// A `round()` function.
+    Round {
+        /// The rounding strategy.
+        strategy: RoundingStrategy,
+        /// The value to round.
+        value: Box<GenericCalcNode<L>>,
+        /// The step value.
+        step: Box<GenericCalcNode<L>>,
+    },
+    /// A `mod()` or `rem()` function.
+    ModRem {
+        /// The dividend calculation.
+        dividend: Box<GenericCalcNode<L>>,
+        /// The divisor calculation.
+        divisor: Box<GenericCalcNode<L>>,
+        /// Is the function mod or rem?
+        op: ModRemOp,
+    },
+}
+
+pub use self::GenericCalcNode as CalcNode;
+
+/// A trait that represents all the stuff a valid leaf of a calc expression.
+pub trait CalcNodeLeaf: Clone + Sized + PartialOrd + PartialEq + ToCss {
+    /// Returns the unitless value of this leaf.
+    fn unitless_value(&self) -> f32;
+
+    /// Whether this value is known-negative.
+    fn is_negative(&self) -> bool {
+        self.unitless_value().is_sign_negative()
+    }
+
+    /// Whether this value is infinite.
+    fn is_infinite(&self) -> bool {
+        self.unitless_value().is_infinite()
+    }
+
+    /// Whether this value is zero.
+    fn is_zero(&self) -> bool {
+        self.unitless_value().is_zero()
+    }
+
+    /// Whether this value is NaN.
+    fn is_nan(&self) -> bool {
+        self.unitless_value().is_nan()
+    }
+
+    /// Tries to merge one sum to another, that is, perform `x` + `y`.
+    fn try_sum_in_place(&mut self, other: &Self) -> Result<(), ()>;
+
+    /// Tries a generic arithmetic operation.
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32;
+
+    /// Multiplies the leaf by a given scalar number.
+    fn mul_by(&mut self, scalar: f32);
+
+    /// Negates the leaf.
+    fn negate(&mut self) {
+        self.mul_by(-1.);
+    }
+
+    /// Canonicalizes the expression if necessary.
+    fn simplify(&mut self);
+
+    /// Returns the sort key for simplification.
+    fn sort_key(&self) -> SortKey;
+}
+
+impl<L: CalcNodeLeaf> CalcNode<L> {
+    /// Negates the node.
+    pub fn negate(&mut self) {
+        self.mul_by(-1.);
+    }
+
+    fn sort_key(&self) -> SortKey {
+        match *self {
+            Self::Leaf(ref l) => l.sort_key(),
+            _ => SortKey::Other,
+        }
+    }
+
+    /// Returns the leaf if we can (if simplification has allowed it).
+    pub fn as_leaf(&self) -> Option<&L> {
+        match *self {
+            Self::Leaf(ref l) => Some(l),
+            _ => None,
+        }
+    }
+
+    /// Tries to merge one sum to another, that is, perform `x` + `y`.
+    fn try_sum_in_place(&mut self, other: &Self) -> Result<(), ()> {
+        match (self, other) {
+            (&mut CalcNode::Leaf(ref mut one), &CalcNode::Leaf(ref other)) => {
+                one.try_sum_in_place(other)
+            },
+            _ => Err(()),
+        }
+    }
+
+    /// Tries to apply a generic arithmentic operator
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        match (self, other) {
+            (&CalcNode::Leaf(ref one), &CalcNode::Leaf(ref other)) => {
+                Ok(CalcNode::Leaf(one.try_op(other, op)?))
+            },
+            _ => Err(()),
+        }
+    }
+
+    /// Convert this `CalcNode` into a `CalcNode` with a different leaf kind.
+    pub fn map_leaves<O, F>(&self, mut map: F) -> CalcNode<O>
+    where
+        O: CalcNodeLeaf,
+        F: FnMut(&L) -> O,
+    {
+        self.map_leaves_internal(&mut map)
+    }
+
+    fn map_leaves_internal<O, F>(&self, map: &mut F) -> CalcNode<O>
+    where
+        O: CalcNodeLeaf,
+        F: FnMut(&L) -> O,
+    {
+        fn map_children<L, O, F>(
+            children: &[CalcNode<L>],
+            map: &mut F,
+        ) -> crate::OwnedSlice<CalcNode<O>>
+        where
+            L: CalcNodeLeaf,
+            O: CalcNodeLeaf,
+            F: FnMut(&L) -> O,
+        {
+            children
+                .iter()
+                .map(|c| c.map_leaves_internal(map))
+                .collect()
+        }
+
+        match *self {
+            Self::Leaf(ref l) => CalcNode::Leaf(map(l)),
+            Self::Sum(ref c) => CalcNode::Sum(map_children(c, map)),
+            Self::MinMax(ref c, op) => CalcNode::MinMax(map_children(c, map), op),
+            Self::Clamp {
+                ref min,
+                ref center,
+                ref max,
+            } => {
+                let min = Box::new(min.map_leaves_internal(map));
+                let center = Box::new(center.map_leaves_internal(map));
+                let max = Box::new(max.map_leaves_internal(map));
+                CalcNode::Clamp { min, center, max }
+            },
+            Self::Round {
+                strategy,
+                ref value,
+                ref step,
+            } => {
+                let value = Box::new(value.map_leaves_internal(map));
+                let step = Box::new(step.map_leaves_internal(map));
+                CalcNode::Round {
+                    strategy,
+                    value,
+                    step,
+                }
+            },
+            Self::ModRem {
+                ref dividend,
+                ref divisor,
+                op,
+            } => {
+                let dividend = Box::new(dividend.map_leaves_internal(map));
+                let divisor = Box::new(divisor.map_leaves_internal(map));
+                CalcNode::ModRem {
+                    dividend,
+                    divisor,
+                    op,
+                }
+            },
+        }
+    }
+
+    /// Resolves the expression returning a value of `O`, given a function to
+    /// turn a leaf into the relevant value.
+    pub fn resolve<O>(
+        &self,
+        mut leaf_to_output_fn: impl FnMut(&L) -> Result<O, ()>,
+    ) -> Result<O, ()>
+    where
+        O: PartialOrd
+            + PartialEq
+            + Add<Output = O>
+            + Mul<Output = O>
+            + Div<Output = O>
+            + Sub<Output = O>
+            + Zero
+            + Float
+            + Copy,
+    {
+        self.resolve_internal(&mut leaf_to_output_fn)
+    }
+
+    fn resolve_internal<O, F>(&self, leaf_to_output_fn: &mut F) -> Result<O, ()>
+    where
+        O: PartialOrd
+            + PartialEq
+            + Add<Output = O>
+            + Mul<Output = O>
+            + Div<Output = O>
+            + Sub<Output = O>
+            + Zero
+            + Float
+            + Copy,
+        F: FnMut(&L) -> Result<O, ()>,
+    {
+        Ok(match *self {
+            Self::Leaf(ref l) => return leaf_to_output_fn(l),
+            Self::Sum(ref c) => {
+                let mut result = Zero::zero();
+                for child in &**c {
+                    result = result + child.resolve_internal(leaf_to_output_fn)?;
+                }
+                result
+            },
+            Self::MinMax(ref nodes, op) => {
+                let mut result = nodes[0].resolve_internal(leaf_to_output_fn)?;
+                for node in nodes.iter().skip(1) {
+                    let candidate = node.resolve_internal(leaf_to_output_fn)?;
+                    let candidate_wins = match op {
+                        MinMaxOp::Min => candidate < result,
+                        MinMaxOp::Max => candidate > result,
+                    };
+                    if candidate_wins {
+                        result = candidate;
+                    }
+                }
+                result
+            },
+            Self::Clamp {
+                ref min,
+                ref center,
+                ref max,
+            } => {
+                let min = min.resolve_internal(leaf_to_output_fn)?;
+                let center = center.resolve_internal(leaf_to_output_fn)?;
+                let max = max.resolve_internal(leaf_to_output_fn)?;
+
+                let mut result = center;
+                if result > max {
+                    result = max;
+                }
+                if result < min {
+                    result = min
+                }
+                result
+            },
+            Self::Round {
+                strategy,
+                ref value,
+                ref step,
+            } => {
+                let value = value.resolve_internal(leaf_to_output_fn)?;
+                let step = step.resolve_internal(leaf_to_output_fn)?;
+
+                // TODO(emilio): Seems like at least a few of these
+                // special-cases could be removed if we do the math in a
+                // particular order.
+                if step.is_zero() {
+                    return Ok(<O as Float>::nan());
+                }
+
+                if value.is_infinite() && step.is_infinite() {
+                    return Ok(<O as Float>::nan());
+                }
+
+                if value.is_infinite() {
+                    return Ok(value);
+                }
+
+                if step.is_infinite() {
+                    match strategy {
+                        RoundingStrategy::Nearest | RoundingStrategy::ToZero => {
+                            return if value.is_sign_negative() {
+                                Ok(<O as Float>::neg_zero())
+                            } else {
+                                Ok(<O as Zero>::zero())
+                            }
+                        },
+                        RoundingStrategy::Up => {
+                            return if !value.is_sign_negative() && !value.is_zero() {
+                                Ok(<O as Float>::infinity())
+                            } else if !value.is_sign_negative() && value.is_zero() {
+                                Ok(value)
+                            } else {
+                                Ok(<O as Float>::neg_zero())
+                            }
+                        },
+                        RoundingStrategy::Down => {
+                            return if value.is_sign_negative() && !value.is_zero() {
+                                Ok(<O as Float>::neg_infinity())
+                            } else if value.is_sign_negative() && value.is_zero() {
+                                Ok(value)
+                            } else {
+                                Ok(<O as Zero>::zero())
+                            }
+                        },
+                    }
+                }
+
+                let div = value / step;
+                let lower_bound = div.floor() * step;
+                let upper_bound = div.ceil() * step;
+
+                match strategy {
+                    RoundingStrategy::Nearest => {
+                        // In case of a tie, use the upper bound
+                        if value - lower_bound < upper_bound - value {
+                            lower_bound
+                        } else {
+                            upper_bound
+                        }
+                    },
+                    RoundingStrategy::Up => upper_bound,
+                    RoundingStrategy::Down => lower_bound,
+                    RoundingStrategy::ToZero => {
+                        // In case of a tie, use the upper bound
+                        if lower_bound.abs() < upper_bound.abs() {
+                            lower_bound
+                        } else {
+                            upper_bound
+                        }
+                    },
+                }
+            },
+            Self::ModRem {
+                ref dividend,
+                ref divisor,
+                op,
+            } => {
+                let dividend = dividend.resolve_internal(leaf_to_output_fn)?;
+                let divisor = divisor.resolve_internal(leaf_to_output_fn)?;
+
+                // In mod(A, B) only, if B is infinite and A has opposite sign to B
+                // (including an oppositely-signed zero), the result is NaN.
+                // https://drafts.csswg.org/css-values/#round-infinities
+                if matches!(op, ModRemOp::Mod) &&
+                    divisor.is_infinite() &&
+                    dividend.is_sign_negative() != divisor.is_sign_negative()
+                {
+                    return Ok(<O as Float>::nan());
+                }
+
+                match op {
+                    ModRemOp::Mod => dividend - divisor * (dividend / divisor).floor(),
+                    ModRemOp::Rem => dividend - divisor * (dividend / divisor).trunc(),
+                }
+            },
+        })
+    }
+
+    fn is_negative_leaf(&self) -> bool {
+        match *self {
+            Self::Leaf(ref l) => l.is_negative(),
+            _ => false,
+        }
+    }
+
+    fn is_zero_leaf(&self) -> bool {
+        match *self {
+            Self::Leaf(ref l) => l.is_zero(),
+            _ => false,
+        }
+    }
+
+    fn is_infinite_leaf(&self) -> bool {
+        match *self {
+            Self::Leaf(ref l) => l.is_infinite(),
+            _ => false,
+        }
+    }
+
+    /// Multiplies the node by a scalar.
+    pub fn mul_by(&mut self, scalar: f32) {
+        match *self {
+            Self::Leaf(ref mut l) => l.mul_by(scalar),
+            // Multiplication is distributive across this.
+            Self::Sum(ref mut children) => {
+                for node in &mut **children {
+                    node.mul_by(scalar);
+                }
+            },
+            // This one is a bit trickier.
+            Self::MinMax(ref mut children, ref mut op) => {
+                for node in &mut **children {
+                    node.mul_by(scalar);
+                }
+
+                // For negatives we need to invert the operation.
+                if scalar < 0. {
+                    *op = match *op {
+                        MinMaxOp::Min => MinMaxOp::Max,
+                        MinMaxOp::Max => MinMaxOp::Min,
+                    }
+                }
+            },
+            // This one is slightly tricky too.
+            Self::Clamp {
+                ref mut min,
+                ref mut center,
+                ref mut max,
+            } => {
+                min.mul_by(scalar);
+                center.mul_by(scalar);
+                max.mul_by(scalar);
+                // For negatives we need to swap min / max.
+                if scalar < 0. {
+                    mem::swap(min, max);
+                }
+            },
+            Self::Round {
+                ref mut value,
+                ref mut step,
+                ..
+            } => {
+                value.mul_by(scalar);
+                step.mul_by(scalar);
+            },
+            Self::ModRem {
+                ref mut dividend,
+                ref mut divisor,
+                ..
+            } => {
+                dividend.mul_by(scalar);
+                divisor.mul_by(scalar);
+            },
+        }
+    }
+
+    /// Visits all the nodes in this calculation tree recursively, starting by
+    /// the leaves and bubbling all the way up.
+    ///
+    /// This is useful for simplification, but can also be used for validation
+    /// and such.
+    pub fn visit_depth_first(&mut self, mut f: impl FnMut(&mut Self)) {
+        self.visit_depth_first_internal(&mut f);
+    }
+
+    fn visit_depth_first_internal(&mut self, f: &mut impl FnMut(&mut Self)) {
+        match *self {
+            Self::Clamp {
+                ref mut min,
+                ref mut center,
+                ref mut max,
+            } => {
+                min.visit_depth_first_internal(f);
+                center.visit_depth_first_internal(f);
+                max.visit_depth_first_internal(f);
+            },
+            Self::Round {
+                ref mut value,
+                ref mut step,
+                ..
+            } => {
+                value.visit_depth_first_internal(f);
+                step.visit_depth_first_internal(f);
+            },
+            Self::ModRem {
+                ref mut dividend,
+                ref mut divisor,
+                ..
+            } => {
+                dividend.visit_depth_first_internal(f);
+                divisor.visit_depth_first_internal(f);
+            },
+            Self::Sum(ref mut children) | Self::MinMax(ref mut children, _) => {
+                for child in &mut **children {
+                    child.visit_depth_first_internal(f);
+                }
+            },
+            Self::Leaf(..) => {},
+        }
+        f(self);
+    }
+
+    /// Simplifies and sorts the calculation of a given node. All the nodes
+    /// below it should be simplified already, this only takes care of
+    /// simplifying directly nested nodes. So, probably should always be used in
+    /// combination with `visit_depth_first()`.
+    ///
+    /// This is only needed if it's going to be preserved after parsing (so, for
+    /// `<length-percentage>`). Otherwise we can just evaluate it using
+    /// `resolve()`, and we'll come up with a simplified value anyways.
+    pub fn simplify_and_sort_direct_children(&mut self) {
+        macro_rules! replace_self_with {
+            ($slot:expr) => {{
+                let dummy = Self::MinMax(Default::default(), MinMaxOp::Max);
+                let result = mem::replace($slot, dummy);
+                *self = result;
+            }};
+        }
+        match *self {
+            Self::Clamp {
+                ref mut min,
+                ref mut center,
+                ref mut max,
+            } => {
+                // NOTE: clamp() is max(min, min(center, max))
+                let min_cmp_center = match min.partial_cmp(&center) {
+                    Some(o) => o,
+                    None => return,
+                };
+
+                // So if we can prove that min is more than center, then we won,
+                // as that's what we should always return.
+                if matches!(min_cmp_center, cmp::Ordering::Greater) {
+                    return replace_self_with!(&mut **min);
+                }
+
+                // Otherwise try with max.
+                let max_cmp_center = match max.partial_cmp(&center) {
+                    Some(o) => o,
+                    None => return,
+                };
+
+                if matches!(max_cmp_center, cmp::Ordering::Less) {
+                    // max is less than center, so we need to return effectively
+                    // `max(min, max)`.
+                    let max_cmp_min = match max.partial_cmp(&min) {
+                        Some(o) => o,
+                        None => {
+                            debug_assert!(
+                                false,
+                                "We compared center with min and max, how are \
+                                 min / max not comparable with each other?"
+                            );
+                            return;
+                        },
+                    };
+
+                    if matches!(max_cmp_min, cmp::Ordering::Less) {
+                        return replace_self_with!(&mut **min);
+                    }
+
+                    return replace_self_with!(&mut **max);
+                }
+
+                // Otherwise we're the center node.
+                return replace_self_with!(&mut **center);
+            },
+            Self::Round {
+                strategy,
+                ref mut value,
+                ref mut step,
+            } => {
+                if step.is_zero_leaf() {
+                    value.mul_by(f32::NAN);
+                    return replace_self_with!(&mut **value);
+                }
+
+                if value.is_infinite_leaf() && step.is_infinite_leaf() {
+                    value.mul_by(f32::NAN);
+                    return replace_self_with!(&mut **value);
+                }
+
+                if value.is_infinite_leaf() {
+                    return replace_self_with!(&mut **value);
+                }
+
+                if step.is_infinite_leaf() {
+                    match strategy {
+                        RoundingStrategy::Nearest | RoundingStrategy::ToZero => {
+                            value.mul_by(0.);
+                            return replace_self_with!(&mut **value);
+                        },
+                        RoundingStrategy::Up => {
+                            if !value.is_negative_leaf() && !value.is_zero_leaf() {
+                                value.mul_by(f32::INFINITY);
+                                return replace_self_with!(&mut **value);
+                            } else if !value.is_negative_leaf() && value.is_zero_leaf() {
+                                return replace_self_with!(&mut **value);
+                            } else {
+                                value.mul_by(0.);
+                                return replace_self_with!(&mut **value);
+                            }
+                        },
+                        RoundingStrategy::Down => {
+                            if value.is_negative_leaf() && !value.is_zero_leaf() {
+                                value.mul_by(f32::INFINITY);
+                                return replace_self_with!(&mut **value);
+                            } else if value.is_negative_leaf() && value.is_zero_leaf() {
+                                return replace_self_with!(&mut **value);
+                            } else {
+                                value.mul_by(0.);
+                                return replace_self_with!(&mut **value);
+                            }
+                        },
+                    }
+                }
+
+                if step.is_negative_leaf() {
+                    step.negate();
+                }
+
+                let remainder = match value.try_op(step, Rem::rem) {
+                    Ok(res) => res,
+                    Err(..) => return,
+                };
+
+                let (mut lower_bound, mut upper_bound) = if value.is_negative_leaf() {
+                    let upper_bound = match value.try_op(&remainder, Sub::sub) {
+                        Ok(res) => res,
+                        Err(..) => return,
+                    };
+
+                    let lower_bound = match upper_bound.try_op(&step, Sub::sub) {
+                        Ok(res) => res,
+                        Err(..) => return,
+                    };
+
+                    (lower_bound, upper_bound)
+                } else {
+                    let lower_bound = match value.try_op(&remainder, Sub::sub) {
+                        Ok(res) => res,
+                        Err(..) => return,
+                    };
+
+                    let upper_bound = match lower_bound.try_op(&step, Add::add) {
+                        Ok(res) => res,
+                        Err(..) => return,
+                    };
+
+                    (lower_bound, upper_bound)
+                };
+
+                match strategy {
+                    RoundingStrategy::Nearest => {
+                        let lower_diff = match value.try_op(&lower_bound, Sub::sub) {
+                            Ok(res) => res,
+                            Err(..) => return,
+                        };
+
+                        let upper_diff = match upper_bound.try_op(value, Sub::sub) {
+                            Ok(res) => res,
+                            Err(..) => return,
+                        };
+
+                        // In case of a tie, use the upper bound
+                        if lower_diff < upper_diff {
+                            return replace_self_with!(&mut lower_bound);
+                        } else {
+                            return replace_self_with!(&mut upper_bound);
+                        }
+                    },
+                    RoundingStrategy::Up => return replace_self_with!(&mut upper_bound),
+                    RoundingStrategy::Down => return replace_self_with!(&mut lower_bound),
+                    RoundingStrategy::ToZero => {
+                        let mut lower_diff = lower_bound.clone();
+                        let mut upper_diff = upper_bound.clone();
+
+                        if lower_diff.is_negative_leaf() {
+                            lower_diff.negate();
+                        }
+
+                        if upper_diff.is_negative_leaf() {
+                            upper_diff.negate();
+                        }
+
+                        // In case of a tie, use the upper bound
+                        if lower_diff < upper_diff {
+                            return replace_self_with!(&mut lower_bound);
+                        } else {
+                            return replace_self_with!(&mut upper_bound);
+                        }
+                    },
+                };
+            },
+            Self::ModRem {
+                ref dividend,
+                ref divisor,
+                op,
+            } => {
+                let mut result = dividend.clone();
+
+                // In mod(A, B) only, if B is infinite and A has opposite sign to B
+                // (including an oppositely-signed zero), the result is NaN.
+                // https://drafts.csswg.org/css-values/#round-infinities
+                if matches!(op, ModRemOp::Mod) &&
+                    divisor.is_infinite_leaf() &&
+                    dividend.is_negative_leaf() != divisor.is_negative_leaf()
+                {
+                    result.mul_by(f32::NAN);
+                    return replace_self_with!(&mut *result);
+                }
+
+                let result = match op {
+                    ModRemOp::Mod => dividend.try_op(divisor, |a, b| a - b * (a / b).floor()),
+                    ModRemOp::Rem => dividend.try_op(divisor, |a, b| a - b * (a / b).trunc()),
+                };
+
+                let mut result = match result {
+                    Ok(res) => res,
+                    Err(..) => return,
+                };
+
+                return replace_self_with!(&mut result);
+            },
+            Self::MinMax(ref mut children, op) => {
+                let winning_order = match op {
+                    MinMaxOp::Min => cmp::Ordering::Less,
+                    MinMaxOp::Max => cmp::Ordering::Greater,
+                };
+
+                let mut result = 0;
+                for i in 1..children.len() {
+                    let o = match children[i].partial_cmp(&children[result]) {
+                        // We can't compare all the children, so we can't
+                        // know which one will actually win. Bail out and
+                        // keep ourselves as a min / max function.
+                        //
+                        // TODO: Maybe we could simplify compatible children,
+                        // see https://github.com/w3c/csswg-drafts/issues/4756
+                        None => return,
+                        Some(o) => o,
+                    };
+
+                    if o == winning_order {
+                        result = i;
+                    }
+                }
+
+                replace_self_with!(&mut children[result]);
+            },
+            Self::Sum(ref mut children_slot) => {
+                let mut sums_to_merge = SmallVec::<[_; 3]>::new();
+                let mut extra_kids = 0;
+                for (i, child) in children_slot.iter().enumerate() {
+                    if let Self::Sum(ref children) = *child {
+                        extra_kids += children.len();
+                        sums_to_merge.push(i);
+                    }
+                }
+
+                // If we only have one kid, we've already simplified it, and it
+                // doesn't really matter whether it's a sum already or not, so
+                // lift it up and continue.
+                if children_slot.len() == 1 {
+                    return replace_self_with!(&mut children_slot[0]);
+                }
+
+                let mut children = mem::replace(children_slot, Default::default()).into_vec();
+
+                if !sums_to_merge.is_empty() {
+                    children.reserve(extra_kids - sums_to_merge.len());
+                    // Merge all our nested sums, in reverse order so that the
+                    // list indices are not invalidated.
+                    for i in sums_to_merge.drain(..).rev() {
+                        let kid_children = match children.swap_remove(i) {
+                            Self::Sum(c) => c,
+                            _ => unreachable!(),
+                        };
+
+                        // This would be nicer with
+                        // https://github.com/rust-lang/rust/issues/59878 fixed.
+                        children.extend(kid_children.into_vec());
+                    }
+                }
+
+                debug_assert!(children.len() >= 2, "Should still have multiple kids!");
+
+                // Sort by spec order.
+                children.sort_unstable_by_key(|c| c.sort_key());
+
+                // NOTE: if the function returns true, by the docs of dedup_by,
+                // a is removed.
+                children.dedup_by(|a, b| b.try_sum_in_place(a).is_ok());
+
+                if children.len() == 1 {
+                    // If only one children remains, lift it up, and carry on.
+                    replace_self_with!(&mut children[0]);
+                } else {
+                    // Else put our simplified children back.
+                    *children_slot = children.into_boxed_slice().into();
+                }
+            },
+            Self::Leaf(ref mut l) => {
+                l.simplify();
+            },
+        }
+    }
+
+    /// Simplifies and sorts the kids in the whole calculation subtree.
+    pub fn simplify_and_sort(&mut self) {
+        self.visit_depth_first(|node| node.simplify_and_sort_direct_children())
+    }
+
+    fn to_css_impl<W>(&self, dest: &mut CssWriter<W>, is_outermost: bool) -> fmt::Result
+    where
+        W: Write,
+    {
+        let write_closing_paren = match *self {
+            Self::MinMax(_, op) => {
+                dest.write_str(match op {
+                    MinMaxOp::Max => "max(",
+                    MinMaxOp::Min => "min(",
+                })?;
+                true
+            },
+            Self::Clamp { .. } => {
+                dest.write_str("clamp(")?;
+                true
+            },
+            Self::Round { strategy, .. } => {
+                match strategy {
+                    RoundingStrategy::Nearest => dest.write_str("round("),
+                    RoundingStrategy::Up => dest.write_str("round(up, "),
+                    RoundingStrategy::Down => dest.write_str("round(down, "),
+                    RoundingStrategy::ToZero => dest.write_str("round(to-zero, "),
+                }?;
+
+                true
+            },
+            Self::ModRem { op, .. } => {
+                dest.write_str(match op {
+                    ModRemOp::Mod => "mod(",
+                    ModRemOp::Rem => "rem(",
+                })?;
+
+                true
+            },
+            _ => {
+                if is_outermost {
+                    dest.write_str("calc(")?;
+                }
+                is_outermost
+            },
+        };
+
+        match *self {
+            Self::MinMax(ref children, _) => {
+                let mut first = true;
+                for child in &**children {
+                    if !first {
+                        dest.write_str(", ")?;
+                    }
+                    first = false;
+                    child.to_css_impl(dest, false)?;
+                }
+            },
+            Self::Sum(ref children) => {
+                let mut first = true;
+                for child in &**children {
+                    if !first {
+                        if child.is_negative_leaf() {
+                            dest.write_str(" - ")?;
+                            let mut c = child.clone();
+                            c.negate();
+                            c.to_css_impl(dest, false)?;
+                        } else {
+                            dest.write_str(" + ")?;
+                            child.to_css_impl(dest, false)?;
+                        }
+                    } else {
+                        first = false;
+                        child.to_css_impl(dest, false)?;
+                    }
+                }
+            },
+            Self::Clamp {
+                ref min,
+                ref center,
+                ref max,
+            } => {
+                min.to_css_impl(dest, false)?;
+                dest.write_str(", ")?;
+                center.to_css_impl(dest, false)?;
+                dest.write_str(", ")?;
+                max.to_css_impl(dest, false)?;
+            },
+            Self::Round {
+                ref value,
+                ref step,
+                ..
+            } => {
+                value.to_css_impl(dest, false)?;
+                dest.write_str(", ")?;
+                step.to_css_impl(dest, false)?;
+            },
+            Self::ModRem {
+                ref dividend,
+                ref divisor,
+                ..
+            } => {
+                dividend.to_css_impl(dest, false)?;
+                dest.write_str(", ")?;
+                divisor.to_css_impl(dest, false)?;
+            },
+            Self::Leaf(ref l) => l.to_css(dest)?,
+        }
+
+        if write_closing_paren {
+            dest.write_str(")")?;
+        }
+        Ok(())
+    }
+}
+
+impl<L: CalcNodeLeaf> PartialOrd for CalcNode<L> {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        match (self, other) {
+            (&CalcNode::Leaf(ref one), &CalcNode::Leaf(ref other)) => one.partial_cmp(other),
+            _ => None,
+        }
+    }
+}
+
+impl<L: CalcNodeLeaf> ToCss for CalcNode<L> {
+    /// <https://drafts.csswg.org/css-values/#calc-serialize>
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.to_css_impl(dest, /* is_outermost = */ true)
+    }
+}
diff --git a/servo/components/style/values/generics/color.rs b/servo/components/style/values/generics/color.rs
new file mode 100644
index 0000000000..6c82cbf2ae
--- /dev/null
+++ b/servo/components/style/values/generics/color.rs
@@ -0,0 +1,379 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for color properties.
+
+use crate::values::animated::color::AnimatedRGBA;
+use crate::values::animated::ToAnimatedValue;
+use crate::values::specified::percentage::ToPercentage;
+use crate::values::{Parse, Parser, ParserContext};
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ParseError, ToCss};
+
+/// This struct represents a combined color from a numeric color and
+/// the current foreground color (currentcolor keyword).
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToAnimatedValue, ToShmem)]
+#[repr(C)]
+pub enum GenericColor<RGBA, Percentage> {
+    /// The actual numeric color.
+    Numeric(RGBA),
+    /// The `CurrentColor` keyword.
+    CurrentColor,
+    /// The color-mix() function.
+    ColorMix(Box<GenericColorMix<Self, Percentage>>),
+}
+
+/// A color space as defined in [1].
+///
+/// [1]: https://drafts.csswg.org/css-color-4/#typedef-color-space
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ColorSpace {
+    /// The sRGB color space.
+    Srgb,
+    /// The linear-sRGB color space.
+    LinearSrgb,
+    /// The CIEXYZ color space.
+    #[parse(aliases = "xyz-d65")]
+    Xyz,
+    /// https://drafts.csswg.org/css-color-4/#valdef-color-xyz
+    XyzD50,
+    /// The CIELAB color space.
+    Lab,
+    /// https://drafts.csswg.org/css-color-4/#valdef-hsl-hsl
+    Hsl,
+    /// https://drafts.csswg.org/css-color-4/#valdef-hwb-hwb
+    Hwb,
+    /// The CIELAB color space, expressed in cylindrical coordinates.
+    Lch,
+    // TODO: Oklab, Lch
+}
+
+impl ColorSpace {
+    /// Returns whether this is a `<polar-color-space>`.
+    pub fn is_polar(self) -> bool {
+        match self {
+            Self::Srgb | Self::LinearSrgb | Self::Xyz | Self::XyzD50 | Self::Lab => false,
+            Self::Hsl | Self::Hwb | Self::Lch => true,
+        }
+    }
+}
+
+/// A hue-interpolation-method as defined in [1].
+///
+/// [1]: https://drafts.csswg.org/css-color-4/#typedef-hue-interpolation-method
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum HueInterpolationMethod {
+    /// https://drafts.csswg.org/css-color-4/#shorter
+    Shorter,
+    /// https://drafts.csswg.org/css-color-4/#longer
+    Longer,
+    /// https://drafts.csswg.org/css-color-4/#increasing
+    Increasing,
+    /// https://drafts.csswg.org/css-color-4/#decreasing
+    Decreasing,
+    /// https://drafts.csswg.org/css-color-4/#specified
+    Specified,
+}
+
+/// https://drafts.csswg.org/css-color-4/#color-interpolation-method
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToShmem,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+)]
+#[repr(C)]
+pub struct ColorInterpolationMethod {
+    /// The color-space the interpolation should be done in.
+    pub space: ColorSpace,
+    /// The hue interpolation method.
+    pub hue: HueInterpolationMethod,
+}
+
+impl ColorInterpolationMethod {
+    /// Returns the srgb interpolation method.
+    pub fn srgb() -> Self {
+        Self {
+            space: ColorSpace::Srgb,
+            hue: HueInterpolationMethod::Shorter,
+        }
+    }
+}
+
+impl Parse for ColorInterpolationMethod {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_ident_matching("in")?;
+        let space = ColorSpace::parse(input)?;
+        // https://drafts.csswg.org/css-color-4/#hue-interpolation
+        //     Unless otherwise specified, if no specific hue interpolation
+        //     algorithm is selected by the host syntax, the default is shorter.
+        let hue = if space.is_polar() {
+            input
+                .try_parse(|input| -> Result<_, ParseError<'i>> {
+                    let hue = HueInterpolationMethod::parse(input)?;
+                    input.expect_ident_matching("hue")?;
+                    Ok(hue)
+                })
+                .unwrap_or(HueInterpolationMethod::Shorter)
+        } else {
+            HueInterpolationMethod::Shorter
+        };
+        Ok(Self { space, hue })
+    }
+}
+
+impl ToCss for ColorInterpolationMethod {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("in ")?;
+        self.space.to_css(dest)?;
+        if self.hue != HueInterpolationMethod::Shorter {
+            dest.write_char(' ')?;
+            self.hue.to_css(dest)?;
+            dest.write_str(" hue")?;
+        }
+        Ok(())
+    }
+}
+
+/// A restricted version of the css `color-mix()` function, which only supports
+/// percentages.
+///
+/// https://drafts.csswg.org/css-color-5/#color-mix
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[repr(C)]
+pub struct GenericColorMix<Color, Percentage> {
+    pub interpolation: ColorInterpolationMethod,
+    pub left: Color,
+    pub left_percentage: Percentage,
+    pub right: Color,
+    pub right_percentage: Percentage,
+    pub normalize_weights: bool,
+}
+
+pub use self::GenericColorMix as ColorMix;
+
+impl<Color: ToCss, Percentage: ToCss + ToPercentage> ToCss for ColorMix<Color, Percentage> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        fn can_omit<Percentage: ToPercentage>(
+            percent: &Percentage,
+            other: &Percentage,
+            is_left: bool,
+        ) -> bool {
+            if percent.is_calc() {
+                return false;
+            }
+            if percent.to_percentage() == 0.5 {
+                return other.to_percentage() == 0.5;
+            }
+            if is_left {
+                return false;
+            }
+            (1.0 - percent.to_percentage() - other.to_percentage()).abs() <= f32::EPSILON
+        }
+
+        dest.write_str("color-mix(")?;
+        self.interpolation.to_css(dest)?;
+        dest.write_str(", ")?;
+        self.left.to_css(dest)?;
+        if !can_omit(&self.left_percentage, &self.right_percentage, true) {
+            dest.write_str(" ")?;
+            self.left_percentage.to_css(dest)?;
+        }
+        dest.write_str(", ")?;
+        self.right.to_css(dest)?;
+        if !can_omit(&self.right_percentage, &self.left_percentage, false) {
+            dest.write_str(" ")?;
+            self.right_percentage.to_css(dest)?;
+        }
+        dest.write_str(")")
+    }
+}
+
+impl<RGBA, Percentage> ColorMix<GenericColor<RGBA, Percentage>, Percentage> {
+    fn to_rgba(&self) -> Option<RGBA>
+    where
+        RGBA: Clone + ToAnimatedValue<AnimatedValue = AnimatedRGBA>,
+        Percentage: ToPercentage,
+    {
+        use crate::values::animated::color::Color as AnimatedColor;
+        let left = self.left.as_numeric()?.clone().to_animated_value();
+        let right = self.right.as_numeric()?.clone().to_animated_value();
+        Some(ToAnimatedValue::from_animated_value(AnimatedColor::mix(
+            &self.interpolation,
+            &left,
+            self.left_percentage.to_percentage(),
+            &right,
+            self.right_percentage.to_percentage(),
+            self.normalize_weights,
+        )))
+    }
+}
+
+pub use self::GenericColor as Color;
+
+impl<RGBA, Percentage> Color<RGBA, Percentage> {
+    /// Returns the numeric rgba value if this color is numeric, or None
+    /// otherwise.
+    pub fn as_numeric(&self) -> Option<&RGBA> {
+        match *self {
+            Self::Numeric(ref rgba) => Some(rgba),
+            _ => None,
+        }
+    }
+
+    /// Simplifies the color-mix()es to the extent possible given a current
+    /// color (or not).
+    pub fn simplify(&mut self, current_color: Option<&RGBA>)
+    where
+        RGBA: Clone + ToAnimatedValue<AnimatedValue = AnimatedRGBA>,
+        Percentage: ToPercentage,
+    {
+        match *self {
+            Self::Numeric(..) => {},
+            Self::CurrentColor => {
+                if let Some(c) = current_color {
+                    *self = Self::Numeric(c.clone());
+                }
+            },
+            Self::ColorMix(ref mut mix) => {
+                mix.left.simplify(current_color);
+                mix.right.simplify(current_color);
+
+                if let Some(mix) = mix.to_rgba() {
+                    *self = Self::Numeric(mix);
+                }
+            },
+        }
+    }
+
+    /// Returns a color value representing currentcolor.
+    pub fn currentcolor() -> Self {
+        Self::CurrentColor
+    }
+
+    /// Returns a numeric color representing the given RGBA value.
+    pub fn rgba(color: RGBA) -> Self {
+        Self::Numeric(color)
+    }
+
+    /// Whether it is a currentcolor value (no numeric color component).
+    pub fn is_currentcolor(&self) -> bool {
+        matches!(*self, Self::CurrentColor)
+    }
+
+    /// Whether it is a numeric color (no currentcolor component).
+    pub fn is_numeric(&self) -> bool {
+        matches!(*self, Self::Numeric(..))
+    }
+}
+
+/// Either `<color>` or `auto`.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToCss,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericColorOrAuto<C> {
+    /// A `<color>`.
+    Color(C),
+    /// `auto`
+    Auto,
+}
+
+pub use self::GenericColorOrAuto as ColorOrAuto;
+
+/// Caret color is effectively a ColorOrAuto, but resolves `auto` to
+/// currentColor.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct GenericCaretColor<C>(pub GenericColorOrAuto<C>);
+
+impl<C> GenericCaretColor<C> {
+    /// Returns the `auto` value.
+    pub fn auto() -> Self {
+        GenericCaretColor(GenericColorOrAuto::Auto)
+    }
+}
+
+pub use self::GenericCaretColor as CaretColor;
diff --git a/servo/components/style/values/generics/column.rs b/servo/components/style/values/generics/column.rs
new file mode 100644
index 0000000000..4b5f0e0399
--- /dev/null
+++ b/servo/components/style/values/generics/column.rs
@@ -0,0 +1,45 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for the column properties.
+
+/// A generic type for `column-count` values.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum ColumnCount<PositiveInteger> {
+    /// A positive integer.
+    Integer(PositiveInteger),
+    /// The keyword `auto`.
+    #[animation(error)]
+    Auto,
+}
+
+impl<I> ColumnCount<I> {
+    /// Returns `auto`.
+    #[inline]
+    pub fn auto() -> Self {
+        ColumnCount::Auto
+    }
+
+    /// Returns whether this value is `auto`.
+    #[inline]
+    pub fn is_auto(self) -> bool {
+        matches!(self, ColumnCount::Auto)
+    }
+}
diff --git a/servo/components/style/values/generics/counters.rs b/servo/components/style/values/generics/counters.rs
new file mode 100644
index 0000000000..903a5c870e
--- /dev/null
+++ b/servo/components/style/values/generics/counters.rs
@@ -0,0 +1,286 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for counters-related CSS values.
+
+#[cfg(feature = "servo-layout-2013")]
+use crate::computed_values::list_style_type::T as ListStyleType;
+#[cfg(feature = "gecko")]
+use crate::values::generics::CounterStyle;
+#[cfg(any(feature = "gecko", feature = "servo-layout-2020"))]
+use crate::values::specified::Attr;
+use crate::values::CustomIdent;
+use std::fmt::{self, Write};
+use std::ops::Deref;
+use style_traits::{CssWriter, ToCss};
+
+/// A name / value pair for counters.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericCounterPair<Integer> {
+    /// The name of the counter.
+    pub name: CustomIdent,
+    /// The value of the counter / increment / etc.
+    pub value: Integer,
+    /// If true, then this represents `reversed(name)`.
+    /// NOTE: It can only be true on `counter-reset` values.
+    pub is_reversed: bool,
+}
+pub use self::GenericCounterPair as CounterPair;
+
+impl<Integer> ToCss for CounterPair<Integer>
+where
+    Integer: ToCss + PartialEq<i32>,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.is_reversed {
+            dest.write_str("reversed(")?;
+        }
+        self.name.to_css(dest)?;
+        if self.is_reversed {
+            dest.write_str(")")?;
+            if self.value == i32::min_value() {
+                return Ok(());
+            }
+        }
+        dest.write_str(" ")?;
+        self.value.to_css(dest)
+    }
+}
+
+/// A generic value for the `counter-increment` property.
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct GenericCounterIncrement<I>(#[css(field_bound)] pub GenericCounters<I>);
+pub use self::GenericCounterIncrement as CounterIncrement;
+
+impl<I> CounterIncrement<I> {
+    /// Returns a new value for `counter-increment`.
+    #[inline]
+    pub fn new(counters: Vec<CounterPair<I>>) -> Self {
+        CounterIncrement(Counters(counters.into()))
+    }
+}
+
+impl<I> Deref for CounterIncrement<I> {
+    type Target = [CounterPair<I>];
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &(self.0).0
+    }
+}
+
+/// A generic value for the `counter-set` property.
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct GenericCounterSet<I>(#[css(field_bound)] pub GenericCounters<I>);
+pub use self::GenericCounterSet as CounterSet;
+
+impl<I> CounterSet<I> {
+    /// Returns a new value for `counter-set`.
+    #[inline]
+    pub fn new(counters: Vec<CounterPair<I>>) -> Self {
+        CounterSet(Counters(counters.into()))
+    }
+}
+
+impl<I> Deref for CounterSet<I> {
+    type Target = [CounterPair<I>];
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &(self.0).0
+    }
+}
+
+/// A generic value for the `counter-reset` property.
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct GenericCounterReset<I>(#[css(field_bound)] pub GenericCounters<I>);
+pub use self::GenericCounterReset as CounterReset;
+
+impl<I> CounterReset<I> {
+    /// Returns a new value for `counter-reset`.
+    #[inline]
+    pub fn new(counters: Vec<CounterPair<I>>) -> Self {
+        CounterReset(Counters(counters.into()))
+    }
+}
+
+impl<I> Deref for CounterReset<I> {
+    type Target = [CounterPair<I>];
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &(self.0).0
+    }
+}
+
+/// A generic value for lists of counters.
+///
+/// Keyword `none` is represented by an empty vector.
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct GenericCounters<I>(
+    #[css(field_bound)]
+    #[css(iterable, if_empty = "none")]
+    crate::OwnedSlice<GenericCounterPair<I>>,
+);
+pub use self::GenericCounters as Counters;
+
+#[cfg(feature = "servo-layout-2013")]
+type CounterStyleType = ListStyleType;
+
+#[cfg(feature = "gecko")]
+type CounterStyleType = CounterStyle;
+
+#[cfg(feature = "servo-layout-2013")]
+#[inline]
+fn is_decimal(counter_type: &CounterStyleType) -> bool {
+    *counter_type == ListStyleType::Decimal
+}
+
+#[cfg(feature = "gecko")]
+#[inline]
+fn is_decimal(counter_type: &CounterStyleType) -> bool {
+    *counter_type == CounterStyle::decimal()
+}
+
+/// The specified value for the `content` property.
+///
+/// https://drafts.csswg.org/css-content/#propdef-content
+#[derive(
+    Clone, Debug, Eq, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToComputedValue, ToCss, ToShmem,
+)]
+#[repr(u8)]
+pub enum GenericContent<Image> {
+    /// `normal` reserved keyword.
+    Normal,
+    /// `none` reserved keyword.
+    None,
+    /// Content items.
+    Items(#[css(iterable)] crate::OwnedSlice<GenericContentItem<Image>>),
+}
+
+pub use self::GenericContent as Content;
+
+impl<Image> Content<Image> {
+    /// Whether `self` represents list of items.
+    #[inline]
+    pub fn is_items(&self) -> bool {
+        matches!(*self, Self::Items(..))
+    }
+
+    /// Set `content` property to `normal`.
+    #[inline]
+    pub fn normal() -> Self {
+        Content::Normal
+    }
+}
+
+/// Items for the `content` property.
+#[derive(
+    Clone, Debug, Eq, MallocSizeOf, PartialEq, ToComputedValue, ToCss, ToResolvedValue, ToShmem,
+)]
+#[repr(u8)]
+pub enum GenericContentItem<I> {
+    /// Literal string content.
+    String(crate::OwnedStr),
+    /// `counter(name, style)`.
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+    #[css(comma, function)]
+    Counter(CustomIdent, #[css(skip_if = "is_decimal")] CounterStyleType),
+    /// `counters(name, separator, style)`.
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+    #[css(comma, function)]
+    Counters(
+        CustomIdent,
+        crate::OwnedStr,
+        #[css(skip_if = "is_decimal")] CounterStyleType,
+    ),
+    /// `open-quote`.
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+    OpenQuote,
+    /// `close-quote`.
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+    CloseQuote,
+    /// `no-open-quote`.
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+    NoOpenQuote,
+    /// `no-close-quote`.
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+    NoCloseQuote,
+    /// `-moz-alt-content`.
+    #[cfg(feature = "gecko")]
+    MozAltContent,
+    /// `-moz-label-content`.
+    /// This is needed to make `accesskey` work for XUL labels. It's basically
+    /// attr(value) otherwise.
+    #[cfg(feature = "gecko")]
+    MozLabelContent,
+    /// `attr([namespace? `|`]? ident)`
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2020"))]
+    Attr(Attr),
+    /// image-set(url) | url(url)
+    Image(I),
+}
+
+pub use self::GenericContentItem as ContentItem;
diff --git a/servo/components/style/values/generics/easing.rs b/servo/components/style/values/generics/easing.rs
new file mode 100644
index 0000000000..7e4e7a750b
--- /dev/null
+++ b/servo/components/style/values/generics/easing.rs
@@ -0,0 +1,138 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS Easing Functions.
+//! https://drafts.csswg.org/css-easing/#timing-functions
+
+use crate::parser::ParserContext;
+
+/// A generic easing function.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToShmem,
+    Serialize,
+    Deserialize,
+)]
+#[value_info(ty = "TIMING_FUNCTION")]
+#[repr(u8, C)]
+/// cbindgen:private-default-tagged-enum-constructor=false
+pub enum TimingFunction<Integer, Number, LinearStops> {
+    /// `linear | ease | ease-in | ease-out | ease-in-out`
+    Keyword(TimingKeyword),
+    /// `cubic-bezier(<number>, <number>, <number>, <number>)`
+    #[allow(missing_docs)]
+    #[css(comma, function)]
+    CubicBezier {
+        x1: Number,
+        y1: Number,
+        x2: Number,
+        y2: Number,
+    },
+    /// `step-start | step-end | steps(<integer>, [ <step-position> ]?)`
+    /// `<step-position> = jump-start | jump-end | jump-none | jump-both | start | end`
+    #[css(comma, function)]
+    #[value_info(other_values = "step-start,step-end")]
+    Steps(Integer, #[css(skip_if = "is_end")] StepPosition),
+    /// linear([<linear-stop>]#)
+    /// <linear-stop> = <output> && <linear-stop-length>?
+    /// <linear-stop-length> = <percentage>{1, 2}
+    #[css(function = "linear")]
+    LinearFunction(LinearStops),
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+    Serialize,
+    Deserialize,
+)]
+#[repr(u8)]
+pub enum TimingKeyword {
+    Linear,
+    Ease,
+    EaseIn,
+    EaseOut,
+    EaseInOut,
+}
+
+/// Before flag, defined as per https://drafts.csswg.org/css-easing/#before-flag
+/// This flag is never user-specified.
+#[allow(missing_docs)]
+#[derive(PartialEq)]
+#[repr(u8)]
+pub enum BeforeFlag {
+    Unset,
+    Set,
+}
+
+#[cfg(feature = "gecko")]
+fn step_position_jump_enabled(_context: &ParserContext) -> bool {
+    static_prefs::pref!("layout.css.step-position-jump.enabled")
+}
+
+#[cfg(feature = "servo")]
+fn step_position_jump_enabled(_context: &ParserContext) -> bool {
+    false
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+    Serialize,
+    Deserialize,
+)]
+#[repr(u8)]
+pub enum StepPosition {
+    #[parse(condition = "step_position_jump_enabled")]
+    JumpStart,
+    #[parse(condition = "step_position_jump_enabled")]
+    JumpEnd,
+    #[parse(condition = "step_position_jump_enabled")]
+    JumpNone,
+    #[parse(condition = "step_position_jump_enabled")]
+    JumpBoth,
+    Start,
+    End,
+}
+
+#[inline]
+fn is_end(position: &StepPosition) -> bool {
+    *position == StepPosition::JumpEnd || *position == StepPosition::End
+}
+
+impl<Integer, Number, LinearStops> TimingFunction<Integer, Number, LinearStops> {
+    /// `ease`
+    #[inline]
+    pub fn ease() -> Self {
+        TimingFunction::Keyword(TimingKeyword::Ease)
+    }
+}
diff --git a/servo/components/style/values/generics/effects.rs b/servo/components/style/values/generics/effects.rs
new file mode 100644
index 0000000000..f5666f3055
--- /dev/null
+++ b/servo/components/style/values/generics/effects.rs
@@ -0,0 +1,121 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to effects.
+
+/// A generic value for a single `box-shadow`.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericBoxShadow<Color, SizeLength, BlurShapeLength, ShapeLength> {
+    /// The base shadow.
+    pub base: GenericSimpleShadow<Color, SizeLength, BlurShapeLength>,
+    /// The spread radius.
+    pub spread: ShapeLength,
+    /// Whether this is an inset box shadow.
+    #[animation(constant)]
+    #[css(represents_keyword)]
+    pub inset: bool,
+}
+
+pub use self::GenericBoxShadow as BoxShadow;
+
+/// A generic value for a single `filter`.
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[animation(no_bound(U))]
+#[repr(C, u8)]
+pub enum GenericFilter<Angle, NonNegativeFactor, ZeroToOneFactor, Length, Shadow, U> {
+    /// `blur(<length>)`
+    #[css(function)]
+    Blur(Length),
+    /// `brightness(<factor>)`
+    #[css(function)]
+    Brightness(NonNegativeFactor),
+    /// `contrast(<factor>)`
+    #[css(function)]
+    Contrast(NonNegativeFactor),
+    /// `grayscale(<factor>)`
+    #[css(function)]
+    Grayscale(ZeroToOneFactor),
+    /// `hue-rotate(<angle>)`
+    #[css(function)]
+    HueRotate(Angle),
+    /// `invert(<factor>)`
+    #[css(function)]
+    Invert(ZeroToOneFactor),
+    /// `opacity(<factor>)`
+    #[css(function)]
+    Opacity(ZeroToOneFactor),
+    /// `saturate(<factor>)`
+    #[css(function)]
+    Saturate(NonNegativeFactor),
+    /// `sepia(<factor>)`
+    #[css(function)]
+    Sepia(ZeroToOneFactor),
+    /// `drop-shadow(...)`
+    #[css(function)]
+    DropShadow(Shadow),
+    /// `<url>`
+    #[animation(error)]
+    Url(U),
+}
+
+pub use self::GenericFilter as Filter;
+
+/// A generic value for the `drop-shadow()` filter and the `text-shadow` property.
+///
+/// Contrary to the canonical order from the spec, the color is serialised
+/// first, like in Gecko and Webkit.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericSimpleShadow<Color, SizeLength, ShapeLength> {
+    /// Color.
+    pub color: Color,
+    /// Horizontal radius.
+    pub horizontal: SizeLength,
+    /// Vertical radius.
+    pub vertical: SizeLength,
+    /// Blur radius.
+    pub blur: ShapeLength,
+}
+
+pub use self::GenericSimpleShadow as SimpleShadow;
diff --git a/servo/components/style/values/generics/flex.rs b/servo/components/style/values/generics/flex.rs
new file mode 100644
index 0000000000..85b64000f2
--- /dev/null
+++ b/servo/components/style/values/generics/flex.rs
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to flexbox.
+
+/// A generic value for the `flex-basis` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub enum GenericFlexBasis<S> {
+    /// `content`
+    Content,
+    /// `<width>`
+    Size(S),
+}
+
+pub use self::GenericFlexBasis as FlexBasis;
diff --git a/servo/components/style/values/generics/font.rs b/servo/components/style/values/generics/font.rs
new file mode 100644
index 0000000000..a88df7be17
--- /dev/null
+++ b/servo/components/style/values/generics/font.rs
@@ -0,0 +1,261 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for font stuff.
+
+use crate::parser::{Parse, ParserContext};
+use crate::One;
+use byteorder::{BigEndian, ReadBytesExt};
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use std::io::Cursor;
+use style_traits::{CssWriter, ParseError};
+use style_traits::{StyleParseErrorKind, ToCss};
+
+/// https://drafts.csswg.org/css-fonts-4/#feature-tag-value
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct FeatureTagValue<Integer> {
+    /// A four-character tag, packed into a u32 (one byte per character).
+    pub tag: FontTag,
+    /// The actual value.
+    pub value: Integer,
+}
+
+impl<Integer> ToCss for FeatureTagValue<Integer>
+where
+    Integer: One + ToCss + PartialEq,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.tag.to_css(dest)?;
+        // Don't serialize the default value.
+        if !self.value.is_one() {
+            dest.write_char(' ')?;
+            self.value.to_css(dest)?;
+        }
+
+        Ok(())
+    }
+}
+
+/// Variation setting for a single feature, see:
+///
+/// https://drafts.csswg.org/css-fonts-4/#font-variation-settings-def
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct VariationValue<Number> {
+    /// A four-character tag, packed into a u32 (one byte per character).
+    #[animation(constant)]
+    pub tag: FontTag,
+    /// The actual value.
+    pub value: Number,
+}
+
+/// A value both for font-variation-settings and font-feature-settings.
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma)]
+pub struct FontSettings<T>(#[css(if_empty = "normal", iterable)] pub Box<[T]>);
+
+impl<T> FontSettings<T> {
+    /// Default value of font settings as `normal`.
+    #[inline]
+    pub fn normal() -> Self {
+        FontSettings(vec![].into_boxed_slice())
+    }
+}
+
+impl<T: Parse> Parse for FontSettings<T> {
+    /// https://drafts.csswg.org/css-fonts-4/#descdef-font-face-font-feature-settings
+    /// https://drafts.csswg.org/css-fonts-4/#font-variation-settings-def
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|i| i.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(Self::normal());
+        }
+
+        Ok(FontSettings(
+            input
+                .parse_comma_separated(|i| T::parse(context, i))?
+                .into_boxed_slice(),
+        ))
+    }
+}
+
+/// A font four-character tag, represented as a u32 for convenience.
+///
+/// See:
+///   https://drafts.csswg.org/css-fonts-4/#font-variation-settings-def
+///   https://drafts.csswg.org/css-fonts-4/#descdef-font-face-font-feature-settings
+///
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct FontTag(pub u32);
+
+impl ToCss for FontTag {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        use byteorder::ByteOrder;
+        use std::str;
+
+        let mut raw = [0u8; 4];
+        BigEndian::write_u32(&mut raw, self.0);
+        str::from_utf8(&raw).unwrap_or_default().to_css(dest)
+    }
+}
+
+impl Parse for FontTag {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let tag = input.expect_string()?;
+
+        // allowed strings of length 4 containing chars: <U+20, U+7E>
+        if tag.len() != 4 || tag.as_bytes().iter().any(|c| *c < b' ' || *c > b'~') {
+            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        let mut raw = Cursor::new(tag.as_bytes());
+        Ok(FontTag(raw.read_u32::<BigEndian>().unwrap()))
+    }
+}
+
+/// A generic value for the `font-style` property.
+///
+/// https://drafts.csswg.org/css-fonts-4/#font-style-prop
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum FontStyle<Angle> {
+    #[animation(error)]
+    Normal,
+    #[animation(error)]
+    Italic,
+    #[value_info(starts_with_keyword)]
+    Oblique(Angle),
+}
+
+/// A generic value for the `font-size-adjust` property.
+///
+/// https://www.w3.org/TR/css-fonts-4/#font-size-adjust-prop
+/// https://github.com/w3c/csswg-drafts/issues/6160
+/// https://github.com/w3c/csswg-drafts/issues/6288
+#[allow(missing_docs)]
+#[repr(u8)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum GenericFontSizeAdjust<Number> {
+    #[animation(error)]
+    None,
+    // 'ex-height' is the implied basis, so the keyword can be omitted
+    ExHeight(Number),
+    #[value_info(starts_with_keyword)]
+    CapHeight(Number),
+    #[value_info(starts_with_keyword)]
+    ChWidth(Number),
+    #[value_info(starts_with_keyword)]
+    IcWidth(Number),
+    #[value_info(starts_with_keyword)]
+    IcHeight(Number),
+}
+
+impl<Number: ToCss> ToCss for GenericFontSizeAdjust<Number> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let (prefix, value) = match self {
+            Self::None => return dest.write_str("none"),
+            Self::ExHeight(v) => ("", v),
+            Self::CapHeight(v) => ("cap-height ", v),
+            Self::ChWidth(v) => ("ch-width ", v),
+            Self::IcWidth(v) => ("ic-width ", v),
+            Self::IcHeight(v) => ("ic-height ", v),
+        };
+
+        dest.write_str(prefix)?;
+        value.to_css(dest)
+    }
+}
diff --git a/servo/components/style/values/generics/grid.rs b/servo/components/style/values/generics/grid.rs
new file mode 100644
index 0000000000..46b1a65ba3
--- /dev/null
+++ b/servo/components/style/values/generics/grid.rs
@@ -0,0 +1,830 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for the handling of
+//! [grids](https://drafts.csswg.org/css-grid/).
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::specified;
+use crate::values::specified::grid::parse_line_names;
+use crate::values::{CSSFloat, CustomIdent};
+use crate::{Atom, Zero};
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use std::{cmp, usize};
+use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+
+/// These are the limits that we choose to clamp grid line numbers to.
+/// http://drafts.csswg.org/css-grid/#overlarge-grids
+/// line_num is clamped to this range at parse time.
+pub const MIN_GRID_LINE: i32 = -10000;
+/// See above.
+pub const MAX_GRID_LINE: i32 = 10000;
+
+/// A `<grid-line>` type.
+///
+/// <https://drafts.csswg.org/css-grid/#typedef-grid-row-start-grid-line>
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericGridLine<Integer> {
+    /// A custom identifier for named lines, or the empty atom otherwise.
+    ///
+    /// <https://drafts.csswg.org/css-grid/#grid-placement-slot>
+    pub ident: Atom,
+    /// Denotes the nth grid line from grid item's placement.
+    ///
+    /// This is clamped by MIN_GRID_LINE and MAX_GRID_LINE.
+    ///
+    /// NOTE(emilio): If we ever allow animating these we need to either do
+    /// something more complicated for the clamping, or do this clamping at
+    /// used-value time.
+    pub line_num: Integer,
+    /// Flag to check whether it's a `span` keyword.
+    pub is_span: bool,
+}
+
+pub use self::GenericGridLine as GridLine;
+
+impl<Integer> GridLine<Integer>
+where
+    Integer: PartialEq + Zero,
+{
+    /// The `auto` value.
+    pub fn auto() -> Self {
+        Self {
+            is_span: false,
+            line_num: Zero::zero(),
+            ident: atom!(""),
+        }
+    }
+
+    /// Check whether this `<grid-line>` represents an `auto` value.
+    pub fn is_auto(&self) -> bool {
+        self.ident == atom!("") && self.line_num.is_zero() && !self.is_span
+    }
+
+    /// Check whether this `<grid-line>` represents a `<custom-ident>` value.
+    pub fn is_ident_only(&self) -> bool {
+        self.ident != atom!("") && self.line_num.is_zero() && !self.is_span
+    }
+
+    /// Check if `self` makes `other` omittable according to the rules at:
+    /// https://drafts.csswg.org/css-grid/#propdef-grid-column
+    /// https://drafts.csswg.org/css-grid/#propdef-grid-area
+    pub fn can_omit(&self, other: &Self) -> bool {
+        if self.is_ident_only() {
+            self == other
+        } else {
+            other.is_auto()
+        }
+    }
+}
+
+impl<Integer> ToCss for GridLine<Integer>
+where
+    Integer: ToCss + PartialEq + Zero,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.is_auto() {
+            return dest.write_str("auto");
+        }
+
+        if self.is_span {
+            dest.write_str("span")?;
+        }
+
+        if !self.line_num.is_zero() {
+            if self.is_span {
+                dest.write_str(" ")?;
+            }
+            self.line_num.to_css(dest)?;
+        }
+
+        if self.ident != atom!("") {
+            if self.is_span || !self.line_num.is_zero() {
+                dest.write_str(" ")?;
+            }
+            CustomIdent(self.ident.clone()).to_css(dest)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Parse for GridLine<specified::Integer> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut grid_line = Self::auto();
+        if input.try_parse(|i| i.expect_ident_matching("auto")).is_ok() {
+            return Ok(grid_line);
+        }
+
+        // <custom-ident> | [ <integer> && <custom-ident>? ] | [ span && [ <integer> || <custom-ident> ] ]
+        // This <grid-line> horror is simply,
+        // [ span? && [ <custom-ident> || <integer> ] ]
+        // And, for some magical reason, "span" should be the first or last value and not in-between.
+        let mut val_before_span = false;
+
+        for _ in 0..3 {
+            // Maximum possible entities for <grid-line>
+            let location = input.current_source_location();
+            if input.try_parse(|i| i.expect_ident_matching("span")).is_ok() {
+                if grid_line.is_span {
+                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+
+                if !grid_line.line_num.is_zero() || grid_line.ident != atom!("") {
+                    val_before_span = true;
+                }
+
+                grid_line.is_span = true;
+            } else if let Ok(i) = input.try_parse(|i| specified::Integer::parse(context, i)) {
+                // FIXME(emilio): Probably shouldn't reject if it's calc()...
+                let value = i.value();
+                if value == 0 || val_before_span || !grid_line.line_num.is_zero() {
+                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+
+                grid_line.line_num = specified::Integer::new(cmp::max(
+                    MIN_GRID_LINE,
+                    cmp::min(value, MAX_GRID_LINE),
+                ));
+            } else if let Ok(name) = input.try_parse(|i| i.expect_ident_cloned()) {
+                if val_before_span || grid_line.ident != atom!("") {
+                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+                // NOTE(emilio): `span` is consumed above, so we only need to
+                // reject `auto`.
+                grid_line.ident = CustomIdent::from_ident(location, &name, &["auto"])?.0;
+            } else {
+                break;
+            }
+        }
+
+        if grid_line.is_auto() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        if grid_line.is_span {
+            if !grid_line.line_num.is_zero() {
+                if grid_line.line_num.value() <= 0 {
+                    // disallow negative integers for grid spans
+                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+            } else if grid_line.ident == atom!("") {
+                // integer could be omitted
+                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+        }
+
+        Ok(grid_line)
+    }
+}
+
+/// A track breadth for explicit grid track sizing. It's generic solely to
+/// avoid re-implementing it for the computed type.
+///
+/// <https://drafts.csswg.org/css-grid/#typedef-track-breadth>
+#[derive(
+    Animate,
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericTrackBreadth<L> {
+    /// The generic type is almost always a non-negative `<length-percentage>`
+    Breadth(L),
+    /// A flex fraction specified in `fr` units.
+    #[css(dimension)]
+    Fr(CSSFloat),
+    /// `auto`
+    Auto,
+    /// `min-content`
+    MinContent,
+    /// `max-content`
+    MaxContent,
+}
+
+pub use self::GenericTrackBreadth as TrackBreadth;
+
+impl<L> TrackBreadth<L> {
+    /// Check whether this is a `<fixed-breadth>` (i.e., it only has `<length-percentage>`)
+    ///
+    /// <https://drafts.csswg.org/css-grid/#typedef-fixed-breadth>
+    #[inline]
+    pub fn is_fixed(&self) -> bool {
+        matches!(*self, TrackBreadth::Breadth(..))
+    }
+}
+
+/// A `<track-size>` type for explicit grid track sizing. Like `<track-breadth>`, this is
+/// generic only to avoid code bloat. It only takes `<length-percentage>`
+///
+/// <https://drafts.csswg.org/css-grid/#typedef-track-size>
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericTrackSize<L> {
+    /// A flexible `<track-breadth>`
+    Breadth(GenericTrackBreadth<L>),
+    /// A `minmax` function for a range over an inflexible `<track-breadth>`
+    /// and a flexible `<track-breadth>`
+    ///
+    /// <https://drafts.csswg.org/css-grid/#valdef-grid-template-columns-minmax>
+    #[css(function)]
+    Minmax(GenericTrackBreadth<L>, GenericTrackBreadth<L>),
+    /// A `fit-content` function.
+    ///
+    /// This stores a TrackBreadth<L> for convenience, but it can only be a
+    /// LengthPercentage.
+    ///
+    /// <https://drafts.csswg.org/css-grid/#valdef-grid-template-columns-fit-content>
+    #[css(function)]
+    FitContent(GenericTrackBreadth<L>),
+}
+
+pub use self::GenericTrackSize as TrackSize;
+
+impl<L> TrackSize<L> {
+    /// The initial value.
+    const INITIAL_VALUE: Self = TrackSize::Breadth(TrackBreadth::Auto);
+
+    /// Returns the initial value.
+    pub const fn initial_value() -> Self {
+        Self::INITIAL_VALUE
+    }
+
+    /// Returns true if `self` is the initial value.
+    pub fn is_initial(&self) -> bool {
+        matches!(*self, TrackSize::Breadth(TrackBreadth::Auto)) // FIXME: can't use Self::INITIAL_VALUE here yet: https://github.com/rust-lang/rust/issues/66585
+    }
+
+    /// Check whether this is a `<fixed-size>`
+    ///
+    /// <https://drafts.csswg.org/css-grid/#typedef-fixed-size>
+    pub fn is_fixed(&self) -> bool {
+        match *self {
+            TrackSize::Breadth(ref breadth) => breadth.is_fixed(),
+            // For minmax function, it could be either
+            // minmax(<fixed-breadth>, <track-breadth>) or minmax(<inflexible-breadth>, <fixed-breadth>),
+            // and since both variants are a subset of minmax(<inflexible-breadth>, <track-breadth>), we only
+            // need to make sure that they're fixed. So, we don't have to modify the parsing function.
+            TrackSize::Minmax(ref breadth_1, ref breadth_2) => {
+                if breadth_1.is_fixed() {
+                    return true; // the second value is always a <track-breadth>
+                }
+
+                match *breadth_1 {
+                    TrackBreadth::Fr(_) => false, // should be <inflexible-breadth> at this point
+                    _ => breadth_2.is_fixed(),
+                }
+            },
+            TrackSize::FitContent(_) => false,
+        }
+    }
+}
+
+impl<L> Default for TrackSize<L> {
+    fn default() -> Self {
+        Self::initial_value()
+    }
+}
+
+impl<L: ToCss> ToCss for TrackSize<L> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            TrackSize::Breadth(ref breadth) => breadth.to_css(dest),
+            TrackSize::Minmax(ref min, ref max) => {
+                // According to gecko minmax(auto, <flex>) is equivalent to <flex>,
+                // and both are serialized as <flex>.
+                if let TrackBreadth::Auto = *min {
+                    if let TrackBreadth::Fr(_) = *max {
+                        return max.to_css(dest);
+                    }
+                }
+
+                dest.write_str("minmax(")?;
+                min.to_css(dest)?;
+                dest.write_str(", ")?;
+                max.to_css(dest)?;
+                dest.write_str(")")
+            },
+            TrackSize::FitContent(ref lp) => {
+                dest.write_str("fit-content(")?;
+                lp.to_css(dest)?;
+                dest.write_str(")")
+            },
+        }
+    }
+}
+
+/// A `<track-size>+`.
+/// We use the empty slice as `auto`, and always parse `auto` as an empty slice.
+/// This means it's impossible to have a slice containing only one auto item.
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct GenericImplicitGridTracks<T>(
+    #[css(if_empty = "auto", iterable)] pub crate::OwnedSlice<T>,
+);
+
+pub use self::GenericImplicitGridTracks as ImplicitGridTracks;
+
+impl<T: fmt::Debug + Default + PartialEq> ImplicitGridTracks<T> {
+    /// Returns true if current value is same as its initial value (i.e. auto).
+    pub fn is_initial(&self) -> bool {
+        debug_assert_ne!(
+            *self,
+            ImplicitGridTracks(crate::OwnedSlice::from(vec![Default::default()]))
+        );
+        self.0.is_empty()
+    }
+}
+
+/// Helper function for serializing identifiers with a prefix and suffix, used
+/// for serializing <line-names> (in grid).
+pub fn concat_serialize_idents<W>(
+    prefix: &str,
+    suffix: &str,
+    slice: &[CustomIdent],
+    sep: &str,
+    dest: &mut CssWriter<W>,
+) -> fmt::Result
+where
+    W: Write,
+{
+    if let Some((ref first, rest)) = slice.split_first() {
+        dest.write_str(prefix)?;
+        first.to_css(dest)?;
+        for thing in rest {
+            dest.write_str(sep)?;
+            thing.to_css(dest)?;
+        }
+
+        dest.write_str(suffix)?;
+    }
+
+    Ok(())
+}
+
+/// The initial argument of the `repeat` function.
+///
+/// <https://drafts.csswg.org/css-grid/#typedef-track-repeat>
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToCss, ToResolvedValue, ToShmem,
+)]
+#[repr(C, u8)]
+pub enum RepeatCount<Integer> {
+    /// A positive integer. This is allowed only for `<track-repeat>` and `<fixed-repeat>`
+    Number(Integer),
+    /// An `<auto-fill>` keyword allowed only for `<auto-repeat>`
+    AutoFill,
+    /// An `<auto-fit>` keyword allowed only for `<auto-repeat>`
+    AutoFit,
+}
+
+impl Parse for RepeatCount<specified::Integer> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(mut i) = input.try_parse(|i| specified::Integer::parse_positive(context, i)) {
+            if i.value() > MAX_GRID_LINE {
+                i = specified::Integer::new(MAX_GRID_LINE);
+            }
+            return Ok(RepeatCount::Number(i));
+        }
+        try_match_ident_ignore_ascii_case! { input,
+            "auto-fill" => Ok(RepeatCount::AutoFill),
+            "auto-fit" => Ok(RepeatCount::AutoFit),
+        }
+    }
+}
+
+/// The structure containing `<line-names>` and `<track-size>` values.
+///
+/// It can also hold `repeat()` function parameters, which expands into the respective
+/// values in its computed form.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function = "repeat")]
+#[repr(C)]
+pub struct GenericTrackRepeat<L, I> {
+    /// The number of times for the value to be repeated (could also be `auto-fit` or `auto-fill`)
+    pub count: RepeatCount<I>,
+    /// `<line-names>` accompanying `<track_size>` values.
+    ///
+    /// If there's no `<line-names>`, then it's represented by an empty vector.
+    /// For N `<track-size>` values, there will be N+1 `<line-names>`, and so this vector's
+    /// length is always one value more than that of the `<track-size>`.
+    pub line_names: crate::OwnedSlice<crate::OwnedSlice<CustomIdent>>,
+    /// `<track-size>` values.
+    pub track_sizes: crate::OwnedSlice<GenericTrackSize<L>>,
+}
+
+pub use self::GenericTrackRepeat as TrackRepeat;
+
+impl<L: ToCss, I: ToCss> ToCss for TrackRepeat<L, I> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("repeat(")?;
+        self.count.to_css(dest)?;
+        dest.write_str(", ")?;
+
+        let mut line_names_iter = self.line_names.iter();
+        for (i, (ref size, ref names)) in self
+            .track_sizes
+            .iter()
+            .zip(&mut line_names_iter)
+            .enumerate()
+        {
+            if i > 0 {
+                dest.write_str(" ")?;
+            }
+
+            concat_serialize_idents("[", "] ", names, " ", dest)?;
+            size.to_css(dest)?;
+        }
+
+        if let Some(line_names_last) = line_names_iter.next() {
+            concat_serialize_idents(" [", "]", line_names_last, " ", dest)?;
+        }
+
+        dest.write_str(")")?;
+
+        Ok(())
+    }
+}
+
+/// Track list values. Can be <track-size> or <track-repeat>
+#[derive(
+    Animate,
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericTrackListValue<LengthPercentage, Integer> {
+    /// A <track-size> value.
+    TrackSize(#[animation(field_bound)] GenericTrackSize<LengthPercentage>),
+    /// A <track-repeat> value.
+    TrackRepeat(#[animation(field_bound)] GenericTrackRepeat<LengthPercentage, Integer>),
+}
+
+pub use self::GenericTrackListValue as TrackListValue;
+
+impl<L, I> TrackListValue<L, I> {
+    // FIXME: can't use TrackSize::initial_value() here b/c rustc error "is not yet stable as a const fn"
+    const INITIAL_VALUE: Self = TrackListValue::TrackSize(TrackSize::Breadth(TrackBreadth::Auto));
+
+    fn is_repeat(&self) -> bool {
+        matches!(*self, TrackListValue::TrackRepeat(..))
+    }
+
+    /// Returns true if `self` is the initial value.
+    pub fn is_initial(&self) -> bool {
+        matches!(
+            *self,
+            TrackListValue::TrackSize(TrackSize::Breadth(TrackBreadth::Auto))
+        ) // FIXME: can't use Self::INITIAL_VALUE here yet: https://github.com/rust-lang/rust/issues/66585
+    }
+}
+
+impl<L, I> Default for TrackListValue<L, I> {
+    #[inline]
+    fn default() -> Self {
+        Self::INITIAL_VALUE
+    }
+}
+
+/// A grid `<track-list>` type.
+///
+/// <https://drafts.csswg.org/css-grid/#typedef-track-list>
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericTrackList<LengthPercentage, Integer> {
+    /// The index in `values` where our `<auto-repeat>` value is, if in bounds.
+    #[css(skip)]
+    pub auto_repeat_index: usize,
+    /// A vector of `<track-size> | <track-repeat>` values.
+    pub values: crate::OwnedSlice<GenericTrackListValue<LengthPercentage, Integer>>,
+    /// `<line-names>` accompanying `<track-size> | <track-repeat>` values.
+    ///
+    /// If there's no `<line-names>`, then it's represented by an empty vector.
+    /// For N values, there will be N+1 `<line-names>`, and so this vector's
+    /// length is always one value more than that of the `<track-size>`.
+    pub line_names: crate::OwnedSlice<crate::OwnedSlice<CustomIdent>>,
+}
+
+pub use self::GenericTrackList as TrackList;
+
+impl<L, I> TrackList<L, I> {
+    /// Whether this track list is an explicit track list (that is, doesn't have
+    /// any repeat values).
+    pub fn is_explicit(&self) -> bool {
+        !self.values.iter().any(|v| v.is_repeat())
+    }
+
+    /// Whether this track list has an `<auto-repeat>` value.
+    pub fn has_auto_repeat(&self) -> bool {
+        self.auto_repeat_index < self.values.len()
+    }
+}
+
+impl<L: ToCss, I: ToCss> ToCss for TrackList<L, I> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let mut values_iter = self.values.iter().peekable();
+        let mut line_names_iter = self.line_names.iter().peekable();
+
+        for idx in 0.. {
+            let names = line_names_iter.next().unwrap(); // This should exist!
+            concat_serialize_idents("[", "]", names, " ", dest)?;
+
+            match values_iter.next() {
+                Some(value) => {
+                    if !names.is_empty() {
+                        dest.write_str(" ")?;
+                    }
+
+                    value.to_css(dest)?;
+                },
+                None => break,
+            }
+
+            if values_iter.peek().is_some() ||
+                line_names_iter.peek().map_or(false, |v| !v.is_empty()) ||
+                (idx + 1 == self.auto_repeat_index)
+            {
+                dest.write_str(" ")?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+/// The `<line-name-list>` for subgrids.
+///
+/// `subgrid [ <line-names> | repeat(<positive-integer> | auto-fill, <line-names>+) ]+`
+///
+/// https://drafts.csswg.org/css-grid-2/#typedef-line-name-list
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct LineNameList {
+    /// The optional `<line-name-list>`
+    pub names: crate::OwnedSlice<crate::OwnedSlice<CustomIdent>>,
+    /// Indicates the starting line names that requires `auto-fill`, if in bounds.
+    pub fill_start: usize,
+    /// Indicates the number of line names in the auto-fill
+    pub fill_len: usize,
+}
+
+impl Parse for LineNameList {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_ident_matching("subgrid")?;
+        let mut line_names = vec![];
+        let mut fill_data = None;
+        // Rather than truncating the result after inserting values, just
+        // have a maximum number of values. This gives us an early out on very
+        // large name lists, but more importantly prevents OOM on huge repeat
+        // expansions. (bug 1583429)
+        let mut max_remaining = MAX_GRID_LINE as usize;
+
+        loop {
+            let repeat_parse_result = input.try_parse(|input| {
+                input.expect_function_matching("repeat")?;
+                input.parse_nested_block(|input| {
+                    let count = RepeatCount::parse(context, input)?;
+                    input.expect_comma()?;
+                    let mut names_list = vec![];
+                    names_list.push(parse_line_names(input)?); // there should be at least one
+                    while let Ok(names) = input.try_parse(parse_line_names) {
+                        names_list.push(names);
+                    }
+                    Ok((names_list, count))
+                })
+            });
+            if let Ok((names_list, count)) = repeat_parse_result {
+                let mut handle_size = |n| {
+                    let n = cmp::min(n, max_remaining);
+                    max_remaining -= n;
+                    n
+                };
+                match count {
+                    // FIXME(emilio): we shouldn't expand repeat() at
+                    // parse time for subgrid. (bug 1583429)
+                    RepeatCount::Number(num) => {
+                        let n = handle_size(
+                            num.value() as usize * names_list.len());
+                        line_names.extend(
+                            names_list.iter().cloned().cycle().take(n));
+                    },
+                    RepeatCount::AutoFill if fill_data.is_none() => {
+                        let fill_idx = line_names.len();
+                        let fill_len = names_list.len();
+                        fill_data = Some((fill_idx, fill_len));
+                        let n = handle_size(fill_len);
+                        line_names.extend(names_list.into_iter().take(n));
+                    },
+                    _ => return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+                }
+            } else if let Ok(names) = input.try_parse(parse_line_names) {
+                if max_remaining > 0 {
+                    line_names.push(names);
+                    max_remaining -= 1;
+                }
+            } else {
+                break;
+            }
+        }
+
+        debug_assert!(line_names.len() <= MAX_GRID_LINE as usize);
+
+        let (fill_start, fill_len) = fill_data.unwrap_or((0, 0));
+
+        Ok(LineNameList {
+            names: line_names.into(),
+            fill_start: fill_start,
+            fill_len: fill_len,
+        })
+    }
+}
+
+impl ToCss for LineNameList {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("subgrid")?;
+        let fill_start = self.fill_start;
+        let fill_len = self.fill_len;
+        for (i, names) in self.names.iter().enumerate() {
+            if fill_len > 0 && i == fill_start {
+                dest.write_str(" repeat(auto-fill,")?;
+            }
+
+            dest.write_str(" [")?;
+
+            if let Some((ref first, rest)) = names.split_first() {
+                first.to_css(dest)?;
+                for name in rest {
+                    dest.write_str(" ")?;
+                    name.to_css(dest)?;
+                }
+            }
+
+            dest.write_str("]")?;
+            if fill_len > 0 && i == fill_start + fill_len - 1 {
+                dest.write_str(")")?;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+/// Variants for `<grid-template-rows> | <grid-template-columns>`
+#[derive(
+    Animate,
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericGridTemplateComponent<L, I> {
+    /// `none` value.
+    None,
+    /// The grid `<track-list>`
+    TrackList(
+        #[animation(field_bound)]
+        #[compute(field_bound)]
+        #[resolve(field_bound)]
+        #[shmem(field_bound)]
+        Box<GenericTrackList<L, I>>,
+    ),
+    /// A `subgrid <line-name-list>?`
+    /// TODO: Support animations for this after subgrid is addressed in [grid-2] spec.
+    #[animation(error)]
+    Subgrid(Box<LineNameList>),
+    /// `masonry` value.
+    /// https://github.com/w3c/csswg-drafts/issues/4650
+    Masonry,
+}
+
+pub use self::GenericGridTemplateComponent as GridTemplateComponent;
+
+impl<L, I> GridTemplateComponent<L, I> {
+    /// The initial value.
+    const INITIAL_VALUE: Self = Self::None;
+
+    /// Returns length of the <track-list>s <track-size>
+    pub fn track_list_len(&self) -> usize {
+        match *self {
+            GridTemplateComponent::TrackList(ref tracklist) => tracklist.values.len(),
+            _ => 0,
+        }
+    }
+
+    /// Returns true if `self` is the initial value.
+    pub fn is_initial(&self) -> bool {
+        matches!(*self, Self::None) // FIXME: can't use Self::INITIAL_VALUE here yet: https://github.com/rust-lang/rust/issues/66585
+    }
+}
+
+impl<L, I> Default for GridTemplateComponent<L, I> {
+    #[inline]
+    fn default() -> Self {
+        Self::INITIAL_VALUE
+    }
+}
diff --git a/servo/components/style/values/generics/image.rs b/servo/components/style/values/generics/image.rs
new file mode 100644
index 0000000000..46e040cd27
--- /dev/null
+++ b/servo/components/style/values/generics/image.rs
@@ -0,0 +1,614 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for the handling of [images].
+//!
+//! [images]: https://drafts.csswg.org/css-images/#image-values
+
+use crate::custom_properties;
+use crate::values::generics::position::PositionComponent;
+use crate::values::generics::Optional;
+use crate::values::serialize_atom_identifier;
+use crate::Atom;
+use crate::Zero;
+use servo_arc::Arc;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// An `<image> | none` value.
+///
+/// https://drafts.csswg.org/css-images/#image-values
+#[derive(
+    Clone, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericImage<G, MozImageRect, ImageUrl, Color, Percentage, Resolution> {
+    /// `none` variant.
+    None,
+    /// A `<url()>` image.
+    Url(ImageUrl),
+
+    /// A `<gradient>` image.  Gradients are rather large, and not nearly as
+    /// common as urls, so we box them here to keep the size of this enum sane.
+    Gradient(Box<G>),
+    /// A `-moz-image-rect` image.  Also fairly large and rare.
+    // not cfg’ed out on non-Gecko to avoid `error[E0392]: parameter `MozImageRect` is never used`
+    // Instead we make MozImageRect an empty enum
+    Rect(Box<MozImageRect>),
+
+    /// A `-moz-element(# <element-id>)`
+    #[cfg(feature = "gecko")]
+    #[css(function = "-moz-element")]
+    Element(Atom),
+
+    /// A paint worklet image.
+    /// <https://drafts.css-houdini.org/css-paint-api/>
+    #[cfg(feature = "servo-layout-2013")]
+    PaintWorklet(PaintWorklet),
+
+    /// A `<cross-fade()>` image. Storing this directly inside of
+    /// GenericImage increases the size by 8 bytes so we box it here
+    /// and store images directly inside of cross-fade instead of
+    /// boxing them there.
+    CrossFade(Box<GenericCrossFade<Self, Color, Percentage>>),
+
+    /// An `image-set()` function.
+    ImageSet(#[compute(field_bound)] Box<GenericImageSet<Self, Resolution>>),
+}
+
+pub use self::GenericImage as Image;
+
+/// <https://drafts.csswg.org/css-images-4/#cross-fade-function>
+#[derive(
+    Clone, Debug, MallocSizeOf, PartialEq, ToResolvedValue, ToShmem, ToCss, ToComputedValue,
+)]
+#[css(comma, function = "cross-fade")]
+#[repr(C)]
+pub struct GenericCrossFade<Image, Color, Percentage> {
+    /// All of the image percent pairings passed as arguments to
+    /// cross-fade.
+    #[css(iterable)]
+    pub elements: crate::OwnedSlice<GenericCrossFadeElement<Image, Color, Percentage>>,
+}
+
+/// An optional percent and a cross fade image.
+#[derive(
+    Clone, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem, ToCss,
+)]
+#[repr(C)]
+pub struct GenericCrossFadeElement<Image, Color, Percentage> {
+    /// The percent of the final image that `image` will be.
+    pub percent: Optional<Percentage>,
+    /// A color or image that will be blended when cross-fade is
+    /// evaluated.
+    pub image: GenericCrossFadeImage<Image, Color>,
+}
+
+/// An image or a color. `cross-fade` takes either when blending
+/// images together.
+#[derive(
+    Clone, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem, ToCss,
+)]
+#[repr(C, u8)]
+pub enum GenericCrossFadeImage<I, C> {
+    /// A boxed image value. Boxing provides indirection so images can
+    /// be cross-fades and cross-fades can be images.
+    Image(I),
+    /// A color value.
+    Color(C),
+}
+
+pub use self::GenericCrossFade as CrossFade;
+pub use self::GenericCrossFadeElement as CrossFadeElement;
+pub use self::GenericCrossFadeImage as CrossFadeImage;
+
+/// https://drafts.csswg.org/css-images-4/#image-set-notation
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToCss, ToResolvedValue, ToShmem)]
+#[css(comma, function = "image-set")]
+#[repr(C)]
+pub struct GenericImageSet<Image, Resolution> {
+    /// The index of the selected candidate. Zero for specified values.
+    #[css(skip)]
+    pub selected_index: usize,
+
+    /// All of the image and resolution pairs.
+    #[css(iterable)]
+    pub items: crate::OwnedSlice<GenericImageSetItem<Image, Resolution>>,
+}
+
+/// An optional percent and a cross fade image.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem)]
+#[repr(C)]
+pub struct GenericImageSetItem<Image, Resolution> {
+    /// `<image>`. `<string>` is converted to `Image::Url` at parse time.
+    pub image: Image,
+    /// The `<resolution>`.
+    ///
+    /// TODO: Skip serialization if it is 1x.
+    pub resolution: Resolution,
+
+    /// The `type(<string>)`
+    /// (Optional) Specify the image's MIME type
+    pub mime_type: crate::OwnedStr,
+
+    /// True if mime_type has been specified
+    pub has_mime_type: bool,
+}
+
+impl<I: style_traits::ToCss, R: style_traits::ToCss> ToCss for GenericImageSetItem<I, R> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        self.image.to_css(dest)?;
+        dest.write_str(" ")?;
+        self.resolution.to_css(dest)?;
+
+        if self.has_mime_type {
+            dest.write_str(" ")?;
+            dest.write_str("type(")?;
+            self.mime_type.to_css(dest)?;
+            dest.write_str(")")?;
+        }
+        Ok(())
+    }
+}
+
+pub use self::GenericImageSet as ImageSet;
+pub use self::GenericImageSetItem as ImageSetItem;
+
+/// A CSS gradient.
+/// <https://drafts.csswg.org/css-images/#gradients>
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem)]
+#[repr(C)]
+pub enum GenericGradient<
+    LineDirection,
+    LengthPercentage,
+    NonNegativeLength,
+    NonNegativeLengthPercentage,
+    Position,
+    Angle,
+    AngleOrPercentage,
+    Color,
+> {
+    /// A linear gradient.
+    Linear {
+        /// Line direction
+        direction: LineDirection,
+        /// The color stops and interpolation hints.
+        items: crate::OwnedSlice<GenericGradientItem<Color, LengthPercentage>>,
+        /// True if this is a repeating gradient.
+        repeating: bool,
+        /// Compatibility mode.
+        compat_mode: GradientCompatMode,
+    },
+    /// A radial gradient.
+    Radial {
+        /// Shape of gradient
+        shape: GenericEndingShape<NonNegativeLength, NonNegativeLengthPercentage>,
+        /// Center of gradient
+        position: Position,
+        /// The color stops and interpolation hints.
+        items: crate::OwnedSlice<GenericGradientItem<Color, LengthPercentage>>,
+        /// True if this is a repeating gradient.
+        repeating: bool,
+        /// Compatibility mode.
+        compat_mode: GradientCompatMode,
+    },
+    /// A conic gradient.
+    Conic {
+        /// Start angle of gradient
+        angle: Angle,
+        /// Center of gradient
+        position: Position,
+        /// The color stops and interpolation hints.
+        items: crate::OwnedSlice<GenericGradientItem<Color, AngleOrPercentage>>,
+        /// True if this is a repeating gradient.
+        repeating: bool,
+    },
+}
+
+pub use self::GenericGradient as Gradient;
+
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[repr(u8)]
+/// Whether we used the modern notation or the compatibility `-webkit`, `-moz` prefixes.
+pub enum GradientCompatMode {
+    /// Modern syntax.
+    Modern,
+    /// `-webkit` prefix.
+    WebKit,
+    /// `-moz` prefix
+    Moz,
+}
+
+/// A radial gradient's ending shape.
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToCss, ToResolvedValue, ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericEndingShape<NonNegativeLength, NonNegativeLengthPercentage> {
+    /// A circular gradient.
+    Circle(GenericCircle<NonNegativeLength>),
+    /// An elliptic gradient.
+    Ellipse(GenericEllipse<NonNegativeLengthPercentage>),
+}
+
+pub use self::GenericEndingShape as EndingShape;
+
+/// A circle shape.
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericCircle<NonNegativeLength> {
+    /// A circle radius.
+    Radius(NonNegativeLength),
+    /// A circle extent.
+    Extent(ShapeExtent),
+}
+
+pub use self::GenericCircle as Circle;
+
+/// An ellipse shape.
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToCss, ToResolvedValue, ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericEllipse<NonNegativeLengthPercentage> {
+    /// An ellipse pair of radii.
+    Radii(NonNegativeLengthPercentage, NonNegativeLengthPercentage),
+    /// An ellipse extent.
+    Extent(ShapeExtent),
+}
+
+pub use self::GenericEllipse as Ellipse;
+
+/// <https://drafts.csswg.org/css-images/#typedef-extent-keyword>
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ShapeExtent {
+    ClosestSide,
+    FarthestSide,
+    ClosestCorner,
+    FarthestCorner,
+    Contain,
+    Cover,
+}
+
+/// A gradient item.
+/// <https://drafts.csswg.org/css-images-4/#color-stop-syntax>
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToCss, ToResolvedValue, ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericGradientItem<Color, T> {
+    /// A simple color stop, without position.
+    SimpleColorStop(Color),
+    /// A complex color stop, with a position.
+    ComplexColorStop {
+        /// The color for the stop.
+        color: Color,
+        /// The position for the stop.
+        position: T,
+    },
+    /// An interpolation hint.
+    InterpolationHint(T),
+}
+
+pub use self::GenericGradientItem as GradientItem;
+
+/// A color stop.
+/// <https://drafts.csswg.org/css-images/#typedef-color-stop-list>
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToCss, ToResolvedValue, ToShmem,
+)]
+pub struct ColorStop<Color, T> {
+    /// The color of this stop.
+    pub color: Color,
+    /// The position of this stop.
+    pub position: Option<T>,
+}
+
+impl<Color, T> ColorStop<Color, T> {
+    /// Convert the color stop into an appropriate `GradientItem`.
+    #[inline]
+    pub fn into_item(self) -> GradientItem<Color, T> {
+        match self.position {
+            Some(position) => GradientItem::ComplexColorStop {
+                color: self.color,
+                position,
+            },
+            None => GradientItem::SimpleColorStop(self.color),
+        }
+    }
+}
+
+/// Specified values for a paint worklet.
+/// <https://drafts.css-houdini.org/css-paint-api/>
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+#[derive(Clone, Debug, PartialEq, ToComputedValue, ToResolvedValue, ToShmem)]
+pub struct PaintWorklet {
+    /// The name the worklet was registered with.
+    pub name: Atom,
+    /// The arguments for the worklet.
+    /// TODO: store a parsed representation of the arguments.
+    #[cfg_attr(feature = "servo", ignore_malloc_size_of = "Arc")]
+    #[compute(no_field_bound)]
+    #[resolve(no_field_bound)]
+    pub arguments: Vec<Arc<custom_properties::SpecifiedValue>>,
+}
+
+impl ::style_traits::SpecifiedValueInfo for PaintWorklet {}
+
+impl ToCss for PaintWorklet {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("paint(")?;
+        serialize_atom_identifier(&self.name, dest)?;
+        for argument in &self.arguments {
+            dest.write_str(", ")?;
+            argument.to_css(dest)?;
+        }
+        dest.write_str(")")
+    }
+}
+
+/// Values for `moz-image-rect`.
+///
+/// `-moz-image-rect(<uri>, top, right, bottom, left);`
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma, function = "-moz-image-rect")]
+#[repr(C)]
+pub struct GenericMozImageRect<NumberOrPercentage, MozImageRectUrl> {
+    pub url: MozImageRectUrl,
+    pub top: NumberOrPercentage,
+    pub right: NumberOrPercentage,
+    pub bottom: NumberOrPercentage,
+    pub left: NumberOrPercentage,
+}
+
+pub use self::GenericMozImageRect as MozImageRect;
+
+impl<G, R, U, C, P, Resolution> fmt::Debug for Image<G, R, U, C, P, Resolution>
+where
+    Image<G, R, U, C, P, Resolution>: ToCss,
+{
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.to_css(&mut CssWriter::new(f))
+    }
+}
+
+impl<G, R, U, C, P, Resolution> ToCss for Image<G, R, U, C, P, Resolution>
+where
+    G: ToCss,
+    R: ToCss,
+    U: ToCss,
+    C: ToCss,
+    P: ToCss,
+    Resolution: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            Image::None => dest.write_str("none"),
+            Image::Url(ref url) => url.to_css(dest),
+            Image::Gradient(ref gradient) => gradient.to_css(dest),
+            Image::Rect(ref rect) => rect.to_css(dest),
+            #[cfg(feature = "servo-layout-2013")]
+            Image::PaintWorklet(ref paint_worklet) => paint_worklet.to_css(dest),
+            #[cfg(feature = "gecko")]
+            Image::Element(ref selector) => {
+                dest.write_str("-moz-element(#")?;
+                serialize_atom_identifier(selector, dest)?;
+                dest.write_str(")")
+            },
+            Image::ImageSet(ref is) => is.to_css(dest),
+            Image::CrossFade(ref cf) => cf.to_css(dest),
+        }
+    }
+}
+
+impl<D, LP, NL, NLP, P, A: Zero, AoP, C> ToCss for Gradient<D, LP, NL, NLP, P, A, AoP, C>
+where
+    D: LineDirection,
+    LP: ToCss,
+    NL: ToCss,
+    NLP: ToCss,
+    P: PositionComponent + ToCss,
+    A: ToCss,
+    AoP: ToCss,
+    C: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let (compat_mode, repeating) = match *self {
+            Gradient::Linear {
+                compat_mode,
+                repeating,
+                ..
+            } => (compat_mode, repeating),
+            Gradient::Radial {
+                compat_mode,
+                repeating,
+                ..
+            } => (compat_mode, repeating),
+            Gradient::Conic { repeating, .. } => (GradientCompatMode::Modern, repeating),
+        };
+
+        match compat_mode {
+            GradientCompatMode::WebKit => dest.write_str("-webkit-")?,
+            GradientCompatMode::Moz => dest.write_str("-moz-")?,
+            _ => {},
+        }
+
+        if repeating {
+            dest.write_str("repeating-")?;
+        }
+
+        match *self {
+            Gradient::Linear {
+                ref direction,
+                ref items,
+                compat_mode,
+                ..
+            } => {
+                dest.write_str("linear-gradient(")?;
+                let mut skip_comma = if !direction.points_downwards(compat_mode) {
+                    direction.to_css(dest, compat_mode)?;
+                    false
+                } else {
+                    true
+                };
+                for item in &**items {
+                    if !skip_comma {
+                        dest.write_str(", ")?;
+                    }
+                    skip_comma = false;
+                    item.to_css(dest)?;
+                }
+            },
+            Gradient::Radial {
+                ref shape,
+                ref position,
+                ref items,
+                compat_mode,
+                ..
+            } => {
+                dest.write_str("radial-gradient(")?;
+                let omit_shape = match *shape {
+                    EndingShape::Ellipse(Ellipse::Extent(ShapeExtent::Cover)) |
+                    EndingShape::Ellipse(Ellipse::Extent(ShapeExtent::FarthestCorner)) => true,
+                    _ => false,
+                };
+                let omit_position = position.is_center();
+                if compat_mode == GradientCompatMode::Modern {
+                    if !omit_shape {
+                        shape.to_css(dest)?;
+                        if !omit_position {
+                            dest.write_str(" ")?;
+                        }
+                    }
+                    if !omit_position {
+                        dest.write_str("at ")?;
+                        position.to_css(dest)?;
+                    }
+                } else {
+                    if !omit_position {
+                        position.to_css(dest)?;
+                        if !omit_shape {
+                            dest.write_str(", ")?;
+                        }
+                    }
+                    if !omit_shape {
+                        shape.to_css(dest)?;
+                    }
+                }
+                let mut skip_comma = omit_shape && omit_position;
+                for item in &**items {
+                    if !skip_comma {
+                        dest.write_str(", ")?;
+                    }
+                    skip_comma = false;
+                    item.to_css(dest)?;
+                }
+            },
+            Gradient::Conic {
+                ref angle,
+                ref position,
+                ref items,
+                ..
+            } => {
+                dest.write_str("conic-gradient(")?;
+                let omit_angle = angle.is_zero();
+                let omit_position = position.is_center();
+                if !omit_angle {
+                    dest.write_str("from ")?;
+                    angle.to_css(dest)?;
+                    if !omit_position {
+                        dest.write_str(" ")?;
+                    }
+                }
+                if !omit_position {
+                    dest.write_str("at ")?;
+                    position.to_css(dest)?;
+                }
+                let mut skip_comma = omit_angle && omit_position;
+                for item in &**items {
+                    if !skip_comma {
+                        dest.write_str(", ")?;
+                    }
+                    skip_comma = false;
+                    item.to_css(dest)?;
+                }
+            },
+        }
+        dest.write_str(")")
+    }
+}
+
+/// The direction of a linear gradient.
+pub trait LineDirection {
+    /// Whether this direction points towards, and thus can be omitted.
+    fn points_downwards(&self, compat_mode: GradientCompatMode) -> bool;
+
+    /// Serialises this direction according to the compatibility mode.
+    fn to_css<W>(&self, dest: &mut CssWriter<W>, compat_mode: GradientCompatMode) -> fmt::Result
+    where
+        W: Write;
+}
+
+impl<L> ToCss for Circle<L>
+where
+    L: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            Circle::Extent(ShapeExtent::FarthestCorner) | Circle::Extent(ShapeExtent::Cover) => {
+                dest.write_str("circle")
+            },
+            Circle::Extent(keyword) => {
+                dest.write_str("circle ")?;
+                keyword.to_css(dest)
+            },
+            Circle::Radius(ref length) => length.to_css(dest),
+        }
+    }
+}
diff --git a/servo/components/style/values/generics/length.rs b/servo/components/style/values/generics/length.rs
new file mode 100644
index 0000000000..de0dd7fbc1
--- /dev/null
+++ b/servo/components/style/values/generics/length.rs
@@ -0,0 +1,304 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to length.
+
+use crate::parser::{Parse, ParserContext};
+#[cfg(feature = "gecko")]
+use crate::Zero;
+use cssparser::Parser;
+use style_traits::ParseError;
+
+/// A `<length-percentage> | auto` value.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericLengthPercentageOrAuto<LengthPercent> {
+    LengthPercentage(LengthPercent),
+    Auto,
+}
+
+pub use self::GenericLengthPercentageOrAuto as LengthPercentageOrAuto;
+
+impl<LengthPercentage> LengthPercentageOrAuto<LengthPercentage> {
+    /// `auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        LengthPercentageOrAuto::Auto
+    }
+
+    /// Whether this is the `auto` value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, LengthPercentageOrAuto::Auto)
+    }
+
+    /// A helper function to parse this with quirks or not and so forth.
+    pub fn parse_with<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        parser: impl FnOnce(
+            &ParserContext,
+            &mut Parser<'i, 't>,
+        ) -> Result<LengthPercentage, ParseError<'i>>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try_parse(|i| i.expect_ident_matching("auto")).is_ok() {
+            return Ok(LengthPercentageOrAuto::Auto);
+        }
+
+        Ok(LengthPercentageOrAuto::LengthPercentage(parser(
+            context, input,
+        )?))
+    }
+}
+
+impl<LengthPercentage> LengthPercentageOrAuto<LengthPercentage>
+where
+    LengthPercentage: Clone,
+{
+    /// Resolves `auto` values by calling `f`.
+    #[inline]
+    pub fn auto_is(&self, f: impl FnOnce() -> LengthPercentage) -> LengthPercentage {
+        match self {
+            LengthPercentageOrAuto::LengthPercentage(length) => length.clone(),
+            LengthPercentageOrAuto::Auto => f(),
+        }
+    }
+
+    /// Returns the non-`auto` value, if any.
+    #[inline]
+    pub fn non_auto(&self) -> Option<LengthPercentage> {
+        match self {
+            LengthPercentageOrAuto::LengthPercentage(length) => Some(length.clone()),
+            LengthPercentageOrAuto::Auto => None,
+        }
+    }
+
+    /// Maps the length of this value.
+    pub fn map<T>(&self, f: impl FnOnce(LengthPercentage) -> T) -> LengthPercentageOrAuto<T> {
+        match self {
+            LengthPercentageOrAuto::LengthPercentage(l) => {
+                LengthPercentageOrAuto::LengthPercentage(f(l.clone()))
+            },
+            LengthPercentageOrAuto::Auto => LengthPercentageOrAuto::Auto,
+        }
+    }
+}
+
+impl<LengthPercentage: Zero> Zero for LengthPercentageOrAuto<LengthPercentage> {
+    fn zero() -> Self {
+        LengthPercentageOrAuto::LengthPercentage(Zero::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        match *self {
+            LengthPercentageOrAuto::LengthPercentage(ref l) => l.is_zero(),
+            LengthPercentageOrAuto::Auto => false,
+        }
+    }
+}
+
+impl<LengthPercentage: Parse> Parse for LengthPercentageOrAuto<LengthPercentage> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with(context, input, LengthPercentage::parse)
+    }
+}
+
+/// A generic value for the `width`, `height`, `min-width`, or `min-height` property.
+///
+/// Unlike `max-width` or `max-height` properties, a Size can be `auto`,
+/// and cannot be `none`.
+///
+/// Note that it only accepts non-negative values.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericSize<LengthPercent> {
+    LengthPercentage(LengthPercent),
+    Auto,
+    #[animation(error)]
+    MaxContent,
+    #[animation(error)]
+    MinContent,
+    #[animation(error)]
+    FitContent,
+    #[animation(error)]
+    MozAvailable,
+    #[animation(error)]
+    #[css(function = "fit-content")]
+    FitContentFunction(LengthPercent),
+}
+
+pub use self::GenericSize as Size;
+
+impl<LengthPercentage> Size<LengthPercentage> {
+    /// `auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        Size::Auto
+    }
+
+    /// Returns whether we're the auto value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, Size::Auto)
+    }
+}
+
+/// A generic value for the `max-width` or `max-height` property.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericMaxSize<LengthPercent> {
+    LengthPercentage(LengthPercent),
+    None,
+    #[animation(error)]
+    MaxContent,
+    #[animation(error)]
+    MinContent,
+    #[animation(error)]
+    FitContent,
+    #[animation(error)]
+    MozAvailable,
+    #[animation(error)]
+    #[css(function = "fit-content")]
+    FitContentFunction(LengthPercent),
+}
+
+pub use self::GenericMaxSize as MaxSize;
+
+impl<LengthPercentage> MaxSize<LengthPercentage> {
+    /// `none` value.
+    #[inline]
+    pub fn none() -> Self {
+        MaxSize::None
+    }
+}
+
+/// A generic `<length>` | `<number>` value for the `tab-size` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericLengthOrNumber<L, N> {
+    /// A number.
+    ///
+    /// NOTE: Numbers need to be before lengths, in order to parse them
+    /// first, since `0` should be a number, not the `0px` length.
+    Number(N),
+    /// A length.
+    Length(L),
+}
+
+pub use self::GenericLengthOrNumber as LengthOrNumber;
+
+impl<L, N: Zero> Zero for LengthOrNumber<L, N> {
+    fn zero() -> Self {
+        LengthOrNumber::Number(Zero::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        match *self {
+            LengthOrNumber::Number(ref n) => n.is_zero(),
+            LengthOrNumber::Length(..) => false,
+        }
+    }
+}
+
+/// A generic `<length-percentage>` | normal` value.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+#[allow(missing_docs)]
+pub enum GenericLengthPercentageOrNormal<LengthPercent> {
+    LengthPercentage(LengthPercent),
+    Normal,
+}
+
+pub use self::GenericLengthPercentageOrNormal as LengthPercentageOrNormal;
+
+impl<LengthPercent> LengthPercentageOrNormal<LengthPercent> {
+    /// Returns the normal value.
+    #[inline]
+    pub fn normal() -> Self {
+        LengthPercentageOrNormal::Normal
+    }
+}
diff --git a/servo/components/style/values/generics/mod.rs b/servo/components/style/values/generics/mod.rs
new file mode 100644
index 0000000000..58c982f78c
--- /dev/null
+++ b/servo/components/style/values/generics/mod.rs
@@ -0,0 +1,385 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types that share their serialization implementations
+//! for both specified and computed values.
+
+use super::CustomIdent;
+use crate::counter_style::{parse_counter_style_name, Symbols};
+use crate::parser::{Parse, ParserContext};
+use crate::Zero;
+use cssparser::Parser;
+use std::ops::Add;
+use style_traits::{KeywordsCollectFn, ParseError, SpecifiedValueInfo, StyleParseErrorKind};
+
+pub mod background;
+pub mod basic_shape;
+pub mod border;
+#[path = "box.rs"]
+pub mod box_;
+pub mod calc;
+pub mod color;
+pub mod column;
+pub mod counters;
+pub mod easing;
+pub mod effects;
+pub mod flex;
+pub mod font;
+pub mod grid;
+pub mod image;
+pub mod length;
+pub mod motion;
+pub mod page;
+pub mod position;
+pub mod ratio;
+pub mod rect;
+pub mod size;
+pub mod svg;
+pub mod text;
+pub mod transform;
+pub mod ui;
+pub mod url;
+
+/// https://drafts.csswg.org/css-counter-styles/#typedef-symbols-type
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum SymbolsType {
+    Cyclic,
+    Numeric,
+    Alphabetic,
+    Symbolic,
+    Fixed,
+}
+
+/// <https://drafts.csswg.org/css-counter-styles/#typedef-counter-style>
+///
+/// Note that 'none' is not a valid name.
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
+#[derive(Clone, Debug, Eq, PartialEq, ToComputedValue, ToCss, ToResolvedValue, ToShmem)]
+#[repr(u8)]
+pub enum CounterStyle {
+    /// `<counter-style-name>`
+    Name(CustomIdent),
+    /// `symbols()`
+    #[css(function)]
+    Symbols(#[css(skip_if = "is_symbolic")] SymbolsType, Symbols),
+}
+
+#[inline]
+fn is_symbolic(symbols_type: &SymbolsType) -> bool {
+    *symbols_type == SymbolsType::Symbolic
+}
+
+impl CounterStyle {
+    /// disc value
+    pub fn disc() -> Self {
+        CounterStyle::Name(CustomIdent(atom!("disc")))
+    }
+
+    /// decimal value
+    pub fn decimal() -> Self {
+        CounterStyle::Name(CustomIdent(atom!("decimal")))
+    }
+
+    /// Is this a bullet? (i.e. `list-style-type: disc|circle|square|disclosure-closed|disclosure-open`)
+    #[inline]
+    pub fn is_bullet(&self) -> bool {
+        match self {
+            CounterStyle::Name(CustomIdent(ref name)) => {
+                name == &atom!("disc") ||
+                    name == &atom!("circle") ||
+                    name == &atom!("square") ||
+                    name == &atom!("disclosure-closed") ||
+                    name == &atom!("disclosure-open")
+            },
+            _ => false,
+        }
+    }
+}
+
+impl Parse for CounterStyle {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(name) = input.try_parse(|i| parse_counter_style_name(i)) {
+            return Ok(CounterStyle::Name(name));
+        }
+        input.expect_function_matching("symbols")?;
+        input.parse_nested_block(|input| {
+            let symbols_type = input
+                .try_parse(SymbolsType::parse)
+                .unwrap_or(SymbolsType::Symbolic);
+            let symbols = Symbols::parse(context, input)?;
+            // There must be at least two symbols for alphabetic or
+            // numeric system.
+            if (symbols_type == SymbolsType::Alphabetic || symbols_type == SymbolsType::Numeric) &&
+                symbols.0.len() < 2
+            {
+                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+            // Identifier is not allowed in symbols() function.
+            if symbols.0.iter().any(|sym| !sym.is_allowed_in_symbols()) {
+                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+            Ok(CounterStyle::Symbols(symbols_type, symbols))
+        })
+    }
+}
+
+impl SpecifiedValueInfo for CounterStyle {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        // XXX The best approach for implementing this is probably
+        // having a CounterStyleName type wrapping CustomIdent, and
+        // put the predefined list for that type in counter_style mod.
+        // But that's a non-trivial change itself, so we use a simpler
+        // approach here.
+        macro_rules! predefined {
+            ($($name:expr,)+) => {
+                f(&["symbols", $($name,)+])
+            }
+        }
+        include!("../../counter_style/predefined.rs");
+    }
+}
+
+/// A wrapper of Non-negative values.
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct NonNegative<T>(pub T);
+
+impl<T: Add<Output = T>> Add<NonNegative<T>> for NonNegative<T> {
+    type Output = Self;
+
+    fn add(self, other: Self) -> Self {
+        NonNegative(self.0 + other.0)
+    }
+}
+
+impl<T: Zero> Zero for NonNegative<T> {
+    fn is_zero(&self) -> bool {
+        self.0.is_zero()
+    }
+
+    fn zero() -> Self {
+        NonNegative(T::zero())
+    }
+}
+
+/// A wrapper of greater-than-or-equal-to-one values.
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct GreaterThanOrEqualToOne<T>(pub T);
+
+/// A wrapper of values between zero and one.
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    PartialOrd,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct ZeroToOne<T>(pub T);
+
+/// A clip rect for clip and image-region
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function = "rect", comma)]
+#[repr(C)]
+pub struct GenericClipRect<LengthOrAuto> {
+    pub top: LengthOrAuto,
+    pub right: LengthOrAuto,
+    pub bottom: LengthOrAuto,
+    pub left: LengthOrAuto,
+}
+
+pub use self::GenericClipRect as ClipRect;
+
+/// Either a clip-rect or `auto`.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericClipRectOrAuto<R> {
+    Auto,
+    Rect(R),
+}
+
+pub use self::GenericClipRectOrAuto as ClipRectOrAuto;
+
+impl<L> ClipRectOrAuto<L> {
+    /// Returns the `auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        ClipRectOrAuto::Auto
+    }
+
+    /// Returns whether this value is the `auto` value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, ClipRectOrAuto::Auto)
+    }
+}
+
+pub use page::PageSize;
+
+/// An optional value, much like `Option<T>`, but with a defined struct layout
+/// to be able to use it from C++ as well.
+///
+/// Note that this is relatively inefficient, struct-layout-wise, as you have
+/// one byte for the tag, but padding to the alignment of T. If you have
+/// multiple optional values and care about struct compactness, you might be
+/// better off "coalescing" the combinations into a parent enum. But that
+/// shouldn't matter for most use cases.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+    Serialize,
+    Deserialize,
+)]
+#[repr(C, u8)]
+pub enum Optional<T> {
+    #[css(skip)]
+    None,
+    Some(T),
+}
+
+impl<T> Optional<T> {
+    /// Returns whether this value is present.
+    pub fn is_some(&self) -> bool {
+        matches!(*self, Self::Some(..))
+    }
+
+    /// Returns whether this value is not present.
+    pub fn is_none(&self) -> bool {
+        matches!(*self, Self::None)
+    }
+
+    /// Turns this Optional<> into a regular rust Option<>.
+    pub fn into_rust(self) -> Option<T> {
+        match self {
+            Self::Some(v) => Some(v),
+            Self::None => None,
+        }
+    }
+
+    /// Return a reference to the containing value, if any, as a plain rust
+    /// Option<>.
+    pub fn as_ref(&self) -> Option<&T> {
+        match *self {
+            Self::Some(ref v) => Some(v),
+            Self::None => None,
+        }
+    }
+}
+
+impl<T> From<Option<T>> for Optional<T> {
+    fn from(rust: Option<T>) -> Self {
+        match rust {
+            Some(t) => Self::Some(t),
+            None => Self::None,
+        }
+    }
+}
diff --git a/servo/components/style/values/generics/motion.rs b/servo/components/style/values/generics/motion.rs
new file mode 100644
index 0000000000..25ba5873ad
--- /dev/null
+++ b/servo/components/style/values/generics/motion.rs
@@ -0,0 +1,117 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS Motion Path.
+
+use crate::values::specified::SVGPathData;
+
+/// The <size> in ray() function.
+///
+/// https://drafts.fxtf.org/motion-1/#valdef-offsetpath-size
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum RaySize {
+    ClosestSide,
+    ClosestCorner,
+    FarthestSide,
+    FarthestCorner,
+    Sides,
+}
+
+/// The `ray()` function, `ray( [ <angle> && <size> && contain? ] )`
+///
+/// https://drafts.fxtf.org/motion-1/#valdef-offsetpath-ray
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct RayFunction<Angle> {
+    /// The bearing angle with `0deg` pointing up and positive angles
+    /// representing clockwise rotation.
+    pub angle: Angle,
+    /// Decide the path length used when `offset-distance` is expressed
+    /// as a percentage.
+    #[animation(constant)]
+    pub size: RaySize,
+    /// Clamp `offset-distance` so that the box is entirely contained
+    /// within the path.
+    #[animation(constant)]
+    #[css(represents_keyword)]
+    pub contain: bool,
+}
+
+/// The offset-path value.
+///
+/// https://drafts.fxtf.org/motion-1/#offset-path-property
+/// cbindgen:private-default-tagged-enum-constructor=false
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericOffsetPath<Angle> {
+    // We could merge SVGPathData into ShapeSource, so we could reuse them. However,
+    // we don't want to support other value for offset-path, so use SVGPathData only for now.
+    /// Path value for path(<string>).
+    #[css(function)]
+    Path(SVGPathData),
+    /// ray() function, which defines a path in the polar coordinate system.
+    #[css(function)]
+    Ray(RayFunction<Angle>),
+    /// None value.
+    #[animation(error)]
+    None,
+    // Bug 1186329: Implement <basic-shape>, <geometry-box>, and <url>.
+}
+
+pub use self::GenericOffsetPath as OffsetPath;
+
+impl<Angle> OffsetPath<Angle> {
+    /// Return None.
+    #[inline]
+    pub fn none() -> Self {
+        OffsetPath::None
+    }
+}
diff --git a/servo/components/style/values/generics/page.rs b/servo/components/style/values/generics/page.rs
new file mode 100644
index 0000000000..ed81c9e534
--- /dev/null
+++ b/servo/components/style/values/generics/page.rs
@@ -0,0 +1,132 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! @page at-rule properties
+
+use crate::values::generics::NonNegative;
+use crate::values::specified::length::AbsoluteLength;
+
+/// Page size names.
+///
+/// https://drafts.csswg.org/css-page-3/#typedef-page-size-page-size
+#[derive(
+    Clone, Copy, Debug, Eq, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+#[repr(u8)]
+pub enum PaperSize {
+    /// ISO A5 media
+    A5,
+    /// ISO A4 media
+    A4,
+    /// ISO A3 media
+    A3,
+    /// ISO B5 media
+    B5,
+    /// ISO B4 media
+    B4,
+    /// JIS B5 media
+    JisB5,
+    /// JIS B4 media
+    JisB4,
+    /// North American Letter size
+    Letter,
+    /// North American Legal size
+    Legal,
+    /// North American Ledger size
+    Ledger,
+}
+
+impl PaperSize {
+    /// Gets the long edge length of the paper size
+    pub fn long_edge(&self) -> NonNegative<AbsoluteLength> {
+        NonNegative(match *self {
+            PaperSize::A5 => AbsoluteLength::Mm(210.0),
+            PaperSize::A4 => AbsoluteLength::Mm(297.0),
+            PaperSize::A3 => AbsoluteLength::Mm(420.0),
+            PaperSize::B5 => AbsoluteLength::Mm(250.0),
+            PaperSize::B4 => AbsoluteLength::Mm(353.0),
+            PaperSize::JisB5 => AbsoluteLength::Mm(257.0),
+            PaperSize::JisB4 => AbsoluteLength::Mm(364.0),
+            PaperSize::Letter => AbsoluteLength::In(11.0),
+            PaperSize::Legal => AbsoluteLength::In(14.0),
+            PaperSize::Ledger => AbsoluteLength::In(17.0),
+        })
+    }
+    /// Gets the short edge length of the paper size
+    pub fn short_edge(&self) -> NonNegative<AbsoluteLength> {
+        NonNegative(match *self {
+            PaperSize::A5 => AbsoluteLength::Mm(148.0),
+            PaperSize::A4 => AbsoluteLength::Mm(210.0),
+            PaperSize::A3 => AbsoluteLength::Mm(297.0),
+            PaperSize::B5 => AbsoluteLength::Mm(176.0),
+            PaperSize::B4 => AbsoluteLength::Mm(250.0),
+            PaperSize::JisB5 => AbsoluteLength::Mm(182.0),
+            PaperSize::JisB4 => AbsoluteLength::Mm(257.0),
+            PaperSize::Letter => AbsoluteLength::In(8.5),
+            PaperSize::Legal => AbsoluteLength::In(8.5),
+            PaperSize::Ledger => AbsoluteLength::In(11.0),
+        })
+    }
+}
+
+/// Paper orientation
+///
+/// https://drafts.csswg.org/css-page-3/#page-size-prop
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum PageSizeOrientation {
+    /// Portrait orientation
+    Portrait,
+    /// Landscape orientation
+    Landscape,
+}
+
+#[inline]
+fn is_portrait(orientation: &PageSizeOrientation) -> bool {
+    *orientation == PageSizeOrientation::Portrait
+}
+
+/// Page size property
+///
+/// https://drafts.csswg.org/css-page-3/#page-size-prop
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+#[repr(C, u8)]
+pub enum GenericPageSize<S> {
+    /// `auto` value.
+    Auto,
+    /// Page dimensions.
+    Size(S),
+    /// An orientation with no size.
+    Orientation(PageSizeOrientation),
+    /// Paper size by name
+    PaperSize(PaperSize, #[css(skip_if = "is_portrait")] PageSizeOrientation),
+}
+
+pub use self::GenericPageSize as PageSize;
+
+impl<S> PageSize<S> {
+    /// `auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        PageSize::Auto
+    }
+
+    /// Whether this is the `auto` value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, PageSize::Auto)
+    }
+}
diff --git a/servo/components/style/values/generics/position.rs b/servo/components/style/values/generics/position.rs
new file mode 100644
index 0000000000..17afb1c39b
--- /dev/null
+++ b/servo/components/style/values/generics/position.rs
@@ -0,0 +1,232 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS handling of specified and computed values of
+//! [`position`](https://drafts.csswg.org/css-backgrounds-3/#position)
+
+use crate::values::animated::ToAnimatedZero;
+use crate::values::generics::ratio::Ratio;
+
+/// A generic type for representing a CSS [position](https://drafts.csswg.org/css-values/#position).
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericPosition<H, V> {
+    /// The horizontal component of position.
+    pub horizontal: H,
+    /// The vertical component of position.
+    pub vertical: V,
+}
+
+impl<H, V> PositionComponent for Position<H, V>
+where
+    H: PositionComponent,
+    V: PositionComponent,
+{
+    #[inline]
+    fn is_center(&self) -> bool {
+        self.horizontal.is_center() && self.vertical.is_center()
+    }
+}
+
+pub use self::GenericPosition as Position;
+
+impl<H, V> Position<H, V> {
+    /// Returns a new position.
+    pub fn new(horizontal: H, vertical: V) -> Self {
+        Self {
+            horizontal,
+            vertical,
+        }
+    }
+}
+
+/// Implements a method that checks if the position is centered.
+pub trait PositionComponent {
+    /// Returns if the position component is 50% or center.
+    /// For pixel lengths, it always returns false.
+    fn is_center(&self) -> bool;
+}
+
+/// A generic type for representing an `Auto | <position>`.
+/// This is used by <offset-anchor> for now.
+/// https://drafts.fxtf.org/motion-1/#offset-anchor-property
+/// cbindgen:private-default-tagged-enum-constructor=false
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericPositionOrAuto<Pos> {
+    /// The <position> value.
+    Position(Pos),
+    /// The keyword `auto`.
+    Auto,
+}
+
+pub use self::GenericPositionOrAuto as PositionOrAuto;
+
+impl<Pos> PositionOrAuto<Pos> {
+    /// Return `auto`.
+    #[inline]
+    pub fn auto() -> Self {
+        PositionOrAuto::Auto
+    }
+}
+
+/// A generic value for the `z-index` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericZIndex<I> {
+    /// An integer value.
+    Integer(I),
+    /// The keyword `auto`.
+    Auto,
+}
+
+pub use self::GenericZIndex as ZIndex;
+
+impl<Integer> ZIndex<Integer> {
+    /// Returns `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        ZIndex::Auto
+    }
+
+    /// Returns whether `self` is `auto`.
+    #[inline]
+    pub fn is_auto(self) -> bool {
+        matches!(self, ZIndex::Auto)
+    }
+
+    /// Returns the integer value if it is an integer, or `auto`.
+    #[inline]
+    pub fn integer_or(self, auto: Integer) -> Integer {
+        match self {
+            ZIndex::Integer(n) => n,
+            ZIndex::Auto => auto,
+        }
+    }
+}
+
+/// Ratio or None.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum PreferredRatio<N> {
+    /// Without specified ratio
+    #[css(skip)]
+    None,
+    /// With specified ratio
+    Ratio(
+        #[animation(field_bound)]
+        #[css(field_bound)]
+        #[distance(field_bound)]
+        Ratio<N>,
+    ),
+}
+
+/// A generic value for the `aspect-ratio` property, the value is `auto || <ratio>`.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericAspectRatio<N> {
+    /// Specifiy auto or not.
+    #[animation(constant)]
+    #[css(represents_keyword)]
+    pub auto: bool,
+    /// The preferred aspect-ratio value.
+    #[animation(field_bound)]
+    #[css(field_bound)]
+    #[distance(field_bound)]
+    pub ratio: PreferredRatio<N>,
+}
+
+pub use self::GenericAspectRatio as AspectRatio;
+
+impl<N> AspectRatio<N> {
+    /// Returns `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        AspectRatio {
+            auto: true,
+            ratio: PreferredRatio::None,
+        }
+    }
+}
+
+impl<N> ToAnimatedZero for AspectRatio<N> {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
diff --git a/servo/components/style/values/generics/ratio.rs b/servo/components/style/values/generics/ratio.rs
new file mode 100644
index 0000000000..8c66fed602
--- /dev/null
+++ b/servo/components/style/values/generics/ratio.rs
@@ -0,0 +1,50 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values related to <ratio>.
+//! https://drafts.csswg.org/css-values/#ratios
+
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// A generic value for the `<ratio>` value.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct Ratio<N>(pub N, pub N);
+
+impl<N> ToCss for Ratio<N>
+where
+    N: ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0.to_css(dest)?;
+        // Even though 1 could be omitted, we don't per
+        // https://drafts.csswg.org/css-values-4/#ratio-value:
+        //
+        //     The second <number> is optional, defaulting to 1. However,
+        //     <ratio> is always serialized with both components.
+        //
+        // And for compat reasons, see bug 1669742.
+        //
+        // We serialize with spaces for consistency with all other
+        // slash-delimited things, see
+        // https://github.com/w3c/csswg-drafts/issues/4282
+        dest.write_str(" / ")?;
+        self.1.to_css(dest)?;
+        Ok(())
+    }
+}
diff --git a/servo/components/style/values/generics/rect.rs b/servo/components/style/values/generics/rect.rs
new file mode 100644
index 0000000000..dee21459a7
--- /dev/null
+++ b/servo/components/style/values/generics/rect.rs
@@ -0,0 +1,126 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values that are composed of four sides.
+
+use crate::parser::{Parse, ParserContext};
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ParseError, ToCss};
+
+/// A CSS value made of four components, where its `ToCss` impl will try to
+/// serialize as few components as possible, like for example in `border-width`.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct Rect<T>(pub T, pub T, pub T, pub T);
+
+impl<T> Rect<T> {
+    /// Returns a new `Rect<T>` value.
+    pub fn new(first: T, second: T, third: T, fourth: T) -> Self {
+        Rect(first, second, third, fourth)
+    }
+}
+
+impl<T> Rect<T>
+where
+    T: Clone,
+{
+    /// Returns a rect with all the values equal to `v`.
+    pub fn all(v: T) -> Self {
+        Rect::new(v.clone(), v.clone(), v.clone(), v)
+    }
+
+    /// Parses a new `Rect<T>` value with the given parse function.
+    pub fn parse_with<'i, 't, Parse>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        parse: Parse,
+    ) -> Result<Self, ParseError<'i>>
+    where
+        Parse: Fn(&ParserContext, &mut Parser<'i, 't>) -> Result<T, ParseError<'i>>,
+    {
+        let first = parse(context, input)?;
+        let second = if let Ok(second) = input.try_parse(|i| parse(context, i)) {
+            second
+        } else {
+            // <first>
+            return Ok(Self::new(
+                first.clone(),
+                first.clone(),
+                first.clone(),
+                first,
+            ));
+        };
+        let third = if let Ok(third) = input.try_parse(|i| parse(context, i)) {
+            third
+        } else {
+            // <first> <second>
+            return Ok(Self::new(first.clone(), second.clone(), first, second));
+        };
+        let fourth = if let Ok(fourth) = input.try_parse(|i| parse(context, i)) {
+            fourth
+        } else {
+            // <first> <second> <third>
+            return Ok(Self::new(first, second.clone(), third, second));
+        };
+        // <first> <second> <third> <fourth>
+        Ok(Self::new(first, second, third, fourth))
+    }
+}
+
+impl<T> Parse for Rect<T>
+where
+    T: Clone + Parse,
+{
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with(context, input, T::parse)
+    }
+}
+
+impl<T> ToCss for Rect<T>
+where
+    T: PartialEq + ToCss,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0.to_css(dest)?;
+        let same_vertical = self.0 == self.2;
+        let same_horizontal = self.1 == self.3;
+        if same_vertical && same_horizontal && self.0 == self.1 {
+            return Ok(());
+        }
+        dest.write_str(" ")?;
+        self.1.to_css(dest)?;
+        if same_vertical && same_horizontal {
+            return Ok(());
+        }
+        dest.write_str(" ")?;
+        self.2.to_css(dest)?;
+        if same_horizontal {
+            return Ok(());
+        }
+        dest.write_str(" ")?;
+        self.3.to_css(dest)
+    }
+}
diff --git a/servo/components/style/values/generics/size.rs b/servo/components/style/values/generics/size.rs
new file mode 100644
index 0000000000..e00eef28b9
--- /dev/null
+++ b/servo/components/style/values/generics/size.rs
@@ -0,0 +1,99 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic type for CSS properties that are composed by two dimensions.
+
+use crate::parser::ParserContext;
+use crate::Zero;
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ParseError, ToCss};
+
+/// A generic size, for `border-*-radius` longhand properties, or
+/// `border-spacing`.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[repr(C)]
+pub struct Size2D<L> {
+    pub width: L,
+    pub height: L,
+}
+
+impl<L> Size2D<L> {
+    #[inline]
+    /// Create a new `Size2D` for an area of given width and height.
+    pub fn new(width: L, height: L) -> Self {
+        Self { width, height }
+    }
+
+    /// Returns the width component.
+    pub fn width(&self) -> &L {
+        &self.width
+    }
+
+    /// Returns the height component.
+    pub fn height(&self) -> &L {
+        &self.height
+    }
+
+    /// Parse a `Size2D` with a given parsing function.
+    pub fn parse_with<'i, 't, F>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        parse_one: F,
+    ) -> Result<Self, ParseError<'i>>
+    where
+        L: Clone,
+        F: Fn(&ParserContext, &mut Parser<'i, 't>) -> Result<L, ParseError<'i>>,
+    {
+        let first = parse_one(context, input)?;
+        let second = input
+            .try_parse(|i| parse_one(context, i))
+            .unwrap_or_else(|_| first.clone());
+        Ok(Self::new(first, second))
+    }
+}
+
+impl<L> ToCss for Size2D<L>
+where
+    L: ToCss + PartialEq,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.width.to_css(dest)?;
+
+        if self.height != self.width {
+            dest.write_str(" ")?;
+            self.height.to_css(dest)?;
+        }
+
+        Ok(())
+    }
+}
+
+impl<L: Zero> Zero for Size2D<L> {
+    fn zero() -> Self {
+        Self::new(L::zero(), L::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        self.width.is_zero() && self.height.is_zero()
+    }
+}
diff --git a/servo/components/style/values/generics/svg.rs b/servo/components/style/values/generics/svg.rs
new file mode 100644
index 0000000000..43ba77f1ff
--- /dev/null
+++ b/servo/components/style/values/generics/svg.rs
@@ -0,0 +1,221 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values in SVG
+
+use crate::parser::{Parse, ParserContext};
+use cssparser::Parser;
+use style_traits::ParseError;
+
+/// The fallback of an SVG paint server value.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericSVGPaintFallback<C> {
+    /// The `none` keyword.
+    None,
+    /// A magic value that represents no fallback specified and serializes to
+    /// the empty string.
+    #[css(skip)]
+    Unset,
+    /// A color.
+    Color(C),
+}
+
+pub use self::GenericSVGPaintFallback as SVGPaintFallback;
+
+/// An SVG paint value
+///
+/// <https://www.w3.org/TR/SVG2/painting.html#SpecifyingPaint>
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[animation(no_bound(Url))]
+#[repr(C)]
+pub struct GenericSVGPaint<Color, Url> {
+    /// The paint source.
+    pub kind: GenericSVGPaintKind<Color, Url>,
+    /// The fallback color.
+    pub fallback: GenericSVGPaintFallback<Color>,
+}
+
+pub use self::GenericSVGPaint as SVGPaint;
+
+impl<C, U> Default for SVGPaint<C, U> {
+    fn default() -> Self {
+        Self {
+            kind: SVGPaintKind::None,
+            fallback: SVGPaintFallback::Unset,
+        }
+    }
+}
+
+/// An SVG paint value without the fallback.
+///
+/// Whereas the spec only allows PaintServer to have a fallback, Gecko lets the
+/// context properties have a fallback as well.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[animation(no_bound(U))]
+#[repr(C, u8)]
+pub enum GenericSVGPaintKind<C, U> {
+    /// `none`
+    #[animation(error)]
+    None,
+    /// `<color>`
+    Color(C),
+    /// `url(...)`
+    #[animation(error)]
+    PaintServer(U),
+    /// `context-fill`
+    ContextFill,
+    /// `context-stroke`
+    ContextStroke,
+}
+
+pub use self::GenericSVGPaintKind as SVGPaintKind;
+
+impl<C: Parse, U: Parse> Parse for SVGPaint<C, U> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let kind = SVGPaintKind::parse(context, input)?;
+        if matches!(kind, SVGPaintKind::None | SVGPaintKind::Color(..)) {
+            return Ok(SVGPaint {
+                kind,
+                fallback: SVGPaintFallback::Unset,
+            });
+        }
+        let fallback = input
+            .try_parse(|i| SVGPaintFallback::parse(context, i))
+            .unwrap_or(SVGPaintFallback::Unset);
+        Ok(SVGPaint { kind, fallback })
+    }
+}
+
+/// An SVG length value supports `context-value` in addition to length.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericSVGLength<L> {
+    /// `<length> | <percentage> | <number>`
+    LengthPercentage(L),
+    /// `context-value`
+    #[animation(error)]
+    ContextValue,
+}
+
+pub use self::GenericSVGLength as SVGLength;
+
+/// Generic value for stroke-dasharray.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericSVGStrokeDashArray<L> {
+    /// `[ <length> | <percentage> | <number> ]#`
+    #[css(comma)]
+    Values(#[css(if_empty = "none", iterable)] crate::OwnedSlice<L>),
+    /// `context-value`
+    ContextValue,
+}
+
+pub use self::GenericSVGStrokeDashArray as SVGStrokeDashArray;
+
+/// An SVG opacity value accepts `context-{fill,stroke}-opacity` in
+/// addition to opacity value.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericSVGOpacity<OpacityType> {
+    /// `<opacity-value>`
+    Opacity(OpacityType),
+    /// `context-fill-opacity`
+    #[animation(error)]
+    ContextFillOpacity,
+    /// `context-stroke-opacity`
+    #[animation(error)]
+    ContextStrokeOpacity,
+}
+
+pub use self::GenericSVGOpacity as SVGOpacity;
diff --git a/servo/components/style/values/generics/text.rs b/servo/components/style/values/generics/text.rs
new file mode 100644
index 0000000000..0062f30470
--- /dev/null
+++ b/servo/components/style/values/generics/text.rs
@@ -0,0 +1,157 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for text properties.
+
+use crate::parser::ParserContext;
+use crate::values::animated::ToAnimatedZero;
+use cssparser::Parser;
+use style_traits::ParseError;
+
+/// A generic value for the `initial-letter` property.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum InitialLetter<Number, Integer> {
+    /// `normal`
+    Normal,
+    /// `<number> <integer>?`
+    Specified(Number, Option<Integer>),
+}
+
+impl<N, I> InitialLetter<N, I> {
+    /// Returns `normal`.
+    #[inline]
+    pub fn normal() -> Self {
+        InitialLetter::Normal
+    }
+}
+
+/// A generic spacing value for the `letter-spacing` and `word-spacing` properties.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum Spacing<Value> {
+    /// `normal`
+    Normal,
+    /// `<value>`
+    Value(Value),
+}
+
+impl<Value> Spacing<Value> {
+    /// Returns `normal`.
+    #[inline]
+    pub fn normal() -> Self {
+        Spacing::Normal
+    }
+
+    /// Parses.
+    #[inline]
+    pub fn parse_with<'i, 't, F>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        parse: F,
+    ) -> Result<Self, ParseError<'i>>
+    where
+        F: FnOnce(&ParserContext, &mut Parser<'i, 't>) -> Result<Value, ParseError<'i>>,
+    {
+        if input
+            .try_parse(|i| i.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(Spacing::Normal);
+        }
+        parse(context, input).map(Spacing::Value)
+    }
+}
+
+#[cfg(feature = "gecko")]
+fn line_height_moz_block_height_enabled(context: &ParserContext) -> bool {
+    context.in_ua_sheet() ||
+        static_prefs::pref!("layout.css.line-height-moz-block-height.content.enabled")
+}
+
+/// A generic value for the `line-height` property.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToCss,
+    ToShmem,
+    ToResolvedValue,
+    Parse,
+)]
+#[repr(C, u8)]
+pub enum GenericLineHeight<N, L> {
+    /// `normal`
+    Normal,
+    /// `-moz-block-height`
+    #[cfg(feature = "gecko")]
+    #[parse(condition = "line_height_moz_block_height_enabled")]
+    MozBlockHeight,
+    /// `<number>`
+    Number(N),
+    /// `<length-percentage>`
+    Length(L),
+}
+
+pub use self::GenericLineHeight as LineHeight;
+
+impl<N, L> ToAnimatedZero for LineHeight<N, L> {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        Err(())
+    }
+}
+
+impl<N, L> LineHeight<N, L> {
+    /// Returns `normal`.
+    #[inline]
+    pub fn normal() -> Self {
+        LineHeight::Normal
+    }
+}
+
+/// Implements type for text-decoration-thickness
+/// which takes the grammar of auto | from-font | <length> | <percentage>
+///
+/// https://drafts.csswg.org/css-text-decor-4/
+#[repr(C, u8)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Animate,
+    Clone,
+    Copy,
+    ComputeSquaredDistance,
+    ToAnimatedZero,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum GenericTextDecorationLength<L> {
+    LengthPercentage(L),
+    Auto,
+    FromFont,
+}
diff --git a/servo/components/style/values/generics/transform.rs b/servo/components/style/values/generics/transform.rs
new file mode 100644
index 0000000000..6d8115005d
--- /dev/null
+++ b/servo/components/style/values/generics/transform.rs
@@ -0,0 +1,883 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for CSS values that are related to transformations.
+
+use crate::values::computed::length::Length as ComputedLength;
+use crate::values::computed::length::LengthPercentage as ComputedLengthPercentage;
+use crate::values::specified::angle::Angle as SpecifiedAngle;
+use crate::values::specified::length::Length as SpecifiedLength;
+use crate::values::specified::length::LengthPercentage as SpecifiedLengthPercentage;
+use crate::values::{computed, CSSFloat};
+use crate::{Zero, ZeroNoPercent};
+use euclid;
+use euclid::default::{Rect, Transform3D};
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// A generic 2D transformation matrix.
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma, function = "matrix")]
+#[repr(C)]
+pub struct GenericMatrix<T> {
+    pub a: T,
+    pub b: T,
+    pub c: T,
+    pub d: T,
+    pub e: T,
+    pub f: T,
+}
+
+pub use self::GenericMatrix as Matrix;
+
+#[allow(missing_docs)]
+#[cfg_attr(rustfmt, rustfmt_skip)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma, function = "matrix3d")]
+#[repr(C)]
+pub struct GenericMatrix3D<T> {
+    pub m11: T, pub m12: T, pub m13: T, pub m14: T,
+    pub m21: T, pub m22: T, pub m23: T, pub m24: T,
+    pub m31: T, pub m32: T, pub m33: T, pub m34: T,
+    pub m41: T, pub m42: T, pub m43: T, pub m44: T,
+}
+
+pub use self::GenericMatrix3D as Matrix3D;
+
+#[cfg_attr(rustfmt, rustfmt_skip)]
+impl<T: Into<f64>> From<Matrix<T>> for Transform3D<f64> {
+    #[inline]
+    fn from(m: Matrix<T>) -> Self {
+        Transform3D::new(
+            m.a.into(), m.b.into(), 0.0, 0.0,
+            m.c.into(), m.d.into(), 0.0, 0.0,
+            0.0,        0.0,        1.0, 0.0,
+            m.e.into(), m.f.into(), 0.0, 1.0,
+        )
+    }
+}
+
+#[cfg_attr(rustfmt, rustfmt_skip)]
+impl<T: Into<f64>> From<Matrix3D<T>> for Transform3D<f64> {
+    #[inline]
+    fn from(m: Matrix3D<T>) -> Self {
+        Transform3D::new(
+            m.m11.into(), m.m12.into(), m.m13.into(), m.m14.into(),
+            m.m21.into(), m.m22.into(), m.m23.into(), m.m24.into(),
+            m.m31.into(), m.m32.into(), m.m33.into(), m.m34.into(),
+            m.m41.into(), m.m42.into(), m.m43.into(), m.m44.into(),
+        )
+    }
+}
+
+/// A generic transform origin.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericTransformOrigin<H, V, Depth> {
+    /// The horizontal origin.
+    pub horizontal: H,
+    /// The vertical origin.
+    pub vertical: V,
+    /// The depth.
+    pub depth: Depth,
+}
+
+pub use self::GenericTransformOrigin as TransformOrigin;
+
+impl<H, V, D> TransformOrigin<H, V, D> {
+    /// Returns a new transform origin.
+    pub fn new(horizontal: H, vertical: V, depth: D) -> Self {
+        Self {
+            horizontal,
+            vertical,
+            depth,
+        }
+    }
+}
+
+fn is_same<N: PartialEq>(x: &N, y: &N) -> bool {
+    x == y
+}
+
+/// A value for the `perspective()` transform function, which is either a
+/// non-negative `<length>` or `none`.
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericPerspectiveFunction<L> {
+    /// `none`
+    None,
+    /// A `<length>`.
+    Length(L),
+}
+
+impl<L> GenericPerspectiveFunction<L> {
+    /// Returns `f32::INFINITY` or the result of a function on the length value.
+    pub fn infinity_or(&self, f: impl FnOnce(&L) -> f32) -> f32 {
+        match *self {
+            Self::None => std::f32::INFINITY,
+            Self::Length(ref l) => f(l),
+        }
+    }
+}
+
+pub use self::GenericPerspectiveFunction as PerspectiveFunction;
+
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+/// A single operation in the list of a `transform` value
+pub enum GenericTransformOperation<Angle, Number, Length, Integer, LengthPercentage>
+where
+    Angle: Zero,
+    LengthPercentage: Zero + ZeroNoPercent,
+    Number: PartialEq,
+{
+    /// Represents a 2D 2x3 matrix.
+    Matrix(GenericMatrix<Number>),
+    /// Represents a 3D 4x4 matrix.
+    Matrix3D(GenericMatrix3D<Number>),
+    /// A 2D skew.
+    ///
+    /// If the second angle is not provided it is assumed zero.
+    ///
+    /// Syntax can be skew(angle) or skew(angle, angle)
+    #[css(comma, function)]
+    Skew(Angle, #[css(skip_if = "Zero::is_zero")] Angle),
+    /// skewX(angle)
+    #[css(function = "skewX")]
+    SkewX(Angle),
+    /// skewY(angle)
+    #[css(function = "skewY")]
+    SkewY(Angle),
+    /// translate(x, y) or translate(x)
+    #[css(comma, function)]
+    Translate(
+        LengthPercentage,
+        #[css(skip_if = "ZeroNoPercent::is_zero_no_percent")] LengthPercentage,
+    ),
+    /// translateX(x)
+    #[css(function = "translateX")]
+    TranslateX(LengthPercentage),
+    /// translateY(y)
+    #[css(function = "translateY")]
+    TranslateY(LengthPercentage),
+    /// translateZ(z)
+    #[css(function = "translateZ")]
+    TranslateZ(Length),
+    /// translate3d(x, y, z)
+    #[css(comma, function = "translate3d")]
+    Translate3D(LengthPercentage, LengthPercentage, Length),
+    /// A 2D scaling factor.
+    ///
+    /// Syntax can be scale(factor) or scale(factor, factor)
+    #[css(comma, function)]
+    Scale(Number, #[css(contextual_skip_if = "is_same")] Number),
+    /// scaleX(factor)
+    #[css(function = "scaleX")]
+    ScaleX(Number),
+    /// scaleY(factor)
+    #[css(function = "scaleY")]
+    ScaleY(Number),
+    /// scaleZ(factor)
+    #[css(function = "scaleZ")]
+    ScaleZ(Number),
+    /// scale3D(factorX, factorY, factorZ)
+    #[css(comma, function = "scale3d")]
+    Scale3D(Number, Number, Number),
+    /// Describes a 2D Rotation.
+    ///
+    /// In a 3D scene `rotate(angle)` is equivalent to `rotateZ(angle)`.
+    #[css(function)]
+    Rotate(Angle),
+    /// Rotation in 3D space around the x-axis.
+    #[css(function = "rotateX")]
+    RotateX(Angle),
+    /// Rotation in 3D space around the y-axis.
+    #[css(function = "rotateY")]
+    RotateY(Angle),
+    /// Rotation in 3D space around the z-axis.
+    #[css(function = "rotateZ")]
+    RotateZ(Angle),
+    /// Rotation in 3D space.
+    ///
+    /// Generalization of rotateX, rotateY and rotateZ.
+    #[css(comma, function = "rotate3d")]
+    Rotate3D(Number, Number, Number, Angle),
+    /// Specifies a perspective projection matrix.
+    ///
+    /// Part of CSS Transform Module Level 2 and defined at
+    /// [§ 13.1. 3D Transform Function](https://drafts.csswg.org/css-transforms-2/#funcdef-perspective).
+    ///
+    /// The value must be greater than or equal to zero.
+    #[css(function)]
+    Perspective(GenericPerspectiveFunction<Length>),
+    /// A intermediate type for interpolation of mismatched transform lists.
+    #[allow(missing_docs)]
+    #[css(comma, function = "interpolatematrix")]
+    InterpolateMatrix {
+        from_list: GenericTransform<
+            GenericTransformOperation<Angle, Number, Length, Integer, LengthPercentage>,
+        >,
+        to_list: GenericTransform<
+            GenericTransformOperation<Angle, Number, Length, Integer, LengthPercentage>,
+        >,
+        progress: computed::Percentage,
+    },
+    /// A intermediate type for accumulation of mismatched transform lists.
+    #[allow(missing_docs)]
+    #[css(comma, function = "accumulatematrix")]
+    AccumulateMatrix {
+        from_list: GenericTransform<
+            GenericTransformOperation<Angle, Number, Length, Integer, LengthPercentage>,
+        >,
+        to_list: GenericTransform<
+            GenericTransformOperation<Angle, Number, Length, Integer, LengthPercentage>,
+        >,
+        count: Integer,
+    },
+}
+
+pub use self::GenericTransformOperation as TransformOperation;
+
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// A value of the `transform` property
+pub struct GenericTransform<T>(#[css(if_empty = "none", iterable)] pub crate::OwnedSlice<T>);
+
+pub use self::GenericTransform as Transform;
+
+impl<Angle, Number, Length, Integer, LengthPercentage>
+    TransformOperation<Angle, Number, Length, Integer, LengthPercentage>
+where
+    Angle: Zero,
+    LengthPercentage: Zero + ZeroNoPercent,
+    Number: PartialEq,
+{
+    /// Check if it is any rotate function.
+    pub fn is_rotate(&self) -> bool {
+        use self::TransformOperation::*;
+        matches!(
+            *self,
+            Rotate(..) | Rotate3D(..) | RotateX(..) | RotateY(..) | RotateZ(..)
+        )
+    }
+
+    /// Check if it is any translate function
+    pub fn is_translate(&self) -> bool {
+        use self::TransformOperation::*;
+        match *self {
+            Translate(..) | Translate3D(..) | TranslateX(..) | TranslateY(..) | TranslateZ(..) => {
+                true
+            },
+            _ => false,
+        }
+    }
+
+    /// Check if it is any scale function
+    pub fn is_scale(&self) -> bool {
+        use self::TransformOperation::*;
+        match *self {
+            Scale(..) | Scale3D(..) | ScaleX(..) | ScaleY(..) | ScaleZ(..) => true,
+            _ => false,
+        }
+    }
+}
+
+/// Convert a length type into the absolute lengths.
+pub trait ToAbsoluteLength {
+    /// Returns the absolute length as pixel value.
+    fn to_pixel_length(&self, containing_len: Option<ComputedLength>) -> Result<CSSFloat, ()>;
+}
+
+impl ToAbsoluteLength for SpecifiedLength {
+    // This returns Err(()) if there is any relative length or percentage. We use this when
+    // parsing a transform list of DOMMatrix because we want to return a DOM Exception
+    // if there is relative length.
+    #[inline]
+    fn to_pixel_length(&self, _containing_len: Option<ComputedLength>) -> Result<CSSFloat, ()> {
+        match *self {
+            SpecifiedLength::NoCalc(len) => len.to_computed_pixel_length_without_context(),
+            SpecifiedLength::Calc(ref calc) => calc.to_computed_pixel_length_without_context(),
+        }
+    }
+}
+
+impl ToAbsoluteLength for SpecifiedLengthPercentage {
+    // This returns Err(()) if there is any relative length or percentage. We use this when
+    // parsing a transform list of DOMMatrix because we want to return a DOM Exception
+    // if there is relative length.
+    #[inline]
+    fn to_pixel_length(&self, _containing_len: Option<ComputedLength>) -> Result<CSSFloat, ()> {
+        use self::SpecifiedLengthPercentage::*;
+        match *self {
+            Length(len) => len.to_computed_pixel_length_without_context(),
+            Calc(ref calc) => calc.to_computed_pixel_length_without_context(),
+            Percentage(..) => Err(()),
+        }
+    }
+}
+
+impl ToAbsoluteLength for ComputedLength {
+    #[inline]
+    fn to_pixel_length(&self, _containing_len: Option<ComputedLength>) -> Result<CSSFloat, ()> {
+        Ok(self.px())
+    }
+}
+
+impl ToAbsoluteLength for ComputedLengthPercentage {
+    #[inline]
+    fn to_pixel_length(&self, containing_len: Option<ComputedLength>) -> Result<CSSFloat, ()> {
+        Ok(self
+            .maybe_percentage_relative_to(containing_len)
+            .ok_or(())?
+            .px())
+    }
+}
+
+/// Support the conversion to a 3d matrix.
+pub trait ToMatrix {
+    /// Check if it is a 3d transform function.
+    fn is_3d(&self) -> bool;
+
+    /// Return the equivalent 3d matrix.
+    fn to_3d_matrix(
+        &self,
+        reference_box: Option<&Rect<ComputedLength>>,
+    ) -> Result<Transform3D<f64>, ()>;
+}
+
+/// A little helper to deal with both specified and computed angles.
+pub trait ToRadians {
+    /// Return the radians value as a 64-bit floating point value.
+    fn radians64(&self) -> f64;
+}
+
+impl ToRadians for computed::angle::Angle {
+    #[inline]
+    fn radians64(&self) -> f64 {
+        computed::angle::Angle::radians64(self)
+    }
+}
+
+impl ToRadians for SpecifiedAngle {
+    #[inline]
+    fn radians64(&self) -> f64 {
+        computed::angle::Angle::from_degrees(self.degrees()).radians64()
+    }
+}
+
+impl<Angle, Number, Length, Integer, LoP> ToMatrix
+    for TransformOperation<Angle, Number, Length, Integer, LoP>
+where
+    Angle: Zero + ToRadians + Copy,
+    Number: PartialEq + Copy + Into<f32> + Into<f64>,
+    Length: ToAbsoluteLength,
+    LoP: Zero + ToAbsoluteLength + ZeroNoPercent,
+{
+    #[inline]
+    fn is_3d(&self) -> bool {
+        use self::TransformOperation::*;
+        match *self {
+            Translate3D(..) | TranslateZ(..) | Rotate3D(..) | RotateX(..) | RotateY(..) |
+            RotateZ(..) | Scale3D(..) | ScaleZ(..) | Perspective(..) | Matrix3D(..) => true,
+            _ => false,
+        }
+    }
+
+    /// If |reference_box| is None, we will drop the percent part from translate because
+    /// we cannot resolve it without the layout info, for computed TransformOperation.
+    /// However, for specified TransformOperation, we will return Err(()) if there is any relative
+    /// lengths because the only caller, DOMMatrix, doesn't accept relative lengths.
+    #[inline]
+    fn to_3d_matrix(
+        &self,
+        reference_box: Option<&Rect<ComputedLength>>,
+    ) -> Result<Transform3D<f64>, ()> {
+        use self::TransformOperation::*;
+        use std::f64;
+
+        let reference_width = reference_box.map(|v| v.size.width);
+        let reference_height = reference_box.map(|v| v.size.height);
+        let matrix = match *self {
+            Rotate3D(ax, ay, az, theta) => {
+                let theta = theta.radians64();
+                let (ax, ay, az, theta) =
+                    get_normalized_vector_and_angle(ax.into(), ay.into(), az.into(), theta);
+                Transform3D::rotation(
+                    ax as f64,
+                    ay as f64,
+                    az as f64,
+                    euclid::Angle::radians(theta),
+                )
+            },
+            RotateX(theta) => {
+                let theta = euclid::Angle::radians(theta.radians64());
+                Transform3D::rotation(1., 0., 0., theta)
+            },
+            RotateY(theta) => {
+                let theta = euclid::Angle::radians(theta.radians64());
+                Transform3D::rotation(0., 1., 0., theta)
+            },
+            RotateZ(theta) | Rotate(theta) => {
+                let theta = euclid::Angle::radians(theta.radians64());
+                Transform3D::rotation(0., 0., 1., theta)
+            },
+            Perspective(ref p) => {
+                let px = match p {
+                    PerspectiveFunction::None => std::f32::INFINITY,
+                    PerspectiveFunction::Length(ref p) => p.to_pixel_length(None)?,
+                };
+                create_perspective_matrix(px).cast()
+            },
+            Scale3D(sx, sy, sz) => Transform3D::scale(sx.into(), sy.into(), sz.into()),
+            Scale(sx, sy) => Transform3D::scale(sx.into(), sy.into(), 1.),
+            ScaleX(s) => Transform3D::scale(s.into(), 1., 1.),
+            ScaleY(s) => Transform3D::scale(1., s.into(), 1.),
+            ScaleZ(s) => Transform3D::scale(1., 1., s.into()),
+            Translate3D(ref tx, ref ty, ref tz) => {
+                let tx = tx.to_pixel_length(reference_width)? as f64;
+                let ty = ty.to_pixel_length(reference_height)? as f64;
+                Transform3D::translation(tx, ty, tz.to_pixel_length(None)? as f64)
+            },
+            Translate(ref tx, ref ty) => {
+                let tx = tx.to_pixel_length(reference_width)? as f64;
+                let ty = ty.to_pixel_length(reference_height)? as f64;
+                Transform3D::translation(tx, ty, 0.)
+            },
+            TranslateX(ref t) => {
+                let t = t.to_pixel_length(reference_width)? as f64;
+                Transform3D::translation(t, 0., 0.)
+            },
+            TranslateY(ref t) => {
+                let t = t.to_pixel_length(reference_height)? as f64;
+                Transform3D::translation(0., t, 0.)
+            },
+            TranslateZ(ref z) => Transform3D::translation(0., 0., z.to_pixel_length(None)? as f64),
+            Skew(theta_x, theta_y) => Transform3D::skew(
+                euclid::Angle::radians(theta_x.radians64()),
+                euclid::Angle::radians(theta_y.radians64()),
+            ),
+            SkewX(theta) => Transform3D::skew(
+                euclid::Angle::radians(theta.radians64()),
+                euclid::Angle::radians(0.),
+            ),
+            SkewY(theta) => Transform3D::skew(
+                euclid::Angle::radians(0.),
+                euclid::Angle::radians(theta.radians64()),
+            ),
+            Matrix3D(m) => m.into(),
+            Matrix(m) => m.into(),
+            InterpolateMatrix { .. } | AccumulateMatrix { .. } => {
+                // TODO: Convert InterpolateMatrix/AccumulateMatrix into a valid Transform3D by
+                // the reference box and do interpolation on these two Transform3D matrices.
+                // Both Gecko and Servo don't support this for computing distance, and Servo
+                // doesn't support animations on InterpolateMatrix/AccumulateMatrix, so
+                // return an identity matrix.
+                // Note: DOMMatrix doesn't go into this arm.
+                Transform3D::identity()
+            },
+        };
+        Ok(matrix)
+    }
+}
+
+impl<T> Transform<T> {
+    /// `none`
+    pub fn none() -> Self {
+        Transform(Default::default())
+    }
+}
+
+impl<T: ToMatrix> Transform<T> {
+    /// Return the equivalent 3d matrix of this transform list.
+    ///
+    /// We return a pair: the first one is the transform matrix, and the second one
+    /// indicates if there is any 3d transform function in this transform list.
+    #[cfg_attr(rustfmt, rustfmt_skip)]
+    pub fn to_transform_3d_matrix(
+        &self,
+        reference_box: Option<&Rect<ComputedLength>>
+    ) -> Result<(Transform3D<CSSFloat>, bool), ()> {
+        Self::components_to_transform_3d_matrix(&self.0, reference_box)
+    }
+
+    /// Converts a series of components to a 3d matrix.
+    #[cfg_attr(rustfmt, rustfmt_skip)]
+    pub fn components_to_transform_3d_matrix(
+        ops: &[T],
+        reference_box: Option<&Rect<ComputedLength>>,
+    ) -> Result<(Transform3D<CSSFloat>, bool), ()> {
+        let cast_3d_transform = |m: Transform3D<f64>| -> Transform3D<CSSFloat> {
+            use std::{f32, f64};
+            let cast = |v: f64| v.min(f32::MAX as f64).max(f32::MIN as f64) as f32;
+            Transform3D::new(
+                cast(m.m11), cast(m.m12), cast(m.m13), cast(m.m14),
+                cast(m.m21), cast(m.m22), cast(m.m23), cast(m.m24),
+                cast(m.m31), cast(m.m32), cast(m.m33), cast(m.m34),
+                cast(m.m41), cast(m.m42), cast(m.m43), cast(m.m44),
+            )
+        };
+
+        let (m, is_3d) = Self::components_to_transform_3d_matrix_f64(ops, reference_box)?;
+        Ok((cast_3d_transform(m), is_3d))
+    }
+
+    /// Same as Transform::to_transform_3d_matrix but a f64 version.
+    fn components_to_transform_3d_matrix_f64(
+        ops: &[T],
+        reference_box: Option<&Rect<ComputedLength>>,
+    ) -> Result<(Transform3D<f64>, bool), ()> {
+        // We intentionally use Transform3D<f64> during computation to avoid
+        // error propagation because using f32 to compute triangle functions
+        // (e.g. in rotation()) is not accurate enough. In Gecko, we also use
+        // "double" to compute the triangle functions. Therefore, let's use
+        // Transform3D<f64> during matrix computation and cast it into f32 in
+        // the end.
+        let mut transform = Transform3D::<f64>::identity();
+        let mut contain_3d = false;
+
+        for operation in ops {
+            let matrix = operation.to_3d_matrix(reference_box)?;
+            contain_3d = contain_3d || operation.is_3d();
+            transform = matrix.then(&transform);
+        }
+
+        Ok((transform, contain_3d))
+    }
+}
+
+/// Return the transform matrix from a perspective length.
+#[inline]
+pub fn create_perspective_matrix(d: CSSFloat) -> Transform3D<CSSFloat> {
+    if d.is_finite() {
+        Transform3D::perspective(d.max(1.))
+    } else {
+        Transform3D::identity()
+    }
+}
+
+/// Return the normalized direction vector and its angle for Rotate3D.
+pub fn get_normalized_vector_and_angle<T: Zero>(
+    x: CSSFloat,
+    y: CSSFloat,
+    z: CSSFloat,
+    angle: T,
+) -> (CSSFloat, CSSFloat, CSSFloat, T) {
+    use crate::values::computed::transform::DirectionVector;
+    use euclid::approxeq::ApproxEq;
+    let vector = DirectionVector::new(x, y, z);
+    if vector.square_length().approx_eq(&f32::zero()) {
+        // https://www.w3.org/TR/css-transforms-1/#funcdef-rotate3d
+        // A direction vector that cannot be normalized, such as [0, 0, 0], will cause the
+        // rotation to not be applied, so we use identity matrix (i.e. rotate3d(0, 0, 1, 0)).
+        (0., 0., 1., T::zero())
+    } else {
+        let vector = vector.robust_normalize();
+        (vector.x, vector.y, vector.z, angle)
+    }
+}
+
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+/// A value of the `Rotate` property
+///
+/// <https://drafts.csswg.org/css-transforms-2/#individual-transforms>
+/// cbindgen:private-default-tagged-enum-constructor=false
+pub enum GenericRotate<Number, Angle> {
+    /// 'none'
+    None,
+    /// '<angle>'
+    Rotate(Angle),
+    /// '<number>{3} <angle>'
+    Rotate3D(Number, Number, Number, Angle),
+}
+
+pub use self::GenericRotate as Rotate;
+
+/// A trait to check if the current 3D vector is parallel to the DirectionVector.
+/// This is especially for serialization on Rotate.
+pub trait IsParallelTo {
+    /// Returns true if this is parallel to the vector.
+    fn is_parallel_to(&self, vector: &computed::transform::DirectionVector) -> bool;
+}
+
+impl<Number, Angle> ToCss for Rotate<Number, Angle>
+where
+    Number: Copy + ToCss + Zero,
+    Angle: ToCss,
+    (Number, Number, Number): IsParallelTo,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        use crate::values::computed::transform::DirectionVector;
+        match *self {
+            Rotate::None => dest.write_str("none"),
+            Rotate::Rotate(ref angle) => angle.to_css(dest),
+            Rotate::Rotate3D(x, y, z, ref angle) => {
+                // If the axis is parallel with the x or y axes, it must serialize as the
+                // appropriate keyword. If a rotation about the z axis (that is, in 2D) is
+                // specified, the property must serialize as just an <angle>
+                //
+                // https://drafts.csswg.org/css-transforms-2/#individual-transform-serialization
+                let v = (x, y, z);
+                let axis = if x.is_zero() && y.is_zero() && z.is_zero() {
+                    // The zero length vector is parallel to every other vector, so
+                    // is_parallel_to() returns true for it. However, it is definitely different
+                    // from x axis, y axis, or z axis, and it's meaningless to perform a rotation
+                    // using that direction vector. So we *have* to serialize it using that same
+                    // vector - we can't simplify to some theoretically parallel axis-aligned
+                    // vector.
+                    None
+                } else if v.is_parallel_to(&DirectionVector::new(1., 0., 0.)) {
+                    Some("x ")
+                } else if v.is_parallel_to(&DirectionVector::new(0., 1., 0.)) {
+                    Some("y ")
+                } else if v.is_parallel_to(&DirectionVector::new(0., 0., 1.)) {
+                    // When we're parallel to the z-axis, we can just serialize the angle.
+                    return angle.to_css(dest);
+                } else {
+                    None
+                };
+                match axis {
+                    Some(a) => dest.write_str(a)?,
+                    None => {
+                        x.to_css(dest)?;
+                        dest.write_char(' ')?;
+                        y.to_css(dest)?;
+                        dest.write_char(' ')?;
+                        z.to_css(dest)?;
+                        dest.write_char(' ')?;
+                    },
+                }
+                angle.to_css(dest)
+            },
+        }
+    }
+}
+
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+/// A value of the `Scale` property
+///
+/// <https://drafts.csswg.org/css-transforms-2/#individual-transforms>
+/// cbindgen:private-default-tagged-enum-constructor=false
+pub enum GenericScale<Number> {
+    /// 'none'
+    None,
+    /// '<number>{1,3}'
+    Scale(Number, Number, Number),
+}
+
+pub use self::GenericScale as Scale;
+
+impl<Number> ToCss for Scale<Number>
+where
+    Number: ToCss + PartialEq + Copy,
+    f32: From<Number>,
+{
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+        f32: From<Number>,
+    {
+        match *self {
+            Scale::None => dest.write_str("none"),
+            Scale::Scale(ref x, ref y, ref z) => {
+                x.to_css(dest)?;
+
+                let is_3d = f32::from(*z) != 1.0;
+                if is_3d || x != y {
+                    dest.write_char(' ')?;
+                    y.to_css(dest)?;
+                }
+
+                if is_3d {
+                    dest.write_char(' ')?;
+                    z.to_css(dest)?;
+                }
+                Ok(())
+            },
+        }
+    }
+}
+
+#[inline]
+fn y_axis_and_z_axis_are_zero<LengthPercentage: Zero + ZeroNoPercent, Length: Zero>(
+    _: &LengthPercentage,
+    y: &LengthPercentage,
+    z: &Length,
+) -> bool {
+    y.is_zero_no_percent() && z.is_zero()
+}
+
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+/// A value of the `translate` property
+///
+/// https://drafts.csswg.org/css-transforms-2/#individual-transform-serialization:
+///
+/// If a 2d translation is specified, the property must serialize with only one
+/// or two values (per usual, if the second value is 0px, the default, it must
+/// be omitted when serializing; however if 0% is the second value, it is included).
+///
+/// If a 3d translation is specified and the value can be expressed as 2d, we treat as 2d and
+/// serialize accoringly. Otherwise, we serialize all three values.
+/// https://github.com/w3c/csswg-drafts/issues/3305
+///
+/// <https://drafts.csswg.org/css-transforms-2/#individual-transforms>
+/// cbindgen:private-default-tagged-enum-constructor=false
+pub enum GenericTranslate<LengthPercentage, Length>
+where
+    LengthPercentage: Zero + ZeroNoPercent,
+    Length: Zero,
+{
+    /// 'none'
+    None,
+    /// <length-percentage> [ <length-percentage> <length>? ]?
+    Translate(
+        LengthPercentage,
+        #[css(contextual_skip_if = "y_axis_and_z_axis_are_zero")] LengthPercentage,
+        #[css(skip_if = "Zero::is_zero")] Length,
+    ),
+}
+
+pub use self::GenericTranslate as Translate;
+
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum TransformStyle {
+    Flat,
+    #[css(keyword = "preserve-3d")]
+    Preserve3d,
+}
diff --git a/servo/components/style/values/generics/ui.rs b/servo/components/style/values/generics/ui.rs
new file mode 100644
index 0000000000..4d9515199a
--- /dev/null
+++ b/servo/components/style/values/generics/ui.rs
@@ -0,0 +1,129 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic values for UI properties.
+
+use crate::values::specified::ui::CursorKind;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ToCss};
+
+/// A generic value for the `cursor` property.
+///
+/// https://drafts.csswg.org/css-ui/#cursor
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct GenericCursor<Image> {
+    /// The parsed images for the cursor.
+    pub images: crate::OwnedSlice<Image>,
+    /// The kind of the cursor [default | help | ...].
+    pub keyword: CursorKind,
+}
+
+pub use self::GenericCursor as Cursor;
+
+impl<Image> Cursor<Image> {
+    /// Set `cursor` to `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        Self {
+            images: Default::default(),
+            keyword: CursorKind::Auto,
+        }
+    }
+}
+
+impl<Image: ToCss> ToCss for Cursor<Image> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        for image in &*self.images {
+            image.to_css(dest)?;
+            dest.write_str(", ")?;
+        }
+        self.keyword.to_css(dest)
+    }
+}
+
+/// A generic value for item of `image cursors`.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem)]
+#[repr(C)]
+pub struct GenericCursorImage<Image, Number> {
+    /// The url to parse images from.
+    pub image: Image,
+    /// Whether the image has a hotspot or not.
+    pub has_hotspot: bool,
+    /// The x coordinate.
+    pub hotspot_x: Number,
+    /// The y coordinate.
+    pub hotspot_y: Number,
+}
+
+pub use self::GenericCursorImage as CursorImage;
+
+impl<Image: ToCss, Number: ToCss> ToCss for CursorImage<Image, Number> {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.image.to_css(dest)?;
+        if self.has_hotspot {
+            dest.write_str(" ")?;
+            self.hotspot_x.to_css(dest)?;
+            dest.write_str(" ")?;
+            self.hotspot_y.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+/// A generic value for `scrollbar-color` property.
+///
+/// https://drafts.csswg.org/css-scrollbars-1/#scrollbar-color
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericScrollbarColor<Color> {
+    /// `auto`
+    Auto,
+    /// `<color>{2}`
+    Colors {
+        /// First `<color>`, for color of the scrollbar thumb.
+        thumb: Color,
+        /// Second `<color>`, for color of the scrollbar track.
+        track: Color,
+    },
+}
+
+pub use self::GenericScrollbarColor as ScrollbarColor;
+
+impl<Color> Default for ScrollbarColor<Color> {
+    #[inline]
+    fn default() -> Self {
+        ScrollbarColor::Auto
+    }
+}
diff --git a/servo/components/style/values/generics/url.rs b/servo/components/style/values/generics/url.rs
new file mode 100644
index 0000000000..46ed453e82
--- /dev/null
+++ b/servo/components/style/values/generics/url.rs
@@ -0,0 +1,47 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Generic types for url properties.
+
+/// An image url or none, used for example in list-style-image
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum GenericUrlOrNone<U> {
+    /// `none`
+    None,
+    /// A URL.
+    Url(U),
+}
+
+pub use self::GenericUrlOrNone as UrlOrNone;
+
+impl<Url> UrlOrNone<Url> {
+    /// Initial "none" value for properties such as `list-style-image`
+    pub fn none() -> Self {
+        UrlOrNone::None
+    }
+
+    /// Returns whether the value is `none`.
+    pub fn is_none(&self) -> bool {
+        match *self {
+            UrlOrNone::None => true,
+            UrlOrNone::Url(..) => false,
+        }
+    }
+}
diff --git a/servo/components/style/values/mod.rs b/servo/components/style/values/mod.rs
new file mode 100644
index 0000000000..3dd31a7587
--- /dev/null
+++ b/servo/components/style/values/mod.rs
@@ -0,0 +1,706 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Common [values][values] used in CSS.
+//!
+//! [values]: https://drafts.csswg.org/css-values/
+
+#![deny(missing_docs)]
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::Atom;
+pub use cssparser::{serialize_identifier, serialize_name, CowRcStr, Parser};
+pub use cssparser::{SourceLocation, Token, RGBA};
+use precomputed_hash::PrecomputedHash;
+use selectors::parser::SelectorParseErrorKind;
+use std::fmt::{self, Debug, Write};
+use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+use to_shmem::impl_trivial_to_shmem;
+
+#[cfg(feature = "gecko")]
+pub use crate::gecko::url::CssUrl;
+#[cfg(feature = "servo")]
+pub use crate::servo::url::CssUrl;
+
+pub mod animated;
+pub mod computed;
+pub mod distance;
+pub mod generics;
+pub mod resolved;
+pub mod specified;
+
+/// A CSS float value.
+pub type CSSFloat = f32;
+
+/// Normalizes a float value to zero after a set of operations that might turn
+/// it into NaN.
+#[inline]
+pub fn normalize(v: CSSFloat) -> CSSFloat {
+    if v.is_nan() {
+        0.0
+    } else {
+        v
+    }
+}
+
+/// A CSS integer value.
+pub type CSSInteger = i32;
+
+/// Serialize an identifier which is represented as an atom.
+#[cfg(feature = "gecko")]
+pub fn serialize_atom_identifier<W>(ident: &Atom, dest: &mut W) -> fmt::Result
+where
+    W: Write,
+{
+    ident.with_str(|s| serialize_identifier(s, dest))
+}
+
+/// Serialize an identifier which is represented as an atom.
+#[cfg(feature = "servo")]
+pub fn serialize_atom_identifier<Static, W>(
+    ident: &::string_cache::Atom<Static>,
+    dest: &mut W,
+) -> fmt::Result
+where
+    Static: string_cache::StaticAtomSet,
+    W: Write,
+{
+    serialize_identifier(&ident, dest)
+}
+
+/// Serialize a name which is represented as an Atom.
+#[cfg(feature = "gecko")]
+pub fn serialize_atom_name<W>(ident: &Atom, dest: &mut W) -> fmt::Result
+where
+    W: Write,
+{
+    ident.with_str(|s| serialize_name(s, dest))
+}
+
+/// Serialize a name which is represented as an Atom.
+#[cfg(feature = "servo")]
+pub fn serialize_atom_name<Static, W>(
+    ident: &::string_cache::Atom<Static>,
+    dest: &mut W,
+) -> fmt::Result
+where
+    Static: string_cache::StaticAtomSet,
+    W: Write,
+{
+    serialize_name(&ident, dest)
+}
+
+/// A CSS string stored as an `Atom`.
+#[repr(transparent)]
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    Deref,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct AtomString(pub Atom);
+
+#[cfg(feature = "servo")]
+impl AsRef<str> for AtomString {
+    fn as_ref(&self) -> &str {
+        &*self.0
+    }
+}
+
+impl cssparser::ToCss for AtomString {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
+    where
+        W: Write,
+    {
+        #[cfg(feature = "servo")]
+        {
+            cssparser::CssStringWriter::new(dest).write_str(self.as_ref())
+        }
+        #[cfg(feature = "gecko")]
+        {
+            self.0
+                .with_str(|s| cssparser::CssStringWriter::new(dest).write_str(s))
+        }
+    }
+}
+
+impl PrecomputedHash for AtomString {
+    #[inline]
+    fn precomputed_hash(&self) -> u32 {
+        self.0.precomputed_hash()
+    }
+}
+
+impl<'a> From<&'a str> for AtomString {
+    #[inline]
+    fn from(string: &str) -> Self {
+        Self(Atom::from(string))
+    }
+}
+
+/// A generic CSS `<ident>` stored as an `Atom`.
+#[cfg(feature = "servo")]
+#[repr(transparent)]
+#[derive(Deref)]
+pub struct GenericAtomIdent<Set>(pub string_cache::Atom<Set>)
+where
+    Set: string_cache::StaticAtomSet;
+
+/// A generic CSS `<ident>` stored as an `Atom`, for the default atom set.
+#[cfg(feature = "servo")]
+pub type AtomIdent = GenericAtomIdent<servo_atoms::AtomStaticSet>;
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> style_traits::SpecifiedValueInfo for GenericAtomIdent<Set> {}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> Default for GenericAtomIdent<Set> {
+    fn default() -> Self {
+        Self(string_cache::Atom::default())
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> std::fmt::Debug for GenericAtomIdent<Set> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> std::hash::Hash for GenericAtomIdent<Set> {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.0.hash(state)
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> Eq for GenericAtomIdent<Set> {}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> PartialEq for GenericAtomIdent<Set> {
+    fn eq(&self, other: &Self) -> bool {
+        self.0 == other.0
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> Clone for GenericAtomIdent<Set> {
+    fn clone(&self) -> Self {
+        Self(self.0.clone())
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> to_shmem::ToShmem for GenericAtomIdent<Set> {
+    fn to_shmem(&self, builder: &mut to_shmem::SharedMemoryBuilder) -> to_shmem::Result<Self> {
+        use std::mem::ManuallyDrop;
+
+        let atom = self.0.to_shmem(builder)?;
+        Ok(ManuallyDrop::new(Self(ManuallyDrop::into_inner(atom))))
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> malloc_size_of::MallocSizeOf for GenericAtomIdent<Set> {
+    fn size_of(&self, ops: &mut malloc_size_of::MallocSizeOfOps) -> usize {
+        self.0.size_of(ops)
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> cssparser::ToCss for GenericAtomIdent<Set> {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
+    where
+        W: Write,
+    {
+        serialize_atom_identifier(&self.0, dest)
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> PrecomputedHash for GenericAtomIdent<Set> {
+    #[inline]
+    fn precomputed_hash(&self) -> u32 {
+        self.0.precomputed_hash()
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<'a, Set: string_cache::StaticAtomSet> From<&'a str> for GenericAtomIdent<Set> {
+    #[inline]
+    fn from(string: &str) -> Self {
+        Self(string_cache::Atom::from(string))
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> std::borrow::Borrow<string_cache::Atom<Set>>
+    for GenericAtomIdent<Set>
+{
+    #[inline]
+    fn borrow(&self) -> &string_cache::Atom<Set> {
+        &self.0
+    }
+}
+
+#[cfg(feature = "servo")]
+impl<Set: string_cache::StaticAtomSet> GenericAtomIdent<Set> {
+    /// Constructs a new GenericAtomIdent.
+    #[inline]
+    pub fn new(atom: string_cache::Atom<Set>) -> Self {
+        Self(atom)
+    }
+
+    /// Cast an atom ref to an AtomIdent ref.
+    #[inline]
+    pub fn cast<'a>(atom: &'a string_cache::Atom<Set>) -> &'a Self {
+        let ptr = atom as *const _ as *const Self;
+        // safety: repr(transparent)
+        unsafe { &*ptr }
+    }
+}
+
+/// A CSS `<ident>` stored as an `Atom`.
+#[cfg(feature = "gecko")]
+#[repr(transparent)]
+#[derive(
+    Clone, Debug, Default, Deref, Eq, Hash, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToShmem,
+)]
+pub struct AtomIdent(pub Atom);
+
+#[cfg(feature = "gecko")]
+impl cssparser::ToCss for AtomIdent {
+    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
+    where
+        W: Write,
+    {
+        serialize_atom_identifier(&self.0, dest)
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl style_traits::ToCss for AtomIdent {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        cssparser::ToCss::to_css(self, dest)
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl PrecomputedHash for AtomIdent {
+    #[inline]
+    fn precomputed_hash(&self) -> u32 {
+        self.0.precomputed_hash()
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl<'a> From<&'a str> for AtomIdent {
+    #[inline]
+    fn from(string: &str) -> Self {
+        Self(Atom::from(string))
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl AtomIdent {
+    /// Constructs a new AtomIdent.
+    #[inline]
+    pub fn new(atom: Atom) -> Self {
+        Self(atom)
+    }
+
+    /// Like `Atom::with` but for `AtomIdent`.
+    pub unsafe fn with<F, R>(ptr: *const crate::gecko_bindings::structs::nsAtom, callback: F) -> R
+    where
+        F: FnOnce(&Self) -> R,
+    {
+        Atom::with(ptr, |atom: &Atom| {
+            // safety: repr(transparent)
+            let atom = atom as *const Atom as *const AtomIdent;
+            callback(&*atom)
+        })
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl std::borrow::Borrow<crate::gecko_string_cache::WeakAtom> for AtomIdent {
+    #[inline]
+    fn borrow(&self) -> &crate::gecko_string_cache::WeakAtom {
+        self.0.borrow()
+    }
+}
+
+/// Serialize a normalized value into percentage.
+pub fn serialize_percentage<W>(value: CSSFloat, dest: &mut CssWriter<W>) -> fmt::Result
+where
+    W: Write,
+{
+    (value * 100.).to_css(dest)?;
+    dest.write_str("%")
+}
+
+/// Convenience void type to disable some properties and values through types.
+#[cfg_attr(feature = "servo", derive(Deserialize, MallocSizeOf, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+)]
+pub enum Impossible {}
+
+// FIXME(nox): This should be derived but the derive code cannot cope
+// with uninhabited enums.
+impl ComputeSquaredDistance for Impossible {
+    #[inline]
+    fn compute_squared_distance(&self, _other: &Self) -> Result<SquaredDistance, ()> {
+        match *self {}
+    }
+}
+
+impl_trivial_to_shmem!(Impossible);
+
+impl Parse for Impossible {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+/// A struct representing one of two kinds of values.
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum Either<A, B> {
+    /// The first value.
+    First(A),
+    /// The second kind of value.
+    Second(B),
+}
+
+impl<A: Debug, B: Debug> Debug for Either<A, B> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Either::First(ref v) => v.fmt(f),
+            Either::Second(ref v) => v.fmt(f),
+        }
+    }
+}
+
+/// <https://drafts.csswg.org/css-values-4/#custom-idents>
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct CustomIdent(pub Atom);
+
+impl CustomIdent {
+    /// Parse an already-tokenizer identifier
+    pub fn from_ident<'i>(
+        location: SourceLocation,
+        ident: &CowRcStr<'i>,
+        excluding: &[&str],
+    ) -> Result<Self, ParseError<'i>> {
+        if !Self::is_valid(ident, excluding) {
+            return Err(
+                location.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone()))
+            );
+        }
+        if excluding.iter().any(|s| ident.eq_ignore_ascii_case(s)) {
+            Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        } else {
+            Ok(CustomIdent(Atom::from(ident.as_ref())))
+        }
+    }
+
+    fn is_valid(ident: &str, excluding: &[&str]) -> bool {
+        use crate::properties::CSSWideKeyword;
+        // https://drafts.csswg.org/css-values-4/#custom-idents:
+        //
+        //     The CSS-wide keywords are not valid <custom-ident>s. The default
+        //     keyword is reserved and is also not a valid <custom-ident>.
+        if CSSWideKeyword::from_ident(ident).is_ok() || ident.eq_ignore_ascii_case("default") {
+            return false;
+        }
+
+        // https://drafts.csswg.org/css-values-4/#custom-idents:
+        //
+        //     Excluded keywords are excluded in all ASCII case permutations.
+        !excluding.iter().any(|s| ident.eq_ignore_ascii_case(s))
+    }
+}
+
+impl ToCss for CustomIdent {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        serialize_atom_identifier(&self.0, dest)
+    }
+}
+
+/// <https://www.w3.org/TR/css-values-4/#dashed-idents>
+/// This is simply an Atom, but will only parse if the identifier starts with "--".
+#[repr(transparent)]
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct DashedIdent(pub Atom);
+
+impl Parse for DashedIdent {
+    fn parse<'i, 't>(_: &ParserContext, input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let ident = input.expect_ident()?;
+        if ident.starts_with("--") {
+            Ok(Self(Atom::from(ident.as_ref())))
+        } else {
+            Err(location.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())))
+        }
+    }
+}
+
+impl ToCss for DashedIdent {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        serialize_atom_identifier(&self.0, dest)
+    }
+}
+
+/// The <timeline-name> or <keyframes-name>.
+/// The definition of these two names are the same, so we use the same type for them.
+///
+/// <https://drafts.csswg.org/css-animations-2/#typedef-timeline-name>
+/// <https://drafts.csswg.org/css-animations/#typedef-keyframes-name>
+///
+/// We use a single atom for these. Empty atom represents `none` animation.
+#[repr(transparent)]
+#[derive(
+    Clone,
+    Debug,
+    Hash,
+    PartialEq,
+    MallocSizeOf,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct TimelineOrKeyframesName(Atom);
+
+impl TimelineOrKeyframesName {
+    /// <https://drafts.csswg.org/css-animations/#dom-csskeyframesrule-name>
+    pub fn from_ident(value: &str) -> Self {
+        Self(Atom::from(value))
+    }
+
+    /// Returns the `none` value.
+    pub fn none() -> Self {
+        Self(atom!(""))
+    }
+
+    /// Returns whether this is the special `none` value.
+    pub fn is_none(&self) -> bool {
+        self.0 == atom!("")
+    }
+
+    /// Create a new TimelineOrKeyframesName from Atom.
+    #[cfg(feature = "gecko")]
+    pub fn from_atom(atom: Atom) -> Self {
+        Self(atom)
+    }
+
+    /// The name as an Atom
+    pub fn as_atom(&self) -> &Atom {
+        &self.0
+    }
+
+    fn parse<'i, 't>(input: &mut Parser<'i, 't>, invalid: &[&str]) -> Result<Self, ParseError<'i>> {
+        debug_assert!(invalid.contains(&"none"));
+        let location = input.current_source_location();
+        Ok(match *input.next()? {
+            Token::Ident(ref s) => Self(CustomIdent::from_ident(location, s, invalid)?.0),
+            Token::QuotedString(ref s) => Self(Atom::from(s.as_ref())),
+            ref t => return Err(location.new_unexpected_token_error(t.clone())),
+        })
+    }
+
+    fn to_css<W>(&self, dest: &mut CssWriter<W>, invalid: &[&str]) -> fmt::Result
+    where
+        W: Write,
+    {
+        debug_assert!(invalid.contains(&"none"));
+
+        if self.0 == atom!("") {
+            return dest.write_str("none");
+        }
+
+        self.0.with_str(|s| {
+            if CustomIdent::is_valid(s, invalid) {
+                serialize_identifier(s, dest)
+            } else {
+                s.to_css(dest)
+            }
+        })
+    }
+}
+
+impl Eq for TimelineOrKeyframesName {}
+
+/// A trait that returns whether a given type is the `auto` value or not. So far
+/// only needed for background-size serialization, which special-cases `auto`.
+pub trait IsAuto {
+    /// Returns whether the value is the `auto` value.
+    fn is_auto(&self) -> bool;
+}
+
+/// The typedef of <timeline-name>.
+#[repr(transparent)]
+#[derive(
+    Clone,
+    Debug,
+    Deref,
+    Hash,
+    Eq,
+    PartialEq,
+    MallocSizeOf,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct TimelineName(TimelineOrKeyframesName);
+
+impl TimelineName {
+    /// Create a new TimelineName from Atom.
+    #[cfg(feature = "gecko")]
+    pub fn from_atom(atom: Atom) -> Self {
+        Self(TimelineOrKeyframesName::from_atom(atom))
+    }
+
+    /// Returns the `none` value.
+    pub fn none() -> Self {
+        Self(TimelineOrKeyframesName::none())
+    }
+}
+
+impl Parse for TimelineName {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(Self(TimelineOrKeyframesName::parse(
+            input,
+            &["none", "auto"],
+        )?))
+    }
+}
+
+impl ToCss for TimelineName {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0.to_css(dest, &["none", "auto"])
+    }
+}
+
+/// The typedef of <keyframes-name>.
+#[derive(
+    Clone,
+    Debug,
+    Deref,
+    Hash,
+    Eq,
+    PartialEq,
+    MallocSizeOf,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct KeyframesName(TimelineOrKeyframesName);
+
+impl KeyframesName {
+    /// Create a new KeyframesName from Atom.
+    #[cfg(feature = "gecko")]
+    pub fn from_atom(atom: Atom) -> Self {
+        Self(TimelineOrKeyframesName::from_atom(atom))
+    }
+
+    /// Returns the `none` value.
+    pub fn none() -> Self {
+        Self(TimelineOrKeyframesName::none())
+    }
+}
+
+impl Parse for KeyframesName {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(Self(TimelineOrKeyframesName::parse(input, &["none"])?))
+    }
+}
+
+impl ToCss for KeyframesName {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0.to_css(dest, &["none"])
+    }
+}
diff --git a/servo/components/style/values/resolved/color.rs b/servo/components/style/values/resolved/color.rs
new file mode 100644
index 0000000000..ea912945c5
--- /dev/null
+++ b/servo/components/style/values/resolved/color.rs
@@ -0,0 +1,47 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Resolved color values.
+
+use super::{Context, ToResolvedValue};
+
+use crate::values::computed::color as computed;
+use crate::values::generics::color as generics;
+
+impl ToResolvedValue for computed::Color {
+    // A resolved color value is an rgba color, with currentcolor resolved.
+    type ResolvedValue = cssparser::RGBA;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        context.style.resolve_color(self)
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        generics::Color::rgba(resolved)
+    }
+}
+
+impl ToResolvedValue for computed::CaretColor {
+    // A resolved caret-color value is an rgba color, with auto resolving to
+    // currentcolor.
+    type ResolvedValue = cssparser::RGBA;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        let color = match self.0 {
+            generics::ColorOrAuto::Color(color) => color,
+            generics::ColorOrAuto::Auto => generics::Color::currentcolor(),
+        };
+        color.to_resolved_value(context)
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        generics::CaretColor(generics::ColorOrAuto::Color(
+            computed::Color::from_resolved_value(resolved),
+        ))
+    }
+}
diff --git a/servo/components/style/values/resolved/counters.rs b/servo/components/style/values/resolved/counters.rs
new file mode 100644
index 0000000000..c1332449ad
--- /dev/null
+++ b/servo/components/style/values/resolved/counters.rs
@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Resolved values for counter properties
+
+use super::{Context, ToResolvedValue};
+use crate::values::computed;
+
+/// https://drafts.csswg.org/css-content/#content-property
+///
+/// We implement this at resolved value time because otherwise it causes us to
+/// allocate a bunch of useless initial structs for ::before / ::after, which is
+/// a bit unfortunate.
+///
+/// Though these should be temporary, mostly, so if this causes complexity in
+/// other places, it should be fine to move to `StyleAdjuster`.
+///
+/// See https://github.com/w3c/csswg-drafts/issues/4632 for where some related
+/// issues are being discussed.
+impl ToResolvedValue for computed::Content {
+    type ResolvedValue = Self;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self {
+        let (is_pseudo, is_before_or_after, is_marker) = match context.style.pseudo() {
+            Some(ref pseudo) => (true, pseudo.is_before_or_after(), pseudo.is_marker()),
+            None => (false, false, false),
+        };
+        match self {
+            Self::Normal if is_before_or_after => Self::None,
+            // For now, make `content: none` compute to `normal` for pseudos
+            // other than ::before, ::after and ::marker, as we don't respect it.
+            // https://github.com/w3c/csswg-drafts/issues/6124
+            // Ditto for non-pseudo elements if the pref is disabled.
+            Self::None
+                if (is_pseudo && !is_before_or_after && !is_marker) ||
+                    (!is_pseudo &&
+                        !static_prefs::pref!("layout.css.element-content-none.enabled")) =>
+            {
+                Self::Normal
+            },
+            other => other,
+        }
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self) -> Self {
+        resolved
+    }
+}
diff --git a/servo/components/style/values/resolved/mod.rs b/servo/components/style/values/resolved/mod.rs
new file mode 100644
index 0000000000..a765980756
--- /dev/null
+++ b/servo/components/style/values/resolved/mod.rs
@@ -0,0 +1,264 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Resolved values. These are almost always computed values, but in some cases
+//! there are used values.
+
+use crate::properties::ComputedValues;
+use crate::ArcSlice;
+use cssparser;
+use servo_arc::Arc;
+use smallvec::SmallVec;
+
+mod color;
+mod counters;
+
+use crate::values::computed;
+
+/// Information needed to resolve a given value.
+pub struct Context<'a> {
+    /// The style we're resolving for. This is useful to resolve currentColor.
+    pub style: &'a ComputedValues,
+    // TODO(emilio): Add layout box information, and maybe property-specific
+    // information?
+}
+
+/// A trait to represent the conversion between resolved and resolved values.
+///
+/// This trait is derivable with `#[derive(ToResolvedValue)]`.
+///
+/// The deriving code assumes that if the type isn't generic, then the trait can
+/// be implemented as simple move. This means that a manual implementation with
+/// `ResolvedValue = Self` is bogus if it returns anything else than a clone.
+pub trait ToResolvedValue {
+    /// The resolved value type we're going to be converted to.
+    type ResolvedValue;
+
+    /// Convert a resolved value to a resolved value.
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue;
+
+    /// Convert a resolved value to resolved value form.
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self;
+}
+
+macro_rules! trivial_to_resolved_value {
+    ($ty:ty) => {
+        impl $crate::values::resolved::ToResolvedValue for $ty {
+            type ResolvedValue = Self;
+
+            #[inline]
+            fn to_resolved_value(self, _: &Context) -> Self {
+                self
+            }
+
+            #[inline]
+            fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+                resolved
+            }
+        }
+    };
+}
+
+trivial_to_resolved_value!(());
+trivial_to_resolved_value!(bool);
+trivial_to_resolved_value!(f32);
+trivial_to_resolved_value!(u8);
+trivial_to_resolved_value!(i8);
+trivial_to_resolved_value!(u16);
+trivial_to_resolved_value!(i16);
+trivial_to_resolved_value!(u32);
+trivial_to_resolved_value!(i32);
+trivial_to_resolved_value!(usize);
+trivial_to_resolved_value!(String);
+trivial_to_resolved_value!(Box<str>);
+trivial_to_resolved_value!(crate::OwnedStr);
+trivial_to_resolved_value!(cssparser::RGBA);
+trivial_to_resolved_value!(crate::Atom);
+trivial_to_resolved_value!(crate::values::AtomIdent);
+trivial_to_resolved_value!(app_units::Au);
+trivial_to_resolved_value!(computed::url::ComputedUrl);
+#[cfg(feature = "gecko")]
+trivial_to_resolved_value!(computed::url::ComputedImageUrl);
+#[cfg(feature = "servo")]
+trivial_to_resolved_value!(crate::Namespace);
+#[cfg(feature = "servo")]
+trivial_to_resolved_value!(crate::Prefix);
+trivial_to_resolved_value!(computed::LengthPercentage);
+trivial_to_resolved_value!(style_traits::values::specified::AllowedNumericType);
+trivial_to_resolved_value!(computed::TimingFunction);
+
+impl<A, B> ToResolvedValue for (A, B)
+where
+    A: ToResolvedValue,
+    B: ToResolvedValue,
+{
+    type ResolvedValue = (
+        <A as ToResolvedValue>::ResolvedValue,
+        <B as ToResolvedValue>::ResolvedValue,
+    );
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        (
+            self.0.to_resolved_value(context),
+            self.1.to_resolved_value(context),
+        )
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        (
+            A::from_resolved_value(resolved.0),
+            B::from_resolved_value(resolved.1),
+        )
+    }
+}
+
+impl<T> ToResolvedValue for Option<T>
+where
+    T: ToResolvedValue,
+{
+    type ResolvedValue = Option<<T as ToResolvedValue>::ResolvedValue>;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        self.map(|item| item.to_resolved_value(context))
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        resolved.map(T::from_resolved_value)
+    }
+}
+
+impl<T> ToResolvedValue for SmallVec<[T; 1]>
+where
+    T: ToResolvedValue,
+{
+    type ResolvedValue = SmallVec<[<T as ToResolvedValue>::ResolvedValue; 1]>;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        self.into_iter()
+            .map(|item| item.to_resolved_value(context))
+            .collect()
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        resolved.into_iter().map(T::from_resolved_value).collect()
+    }
+}
+
+impl<T> ToResolvedValue for Vec<T>
+where
+    T: ToResolvedValue,
+{
+    type ResolvedValue = Vec<<T as ToResolvedValue>::ResolvedValue>;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        self.into_iter()
+            .map(|item| item.to_resolved_value(context))
+            .collect()
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        resolved.into_iter().map(T::from_resolved_value).collect()
+    }
+}
+
+impl<T> ToResolvedValue for Box<T>
+where
+    T: ToResolvedValue,
+{
+    type ResolvedValue = Box<<T as ToResolvedValue>::ResolvedValue>;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        Box::new(T::to_resolved_value(*self, context))
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        Box::new(T::from_resolved_value(*resolved))
+    }
+}
+
+impl<T> ToResolvedValue for Box<[T]>
+where
+    T: ToResolvedValue,
+{
+    type ResolvedValue = Box<[<T as ToResolvedValue>::ResolvedValue]>;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        Vec::from(self)
+            .to_resolved_value(context)
+            .into_boxed_slice()
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        Vec::from_resolved_value(Vec::from(resolved)).into_boxed_slice()
+    }
+}
+
+impl<T> ToResolvedValue for crate::OwnedSlice<T>
+where
+    T: ToResolvedValue,
+{
+    type ResolvedValue = crate::OwnedSlice<<T as ToResolvedValue>::ResolvedValue>;
+
+    #[inline]
+    fn to_resolved_value(self, context: &Context) -> Self::ResolvedValue {
+        self.into_box().to_resolved_value(context).into()
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self::ResolvedValue) -> Self {
+        Self::from(Box::from_resolved_value(resolved.into_box()))
+    }
+}
+
+// NOTE(emilio): This is implementable more generically, but it's unlikely what
+// you want there, as it forces you to have an extra allocation.
+//
+// We could do that if needed, ideally with specialization for the case where
+// ResolvedValue = T. But we don't need it for now.
+impl<T> ToResolvedValue for Arc<T>
+where
+    T: ToResolvedValue<ResolvedValue = T>,
+{
+    type ResolvedValue = Self;
+
+    #[inline]
+    fn to_resolved_value(self, _: &Context) -> Self {
+        self
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self) -> Self {
+        resolved
+    }
+}
+
+// Same caveat as above applies.
+impl<T> ToResolvedValue for ArcSlice<T>
+where
+    T: ToResolvedValue<ResolvedValue = T>,
+{
+    type ResolvedValue = Self;
+
+    #[inline]
+    fn to_resolved_value(self, _: &Context) -> Self {
+        self
+    }
+
+    #[inline]
+    fn from_resolved_value(resolved: Self) -> Self {
+        resolved
+    }
+}
diff --git a/servo/components/style/values/specified/align.rs b/servo/components/style/values/specified/align.rs
new file mode 100644
index 0000000000..ebb6f63834
--- /dev/null
+++ b/servo/components/style/values/specified/align.rs
@@ -0,0 +1,817 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Values for CSS Box Alignment properties
+//!
+//! https://drafts.csswg.org/css-align/
+
+use crate::parser::{Parse, ParserContext};
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, KeywordsCollectFn, ParseError, SpecifiedValueInfo, ToCss};
+
+bitflags! {
+    /// Constants shared by multiple CSS Box Alignment properties
+    #[derive(MallocSizeOf, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[repr(C)]
+    pub struct AlignFlags: u8 {
+        // Enumeration stored in the lower 5 bits:
+        /// {align,justify}-{content,items,self}: 'auto'
+        const AUTO = 0;
+        /// 'normal'
+        const NORMAL = 1;
+        /// 'start'
+        const START = 2;
+        /// 'end'
+        const END = 3;
+        /// 'flex-start'
+        const FLEX_START = 4;
+        /// 'flex-end'
+        const FLEX_END = 5;
+        /// 'center'
+        const CENTER = 6;
+        /// 'left'
+        const LEFT = 7;
+        /// 'right'
+        const RIGHT = 8;
+        /// 'baseline'
+        const BASELINE = 9;
+        /// 'last-baseline'
+        const LAST_BASELINE = 10;
+        /// 'stretch'
+        const STRETCH = 11;
+        /// 'self-start'
+        const SELF_START = 12;
+        /// 'self-end'
+        const SELF_END = 13;
+        /// 'space-between'
+        const SPACE_BETWEEN = 14;
+        /// 'space-around'
+        const SPACE_AROUND = 15;
+        /// 'space-evenly'
+        const SPACE_EVENLY = 16;
+
+        // Additional flags stored in the upper bits:
+        /// 'legacy' (mutually exclusive w. SAFE & UNSAFE)
+        const LEGACY = 1 << 5;
+        /// 'safe'
+        const SAFE = 1 << 6;
+        /// 'unsafe' (mutually exclusive w. SAFE)
+        const UNSAFE = 1 << 7;
+
+        /// Mask for the additional flags above.
+        const FLAG_BITS = 0b11100000;
+    }
+}
+
+impl AlignFlags {
+    /// Returns the enumeration value stored in the lower 5 bits.
+    #[inline]
+    fn value(&self) -> Self {
+        *self & !AlignFlags::FLAG_BITS
+    }
+}
+
+impl ToCss for AlignFlags {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let extra_flags = *self & AlignFlags::FLAG_BITS;
+        let value = self.value();
+
+        match extra_flags {
+            AlignFlags::LEGACY => {
+                dest.write_str("legacy")?;
+                if value.is_empty() {
+                    return Ok(());
+                }
+                dest.write_char(' ')?;
+            },
+            AlignFlags::SAFE => dest.write_str("safe ")?,
+            AlignFlags::UNSAFE => dest.write_str("unsafe ")?,
+            _ => {
+                debug_assert_eq!(extra_flags, AlignFlags::empty());
+            },
+        }
+
+        dest.write_str(match value {
+            AlignFlags::AUTO => "auto",
+            AlignFlags::NORMAL => "normal",
+            AlignFlags::START => "start",
+            AlignFlags::END => "end",
+            AlignFlags::FLEX_START => "flex-start",
+            AlignFlags::FLEX_END => "flex-end",
+            AlignFlags::CENTER => "center",
+            AlignFlags::LEFT => "left",
+            AlignFlags::RIGHT => "right",
+            AlignFlags::BASELINE => "baseline",
+            AlignFlags::LAST_BASELINE => "last baseline",
+            AlignFlags::STRETCH => "stretch",
+            AlignFlags::SELF_START => "self-start",
+            AlignFlags::SELF_END => "self-end",
+            AlignFlags::SPACE_BETWEEN => "space-between",
+            AlignFlags::SPACE_AROUND => "space-around",
+            AlignFlags::SPACE_EVENLY => "space-evenly",
+            _ => unreachable!(),
+        })
+    }
+}
+
+/// An axis direction, either inline (for the `justify` properties) or block,
+/// (for the `align` properties).
+#[derive(Clone, Copy, PartialEq)]
+pub enum AxisDirection {
+    /// Block direction.
+    Block,
+    /// Inline direction.
+    Inline,
+}
+
+/// Shared value for the `align-content` and `justify-content` properties.
+///
+/// <https://drafts.csswg.org/css-align/#content-distribution>
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+pub struct ContentDistribution {
+    primary: AlignFlags,
+    // FIXME(https://github.com/w3c/csswg-drafts/issues/1002): This will need to
+    // accept fallback alignment, eventually.
+}
+
+impl ContentDistribution {
+    /// The initial value 'normal'
+    #[inline]
+    pub fn normal() -> Self {
+        Self::new(AlignFlags::NORMAL)
+    }
+
+    /// `start`
+    #[inline]
+    pub fn start() -> Self {
+        Self::new(AlignFlags::START)
+    }
+
+    /// The initial value 'normal'
+    #[inline]
+    pub fn new(primary: AlignFlags) -> Self {
+        Self { primary }
+    }
+
+    /// Returns whether this value is a <baseline-position>.
+    pub fn is_baseline_position(&self) -> bool {
+        matches!(
+            self.primary.value(),
+            AlignFlags::BASELINE | AlignFlags::LAST_BASELINE
+        )
+    }
+
+    /// The primary alignment
+    #[inline]
+    pub fn primary(self) -> AlignFlags {
+        self.primary
+    }
+
+    /// Parse a value for align-content / justify-content.
+    pub fn parse<'i, 't>(
+        input: &mut Parser<'i, 't>,
+        axis: AxisDirection,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update the `list_keywords` function below
+        //      when this function is updated.
+
+        // Try to parse normal first
+        if input
+            .try_parse(|i| i.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(ContentDistribution::normal());
+        }
+
+        // Parse <baseline-position>, but only on the block axis.
+        if axis == AxisDirection::Block {
+            if let Ok(value) = input.try_parse(parse_baseline) {
+                return Ok(ContentDistribution::new(value));
+            }
+        }
+
+        // <content-distribution>
+        if let Ok(value) = input.try_parse(parse_content_distribution) {
+            return Ok(ContentDistribution::new(value));
+        }
+
+        // <overflow-position>? <content-position>
+        let overflow_position = input
+            .try_parse(parse_overflow_position)
+            .unwrap_or(AlignFlags::empty());
+
+        let content_position = try_match_ident_ignore_ascii_case! { input,
+            "start" => AlignFlags::START,
+            "end" => AlignFlags::END,
+            "flex-start" => AlignFlags::FLEX_START,
+            "flex-end" => AlignFlags::FLEX_END,
+            "center" => AlignFlags::CENTER,
+            "left" if axis == AxisDirection::Inline => AlignFlags::LEFT,
+            "right" if axis == AxisDirection::Inline => AlignFlags::RIGHT,
+        };
+
+        Ok(ContentDistribution::new(
+            content_position | overflow_position,
+        ))
+    }
+
+    fn list_keywords(f: KeywordsCollectFn, axis: AxisDirection) {
+        f(&["normal"]);
+        if axis == AxisDirection::Block {
+            list_baseline_keywords(f);
+        }
+        list_content_distribution_keywords(f);
+        list_overflow_position_keywords(f);
+        f(&["start", "end", "flex-start", "flex-end", "center"]);
+        if axis == AxisDirection::Inline {
+            f(&["left", "right"]);
+        }
+    }
+}
+
+/// Value for the `align-content` property.
+///
+/// <https://drafts.csswg.org/css-align/#propdef-align-content>
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct AlignContent(pub ContentDistribution);
+
+impl Parse for AlignContent {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update `impl SpecifiedValueInfo` below when
+        //      this function is updated.
+        Ok(AlignContent(ContentDistribution::parse(
+            input,
+            AxisDirection::Block,
+        )?))
+    }
+}
+
+impl SpecifiedValueInfo for AlignContent {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        ContentDistribution::list_keywords(f, AxisDirection::Block);
+    }
+}
+
+/// Value for the `align-tracks` property.
+///
+/// <https://github.com/w3c/csswg-drafts/issues/4650>
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+#[css(comma)]
+pub struct AlignTracks(#[css(iterable, if_empty = "normal")] pub crate::OwnedSlice<AlignContent>);
+
+impl Parse for AlignTracks {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let values = input.parse_comma_separated(|input| AlignContent::parse(context, input))?;
+        Ok(AlignTracks(values.into()))
+    }
+}
+
+/// Value for the `justify-content` property.
+///
+/// <https://drafts.csswg.org/css-align/#propdef-justify-content>
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct JustifyContent(pub ContentDistribution);
+
+impl Parse for JustifyContent {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update `impl SpecifiedValueInfo` below when
+        //      this function is updated.
+        Ok(JustifyContent(ContentDistribution::parse(
+            input,
+            AxisDirection::Inline,
+        )?))
+    }
+}
+
+impl SpecifiedValueInfo for JustifyContent {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        ContentDistribution::list_keywords(f, AxisDirection::Inline);
+    }
+}
+/// Value for the `justify-tracks` property.
+///
+/// <https://github.com/w3c/csswg-drafts/issues/4650>
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+#[css(comma)]
+pub struct JustifyTracks(
+    #[css(iterable, if_empty = "normal")] pub crate::OwnedSlice<JustifyContent>,
+);
+
+impl Parse for JustifyTracks {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let values = input.parse_comma_separated(|input| JustifyContent::parse(context, input))?;
+        Ok(JustifyTracks(values.into()))
+    }
+}
+
+/// <https://drafts.csswg.org/css-align/#self-alignment>
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct SelfAlignment(pub AlignFlags);
+
+impl SelfAlignment {
+    /// The initial value 'auto'
+    #[inline]
+    pub fn auto() -> Self {
+        SelfAlignment(AlignFlags::AUTO)
+    }
+
+    /// Returns whether this value is valid for both axis directions.
+    pub fn is_valid_on_both_axes(&self) -> bool {
+        match self.0.value() {
+            // left | right are only allowed on the inline axis.
+            AlignFlags::LEFT | AlignFlags::RIGHT => false,
+
+            _ => true,
+        }
+    }
+
+    /// Parse a self-alignment value on one of the axis.
+    pub fn parse<'i, 't>(
+        input: &mut Parser<'i, 't>,
+        axis: AxisDirection,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update the `list_keywords` function below
+        //      when this function is updated.
+
+        // <baseline-position>
+        //
+        // It's weird that this accepts <baseline-position>, but not
+        // justify-content...
+        if let Ok(value) = input.try_parse(parse_baseline) {
+            return Ok(SelfAlignment(value));
+        }
+
+        // auto | normal | stretch
+        if let Ok(value) = input.try_parse(parse_auto_normal_stretch) {
+            return Ok(SelfAlignment(value));
+        }
+
+        // <overflow-position>? <self-position>
+        let overflow_position = input
+            .try_parse(parse_overflow_position)
+            .unwrap_or(AlignFlags::empty());
+        let self_position = parse_self_position(input, axis)?;
+        Ok(SelfAlignment(overflow_position | self_position))
+    }
+
+    fn list_keywords(f: KeywordsCollectFn, axis: AxisDirection) {
+        list_baseline_keywords(f);
+        list_auto_normal_stretch(f);
+        list_overflow_position_keywords(f);
+        list_self_position_keywords(f, axis);
+    }
+}
+
+/// The specified value of the align-self property.
+///
+/// <https://drafts.csswg.org/css-align/#propdef-align-self>
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct AlignSelf(pub SelfAlignment);
+
+impl Parse for AlignSelf {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update `impl SpecifiedValueInfo` below when
+        //      this function is updated.
+        Ok(AlignSelf(SelfAlignment::parse(
+            input,
+            AxisDirection::Block,
+        )?))
+    }
+}
+
+impl SpecifiedValueInfo for AlignSelf {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        SelfAlignment::list_keywords(f, AxisDirection::Block);
+    }
+}
+
+/// The specified value of the justify-self property.
+///
+/// <https://drafts.csswg.org/css-align/#propdef-justify-self>
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct JustifySelf(pub SelfAlignment);
+
+impl Parse for JustifySelf {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update `impl SpecifiedValueInfo` below when
+        //      this function is updated.
+        Ok(JustifySelf(SelfAlignment::parse(
+            input,
+            AxisDirection::Inline,
+        )?))
+    }
+}
+
+impl SpecifiedValueInfo for JustifySelf {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        SelfAlignment::list_keywords(f, AxisDirection::Inline);
+    }
+}
+
+/// Value of the `align-items` property
+///
+/// <https://drafts.csswg.org/css-align/#propdef-align-items>
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct AlignItems(pub AlignFlags);
+
+impl AlignItems {
+    /// The initial value 'normal'
+    #[inline]
+    pub fn normal() -> Self {
+        AlignItems(AlignFlags::NORMAL)
+    }
+}
+
+impl Parse for AlignItems {
+    // normal | stretch | <baseline-position> |
+    // <overflow-position>? <self-position>
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update `impl SpecifiedValueInfo` below when
+        //      this function is updated.
+
+        // <baseline-position>
+        if let Ok(baseline) = input.try_parse(parse_baseline) {
+            return Ok(AlignItems(baseline));
+        }
+
+        // normal | stretch
+        if let Ok(value) = input.try_parse(parse_normal_stretch) {
+            return Ok(AlignItems(value));
+        }
+        // <overflow-position>? <self-position>
+        let overflow = input
+            .try_parse(parse_overflow_position)
+            .unwrap_or(AlignFlags::empty());
+        let self_position = parse_self_position(input, AxisDirection::Block)?;
+        Ok(AlignItems(self_position | overflow))
+    }
+}
+
+impl SpecifiedValueInfo for AlignItems {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        list_baseline_keywords(f);
+        list_normal_stretch(f);
+        list_overflow_position_keywords(f);
+        list_self_position_keywords(f, AxisDirection::Block);
+    }
+}
+
+/// Value of the `justify-items` property
+///
+/// <https://drafts.csswg.org/css-align/#justify-items-property>
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToCss, ToResolvedValue, ToShmem)]
+#[repr(C)]
+pub struct JustifyItems(pub AlignFlags);
+
+impl JustifyItems {
+    /// The initial value 'legacy'
+    #[inline]
+    pub fn legacy() -> Self {
+        JustifyItems(AlignFlags::LEGACY)
+    }
+
+    /// The value 'normal'
+    #[inline]
+    pub fn normal() -> Self {
+        JustifyItems(AlignFlags::NORMAL)
+    }
+}
+
+impl Parse for JustifyItems {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // NOTE Please also update `impl SpecifiedValueInfo` below when
+        //      this function is updated.
+
+        // <baseline-position>
+        //
+        // It's weird that this accepts <baseline-position>, but not
+        // justify-content...
+        if let Ok(baseline) = input.try_parse(parse_baseline) {
+            return Ok(JustifyItems(baseline));
+        }
+
+        // normal | stretch
+        if let Ok(value) = input.try_parse(parse_normal_stretch) {
+            return Ok(JustifyItems(value));
+        }
+
+        // legacy | [ legacy && [ left | right | center ] ]
+        if let Ok(value) = input.try_parse(parse_legacy) {
+            return Ok(JustifyItems(value));
+        }
+
+        // <overflow-position>? <self-position>
+        let overflow = input
+            .try_parse(parse_overflow_position)
+            .unwrap_or(AlignFlags::empty());
+        let self_position = parse_self_position(input, AxisDirection::Inline)?;
+        Ok(JustifyItems(overflow | self_position))
+    }
+}
+
+impl SpecifiedValueInfo for JustifyItems {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        list_baseline_keywords(f);
+        list_normal_stretch(f);
+        list_legacy_keywords(f);
+        list_overflow_position_keywords(f);
+        list_self_position_keywords(f, AxisDirection::Inline);
+    }
+}
+
+// auto | normal | stretch
+fn parse_auto_normal_stretch<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_auto_normal_stretch` function
+    //      below when this function is updated.
+    try_match_ident_ignore_ascii_case! { input,
+        "auto" => Ok(AlignFlags::AUTO),
+        "normal" => Ok(AlignFlags::NORMAL),
+        "stretch" => Ok(AlignFlags::STRETCH),
+    }
+}
+
+fn list_auto_normal_stretch(f: KeywordsCollectFn) {
+    f(&["auto", "normal", "stretch"]);
+}
+
+// normal | stretch
+fn parse_normal_stretch<'i, 't>(input: &mut Parser<'i, 't>) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_normal_stretch` function below
+    //      when this function is updated.
+    try_match_ident_ignore_ascii_case! { input,
+        "normal" => Ok(AlignFlags::NORMAL),
+        "stretch" => Ok(AlignFlags::STRETCH),
+    }
+}
+
+fn list_normal_stretch(f: KeywordsCollectFn) {
+    f(&["normal", "stretch"]);
+}
+
+// <baseline-position>
+fn parse_baseline<'i, 't>(input: &mut Parser<'i, 't>) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_baseline_keywords` function
+    //      below when this function is updated.
+    try_match_ident_ignore_ascii_case! { input,
+        "baseline" => Ok(AlignFlags::BASELINE),
+        "first" => {
+            input.expect_ident_matching("baseline")?;
+            Ok(AlignFlags::BASELINE)
+        },
+        "last" => {
+            input.expect_ident_matching("baseline")?;
+            Ok(AlignFlags::LAST_BASELINE)
+        },
+    }
+}
+
+fn list_baseline_keywords(f: KeywordsCollectFn) {
+    f(&["baseline", "first baseline", "last baseline"]);
+}
+
+// <content-distribution>
+fn parse_content_distribution<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_content_distribution_keywords`
+    //      function below when this function is updated.
+    try_match_ident_ignore_ascii_case! { input,
+        "stretch" => Ok(AlignFlags::STRETCH),
+        "space-between" => Ok(AlignFlags::SPACE_BETWEEN),
+        "space-around" => Ok(AlignFlags::SPACE_AROUND),
+        "space-evenly" => Ok(AlignFlags::SPACE_EVENLY),
+    }
+}
+
+fn list_content_distribution_keywords(f: KeywordsCollectFn) {
+    f(&["stretch", "space-between", "space-around", "space-evenly"]);
+}
+
+// <overflow-position>
+fn parse_overflow_position<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_overflow_position_keywords`
+    //      function below when this function is updated.
+    try_match_ident_ignore_ascii_case! { input,
+        "safe" => Ok(AlignFlags::SAFE),
+        "unsafe" => Ok(AlignFlags::UNSAFE),
+    }
+}
+
+fn list_overflow_position_keywords(f: KeywordsCollectFn) {
+    f(&["safe", "unsafe"]);
+}
+
+// <self-position> | left | right in the inline axis.
+fn parse_self_position<'i, 't>(
+    input: &mut Parser<'i, 't>,
+    axis: AxisDirection,
+) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_self_position_keywords`
+    //      function below when this function is updated.
+    Ok(try_match_ident_ignore_ascii_case! { input,
+        "start" => AlignFlags::START,
+        "end" => AlignFlags::END,
+        "flex-start" => AlignFlags::FLEX_START,
+        "flex-end" => AlignFlags::FLEX_END,
+        "center" => AlignFlags::CENTER,
+        "self-start" => AlignFlags::SELF_START,
+        "self-end" => AlignFlags::SELF_END,
+        "left" if axis == AxisDirection::Inline => AlignFlags::LEFT,
+        "right" if axis == AxisDirection::Inline => AlignFlags::RIGHT,
+    })
+}
+
+fn list_self_position_keywords(f: KeywordsCollectFn, axis: AxisDirection) {
+    f(&[
+        "start",
+        "end",
+        "flex-start",
+        "flex-end",
+        "center",
+        "self-start",
+        "self-end",
+    ]);
+    if axis == AxisDirection::Inline {
+        f(&["left", "right"]);
+    }
+}
+
+fn parse_left_right_center<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_legacy_keywords` function below
+    //      when this function is updated.
+    Ok(try_match_ident_ignore_ascii_case! { input,
+        "left" => AlignFlags::LEFT,
+        "right" => AlignFlags::RIGHT,
+        "center" => AlignFlags::CENTER,
+    })
+}
+
+// legacy | [ legacy && [ left | right | center ] ]
+fn parse_legacy<'i, 't>(input: &mut Parser<'i, 't>) -> Result<AlignFlags, ParseError<'i>> {
+    // NOTE Please also update the `list_legacy_keywords` function below
+    //      when this function is updated.
+    let flags = try_match_ident_ignore_ascii_case! { input,
+        "legacy" => {
+            let flags = input.try_parse(parse_left_right_center)
+                .unwrap_or(AlignFlags::empty());
+
+            return Ok(AlignFlags::LEGACY | flags)
+        },
+        "left" => AlignFlags::LEFT,
+        "right" => AlignFlags::RIGHT,
+        "center" => AlignFlags::CENTER,
+    };
+
+    input.expect_ident_matching("legacy")?;
+    Ok(AlignFlags::LEGACY | flags)
+}
+
+fn list_legacy_keywords(f: KeywordsCollectFn) {
+    f(&["legacy", "left", "right", "center"]);
+}
diff --git a/servo/components/style/values/specified/angle.rs b/servo/components/style/values/specified/angle.rs
new file mode 100644
index 0000000000..08c6b44367
--- /dev/null
+++ b/servo/components/style/values/specified/angle.rs
@@ -0,0 +1,256 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified angles.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::angle::Angle as ComputedAngle;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::specified::calc::CalcNode;
+use crate::values::CSSFloat;
+use crate::Zero;
+use cssparser::{Parser, Token};
+use std::f32::consts::PI;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, ToCss};
+
+/// A specified angle dimension.
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, PartialOrd, ToCss, ToShmem)]
+pub enum AngleDimension {
+    /// An angle with degree unit.
+    #[css(dimension)]
+    Deg(CSSFloat),
+    /// An angle with gradian unit.
+    #[css(dimension)]
+    Grad(CSSFloat),
+    /// An angle with radian unit.
+    #[css(dimension)]
+    Rad(CSSFloat),
+    /// An angle with turn unit.
+    #[css(dimension)]
+    Turn(CSSFloat),
+}
+
+impl Zero for AngleDimension {
+    fn zero() -> Self {
+        AngleDimension::Deg(0.)
+    }
+
+    fn is_zero(&self) -> bool {
+        match *self {
+            AngleDimension::Deg(ref f) |
+            AngleDimension::Grad(ref f) |
+            AngleDimension::Rad(ref f) |
+            AngleDimension::Turn(ref f) => *f == 0.,
+        }
+    }
+}
+
+impl AngleDimension {
+    /// Returns the amount of degrees this angle represents.
+    #[inline]
+    fn degrees(&self) -> CSSFloat {
+        const DEG_PER_RAD: f32 = 180.0 / PI;
+        const DEG_PER_TURN: f32 = 360.0;
+        const DEG_PER_GRAD: f32 = 180.0 / 200.0;
+
+        match *self {
+            AngleDimension::Deg(d) => d,
+            AngleDimension::Rad(rad) => rad * DEG_PER_RAD,
+            AngleDimension::Turn(turns) => turns * DEG_PER_TURN,
+            AngleDimension::Grad(gradians) => gradians * DEG_PER_GRAD,
+        }
+    }
+}
+
+/// A specified Angle value, which is just the angle dimension, plus whether it
+/// was specified as `calc()` or not.
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToShmem)]
+pub struct Angle {
+    value: AngleDimension,
+    was_calc: bool,
+}
+
+impl Zero for Angle {
+    fn zero() -> Self {
+        Self {
+            value: Zero::zero(),
+            was_calc: false,
+        }
+    }
+
+    fn is_zero(&self) -> bool {
+        self.value.is_zero()
+    }
+}
+
+impl ToCss for Angle {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.was_calc {
+            dest.write_str("calc(")?;
+        }
+        self.value.to_css(dest)?;
+        if self.was_calc {
+            dest.write_str(")")?;
+        }
+        Ok(())
+    }
+}
+
+impl ToComputedValue for Angle {
+    type ComputedValue = ComputedAngle;
+
+    #[inline]
+    fn to_computed_value(&self, _context: &Context) -> Self::ComputedValue {
+        ComputedAngle::from_degrees(self.degrees())
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Angle {
+            value: AngleDimension::Deg(computed.degrees()),
+            was_calc: false,
+        }
+    }
+}
+
+impl Angle {
+    /// Creates an angle with the given value in degrees.
+    #[inline]
+    pub fn from_degrees(value: CSSFloat, was_calc: bool) -> Self {
+        Angle {
+            value: AngleDimension::Deg(value),
+            was_calc,
+        }
+    }
+
+    /// Creates an angle with the given value in radians.
+    #[inline]
+    pub fn from_radians(value: CSSFloat) -> Self {
+        Angle {
+            value: AngleDimension::Rad(value),
+            was_calc: false,
+        }
+    }
+
+    /// Return `0deg`.
+    pub fn zero() -> Self {
+        Self::from_degrees(0.0, false)
+    }
+
+    /// Returns the value of the angle in degrees, mostly for `calc()`.
+    #[inline]
+    pub fn degrees(&self) -> CSSFloat {
+        self.value.degrees()
+    }
+
+    /// Returns the value of the angle in radians.
+    #[inline]
+    pub fn radians(&self) -> CSSFloat {
+        const RAD_PER_DEG: f32 = PI / 180.0;
+        self.value.degrees() * RAD_PER_DEG
+    }
+
+    /// Whether this specified angle came from a `calc()` expression.
+    #[inline]
+    pub fn was_calc(&self) -> bool {
+        self.was_calc
+    }
+
+    /// Returns an `Angle` parsed from a `calc()` expression.
+    pub fn from_calc(degrees: CSSFloat) -> Self {
+        Angle {
+            value: AngleDimension::Deg(degrees),
+            was_calc: true,
+        }
+    }
+}
+
+/// Whether to allow parsing an unitless zero as a valid angle.
+///
+/// This should always be `No`, except for exceptions like:
+///
+///   https://github.com/w3c/fxtf-drafts/issues/228
+///
+/// See also: https://github.com/w3c/csswg-drafts/issues/1162.
+#[allow(missing_docs)]
+pub enum AllowUnitlessZeroAngle {
+    Yes,
+    No,
+}
+
+impl Parse for Angle {
+    /// Parses an angle according to CSS-VALUES § 6.1.
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(context, input, AllowUnitlessZeroAngle::No)
+    }
+}
+
+impl Angle {
+    /// Parse an `<angle>` value given a value and an unit.
+    pub fn parse_dimension(value: CSSFloat, unit: &str, was_calc: bool) -> Result<Angle, ()> {
+        let value = match_ignore_ascii_case! { unit,
+            "deg" => AngleDimension::Deg(value),
+            "grad" => AngleDimension::Grad(value),
+            "turn" => AngleDimension::Turn(value),
+            "rad" => AngleDimension::Rad(value),
+             _ => return Err(())
+        };
+
+        Ok(Self { value, was_calc })
+    }
+
+    /// Parse an `<angle>` allowing unitless zero to represent a zero angle.
+    ///
+    /// See the comment in `AllowUnitlessZeroAngle` for why.
+    #[inline]
+    pub fn parse_with_unitless<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(context, input, AllowUnitlessZeroAngle::Yes)
+    }
+
+    pub(super) fn parse_internal<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_unitless_zero: AllowUnitlessZeroAngle,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let t = input.next()?;
+        let allow_unitless_zero = matches!(allow_unitless_zero, AllowUnitlessZeroAngle::Yes);
+        match *t {
+            Token::Dimension {
+                value, ref unit, ..
+            } => {
+                match Angle::parse_dimension(value, unit, /* from_calc = */ false) {
+                    Ok(angle) => Ok(angle),
+                    Err(()) => {
+                        let t = t.clone();
+                        Err(input.new_unexpected_token_error(t))
+                    },
+                }
+            },
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                CalcNode::parse_angle(context, input, function)
+            },
+            Token::Number { value, .. } if value == 0. && allow_unitless_zero => Ok(Angle::zero()),
+            ref t => {
+                let t = t.clone();
+                Err(input.new_unexpected_token_error(t))
+            },
+        }
+    }
+}
+
+impl SpecifiedValueInfo for Angle {}
diff --git a/servo/components/style/values/specified/background.rs b/servo/components/style/values/specified/background.rs
new file mode 100644
index 0000000000..29f6d6b352
--- /dev/null
+++ b/servo/components/style/values/specified/background.rs
@@ -0,0 +1,143 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS values related to backgrounds.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::background::BackgroundSize as GenericBackgroundSize;
+use crate::values::specified::length::{
+    NonNegativeLengthPercentage, NonNegativeLengthPercentageOrAuto,
+};
+use cssparser::Parser;
+use selectors::parser::SelectorParseErrorKind;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ParseError, ToCss};
+
+/// A specified value for the `background-size` property.
+pub type BackgroundSize = GenericBackgroundSize<NonNegativeLengthPercentage>;
+
+impl Parse for BackgroundSize {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(width) = input.try_parse(|i| NonNegativeLengthPercentageOrAuto::parse(context, i))
+        {
+            let height = input
+                .try_parse(|i| NonNegativeLengthPercentageOrAuto::parse(context, i))
+                .unwrap_or(NonNegativeLengthPercentageOrAuto::auto());
+            return Ok(GenericBackgroundSize::ExplicitSize { width, height });
+        }
+        Ok(try_match_ident_ignore_ascii_case! { input,
+            "cover" => GenericBackgroundSize::Cover,
+            "contain" => GenericBackgroundSize::Contain,
+        })
+    }
+}
+
+/// One of the keywords for `background-repeat`.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[value_info(other_values = "repeat-x,repeat-y")]
+pub enum BackgroundRepeatKeyword {
+    Repeat,
+    Space,
+    Round,
+    NoRepeat,
+}
+
+/// The value of the `background-repeat` property, with `repeat-x` / `repeat-y`
+/// represented as the combination of `no-repeat` and `repeat` in the opposite
+/// axes.
+///
+/// https://drafts.csswg.org/css-backgrounds/#the-background-repeat
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct BackgroundRepeat(pub BackgroundRepeatKeyword, pub BackgroundRepeatKeyword);
+
+impl BackgroundRepeat {
+    /// Returns the `repeat repeat` value.
+    pub fn repeat() -> Self {
+        BackgroundRepeat(
+            BackgroundRepeatKeyword::Repeat,
+            BackgroundRepeatKeyword::Repeat,
+        )
+    }
+}
+
+impl ToCss for BackgroundRepeat {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match (self.0, self.1) {
+            (BackgroundRepeatKeyword::Repeat, BackgroundRepeatKeyword::NoRepeat) => {
+                dest.write_str("repeat-x")
+            },
+            (BackgroundRepeatKeyword::NoRepeat, BackgroundRepeatKeyword::Repeat) => {
+                dest.write_str("repeat-y")
+            },
+            (horizontal, vertical) => {
+                horizontal.to_css(dest)?;
+                if horizontal != vertical {
+                    dest.write_str(" ")?;
+                    vertical.to_css(dest)?;
+                }
+                Ok(())
+            },
+        }
+    }
+}
+
+impl Parse for BackgroundRepeat {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let ident = input.expect_ident_cloned()?;
+
+        match_ignore_ascii_case! { &ident,
+            "repeat-x" => {
+                return Ok(BackgroundRepeat(BackgroundRepeatKeyword::Repeat, BackgroundRepeatKeyword::NoRepeat));
+            },
+            "repeat-y" => {
+                return Ok(BackgroundRepeat(BackgroundRepeatKeyword::NoRepeat, BackgroundRepeatKeyword::Repeat));
+            },
+            _ => {},
+        }
+
+        let horizontal = match BackgroundRepeatKeyword::from_ident(&ident) {
+            Ok(h) => h,
+            Err(()) => {
+                return Err(
+                    input.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone()))
+                );
+            },
+        };
+
+        let vertical = input.try_parse(BackgroundRepeatKeyword::parse).ok();
+        Ok(BackgroundRepeat(horizontal, vertical.unwrap_or(horizontal)))
+    }
+}
diff --git a/servo/components/style/values/specified/basic_shape.rs b/servo/components/style/values/specified/basic_shape.rs
new file mode 100644
index 0000000000..3c571ff8e8
--- /dev/null
+++ b/servo/components/style/values/specified/basic_shape.rs
@@ -0,0 +1,321 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the specified value of
+//! [`basic-shape`][basic-shape]s
+//!
+//! [basic-shape]: https://drafts.csswg.org/css-shapes/#typedef-basic-shape
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::basic_shape as generic;
+use crate::values::generics::basic_shape::{Path, PolygonCoord};
+use crate::values::generics::rect::Rect;
+use crate::values::specified::border::BorderRadius;
+use crate::values::specified::image::Image;
+use crate::values::specified::position::{HorizontalPosition, Position, VerticalPosition};
+use crate::values::specified::url::SpecifiedUrl;
+use crate::values::specified::SVGPathData;
+use crate::values::specified::{LengthPercentage, NonNegativeLengthPercentage};
+use crate::Zero;
+use cssparser::Parser;
+use style_traits::{ParseError, StyleParseErrorKind};
+
+/// A specified alias for FillRule.
+pub use crate::values::generics::basic_shape::FillRule;
+
+/// A specified `clip-path` value.
+pub type ClipPath = generic::GenericClipPath<BasicShape, SpecifiedUrl>;
+
+/// A specified `shape-outside` value.
+pub type ShapeOutside = generic::GenericShapeOutside<BasicShape, Image>;
+
+/// A specified basic shape.
+pub type BasicShape = generic::GenericBasicShape<
+    HorizontalPosition,
+    VerticalPosition,
+    LengthPercentage,
+    NonNegativeLengthPercentage,
+>;
+
+/// The specified value of `inset()`
+pub type InsetRect = generic::InsetRect<LengthPercentage, NonNegativeLengthPercentage>;
+
+/// A specified circle.
+pub type Circle =
+    generic::Circle<HorizontalPosition, VerticalPosition, NonNegativeLengthPercentage>;
+
+/// A specified ellipse.
+pub type Ellipse =
+    generic::Ellipse<HorizontalPosition, VerticalPosition, NonNegativeLengthPercentage>;
+
+/// The specified value of `ShapeRadius`
+pub type ShapeRadius = generic::ShapeRadius<NonNegativeLengthPercentage>;
+
+/// The specified value of `Polygon`
+pub type Polygon = generic::GenericPolygon<LengthPercentage>;
+
+/// A helper for both clip-path and shape-outside parsing of shapes.
+fn parse_shape_or_box<'i, 't, R, ReferenceBox>(
+    context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+    to_shape: impl FnOnce(Box<BasicShape>, ReferenceBox) -> R,
+    to_reference_box: impl FnOnce(ReferenceBox) -> R,
+) -> Result<R, ParseError<'i>>
+where
+    ReferenceBox: Default + Parse,
+{
+    fn parse_component<U: Parse>(
+        context: &ParserContext,
+        input: &mut Parser,
+        component: &mut Option<U>,
+    ) -> bool {
+        if component.is_some() {
+            return false; // already parsed this component
+        }
+
+        *component = input.try_parse(|i| U::parse(context, i)).ok();
+        component.is_some()
+    }
+
+    let mut shape = None;
+    let mut ref_box = None;
+
+    while parse_component(context, input, &mut shape) ||
+        parse_component(context, input, &mut ref_box)
+    {
+        //
+    }
+
+    if let Some(shp) = shape {
+        return Ok(to_shape(Box::new(shp), ref_box.unwrap_or_default()));
+    }
+
+    match ref_box {
+        Some(r) => Ok(to_reference_box(r)),
+        None => Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+    }
+}
+
+impl Parse for ClipPath {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(ClipPath::None);
+        }
+
+        if let Ok(p) = input.try_parse(|i| Path::parse(context, i)) {
+            return Ok(ClipPath::Path(p));
+        }
+
+        if let Ok(url) = input.try_parse(|i| SpecifiedUrl::parse(context, i)) {
+            return Ok(ClipPath::Url(url));
+        }
+
+        parse_shape_or_box(context, input, ClipPath::Shape, ClipPath::Box)
+    }
+}
+
+impl Parse for ShapeOutside {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // Need to parse this here so that `Image::parse_with_cors_anonymous`
+        // doesn't parse it.
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(ShapeOutside::None);
+        }
+
+        if let Ok(image) = input.try_parse(|i| Image::parse_with_cors_anonymous(context, i)) {
+            debug_assert_ne!(image, Image::None);
+            return Ok(ShapeOutside::Image(image));
+        }
+
+        parse_shape_or_box(context, input, ShapeOutside::Shape, ShapeOutside::Box)
+    }
+}
+
+impl Parse for BasicShape {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let function = input.expect_function()?.clone();
+        input.parse_nested_block(move |i| {
+            (match_ignore_ascii_case! { &function,
+                "inset" => return InsetRect::parse_function_arguments(context, i).map(generic::BasicShape::Inset),
+                "circle" => return Circle::parse_function_arguments(context, i).map(generic::BasicShape::Circle),
+                "ellipse" => return Ellipse::parse_function_arguments(context, i).map(generic::BasicShape::Ellipse),
+                "polygon" => return Polygon::parse_function_arguments(context, i).map(generic::BasicShape::Polygon),
+                _ => Err(())
+            }).map_err(|()| {
+                location.new_custom_error(StyleParseErrorKind::UnexpectedFunction(function.clone()))
+            })
+        })
+    }
+}
+
+impl Parse for InsetRect {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("inset")?;
+        input.parse_nested_block(|i| Self::parse_function_arguments(context, i))
+    }
+}
+
+impl InsetRect {
+    /// Parse the inner function arguments of `inset()`
+    fn parse_function_arguments<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let rect = Rect::parse_with(context, input, LengthPercentage::parse)?;
+        let round = if input
+            .try_parse(|i| i.expect_ident_matching("round"))
+            .is_ok()
+        {
+            BorderRadius::parse(context, input)?
+        } else {
+            BorderRadius::zero()
+        };
+        Ok(generic::InsetRect { rect, round })
+    }
+}
+
+impl Parse for Circle {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("circle")?;
+        input.parse_nested_block(|i| Self::parse_function_arguments(context, i))
+    }
+}
+
+impl Circle {
+    fn parse_function_arguments<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let radius = input
+            .try_parse(|i| ShapeRadius::parse(context, i))
+            .unwrap_or_default();
+        let position = if input.try_parse(|i| i.expect_ident_matching("at")).is_ok() {
+            Position::parse(context, input)?
+        } else {
+            Position::center()
+        };
+
+        Ok(generic::Circle { radius, position })
+    }
+}
+
+impl Parse for Ellipse {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("ellipse")?;
+        input.parse_nested_block(|i| Self::parse_function_arguments(context, i))
+    }
+}
+
+impl Ellipse {
+    fn parse_function_arguments<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let (a, b) = input
+            .try_parse(|i| -> Result<_, ParseError> {
+                Ok((
+                    ShapeRadius::parse(context, i)?,
+                    ShapeRadius::parse(context, i)?,
+                ))
+            })
+            .unwrap_or_default();
+        let position = if input.try_parse(|i| i.expect_ident_matching("at")).is_ok() {
+            Position::parse(context, input)?
+        } else {
+            Position::center()
+        };
+
+        Ok(generic::Ellipse {
+            semiaxis_x: a,
+            semiaxis_y: b,
+            position: position,
+        })
+    }
+}
+
+impl Parse for Polygon {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("polygon")?;
+        input.parse_nested_block(|i| Self::parse_function_arguments(context, i))
+    }
+}
+
+impl Polygon {
+    /// Parse the inner arguments of a `polygon` function.
+    fn parse_function_arguments<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let fill = input
+            .try_parse(|i| -> Result<_, ParseError> {
+                let fill = FillRule::parse(i)?;
+                i.expect_comma()?; // only eat the comma if there is something before it
+                Ok(fill)
+            })
+            .unwrap_or_default();
+
+        let coordinates = input
+            .parse_comma_separated(|i| {
+                Ok(PolygonCoord(
+                    LengthPercentage::parse(context, i)?,
+                    LengthPercentage::parse(context, i)?,
+                ))
+            })?
+            .into();
+
+        Ok(Polygon { fill, coordinates })
+    }
+}
+
+impl Parse for Path {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("path")?;
+        input.parse_nested_block(|i| Self::parse_function_arguments(context, i))
+    }
+}
+
+impl Path {
+    /// Parse the inner arguments of a `path` function.
+    fn parse_function_arguments<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let fill = input
+            .try_parse(|i| -> Result<_, ParseError> {
+                let fill = FillRule::parse(i)?;
+                i.expect_comma()?;
+                Ok(fill)
+            })
+            .unwrap_or_default();
+        let path = SVGPathData::parse(context, input)?;
+        Ok(Path { fill, path })
+    }
+}
diff --git a/servo/components/style/values/specified/border.rs b/servo/components/style/values/specified/border.rs
new file mode 100644
index 0000000000..817a5aaddd
--- /dev/null
+++ b/servo/components/style/values/specified/border.rs
@@ -0,0 +1,311 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS values related to borders.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::{self, Context, ToComputedValue};
+use crate::values::generics::border::BorderCornerRadius as GenericBorderCornerRadius;
+use crate::values::generics::border::BorderImageSideWidth as GenericBorderImageSideWidth;
+use crate::values::generics::border::BorderImageSlice as GenericBorderImageSlice;
+use crate::values::generics::border::BorderRadius as GenericBorderRadius;
+use crate::values::generics::border::BorderSpacing as GenericBorderSpacing;
+use crate::values::generics::rect::Rect;
+use crate::values::generics::size::Size2D;
+use crate::values::specified::length::{NonNegativeLength, NonNegativeLengthPercentage};
+use crate::values::specified::{AllowQuirks, NonNegativeNumber, NonNegativeNumberOrPercentage};
+use crate::Zero;
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, ParseError, ToCss};
+
+/// A specified value for a single side of a `border-style` property.
+///
+/// The order here corresponds to the integer values from the border conflict
+/// resolution rules in CSS 2.1 § 17.6.2.1. Higher values override lower values.
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    MallocSizeOf,
+    Ord,
+    Parse,
+    PartialEq,
+    PartialOrd,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum BorderStyle {
+    Hidden,
+    None,
+    Inset,
+    Groove,
+    Outset,
+    Ridge,
+    Dotted,
+    Dashed,
+    Solid,
+    Double,
+}
+
+impl BorderStyle {
+    /// Whether this border style is either none or hidden.
+    #[inline]
+    pub fn none_or_hidden(&self) -> bool {
+        matches!(*self, BorderStyle::None | BorderStyle::Hidden)
+    }
+}
+
+/// A specified value for a single side of the `border-width` property.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum BorderSideWidth {
+    /// `thin`
+    Thin,
+    /// `medium`
+    Medium,
+    /// `thick`
+    Thick,
+    /// `<length>`
+    Length(NonNegativeLength),
+}
+
+/// A specified value for the `border-image-width` property.
+pub type BorderImageWidth = Rect<BorderImageSideWidth>;
+
+/// A specified value for a single side of a `border-image-width` property.
+pub type BorderImageSideWidth =
+    GenericBorderImageSideWidth<NonNegativeLengthPercentage, NonNegativeNumber>;
+
+/// A specified value for the `border-image-slice` property.
+pub type BorderImageSlice = GenericBorderImageSlice<NonNegativeNumberOrPercentage>;
+
+/// A specified value for the `border-radius` property.
+pub type BorderRadius = GenericBorderRadius<NonNegativeLengthPercentage>;
+
+/// A specified value for the `border-*-radius` longhand properties.
+pub type BorderCornerRadius = GenericBorderCornerRadius<NonNegativeLengthPercentage>;
+
+/// A specified value for the `border-spacing` longhand properties.
+pub type BorderSpacing = GenericBorderSpacing<NonNegativeLength>;
+
+impl BorderImageSlice {
+    /// Returns the `100%` value.
+    #[inline]
+    pub fn hundred_percent() -> Self {
+        GenericBorderImageSlice {
+            offsets: Rect::all(NonNegativeNumberOrPercentage::hundred_percent()),
+            fill: false,
+        }
+    }
+}
+
+impl BorderSideWidth {
+    /// Returns the `0px` value.
+    #[inline]
+    pub fn zero() -> Self {
+        BorderSideWidth::Length(NonNegativeLength::zero())
+    }
+
+    /// Parses, with quirks.
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(length) =
+            input.try_parse(|i| NonNegativeLength::parse_quirky(context, i, allow_quirks))
+        {
+            return Ok(BorderSideWidth::Length(length));
+        }
+        try_match_ident_ignore_ascii_case! { input,
+            "thin" => Ok(BorderSideWidth::Thin),
+            "medium" => Ok(BorderSideWidth::Medium),
+            "thick" => Ok(BorderSideWidth::Thick),
+        }
+    }
+}
+
+impl Parse for BorderSideWidth {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl ToComputedValue for BorderSideWidth {
+    type ComputedValue = computed::NonNegativeLength;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        // We choose the pixel length of the keyword values the same as both spec and gecko.
+        // Spec: https://drafts.csswg.org/css-backgrounds-3/#line-width
+        // Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1312155#c0
+        match *self {
+            BorderSideWidth::Thin => NonNegativeLength::from_px(1.).to_computed_value(context),
+            BorderSideWidth::Medium => NonNegativeLength::from_px(3.).to_computed_value(context),
+            BorderSideWidth::Thick => NonNegativeLength::from_px(5.).to_computed_value(context),
+            BorderSideWidth::Length(ref length) => length.to_computed_value(context),
+        }
+        .into()
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        BorderSideWidth::Length(ToComputedValue::from_computed_value(computed))
+    }
+}
+
+impl BorderImageSideWidth {
+    /// Returns `1`.
+    #[inline]
+    pub fn one() -> Self {
+        GenericBorderImageSideWidth::Number(NonNegativeNumber::new(1.))
+    }
+}
+
+impl Parse for BorderImageSlice {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut fill = input.try_parse(|i| i.expect_ident_matching("fill")).is_ok();
+        let offsets = Rect::parse_with(context, input, NonNegativeNumberOrPercentage::parse)?;
+        if !fill {
+            fill = input.try_parse(|i| i.expect_ident_matching("fill")).is_ok();
+        }
+        Ok(GenericBorderImageSlice { offsets, fill })
+    }
+}
+
+impl Parse for BorderRadius {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let widths = Rect::parse_with(context, input, NonNegativeLengthPercentage::parse)?;
+        let heights = if input.try_parse(|i| i.expect_delim('/')).is_ok() {
+            Rect::parse_with(context, input, NonNegativeLengthPercentage::parse)?
+        } else {
+            widths.clone()
+        };
+
+        Ok(GenericBorderRadius {
+            top_left: BorderCornerRadius::new(widths.0, heights.0),
+            top_right: BorderCornerRadius::new(widths.1, heights.1),
+            bottom_right: BorderCornerRadius::new(widths.2, heights.2),
+            bottom_left: BorderCornerRadius::new(widths.3, heights.3),
+        })
+    }
+}
+
+impl Parse for BorderCornerRadius {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Size2D::parse_with(context, input, NonNegativeLengthPercentage::parse)
+            .map(GenericBorderCornerRadius)
+    }
+}
+
+impl Parse for BorderSpacing {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Size2D::parse_with(context, input, |context, input| {
+            NonNegativeLength::parse_quirky(context, input, AllowQuirks::Yes)
+        })
+        .map(GenericBorderSpacing)
+    }
+}
+
+/// A single border-image-repeat keyword.
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum BorderImageRepeatKeyword {
+    Stretch,
+    Repeat,
+    Round,
+    Space,
+}
+
+/// The specified value for the `border-image-repeat` property.
+///
+/// https://drafts.csswg.org/css-backgrounds/#the-border-image-repeat
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct BorderImageRepeat(pub BorderImageRepeatKeyword, pub BorderImageRepeatKeyword);
+
+impl ToCss for BorderImageRepeat {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.0.to_css(dest)?;
+        if self.0 != self.1 {
+            dest.write_str(" ")?;
+            self.1.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+impl BorderImageRepeat {
+    /// Returns the `stretch` value.
+    #[inline]
+    pub fn stretch() -> Self {
+        BorderImageRepeat(
+            BorderImageRepeatKeyword::Stretch,
+            BorderImageRepeatKeyword::Stretch,
+        )
+    }
+}
+
+impl Parse for BorderImageRepeat {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let horizontal = BorderImageRepeatKeyword::parse(input)?;
+        let vertical = input.try_parse(BorderImageRepeatKeyword::parse).ok();
+        Ok(BorderImageRepeat(
+            horizontal,
+            vertical.unwrap_or(horizontal),
+        ))
+    }
+}
diff --git a/servo/components/style/values/specified/box.rs b/servo/components/style/values/specified/box.rs
new file mode 100644
index 0000000000..ad4da4df3f
--- /dev/null
+++ b/servo/components/style/values/specified/box.rs
@@ -0,0 +1,2281 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for box properties.
+
+use crate::custom_properties::Name as CustomPropertyName;
+use crate::parser::{Parse, ParserContext};
+use crate::properties::{LonghandId, PropertyDeclarationId};
+use crate::properties::{PropertyId, ShorthandId};
+use crate::values::generics::box_::{
+    GenericAnimationIterationCount, GenericLineClamp, GenericPerspective,
+};
+use crate::values::generics::box_::{
+    GenericContainIntrinsicSize, GenericVerticalAlign, VerticalAlignKeyword,
+};
+use crate::values::specified::length::{LengthPercentage, NonNegativeLength};
+use crate::values::specified::{AllowQuirks, Integer, Number};
+use crate::values::{CustomIdent, KeyframesName, TimelineName};
+use crate::Atom;
+use cssparser::Parser;
+use num_traits::FromPrimitive;
+use std::fmt::{self, Write};
+use style_traits::{CssWriter, KeywordsCollectFn, ParseError};
+use style_traits::{SpecifiedValueInfo, StyleParseErrorKind, ToCss};
+
+#[cfg(feature = "gecko")]
+fn moz_display_values_enabled(context: &ParserContext) -> bool {
+    context.in_ua_or_chrome_sheet()
+}
+
+#[cfg(not(feature = "servo-layout-2020"))]
+fn flexbox_enabled() -> bool {
+    true
+}
+
+#[cfg(feature = "servo-layout-2020")]
+fn flexbox_enabled() -> bool {
+    servo_config::prefs::pref_map()
+        .get("layout.flexbox.enabled")
+        .as_bool()
+        .unwrap_or(false)
+}
+
+/// Defines an element’s display type, which consists of
+/// the two basic qualities of how an element generates boxes
+/// <https://drafts.csswg.org/css-display/#propdef-display>
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug, Eq, FromPrimitive, Hash, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+#[repr(u8)]
+pub enum DisplayOutside {
+    None = 0,
+    Inline,
+    Block,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableCaption,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    InternalTable,
+    #[cfg(feature = "gecko")]
+    InternalRuby,
+    #[cfg(feature = "gecko")]
+    XUL,
+}
+
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug, Eq, FromPrimitive, Hash, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+#[repr(u8)]
+pub enum DisplayInside {
+    None = 0,
+    #[cfg(any(feature = "servo-layout-2020", feature = "gecko"))]
+    Contents,
+    Flow,
+    FlowRoot,
+    Flex,
+    #[cfg(feature = "gecko")]
+    Grid,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    Table,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableRowGroup,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableColumn,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableColumnGroup,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableHeaderGroup,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableFooterGroup,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableRow,
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    TableCell,
+    #[cfg(feature = "gecko")]
+    Ruby,
+    #[cfg(feature = "gecko")]
+    RubyBase,
+    #[cfg(feature = "gecko")]
+    RubyBaseContainer,
+    #[cfg(feature = "gecko")]
+    RubyText,
+    #[cfg(feature = "gecko")]
+    RubyTextContainer,
+    #[cfg(feature = "gecko")]
+    WebkitBox,
+    #[cfg(feature = "gecko")]
+    MozBox,
+}
+
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct Display(u16);
+
+/// Gecko-only impl block for Display (shared stuff later in this file):
+#[allow(missing_docs)]
+#[allow(non_upper_case_globals)]
+impl Display {
+    // Our u16 bits are used as follows:    LOOOOOOOIIIIIIII
+    const LIST_ITEM_BIT: u16 = 0x8000; //^
+    const DISPLAY_OUTSIDE_BITS: u16 = 7; // ^^^^^^^
+    const DISPLAY_INSIDE_BITS: u16 = 8; //        ^^^^^^^^
+
+    /// https://drafts.csswg.org/css-display/#the-display-properties
+    pub const None: Self = Self::new(DisplayOutside::None, DisplayInside::None);
+    #[cfg(any(feature = "servo-layout-2020", feature = "gecko"))]
+    pub const Contents: Self = Self::new(DisplayOutside::None, DisplayInside::Contents);
+    pub const Inline: Self = Self::new(DisplayOutside::Inline, DisplayInside::Flow);
+    pub const InlineBlock: Self = Self::new(DisplayOutside::Inline, DisplayInside::FlowRoot);
+    pub const Block: Self = Self::new(DisplayOutside::Block, DisplayInside::Flow);
+    #[cfg(feature = "gecko")]
+    pub const FlowRoot: Self = Self::new(DisplayOutside::Block, DisplayInside::FlowRoot);
+    pub const Flex: Self = Self::new(DisplayOutside::Block, DisplayInside::Flex);
+    pub const InlineFlex: Self = Self::new(DisplayOutside::Inline, DisplayInside::Flex);
+    #[cfg(feature = "gecko")]
+    pub const Grid: Self = Self::new(DisplayOutside::Block, DisplayInside::Grid);
+    #[cfg(feature = "gecko")]
+    pub const InlineGrid: Self = Self::new(DisplayOutside::Inline, DisplayInside::Grid);
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const Table: Self = Self::new(DisplayOutside::Block, DisplayInside::Table);
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const InlineTable: Self = Self::new(DisplayOutside::Inline, DisplayInside::Table);
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableCaption: Self = Self::new(DisplayOutside::TableCaption, DisplayInside::Flow);
+    #[cfg(feature = "gecko")]
+    pub const Ruby: Self = Self::new(DisplayOutside::Inline, DisplayInside::Ruby);
+    #[cfg(feature = "gecko")]
+    pub const WebkitBox: Self = Self::new(DisplayOutside::Block, DisplayInside::WebkitBox);
+    #[cfg(feature = "gecko")]
+    pub const WebkitInlineBox: Self = Self::new(DisplayOutside::Inline, DisplayInside::WebkitBox);
+
+    // Internal table boxes.
+
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableRowGroup: Self =
+        Self::new(DisplayOutside::InternalTable, DisplayInside::TableRowGroup);
+
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableHeaderGroup: Self = Self::new(
+        DisplayOutside::InternalTable,
+        DisplayInside::TableHeaderGroup,
+    );
+
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableFooterGroup: Self = Self::new(
+        DisplayOutside::InternalTable,
+        DisplayInside::TableFooterGroup,
+    );
+
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableColumn: Self =
+        Self::new(DisplayOutside::InternalTable, DisplayInside::TableColumn);
+
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableColumnGroup: Self = Self::new(
+        DisplayOutside::InternalTable,
+        DisplayInside::TableColumnGroup,
+    );
+
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableRow: Self = Self::new(DisplayOutside::InternalTable, DisplayInside::TableRow);
+
+    #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+    pub const TableCell: Self = Self::new(DisplayOutside::InternalTable, DisplayInside::TableCell);
+
+    /// Internal ruby boxes.
+    #[cfg(feature = "gecko")]
+    pub const RubyBase: Self = Self::new(DisplayOutside::InternalRuby, DisplayInside::RubyBase);
+    #[cfg(feature = "gecko")]
+    pub const RubyBaseContainer: Self = Self::new(
+        DisplayOutside::InternalRuby,
+        DisplayInside::RubyBaseContainer,
+    );
+    #[cfg(feature = "gecko")]
+    pub const RubyText: Self = Self::new(DisplayOutside::InternalRuby, DisplayInside::RubyText);
+    #[cfg(feature = "gecko")]
+    pub const RubyTextContainer: Self = Self::new(
+        DisplayOutside::InternalRuby,
+        DisplayInside::RubyTextContainer,
+    );
+
+    /// XUL boxes.
+    #[cfg(feature = "gecko")]
+    pub const MozBox: Self = Self::new(DisplayOutside::Block, DisplayInside::MozBox);
+    #[cfg(feature = "gecko")]
+    pub const MozInlineBox: Self = Self::new(DisplayOutside::Inline, DisplayInside::MozBox);
+
+    /// Make a raw display value from <display-outside> and <display-inside> values.
+    #[inline]
+    const fn new(outside: DisplayOutside, inside: DisplayInside) -> Self {
+        let o: u16 = ((outside as u8) as u16) << Self::DISPLAY_INSIDE_BITS;
+        let i: u16 = (inside as u8) as u16;
+        Self(o | i)
+    }
+
+    /// Make a display enum value from <display-outside> and <display-inside> values.
+    #[inline]
+    fn from3(outside: DisplayOutside, inside: DisplayInside, list_item: bool) -> Self {
+        let v = Self::new(outside, inside);
+        if !list_item {
+            return v;
+        }
+        Self(v.0 | Self::LIST_ITEM_BIT)
+    }
+
+    /// Accessor for the <display-inside> value.
+    #[inline]
+    pub fn inside(&self) -> DisplayInside {
+        DisplayInside::from_u16(self.0 & ((1 << Self::DISPLAY_INSIDE_BITS) - 1)).unwrap()
+    }
+
+    /// Accessor for the <display-outside> value.
+    #[inline]
+    pub fn outside(&self) -> DisplayOutside {
+        DisplayOutside::from_u16(
+            (self.0 >> Self::DISPLAY_INSIDE_BITS) & ((1 << Self::DISPLAY_OUTSIDE_BITS) - 1),
+        )
+        .unwrap()
+    }
+
+    /// Returns the raw underlying u16 value.
+    #[inline]
+    pub const fn to_u16(&self) -> u16 {
+        self.0
+    }
+
+    /// Whether this is `display: inline` (or `inline list-item`).
+    #[inline]
+    pub fn is_inline_flow(&self) -> bool {
+        self.outside() == DisplayOutside::Inline && self.inside() == DisplayInside::Flow
+    }
+
+    /// Returns whether this `display` value is some kind of list-item.
+    #[inline]
+    pub const fn is_list_item(&self) -> bool {
+        (self.0 & Self::LIST_ITEM_BIT) != 0
+    }
+
+    /// Returns whether this `display` value is a ruby level container.
+    pub fn is_ruby_level_container(&self) -> bool {
+        match *self {
+            #[cfg(feature = "gecko")]
+            Display::RubyBaseContainer | Display::RubyTextContainer => true,
+            _ => false,
+        }
+    }
+
+    /// Returns whether this `display` value is one of the types for ruby.
+    pub fn is_ruby_type(&self) -> bool {
+        match self.inside() {
+            #[cfg(feature = "gecko")]
+            DisplayInside::Ruby |
+            DisplayInside::RubyBase |
+            DisplayInside::RubyText |
+            DisplayInside::RubyBaseContainer |
+            DisplayInside::RubyTextContainer => true,
+            _ => false,
+        }
+    }
+}
+
+/// Shared Display impl for both Gecko and Servo.
+#[allow(non_upper_case_globals)]
+impl Display {
+    /// The initial display value.
+    #[inline]
+    pub fn inline() -> Self {
+        Display::Inline
+    }
+
+    /// <https://drafts.csswg.org/css2/visuren.html#x13>
+    #[cfg(feature = "servo")]
+    #[inline]
+    pub fn is_atomic_inline_level(&self) -> bool {
+        match *self {
+            Display::InlineBlock | Display::InlineFlex => true,
+            #[cfg(any(feature = "servo-layout-2013"))]
+            Display::InlineTable => true,
+            _ => false,
+        }
+    }
+
+    /// Returns whether this `display` value is the display of a flex or
+    /// grid container.
+    ///
+    /// This is used to implement various style fixups.
+    pub fn is_item_container(&self) -> bool {
+        match self.inside() {
+            DisplayInside::Flex => true,
+            #[cfg(feature = "gecko")]
+            DisplayInside::Grid => true,
+            #[cfg(feature = "gecko")]
+            DisplayInside::MozBox => true,
+            _ => false,
+        }
+    }
+
+    /// Returns whether an element with this display type is a line
+    /// participant, which means it may lay its children on the same
+    /// line as itself.
+    pub fn is_line_participant(&self) -> bool {
+        match *self {
+            Display::Inline => true,
+            #[cfg(feature = "gecko")]
+            Display::Contents | Display::Ruby | Display::RubyBaseContainer => true,
+            _ => false,
+        }
+    }
+
+    /// Convert this display into an equivalent block display.
+    ///
+    /// Also used for :root style adjustments.
+    pub fn equivalent_block_display(&self, _is_root_element: bool) -> Self {
+        #[cfg(any(feature = "servo-layout-2020", feature = "gecko"))]
+        {
+            // Special handling for `contents` and `list-item`s on the root element.
+            if _is_root_element && (self.is_contents() || self.is_list_item()) {
+                return Display::Block;
+            }
+        }
+
+        match self.outside() {
+            DisplayOutside::Inline => {
+                let inside = match self.inside() {
+                    // `inline-block` blockifies to `block` rather than
+                    // `flow-root`, for legacy reasons.
+                    DisplayInside::FlowRoot => DisplayInside::Flow,
+                    inside => inside,
+                };
+                Display::from3(DisplayOutside::Block, inside, self.is_list_item())
+            },
+            DisplayOutside::Block | DisplayOutside::XUL | DisplayOutside::None => *self,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            _ => Display::Block,
+        }
+    }
+
+    /// Convert this display into an equivalent inline-outside display.
+    /// https://drafts.csswg.org/css-display/#inlinify
+    #[cfg(feature = "gecko")]
+    pub fn inlinify(&self) -> Self {
+        match self.outside() {
+            DisplayOutside::Block => {
+                let inside = match self.inside() {
+                    // `display: block` inlinifies to `display: inline-block`,
+                    // rather than `inline`, for legacy reasons.
+                    DisplayInside::Flow => DisplayInside::FlowRoot,
+                    inside => inside,
+                };
+                Display::from3(DisplayOutside::Inline, inside, self.is_list_item())
+            },
+            _ => *self,
+        }
+    }
+
+    /// Returns true if the value is `Contents`
+    #[inline]
+    pub fn is_contents(&self) -> bool {
+        match *self {
+            #[cfg(any(feature = "servo-layout-2020", feature = "gecko"))]
+            Display::Contents => true,
+            _ => false,
+        }
+    }
+
+    /// Returns true if the value is `None`
+    #[inline]
+    pub fn is_none(&self) -> bool {
+        *self == Display::None
+    }
+}
+
+impl ToCss for Display {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        let outside = self.outside();
+        let inside = self.inside();
+        match *self {
+            Display::Block | Display::Inline => outside.to_css(dest),
+            Display::InlineBlock => dest.write_str("inline-block"),
+            #[cfg(feature = "gecko")]
+            Display::WebkitInlineBox => dest.write_str("-webkit-inline-box"),
+            #[cfg(feature = "gecko")]
+            Display::MozInlineBox => dest.write_str("-moz-inline-box"),
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            Display::TableCaption => dest.write_str("table-caption"),
+            _ => match (outside, inside) {
+                #[cfg(feature = "gecko")]
+                (DisplayOutside::Inline, DisplayInside::Grid) => dest.write_str("inline-grid"),
+                (DisplayOutside::Inline, DisplayInside::Flex) => dest.write_str("inline-flex"),
+                #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+                (DisplayOutside::Inline, DisplayInside::Table) => dest.write_str("inline-table"),
+                #[cfg(feature = "gecko")]
+                (DisplayOutside::Block, DisplayInside::Ruby) => dest.write_str("block ruby"),
+                (_, inside) => {
+                    if self.is_list_item() {
+                        if outside != DisplayOutside::Block {
+                            outside.to_css(dest)?;
+                            dest.write_str(" ")?;
+                        }
+                        if inside != DisplayInside::Flow {
+                            inside.to_css(dest)?;
+                            dest.write_str(" ")?;
+                        }
+                        dest.write_str("list-item")
+                    } else {
+                        inside.to_css(dest)
+                    }
+                },
+            },
+        }
+    }
+}
+
+/// <display-inside> = flow | flow-root | table | flex | grid | ruby
+/// https://drafts.csswg.org/css-display/#typedef-display-inside
+fn parse_display_inside<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<DisplayInside, ParseError<'i>> {
+    Ok(try_match_ident_ignore_ascii_case! { input,
+        "flow" => DisplayInside::Flow,
+        "flex" if flexbox_enabled() => DisplayInside::Flex,
+        #[cfg(any(feature = "servo-layout-2020", feature = "gecko"))]
+        "flow-root" => DisplayInside::FlowRoot,
+        #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+        "table" => DisplayInside::Table,
+        #[cfg(feature = "gecko")]
+        "grid" => DisplayInside::Grid,
+        #[cfg(feature = "gecko")]
+        "ruby" => DisplayInside::Ruby,
+    })
+}
+
+/// <display-outside> = block | inline | run-in
+/// https://drafts.csswg.org/css-display/#typedef-display-outside
+fn parse_display_outside<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<DisplayOutside, ParseError<'i>> {
+    Ok(try_match_ident_ignore_ascii_case! { input,
+        "block" => DisplayOutside::Block,
+        "inline" => DisplayOutside::Inline,
+        // FIXME(bug 2056): not supported in layout yet:
+        //"run-in" => DisplayOutside::RunIn,
+    })
+}
+
+/// (flow | flow-root)?
+fn parse_display_inside_for_list_item<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<DisplayInside, ParseError<'i>> {
+    Ok(try_match_ident_ignore_ascii_case! { input,
+        "flow" => DisplayInside::Flow,
+        #[cfg(feature = "gecko")]
+        "flow-root" => DisplayInside::FlowRoot,
+    })
+}
+/// Test a <display-inside> Result for same values as above.
+fn is_valid_inside_for_list_item<'i>(inside: &Result<DisplayInside, ParseError<'i>>) -> bool {
+    match inside {
+        Ok(DisplayInside::Flow) => true,
+        #[cfg(feature = "gecko")]
+        Ok(DisplayInside::FlowRoot) => true,
+        _ => false,
+    }
+}
+
+/// Parse `list-item`.
+fn parse_list_item<'i, 't>(input: &mut Parser<'i, 't>) -> Result<(), ParseError<'i>> {
+    Ok(input.expect_ident_matching("list-item")?)
+}
+
+impl Parse for Display {
+    #[allow(unused)] // `context` isn't used for servo-2020 for now
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Display, ParseError<'i>> {
+        // Parse all combinations of <display-inside/outside>? and `list-item`? first.
+        let mut got_list_item = input.try_parse(parse_list_item).is_ok();
+        let mut inside = if got_list_item {
+            input.try_parse(parse_display_inside_for_list_item)
+        } else {
+            input.try_parse(parse_display_inside)
+        };
+        // <display-listitem> = <display-outside>? && [ flow | flow-root ]? && list-item
+        // https://drafts.csswg.org/css-display/#typedef-display-listitem
+        if !got_list_item && is_valid_inside_for_list_item(&inside) {
+            got_list_item = input.try_parse(parse_list_item).is_ok();
+        }
+        let outside = input.try_parse(parse_display_outside);
+        if outside.is_ok() {
+            if !got_list_item && (inside.is_err() || is_valid_inside_for_list_item(&inside)) {
+                got_list_item = input.try_parse(parse_list_item).is_ok();
+            }
+            if inside.is_err() {
+                inside = if got_list_item {
+                    input.try_parse(parse_display_inside_for_list_item)
+                } else {
+                    input.try_parse(parse_display_inside)
+                };
+                if !got_list_item && is_valid_inside_for_list_item(&inside) {
+                    got_list_item = input.try_parse(parse_list_item).is_ok();
+                }
+            }
+        }
+        if got_list_item || inside.is_ok() || outside.is_ok() {
+            let inside = inside.unwrap_or(DisplayInside::Flow);
+            let outside = outside.unwrap_or(match inside {
+                // "If <display-outside> is omitted, the element’s outside display type
+                // defaults to block — except for ruby, which defaults to inline."
+                // https://drafts.csswg.org/css-display/#inside-model
+                #[cfg(feature = "gecko")]
+                DisplayInside::Ruby => DisplayOutside::Inline,
+                _ => DisplayOutside::Block,
+            });
+            return Ok(Display::from3(outside, inside, got_list_item));
+        }
+
+        // Now parse the single-keyword `display` values.
+        Ok(try_match_ident_ignore_ascii_case! { input,
+            "none" => Display::None,
+            #[cfg(any(feature = "servo-layout-2020", feature = "gecko"))]
+            "contents" => Display::Contents,
+            "inline-block" => Display::InlineBlock,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "inline-table" => Display::InlineTable,
+            "-webkit-flex" if flexbox_enabled() => Display::Flex,
+            "inline-flex" | "-webkit-inline-flex" if flexbox_enabled() => Display::InlineFlex,
+            #[cfg(feature = "gecko")]
+            "inline-grid" => Display::InlineGrid,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-caption" => Display::TableCaption,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-row-group" => Display::TableRowGroup,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-header-group" => Display::TableHeaderGroup,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-footer-group" => Display::TableFooterGroup,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-column" => Display::TableColumn,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-column-group" => Display::TableColumnGroup,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-row" => Display::TableRow,
+            #[cfg(any(feature = "servo-layout-2013", feature = "gecko"))]
+            "table-cell" => Display::TableCell,
+            #[cfg(feature = "gecko")]
+            "ruby-base" => Display::RubyBase,
+            #[cfg(feature = "gecko")]
+            "ruby-base-container" => Display::RubyBaseContainer,
+            #[cfg(feature = "gecko")]
+            "ruby-text" => Display::RubyText,
+            #[cfg(feature = "gecko")]
+            "ruby-text-container" => Display::RubyTextContainer,
+            #[cfg(feature = "gecko")]
+            "-webkit-box" => Display::WebkitBox,
+            #[cfg(feature = "gecko")]
+            "-webkit-inline-box" => Display::WebkitInlineBox,
+            #[cfg(feature = "gecko")]
+            "-moz-box" if moz_display_values_enabled(context) => Display::MozBox,
+            #[cfg(feature = "gecko")]
+            "-moz-inline-box" if moz_display_values_enabled(context) => Display::MozInlineBox,
+        })
+    }
+}
+
+impl SpecifiedValueInfo for Display {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&[
+            "block",
+            "contents",
+            "flex",
+            "flow-root",
+            "flow-root list-item",
+            "grid",
+            "inline",
+            "inline-block",
+            "inline-flex",
+            "inline-grid",
+            "inline-table",
+            "inline list-item",
+            "inline flow-root list-item",
+            "list-item",
+            "none",
+            "block ruby",
+            "ruby",
+            "ruby-base",
+            "ruby-base-container",
+            "ruby-text",
+            "ruby-text-container",
+            "table",
+            "table-caption",
+            "table-cell",
+            "table-column",
+            "table-column-group",
+            "table-footer-group",
+            "table-header-group",
+            "table-row",
+            "table-row-group",
+            "-webkit-box",
+            "-webkit-inline-box",
+        ]);
+    }
+}
+
+/// A specified value for the `contain-intrinsic-size` property.
+pub type ContainIntrinsicSize = GenericContainIntrinsicSize<NonNegativeLength>;
+
+/// A specified value for the `line-clamp` property.
+pub type LineClamp = GenericLineClamp<Integer>;
+
+/// A specified value for the `vertical-align` property.
+pub type VerticalAlign = GenericVerticalAlign<LengthPercentage>;
+
+impl Parse for VerticalAlign {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(lp) =
+            input.try_parse(|i| LengthPercentage::parse_quirky(context, i, AllowQuirks::Yes))
+        {
+            return Ok(GenericVerticalAlign::Length(lp));
+        }
+
+        Ok(GenericVerticalAlign::Keyword(VerticalAlignKeyword::parse(
+            input,
+        )?))
+    }
+}
+
+/// https://drafts.csswg.org/css-animations/#animation-iteration-count
+pub type AnimationIterationCount = GenericAnimationIterationCount<Number>;
+
+impl Parse for AnimationIterationCount {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut ::cssparser::Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("infinite"))
+            .is_ok()
+        {
+            return Ok(GenericAnimationIterationCount::Infinite);
+        }
+
+        let number = Number::parse_non_negative(context, input)?;
+        Ok(GenericAnimationIterationCount::Number(number))
+    }
+}
+
+impl AnimationIterationCount {
+    /// Returns the value `1.0`.
+    #[inline]
+    pub fn one() -> Self {
+        GenericAnimationIterationCount::Number(Number::new(1.0))
+    }
+}
+
+/// A value for the `animation-name` property.
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[value_info(other_values = "none")]
+pub struct AnimationName(pub KeyframesName);
+
+impl AnimationName {
+    /// Get the name of the animation as an `Atom`.
+    pub fn as_atom(&self) -> Option<&Atom> {
+        if self.is_none() {
+            return None;
+        }
+        Some(self.0.as_atom())
+    }
+
+    /// Returns the `none` value.
+    pub fn none() -> Self {
+        AnimationName(KeyframesName::none())
+    }
+
+    /// Returns whether this is the none value.
+    pub fn is_none(&self) -> bool {
+        self.0.is_none()
+    }
+}
+
+impl Parse for AnimationName {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(name) = input.try_parse(|input| KeyframesName::parse(context, input)) {
+            return Ok(AnimationName(name));
+        }
+
+        input.expect_ident_matching("none")?;
+        Ok(AnimationName(KeyframesName::none()))
+    }
+}
+
+/// A value for the <Scroller> used in scroll().
+///
+/// https://drafts.csswg.org/scroll-animations-1/rewrite#typedef-scroller
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum Scroller {
+    /// The nearest ancestor scroll container. (Default.)
+    Nearest,
+    /// The document viewport as the scroll container.
+    Root,
+    // FIXME: Bug 1764450: Once we support container-name CSS property (Bug 1744224), we may add
+    // <custom-ident> here, based on the result of the spec issue:
+    // https://github.com/w3c/csswg-drafts/issues/7046
+}
+
+impl Default for Scroller {
+    fn default() -> Self {
+        Self::Nearest
+    }
+}
+
+/// A value for the <Axis> used in scroll().
+///
+/// https://drafts.csswg.org/scroll-animations-1/rewrite#typedef-axis
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ScrollAxis {
+    /// The block axis of the scroll container. (Default.)
+    Block = 0,
+    /// The inline axis of the scroll container.
+    Inline = 1,
+    /// The vertical block axis of the scroll container.
+    Vertical = 2,
+    /// The horizontal axis of the scroll container.
+    Horizontal = 3,
+}
+
+impl Default for ScrollAxis {
+    fn default() -> Self {
+        Self::Block
+    }
+}
+
+#[inline]
+fn is_default<T: Default + PartialEq>(value: &T) -> bool {
+    *value == Default::default()
+}
+
+/// A value for the <single-animation-timeline>.
+///
+/// https://drafts.csswg.org/css-animations-2/#typedef-single-animation-timeline
+/// cbindgen:private-default-tagged-enum-constructor=false
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum AnimationTimeline {
+    /// Use default timeline. The animation’s timeline is a DocumentTimeline.
+    Auto,
+    /// The scroll-timeline name.
+    /// https://drafts.csswg.org/scroll-animations-1/#scroll-timelines-named
+    Timeline(TimelineName),
+    /// The scroll() notation.
+    /// https://drafts.csswg.org/scroll-animations-1/#scroll-notation
+    #[css(function)]
+    Scroll(
+        #[css(skip_if = "is_default")] ScrollAxis,
+        #[css(skip_if = "is_default")] Scroller,
+    ),
+}
+
+impl AnimationTimeline {
+    /// Returns the `auto` value.
+    pub fn auto() -> Self {
+        Self::Auto
+    }
+
+    /// Returns true if it is auto (i.e. the default value).
+    pub fn is_auto(&self) -> bool {
+        matches!(self, Self::Auto)
+    }
+}
+
+impl Parse for AnimationTimeline {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // We are using the same parser for TimelineName and KeyframesName, but animation-timeline
+        // accepts "auto", so need to manually parse this. (We can not derive
+        // Parse because TimelineName excludes only the "none" keyword).
+        //
+        // FIXME: Bug 1733260: we may drop None based on the spec issue:
+        // https://github.com/w3c/csswg-drafts/issues/6674
+        //
+        // If `none` is removed, then we could potentially shrink this the same
+        // way we deal with animation-name.
+        if input.try_parse(|i| i.expect_ident_matching("auto")).is_ok() {
+            return Ok(Self::Auto);
+        }
+
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(AnimationTimeline::Timeline(TimelineName::none()));
+        }
+
+        // https://drafts.csswg.org/scroll-animations-1/rewrite#scroll-notation
+        if input
+            .try_parse(|i| i.expect_function_matching("scroll"))
+            .is_ok()
+        {
+            return input.parse_nested_block(|i| {
+                Ok(Self::Scroll(
+                    i.try_parse(ScrollAxis::parse).unwrap_or(ScrollAxis::Block),
+                    i.try_parse(Scroller::parse).unwrap_or(Scroller::Nearest),
+                ))
+            });
+        }
+
+        TimelineName::parse(context, input).map(AnimationTimeline::Timeline)
+    }
+}
+
+/// A value for the scroll-timeline-name.
+///
+/// Note: The spec doesn't mention `auto` for scroll-timeline-name. However, `auto` is a keyword in
+/// animation-timeline, so we reject `auto` for scroll-timeline-name now.
+///
+/// https://drafts.csswg.org/scroll-animations-1/rewrite#scroll-timeline-name
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct ScrollTimelineName(pub TimelineName);
+
+impl ScrollTimelineName {
+    /// Returns the `none` value.
+    pub fn none() -> Self {
+        Self(TimelineName::none())
+    }
+}
+
+impl Parse for ScrollTimelineName {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(name) = input.try_parse(|input| TimelineName::parse(context, input)) {
+            return Ok(Self(name));
+        }
+
+        input.expect_ident_matching("none")?;
+        Ok(Self(TimelineName::none()))
+    }
+}
+
+/// https://drafts.csswg.org/css-scroll-snap-1/#snap-axis
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ScrollSnapAxis {
+    X,
+    Y,
+    Block,
+    Inline,
+    Both,
+}
+
+/// https://drafts.csswg.org/css-scroll-snap-1/#snap-strictness
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ScrollSnapStrictness {
+    #[css(skip)]
+    None, // Used to represent scroll-snap-type: none.  It's not parsed.
+    Mandatory,
+    Proximity,
+}
+
+/// https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-type
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct ScrollSnapType {
+    axis: ScrollSnapAxis,
+    strictness: ScrollSnapStrictness,
+}
+
+impl ScrollSnapType {
+    /// Returns `none`.
+    #[inline]
+    pub fn none() -> Self {
+        Self {
+            axis: ScrollSnapAxis::Both,
+            strictness: ScrollSnapStrictness::None,
+        }
+    }
+}
+
+impl Parse for ScrollSnapType {
+    /// none | [ x | y | block | inline | both ] [ mandatory | proximity ]?
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("none"))
+            .is_ok()
+        {
+            return Ok(ScrollSnapType::none());
+        }
+
+        let axis = ScrollSnapAxis::parse(input)?;
+        let strictness = input
+            .try_parse(ScrollSnapStrictness::parse)
+            .unwrap_or(ScrollSnapStrictness::Proximity);
+        Ok(Self { axis, strictness })
+    }
+}
+
+impl ToCss for ScrollSnapType {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.strictness == ScrollSnapStrictness::None {
+            return dest.write_str("none");
+        }
+        self.axis.to_css(dest)?;
+        if self.strictness != ScrollSnapStrictness::Proximity {
+            dest.write_str(" ")?;
+            self.strictness.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+/// Specified value of scroll-snap-align keyword value.
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ScrollSnapAlignKeyword {
+    None,
+    Start,
+    End,
+    Center,
+}
+
+/// https://drafts.csswg.org/css-scroll-snap-1/#scroll-snap-align
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct ScrollSnapAlign {
+    block: ScrollSnapAlignKeyword,
+    inline: ScrollSnapAlignKeyword,
+}
+
+impl ScrollSnapAlign {
+    /// Returns `none`.
+    #[inline]
+    pub fn none() -> Self {
+        ScrollSnapAlign {
+            block: ScrollSnapAlignKeyword::None,
+            inline: ScrollSnapAlignKeyword::None,
+        }
+    }
+}
+
+impl Parse for ScrollSnapAlign {
+    /// [ none | start | end | center ]{1,2}
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<ScrollSnapAlign, ParseError<'i>> {
+        let block = ScrollSnapAlignKeyword::parse(input)?;
+        let inline = input
+            .try_parse(ScrollSnapAlignKeyword::parse)
+            .unwrap_or(block);
+        Ok(ScrollSnapAlign { block, inline })
+    }
+}
+
+impl ToCss for ScrollSnapAlign {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        self.block.to_css(dest)?;
+        if self.block != self.inline {
+            dest.write_str(" ")?;
+            self.inline.to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ScrollSnapStop {
+    Normal,
+    Always,
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum OverscrollBehavior {
+    Auto,
+    Contain,
+    None,
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum OverflowAnchor {
+    Auto,
+    None,
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum OverflowClipBox {
+    PaddingBox,
+    ContentBox,
+}
+
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(comma)]
+#[repr(C)]
+/// Provides a rendering hint to the user agent, stating what kinds of changes
+/// the author expects to perform on the element.
+///
+/// `auto` is represented by an empty `features` list.
+///
+/// <https://drafts.csswg.org/css-will-change/#will-change>
+pub struct WillChange {
+    /// The features that are supposed to change.
+    ///
+    /// TODO(emilio): Consider using ArcSlice since we just clone them from the
+    /// specified value? That'd save an allocation, which could be worth it.
+    #[css(iterable, if_empty = "auto")]
+    features: crate::OwnedSlice<CustomIdent>,
+    /// A bitfield with the kind of change that the value will create, based
+    /// on the above field.
+    #[css(skip)]
+    bits: WillChangeBits,
+}
+
+impl WillChange {
+    #[inline]
+    /// Get default value of `will-change` as `auto`
+    pub fn auto() -> Self {
+        Self::default()
+    }
+}
+
+bitflags! {
+    /// The change bits that we care about.
+    #[derive(Default, MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[repr(C)]
+    pub struct WillChangeBits: u16 {
+        /// Whether a property which can create a stacking context **on any
+        /// box** will change.
+        const STACKING_CONTEXT_UNCONDITIONAL = 1 << 0;
+        /// Whether `transform` or related properties will change.
+        const TRANSFORM = 1 << 1;
+        /// Whether `scroll-position` will change.
+        const SCROLL = 1 << 2;
+        /// Whether `contain` will change.
+        const CONTAIN = 1 << 3;
+        /// Whether `opacity` will change.
+        const OPACITY = 1 << 4;
+        /// Whether `perspective` will change.
+        const PERSPECTIVE = 1 << 5;
+        /// Whether `z-index` will change.
+        const Z_INDEX = 1 << 6;
+        /// Whether any property which creates a containing block for non-svg
+        /// text frames will change.
+        const FIXPOS_CB_NON_SVG = 1 << 7;
+        /// Whether the position property will change.
+        const POSITION = 1 << 8;
+    }
+}
+
+fn change_bits_for_longhand(longhand: LonghandId) -> WillChangeBits {
+    match longhand {
+        LonghandId::Opacity => WillChangeBits::OPACITY,
+        LonghandId::Contain => WillChangeBits::CONTAIN,
+        LonghandId::Perspective => WillChangeBits::PERSPECTIVE,
+        LonghandId::Position => {
+            WillChangeBits::STACKING_CONTEXT_UNCONDITIONAL | WillChangeBits::POSITION
+        },
+        LonghandId::ZIndex => WillChangeBits::Z_INDEX,
+        LonghandId::Transform |
+        LonghandId::TransformStyle |
+        LonghandId::Translate |
+        LonghandId::Rotate |
+        LonghandId::Scale |
+        LonghandId::OffsetPath => WillChangeBits::TRANSFORM,
+        LonghandId::BackdropFilter | LonghandId::Filter => {
+            WillChangeBits::STACKING_CONTEXT_UNCONDITIONAL | WillChangeBits::FIXPOS_CB_NON_SVG
+        },
+        LonghandId::MixBlendMode |
+        LonghandId::Isolation |
+        LonghandId::MaskImage |
+        LonghandId::ClipPath => WillChangeBits::STACKING_CONTEXT_UNCONDITIONAL,
+        _ => WillChangeBits::empty(),
+    }
+}
+
+fn change_bits_for_maybe_property(ident: &str, context: &ParserContext) -> WillChangeBits {
+    let id = match PropertyId::parse_ignoring_rule_type(ident, context) {
+        Ok(id) => id,
+        Err(..) => return WillChangeBits::empty(),
+    };
+
+    match id.as_shorthand() {
+        Ok(shorthand) => shorthand
+            .longhands()
+            .fold(WillChangeBits::empty(), |flags, p| {
+                flags | change_bits_for_longhand(p)
+            }),
+        Err(PropertyDeclarationId::Longhand(longhand)) => change_bits_for_longhand(longhand),
+        Err(PropertyDeclarationId::Custom(..)) => WillChangeBits::empty(),
+    }
+}
+
+impl Parse for WillChange {
+    /// auto | <animateable-feature>#
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("auto"))
+            .is_ok()
+        {
+            return Ok(Self::default());
+        }
+
+        let mut bits = WillChangeBits::empty();
+        let custom_idents = input.parse_comma_separated(|i| {
+            let location = i.current_source_location();
+            let parser_ident = i.expect_ident()?;
+            let ident = CustomIdent::from_ident(
+                location,
+                parser_ident,
+                &["will-change", "none", "all", "auto"],
+            )?;
+
+            if context.in_ua_sheet() && ident.0 == atom!("-moz-fixed-pos-containing-block") {
+                bits |= WillChangeBits::FIXPOS_CB_NON_SVG;
+            } else if ident.0 == atom!("scroll-position") {
+                bits |= WillChangeBits::SCROLL;
+            } else {
+                bits |= change_bits_for_maybe_property(&parser_ident, context);
+            }
+            Ok(ident)
+        })?;
+
+        Ok(Self {
+            features: custom_idents.into(),
+            bits,
+        })
+    }
+}
+
+bitflags! {
+    /// Values for the `touch-action` property.
+    #[derive(MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToCss, ToResolvedValue, ToShmem, Parse)]
+    #[css(bitflags(single = "none,auto,manipulation", mixed = "pan-x,pan-y,pinch-zoom"))]
+    #[repr(C)]
+    pub struct TouchAction: u8 {
+        /// `none` variant
+        const NONE = 1 << 0;
+        /// `auto` variant
+        const AUTO = 1 << 1;
+        /// `pan-x` variant
+        const PAN_X = 1 << 2;
+        /// `pan-y` variant
+        const PAN_Y = 1 << 3;
+        /// `manipulation` variant
+        const MANIPULATION = 1 << 4;
+        /// `pinch-zoom` variant
+        const PINCH_ZOOM = 1 << 5;
+    }
+}
+
+impl TouchAction {
+    #[inline]
+    /// Get default `touch-action` as `auto`
+    pub fn auto() -> TouchAction {
+        TouchAction::AUTO
+    }
+}
+
+bitflags! {
+    #[derive(MallocSizeOf, Parse, SpecifiedValueInfo, ToComputedValue, ToCss, ToResolvedValue, ToShmem)]
+    #[css(bitflags(single = "none,strict,content", mixed="size,layout,style,paint,inline-size", overlapping_bits))]
+    #[repr(C)]
+    /// Constants for contain: https://drafts.csswg.org/css-contain/#contain-property
+    pub struct Contain: u8 {
+        /// `none` variant, just for convenience.
+        const NONE = 0;
+        /// `inline-size` variant, turns on single-axis inline size containment
+        const INLINE_SIZE = 1 << 0;
+        /// `block-size` variant, turns on single-axis block size containment, internal only
+        const BLOCK_SIZE = 1 << 1;
+        /// `layout` variant, turns on layout containment
+        const LAYOUT = 1 << 2;
+        /// `style` variant, turns on style containment
+        const STYLE = 1 << 3;
+        /// `paint` variant, turns on paint containment
+        const PAINT = 1 << 4;
+        /// 'size' variant, turns on size containment
+        const SIZE = 1 << 5 | Contain::INLINE_SIZE.bits | Contain::BLOCK_SIZE.bits;
+        /// `content` variant, turns on layout and paint containment
+        const CONTENT = 1 << 6 | Contain::LAYOUT.bits | Contain::STYLE.bits | Contain::PAINT.bits;
+        /// `strict` variant, turns on all types of containment
+        const STRICT = 1 << 7 | Contain::LAYOUT.bits | Contain::STYLE.bits | Contain::PAINT.bits | Contain::SIZE.bits;
+    }
+}
+
+impl Parse for ContainIntrinsicSize {
+    /// none | <length> | auto <length>
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(l) = input.try_parse(|i| NonNegativeLength::parse(context, i)) {
+            return Ok(Self::Length(l));
+        }
+
+        if input.try_parse(|i| i.expect_ident_matching("auto")).is_ok() {
+            let l = NonNegativeLength::parse(context, input)?;
+            return Ok(Self::AutoLength(l));
+        }
+
+        input.expect_ident_matching("none")?;
+        Ok(Self::None)
+    }
+}
+
+impl Parse for LineClamp {
+    /// none | <positive-integer>
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(i) =
+            input.try_parse(|i| crate::values::specified::PositiveInteger::parse(context, i))
+        {
+            return Ok(Self(i.0));
+        }
+        input.expect_ident_matching("none")?;
+        Ok(Self::none())
+    }
+}
+
+/// https://drafts.csswg.org/css-contain-2/#content-visibility
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ContentVisibility {
+    /// `auto` variant, the element turns on layout containment, style containment, and paint
+    /// containment. In addition, if the element is not relevant to the user (such as by being
+    /// offscreen) it also skips its content
+    Auto,
+    /// `hidden` variant, the element skips its content
+    Hidden,
+    /// 'visible' variant, no effect
+    Visible,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToCss, Parse, ToResolvedValue, ToShmem)]
+#[repr(u8)]
+#[allow(missing_docs)]
+/// https://drafts.csswg.org/css-contain-3/#container-type
+pub enum ContainerType {
+    /// The `normal` variant.
+    Normal,
+    /// The `inline-size` variant.
+    InlineSize,
+    /// The `size` variant.
+    Size,
+}
+
+impl ContainerType {
+    /// Is this container-type: normal?
+    pub fn is_normal(self) -> bool {
+        self == Self::Normal
+    }
+
+    /// Is this type containing size in any way?
+    pub fn is_size_container_type(self) -> bool {
+        !self.is_normal()
+    }
+}
+
+/// https://drafts.csswg.org/css-contain-3/#container-name
+#[repr(transparent)]
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct ContainerName(#[css(iterable, if_empty = "none")] pub crate::OwnedSlice<CustomIdent>);
+
+impl ContainerName {
+    /// Return the `none` value.
+    pub fn none() -> Self {
+        Self(Default::default())
+    }
+
+    /// Returns whether this is the `none` value.
+    pub fn is_none(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    fn parse_internal<'i>(
+        input: &mut Parser<'i, '_>,
+        for_query: bool,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut idents = vec![];
+        let location = input.current_source_location();
+        let first = input.expect_ident()?;
+        if !for_query && first.eq_ignore_ascii_case("none") {
+            return Ok(Self::none());
+        }
+        const DISALLOWED_CONTAINER_NAMES: &'static [&'static str] =
+            &["none", "not", "or", "and"];
+        idents.push(CustomIdent::from_ident(
+            location,
+            first,
+            DISALLOWED_CONTAINER_NAMES,
+        )?);
+        if !for_query {
+            while let Ok(name) = input.try_parse(|input| {
+                let ident = input.expect_ident()?;
+                CustomIdent::from_ident(location, &ident, DISALLOWED_CONTAINER_NAMES)
+            }) {
+                idents.push(name);
+            }
+        }
+        Ok(ContainerName(idents.into()))
+    }
+
+    /// https://github.com/w3c/csswg-drafts/issues/7203
+    /// Only a single name allowed in @container rule.
+    /// Disallow none for container-name in @container rule.
+    pub fn parse_for_query<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(input, /* for_query = */ true)
+    }
+}
+
+impl Parse for ContainerName {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(input, /* for_query = */ false)
+    }
+}
+
+/// A specified value for the `perspective` property.
+pub type Perspective = GenericPerspective<NonNegativeLength>;
+
+/// A given transition property, that is either `All`, a longhand or shorthand
+/// property, or an unsupported or custom property.
+#[derive(
+    Clone, Debug, Eq, Hash, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+pub enum TransitionProperty {
+    /// A shorthand.
+    Shorthand(ShorthandId),
+    /// A longhand transitionable property.
+    Longhand(LonghandId),
+    /// A custom property.
+    Custom(CustomPropertyName),
+    /// Unrecognized property which could be any non-transitionable, custom property, or
+    /// unknown property.
+    Unsupported(CustomIdent),
+}
+
+impl ToCss for TransitionProperty {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        use crate::values::serialize_atom_name;
+        match *self {
+            TransitionProperty::Shorthand(ref s) => s.to_css(dest),
+            TransitionProperty::Longhand(ref l) => l.to_css(dest),
+            TransitionProperty::Custom(ref name) => {
+                dest.write_str("--")?;
+                serialize_atom_name(name, dest)
+            },
+            TransitionProperty::Unsupported(ref i) => i.to_css(dest),
+        }
+    }
+}
+
+impl Parse for TransitionProperty {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let ident = input.expect_ident()?;
+
+        let id = match PropertyId::parse_ignoring_rule_type(&ident, context) {
+            Ok(id) => id,
+            Err(..) => {
+                return Ok(TransitionProperty::Unsupported(CustomIdent::from_ident(
+                    location,
+                    ident,
+                    &["none"],
+                )?));
+            },
+        };
+
+        Ok(match id.as_shorthand() {
+            Ok(s) => TransitionProperty::Shorthand(s),
+            Err(longhand_or_custom) => match longhand_or_custom {
+                PropertyDeclarationId::Longhand(id) => TransitionProperty::Longhand(id),
+                PropertyDeclarationId::Custom(custom) => TransitionProperty::Custom(custom.clone()),
+            },
+        })
+    }
+}
+
+impl SpecifiedValueInfo for TransitionProperty {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        // `transition-property` can actually accept all properties and
+        // arbitrary identifiers, but `all` is a special one we'd like
+        // to list.
+        f(&["all"]);
+    }
+}
+
+impl TransitionProperty {
+    /// Returns `all`.
+    #[inline]
+    pub fn all() -> Self {
+        TransitionProperty::Shorthand(ShorthandId::All)
+    }
+
+    /// Convert TransitionProperty to nsCSSPropertyID.
+    #[cfg(feature = "gecko")]
+    pub fn to_nscsspropertyid(
+        &self,
+    ) -> Result<crate::gecko_bindings::structs::nsCSSPropertyID, ()> {
+        Ok(match *self {
+            TransitionProperty::Shorthand(ShorthandId::All) => {
+                crate::gecko_bindings::structs::nsCSSPropertyID::eCSSPropertyExtra_all_properties
+            },
+            TransitionProperty::Shorthand(ref id) => id.to_nscsspropertyid(),
+            TransitionProperty::Longhand(ref id) => id.to_nscsspropertyid(),
+            TransitionProperty::Custom(..) | TransitionProperty::Unsupported(..) => return Err(()),
+        })
+    }
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+/// https://drafts.csswg.org/css-box/#propdef-float
+pub enum Float {
+    Left,
+    Right,
+    None,
+    // https://drafts.csswg.org/css-logical-props/#float-clear
+    InlineStart,
+    InlineEnd,
+}
+
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+/// https://drafts.csswg.org/css2/#propdef-clear
+pub enum Clear {
+    None,
+    Left,
+    Right,
+    Both,
+    // https://drafts.csswg.org/css-logical-props/#float-clear
+    InlineStart,
+    InlineEnd,
+}
+
+/// https://drafts.csswg.org/css-ui/#propdef-resize
+#[allow(missing_docs)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+pub enum Resize {
+    None,
+    Both,
+    Horizontal,
+    Vertical,
+    // https://drafts.csswg.org/css-logical-1/#resize
+    Inline,
+    Block,
+}
+
+/// The value for the `appearance` property.
+///
+/// https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-appearance
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum Appearance {
+    /// No appearance at all.
+    None,
+    /// Default appearance for the element.
+    ///
+    /// This value doesn't make sense for -moz-default-appearance, but we don't bother to guard
+    /// against parsing it.
+    Auto,
+    /// A searchfield.
+    Searchfield,
+    /// A multi-line text field, e.g. HTML <textarea>.
+    #[parse(aliases = "textfield-multiline")]
+    Textarea,
+    /// A checkbox element.
+    Checkbox,
+    /// A radio element within a radio group.
+    Radio,
+    /// A dropdown list.
+    Menulist,
+    /// List boxes.
+    Listbox,
+    /// A horizontal meter bar.
+    #[parse(aliases = "meterbar")]
+    Meter,
+    /// A horizontal progress bar.
+    #[parse(aliases = "progressbar")]
+    ProgressBar,
+    /// A typical dialog button.
+    Button,
+    /// A single-line text field, e.g. HTML <input type=text>.
+    Textfield,
+    /// The dropdown button(s) that open up a dropdown list.
+    MenulistButton,
+    /// Various arrows that go in buttons
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ButtonArrowDown,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ButtonArrowNext,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ButtonArrowPrevious,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ButtonArrowUp,
+    /// A dual toolbar button (e.g., a Back button with a dropdown)
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Dualbutton,
+    /// A groupbox.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Groupbox,
+    /// Menu Bar background
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menubar,
+    /// <menu> and <menuitem> appearances
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menuitem,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Checkmenuitem,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Radiomenuitem,
+    /// For text on non-iconic menuitems only
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menuitemtext,
+    /// The text part of a dropdown list, to left of button.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MenulistText,
+    /// Menu Popup background.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menupopup,
+    /// menu checkbox/radio appearances
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menucheckbox,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menuradio,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menuseparator,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menuarrow,
+    /// An image in the menu gutter, like in bookmarks or history.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Menuimage,
+    /// The meter bar's meter indicator.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Meterchunk,
+    /// The "arrowed" part of the dropdown button that open up a dropdown list.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMenulistArrowButton,
+    /// For HTML's <input type=number>
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    NumberInput,
+    /// The progress bar's progress indicator
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Progresschunk,
+    /// A generic container that always repaints on state changes. This is a
+    /// hack to make XUL checkboxes and radio buttons work.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    CheckboxContainer,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    RadioContainer,
+    /// The label part of a checkbox or radio button, used for painting a focus
+    /// outline.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    CheckboxLabel,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    RadioLabel,
+    /// nsRangeFrame and its subparts
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Range,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    RangeThumb,
+    /// The resizer background area in a status bar for the resizer widget in
+    /// the corner of a window.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Resizerpanel,
+    /// The resizer itself.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Resizer,
+    /// The scrollbar slider
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarHorizontal,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarVertical,
+    /// A scrollbar button (up/down/left/right).
+    /// Keep these in order (some code casts these values to `int` in order to
+    /// compare them against each other).
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarbuttonUp,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarbuttonDown,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarbuttonLeft,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarbuttonRight,
+    /// The scrollbar thumb.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarthumbHorizontal,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbarthumbVertical,
+    /// The scrollbar track.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbartrackHorizontal,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ScrollbartrackVertical,
+    /// The scroll corner
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Scrollcorner,
+    /// A separator.  Can be horizontal or vertical.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Separator,
+    /// A spin control (up/down control for time/date pickers).
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Spinner,
+    /// The up button of a spin control.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    SpinnerUpbutton,
+    /// The down button of a spin control.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    SpinnerDownbutton,
+    /// The textfield of a spin control
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    SpinnerTextfield,
+    /// A splitter.  Can be horizontal or vertical.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Splitter,
+    /// A status bar in a main application window.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Statusbar,
+    /// A single pane of a status bar.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Statusbarpanel,
+    /// A single tab in a tab widget.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Tab,
+    /// A single pane (inside the tabpanels container).
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Tabpanel,
+    /// The tab panels container.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Tabpanels,
+    /// The tabs scroll arrows (left/right).
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    TabScrollArrowBack,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    TabScrollArrowForward,
+    /// A toolbar in an application window.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Toolbar,
+    /// A single toolbar button (with no associated dropdown).
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Toolbarbutton,
+    /// The dropdown portion of a toolbar button
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    ToolbarbuttonDropdown,
+    /// The gripper for a toolbar.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Toolbargripper,
+    /// The toolbox that contains the toolbars.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Toolbox,
+    /// A tooltip.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Tooltip,
+    /// A listbox or tree widget header
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treeheader,
+    /// An individual header cell
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treeheadercell,
+    /// The sort arrow for a header.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treeheadersortarrow,
+    /// A tree item.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treeitem,
+    /// A tree widget branch line
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treeline,
+    /// A tree widget twisty.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treetwisty,
+    /// Open tree widget twisty.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treetwistyopen,
+    /// A tree widget.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Treeview,
+    /// Window and dialog backgrounds.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Window,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    Dialog,
+
+    /// Vista Rebars.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWinCommunicationsToolbox,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWinMediaToolbox,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWinBrowsertabbarToolbox,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWinBorderlessGlass,
+    /// -moz-apperance style used in setting proper glass margins.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWinExcludeGlass,
+
+    /// Mac help button.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMacHelpButton,
+
+    /// Windows themed window frame elements.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowButtonBox,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowButtonBoxMaximized,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowButtonClose,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowButtonMaximize,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowButtonMinimize,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowButtonRestore,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowTitlebar,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozWindowTitlebarMaximized,
+
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMacActiveSourceListSelection,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMacDisclosureButtonClosed,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMacDisclosureButtonOpen,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMacSourceList,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMacSourceListSelection,
+
+    /// A themed focus outline (for outline:auto).
+    ///
+    /// This isn't exposed to CSS at all, just here for convenience.
+    #[css(skip)]
+    FocusOutline,
+
+    /// A dummy variant that should be last to let the GTK widget do hackery.
+    #[css(skip)]
+    Count,
+}
+
+/// A kind of break between two boxes.
+///
+/// https://drafts.csswg.org/css-break/#break-between
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum BreakBetween {
+    Always,
+    Auto,
+    Page,
+    Avoid,
+    Left,
+    Right,
+}
+
+impl BreakBetween {
+    /// Parse a legacy break-between value for `page-break-{before,after}`.
+    ///
+    /// See https://drafts.csswg.org/css-break/#page-break-properties.
+    #[inline]
+    pub(crate) fn parse_legacy<'i>(
+        _: &ParserContext,
+        input: &mut Parser<'i, '_>,
+    ) -> Result<Self, ParseError<'i>> {
+        let break_value = BreakBetween::parse(input)?;
+        match break_value {
+            BreakBetween::Always => Ok(BreakBetween::Page),
+            BreakBetween::Auto | BreakBetween::Avoid | BreakBetween::Left | BreakBetween::Right => {
+                Ok(break_value)
+            },
+            BreakBetween::Page => {
+                Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+            },
+        }
+    }
+
+    /// Serialize a legacy break-between value for `page-break-*`.
+    ///
+    /// See https://drafts.csswg.org/css-break/#page-break-properties.
+    pub(crate) fn to_css_legacy<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            BreakBetween::Auto | BreakBetween::Avoid | BreakBetween::Left | BreakBetween::Right => {
+                self.to_css(dest)
+            },
+            BreakBetween::Page => dest.write_str("always"),
+            BreakBetween::Always => Ok(()),
+        }
+    }
+}
+
+/// A kind of break within a box.
+///
+/// https://drafts.csswg.org/css-break/#break-within
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum BreakWithin {
+    Auto,
+    Avoid,
+    AvoidPage,
+    AvoidColumn,
+}
+
+impl BreakWithin {
+    /// Parse a legacy break-between value for `page-break-inside`.
+    ///
+    /// See https://drafts.csswg.org/css-break/#page-break-properties.
+    #[inline]
+    pub(crate) fn parse_legacy<'i>(
+        _: &ParserContext,
+        input: &mut Parser<'i, '_>,
+    ) -> Result<Self, ParseError<'i>> {
+        let break_value = BreakWithin::parse(input)?;
+        match break_value {
+            BreakWithin::Auto | BreakWithin::Avoid => Ok(break_value),
+            BreakWithin::AvoidPage | BreakWithin::AvoidColumn => {
+                Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+            },
+        }
+    }
+
+    /// Serialize a legacy break-between value for `page-break-inside`.
+    ///
+    /// See https://drafts.csswg.org/css-break/#page-break-properties.
+    pub(crate) fn to_css_legacy<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            BreakWithin::Auto | BreakWithin::Avoid => self.to_css(dest),
+            BreakWithin::AvoidPage | BreakWithin::AvoidColumn => Ok(()),
+        }
+    }
+}
+
+/// The value for the `overflow-x` / `overflow-y` properties.
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum Overflow {
+    Visible,
+    Hidden,
+    Scroll,
+    Auto,
+    #[cfg(feature = "gecko")]
+    Clip,
+}
+
+// This can be derived once we remove or keep `-moz-hidden-unscrollable`
+// indefinitely.
+impl Parse for Overflow {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(try_match_ident_ignore_ascii_case! { input,
+            "visible" => Self::Visible,
+            "hidden" => Self::Hidden,
+            "scroll" => Self::Scroll,
+            "auto" => Self::Auto,
+            #[cfg(feature = "gecko")]
+            "clip" => Self::Clip,
+            #[cfg(feature = "gecko")]
+            "-moz-hidden-unscrollable" if static_prefs::pref!("layout.css.overflow-moz-hidden-unscrollable.enabled") => {
+                Overflow::Clip
+            },
+            "overlay" if static_prefs::pref!("layout.css.overflow-overlay.enabled") => {
+                Overflow::Auto
+            },
+        })
+    }
+}
+
+impl Overflow {
+    /// Return true if the value will create a scrollable box.
+    #[inline]
+    pub fn is_scrollable(&self) -> bool {
+        matches!(*self, Self::Hidden | Self::Scroll | Self::Auto)
+    }
+    /// Convert the value to a scrollable value if it's not already scrollable.
+    /// This maps `visible` to `auto` and `clip` to `hidden`.
+    #[inline]
+    pub fn to_scrollable(&self) -> Self {
+        match *self {
+            Self::Hidden | Self::Scroll | Self::Auto => *self,
+            Self::Visible => Self::Auto,
+            #[cfg(feature = "gecko")]
+            Self::Clip => Self::Hidden,
+        }
+    }
+}
+
+bitflags! {
+    #[derive(MallocSizeOf, SpecifiedValueInfo, ToCss, ToComputedValue, ToResolvedValue, ToShmem, Parse)]
+    #[repr(C)]
+    #[css(bitflags(single = "auto", mixed = "stable,both-edges", validate_mixed="Self::has_stable"))]
+    /// Values for scrollbar-gutter:
+    /// <https://drafts.csswg.org/css-overflow-3/#scrollbar-gutter-property>
+    pub struct ScrollbarGutter: u8 {
+        /// `auto` variant. Just for convenience if there is no flag set.
+        const AUTO = 0;
+        /// `stable` variant.
+        const STABLE = 1 << 0;
+        /// `both-edges` variant.
+        const BOTH_EDGES = 1 << 1;
+    }
+}
+
+impl ScrollbarGutter {
+    #[inline]
+    fn has_stable(&self) -> bool {
+        self.intersects(Self::STABLE)
+    }
+}
diff --git a/servo/components/style/values/specified/calc.rs b/servo/components/style/values/specified/calc.rs
new file mode 100644
index 0000000000..cce7440c97
--- /dev/null
+++ b/servo/components/style/values/specified/calc.rs
@@ -0,0 +1,918 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! [Calc expressions][calc].
+//!
+//! [calc]: https://drafts.csswg.org/css-values/#calc-notation
+
+use crate::parser::ParserContext;
+use crate::values::generics::calc as generic;
+use crate::values::generics::calc::{MinMaxOp, ModRemOp, RoundingStrategy, SortKey};
+use crate::values::specified::length::{AbsoluteLength, FontRelativeLength, NoCalcLength};
+use crate::values::specified::length::{ContainerRelativeLength, ViewportPercentageLength};
+use crate::values::specified::{self, Angle, Time};
+use crate::values::{CSSFloat, CSSInteger};
+use cssparser::{AngleOrNumber, CowRcStr, NumberOrPercentage, Parser, Token};
+use smallvec::SmallVec;
+use std::cmp;
+use std::fmt::{self, Write};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, StyleParseErrorKind, ToCss};
+
+fn trig_enabled() -> bool {
+    static_prefs::pref!("layout.css.trig.enabled")
+}
+
+fn nan_inf_enabled() -> bool {
+    static_prefs::pref!("layout.css.nan-inf.enabled")
+}
+
+/// The name of the mathematical function that we're parsing.
+#[derive(Clone, Copy, Debug, Parse)]
+pub enum MathFunction {
+    /// `calc()`: https://drafts.csswg.org/css-values-4/#funcdef-calc
+    Calc,
+    /// `min()`: https://drafts.csswg.org/css-values-4/#funcdef-min
+    Min,
+    /// `max()`: https://drafts.csswg.org/css-values-4/#funcdef-max
+    Max,
+    /// `clamp()`: https://drafts.csswg.org/css-values-4/#funcdef-clamp
+    Clamp,
+    /// `round()`: https://drafts.csswg.org/css-values-4/#funcdef-round
+    Round,
+    /// `mod()`: https://drafts.csswg.org/css-values-4/#funcdef-mod
+    Mod,
+    /// `rem()`: https://drafts.csswg.org/css-values-4/#funcdef-rem
+    Rem,
+    /// `sin()`: https://drafts.csswg.org/css-values-4/#funcdef-sin
+    Sin,
+    /// `cos()`: https://drafts.csswg.org/css-values-4/#funcdef-cos
+    Cos,
+    /// `tan()`: https://drafts.csswg.org/css-values-4/#funcdef-tan
+    Tan,
+    /// `asin()`: https://drafts.csswg.org/css-values-4/#funcdef-asin
+    Asin,
+    /// `acos()`: https://drafts.csswg.org/css-values-4/#funcdef-acos
+    Acos,
+    /// `atan()`: https://drafts.csswg.org/css-values-4/#funcdef-atan
+    Atan,
+    /// `atan2()`: https://drafts.csswg.org/css-values-4/#funcdef-atan2
+    Atan2,
+}
+
+/// A leaf node inside a `Calc` expression's AST.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
+pub enum Leaf {
+    /// `<length>`
+    Length(NoCalcLength),
+    /// `<angle>`
+    Angle(Angle),
+    /// `<time>`
+    Time(Time),
+    /// `<percentage>`
+    Percentage(CSSFloat),
+    /// `<number>`
+    Number(CSSFloat),
+}
+
+impl Leaf {
+    fn as_length(&self) -> Option<&NoCalcLength> {
+        match *self {
+            Self::Length(ref l) => Some(l),
+            _ => None,
+        }
+    }
+}
+
+impl ToCss for Leaf {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            Self::Length(ref l) => l.to_css(dest),
+            Self::Number(ref n) => n.to_css(dest),
+            Self::Percentage(p) => crate::values::serialize_percentage(p, dest),
+            Self::Angle(ref a) => a.to_css(dest),
+            Self::Time(ref t) => t.to_css(dest),
+        }
+    }
+}
+
+bitflags! {
+    /// Expected units we allow parsing within a `calc()` expression.
+    ///
+    /// This is used as a hint for the parser to fast-reject invalid
+    /// expressions. Numbers are always allowed because they multiply other
+    /// units.
+    struct CalcUnits: u8 {
+        const LENGTH = 1 << 0;
+        const PERCENTAGE = 1 << 1;
+        const ANGLE = 1 << 2;
+        const TIME = 1 << 3;
+
+        const LENGTH_PERCENTAGE = Self::LENGTH.bits | Self::PERCENTAGE.bits;
+        // NOTE: When you add to this, make sure to make Atan2 deal with these.
+        const ALL = Self::LENGTH.bits | Self::PERCENTAGE.bits | Self::ANGLE.bits | Self::TIME.bits;
+    }
+}
+
+/// A struct to hold a simplified `<length>` or `<percentage>` expression.
+///
+/// In some cases, e.g. DOMMatrix, we support calc(), but reject all the
+/// relative lengths, and to_computed_pixel_length_without_context() handles
+/// this case. Therefore, if you want to add a new field, please make sure this
+/// function work properly.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+#[allow(missing_docs)]
+pub struct CalcLengthPercentage {
+    #[css(skip)]
+    pub clamping_mode: AllowedNumericType,
+    pub node: CalcNode,
+}
+
+impl CalcLengthPercentage {
+    fn same_unit_length_as(a: &Self, b: &Self) -> Option<(CSSFloat, CSSFloat)> {
+        use generic::CalcNodeLeaf;
+
+        debug_assert_eq!(a.clamping_mode, b.clamping_mode);
+        debug_assert_eq!(a.clamping_mode, AllowedNumericType::All);
+
+        let a = a.node.as_leaf()?;
+        let b = b.node.as_leaf()?;
+
+        if a.sort_key() != b.sort_key() {
+            return None;
+        }
+
+        let a = a.as_length()?.unitless_value();
+        let b = b.as_length()?.unitless_value();
+        return Some((a, b));
+    }
+}
+
+impl SpecifiedValueInfo for CalcLengthPercentage {}
+
+impl PartialOrd for Leaf {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        use self::Leaf::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return None;
+        }
+
+        match (self, other) {
+            // NOTE: Percentages can't be compared reasonably here because the
+            // percentage basis might be negative, see bug 1709018.
+            // Conveniently, we only use this for <length-percentage> (for raw
+            // percentages, we go through resolve()).
+            (&Percentage(..), &Percentage(..)) => None,
+            (&Length(ref one), &Length(ref other)) => one.partial_cmp(other),
+            (&Angle(ref one), &Angle(ref other)) => one.degrees().partial_cmp(&other.degrees()),
+            (&Time(ref one), &Time(ref other)) => one.seconds().partial_cmp(&other.seconds()),
+            (&Number(ref one), &Number(ref other)) => one.partial_cmp(other),
+            _ => {
+                match *self {
+                    Length(..) | Percentage(..) | Angle(..) | Time(..) | Number(..) => {},
+                }
+                unsafe {
+                    debug_unreachable!("Forgot a branch?");
+                }
+            },
+        }
+    }
+}
+
+impl generic::CalcNodeLeaf for Leaf {
+    fn unitless_value(&self) -> f32 {
+        match *self {
+            Self::Length(ref l) => l.unitless_value(),
+            Self::Percentage(n) | Self::Number(n) => n,
+            Self::Angle(ref a) => a.degrees(),
+            Self::Time(ref t) => t.seconds(),
+        }
+    }
+
+    fn mul_by(&mut self, scalar: f32) {
+        match *self {
+            Self::Length(ref mut l) => {
+                // FIXME: For consistency this should probably convert absolute
+                // lengths into pixels.
+                *l = *l * scalar;
+            },
+            Self::Number(ref mut n) => {
+                *n *= scalar;
+            },
+            Self::Angle(ref mut a) => {
+                *a = Angle::from_calc(a.degrees() * scalar);
+            },
+            Self::Time(ref mut t) => {
+                *t = Time::from_calc(t.seconds() * scalar);
+            },
+            Self::Percentage(ref mut p) => {
+                *p *= scalar;
+            },
+        }
+    }
+
+    fn sort_key(&self) -> SortKey {
+        match *self {
+            Self::Number(..) => SortKey::Number,
+            Self::Percentage(..) => SortKey::Percentage,
+            Self::Time(..) => SortKey::Sec,
+            Self::Angle(..) => SortKey::Deg,
+            Self::Length(ref l) => match *l {
+                NoCalcLength::Absolute(..) => SortKey::Px,
+                NoCalcLength::FontRelative(ref relative) => match *relative {
+                    FontRelativeLength::Ch(..) => SortKey::Ch,
+                    FontRelativeLength::Em(..) => SortKey::Em,
+                    FontRelativeLength::Ex(..) => SortKey::Ex,
+                    FontRelativeLength::Cap(..) => SortKey::Cap,
+                    FontRelativeLength::Ic(..) => SortKey::Ic,
+                    FontRelativeLength::Rem(..) => SortKey::Rem,
+                },
+                NoCalcLength::ViewportPercentage(ref vp) => match *vp {
+                    ViewportPercentageLength::Vh(..) => SortKey::Vh,
+                    ViewportPercentageLength::Svh(..) => SortKey::Svh,
+                    ViewportPercentageLength::Lvh(..) => SortKey::Lvh,
+                    ViewportPercentageLength::Dvh(..) => SortKey::Dvh,
+                    ViewportPercentageLength::Vw(..) => SortKey::Vw,
+                    ViewportPercentageLength::Svw(..) => SortKey::Svw,
+                    ViewportPercentageLength::Lvw(..) => SortKey::Lvw,
+                    ViewportPercentageLength::Dvw(..) => SortKey::Dvw,
+                    ViewportPercentageLength::Vmax(..) => SortKey::Vmax,
+                    ViewportPercentageLength::Svmax(..) => SortKey::Svmax,
+                    ViewportPercentageLength::Lvmax(..) => SortKey::Lvmax,
+                    ViewportPercentageLength::Dvmax(..) => SortKey::Dvmax,
+                    ViewportPercentageLength::Vmin(..) => SortKey::Vmin,
+                    ViewportPercentageLength::Svmin(..) => SortKey::Svmin,
+                    ViewportPercentageLength::Lvmin(..) => SortKey::Lvmin,
+                    ViewportPercentageLength::Dvmin(..) => SortKey::Dvmin,
+                    ViewportPercentageLength::Vb(..) => SortKey::Vb,
+                    ViewportPercentageLength::Svb(..) => SortKey::Svb,
+                    ViewportPercentageLength::Lvb(..) => SortKey::Lvb,
+                    ViewportPercentageLength::Dvb(..) => SortKey::Dvb,
+                    ViewportPercentageLength::Vi(..) => SortKey::Vi,
+                    ViewportPercentageLength::Svi(..) => SortKey::Svi,
+                    ViewportPercentageLength::Lvi(..) => SortKey::Lvi,
+                    ViewportPercentageLength::Dvi(..) => SortKey::Dvi,
+                },
+                NoCalcLength::ContainerRelative(ref cq) => match *cq {
+                    ContainerRelativeLength::Cqw(..) => SortKey::Cqw,
+                    ContainerRelativeLength::Cqh(..) => SortKey::Cqh,
+                    ContainerRelativeLength::Cqi(..) => SortKey::Cqi,
+                    ContainerRelativeLength::Cqb(..) => SortKey::Cqb,
+                    ContainerRelativeLength::Cqmin(..) => SortKey::Cqmin,
+                    ContainerRelativeLength::Cqmax(..) => SortKey::Cqmax,
+                },
+                NoCalcLength::ServoCharacterWidth(..) => unreachable!(),
+            },
+        }
+    }
+
+    fn simplify(&mut self) {
+        if let Self::Length(NoCalcLength::Absolute(ref mut abs)) = *self {
+            *abs = AbsoluteLength::Px(abs.to_px());
+        }
+    }
+
+    /// Tries to merge one sum to another, that is, perform `x` + `y`.
+    ///
+    /// Only handles leaf nodes, it's the caller's responsibility to simplify
+    /// them before calling this if needed.
+    fn try_sum_in_place(&mut self, other: &Self) -> Result<(), ()> {
+        use self::Leaf::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        match (self, other) {
+            (&mut Number(ref mut one), &Number(ref other)) |
+            (&mut Percentage(ref mut one), &Percentage(ref other)) => {
+                *one += *other;
+            },
+            (&mut Angle(ref mut one), &Angle(ref other)) => {
+                *one = specified::Angle::from_calc(one.degrees() + other.degrees());
+            },
+            (&mut Time(ref mut one), &Time(ref other)) => {
+                *one = specified::Time::from_calc(one.seconds() + other.seconds());
+            },
+            (&mut Length(ref mut one), &Length(ref other)) => {
+                *one = one.try_op(other, std::ops::Add::add)?;
+            },
+            _ => {
+                match *other {
+                    Number(..) | Percentage(..) | Angle(..) | Time(..) | Length(..) => {},
+                }
+                unsafe {
+                    debug_unreachable!();
+                }
+            },
+        }
+
+        Ok(())
+    }
+
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        use self::Leaf::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        match (self, other) {
+            (&Number(one), &Number(other)) => {
+                return Ok(Leaf::Number(op(one, other)));
+            },
+            (&Percentage(one), &Percentage(other)) => {
+                return Ok(Leaf::Percentage(op(one, other)));
+            },
+            (&Angle(ref one), &Angle(ref other)) => {
+                return Ok(Leaf::Angle(specified::Angle::from_calc(op(
+                    one.degrees(),
+                    other.degrees(),
+                ))));
+            },
+            (&Time(ref one), &Time(ref other)) => {
+                return Ok(Leaf::Time(specified::Time::from_calc(op(
+                    one.seconds(),
+                    other.seconds(),
+                ))));
+            },
+            (&Length(ref one), &Length(ref other)) => {
+                return Ok(Leaf::Length(one.try_op(other, op)?));
+            },
+            _ => {
+                match *other {
+                    Number(..) | Percentage(..) | Angle(..) | Time(..) | Length(..) => {},
+                }
+                unsafe {
+                    debug_unreachable!();
+                }
+            },
+        }
+    }
+}
+
+/// A calc node representation for specified values.
+pub type CalcNode = generic::GenericCalcNode<Leaf>;
+
+impl CalcNode {
+    /// Tries to parse a single element in the expression, that is, a
+    /// `<length>`, `<angle>`, `<time>`, `<percentage>`, according to
+    /// `allowed_units`.
+    ///
+    /// May return a "complex" `CalcNode`, in the presence of a parenthesized
+    /// expression, for example.
+    fn parse_one<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        match input.next()? {
+            &Token::Number { value, .. } => Ok(CalcNode::Leaf(Leaf::Number(value))),
+            &Token::Dimension {
+                value, ref unit, ..
+            } => {
+                if allowed_units.intersects(CalcUnits::LENGTH) {
+                    if let Ok(l) = NoCalcLength::parse_dimension(context, value, unit) {
+                        return Ok(CalcNode::Leaf(Leaf::Length(l)));
+                    }
+                }
+                if allowed_units.intersects(CalcUnits::ANGLE) {
+                    if let Ok(a) = Angle::parse_dimension(value, unit, /* from_calc = */ true) {
+                        return Ok(CalcNode::Leaf(Leaf::Angle(a)));
+                    }
+                }
+                if allowed_units.intersects(CalcUnits::TIME) {
+                    if let Ok(t) = Time::parse_dimension(value, unit, /* from_calc = */ true) {
+                        return Ok(CalcNode::Leaf(Leaf::Time(t)));
+                    }
+                }
+                return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            },
+            &Token::Percentage { unit_value, .. }
+                if allowed_units.intersects(CalcUnits::PERCENTAGE) =>
+            {
+                Ok(CalcNode::Leaf(Leaf::Percentage(unit_value)))
+            },
+            &Token::ParenthesisBlock => input.parse_nested_block(|input| {
+                CalcNode::parse_argument(context, input, allowed_units)
+            }),
+            &Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                CalcNode::parse(context, input, function, allowed_units)
+            },
+            &Token::Ident(ref ident) => {
+                let number = match_ignore_ascii_case! { &**ident,
+                    "e" if trig_enabled() => std::f32::consts::E,
+                    "pi" if trig_enabled() => std::f32::consts::PI,
+                    "infinity" if nan_inf_enabled() => f32::INFINITY,
+                    "-infinity" if nan_inf_enabled() => f32::NEG_INFINITY,
+                    "nan" if nan_inf_enabled() => f32::NAN,
+                    _ => return Err(location.new_unexpected_token_error(Token::Ident(ident.clone()))),
+                };
+                Ok(CalcNode::Leaf(Leaf::Number(number)))
+            },
+            t => Err(location.new_unexpected_token_error(t.clone())),
+        }
+    }
+
+    /// Parse a top-level `calc` expression, with all nested sub-expressions.
+    ///
+    /// This is in charge of parsing, for example, `2 + 3 * 100%`.
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        // TODO: Do something different based on the function name. In
+        // particular, for non-calc function we need to take a list of
+        // comma-separated arguments and such.
+        input.parse_nested_block(|input| {
+            match function {
+                MathFunction::Calc => Self::parse_argument(context, input, allowed_units),
+                MathFunction::Clamp => {
+                    let min = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let center = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let max = Self::parse_argument(context, input, allowed_units)?;
+                    Ok(Self::Clamp {
+                        min: Box::new(min),
+                        center: Box::new(center),
+                        max: Box::new(max),
+                    })
+                },
+                MathFunction::Round => {
+                    let strategy = input.try_parse(parse_rounding_strategy);
+
+                    // <rounding-strategy> = nearest | up | down | to-zero
+                    // https://drafts.csswg.org/css-values-4/#calc-syntax
+                    fn parse_rounding_strategy<'i, 't>(
+                        input: &mut Parser<'i, 't>,
+                    ) -> Result<RoundingStrategy, ParseError<'i>> {
+                        Ok(try_match_ident_ignore_ascii_case! { input,
+                            "nearest" => RoundingStrategy::Nearest,
+                            "up" => RoundingStrategy::Up,
+                            "down" => RoundingStrategy::Down,
+                            "to-zero" => RoundingStrategy::ToZero,
+                        })
+                    }
+
+                    if strategy.is_ok() {
+                        input.expect_comma()?;
+                    }
+
+                    let value = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let step = Self::parse_argument(context, input, allowed_units)?;
+
+                    Ok(Self::Round {
+                        strategy: strategy.unwrap_or(RoundingStrategy::Nearest),
+                        value: Box::new(value),
+                        step: Box::new(step),
+                    })
+                },
+                MathFunction::Mod | MathFunction::Rem => {
+                    let dividend = Self::parse_argument(context, input, allowed_units)?;
+                    input.expect_comma()?;
+                    let divisor = Self::parse_argument(context, input, allowed_units)?;
+
+                    let op = match function {
+                        MathFunction::Mod => ModRemOp::Mod,
+                        MathFunction::Rem => ModRemOp::Rem,
+                        _ => unreachable!(),
+                    };
+                    Ok(Self::ModRem {
+                        dividend: Box::new(dividend),
+                        divisor: Box::new(divisor),
+                        op,
+                    })
+                },
+                MathFunction::Min | MathFunction::Max => {
+                    // TODO(emilio): The common case for parse_comma_separated
+                    // is just one element, but for min / max is two, really...
+                    //
+                    // Consider adding an API to cssparser to specify the
+                    // initial vector capacity?
+                    let arguments = input.parse_comma_separated(|input| {
+                        Self::parse_argument(context, input, allowed_units)
+                    })?;
+
+                    let op = match function {
+                        MathFunction::Min => MinMaxOp::Min,
+                        MathFunction::Max => MinMaxOp::Max,
+                        _ => unreachable!(),
+                    };
+
+                    Ok(Self::MinMax(arguments.into(), op))
+                },
+                MathFunction::Sin | MathFunction::Cos | MathFunction::Tan => {
+                    let argument = Self::parse_argument(context, input, CalcUnits::ANGLE)?;
+                    let radians = match argument.to_number() {
+                        Ok(v) => v,
+                        Err(()) => match argument.to_angle() {
+                            Ok(angle) => angle.radians(),
+                            Err(()) => {
+                                return Err(
+                                    input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                                )
+                            },
+                        },
+                    };
+                    let number = match function {
+                        MathFunction::Sin => radians.sin(),
+                        MathFunction::Cos => radians.cos(),
+                        MathFunction::Tan => radians.tan(),
+                        _ => unsafe {
+                            debug_unreachable!("We just checked!");
+                        },
+                    };
+                    Ok(Self::Leaf(Leaf::Number(number)))
+                },
+                MathFunction::Asin | MathFunction::Acos | MathFunction::Atan => {
+                    let argument = Self::parse_argument(context, input, CalcUnits::empty())?;
+                    let number = match argument.to_number() {
+                        Ok(v) => v,
+                        Err(()) => {
+                            return Err(
+                                input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                            )
+                        },
+                    };
+
+                    let radians = match function {
+                        MathFunction::Asin => number.asin(),
+                        MathFunction::Acos => number.acos(),
+                        MathFunction::Atan => number.atan(),
+                        _ => unsafe {
+                            debug_unreachable!("We just checked!");
+                        },
+                    };
+
+                    Ok(Self::Leaf(Leaf::Angle(Angle::from_radians(radians))))
+                },
+                MathFunction::Atan2 => {
+                    let a = Self::parse_argument(context, input, CalcUnits::ALL)?;
+                    input.expect_comma()?;
+                    let b = Self::parse_argument(context, input, CalcUnits::ALL)?;
+                    fn resolve_atan2(a: CalcNode, b: CalcNode) -> Result<CSSFloat, ()> {
+                        if let Ok(a) = a.to_number() {
+                            let b = b.to_number()?;
+                            return Ok(a.atan2(b));
+                        }
+
+                        if let Ok(a) = a.to_percentage() {
+                            let b = b.to_percentage()?;
+                            return Ok(a.atan2(b));
+                        }
+
+                        if let Ok(a) = a.to_time() {
+                            let b = b.to_time()?;
+                            return Ok(a.seconds().atan2(b.seconds()));
+                        }
+
+                        if let Ok(a) = a.to_angle() {
+                            let b = b.to_angle()?;
+                            return Ok(a.radians().atan2(b.radians()));
+                        }
+
+                        let a = a.into_length_or_percentage(AllowedNumericType::All)?;
+                        let b = b.into_length_or_percentage(AllowedNumericType::All)?;
+                        let (a, b) = CalcLengthPercentage::same_unit_length_as(&a, &b).ok_or(())?;
+                        return Ok(a.atan2(b));
+                    }
+
+                    let radians = match resolve_atan2(a, b) {
+                        Ok(v) => v,
+                        Err(()) => {
+                            return Err(
+                                input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                            )
+                        },
+                    };
+
+                    Ok(Self::Leaf(Leaf::Angle(Angle::from_radians(radians))))
+                },
+            }
+        })
+    }
+
+    fn parse_argument<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut sum = SmallVec::<[CalcNode; 1]>::new();
+        sum.push(Self::parse_product(context, input, allowed_units)?);
+
+        loop {
+            let start = input.state();
+            match input.next_including_whitespace() {
+                Ok(&Token::WhiteSpace(_)) => {
+                    if input.is_exhausted() {
+                        break; // allow trailing whitespace
+                    }
+                    match *input.next()? {
+                        Token::Delim('+') => {
+                            sum.push(Self::parse_product(context, input, allowed_units)?);
+                        },
+                        Token::Delim('-') => {
+                            let mut rhs = Self::parse_product(context, input, allowed_units)?;
+                            rhs.negate();
+                            sum.push(rhs);
+                        },
+                        _ => {
+                            input.reset(&start);
+                            break;
+                        },
+                    }
+                },
+                _ => {
+                    input.reset(&start);
+                    break;
+                },
+            }
+        }
+
+        Ok(if sum.len() == 1 {
+            sum.drain(..).next().unwrap()
+        } else {
+            Self::Sum(sum.into_boxed_slice().into())
+        })
+    }
+
+    /// Parse a top-level `calc` expression, and all the products that may
+    /// follow, and stop as soon as a non-product expression is found.
+    ///
+    /// This should parse correctly:
+    ///
+    /// * `2`
+    /// * `2 * 2`
+    /// * `2 * 2 + 2` (but will leave the `+ 2` unparsed).
+    ///
+    fn parse_product<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allowed_units: CalcUnits,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut node = Self::parse_one(context, input, allowed_units)?;
+
+        loop {
+            let start = input.state();
+            match input.next() {
+                Ok(&Token::Delim('*')) => {
+                    let rhs = Self::parse_one(context, input, allowed_units)?;
+                    if let Ok(rhs) = rhs.to_number() {
+                        node.mul_by(rhs);
+                    } else if let Ok(number) = node.to_number() {
+                        node = rhs;
+                        node.mul_by(number);
+                    } else {
+                        // One of the two parts of the multiplication has to be
+                        // a number, at least until we implement unit math.
+                        return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                    }
+                },
+                Ok(&Token::Delim('/')) => {
+                    let rhs = Self::parse_one(context, input, allowed_units)?;
+                    // Dividing by units is not ok.
+                    //
+                    // TODO(emilio): Eventually it should be.
+                    let number = match rhs.to_number() {
+                        Ok(n) if n != 0. || nan_inf_enabled() => n,
+                        _ => {
+                            return Err(
+                                input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                            )
+                        },
+                    };
+                    node.mul_by(1. / number);
+                },
+                _ => {
+                    input.reset(&start);
+                    break;
+                },
+            }
+        }
+
+        Ok(node)
+    }
+
+    /// Tries to simplify this expression into a `<length>` or `<percentage>`
+    /// value.
+    fn into_length_or_percentage(
+        mut self,
+        clamping_mode: AllowedNumericType,
+    ) -> Result<CalcLengthPercentage, ()> {
+        // Keep track of whether there's any invalid member of the calculation,
+        // so as to reject the calculation properly at parse-time.
+        let mut any_invalid = false;
+        self.visit_depth_first(|node| {
+            if let CalcNode::Leaf(ref l) = *node {
+                any_invalid |= !matches!(*l, Leaf::Percentage(..) | Leaf::Length(..));
+            }
+            node.simplify_and_sort_direct_children();
+        });
+
+        if any_invalid {
+            return Err(());
+        }
+
+        Ok(CalcLengthPercentage {
+            clamping_mode,
+            node: self,
+        })
+    }
+
+    /// Tries to simplify this expression into a `<time>` value.
+    fn to_time(&self) -> Result<Time, ()> {
+        let seconds = self.resolve(|leaf| match *leaf {
+            Leaf::Time(ref t) => Ok(t.seconds()),
+            _ => Err(()),
+        })?;
+        Ok(Time::from_calc(crate::values::normalize(seconds)))
+    }
+
+    /// Tries to simplify this expression into an `Angle` value.
+    fn to_angle(&self) -> Result<Angle, ()> {
+        let degrees = self.resolve(|leaf| match *leaf {
+            Leaf::Angle(ref angle) => Ok(angle.degrees()),
+            _ => Err(()),
+        })?;
+        Ok(Angle::from_calc(crate::values::normalize(degrees)))
+    }
+
+    /// Tries to simplify this expression into a `<number>` value.
+    fn to_number(&self) -> Result<CSSFloat, ()> {
+        self.resolve(|leaf| match *leaf {
+            Leaf::Number(n) => Ok(n),
+            _ => Err(()),
+        })
+    }
+
+    /// Tries to simplify this expression into a `<percentage>` value.
+    fn to_percentage(&self) -> Result<CSSFloat, ()> {
+        self.resolve(|leaf| match *leaf {
+            Leaf::Percentage(p) => Ok(p),
+            _ => Err(()),
+        })
+    }
+
+    /// Given a function name, and the location from where the token came from,
+    /// return a mathematical function corresponding to that name or an error.
+    #[inline]
+    pub fn math_function<'i>(
+        name: &CowRcStr<'i>,
+        location: cssparser::SourceLocation,
+    ) -> Result<MathFunction, ParseError<'i>> {
+        use self::MathFunction::*;
+
+        let function = match MathFunction::from_ident(&*name) {
+            Ok(f) => f,
+            Err(()) => {
+                return Err(location.new_unexpected_token_error(Token::Function(name.clone())))
+            },
+        };
+
+        let enabled = if matches!(function, Sin | Cos | Tan | Asin | Acos | Atan | Atan2) {
+            trig_enabled()
+        } else if matches!(function, Round) {
+            static_prefs::pref!("layout.css.round.enabled")
+        } else if matches!(function, Mod | Rem) {
+            static_prefs::pref!("layout.css.mod-rem.enabled")
+        } else {
+            true
+        };
+
+        if !enabled {
+            return Err(location.new_unexpected_token_error(Token::Function(name.clone())));
+        }
+
+        Ok(function)
+    }
+
+    /// Convenience parsing function for integers.
+    pub fn parse_integer<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<CSSInteger, ParseError<'i>> {
+        Self::parse_number(context, input, function).map(|n| n.round() as CSSInteger)
+    }
+
+    /// Convenience parsing function for `<length> | <percentage>`.
+    pub fn parse_length_or_percentage<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        clamping_mode: AllowedNumericType,
+        function: MathFunction,
+    ) -> Result<CalcLengthPercentage, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::LENGTH_PERCENTAGE)?
+            .into_length_or_percentage(clamping_mode)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for percentages.
+    pub fn parse_percentage<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<CSSFloat, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::PERCENTAGE)?
+            .to_percentage()
+            .map(crate::values::normalize)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<length>`.
+    pub fn parse_length<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        clamping_mode: AllowedNumericType,
+        function: MathFunction,
+    ) -> Result<CalcLengthPercentage, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::LENGTH)?
+            .into_length_or_percentage(clamping_mode)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<number>`.
+    pub fn parse_number<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<CSSFloat, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::empty())?
+            .to_number()
+            .map(crate::values::normalize)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<angle>`.
+    pub fn parse_angle<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<Angle, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::ANGLE)?
+            .to_angle()
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<time>`.
+    pub fn parse_time<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<Time, ParseError<'i>> {
+        Self::parse(context, input, function, CalcUnits::TIME)?
+            .to_time()
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+
+    /// Convenience parsing function for `<number>` or `<percentage>`.
+    pub fn parse_number_or_percentage<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<NumberOrPercentage, ParseError<'i>> {
+        let node = Self::parse(context, input, function, CalcUnits::PERCENTAGE)?;
+
+        if let Ok(value) = node.to_number() {
+            return Ok(NumberOrPercentage::Number { value });
+        }
+
+        match node.to_percentage() {
+            Ok(unit_value) => Ok(NumberOrPercentage::Percentage { unit_value }),
+            Err(()) => Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+        }
+    }
+
+    /// Convenience parsing function for `<number>` or `<angle>`.
+    pub fn parse_angle_or_number<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        function: MathFunction,
+    ) -> Result<AngleOrNumber, ParseError<'i>> {
+        let node = Self::parse(context, input, function, CalcUnits::ANGLE)?;
+
+        if let Ok(angle) = node.to_angle() {
+            let degrees = angle.degrees();
+            return Ok(AngleOrNumber::Angle { degrees });
+        }
+
+        match node.to_number() {
+            Ok(value) => Ok(AngleOrNumber::Number { value }),
+            Err(()) => Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+        }
+    }
+}
diff --git a/servo/components/style/values/specified/color.rs b/servo/components/style/values/specified/color.rs
new file mode 100644
index 0000000000..b27a798bce
--- /dev/null
+++ b/servo/components/style/values/specified/color.rs
@@ -0,0 +1,1020 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified color values.
+
+use super::AllowQuirks;
+use crate::media_queries::Device;
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::{Color as ComputedColor, Context, ToComputedValue};
+use crate::values::generics::color::{
+    ColorInterpolationMethod, GenericCaretColor, GenericColorMix, GenericColorOrAuto,
+};
+use crate::values::specified::calc::CalcNode;
+use crate::values::specified::Percentage;
+use crate::values::CustomIdent;
+use cssparser::{AngleOrNumber, Color as CSSParserColor, Parser, Token, RGBA};
+use cssparser::{BasicParseErrorKind, NumberOrPercentage, ParseErrorKind};
+use itoa;
+use std::fmt::{self, Write};
+use std::io::Write as IoWrite;
+use style_traits::{CssType, CssWriter, KeywordsCollectFn, ParseError, StyleParseErrorKind};
+use style_traits::{SpecifiedValueInfo, ToCss, ValueParseErrorKind};
+
+/// A specified color-mix().
+pub type ColorMix = GenericColorMix<Color, Percentage>;
+
+impl ColorMix {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        preserve_authored: PreserveAuthored,
+    ) -> Result<Self, ParseError<'i>> {
+        let enabled =
+            context.chrome_rules_enabled() || static_prefs::pref!("layout.css.color-mix.enabled");
+
+        if !enabled {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        input.expect_function_matching("color-mix")?;
+
+        input.parse_nested_block(|input| {
+            let interpolation = ColorInterpolationMethod::parse(context, input)?;
+            input.expect_comma()?;
+
+            let try_parse_percentage = |input: &mut Parser| -> Option<Percentage> {
+                input
+                    .try_parse(|input| Percentage::parse_zero_to_a_hundred(context, input))
+                    .ok()
+            };
+
+            let mut left_percentage = try_parse_percentage(input);
+
+            let left = Color::parse_internal(context, input, preserve_authored)?;
+            if left_percentage.is_none() {
+                left_percentage = try_parse_percentage(input);
+            }
+
+            input.expect_comma()?;
+
+            let mut right_percentage = try_parse_percentage(input);
+
+            let right = Color::parse(context, input)?;
+
+            if right_percentage.is_none() {
+                right_percentage = try_parse_percentage(input);
+            }
+
+            let right_percentage = right_percentage
+                .unwrap_or_else(|| Percentage::new(1.0 - left_percentage.map_or(0.5, |p| p.get())));
+
+            let left_percentage =
+                left_percentage.unwrap_or_else(|| Percentage::new(1.0 - right_percentage.get()));
+
+            if left_percentage.get() + right_percentage.get() <= 0.0 {
+                // If the percentages sum to zero, the function is invalid.
+                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+
+            Ok(ColorMix {
+                interpolation,
+                left,
+                left_percentage,
+                right,
+                right_percentage,
+                normalize_weights: true,
+            })
+        })
+    }
+}
+
+/// Specified color value
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
+pub enum Color {
+    /// The 'currentColor' keyword
+    CurrentColor,
+    /// A specific RGBA color
+    Numeric {
+        /// Parsed RGBA color
+        parsed: RGBA,
+        /// Authored representation
+        authored: Option<Box<str>>,
+    },
+    /// A system color.
+    #[cfg(feature = "gecko")]
+    System(SystemColor),
+    /// A color mix.
+    ColorMix(Box<ColorMix>),
+    /// Quirksmode-only rule for inheriting color from the body
+    #[cfg(feature = "gecko")]
+    InheritFromBodyQuirk,
+}
+
+/// System colors. A bunch of these are ad-hoc, others come from Windows:
+///
+///   https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getsyscolor
+///
+/// Others are HTML/CSS specific. Spec is:
+///
+///   https://drafts.csswg.org/css-color/#css-system-colors
+///   https://drafts.csswg.org/css-color/#deprecated-system-colors
+#[allow(missing_docs)]
+#[cfg(feature = "gecko")]
+#[derive(Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, ToCss, ToShmem)]
+#[repr(u8)]
+pub enum SystemColor {
+    Activeborder,
+    /// Background in the (active) titlebar.
+    Activecaption,
+    Appworkspace,
+    Background,
+    Buttonface,
+    Buttonhighlight,
+    Buttonshadow,
+    Buttontext,
+    Buttonborder,
+    /// Text color in the (active) titlebar.
+    Captiontext,
+    #[parse(aliases = "-moz-field")]
+    Field,
+    /// Used for disabled field backgrounds.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozDisabledfield,
+    #[parse(aliases = "-moz-fieldtext")]
+    Fieldtext,
+
+    Mark,
+    Marktext,
+
+    /// Combobox widgets
+    MozComboboxtext,
+    MozCombobox,
+
+    Graytext,
+    Highlight,
+    Highlighttext,
+    Inactiveborder,
+    /// Background in the (inactive) titlebar.
+    Inactivecaption,
+    /// Text color in the (inactive) titlebar.
+    Inactivecaptiontext,
+    Infobackground,
+    Infotext,
+    Menu,
+    Menutext,
+    Scrollbar,
+    Threeddarkshadow,
+    Threedface,
+    Threedhighlight,
+    Threedlightshadow,
+    Threedshadow,
+    Window,
+    Windowframe,
+    Windowtext,
+    MozButtondefault,
+    #[parse(aliases = "-moz-default-color")]
+    Canvastext,
+    #[parse(aliases = "-moz-default-background-color")]
+    Canvas,
+    MozDialog,
+    MozDialogtext,
+    /// Used to highlight valid regions to drop something onto.
+    MozDragtargetzone,
+    /// Used for selected but not focused cell backgrounds.
+    #[parse(aliases = "-moz-html-cellhighlight")]
+    MozCellhighlight,
+    /// Used for selected but not focused cell text.
+    #[parse(aliases = "-moz-html-cellhighlighttext")]
+    MozCellhighlighttext,
+    /// Used for selected and focused html cell backgrounds.
+    Selecteditem,
+    /// Used for selected and focused html cell text.
+    Selecteditemtext,
+    /// Used to button text background when hovered.
+    MozButtonhoverface,
+    /// Used to button text color when hovered.
+    MozButtonhovertext,
+    /// Used for menu item backgrounds when hovered.
+    MozMenuhover,
+    /// Used for menu item backgrounds when hovered and disabled.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozMenuhoverdisabled,
+    /// Used for menu item text when hovered.
+    MozMenuhovertext,
+    /// Used for menubar item text.
+    MozMenubartext,
+    /// Used for menubar item text when hovered.
+    MozMenubarhovertext,
+
+    /// On platforms where these colors are the same as -moz-field, use
+    /// -moz-fieldtext as foreground color
+    MozEventreerow,
+    MozOddtreerow,
+
+    /// Used for button text when pressed.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozButtonactivetext,
+
+    /// Used for button background when pressed.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozButtonactiveface,
+
+    /// Used for button background when disabled.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozButtondisabledface,
+
+    /// Background color of chrome toolbars in active windows.
+    MozMacChromeActive,
+    /// Background color of chrome toolbars in inactive windows.
+    MozMacChromeInactive,
+    /// Foreground color of default buttons.
+    MozMacDefaultbuttontext,
+    /// Ring color around text fields and lists.
+    MozMacFocusring,
+    /// Color used when mouse is over a menu item.
+    MozMacMenuselect,
+    /// Color used to do shadows on menu items.
+    MozMacMenushadow,
+    /// Color used to display text for disabled menu items.
+    MozMacMenutextdisable,
+    /// Color used to display text while mouse is over a menu item.
+    MozMacMenutextselect,
+    /// Text color of disabled text on toolbars.
+    MozMacDisabledtoolbartext,
+    /// Inactive light hightlight
+    MozMacSecondaryhighlight,
+
+    MozMacMenupopup,
+    MozMacMenuitem,
+    MozMacActiveMenuitem,
+    MozMacSourceList,
+    MozMacSourceListSelection,
+    MozMacActiveSourceListSelection,
+    MozMacTooltip,
+
+    /// Theme accent color.
+    /// https://drafts.csswg.org/css-color-4/#valdef-system-color-accentcolor
+    Accentcolor,
+
+    /// Foreground for the accent color.
+    /// https://drafts.csswg.org/css-color-4/#valdef-system-color-accentcolortext
+    Accentcolortext,
+
+    /// The background-color for :autofill-ed inputs.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozAutofillBackground,
+
+    /// Media rebar text.
+    MozWinMediatext,
+    /// Communications rebar text.
+    MozWinCommunicationstext,
+
+    /// Hyperlink color extracted from the system, not affected by the
+    /// browser.anchor_color user pref.
+    ///
+    /// There is no OS-specified safe background color for this text, but it is
+    /// used regularly within Windows and the Gnome DE on Dialog and Window
+    /// colors.
+    MozNativehyperlinktext,
+
+    /// As above, but visited link color.
+    #[css(skip)]
+    MozNativevisitedhyperlinktext,
+
+    #[parse(aliases = "-moz-hyperlinktext")]
+    Linktext,
+    #[parse(aliases = "-moz-activehyperlinktext")]
+    Activetext,
+    #[parse(aliases = "-moz-visitedhyperlinktext")]
+    Visitedtext,
+
+    /// Color of tree column headers
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozColheadertext,
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozColheaderhovertext,
+
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    TextSelectDisabledBackground,
+    #[css(skip)]
+    TextSelectAttentionBackground,
+    #[css(skip)]
+    TextSelectAttentionForeground,
+    #[css(skip)]
+    TextHighlightBackground,
+    #[css(skip)]
+    TextHighlightForeground,
+    #[css(skip)]
+    IMERawInputBackground,
+    #[css(skip)]
+    IMERawInputForeground,
+    #[css(skip)]
+    IMERawInputUnderline,
+    #[css(skip)]
+    IMESelectedRawTextBackground,
+    #[css(skip)]
+    IMESelectedRawTextForeground,
+    #[css(skip)]
+    IMESelectedRawTextUnderline,
+    #[css(skip)]
+    IMEConvertedTextBackground,
+    #[css(skip)]
+    IMEConvertedTextForeground,
+    #[css(skip)]
+    IMEConvertedTextUnderline,
+    #[css(skip)]
+    IMESelectedConvertedTextBackground,
+    #[css(skip)]
+    IMESelectedConvertedTextForeground,
+    #[css(skip)]
+    IMESelectedConvertedTextUnderline,
+    #[css(skip)]
+    SpellCheckerUnderline,
+    #[css(skip)]
+    ThemedScrollbar,
+    #[css(skip)]
+    ThemedScrollbarInactive,
+    #[css(skip)]
+    ThemedScrollbarThumb,
+    #[css(skip)]
+    ThemedScrollbarThumbHover,
+    #[css(skip)]
+    ThemedScrollbarThumbActive,
+    #[css(skip)]
+    ThemedScrollbarThumbInactive,
+
+    #[css(skip)]
+    End, // Just for array-indexing purposes.
+}
+
+#[cfg(feature = "gecko")]
+impl SystemColor {
+    #[inline]
+    fn compute(&self, cx: &Context) -> ComputedColor {
+        use crate::gecko::values::convert_nscolor_to_rgba;
+        use crate::gecko_bindings::bindings;
+
+        // TODO: We should avoid cloning here most likely, though it's
+        // cheap-ish.
+        let style_color_scheme = cx.style().get_inherited_ui().clone_color_scheme();
+        let color = cx.device().system_nscolor(*self, &style_color_scheme);
+        if color == bindings::NS_SAME_AS_FOREGROUND_COLOR {
+            return ComputedColor::currentcolor();
+        }
+        ComputedColor::rgba(convert_nscolor_to_rgba(color))
+    }
+}
+
+impl From<RGBA> for Color {
+    fn from(value: RGBA) -> Self {
+        Color::rgba(value)
+    }
+}
+
+struct ColorComponentParser<'a, 'b: 'a>(&'a ParserContext<'b>);
+impl<'a, 'b: 'a, 'i: 'a> ::cssparser::ColorComponentParser<'i> for ColorComponentParser<'a, 'b> {
+    type Error = StyleParseErrorKind<'i>;
+
+    fn parse_angle_or_number<'t>(
+        &self,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<AngleOrNumber, ParseError<'i>> {
+        use crate::values::specified::Angle;
+
+        let location = input.current_source_location();
+        let token = input.next()?.clone();
+        match token {
+            Token::Dimension {
+                value, ref unit, ..
+            } => {
+                let angle = Angle::parse_dimension(value, unit, /* from_calc = */ false);
+
+                let degrees = match angle {
+                    Ok(angle) => angle.degrees(),
+                    Err(()) => return Err(location.new_unexpected_token_error(token.clone())),
+                };
+
+                Ok(AngleOrNumber::Angle { degrees })
+            },
+            Token::Number { value, .. } => Ok(AngleOrNumber::Number { value }),
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                CalcNode::parse_angle_or_number(self.0, input, function)
+            },
+            t => return Err(location.new_unexpected_token_error(t)),
+        }
+    }
+
+    fn parse_percentage<'t>(&self, input: &mut Parser<'i, 't>) -> Result<f32, ParseError<'i>> {
+        Ok(Percentage::parse(self.0, input)?.get())
+    }
+
+    fn parse_number<'t>(&self, input: &mut Parser<'i, 't>) -> Result<f32, ParseError<'i>> {
+        use crate::values::specified::Number;
+
+        Ok(Number::parse(self.0, input)?.get())
+    }
+
+    fn parse_number_or_percentage<'t>(
+        &self,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<NumberOrPercentage, ParseError<'i>> {
+        let location = input.current_source_location();
+
+        match *input.next()? {
+            Token::Number { value, .. } => Ok(NumberOrPercentage::Number { value }),
+            Token::Percentage { unit_value, .. } => {
+                Ok(NumberOrPercentage::Percentage { unit_value })
+            },
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                CalcNode::parse_number_or_percentage(self.0, input, function)
+            },
+            ref t => return Err(location.new_unexpected_token_error(t.clone())),
+        }
+    }
+}
+
+/// Whether to preserve authored colors during parsing. That's useful only if we
+/// plan to serialize the color back.
+enum PreserveAuthored {
+    No,
+    Yes,
+}
+
+impl Parse for Color {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(context, input, PreserveAuthored::Yes)
+    }
+}
+
+impl Color {
+    fn parse_internal<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        preserve_authored: PreserveAuthored,
+    ) -> Result<Self, ParseError<'i>> {
+        let authored = match preserve_authored {
+            PreserveAuthored::No => None,
+            PreserveAuthored::Yes => {
+                // Currently we only store authored value for color keywords,
+                // because all browsers serialize those values as keywords for
+                // specified value.
+                let start = input.state();
+                let authored = input.expect_ident_cloned().ok();
+                input.reset(&start);
+                authored
+            }
+        };
+
+        let compontent_parser = ColorComponentParser(&*context);
+        match input.try_parse(|i| CSSParserColor::parse_with(&compontent_parser, i)) {
+            Ok(value) => Ok(match value {
+                CSSParserColor::CurrentColor => Color::CurrentColor,
+                CSSParserColor::RGBA(rgba) => Color::Numeric {
+                    parsed: rgba,
+                    authored: authored.map(|s| s.to_ascii_lowercase().into_boxed_str()),
+                },
+            }),
+            Err(e) => {
+                #[cfg(feature = "gecko")]
+                {
+                    if let Ok(system) = input.try_parse(|i| SystemColor::parse(context, i)) {
+                        return Ok(Color::System(system));
+                    }
+                }
+
+                if let Ok(mix) = input.try_parse(|i| ColorMix::parse(context, i, preserve_authored)) {
+                    return Ok(Color::ColorMix(Box::new(mix)));
+                }
+
+                match e.kind {
+                    ParseErrorKind::Basic(BasicParseErrorKind::UnexpectedToken(t)) => {
+                        Err(e.location.new_custom_error(StyleParseErrorKind::ValueError(
+                            ValueParseErrorKind::InvalidColor(t),
+                        )))
+                    },
+                    _ => Err(e),
+                }
+            },
+        }
+    }
+
+    /// Returns whether a given color is valid for authors.
+    pub fn is_valid(context: &ParserContext, input: &mut Parser) -> bool {
+        input.parse_entirely(|input| Self::parse_internal(context, input, PreserveAuthored::No)).is_ok()
+    }
+
+    /// Tries to parse a color and compute it with a given device.
+    pub fn parse_and_compute(
+        context: &ParserContext,
+        input: &mut Parser,
+        device: Option<&Device>,
+    ) -> Option<ComputedColor> {
+        use crate::error_reporting::ContextualParseError;
+        let start = input.position();
+        let result = input.parse_entirely(|input| {
+            Self::parse_internal(context, input, PreserveAuthored::No)
+        });
+
+        let specified = match result {
+            Ok(s) => s,
+            Err(e) => {
+                if !context.error_reporting_enabled() {
+                    return None;
+                }
+                // Ignore other kinds of errors that might be reported, such as
+                // ParseErrorKind::Basic(BasicParseErrorKind::UnexpectedToken),
+                // since Gecko didn't use to report those to the error console.
+                //
+                // TODO(emilio): Revise whether we want to keep this at all, we
+                // use this only for canvas, this warnings are disabled by
+                // default and not available on OffscreenCanvas anyways...
+                if let ParseErrorKind::Custom(StyleParseErrorKind::ValueError(..)) = e.kind {
+                    let location = e.location.clone();
+                    let error = ContextualParseError::UnsupportedValue(
+                        input.slice_from(start),
+                        e,
+                    );
+                    context.log_css_error(location, error);
+                }
+                return None;
+            }
+        };
+
+        match device {
+            Some(device) => {
+                Context::for_media_query_evaluation(device, device.quirks_mode(), |context| {
+                    specified.to_computed_color(Some(&context))
+                })
+            },
+            None => specified.to_computed_color(None),
+        }
+    }
+}
+
+impl ToCss for Color {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            Color::CurrentColor => CSSParserColor::CurrentColor.to_css(dest),
+            Color::Numeric {
+                authored: Some(ref authored),
+                ..
+            } => dest.write_str(authored),
+            Color::Numeric {
+                parsed: ref rgba, ..
+            } => rgba.to_css(dest),
+            Color::ColorMix(ref mix) => mix.to_css(dest),
+            #[cfg(feature = "gecko")]
+            Color::System(system) => system.to_css(dest),
+            #[cfg(feature = "gecko")]
+            Color::InheritFromBodyQuirk => Ok(()),
+        }
+    }
+}
+
+/// A wrapper of cssparser::Color::parse_hash.
+///
+/// That function should never return CurrentColor, so it makes no sense to
+/// handle a cssparser::Color here. This should really be done in cssparser
+/// directly rather than here.
+fn parse_hash_color(value: &[u8]) -> Result<RGBA, ()> {
+    CSSParserColor::parse_hash(value).map(|color| match color {
+        CSSParserColor::RGBA(rgba) => rgba,
+        CSSParserColor::CurrentColor => unreachable!("parse_hash should never return currentcolor"),
+    })
+}
+
+impl Color {
+    /// Returns whether this color is allowed in forced-colors mode.
+    pub fn honored_in_forced_colors_mode(&self, allow_transparent: bool) -> bool {
+        match *self {
+            Color::InheritFromBodyQuirk => false,
+            Color::CurrentColor | Color::System(..) => true,
+            Color::Numeric { ref parsed, .. } => allow_transparent && parsed.alpha == 0,
+            Color::ColorMix(ref mix) => {
+                mix.left.honored_in_forced_colors_mode(allow_transparent) &&
+                    mix.right.honored_in_forced_colors_mode(allow_transparent)
+            },
+        }
+    }
+
+    /// Returns currentcolor value.
+    #[inline]
+    pub fn currentcolor() -> Color {
+        Color::CurrentColor
+    }
+
+    /// Returns transparent value.
+    #[inline]
+    pub fn transparent() -> Color {
+        // We should probably set authored to "transparent", but maybe it doesn't matter.
+        Color::rgba(RGBA::transparent())
+    }
+
+    /// Returns a numeric RGBA color value.
+    #[inline]
+    pub fn rgba(rgba: RGBA) -> Self {
+        Color::Numeric {
+            parsed: rgba,
+            authored: None,
+        }
+    }
+
+    /// Parse a color, with quirks.
+    ///
+    /// <https://quirks.spec.whatwg.org/#the-hashless-hex-color-quirk>
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        input.try_parse(|i| Self::parse(context, i)).or_else(|e| {
+            if !allow_quirks.allowed(context.quirks_mode) {
+                return Err(e);
+            }
+            Color::parse_quirky_color(input)
+                .map(Color::rgba)
+                .map_err(|_| e)
+        })
+    }
+
+    /// Parse a <quirky-color> value.
+    ///
+    /// <https://quirks.spec.whatwg.org/#the-hashless-hex-color-quirk>
+    fn parse_quirky_color<'i, 't>(input: &mut Parser<'i, 't>) -> Result<RGBA, ParseError<'i>> {
+        let location = input.current_source_location();
+        let (value, unit) = match *input.next()? {
+            Token::Number {
+                int_value: Some(integer),
+                ..
+            } => (integer, None),
+            Token::Dimension {
+                int_value: Some(integer),
+                ref unit,
+                ..
+            } => (integer, Some(unit)),
+            Token::Ident(ref ident) => {
+                if ident.len() != 3 && ident.len() != 6 {
+                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+                return parse_hash_color(ident.as_bytes()).map_err(|()| {
+                    location.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                });
+            },
+            ref t => {
+                return Err(location.new_unexpected_token_error(t.clone()));
+            },
+        };
+        if value < 0 {
+            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        let length = if value <= 9 {
+            1
+        } else if value <= 99 {
+            2
+        } else if value <= 999 {
+            3
+        } else if value <= 9999 {
+            4
+        } else if value <= 99999 {
+            5
+        } else if value <= 999999 {
+            6
+        } else {
+            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        };
+        let total = length + unit.as_ref().map_or(0, |d| d.len());
+        if total > 6 {
+            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        let mut serialization = [b'0'; 6];
+        let space_padding = 6 - total;
+        let mut written = space_padding;
+        let mut buf = itoa::Buffer::new();
+        let s = buf.format(value);
+        (&mut serialization[written..])
+            .write_all(s.as_bytes())
+            .unwrap();
+        written += s.len();
+        if let Some(unit) = unit {
+            written += (&mut serialization[written..])
+                .write(unit.as_bytes())
+                .unwrap();
+        }
+        debug_assert_eq!(written, 6);
+        parse_hash_color(&serialization)
+            .map_err(|()| location.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+impl Color {
+    /// Converts this Color into a ComputedColor.
+    ///
+    /// If `context` is `None`, and the specified color requires data from
+    /// the context to resolve, then `None` is returned.
+    pub fn to_computed_color(&self, context: Option<&Context>) -> Option<ComputedColor> {
+        Some(match *self {
+            Color::CurrentColor => ComputedColor::CurrentColor,
+            Color::Numeric { ref parsed, .. } => ComputedColor::Numeric(*parsed),
+            Color::ColorMix(ref mix) => {
+                use crate::values::computed::percentage::Percentage;
+
+                let left = mix.left.to_computed_color(context)?;
+                let right = mix.right.to_computed_color(context)?;
+                let mut color = ComputedColor::ColorMix(Box::new(GenericColorMix {
+                    interpolation: mix.interpolation,
+                    left,
+                    left_percentage: Percentage(mix.left_percentage.get()),
+                    right,
+                    right_percentage: Percentage(mix.right_percentage.get()),
+                    normalize_weights: mix.normalize_weights,
+                }));
+                color.simplify(None);
+                color
+            },
+            #[cfg(feature = "gecko")]
+            Color::System(system) => system.compute(context?),
+            #[cfg(feature = "gecko")]
+            Color::InheritFromBodyQuirk => ComputedColor::rgba(context?.device().body_text_color()),
+        })
+    }
+}
+
+impl ToComputedValue for Color {
+    type ComputedValue = ComputedColor;
+
+    fn to_computed_value(&self, context: &Context) -> ComputedColor {
+        self.to_computed_color(Some(context)).unwrap()
+    }
+
+    fn from_computed_value(computed: &ComputedColor) -> Self {
+        match *computed {
+            ComputedColor::Numeric(ref color) => Color::rgba(*color),
+            ComputedColor::CurrentColor => Color::CurrentColor,
+            ComputedColor::ColorMix(ref mix) => {
+                Color::ColorMix(Box::new(ToComputedValue::from_computed_value(&**mix)))
+            },
+        }
+    }
+}
+
+/// Specified color value for `-moz-font-smoothing-background-color`.
+///
+/// This property does not support `currentcolor`. We could drop it at
+/// parse-time, but it's not exposed to the web so it doesn't really matter.
+///
+/// We resolve it to `transparent` instead.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub struct MozFontSmoothingBackgroundColor(pub Color);
+
+impl Parse for MozFontSmoothingBackgroundColor {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Color::parse(context, input).map(MozFontSmoothingBackgroundColor)
+    }
+}
+
+impl ToComputedValue for MozFontSmoothingBackgroundColor {
+    type ComputedValue = RGBA;
+
+    fn to_computed_value(&self, context: &Context) -> RGBA {
+        self.0
+            .to_computed_value(context)
+            .into_rgba(RGBA::transparent())
+    }
+
+    fn from_computed_value(computed: &RGBA) -> Self {
+        MozFontSmoothingBackgroundColor(Color::rgba(*computed))
+    }
+}
+
+impl SpecifiedValueInfo for Color {
+    const SUPPORTED_TYPES: u8 = CssType::COLOR;
+
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        // We are not going to insert all the color names here. Caller and
+        // devtools should take care of them. XXX Actually, transparent
+        // should probably be handled that way as well.
+        // XXX `currentColor` should really be `currentcolor`. But let's
+        // keep it consistent with the old system for now.
+        f(&[
+            "rgb",
+            "rgba",
+            "hsl",
+            "hsla",
+            "hwb",
+            "currentColor",
+            "transparent",
+        ]);
+        if static_prefs::pref!("layout.css.color-mix.enabled") {
+            f(&["color-mix"]);
+        }
+    }
+}
+
+/// Specified value for the "color" property, which resolves the `currentcolor`
+/// keyword to the parent color instead of self's color.
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
+#[derive(Clone, Debug, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub struct ColorPropertyValue(pub Color);
+
+impl ToComputedValue for ColorPropertyValue {
+    type ComputedValue = RGBA;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> RGBA {
+        self.0
+            .to_computed_value(context)
+            .into_rgba(context.builder.get_parent_inherited_text().clone_color())
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &RGBA) -> Self {
+        ColorPropertyValue(Color::rgba(*computed).into())
+    }
+}
+
+impl Parse for ColorPropertyValue {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Color::parse_quirky(context, input, AllowQuirks::Yes).map(ColorPropertyValue)
+    }
+}
+
+/// auto | <color>
+pub type ColorOrAuto = GenericColorOrAuto<Color>;
+
+/// caret-color
+pub type CaretColor = GenericCaretColor<Color>;
+
+impl Parse for CaretColor {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        ColorOrAuto::parse(context, input).map(GenericCaretColor)
+    }
+}
+
+bitflags! {
+    /// Various flags to represent the color-scheme property in an efficient
+    /// way.
+    #[derive(Default, MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[repr(C)]
+    #[value_info(other_values = "light,dark,only")]
+    pub struct ColorSchemeFlags: u8 {
+        /// Whether the author specified `light`.
+        const LIGHT = 1 << 0;
+        /// Whether the author specified `dark`.
+        const DARK = 1 << 1;
+        /// Whether the author specified `only`.
+        const ONLY = 1 << 2;
+    }
+}
+
+/// <https://drafts.csswg.org/css-color-adjust/#color-scheme-prop>
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+#[value_info(other_values = "normal")]
+pub struct ColorScheme {
+    #[ignore_malloc_size_of = "Arc"]
+    idents: crate::ArcSlice<CustomIdent>,
+    bits: ColorSchemeFlags,
+}
+
+impl ColorScheme {
+    /// Returns the `normal` value.
+    pub fn normal() -> Self {
+        Self {
+            idents: Default::default(),
+            bits: ColorSchemeFlags::empty(),
+        }
+    }
+
+    /// Returns the raw bitfield.
+    pub fn raw_bits(&self) -> u8 {
+        self.bits.bits
+    }
+}
+
+impl Parse for ColorScheme {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut idents = vec![];
+        let mut bits = ColorSchemeFlags::empty();
+
+        let mut location = input.current_source_location();
+        while let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            let mut is_only = false;
+            match_ignore_ascii_case! { &ident,
+                "normal" => {
+                    if idents.is_empty() && bits.is_empty() {
+                        return Ok(Self::normal());
+                    }
+                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                },
+                "light" => bits.insert(ColorSchemeFlags::LIGHT),
+                "dark" => bits.insert(ColorSchemeFlags::DARK),
+                "only" => {
+                    if bits.intersects(ColorSchemeFlags::ONLY) {
+                        return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                    }
+                    bits.insert(ColorSchemeFlags::ONLY);
+                    is_only = true;
+                },
+                _ => {},
+            };
+
+            if is_only {
+                if !idents.is_empty() {
+                    // Only is allowed either at the beginning or at the end,
+                    // but not in the middle.
+                    break;
+                }
+            } else {
+                idents.push(CustomIdent::from_ident(location, &ident, &[])?);
+            }
+            location = input.current_source_location();
+        }
+
+        if idents.is_empty() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(Self {
+            idents: crate::ArcSlice::from_iter(idents.into_iter()),
+            bits,
+        })
+    }
+}
+
+impl ToCss for ColorScheme {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.idents.is_empty() {
+            debug_assert!(self.bits.is_empty());
+            return dest.write_str("normal");
+        }
+        let mut first = true;
+        for ident in self.idents.iter() {
+            if !first {
+                dest.write_char(' ')?;
+            }
+            first = false;
+            ident.to_css(dest)?;
+        }
+        if self.bits.intersects(ColorSchemeFlags::ONLY) {
+            dest.write_str(" only")?;
+        }
+        Ok(())
+    }
+}
+
+/// https://drafts.csswg.org/css-color-adjust/#print-color-adjust
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum PrintColorAdjust {
+    /// Ignore backgrounds and darken text.
+    Economy,
+    /// Respect specified colors.
+    Exact,
+}
diff --git a/servo/components/style/values/specified/column.rs b/servo/components/style/values/specified/column.rs
new file mode 100644
index 0000000000..2dd7bb0144
--- /dev/null
+++ b/servo/components/style/values/specified/column.rs
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for the column properties.
+
+use crate::values::generics::column::ColumnCount as GenericColumnCount;
+use crate::values::specified::PositiveInteger;
+
+/// A specified type for `column-count` values.
+pub type ColumnCount = GenericColumnCount<PositiveInteger>;
diff --git a/servo/components/style/values/specified/counters.rs b/servo/components/style/values/specified/counters.rs
new file mode 100644
index 0000000000..804a519556
--- /dev/null
+++ b/servo/components/style/values/specified/counters.rs
@@ -0,0 +1,303 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for counter properties.
+
+#[cfg(feature = "servo-layout-2013")]
+use crate::computed_values::list_style_type::T as ListStyleType;
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::counters as generics;
+use crate::values::generics::counters::CounterPair;
+#[cfg(feature = "gecko")]
+use crate::values::generics::CounterStyle;
+use crate::values::specified::image::Image;
+#[cfg(any(feature = "gecko", feature = "servo-layout-2020"))]
+use crate::values::specified::Attr;
+use crate::values::specified::Integer;
+use crate::values::CustomIdent;
+use cssparser::{Parser, Token};
+#[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+use selectors::parser::SelectorParseErrorKind;
+use style_traits::{KeywordsCollectFn, ParseError, SpecifiedValueInfo, StyleParseErrorKind};
+
+#[derive(PartialEq)]
+enum CounterType {
+    Increment,
+    Set,
+    Reset,
+}
+
+impl CounterType {
+    fn default_value(&self) -> i32 {
+        match *self {
+            Self::Increment => 1,
+            Self::Reset | Self::Set => 0,
+        }
+    }
+}
+
+/// A specified value for the `counter-increment` property.
+pub type CounterIncrement = generics::GenericCounterIncrement<Integer>;
+
+impl Parse for CounterIncrement {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(Self::new(parse_counters(
+            context,
+            input,
+            CounterType::Increment,
+        )?))
+    }
+}
+
+/// A specified value for the `counter-set` property.
+pub type CounterSet = generics::GenericCounterSet<Integer>;
+
+impl Parse for CounterSet {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(Self::new(parse_counters(context, input, CounterType::Set)?))
+    }
+}
+
+/// A specified value for the `counter-reset` property.
+pub type CounterReset = generics::GenericCounterReset<Integer>;
+
+impl Parse for CounterReset {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(Self::new(parse_counters(
+            context,
+            input,
+            CounterType::Reset,
+        )?))
+    }
+}
+
+fn parse_counters<'i, 't>(
+    context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+    counter_type: CounterType,
+) -> Result<Vec<CounterPair<Integer>>, ParseError<'i>> {
+    if input
+        .try_parse(|input| input.expect_ident_matching("none"))
+        .is_ok()
+    {
+        return Ok(vec![]);
+    }
+
+    let mut counters = Vec::new();
+    loop {
+        let location = input.current_source_location();
+        let (name, is_reversed) = match input.next() {
+            Ok(&Token::Ident(ref ident)) => {
+                (CustomIdent::from_ident(location, ident, &["none"])?, false)
+            },
+            Ok(&Token::Function(ref name))
+                if counter_type == CounterType::Reset && name.eq_ignore_ascii_case("reversed") =>
+            {
+                input.parse_nested_block(|input| {
+                    let location = input.current_source_location();
+                    Ok((
+                        CustomIdent::from_ident(location, input.expect_ident()?, &["none"])?,
+                        true,
+                    ))
+                })?
+            },
+            Ok(t) => {
+                let t = t.clone();
+                return Err(location.new_unexpected_token_error(t));
+            },
+            Err(_) => break,
+        };
+
+        let value = match input.try_parse(|input| Integer::parse(context, input)) {
+            Ok(start) => {
+                if start.value == i32::min_value() {
+                    // The spec says that values must be clamped to the valid range,
+                    // and we reserve i32::min_value() as an internal magic value.
+                    // https://drafts.csswg.org/css-lists/#auto-numbering
+                    Integer::new(i32::min_value() + 1)
+                } else {
+                    start
+                }
+            },
+            _ => Integer::new(if is_reversed {
+                i32::min_value()
+            } else {
+                counter_type.default_value()
+            }),
+        };
+        counters.push(CounterPair {
+            name,
+            value,
+            is_reversed,
+        });
+    }
+
+    if !counters.is_empty() {
+        Ok(counters)
+    } else {
+        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+/// The specified value for the `content` property.
+pub type Content = generics::GenericContent<Image>;
+
+/// The specified value for a content item in the `content` property.
+pub type ContentItem = generics::GenericContentItem<Image>;
+
+impl Content {
+    #[cfg(feature = "servo-layout-2013")]
+    fn parse_counter_style(_: &ParserContext, input: &mut Parser) -> ListStyleType {
+        input
+            .try_parse(|input| {
+                input.expect_comma()?;
+                ListStyleType::parse(input)
+            })
+            .unwrap_or(ListStyleType::Decimal)
+    }
+
+    #[cfg(feature = "gecko")]
+    fn parse_counter_style(context: &ParserContext, input: &mut Parser) -> CounterStyle {
+        input
+            .try_parse(|input| {
+                input.expect_comma()?;
+                CounterStyle::parse(context, input)
+            })
+            .unwrap_or(CounterStyle::decimal())
+    }
+}
+
+impl Parse for Content {
+    // normal | none | [ <string> | <counter> | open-quote | close-quote | no-open-quote |
+    // no-close-quote ]+
+    // TODO: <uri>, attr(<identifier>)
+    #[cfg_attr(feature = "servo", allow(unused_mut))]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(generics::Content::Normal);
+        }
+        if input
+            .try_parse(|input| input.expect_ident_matching("none"))
+            .is_ok()
+        {
+            return Ok(generics::Content::None);
+        }
+
+        let mut content = vec![];
+        let mut has_alt_content = false;
+        loop {
+            #[cfg(any(feature = "gecko", feature = "servo-layout-2020"))]
+            {
+                if let Ok(image) = input.try_parse(|i| Image::parse_only_url(context, i)) {
+                    content.push(generics::ContentItem::Image(image));
+                    continue;
+                }
+            }
+            match input.next() {
+                Ok(&Token::QuotedString(ref value)) => {
+                    content.push(generics::ContentItem::String(
+                        value.as_ref().to_owned().into(),
+                    ));
+                },
+                Ok(&Token::Function(ref name)) => {
+                    let result = match_ignore_ascii_case! { &name,
+                        #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+                        "counter" => input.parse_nested_block(|input| {
+                            let location = input.current_source_location();
+                            let name = CustomIdent::from_ident(location, input.expect_ident()?, &[])?;
+                            let style = Content::parse_counter_style(context, input);
+                            Ok(generics::ContentItem::Counter(name, style))
+                        }),
+                        #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+                        "counters" => input.parse_nested_block(|input| {
+                            let location = input.current_source_location();
+                            let name = CustomIdent::from_ident(location, input.expect_ident()?, &[])?;
+                            input.expect_comma()?;
+                            let separator = input.expect_string()?.as_ref().to_owned().into();
+                            let style = Content::parse_counter_style(context, input);
+                            Ok(generics::ContentItem::Counters(name, separator, style))
+                        }),
+                        #[cfg(any(feature = "gecko", feature = "servo-layout-2020"))]
+                        "attr" => input.parse_nested_block(|input| {
+                            Ok(generics::ContentItem::Attr(Attr::parse_function(context, input)?))
+                        }),
+                        _ => {
+                            use style_traits::StyleParseErrorKind;
+                            let name = name.clone();
+                            return Err(input.new_custom_error(
+                                StyleParseErrorKind::UnexpectedFunction(name),
+                            ))
+                        }
+                    }?;
+                    content.push(result);
+                },
+                #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+                Ok(&Token::Ident(ref ident)) => {
+                    content.push(match_ignore_ascii_case! { &ident,
+                        "open-quote" => generics::ContentItem::OpenQuote,
+                        "close-quote" => generics::ContentItem::CloseQuote,
+                        "no-open-quote" => generics::ContentItem::NoOpenQuote,
+                        "no-close-quote" => generics::ContentItem::NoCloseQuote,
+                        #[cfg(feature = "gecko")]
+                        "-moz-alt-content" => {
+                            has_alt_content = true;
+                            generics::ContentItem::MozAltContent
+                        },
+                        "-moz-label-content" if context.chrome_rules_enabled() => {
+                            generics::ContentItem::MozLabelContent
+                        },
+                        _ =>{
+                            let ident = ident.clone();
+                            return Err(input.new_custom_error(
+                                SelectorParseErrorKind::UnexpectedIdent(ident)
+                            ));
+                        }
+                    });
+                },
+                Err(_) => break,
+                Ok(t) => {
+                    let t = t.clone();
+                    return Err(input.new_unexpected_token_error(t));
+                },
+            }
+        }
+        // We don't allow to parse `-moz-alt-content` in multiple positions.
+        if content.is_empty() || (has_alt_content && content.len() != 1) {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        Ok(generics::Content::Items(content.into()))
+    }
+}
+
+impl<Image> SpecifiedValueInfo for generics::GenericContentItem<Image> {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&[
+            "url",
+            "image-set",
+            "counter",
+            "counters",
+            "attr",
+            "open-quote",
+            "close-quote",
+            "no-open-quote",
+            "no-close-quote",
+            "-moz-alt-content",
+        ]);
+    }
+}
diff --git a/servo/components/style/values/specified/easing.rs b/servo/components/style/values/specified/easing.rs
new file mode 100644
index 0000000000..e10eb0b98b
--- /dev/null
+++ b/servo/components/style/values/specified/easing.rs
@@ -0,0 +1,251 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS Easing functions.
+use crate::parser::{Parse, ParserContext};
+use crate::piecewise_linear::{PiecewiseLinearFunction, PiecewiseLinearFunctionBuildParameters};
+use crate::values::computed::easing::TimingFunction as ComputedTimingFunction;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics::easing::TimingFunction as GenericTimingFunction;
+use crate::values::generics::easing::{StepPosition, TimingKeyword};
+use crate::values::specified::{Integer, Number, Percentage};
+use cssparser::{Delimiter, Parser, Token};
+use selectors::parser::SelectorParseErrorKind;
+use std::iter::FromIterator;
+use style_traits::{ParseError, StyleParseErrorKind};
+
+/// An entry for linear easing function.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub struct LinearStop {
+    /// Output of the function at the given point.
+    pub output: Number,
+    /// Playback progress at which this output is given.
+    #[css(skip_if = "Option::is_none")]
+    pub input: Option<Percentage>,
+}
+
+/// A list of specified linear stops.
+#[derive(Clone, Default, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+#[css(comma)]
+pub struct LinearStops {
+    #[css(iterable)]
+    entries: crate::OwnedSlice<LinearStop>,
+}
+
+impl LinearStops {
+    fn new(list: crate::OwnedSlice<LinearStop>) -> Self {
+        LinearStops { entries: list }
+    }
+}
+
+/// A specified timing function.
+pub type TimingFunction = GenericTimingFunction<Integer, Number, LinearStops>;
+
+#[cfg(feature = "gecko")]
+fn linear_timing_function_enabled() -> bool {
+    static_prefs::pref!("layout.css.linear-easing-function.enabled")
+}
+
+#[cfg(feature = "servo")]
+fn linear_timing_function_enabled() -> bool {
+    false
+}
+
+impl Parse for TimingFunction {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(keyword) = input.try_parse(TimingKeyword::parse) {
+            return Ok(GenericTimingFunction::Keyword(keyword));
+        }
+        if let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            let position = match_ignore_ascii_case! { &ident,
+                "step-start" => StepPosition::Start,
+                "step-end" => StepPosition::End,
+                _ => {
+                    return Err(input.new_custom_error(
+                        SelectorParseErrorKind::UnexpectedIdent(ident.clone())
+                    ));
+                },
+            };
+            return Ok(GenericTimingFunction::Steps(Integer::new(1), position));
+        }
+        let location = input.current_source_location();
+        let function = input.expect_function()?.clone();
+        input.parse_nested_block(move |i| {
+            match_ignore_ascii_case! { &function,
+                "cubic-bezier" => Self::parse_cubic_bezier(context, i),
+                "steps" => Self::parse_steps(context, i),
+                "linear" => Self::parse_linear_function(context, i),
+                _ => Err(location.new_custom_error(StyleParseErrorKind::UnexpectedFunction(function.clone()))),
+            }
+        })
+    }
+}
+
+impl TimingFunction {
+    fn parse_cubic_bezier<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let x1 = Number::parse(context, input)?;
+        input.expect_comma()?;
+        let y1 = Number::parse(context, input)?;
+        input.expect_comma()?;
+        let x2 = Number::parse(context, input)?;
+        input.expect_comma()?;
+        let y2 = Number::parse(context, input)?;
+
+        if x1.get() < 0.0 || x1.get() > 1.0 || x2.get() < 0.0 || x2.get() > 1.0 {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(GenericTimingFunction::CubicBezier { x1, y1, x2, y2 })
+    }
+
+    fn parse_steps<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let steps = Integer::parse_positive(context, input)?;
+        let position = input
+            .try_parse(|i| {
+                i.expect_comma()?;
+                StepPosition::parse(context, i)
+            })
+            .unwrap_or(StepPosition::End);
+
+        // jump-none accepts a positive integer greater than 1.
+        // FIXME(emilio): The spec asks us to avoid rejecting it at parse
+        // time except until computed value time.
+        //
+        // It's not totally clear it's worth it though, and no other browser
+        // does this.
+        if position == StepPosition::JumpNone && steps.value() <= 1 {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        Ok(GenericTimingFunction::Steps(steps, position))
+    }
+
+    fn parse_linear_function<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if !linear_timing_function_enabled() {
+            return Err(input.new_custom_error(StyleParseErrorKind::ExperimentalProperty));
+        }
+        if input.is_exhausted() {
+            return Ok(GenericTimingFunction::LinearFunction(LinearStops::default()));
+        }
+        let mut result = vec![];
+        loop {
+            input.parse_until_before(Delimiter::Comma, |i| {
+                let mut input_start = i.try_parse(|i| Percentage::parse(context, i)).ok();
+                let mut input_end = i.try_parse(|i| Percentage::parse(context, i)).ok();
+
+                let output = Number::parse(context, i)?;
+                if input_start.is_none() {
+                    debug_assert!(input_end.is_none(), "Input end parsed without input start?");
+                    input_start = i.try_parse(|i| Percentage::parse(context, i)).ok();
+                    input_end = i.try_parse(|i| Percentage::parse(context, i)).ok();
+                }
+                result.push(LinearStop {
+                    output,
+                    input: input_start.into(),
+                });
+                if input_end.is_some() {
+                    debug_assert!(
+                        input_start.is_some(),
+                        "Input end valid but not input start?"
+                    );
+                    result.push(LinearStop {
+                        output,
+                        input: input_end.into(),
+                    });
+                }
+
+                Ok(())
+            })?;
+
+            match input.next() {
+                Err(_) => break,
+                Ok(&Token::Comma) => continue,
+                Ok(_) => unreachable!(),
+            }
+        }
+
+        Ok(GenericTimingFunction::LinearFunction(LinearStops::new(
+            crate::OwnedSlice::from(result),
+        )))
+    }
+}
+
+impl LinearStop {
+    /// Convert this type to entries that can be used to build PiecewiseLinearFunction.
+    pub fn to_piecewise_linear_build_parameters(
+        x: &LinearStop,
+    ) -> PiecewiseLinearFunctionBuildParameters {
+        (x.output.get(), x.input.map(|x| x.get()))
+    }
+}
+
+// We need this for converting the specified TimingFunction into computed TimingFunction without
+// Context (for some FFIs in glue.rs). In fact, we don't really need Context to get the computed
+// value of TimingFunction.
+impl TimingFunction {
+    /// Generate the ComputedTimingFunction without Context.
+    pub fn to_computed_value_without_context(&self) -> ComputedTimingFunction {
+        match &self {
+            GenericTimingFunction::Steps(steps, pos) => {
+                GenericTimingFunction::Steps(steps.value(), *pos)
+            },
+            GenericTimingFunction::CubicBezier { x1, y1, x2, y2 } => {
+                GenericTimingFunction::CubicBezier {
+                    x1: x1.get(),
+                    y1: y1.get(),
+                    x2: x2.get(),
+                    y2: y2.get(),
+                }
+            },
+            GenericTimingFunction::Keyword(keyword) => GenericTimingFunction::Keyword(*keyword),
+            GenericTimingFunction::LinearFunction(steps) => {
+                GenericTimingFunction::LinearFunction(PiecewiseLinearFunction::from_iter(
+                    steps
+                        .entries
+                        .iter()
+                        .map(|e| LinearStop::to_piecewise_linear_build_parameters(e)),
+                ))
+            },
+        }
+    }
+}
+
+impl ToComputedValue for TimingFunction {
+    type ComputedValue = ComputedTimingFunction;
+    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
+        self.to_computed_value_without_context()
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        match &computed {
+            ComputedTimingFunction::Steps(steps, pos) => Self::Steps(Integer::new(*steps), *pos),
+            ComputedTimingFunction::CubicBezier { x1, y1, x2, y2 } => Self::CubicBezier {
+                x1: Number::new(*x1),
+                y1: Number::new(*y1),
+                x2: Number::new(*x2),
+                y2: Number::new(*y2),
+            },
+            ComputedTimingFunction::Keyword(keyword) => GenericTimingFunction::Keyword(*keyword),
+            ComputedTimingFunction::LinearFunction(function) => {
+                GenericTimingFunction::LinearFunction(LinearStops {
+                    entries: crate::OwnedSlice::from_iter(function.iter().map(|e| LinearStop {
+                        output: Number::new(e.y),
+                        input: Some(Percentage::new(e.x)).into(),
+                    })),
+                })
+            },
+        }
+    }
+}
diff --git a/servo/components/style/values/specified/effects.rs b/servo/components/style/values/specified/effects.rs
new file mode 100644
index 0000000000..fd92e6ee95
--- /dev/null
+++ b/servo/components/style/values/specified/effects.rs
@@ -0,0 +1,362 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS values related to effects.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::effects::BoxShadow as ComputedBoxShadow;
+use crate::values::computed::effects::SimpleShadow as ComputedSimpleShadow;
+use crate::values::computed::NonNegativeNumber as ComputedNonNegativeNumber;
+use crate::values::computed::ZeroToOneNumber as ComputedZeroToOneNumber;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics::effects::BoxShadow as GenericBoxShadow;
+use crate::values::generics::effects::Filter as GenericFilter;
+use crate::values::generics::effects::SimpleShadow as GenericSimpleShadow;
+use crate::values::generics::NonNegative;
+use crate::values::specified::color::Color;
+use crate::values::specified::length::{Length, NonNegativeLength};
+#[cfg(feature = "gecko")]
+use crate::values::specified::url::SpecifiedUrl;
+use crate::values::specified::{Angle, Number, NumberOrPercentage};
+#[cfg(feature = "servo")]
+use crate::values::Impossible;
+use crate::Zero;
+use cssparser::{self, BasicParseErrorKind, Parser, Token};
+use style_traits::{ParseError, StyleParseErrorKind, ValueParseErrorKind};
+
+/// A specified value for a single shadow of the `box-shadow` property.
+pub type BoxShadow =
+    GenericBoxShadow<Option<Color>, Length, Option<NonNegativeLength>, Option<Length>>;
+
+/// A specified value for a single `filter`.
+#[cfg(feature = "gecko")]
+pub type SpecifiedFilter = GenericFilter<
+    Angle,
+    NonNegativeFactor,
+    ZeroToOneFactor,
+    NonNegativeLength,
+    SimpleShadow,
+    SpecifiedUrl,
+>;
+
+/// A specified value for a single `filter`.
+#[cfg(feature = "servo")]
+pub type SpecifiedFilter = GenericFilter<
+    Angle,
+    NonNegativeFactor,
+    ZeroToOneFactor,
+    NonNegativeLength,
+    Impossible,
+    Impossible,
+>;
+
+pub use self::SpecifiedFilter as Filter;
+
+/// A value for the `<factor>` parts in `Filter`.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub struct NonNegativeFactor(NumberOrPercentage);
+
+/// A value for the `<factor>` parts in `Filter` which clamps to one.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub struct ZeroToOneFactor(NumberOrPercentage);
+
+/// Clamp the value to 1 if the value is over 100%.
+#[inline]
+fn clamp_to_one(number: NumberOrPercentage) -> NumberOrPercentage {
+    match number {
+        NumberOrPercentage::Percentage(percent) => {
+            NumberOrPercentage::Percentage(percent.clamp_to_hundred())
+        },
+        NumberOrPercentage::Number(number) => NumberOrPercentage::Number(number.clamp_to_one()),
+    }
+}
+
+macro_rules! factor_impl_common {
+    ($ty:ty, $computed_ty:ty) => {
+        impl $ty {
+            fn one() -> Self {
+                Self(NumberOrPercentage::Number(Number::new(1.)))
+            }
+        }
+
+        impl ToComputedValue for $ty {
+            type ComputedValue = $computed_ty;
+
+            #[inline]
+            fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+                use crate::values::computed::NumberOrPercentage;
+                match self.0.to_computed_value(context) {
+                    NumberOrPercentage::Number(n) => n.into(),
+                    NumberOrPercentage::Percentage(p) => p.0.into(),
+                }
+            }
+
+            #[inline]
+            fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+                Self(NumberOrPercentage::Number(
+                    ToComputedValue::from_computed_value(&computed.0),
+                ))
+            }
+        }
+    };
+}
+factor_impl_common!(NonNegativeFactor, ComputedNonNegativeNumber);
+factor_impl_common!(ZeroToOneFactor, ComputedZeroToOneNumber);
+
+impl Parse for NonNegativeFactor {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        NumberOrPercentage::parse_non_negative(context, input).map(Self)
+    }
+}
+
+impl Parse for ZeroToOneFactor {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        NumberOrPercentage::parse_non_negative(context, input)
+            .map(clamp_to_one)
+            .map(Self)
+    }
+}
+
+/// A specified value for the `drop-shadow()` filter.
+pub type SimpleShadow = GenericSimpleShadow<Option<Color>, Length, Option<NonNegativeLength>>;
+
+impl Parse for BoxShadow {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut lengths = None;
+        let mut color = None;
+        let mut inset = false;
+
+        loop {
+            if !inset {
+                if input
+                    .try_parse(|input| input.expect_ident_matching("inset"))
+                    .is_ok()
+                {
+                    inset = true;
+                    continue;
+                }
+            }
+            if lengths.is_none() {
+                let value = input.try_parse::<_, _, ParseError>(|i| {
+                    let horizontal = Length::parse(context, i)?;
+                    let vertical = Length::parse(context, i)?;
+                    let (blur, spread) =
+                        match i.try_parse(|i| Length::parse_non_negative(context, i)) {
+                            Ok(blur) => {
+                                let spread = i.try_parse(|i| Length::parse(context, i)).ok();
+                                (Some(blur.into()), spread)
+                            },
+                            Err(_) => (None, None),
+                        };
+                    Ok((horizontal, vertical, blur, spread))
+                });
+                if let Ok(value) = value {
+                    lengths = Some(value);
+                    continue;
+                }
+            }
+            if color.is_none() {
+                if let Ok(value) = input.try_parse(|i| Color::parse(context, i)) {
+                    color = Some(value);
+                    continue;
+                }
+            }
+            break;
+        }
+
+        let lengths =
+            lengths.ok_or(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))?;
+        Ok(BoxShadow {
+            base: SimpleShadow {
+                color: color,
+                horizontal: lengths.0,
+                vertical: lengths.1,
+                blur: lengths.2,
+            },
+            spread: lengths.3,
+            inset: inset,
+        })
+    }
+}
+
+impl ToComputedValue for BoxShadow {
+    type ComputedValue = ComputedBoxShadow;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        ComputedBoxShadow {
+            base: self.base.to_computed_value(context),
+            spread: self
+                .spread
+                .as_ref()
+                .unwrap_or(&Length::zero())
+                .to_computed_value(context),
+            inset: self.inset,
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &ComputedBoxShadow) -> Self {
+        BoxShadow {
+            base: ToComputedValue::from_computed_value(&computed.base),
+            spread: Some(ToComputedValue::from_computed_value(&computed.spread)),
+            inset: computed.inset,
+        }
+    }
+}
+
+impl Parse for Filter {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        #[cfg(feature = "gecko")]
+        {
+            if let Ok(url) = input.try_parse(|i| SpecifiedUrl::parse(context, i)) {
+                return Ok(GenericFilter::Url(url));
+            }
+        }
+        let location = input.current_source_location();
+        let function = match input.expect_function() {
+            Ok(f) => f.clone(),
+            Err(cssparser::BasicParseError {
+                kind: BasicParseErrorKind::UnexpectedToken(t),
+                location,
+            }) => return Err(location.new_custom_error(ValueParseErrorKind::InvalidFilter(t))),
+            Err(e) => return Err(e.into()),
+        };
+        input.parse_nested_block(|i| {
+            match_ignore_ascii_case! { &*function,
+                "blur" => Ok(GenericFilter::Blur(
+                    i.try_parse(|i| NonNegativeLength::parse(context, i))
+                     .unwrap_or(Zero::zero()),
+                )),
+                "brightness" => Ok(GenericFilter::Brightness(
+                    i.try_parse(|i| NonNegativeFactor::parse(context, i))
+                     .unwrap_or(NonNegativeFactor::one()),
+                )),
+                "contrast" => Ok(GenericFilter::Contrast(
+                    i.try_parse(|i| NonNegativeFactor::parse(context, i))
+                     .unwrap_or(NonNegativeFactor::one()),
+                )),
+                "grayscale" => {
+                    // Values of amount over 100% are allowed but UAs must clamp the values to 1.
+                    // https://drafts.fxtf.org/filter-effects/#funcdef-filter-grayscale
+                    Ok(GenericFilter::Grayscale(
+                        i.try_parse(|i| ZeroToOneFactor::parse(context, i))
+                         .unwrap_or(ZeroToOneFactor::one()),
+                    ))
+                },
+                "hue-rotate" => {
+                    // We allow unitless zero here, see:
+                    // https://github.com/w3c/fxtf-drafts/issues/228
+                    Ok(GenericFilter::HueRotate(
+                        i.try_parse(|i| Angle::parse_with_unitless(context, i))
+                         .unwrap_or(Zero::zero()),
+                    ))
+                },
+                "invert" => {
+                    // Values of amount over 100% are allowed but UAs must clamp the values to 1.
+                    // https://drafts.fxtf.org/filter-effects/#funcdef-filter-invert
+                    Ok(GenericFilter::Invert(
+                        i.try_parse(|i| ZeroToOneFactor::parse(context, i))
+                         .unwrap_or(ZeroToOneFactor::one()),
+                    ))
+                },
+                "opacity" => {
+                    // Values of amount over 100% are allowed but UAs must clamp the values to 1.
+                    // https://drafts.fxtf.org/filter-effects/#funcdef-filter-opacity
+                    Ok(GenericFilter::Opacity(
+                        i.try_parse(|i| ZeroToOneFactor::parse(context, i))
+                         .unwrap_or(ZeroToOneFactor::one()),
+                    ))
+                },
+                "saturate" => Ok(GenericFilter::Saturate(
+                    i.try_parse(|i| NonNegativeFactor::parse(context, i))
+                     .unwrap_or(NonNegativeFactor::one()),
+                )),
+                "sepia" => {
+                    // Values of amount over 100% are allowed but UAs must clamp the values to 1.
+                    // https://drafts.fxtf.org/filter-effects/#funcdef-filter-sepia
+                    Ok(GenericFilter::Sepia(
+                        i.try_parse(|i| ZeroToOneFactor::parse(context, i))
+                         .unwrap_or(ZeroToOneFactor::one()),
+                    ))
+                },
+                "drop-shadow" => Ok(GenericFilter::DropShadow(Parse::parse(context, i)?)),
+                _ => Err(location.new_custom_error(
+                    ValueParseErrorKind::InvalidFilter(Token::Function(function.clone()))
+                )),
+            }
+        })
+    }
+}
+
+impl Parse for SimpleShadow {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let color = input.try_parse(|i| Color::parse(context, i)).ok();
+        let horizontal = Length::parse(context, input)?;
+        let vertical = Length::parse(context, input)?;
+        let blur = input
+            .try_parse(|i| Length::parse_non_negative(context, i))
+            .ok();
+        let blur = blur.map(NonNegative::<Length>);
+        let color = color.or_else(|| input.try_parse(|i| Color::parse(context, i)).ok());
+
+        Ok(SimpleShadow {
+            color,
+            horizontal,
+            vertical,
+            blur,
+        })
+    }
+}
+
+impl ToComputedValue for SimpleShadow {
+    type ComputedValue = ComputedSimpleShadow;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        ComputedSimpleShadow {
+            color: self
+                .color
+                .as_ref()
+                .unwrap_or(&Color::currentcolor())
+                .to_computed_value(context),
+            horizontal: self.horizontal.to_computed_value(context),
+            vertical: self.vertical.to_computed_value(context),
+            blur: self
+                .blur
+                .as_ref()
+                .unwrap_or(&NonNegativeLength::zero())
+                .to_computed_value(context),
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        SimpleShadow {
+            color: Some(ToComputedValue::from_computed_value(&computed.color)),
+            horizontal: ToComputedValue::from_computed_value(&computed.horizontal),
+            vertical: ToComputedValue::from_computed_value(&computed.vertical),
+            blur: Some(ToComputedValue::from_computed_value(&computed.blur)),
+        }
+    }
+}
diff --git a/servo/components/style/values/specified/flex.rs b/servo/components/style/values/specified/flex.rs
new file mode 100644
index 0000000000..7c767cdf34
--- /dev/null
+++ b/servo/components/style/values/specified/flex.rs
@@ -0,0 +1,25 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS values related to flexbox.
+
+use crate::values::generics::flex::FlexBasis as GenericFlexBasis;
+use crate::values::specified::Size;
+
+/// A specified value for the `flex-basis` property.
+pub type FlexBasis = GenericFlexBasis<Size>;
+
+impl FlexBasis {
+    /// `auto`
+    #[inline]
+    pub fn auto() -> Self {
+        GenericFlexBasis::Size(Size::auto())
+    }
+
+    /// `0%`
+    #[inline]
+    pub fn zero_percent() -> Self {
+        GenericFlexBasis::Size(Size::zero_percent())
+    }
+}
diff --git a/servo/components/style/values/specified/font.rs b/servo/components/style/values/specified/font.rs
new file mode 100644
index 0000000000..5b75778e31
--- /dev/null
+++ b/servo/components/style/values/specified/font.rs
@@ -0,0 +1,2213 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified values for font properties
+
+use crate::context::QuirksMode;
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::font::{FamilyName, FontFamilyList, SingleFontFamily};
+use crate::values::computed::Percentage as ComputedPercentage;
+use crate::values::computed::{font as computed, Length, NonNegativeLength};
+use crate::values::computed::{CSSPixelLength, Context, ToComputedValue};
+use crate::values::generics::font::VariationValue;
+use crate::values::generics::font::{
+    self as generics, FeatureTagValue, FontSettings, FontTag, GenericFontSizeAdjust,
+};
+use crate::values::generics::NonNegative;
+use crate::values::specified::length::{FontBaseSize, PX_PER_PT};
+use crate::values::specified::{AllowQuirks, Angle, Integer, LengthPercentage};
+use crate::values::specified::{NoCalcLength, NonNegativeNumber, NonNegativePercentage, Number};
+use crate::values::{CustomIdent, SelectorParseErrorKind, serialize_atom_identifier};
+use crate::Atom;
+use cssparser::{Parser, Token};
+#[cfg(feature = "gecko")]
+use malloc_size_of::{MallocSizeOf, MallocSizeOfOps, MallocUnconditionalSizeOf};
+use std::fmt::{self, Write};
+use style_traits::values::SequenceWriter;
+use style_traits::{CssWriter, KeywordsCollectFn, ParseError};
+use style_traits::{SpecifiedValueInfo, StyleParseErrorKind, ToCss};
+
+// FIXME(emilio): The system font code is copy-pasta, and should be cleaned up.
+macro_rules! system_font_methods {
+    ($ty:ident, $field:ident) => {
+        system_font_methods!($ty);
+
+        fn compute_system(&self, _context: &Context) -> <$ty as ToComputedValue>::ComputedValue {
+            debug_assert!(matches!(*self, $ty::System(..)));
+            #[cfg(feature = "gecko")]
+            {
+                _context.cached_system_font.as_ref().unwrap().$field.clone()
+            }
+            #[cfg(feature = "servo")]
+            {
+                unreachable!()
+            }
+        }
+    };
+
+    ($ty:ident) => {
+        /// Get a specified value that represents a system font.
+        pub fn system_font(f: SystemFont) -> Self {
+            $ty::System(f)
+        }
+
+        /// Retreive a SystemFont from the specified value.
+        pub fn get_system(&self) -> Option<SystemFont> {
+            if let $ty::System(s) = *self {
+                Some(s)
+            } else {
+                None
+            }
+        }
+    };
+}
+
+/// System fonts.
+#[repr(u8)]
+#[derive(
+    Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum SystemFont {
+    /// https://drafts.csswg.org/css-fonts/#valdef-font-caption
+    Caption,
+    /// https://drafts.csswg.org/css-fonts/#valdef-font-icon
+    Icon,
+    /// https://drafts.csswg.org/css-fonts/#valdef-font-menu
+    Menu,
+    /// https://drafts.csswg.org/css-fonts/#valdef-font-message-box
+    MessageBox,
+    /// https://drafts.csswg.org/css-fonts/#valdef-font-small-caption
+    SmallCaption,
+    /// https://drafts.csswg.org/css-fonts/#valdef-font-status-bar
+    StatusBar,
+    /// Internal system font, used by the `<menupopup>`s on macOS.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozPullDownMenu,
+    /// Internal system font, used for `<button>` elements.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozButton,
+    /// Internal font, used by `<select>` elements.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozList,
+    /// Internal font, used by `<input>` elements.
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozField,
+    #[css(skip)]
+    End, // Just for indexing purposes.
+}
+
+const DEFAULT_SCRIPT_MIN_SIZE_PT: u32 = 8;
+const DEFAULT_SCRIPT_SIZE_MULTIPLIER: f64 = 0.71;
+
+/// The minimum font-weight value per:
+///
+/// https://drafts.csswg.org/css-fonts-4/#font-weight-numeric-values
+pub const MIN_FONT_WEIGHT: f32 = 1.;
+
+/// The maximum font-weight value per:
+///
+/// https://drafts.csswg.org/css-fonts-4/#font-weight-numeric-values
+pub const MAX_FONT_WEIGHT: f32 = 1000.;
+
+/// A specified font-weight value.
+///
+/// https://drafts.csswg.org/css-fonts-4/#propdef-font-weight
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+pub enum FontWeight {
+    /// `<font-weight-absolute>`
+    Absolute(AbsoluteFontWeight),
+    /// Bolder variant
+    Bolder,
+    /// Lighter variant
+    Lighter,
+    /// System font variant.
+    #[css(skip)]
+    System(SystemFont),
+}
+
+impl FontWeight {
+    system_font_methods!(FontWeight, font_weight);
+
+    /// `normal`
+    #[inline]
+    pub fn normal() -> Self {
+        FontWeight::Absolute(AbsoluteFontWeight::Normal)
+    }
+
+    /// Get a specified FontWeight from a gecko keyword
+    pub fn from_gecko_keyword(kw: u32) -> Self {
+        debug_assert!(kw % 100 == 0);
+        debug_assert!(kw as f32 <= MAX_FONT_WEIGHT);
+        FontWeight::Absolute(AbsoluteFontWeight::Weight(Number::new(kw as f32)))
+    }
+}
+
+impl ToComputedValue for FontWeight {
+    type ComputedValue = computed::FontWeight;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            FontWeight::Absolute(ref abs) => abs.compute(),
+            FontWeight::Bolder => context
+                .builder
+                .get_parent_font()
+                .clone_font_weight()
+                .bolder(),
+            FontWeight::Lighter => context
+                .builder
+                .get_parent_font()
+                .clone_font_weight()
+                .lighter(),
+            FontWeight::System(_) => self.compute_system(context),
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &computed::FontWeight) -> Self {
+        FontWeight::Absolute(AbsoluteFontWeight::Weight(Number::from_computed_value(
+            &computed.value(),
+        )))
+    }
+}
+
+/// An absolute font-weight value for a @font-face rule.
+///
+/// https://drafts.csswg.org/css-fonts-4/#font-weight-absolute-values
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum AbsoluteFontWeight {
+    /// A `<number>`, with the additional constraints specified in:
+    ///
+    ///   https://drafts.csswg.org/css-fonts-4/#font-weight-numeric-values
+    Weight(Number),
+    /// Normal font weight. Same as 400.
+    Normal,
+    /// Bold font weight. Same as 700.
+    Bold,
+}
+
+impl AbsoluteFontWeight {
+    /// Returns the computed value for this absolute font weight.
+    pub fn compute(&self) -> computed::FontWeight {
+        match *self {
+            AbsoluteFontWeight::Weight(weight) => computed::FontWeight::from_float(weight.get()),
+            AbsoluteFontWeight::Normal => computed::FontWeight::NORMAL,
+            AbsoluteFontWeight::Bold => computed::FontWeight::BOLD,
+        }
+    }
+}
+
+impl Parse for AbsoluteFontWeight {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(number) = input.try_parse(|input| Number::parse(context, input)) {
+            // We could add another AllowedNumericType value, but it doesn't
+            // seem worth it just for a single property with such a weird range,
+            // so we do the clamping here manually.
+            if !number.was_calc() &&
+                (number.get() < MIN_FONT_WEIGHT || number.get() > MAX_FONT_WEIGHT)
+            {
+                return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+            return Ok(AbsoluteFontWeight::Weight(number));
+        }
+
+        Ok(try_match_ident_ignore_ascii_case! { input,
+            "normal" => AbsoluteFontWeight::Normal,
+            "bold" => AbsoluteFontWeight::Bold,
+        })
+    }
+}
+
+/// The specified value of the `font-style` property, without the system font
+/// crap.
+pub type SpecifiedFontStyle = generics::FontStyle<Angle>;
+
+impl ToCss for SpecifiedFontStyle {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            generics::FontStyle::Normal => dest.write_str("normal"),
+            generics::FontStyle::Italic => dest.write_str("italic"),
+            generics::FontStyle::Oblique(ref angle) => {
+                dest.write_str("oblique")?;
+                if *angle != Self::default_angle() {
+                    dest.write_char(' ')?;
+                    angle.to_css(dest)?;
+                }
+                Ok(())
+            },
+        }
+    }
+}
+
+impl Parse for SpecifiedFontStyle {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(try_match_ident_ignore_ascii_case! { input,
+            "normal" => generics::FontStyle::Normal,
+            "italic" => generics::FontStyle::Italic,
+            "oblique" => {
+                let angle = input.try_parse(|input| Self::parse_angle(context, input))
+                    .unwrap_or_else(|_| Self::default_angle());
+
+                generics::FontStyle::Oblique(angle)
+            },
+        })
+    }
+}
+
+impl ToComputedValue for SpecifiedFontStyle {
+    type ComputedValue = computed::FontStyle;
+
+    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
+        match *self {
+            Self::Normal => computed::FontStyle::NORMAL,
+            Self::Italic => computed::FontStyle::ITALIC,
+            Self::Oblique(ref angle) => computed::FontStyle::oblique(angle.degrees()),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        if *computed == computed::FontStyle::NORMAL {
+            return Self::Normal;
+        }
+        if *computed == computed::FontStyle::ITALIC {
+            return Self::Italic;
+        }
+        let degrees = computed.oblique_degrees();
+        generics::FontStyle::Oblique(Angle::from_degrees(degrees, /* was_calc = */ false))
+    }
+}
+
+/// From https://drafts.csswg.org/css-fonts-4/#valdef-font-style-oblique-angle:
+///
+///     Values less than -90deg or values greater than 90deg are
+///     invalid and are treated as parse errors.
+///
+/// The maximum angle value that `font-style: oblique` should compute to.
+pub const FONT_STYLE_OBLIQUE_MAX_ANGLE_DEGREES: f32 = 90.;
+
+/// The minimum angle value that `font-style: oblique` should compute to.
+pub const FONT_STYLE_OBLIQUE_MIN_ANGLE_DEGREES: f32 = -90.;
+
+impl SpecifiedFontStyle {
+    /// Gets a clamped angle in degrees from a specified Angle.
+    pub fn compute_angle_degrees(angle: &Angle) -> f32 {
+        angle
+            .degrees()
+            .max(FONT_STYLE_OBLIQUE_MIN_ANGLE_DEGREES)
+            .min(FONT_STYLE_OBLIQUE_MAX_ANGLE_DEGREES)
+    }
+
+    /// Parse a suitable angle for font-style: oblique.
+    pub fn parse_angle<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Angle, ParseError<'i>> {
+        let angle = Angle::parse(context, input)?;
+        if angle.was_calc() {
+            return Ok(angle);
+        }
+
+        let degrees = angle.degrees();
+        if degrees < FONT_STYLE_OBLIQUE_MIN_ANGLE_DEGREES ||
+            degrees > FONT_STYLE_OBLIQUE_MAX_ANGLE_DEGREES
+        {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        return Ok(angle);
+    }
+
+    /// The default angle for `font-style: oblique`.
+    pub fn default_angle() -> Angle {
+        Angle::from_degrees(
+            computed::FontStyle::DEFAULT_OBLIQUE_DEGREES as f32,
+            /* was_calc = */ false,
+        )
+    }
+}
+
+/// The specified value of the `font-style` property.
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum FontStyle {
+    Specified(SpecifiedFontStyle),
+    #[css(skip)]
+    System(SystemFont),
+}
+
+impl FontStyle {
+    /// Return the `normal` value.
+    #[inline]
+    pub fn normal() -> Self {
+        FontStyle::Specified(generics::FontStyle::Normal)
+    }
+
+    system_font_methods!(FontStyle, font_style);
+}
+
+impl ToComputedValue for FontStyle {
+    type ComputedValue = computed::FontStyle;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            FontStyle::Specified(ref specified) => specified.to_computed_value(context),
+            FontStyle::System(..) => self.compute_system(context),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        FontStyle::Specified(SpecifiedFontStyle::from_computed_value(computed))
+    }
+}
+
+/// A value for the `font-stretch` property.
+///
+/// https://drafts.csswg.org/css-fonts-4/#font-stretch-prop
+#[allow(missing_docs)]
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+pub enum FontStretch {
+    Stretch(NonNegativePercentage),
+    Keyword(FontStretchKeyword),
+    #[css(skip)]
+    System(SystemFont),
+}
+
+/// A keyword value for `font-stretch`.
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum FontStretchKeyword {
+    Normal,
+    Condensed,
+    UltraCondensed,
+    ExtraCondensed,
+    SemiCondensed,
+    SemiExpanded,
+    Expanded,
+    ExtraExpanded,
+    UltraExpanded,
+}
+
+impl FontStretchKeyword {
+    /// Turns the keyword into a computed value.
+    pub fn compute(&self) -> computed::FontStretch {
+        computed::FontStretch::from_keyword(*self)
+    }
+
+    /// Does the opposite operation to `compute`, in order to serialize keywords
+    /// if possible.
+    pub fn from_percentage(p: f32) -> Option<Self> {
+        computed::FontStretch::from_percentage(p).as_keyword()
+    }
+}
+
+impl FontStretch {
+    /// `normal`.
+    pub fn normal() -> Self {
+        FontStretch::Keyword(FontStretchKeyword::Normal)
+    }
+
+    system_font_methods!(FontStretch, font_stretch);
+}
+
+impl ToComputedValue for FontStretch {
+    type ComputedValue = computed::FontStretch;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            FontStretch::Stretch(ref percentage) => {
+                let percentage = percentage.to_computed_value(context).0;
+                computed::FontStretch::from_percentage(percentage.0)
+            },
+            FontStretch::Keyword(ref kw) => kw.compute(),
+            FontStretch::System(_) => self.compute_system(context),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        FontStretch::Stretch(NonNegativePercentage::from_computed_value(&NonNegative(
+            computed.to_percentage(),
+        )))
+    }
+}
+
+/// CSS font keywords
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+    Serialize,
+    Deserialize,
+)]
+#[allow(missing_docs)]
+#[repr(u8)]
+pub enum FontSizeKeyword {
+    #[css(keyword = "xx-small")]
+    XXSmall,
+    XSmall,
+    Small,
+    Medium,
+    Large,
+    XLarge,
+    #[css(keyword = "xx-large")]
+    XXLarge,
+    #[css(keyword = "xxx-large")]
+    XXXLarge,
+    #[css(skip)]
+    None,
+}
+
+impl FontSizeKeyword {
+    /// Convert to an HTML <font size> value
+    #[inline]
+    pub fn html_size(self) -> u8 {
+        self as u8
+    }
+}
+
+impl Default for FontSizeKeyword {
+    fn default() -> Self {
+        FontSizeKeyword::Medium
+    }
+}
+
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    ToAnimatedValue,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[cfg_attr(feature = "servo", derive(Serialize, Deserialize))]
+/// Additional information for keyword-derived font sizes.
+pub struct KeywordInfo {
+    /// The keyword used
+    pub kw: FontSizeKeyword,
+    /// A factor to be multiplied by the computed size of the keyword
+    #[css(skip)]
+    pub factor: f32,
+    /// An additional fixed offset to add to the kw * factor in the case of
+    /// `calc()`.
+    #[css(skip)]
+    pub offset: CSSPixelLength,
+}
+
+impl KeywordInfo {
+    /// KeywordInfo value for font-size: medium
+    pub fn medium() -> Self {
+        Self::new(FontSizeKeyword::Medium)
+    }
+
+    /// KeywordInfo value for font-size: none
+    pub fn none() -> Self {
+        Self::new(FontSizeKeyword::None)
+    }
+
+    fn new(kw: FontSizeKeyword) -> Self {
+        KeywordInfo {
+            kw,
+            factor: 1.,
+            offset: CSSPixelLength::new(0.),
+        }
+    }
+
+    /// Computes the final size for this font-size keyword, accounting for
+    /// text-zoom.
+    fn to_computed_value(&self, context: &Context) -> CSSPixelLength {
+        debug_assert_ne!(self.kw, FontSizeKeyword::None);
+        let base = context.maybe_zoom_text(self.kw.to_length(context).0);
+        base * self.factor + context.maybe_zoom_text(self.offset)
+    }
+
+    /// Given a parent keyword info (self), apply an additional factor/offset to
+    /// it.
+    fn compose(self, factor: f32) -> Self {
+        if self.kw == FontSizeKeyword::None {
+            return self;
+        }
+        KeywordInfo {
+            kw: self.kw,
+            factor: self.factor * factor,
+            offset: self.offset * factor,
+        }
+    }
+}
+
+impl SpecifiedValueInfo for KeywordInfo {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        <FontSizeKeyword as SpecifiedValueInfo>::collect_completion_keywords(f);
+    }
+}
+
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+/// A specified font-size value
+pub enum FontSize {
+    /// A length; e.g. 10px.
+    Length(LengthPercentage),
+    /// A keyword value, along with a ratio and absolute offset.
+    /// The ratio in any specified keyword value
+    /// will be 1 (with offset 0), but we cascade keywordness even
+    /// after font-relative (percent and em) values
+    /// have been applied, which is where the ratio
+    /// comes in. The offset comes in if we cascaded a calc value,
+    /// where the font-relative portion (em and percentage) will
+    /// go into the ratio, and the remaining units all computed together
+    /// will go into the offset.
+    /// See bug 1355707.
+    Keyword(KeywordInfo),
+    /// font-size: smaller
+    Smaller,
+    /// font-size: larger
+    Larger,
+    /// Derived from a specified system font.
+    #[css(skip)]
+    System(SystemFont),
+}
+
+/// Specifies a prioritized list of font family names or generic family names.
+#[derive(Clone, Debug, Eq, PartialEq, ToCss, ToShmem)]
+#[cfg_attr(feature = "servo", derive(Hash))]
+pub enum FontFamily {
+    /// List of `font-family`
+    #[css(comma)]
+    Values(#[css(iterable)] FontFamilyList),
+    /// System font
+    #[css(skip)]
+    System(SystemFont),
+}
+
+impl FontFamily {
+    system_font_methods!(FontFamily, font_family);
+}
+
+impl ToComputedValue for FontFamily {
+    type ComputedValue = computed::FontFamily;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            FontFamily::Values(ref list) => computed::FontFamily {
+                families: list.clone(),
+                is_system_font: false,
+                is_initial: false,
+            },
+            FontFamily::System(_) => self.compute_system(context),
+        }
+    }
+
+    fn from_computed_value(other: &computed::FontFamily) -> Self {
+        FontFamily::Values(other.families.clone())
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl MallocSizeOf for FontFamily {
+    fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
+        match *self {
+            FontFamily::Values(ref v) => {
+                // Although the family list is refcounted, we always attribute
+                // its size to the specified value.
+                v.list.unconditional_size_of(ops)
+            },
+            FontFamily::System(_) => 0,
+        }
+    }
+}
+
+impl Parse for FontFamily {
+    /// <family-name>#
+    /// <family-name> = <string> | [ <ident>+ ]
+    /// TODO: <generic-family>
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<FontFamily, ParseError<'i>> {
+        let values =
+            input.parse_comma_separated(|input| SingleFontFamily::parse(context, input))?;
+        Ok(FontFamily::Values(FontFamilyList {
+            list: crate::ArcSlice::from_iter(values.into_iter()),
+        }))
+    }
+}
+
+impl SpecifiedValueInfo for FontFamily {}
+
+/// `FamilyName::parse` is based on `SingleFontFamily::parse` and not the other
+/// way around because we want the former to exclude generic family keywords.
+impl Parse for FamilyName {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        match SingleFontFamily::parse(context, input) {
+            Ok(SingleFontFamily::FamilyName(name)) => Ok(name),
+            Ok(SingleFontFamily::Generic(_)) => {
+                Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+            },
+            Err(e) => Err(e),
+        }
+    }
+}
+
+/// Preserve the readability of text when font fallback occurs
+pub type FontSizeAdjust = GenericFontSizeAdjust<NonNegativeNumber>;
+
+impl Parse for FontSizeAdjust {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        if let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            let basis_enabled = static_prefs::pref!("layout.css.font-size-adjust.basis.enabled");
+            let basis = match_ignore_ascii_case! { &ident,
+                "none" => return Ok(Self::None),
+                // Check for size adjustment basis keywords if enabled.
+                "ex-height" if basis_enabled => Self::ExHeight,
+                "cap-height" if basis_enabled => Self::CapHeight,
+                "ch-width" if basis_enabled => Self::ChWidth,
+                "ic-width" if basis_enabled => Self::IcWidth,
+                "ic-height" if basis_enabled => Self::IcHeight,
+                // Unknown (or disabled) keyword.
+                _ => return Err(location.new_custom_error(
+                    SelectorParseErrorKind::UnexpectedIdent(ident)
+                )),
+            };
+            let value = NonNegativeNumber::parse(context, input)?;
+            return Ok(basis(value));
+        }
+        // Without a basis keyword, the number refers to the 'ex-height' metric.
+        let value = NonNegativeNumber::parse(context, input)?;
+        Ok(Self::ExHeight(value))
+    }
+}
+
+/// This is the ratio applied for font-size: larger
+/// and smaller by both Firefox and Chrome
+const LARGER_FONT_SIZE_RATIO: f32 = 1.2;
+
+/// The default font size.
+pub const FONT_MEDIUM_PX: f32 = 16.0;
+
+impl FontSizeKeyword {
+    #[inline]
+    #[cfg(feature = "servo")]
+    fn to_length(&self, _: &Context) -> NonNegativeLength {
+        let medium = Length::new(FONT_MEDIUM_PX);
+        // https://drafts.csswg.org/css-fonts-3/#font-size-prop
+        NonNegative(match *self {
+            FontSizeKeyword::XXSmall => medium * 3.0 / 5.0,
+            FontSizeKeyword::XSmall => medium * 3.0 / 4.0,
+            FontSizeKeyword::Small => medium * 8.0 / 9.0,
+            FontSizeKeyword::Medium => medium,
+            FontSizeKeyword::Large => medium * 6.0 / 5.0,
+            FontSizeKeyword::XLarge => medium * 3.0 / 2.0,
+            FontSizeKeyword::XXLarge => medium * 2.0,
+            FontSizeKeyword::XXXLarge => medium * 3.0,
+            FontSizeKeyword::None => unreachable!(),
+        })
+    }
+
+    #[cfg(feature = "gecko")]
+    #[inline]
+    fn to_length(&self, cx: &Context) -> NonNegativeLength {
+        let gecko_font = cx.style().get_font().gecko();
+        let family = &gecko_font.mFont.family.families;
+        let generic = family
+            .single_generic()
+            .unwrap_or(computed::GenericFontFamily::None);
+        let base_size = unsafe {
+            Atom::with(gecko_font.mLanguage.mRawPtr, |language| {
+                cx.device().base_size_for_generic(language, generic)
+            })
+        };
+        self.to_length_without_context(cx.quirks_mode, base_size)
+    }
+
+    /// Resolve a keyword length without any context, with explicit arguments.
+    #[cfg(feature = "gecko")]
+    #[inline]
+    pub fn to_length_without_context(
+        &self,
+        quirks_mode: QuirksMode,
+        base_size: Length,
+    ) -> NonNegativeLength {
+        // The tables in this function are originally from
+        // nsRuleNode::CalcFontPointSize in Gecko:
+        //
+        // https://searchfox.org/mozilla-central/rev/c05d9d61188d32b8/layout/style/nsRuleNode.cpp#3150
+        //
+        // Mapping from base size and HTML size to pixels
+        // The first index is (base_size - 9), the second is the
+        // HTML size. "0" is CSS keyword xx-small, not HTML size 0,
+        // since HTML size 0 is the same as 1.
+        //
+        //  xxs   xs      s      m     l      xl     xxl   -
+        //  -     0/1     2      3     4      5      6     7
+        static FONT_SIZE_MAPPING: [[i32; 8]; 8] = [
+            [9, 9, 9, 9, 11, 14, 18, 27],
+            [9, 9, 9, 10, 12, 15, 20, 30],
+            [9, 9, 10, 11, 13, 17, 22, 33],
+            [9, 9, 10, 12, 14, 18, 24, 36],
+            [9, 10, 12, 13, 16, 20, 26, 39],
+            [9, 10, 12, 14, 17, 21, 28, 42],
+            [9, 10, 13, 15, 18, 23, 30, 45],
+            [9, 10, 13, 16, 18, 24, 32, 48],
+        ];
+
+        // This table gives us compatibility with WinNav4 for the default fonts only.
+        // In WinNav4, the default fonts were:
+        //
+        //     Times/12pt ==   Times/16px at 96ppi
+        //   Courier/10pt == Courier/13px at 96ppi
+        //
+        // xxs   xs     s      m      l     xl     xxl    -
+        // -     1      2      3      4     5      6      7
+        static QUIRKS_FONT_SIZE_MAPPING: [[i32; 8]; 8] = [
+            [9, 9, 9, 9, 11, 14, 18, 28],
+            [9, 9, 9, 10, 12, 15, 20, 31],
+            [9, 9, 9, 11, 13, 17, 22, 34],
+            [9, 9, 10, 12, 14, 18, 24, 37],
+            [9, 9, 10, 13, 16, 20, 26, 40],
+            [9, 9, 11, 14, 17, 21, 28, 42],
+            [9, 10, 12, 15, 17, 23, 30, 45],
+            [9, 10, 13, 16, 18, 24, 32, 48],
+        ];
+
+        static FONT_SIZE_FACTORS: [i32; 8] = [60, 75, 89, 100, 120, 150, 200, 300];
+        let base_size_px = base_size.px().round() as i32;
+        let html_size = self.html_size() as usize;
+        NonNegative(if base_size_px >= 9 && base_size_px <= 16 {
+            let mapping = if quirks_mode == QuirksMode::Quirks {
+                QUIRKS_FONT_SIZE_MAPPING
+            } else {
+                FONT_SIZE_MAPPING
+            };
+            Length::new(mapping[(base_size_px - 9) as usize][html_size] as f32)
+        } else {
+            base_size * FONT_SIZE_FACTORS[html_size] as f32 / 100.0
+        })
+    }
+}
+
+impl FontSize {
+    /// <https://html.spec.whatwg.org/multipage/#rules-for-parsing-a-legacy-font-size>
+    pub fn from_html_size(size: u8) -> Self {
+        FontSize::Keyword(KeywordInfo::new(match size {
+            // If value is less than 1, let it be 1.
+            0 | 1 => FontSizeKeyword::XSmall,
+            2 => FontSizeKeyword::Small,
+            3 => FontSizeKeyword::Medium,
+            4 => FontSizeKeyword::Large,
+            5 => FontSizeKeyword::XLarge,
+            6 => FontSizeKeyword::XXLarge,
+            // If value is greater than 7, let it be 7.
+            _ => FontSizeKeyword::XXXLarge,
+        }))
+    }
+
+    /// Compute it against a given base font size
+    pub fn to_computed_value_against(
+        &self,
+        context: &Context,
+        base_size: FontBaseSize,
+    ) -> computed::FontSize {
+        use crate::values::specified::length::FontRelativeLength;
+
+        let compose_keyword = |factor| {
+            context
+                .style()
+                .get_parent_font()
+                .clone_font_size()
+                .keyword_info
+                .compose(factor)
+        };
+        let mut info = KeywordInfo::none();
+        let size = match *self {
+            FontSize::Length(LengthPercentage::Length(ref l)) => {
+                if let NoCalcLength::FontRelative(ref value) = *l {
+                    if let FontRelativeLength::Em(em) = *value {
+                        // If the parent font was keyword-derived, this is
+                        // too. Tack the em unit onto the factor
+                        info = compose_keyword(em);
+                    }
+                }
+                let result = l.to_computed_value_with_base_size(context, base_size);
+                if l.should_zoom_text() {
+                    context.maybe_zoom_text(result)
+                } else {
+                    result
+                }
+            },
+            FontSize::Length(LengthPercentage::Percentage(pc)) => {
+                // If the parent font was keyword-derived, this is too.
+                // Tack the % onto the factor
+                info = compose_keyword(pc.0);
+                (base_size.resolve(context).computed_size() * pc.0).normalized()
+            },
+            FontSize::Length(LengthPercentage::Calc(ref calc)) => {
+                let calc = calc.to_computed_value_zoomed(context, base_size);
+                calc.resolve(base_size.resolve(context).computed_size())
+            },
+            FontSize::Keyword(i) => {
+                // As a specified keyword, this is keyword derived
+                info = i;
+                i.to_computed_value(context).clamp_to_non_negative()
+            },
+            FontSize::Smaller => {
+                info = compose_keyword(1. / LARGER_FONT_SIZE_RATIO);
+                FontRelativeLength::Em(1. / LARGER_FONT_SIZE_RATIO)
+                    .to_computed_value(context, base_size)
+            },
+            FontSize::Larger => {
+                info = compose_keyword(LARGER_FONT_SIZE_RATIO);
+                FontRelativeLength::Em(LARGER_FONT_SIZE_RATIO).to_computed_value(context, base_size)
+            },
+
+            FontSize::System(_) => {
+                #[cfg(feature = "servo")]
+                {
+                    unreachable!()
+                }
+                #[cfg(feature = "gecko")]
+                {
+                    context
+                        .cached_system_font
+                        .as_ref()
+                        .unwrap()
+                        .font_size
+                        .computed_size()
+                }
+            },
+        };
+        computed::FontSize {
+            computed_size: NonNegative(size),
+            used_size: NonNegative(size),
+            keyword_info: info,
+        }
+    }
+}
+
+impl ToComputedValue for FontSize {
+    type ComputedValue = computed::FontSize;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> computed::FontSize {
+        self.to_computed_value_against(context, FontBaseSize::InheritedStyle)
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &computed::FontSize) -> Self {
+        FontSize::Length(LengthPercentage::Length(
+            ToComputedValue::from_computed_value(&computed.computed_size()),
+        ))
+    }
+}
+
+impl FontSize {
+    system_font_methods!(FontSize);
+
+    /// Get initial value for specified font size.
+    #[inline]
+    pub fn medium() -> Self {
+        FontSize::Keyword(KeywordInfo::medium())
+    }
+
+    /// Parses a font-size, with quirks.
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<FontSize, ParseError<'i>> {
+        if let Ok(lp) = input
+            .try_parse(|i| LengthPercentage::parse_non_negative_quirky(context, i, allow_quirks))
+        {
+            return Ok(FontSize::Length(lp));
+        }
+
+        if let Ok(kw) = input.try_parse(FontSizeKeyword::parse) {
+            return Ok(FontSize::Keyword(KeywordInfo::new(kw)));
+        }
+
+        try_match_ident_ignore_ascii_case! { input,
+            "smaller" => Ok(FontSize::Smaller),
+            "larger" => Ok(FontSize::Larger),
+        }
+    }
+}
+
+impl Parse for FontSize {
+    /// <length> | <percentage> | <absolute-size> | <relative-size>
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<FontSize, ParseError<'i>> {
+        FontSize::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+bitflags! {
+    #[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+    /// Flags of variant alternates in bit
+    struct VariantAlternatesParsingFlags: u8 {
+        /// None of variant alternates enabled
+        const NORMAL = 0;
+        /// Historical forms
+        const HISTORICAL_FORMS = 0x01;
+        /// Stylistic Alternates
+        const STYLISTIC = 0x02;
+        /// Stylistic Sets
+        const STYLESET = 0x04;
+        /// Character Variant
+        const CHARACTER_VARIANT = 0x08;
+        /// Swash glyphs
+        const SWASH = 0x10;
+        /// Ornaments glyphs
+        const ORNAMENTS = 0x20;
+        /// Annotation forms
+        const ANNOTATION = 0x40;
+    }
+}
+
+#[derive(
+    Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[repr(C, u8)]
+/// Set of variant alternates
+pub enum VariantAlternates {
+    /// Enables display of stylistic alternates
+    #[css(function)]
+    Stylistic(CustomIdent),
+    /// Enables display with stylistic sets
+    #[css(comma, function)]
+    Styleset(#[css(iterable)] crate::OwnedSlice<CustomIdent>),
+    /// Enables display of specific character variants
+    #[css(comma, function)]
+    CharacterVariant(#[css(iterable)] crate::OwnedSlice<CustomIdent>),
+    /// Enables display of swash glyphs
+    #[css(function)]
+    Swash(CustomIdent),
+    /// Enables replacement of default glyphs with ornaments
+    #[css(function)]
+    Ornaments(CustomIdent),
+    /// Enables display of alternate annotation forms
+    #[css(function)]
+    Annotation(CustomIdent),
+    /// Enables display of historical forms
+    HistoricalForms,
+}
+
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+/// List of Variant Alternates
+pub struct FontVariantAlternates(
+    #[css(if_empty = "normal", iterable)] crate::OwnedSlice<VariantAlternates>,
+);
+
+impl FontVariantAlternates {
+    /// Returns the length of all variant alternates.
+    pub fn len(&self) -> usize {
+        self.0.iter().fold(0, |acc, alternate| match *alternate {
+            VariantAlternates::Swash(_) |
+            VariantAlternates::Stylistic(_) |
+            VariantAlternates::Ornaments(_) |
+            VariantAlternates::Annotation(_) => acc + 1,
+            VariantAlternates::Styleset(ref slice) |
+            VariantAlternates::CharacterVariant(ref slice) => acc + slice.len(),
+            _ => acc,
+        })
+    }
+}
+
+impl FontVariantAlternates {
+    #[inline]
+    /// Get initial specified value with VariantAlternatesList
+    pub fn get_initial_specified_value() -> Self {
+        Default::default()
+    }
+}
+
+impl Parse for FontVariantAlternates {
+    /// normal |
+    ///  [ stylistic(<feature-value-name>)           ||
+    ///    historical-forms                          ||
+    ///    styleset(<feature-value-name> #)          ||
+    ///    character-variant(<feature-value-name> #) ||
+    ///    swash(<feature-value-name>)               ||
+    ///    ornaments(<feature-value-name>)           ||
+    ///    annotation(<feature-value-name>) ]
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<FontVariantAlternates, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(Default::default());
+        }
+
+        let mut alternates = Vec::new();
+        let mut parsed_alternates = VariantAlternatesParsingFlags::empty();
+        macro_rules! check_if_parsed(
+            ($input:expr, $flag:path) => (
+                if parsed_alternates.contains($flag) {
+                    return Err($input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+                }
+                parsed_alternates |= $flag;
+            )
+        );
+        while let Ok(_) = input.try_parse(|input| match *input.next()? {
+            Token::Ident(ref value) if value.eq_ignore_ascii_case("historical-forms") => {
+                check_if_parsed!(input, VariantAlternatesParsingFlags::HISTORICAL_FORMS);
+                alternates.push(VariantAlternates::HistoricalForms);
+                Ok(())
+            },
+            Token::Function(ref name) => {
+                let name = name.clone();
+                input.parse_nested_block(|i| {
+                    match_ignore_ascii_case! { &name,
+                        "swash" => {
+                            check_if_parsed!(i, VariantAlternatesParsingFlags::SWASH);
+                            let location = i.current_source_location();
+                            let ident = CustomIdent::from_ident(location, i.expect_ident()?, &[])?;
+                            alternates.push(VariantAlternates::Swash(ident));
+                            Ok(())
+                        },
+                        "stylistic" => {
+                            check_if_parsed!(i, VariantAlternatesParsingFlags::STYLISTIC);
+                            let location = i.current_source_location();
+                            let ident = CustomIdent::from_ident(location, i.expect_ident()?, &[])?;
+                            alternates.push(VariantAlternates::Stylistic(ident));
+                            Ok(())
+                        },
+                        "ornaments" => {
+                            check_if_parsed!(i, VariantAlternatesParsingFlags::ORNAMENTS);
+                            let location = i.current_source_location();
+                            let ident = CustomIdent::from_ident(location, i.expect_ident()?, &[])?;
+                            alternates.push(VariantAlternates::Ornaments(ident));
+                            Ok(())
+                        },
+                        "annotation" => {
+                            check_if_parsed!(i, VariantAlternatesParsingFlags::ANNOTATION);
+                            let location = i.current_source_location();
+                            let ident = CustomIdent::from_ident(location, i.expect_ident()?, &[])?;
+                            alternates.push(VariantAlternates::Annotation(ident));
+                            Ok(())
+                        },
+                        "styleset" => {
+                            check_if_parsed!(i, VariantAlternatesParsingFlags::STYLESET);
+                            let idents = i.parse_comma_separated(|i| {
+                                let location = i.current_source_location();
+                                CustomIdent::from_ident(location, i.expect_ident()?, &[])
+                            })?;
+                            alternates.push(VariantAlternates::Styleset(idents.into()));
+                            Ok(())
+                        },
+                        "character-variant" => {
+                            check_if_parsed!(i, VariantAlternatesParsingFlags::CHARACTER_VARIANT);
+                            let idents = i.parse_comma_separated(|i| {
+                                let location = i.current_source_location();
+                                CustomIdent::from_ident(location, i.expect_ident()?, &[])
+                            })?;
+                            alternates.push(VariantAlternates::CharacterVariant(idents.into()));
+                            Ok(())
+                        },
+                        _ => return Err(i.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+                    }
+                })
+            },
+            _ => Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+        }) {}
+
+        if parsed_alternates.is_empty() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        Ok(FontVariantAlternates(alternates.into()))
+    }
+}
+
+macro_rules! impl_variant_east_asian {
+    {
+        $(
+            $(#[$($meta:tt)+])*
+            $ident:ident / $css:expr => $gecko:ident = $value:expr,
+        )+
+    } => {
+        bitflags! {
+            #[derive(MallocSizeOf, ToComputedValue, ToResolvedValue, ToShmem)]
+            /// Vairants for east asian variant
+            pub struct FontVariantEastAsian: u16 {
+                /// None of the features
+                const NORMAL = 0;
+                $(
+                    $(#[$($meta)+])*
+                    const $ident = $value;
+                )+
+            }
+        }
+
+        impl ToCss for FontVariantEastAsian {
+            fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+            where
+                W: Write,
+            {
+                if self.is_empty() {
+                    return dest.write_str("normal");
+                }
+
+                let mut writer = SequenceWriter::new(dest, " ");
+                $(
+                    if self.intersects(Self::$ident) {
+                        writer.raw_item($css)?;
+                    }
+                )+
+                Ok(())
+            }
+        }
+
+        /// Asserts that all variant-east-asian matches its NS_FONT_VARIANT_EAST_ASIAN_* value.
+        #[cfg(feature = "gecko")]
+        #[inline]
+        pub fn assert_variant_east_asian_matches() {
+            use crate::gecko_bindings::structs;
+            $(
+                debug_assert_eq!(structs::$gecko as u16, FontVariantEastAsian::$ident.bits());
+            )+
+        }
+
+        impl SpecifiedValueInfo for FontVariantEastAsian {
+            fn collect_completion_keywords(f: KeywordsCollectFn) {
+                f(&["normal", $($css,)+]);
+            }
+        }
+    }
+}
+
+impl_variant_east_asian! {
+    /// Enables rendering of JIS78 forms (OpenType feature: jp78)
+    JIS78 / "jis78" => NS_FONT_VARIANT_EAST_ASIAN_JIS78 = 0x01,
+    /// Enables rendering of JIS83 forms (OpenType feature: jp83).
+    JIS83 / "jis83" => NS_FONT_VARIANT_EAST_ASIAN_JIS83 = 0x02,
+    /// Enables rendering of JIS90 forms (OpenType feature: jp90).
+    JIS90 / "jis90" => NS_FONT_VARIANT_EAST_ASIAN_JIS90 = 0x04,
+    /// Enables rendering of JIS2004 forms (OpenType feature: jp04).
+    JIS04 / "jis04" => NS_FONT_VARIANT_EAST_ASIAN_JIS04 = 0x08,
+    /// Enables rendering of simplified forms (OpenType feature: smpl).
+    SIMPLIFIED / "simplified" => NS_FONT_VARIANT_EAST_ASIAN_SIMPLIFIED = 0x10,
+    /// Enables rendering of traditional forms (OpenType feature: trad).
+    TRADITIONAL / "traditional" => NS_FONT_VARIANT_EAST_ASIAN_TRADITIONAL = 0x20,
+    /// Enables rendering of full-width variants (OpenType feature: fwid).
+    FULL_WIDTH / "full-width" => NS_FONT_VARIANT_EAST_ASIAN_FULL_WIDTH = 0x40,
+    /// Enables rendering of proportionally-spaced variants (OpenType feature: pwid).
+    PROPORTIONAL_WIDTH / "proportional-width" => NS_FONT_VARIANT_EAST_ASIAN_PROP_WIDTH = 0x80,
+    /// Enables display of ruby variant glyphs (OpenType feature: ruby).
+    RUBY / "ruby" => NS_FONT_VARIANT_EAST_ASIAN_RUBY = 0x100,
+}
+
+#[cfg(feature = "gecko")]
+impl FontVariantEastAsian {
+    /// Obtain a specified value from a Gecko keyword value
+    ///
+    /// Intended for use with presentation attributes, not style structs
+    pub fn from_gecko_keyword(kw: u16) -> Self {
+        Self::from_bits_truncate(kw)
+    }
+
+    /// Transform into gecko keyword
+    pub fn to_gecko_keyword(self) -> u16 {
+        self.bits()
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl_gecko_keyword_conversions!(FontVariantEastAsian, u16);
+
+impl Parse for FontVariantEastAsian {
+    /// normal | [ <east-asian-variant-values> || <east-asian-width-values> || ruby ]
+    /// <east-asian-variant-values> = [ jis78 | jis83 | jis90 | jis04 | simplified | traditional ]
+    /// <east-asian-width-values>   = [ full-width | proportional-width ]
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut result = Self::empty();
+
+        if input
+            .try_parse(|input| input.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(result);
+        }
+
+        while let Ok(flag) = input.try_parse(|input| {
+            Ok(
+                match_ignore_ascii_case! { &input.expect_ident().map_err(|_| ())?,
+                    "jis78" =>
+                        exclusive_value!((result, Self::JIS78 | Self::JIS83 |
+                                                  Self::JIS90 | Self::JIS04 |
+                                                  Self::SIMPLIFIED | Self::TRADITIONAL
+                                        ) => Self::JIS78),
+                    "jis83" =>
+                        exclusive_value!((result, Self::JIS78 | Self::JIS83 |
+                                                  Self::JIS90 | Self::JIS04 |
+                                                  Self::SIMPLIFIED | Self::TRADITIONAL
+                                        ) => Self::JIS83),
+                    "jis90" =>
+                        exclusive_value!((result, Self::JIS78 | Self::JIS83 |
+                                                  Self::JIS90 | Self::JIS04 |
+                                                  Self::SIMPLIFIED | Self::TRADITIONAL
+                                        ) => Self::JIS90),
+                    "jis04" =>
+                        exclusive_value!((result, Self::JIS78 | Self::JIS83 |
+                                                  Self::JIS90 | Self::JIS04 |
+                                                  Self::SIMPLIFIED | Self::TRADITIONAL
+                                        ) => Self::JIS04),
+                    "simplified" =>
+                        exclusive_value!((result, Self::JIS78 | Self::JIS83 |
+                                                  Self::JIS90 | Self::JIS04 |
+                                                  Self::SIMPLIFIED | Self::TRADITIONAL
+                                        ) => Self::SIMPLIFIED),
+                    "traditional" =>
+                        exclusive_value!((result, Self::JIS78 | Self::JIS83 |
+                                                  Self::JIS90 | Self::JIS04 |
+                                                  Self::SIMPLIFIED | Self::TRADITIONAL
+                                        ) => Self::TRADITIONAL),
+                    "full-width" =>
+                        exclusive_value!((result, Self::FULL_WIDTH |
+                                                  Self::PROPORTIONAL_WIDTH
+                                        ) => Self::FULL_WIDTH),
+                    "proportional-width" =>
+                        exclusive_value!((result, Self::FULL_WIDTH |
+                                                  Self::PROPORTIONAL_WIDTH
+                                        ) => Self::PROPORTIONAL_WIDTH),
+                    "ruby" =>
+                        exclusive_value!((result, Self::RUBY) => Self::RUBY),
+                    _ => return Err(()),
+                },
+            )
+        }) {
+            result.insert(flag);
+        }
+
+        if !result.is_empty() {
+            Ok(result)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+macro_rules! impl_variant_ligatures {
+    {
+        $(
+            $(#[$($meta:tt)+])*
+            $ident:ident / $css:expr => $gecko:ident = $value:expr,
+        )+
+    } => {
+        bitflags! {
+            #[derive(MallocSizeOf, ToComputedValue, ToResolvedValue, ToShmem)]
+            /// Variants of ligatures
+            pub struct FontVariantLigatures: u16 {
+                /// Specifies that common default features are enabled
+                const NORMAL = 0;
+                $(
+                    $(#[$($meta)+])*
+                    const $ident = $value;
+                )+
+            }
+        }
+
+        impl ToCss for FontVariantLigatures {
+            fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+            where
+                W: Write,
+            {
+                if self.is_empty() {
+                    return dest.write_str("normal");
+                }
+                if self.contains(FontVariantLigatures::NONE) {
+                    return dest.write_str("none");
+                }
+
+                let mut writer = SequenceWriter::new(dest, " ");
+                $(
+                    if self.intersects(FontVariantLigatures::$ident) {
+                        writer.raw_item($css)?;
+                    }
+                )+
+                Ok(())
+            }
+        }
+
+        /// Asserts that all variant-east-asian matches its NS_FONT_VARIANT_EAST_ASIAN_* value.
+        #[cfg(feature = "gecko")]
+        #[inline]
+        pub fn assert_variant_ligatures_matches() {
+            use crate::gecko_bindings::structs;
+            $(
+                debug_assert_eq!(structs::$gecko as u16, FontVariantLigatures::$ident.bits());
+            )+
+        }
+
+        impl SpecifiedValueInfo for FontVariantLigatures {
+            fn collect_completion_keywords(f: KeywordsCollectFn) {
+                f(&["normal", $($css,)+]);
+            }
+        }
+    }
+}
+
+impl_variant_ligatures! {
+    /// Specifies that all types of ligatures and contextual forms
+    /// covered by this property are explicitly disabled
+    NONE / "none" => NS_FONT_VARIANT_LIGATURES_NONE = 0x01,
+    /// Enables display of common ligatures
+    COMMON_LIGATURES / "common-ligatures" => NS_FONT_VARIANT_LIGATURES_COMMON = 0x02,
+    /// Disables display of common ligatures
+    NO_COMMON_LIGATURES / "no-common-ligatures" => NS_FONT_VARIANT_LIGATURES_NO_COMMON = 0x04,
+    /// Enables display of discretionary ligatures
+    DISCRETIONARY_LIGATURES / "discretionary-ligatures" => NS_FONT_VARIANT_LIGATURES_DISCRETIONARY = 0x08,
+    /// Disables display of discretionary ligatures
+    NO_DISCRETIONARY_LIGATURES / "no-discretionary-ligatures" => NS_FONT_VARIANT_LIGATURES_NO_DISCRETIONARY = 0x10,
+    /// Enables display of historical ligatures
+    HISTORICAL_LIGATURES / "historical-ligatures" => NS_FONT_VARIANT_LIGATURES_HISTORICAL = 0x20,
+    /// Disables display of historical ligatures
+    NO_HISTORICAL_LIGATURES / "no-historical-ligatures" => NS_FONT_VARIANT_LIGATURES_NO_HISTORICAL = 0x40,
+    /// Enables display of contextual alternates
+    CONTEXTUAL / "contextual" => NS_FONT_VARIANT_LIGATURES_CONTEXTUAL = 0x80,
+    /// Disables display of contextual alternates
+    NO_CONTEXTUAL / "no-contextual" => NS_FONT_VARIANT_LIGATURES_NO_CONTEXTUAL = 0x100,
+}
+
+#[cfg(feature = "gecko")]
+impl FontVariantLigatures {
+    /// Obtain a specified value from a Gecko keyword value
+    ///
+    /// Intended for use with presentation attributes, not style structs
+    pub fn from_gecko_keyword(kw: u16) -> Self {
+        Self::from_bits_truncate(kw)
+    }
+
+    /// Transform into gecko keyword
+    pub fn to_gecko_keyword(self) -> u16 {
+        self.bits()
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl_gecko_keyword_conversions!(FontVariantLigatures, u16);
+
+impl Parse for FontVariantLigatures {
+    /// normal | none |
+    /// [ <common-lig-values> ||
+    ///   <discretionary-lig-values> ||
+    ///   <historical-lig-values> ||
+    ///   <contextual-alt-values> ]
+    /// <common-lig-values>        = [ common-ligatures | no-common-ligatures ]
+    /// <discretionary-lig-values> = [ discretionary-ligatures | no-discretionary-ligatures ]
+    /// <historical-lig-values>    = [ historical-ligatures | no-historical-ligatures ]
+    /// <contextual-alt-values>    = [ contextual | no-contextual ]
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut result = Self::empty();
+        if input
+            .try_parse(|input| input.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(result);
+        }
+        if input
+            .try_parse(|input| input.expect_ident_matching("none"))
+            .is_ok()
+        {
+            return Ok(Self::NONE);
+        }
+
+        while let Ok(flag) = input.try_parse(|input| {
+            Ok(
+                match_ignore_ascii_case! { &input.expect_ident().map_err(|_| ())?,
+                    "common-ligatures" =>
+                        exclusive_value!((result, Self::COMMON_LIGATURES |
+                                                  Self::NO_COMMON_LIGATURES
+                                        ) => Self::COMMON_LIGATURES),
+                    "no-common-ligatures" =>
+                        exclusive_value!((result, Self::COMMON_LIGATURES |
+                                                  Self::NO_COMMON_LIGATURES
+                                        ) => Self::NO_COMMON_LIGATURES),
+                    "discretionary-ligatures" =>
+                        exclusive_value!((result, Self::DISCRETIONARY_LIGATURES |
+                                                  Self::NO_DISCRETIONARY_LIGATURES
+                                        ) => Self::DISCRETIONARY_LIGATURES),
+                    "no-discretionary-ligatures" =>
+                        exclusive_value!((result, Self::DISCRETIONARY_LIGATURES |
+                                                  Self::NO_DISCRETIONARY_LIGATURES
+                                        ) => Self::NO_DISCRETIONARY_LIGATURES),
+                    "historical-ligatures" =>
+                        exclusive_value!((result, Self::HISTORICAL_LIGATURES |
+                                                  Self::NO_HISTORICAL_LIGATURES
+                                        ) => Self::HISTORICAL_LIGATURES),
+                    "no-historical-ligatures" =>
+                        exclusive_value!((result, Self::HISTORICAL_LIGATURES |
+                                                  Self::NO_HISTORICAL_LIGATURES
+                                        ) => Self::NO_HISTORICAL_LIGATURES),
+                    "contextual" =>
+                        exclusive_value!((result, Self::CONTEXTUAL |
+                                                  Self::NO_CONTEXTUAL
+                                        ) => Self::CONTEXTUAL),
+                    "no-contextual" =>
+                        exclusive_value!((result, Self::CONTEXTUAL |
+                                                  Self::NO_CONTEXTUAL
+                                        ) => Self::NO_CONTEXTUAL),
+                    _ => return Err(()),
+                },
+            )
+        }) {
+            result.insert(flag);
+        }
+
+        if !result.is_empty() {
+            Ok(result)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+macro_rules! impl_variant_numeric {
+    {
+        $(
+            $(#[$($meta:tt)+])*
+            $ident:ident / $css:expr => $gecko:ident = $value:expr,
+        )+
+    } => {
+        bitflags! {
+            #[derive(MallocSizeOf, ToComputedValue, ToResolvedValue, ToShmem)]
+            /// Vairants of numeric values
+            pub struct FontVariantNumeric: u8 {
+                /// None of other variants are enabled.
+                const NORMAL = 0;
+                $(
+                    $(#[$($meta)+])*
+                    const $ident = $value;
+                )+
+            }
+        }
+
+        impl ToCss for FontVariantNumeric {
+            fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+            where
+                W: Write,
+            {
+                if self.is_empty() {
+                    return dest.write_str("normal");
+                }
+
+                let mut writer = SequenceWriter::new(dest, " ");
+                $(
+                    if self.intersects(FontVariantNumeric::$ident) {
+                        writer.raw_item($css)?;
+                    }
+                )+
+                Ok(())
+            }
+        }
+
+        /// Asserts that all variant-east-asian matches its NS_FONT_VARIANT_EAST_ASIAN_* value.
+        #[cfg(feature = "gecko")]
+        #[inline]
+        pub fn assert_variant_numeric_matches() {
+            use crate::gecko_bindings::structs;
+            $(
+                debug_assert_eq!(structs::$gecko as u8, FontVariantNumeric::$ident.bits());
+            )+
+        }
+
+        impl SpecifiedValueInfo for FontVariantNumeric {
+            fn collect_completion_keywords(f: KeywordsCollectFn) {
+                f(&["normal", $($css,)+]);
+            }
+        }
+    }
+}
+
+impl_variant_numeric! {
+    /// Enables display of lining numerals.
+    LINING_NUMS / "lining-nums" => NS_FONT_VARIANT_NUMERIC_LINING = 0x01,
+    /// Enables display of old-style numerals.
+    OLDSTYLE_NUMS / "oldstyle-nums" => NS_FONT_VARIANT_NUMERIC_OLDSTYLE = 0x02,
+    /// Enables display of proportional numerals.
+    PROPORTIONAL_NUMS / "proportional-nums" => NS_FONT_VARIANT_NUMERIC_PROPORTIONAL = 0x04,
+    /// Enables display of tabular numerals.
+    TABULAR_NUMS / "tabular-nums" => NS_FONT_VARIANT_NUMERIC_TABULAR = 0x08,
+    /// Enables display of lining diagonal fractions.
+    DIAGONAL_FRACTIONS / "diagonal-fractions" => NS_FONT_VARIANT_NUMERIC_DIAGONAL_FRACTIONS = 0x10,
+    /// Enables display of lining stacked fractions.
+    STACKED_FRACTIONS / "stacked-fractions" => NS_FONT_VARIANT_NUMERIC_STACKED_FRACTIONS = 0x20,
+    /// Enables display of letter forms used with ordinal numbers.
+    ORDINAL / "ordinal" => NS_FONT_VARIANT_NUMERIC_ORDINAL = 0x80,
+    /// Enables display of slashed zeros.
+    SLASHED_ZERO / "slashed-zero" => NS_FONT_VARIANT_NUMERIC_SLASHZERO = 0x40,
+}
+
+#[cfg(feature = "gecko")]
+impl FontVariantNumeric {
+    /// Obtain a specified value from a Gecko keyword value
+    ///
+    /// Intended for use with presentation attributes, not style structs
+    pub fn from_gecko_keyword(kw: u8) -> Self {
+        Self::from_bits_truncate(kw)
+    }
+
+    /// Transform into gecko keyword
+    pub fn to_gecko_keyword(self) -> u8 {
+        self.bits()
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl_gecko_keyword_conversions!(FontVariantNumeric, u8);
+
+impl Parse for FontVariantNumeric {
+    /// normal |
+    ///  [ <numeric-figure-values>   ||
+    ///    <numeric-spacing-values>  ||
+    ///    <numeric-fraction-values> ||
+    ///    ordinal                   ||
+    ///    slashed-zero ]
+    /// <numeric-figure-values>   = [ lining-nums | oldstyle-nums ]
+    /// <numeric-spacing-values>  = [ proportional-nums | tabular-nums ]
+    /// <numeric-fraction-values> = [ diagonal-fractions | stacked-fractions ]
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut result = Self::empty();
+
+        if input
+            .try_parse(|input| input.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(result);
+        }
+
+        while let Ok(flag) = input.try_parse(|input| {
+            Ok(
+                match_ignore_ascii_case! { &input.expect_ident().map_err(|_| ())?,
+                    "ordinal" =>
+                        exclusive_value!((result, Self::ORDINAL) => Self::ORDINAL),
+                    "slashed-zero" =>
+                        exclusive_value!((result, Self::SLASHED_ZERO) => Self::SLASHED_ZERO),
+                    "lining-nums" =>
+                        exclusive_value!((result, Self::LINING_NUMS |
+                                                  Self::OLDSTYLE_NUMS
+                                        ) => Self::LINING_NUMS),
+                    "oldstyle-nums" =>
+                        exclusive_value!((result, Self::LINING_NUMS |
+                                                  Self::OLDSTYLE_NUMS
+                                        ) => Self::OLDSTYLE_NUMS),
+                    "proportional-nums" =>
+                        exclusive_value!((result, Self::PROPORTIONAL_NUMS |
+                                                  Self::TABULAR_NUMS
+                                        ) => Self::PROPORTIONAL_NUMS),
+                    "tabular-nums" =>
+                        exclusive_value!((result, Self::PROPORTIONAL_NUMS |
+                                                  Self::TABULAR_NUMS
+                                        ) => Self::TABULAR_NUMS),
+                    "diagonal-fractions" =>
+                        exclusive_value!((result, Self::DIAGONAL_FRACTIONS |
+                                                  Self::STACKED_FRACTIONS
+                                        ) => Self::DIAGONAL_FRACTIONS),
+                    "stacked-fractions" =>
+                        exclusive_value!((result, Self::DIAGONAL_FRACTIONS |
+                                                  Self::STACKED_FRACTIONS
+                                        ) => Self::STACKED_FRACTIONS),
+                    _ => return Err(()),
+                },
+            )
+        }) {
+            result.insert(flag);
+        }
+
+        if !result.is_empty() {
+            Ok(result)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+/// This property provides low-level control over OpenType or TrueType font features.
+pub type FontFeatureSettings = FontSettings<FeatureTagValue<Integer>>;
+
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+/// Whether user agents are allowed to synthesize bold or oblique font faces
+/// when a font family lacks those faces, or a small-caps variant when this is
+/// not supported by the face.
+pub struct FontSynthesis {
+    /// If a `font-weight` is requested that the font family does not contain,
+    /// the user agent may synthesize the requested weight from the weights
+    /// that do exist in the font family.
+    pub weight: bool,
+    /// If a font-style is requested that the font family does not contain,
+    /// the user agent may synthesize the requested style from the normal face in the font family.
+    pub style: bool,
+    /// This bit controls whether the user agent is allowed to synthesize small caps variant
+    /// when a font face lacks it.
+    pub small_caps: bool,
+}
+
+impl FontSynthesis {
+    #[inline]
+    /// Get the default value of font-synthesis
+    pub fn get_initial_value() -> Self {
+        FontSynthesis {
+            weight: true,
+            style: true,
+            small_caps: true,
+        }
+    }
+    #[inline]
+    /// Get the 'none' value of font-synthesis
+    pub fn none() -> Self {
+        FontSynthesis {
+            weight: false,
+            style: false,
+            small_caps: false,
+        }
+    }
+    #[inline]
+    /// Return true if this is the 'none' value
+    pub fn is_none(&self) -> bool {
+        *self == Self::none()
+    }
+}
+
+impl Parse for FontSynthesis {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<FontSynthesis, ParseError<'i>> {
+        let mut result = Self::none();
+        while let Ok(ident) = input.try_parse(|i| i.expect_ident_cloned()) {
+            match_ignore_ascii_case! { &ident,
+                "none" if result.is_none() => return Ok(result),
+                "weight" if !result.weight => result.weight = true,
+                "style" if !result.style => result.style = true,
+                "small-caps" if !result.small_caps &&
+                                static_prefs::pref!("layout.css.font-synthesis-small-caps.enabled")
+                                    => result.small_caps = true,
+                _ => return Err(input.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident))),
+            }
+        }
+        if !result.is_none() {
+            Ok(result)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+impl ToCss for FontSynthesis {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.is_none() {
+            return dest.write_str("none");
+        }
+
+        let mut need_space = false;
+        if self.weight {
+            dest.write_str("weight")?;
+            need_space = true;
+        }
+        if self.style {
+            if need_space {
+                dest.write_str(" ")?;
+            }
+            dest.write_str("style")?;
+            need_space = true;
+        }
+        if self.small_caps {
+            if need_space {
+                dest.write_str(" ")?;
+            }
+            dest.write_str("small-caps")?;
+        }
+        Ok(())
+    }
+}
+
+impl SpecifiedValueInfo for FontSynthesis {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&["none", "weight", "style"]);
+        if static_prefs::pref!("layout.css.font-synthesis-small-caps.enabled") {
+            f(&["small-caps"]);
+        }
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl From<u8> for FontSynthesis {
+    fn from(bits: u8) -> FontSynthesis {
+        use crate::gecko_bindings::structs;
+
+        FontSynthesis {
+            weight: bits & structs::NS_FONT_SYNTHESIS_WEIGHT as u8 != 0,
+            style: bits & structs::NS_FONT_SYNTHESIS_STYLE as u8 != 0,
+            small_caps: bits & structs::NS_FONT_SYNTHESIS_SMALL_CAPS as u8 != 0,
+        }
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl From<FontSynthesis> for u8 {
+    fn from(v: FontSynthesis) -> u8 {
+        use crate::gecko_bindings::structs;
+
+        let mut bits: u8 = 0;
+        if v.weight {
+            bits |= structs::NS_FONT_SYNTHESIS_WEIGHT as u8;
+        }
+        if v.style {
+            bits |= structs::NS_FONT_SYNTHESIS_STYLE as u8;
+        }
+        if v.small_caps {
+            bits |= structs::NS_FONT_SYNTHESIS_SMALL_CAPS as u8;
+        }
+        bits
+    }
+}
+
+#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+/// Allows authors to explicitly specify the language system of the font,
+/// overriding the language system implied by the content language
+pub enum FontLanguageOverride {
+    /// When rendering with OpenType fonts,
+    /// the content language of the element is
+    /// used to infer the OpenType language system
+    Normal,
+    /// Single three-letter case-sensitive OpenType language system tag,
+    /// specifies the OpenType language system to be used instead of
+    /// the language system implied by the language of the element
+    Override(Box<str>),
+}
+
+impl FontLanguageOverride {
+    #[inline]
+    /// Get default value with `normal`
+    pub fn normal() -> FontLanguageOverride {
+        FontLanguageOverride::Normal
+    }
+
+    /// The ToComputedValue implementation for non-system-font
+    /// FontLanguageOverride, used for @font-face descriptors.
+    #[inline]
+    pub fn compute_non_system(&self) -> computed::FontLanguageOverride {
+        match *self {
+            FontLanguageOverride::Normal => computed::FontLanguageOverride::zero(),
+            FontLanguageOverride::Override(ref lang) => {
+                computed::FontLanguageOverride::from_str(lang)
+            },
+        }
+    }
+}
+
+impl ToComputedValue for FontLanguageOverride {
+    type ComputedValue = computed::FontLanguageOverride;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> computed::FontLanguageOverride {
+        self.compute_non_system()
+    }
+    #[inline]
+    fn from_computed_value(computed: &computed::FontLanguageOverride) -> Self {
+        if *computed == computed::FontLanguageOverride::zero() {
+            return FontLanguageOverride::Normal;
+        }
+        FontLanguageOverride::Override(computed.to_str(&mut [0; 4]).into())
+    }
+}
+
+impl Parse for FontLanguageOverride {
+    /// normal | <string>
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<FontLanguageOverride, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(FontLanguageOverride::Normal);
+        }
+
+        let string = input.expect_string()?;
+        Ok(FontLanguageOverride::Override(
+            string.as_ref().to_owned().into_boxed_str(),
+        ))
+    }
+}
+
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// Allows authors to choose a palette from those supported by a color font
+/// (and potentially @font-palette-values overrides).
+pub struct FontPalette(Atom);
+
+#[allow(missing_docs)]
+impl FontPalette {
+    pub fn normal() -> Self { Self(atom!("normal")) }
+    pub fn light() -> Self { Self(atom!("light")) }
+    pub fn dark() -> Self { Self(atom!("dark")) }
+}
+
+impl Parse for FontPalette {
+    /// normal | light | dark | dashed-ident
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<FontPalette, ParseError<'i>> {
+        let location = input.current_source_location();
+        let ident = input.expect_ident()?;
+        match_ignore_ascii_case! { &ident,
+            "normal" => Ok(Self::normal()),
+            "light" => Ok(Self::light()),
+            "dark" => Ok(Self::dark()),
+            _ => if ident.starts_with("--") {
+                Ok(Self(Atom::from(ident.as_ref())))
+            } else {
+                Err(location.new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())))
+            },
+        }
+    }
+}
+
+impl ToCss for FontPalette {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        serialize_atom_identifier(&self.0, dest)
+    }
+}
+
+/// This property provides low-level control over OpenType or TrueType font
+/// variations.
+pub type FontVariationSettings = FontSettings<VariationValue<Number>>;
+
+
+fn parse_one_feature_value<'i, 't>(
+    context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+) -> Result<Integer, ParseError<'i>> {
+    if let Ok(integer) = input.try_parse(|i| Integer::parse_non_negative(context, i)) {
+        return Ok(integer);
+    }
+
+    try_match_ident_ignore_ascii_case! { input,
+        "on" => Ok(Integer::new(1)),
+        "off" => Ok(Integer::new(0)),
+    }
+}
+
+impl Parse for FeatureTagValue<Integer> {
+    /// https://drafts.csswg.org/css-fonts-4/#feature-tag-value
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let tag = FontTag::parse(context, input)?;
+        let value = input
+            .try_parse(|i| parse_one_feature_value(context, i))
+            .unwrap_or_else(|_| Integer::new(1));
+
+        Ok(Self { tag, value })
+    }
+}
+
+impl Parse for VariationValue<Number> {
+    /// This is the `<string> <number>` part of the font-variation-settings
+    /// syntax.
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let tag = FontTag::parse(context, input)?;
+        let value = Number::parse(context, input)?;
+        Ok(Self { tag, value })
+    }
+}
+
+/// A metrics override value for a @font-face descriptor
+///
+/// https://drafts.csswg.org/css-fonts/#font-metrics-override-desc
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+pub enum MetricsOverride {
+    /// A non-negative `<percentage>` of the computed font size
+    Override(NonNegativePercentage),
+    /// Normal metrics from the font.
+    Normal,
+}
+
+impl MetricsOverride {
+    #[inline]
+    /// Get default value with `normal`
+    pub fn normal() -> MetricsOverride {
+        MetricsOverride::Normal
+    }
+
+    /// The ToComputedValue implementation, used for @font-face descriptors.
+    ///
+    /// Valid override percentages must be non-negative; we return -1.0 to indicate
+    /// the absence of an override (i.e. 'normal').
+    #[inline]
+    pub fn compute(&self) -> ComputedPercentage {
+        match *self {
+            MetricsOverride::Normal => ComputedPercentage(-1.0),
+            MetricsOverride::Override(percent) => ComputedPercentage(percent.0.get()),
+        }
+    }
+}
+
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+/// text-zoom. Enable if true, disable if false
+pub struct XTextZoom(#[css(skip)] pub bool);
+
+impl Parse for XTextZoom {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<XTextZoom, ParseError<'i>> {
+        debug_assert!(
+            false,
+            "Should be set directly by presentation attributes only."
+        );
+        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+/// Internal property that reflects the lang attribute
+pub struct XLang(#[css(skip)] pub Atom);
+
+impl XLang {
+    #[inline]
+    /// Get default value for `-x-lang`
+    pub fn get_initial_value() -> XLang {
+        XLang(atom!(""))
+    }
+}
+
+impl Parse for XLang {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<XLang, ParseError<'i>> {
+        debug_assert!(
+            false,
+            "Should be set directly by presentation attributes only."
+        );
+        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
+#[derive(Clone, Copy, Debug, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+/// Specifies the minimum font size allowed due to changes in scriptlevel.
+/// Ref: https://wiki.mozilla.org/MathML:mstyle
+pub struct MozScriptMinSize(pub NoCalcLength);
+
+impl MozScriptMinSize {
+    #[inline]
+    /// Calculate initial value of -moz-script-min-size.
+    pub fn get_initial_value() -> Length {
+        Length::new(DEFAULT_SCRIPT_MIN_SIZE_PT as f32 * PX_PER_PT)
+    }
+}
+
+impl Parse for MozScriptMinSize {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<MozScriptMinSize, ParseError<'i>> {
+        debug_assert!(
+            false,
+            "Should be set directly by presentation attributes only."
+        );
+        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+/// A value for the `math-depth` property.
+/// https://mathml-refresh.github.io/mathml-core/#the-math-script-level-property
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
+#[derive(Clone, Copy, Debug, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum MathDepth {
+    /// Increment math-depth if math-style is compact.
+    AutoAdd,
+
+    /// Add the function's argument to math-depth.
+    #[css(function)]
+    Add(Integer),
+
+    /// Set math-depth to the specified value.
+    Absolute(Integer),
+}
+
+impl Parse for MathDepth {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<MathDepth, ParseError<'i>> {
+        if input
+            .try_parse(|i| i.expect_ident_matching("auto-add"))
+            .is_ok()
+        {
+            return Ok(MathDepth::AutoAdd);
+        }
+        if let Ok(math_depth_value) = input.try_parse(|input| Integer::parse(context, input)) {
+            return Ok(MathDepth::Absolute(math_depth_value));
+        }
+        input.expect_function_matching("add")?;
+        let math_depth_delta_value =
+            input.parse_nested_block(|input| Integer::parse(context, input))?;
+        Ok(MathDepth::Add(math_depth_delta_value))
+    }
+}
+
+#[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+/// Specifies the multiplier to be used to adjust font size
+/// due to changes in scriptlevel.
+///
+/// Ref: https://www.w3.org/TR/MathML3/chapter3.html#presm.mstyle.attrs
+pub struct MozScriptSizeMultiplier(pub f32);
+
+impl MozScriptSizeMultiplier {
+    #[inline]
+    /// Get default value of `-moz-script-size-multiplier`
+    pub fn get_initial_value() -> MozScriptSizeMultiplier {
+        MozScriptSizeMultiplier(DEFAULT_SCRIPT_SIZE_MULTIPLIER as f32)
+    }
+}
+
+impl Parse for MozScriptSizeMultiplier {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<MozScriptSizeMultiplier, ParseError<'i>> {
+        debug_assert!(
+            false,
+            "Should be set directly by presentation attributes only."
+        );
+        Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+impl From<f32> for MozScriptSizeMultiplier {
+    fn from(v: f32) -> Self {
+        MozScriptSizeMultiplier(v)
+    }
+}
+
+impl From<MozScriptSizeMultiplier> for f32 {
+    fn from(v: MozScriptSizeMultiplier) -> f32 {
+        v.0
+    }
+}
diff --git a/servo/components/style/values/specified/gecko.rs b/servo/components/style/values/specified/gecko.rs
new file mode 100644
index 0000000000..e721add59c
--- /dev/null
+++ b/servo/components/style/values/specified/gecko.rs
@@ -0,0 +1,82 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for legacy Gecko-only properties.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::{self, Length, LengthPercentage};
+use crate::values::generics::rect::Rect;
+use cssparser::{Parser, Token};
+use std::fmt;
+use style_traits::values::SequenceWriter;
+use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+
+fn parse_pixel_or_percent<'i, 't>(
+    _context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+) -> Result<LengthPercentage, ParseError<'i>> {
+    let location = input.current_source_location();
+    let token = input.next()?;
+    let value = match *token {
+        Token::Dimension {
+            value, ref unit, ..
+        } => {
+            match_ignore_ascii_case! { unit,
+                "px" => Ok(LengthPercentage::new_length(Length::new(value))),
+                _ => Err(()),
+            }
+        },
+        Token::Percentage { unit_value, .. } => Ok(LengthPercentage::new_percent(
+            computed::Percentage(unit_value),
+        )),
+        _ => Err(()),
+    };
+    value.map_err(|()| location.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+}
+
+/// The value of an IntersectionObserver's rootMargin property.
+///
+/// Only bare px or percentage values are allowed. Other length units and
+/// calc() values are not allowed.
+///
+/// <https://w3c.github.io/IntersectionObserver/#parse-a-root-margin>
+#[repr(transparent)]
+pub struct IntersectionObserverRootMargin(pub Rect<LengthPercentage>);
+
+impl Parse for IntersectionObserverRootMargin {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        use crate::Zero;
+        if input.is_exhausted() {
+            // If there are zero elements in tokens, set tokens to ["0px"].
+            return Ok(IntersectionObserverRootMargin(Rect::all(
+                LengthPercentage::zero(),
+            )));
+        }
+        let rect = Rect::parse_with(context, input, parse_pixel_or_percent)?;
+        Ok(IntersectionObserverRootMargin(rect))
+    }
+}
+
+// Strictly speaking this is not ToCss. It's serializing for DOM. But
+// we can just reuse the infrastructure of this.
+//
+// <https://w3c.github.io/IntersectionObserver/#dom-intersectionobserver-rootmargin>
+impl ToCss for IntersectionObserverRootMargin {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        // We cannot use the ToCss impl of Rect, because that would
+        // merge items when they are equal. We want to list them all.
+        let mut writer = SequenceWriter::new(dest, " ");
+        let rect = &self.0;
+        writer.item(&rect.0)?;
+        writer.item(&rect.1)?;
+        writer.item(&rect.2)?;
+        writer.item(&rect.3)
+    }
+}
diff --git a/servo/components/style/values/specified/grid.rs b/servo/components/style/values/specified/grid.rs
new file mode 100644
index 0000000000..8bfa4a363b
--- /dev/null
+++ b/servo/components/style/values/specified/grid.rs
@@ -0,0 +1,349 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the computed value of
+//! [grids](https://drafts.csswg.org/css-grid/)
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::grid::{GridTemplateComponent, ImplicitGridTracks, RepeatCount};
+use crate::values::generics::grid::{LineNameList, TrackBreadth, TrackRepeat, TrackSize};
+use crate::values::generics::grid::{TrackList, TrackListValue};
+use crate::values::specified::{Integer, LengthPercentage};
+use crate::values::{CSSFloat, CustomIdent};
+use cssparser::{ParseError as CssParseError, Parser, Token};
+use std::mem;
+use style_traits::{ParseError, StyleParseErrorKind};
+
+/// Parse a single flexible length.
+pub fn parse_flex<'i, 't>(input: &mut Parser<'i, 't>) -> Result<CSSFloat, ParseError<'i>> {
+    let location = input.current_source_location();
+    match *input.next()? {
+        Token::Dimension {
+            value, ref unit, ..
+        } if unit.eq_ignore_ascii_case("fr") && value.is_sign_positive() => Ok(value),
+        ref t => Err(location.new_unexpected_token_error(t.clone())),
+    }
+}
+
+impl<L> TrackBreadth<L> {
+    fn parse_keyword<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Self, ParseError<'i>> {
+        #[derive(Parse)]
+        enum TrackKeyword {
+            Auto,
+            MaxContent,
+            MinContent,
+        }
+
+        Ok(match TrackKeyword::parse(input)? {
+            TrackKeyword::Auto => TrackBreadth::Auto,
+            TrackKeyword::MaxContent => TrackBreadth::MaxContent,
+            TrackKeyword::MinContent => TrackBreadth::MinContent,
+        })
+    }
+}
+
+impl Parse for TrackBreadth<LengthPercentage> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // FIXME: This and other callers in this file should use
+        // NonNegativeLengthPercentage instead.
+        //
+        // Though it seems these cannot be animated so it's ~ok.
+        if let Ok(lp) = input.try_parse(|i| LengthPercentage::parse_non_negative(context, i)) {
+            return Ok(TrackBreadth::Breadth(lp));
+        }
+
+        if let Ok(f) = input.try_parse(parse_flex) {
+            return Ok(TrackBreadth::Fr(f));
+        }
+
+        Self::parse_keyword(input)
+    }
+}
+
+impl Parse for TrackSize<LengthPercentage> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(b) = input.try_parse(|i| TrackBreadth::parse(context, i)) {
+            return Ok(TrackSize::Breadth(b));
+        }
+
+        if input
+            .try_parse(|i| i.expect_function_matching("minmax"))
+            .is_ok()
+        {
+            return input.parse_nested_block(|input| {
+                let inflexible_breadth =
+                    match input.try_parse(|i| LengthPercentage::parse_non_negative(context, i)) {
+                        Ok(lp) => TrackBreadth::Breadth(lp),
+                        Err(..) => TrackBreadth::parse_keyword(input)?,
+                    };
+
+                input.expect_comma()?;
+                Ok(TrackSize::Minmax(
+                    inflexible_breadth,
+                    TrackBreadth::parse(context, input)?,
+                ))
+            });
+        }
+
+        input.expect_function_matching("fit-content")?;
+        let lp = input.parse_nested_block(|i| LengthPercentage::parse_non_negative(context, i))?;
+        Ok(TrackSize::FitContent(TrackBreadth::Breadth(lp)))
+    }
+}
+
+impl Parse for ImplicitGridTracks<TrackSize<LengthPercentage>> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        use style_traits::{Separator, Space};
+        let track_sizes = Space::parse(input, |i| TrackSize::parse(context, i))?;
+        if track_sizes.len() == 1 && track_sizes[0].is_initial() {
+            // A single track with the initial value is always represented by an empty slice.
+            return Ok(Default::default());
+        }
+        return Ok(ImplicitGridTracks(track_sizes.into()));
+    }
+}
+
+/// Parse the grid line names into a vector of owned strings.
+///
+/// <https://drafts.csswg.org/css-grid/#typedef-line-names>
+pub fn parse_line_names<'i, 't>(
+    input: &mut Parser<'i, 't>,
+) -> Result<crate::OwnedSlice<CustomIdent>, ParseError<'i>> {
+    input.expect_square_bracket_block()?;
+    input.parse_nested_block(|input| {
+        let mut values = vec![];
+        while let Ok((loc, ident)) = input.try_parse(|i| -> Result<_, CssParseError<()>> {
+            Ok((i.current_source_location(), i.expect_ident_cloned()?))
+        }) {
+            let ident = CustomIdent::from_ident(loc, &ident, &["span", "auto"])?;
+            values.push(ident);
+        }
+
+        Ok(values.into())
+    })
+}
+
+/// The type of `repeat` function (only used in parsing).
+///
+/// <https://drafts.csswg.org/css-grid/#typedef-track-repeat>
+#[derive(Clone, Copy, Debug, PartialEq, SpecifiedValueInfo)]
+#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
+enum RepeatType {
+    /// [`<auto-repeat>`](https://drafts.csswg.org/css-grid/#typedef-auto-repeat)
+    Auto,
+    /// [`<track-repeat>`](https://drafts.csswg.org/css-grid/#typedef-track-repeat)
+    Normal,
+    /// [`<fixed-repeat>`](https://drafts.csswg.org/css-grid/#typedef-fixed-repeat)
+    Fixed,
+}
+
+impl TrackRepeat<LengthPercentage, Integer> {
+    fn parse_with_repeat_type<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<(Self, RepeatType), ParseError<'i>> {
+        input
+            .try_parse(|i| i.expect_function_matching("repeat").map_err(|e| e.into()))
+            .and_then(|_| {
+                input.parse_nested_block(|input| {
+                    let count = RepeatCount::parse(context, input)?;
+                    input.expect_comma()?;
+
+                    let is_auto = count == RepeatCount::AutoFit || count == RepeatCount::AutoFill;
+                    let mut repeat_type = if is_auto {
+                        RepeatType::Auto
+                    } else {
+                        // <fixed-size> is a subset of <track-size>, so it should work for both
+                        RepeatType::Fixed
+                    };
+
+                    let mut names = vec![];
+                    let mut values = vec![];
+                    let mut current_names;
+
+                    loop {
+                        current_names = input.try_parse(parse_line_names).unwrap_or_default();
+                        if let Ok(track_size) = input.try_parse(|i| TrackSize::parse(context, i)) {
+                            if !track_size.is_fixed() {
+                                if is_auto {
+                                    // should be <fixed-size> for <auto-repeat>
+                                    return Err(input
+                                        .new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                                }
+
+                                if repeat_type == RepeatType::Fixed {
+                                    repeat_type = RepeatType::Normal // <track-size> for sure
+                                }
+                            }
+
+                            values.push(track_size);
+                            names.push(current_names);
+                        } else {
+                            if values.is_empty() {
+                                // expecting at least one <track-size>
+                                return Err(
+                                    input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                                );
+                            }
+
+                            names.push(current_names); // final `<line-names>`
+                            break; // no more <track-size>, breaking
+                        }
+                    }
+
+                    let repeat = TrackRepeat {
+                        count,
+                        track_sizes: values.into(),
+                        line_names: names.into(),
+                    };
+
+                    Ok((repeat, repeat_type))
+                })
+            })
+    }
+}
+
+impl Parse for TrackList<LengthPercentage, Integer> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut current_names = vec![];
+        let mut names = vec![];
+        let mut values = vec![];
+
+        // Whether we've parsed an `<auto-repeat>` value.
+        let mut auto_repeat_index = None;
+        // assume that everything is <fixed-size>. This flag is useful when we encounter <auto-repeat>
+        let mut at_least_one_not_fixed = false;
+        loop {
+            current_names
+                .extend_from_slice(&mut input.try_parse(parse_line_names).unwrap_or_default());
+            if let Ok(track_size) = input.try_parse(|i| TrackSize::parse(context, i)) {
+                if !track_size.is_fixed() {
+                    at_least_one_not_fixed = true;
+                    if auto_repeat_index.is_some() {
+                        // <auto-track-list> only accepts <fixed-size> and <fixed-repeat>
+                        return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                    }
+                }
+
+                let vec = mem::replace(&mut current_names, vec![]);
+                names.push(vec.into());
+                values.push(TrackListValue::TrackSize(track_size));
+            } else if let Ok((repeat, type_)) =
+                input.try_parse(|i| TrackRepeat::parse_with_repeat_type(context, i))
+            {
+                match type_ {
+                    RepeatType::Normal => {
+                        at_least_one_not_fixed = true;
+                        if auto_repeat_index.is_some() {
+                            // only <fixed-repeat>
+                            return Err(
+                                input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                            );
+                        }
+                    },
+                    RepeatType::Auto => {
+                        if auto_repeat_index.is_some() || at_least_one_not_fixed {
+                            // We've either seen <auto-repeat> earlier, or there's at least one non-fixed value
+                            return Err(
+                                input.new_custom_error(StyleParseErrorKind::UnspecifiedError)
+                            );
+                        }
+                        auto_repeat_index = Some(values.len());
+                    },
+                    RepeatType::Fixed => {},
+                }
+
+                let vec = mem::replace(&mut current_names, vec![]);
+                names.push(vec.into());
+                values.push(TrackListValue::TrackRepeat(repeat));
+            } else {
+                if values.is_empty() && auto_repeat_index.is_none() {
+                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+
+                names.push(current_names.into());
+                break;
+            }
+        }
+
+        Ok(TrackList {
+            auto_repeat_index: auto_repeat_index.unwrap_or(std::usize::MAX),
+            values: values.into(),
+            line_names: names.into(),
+        })
+    }
+}
+
+#[cfg(feature = "gecko")]
+#[inline]
+fn allow_grid_template_subgrids() -> bool {
+    true
+}
+
+#[cfg(feature = "servo")]
+#[inline]
+fn allow_grid_template_subgrids() -> bool {
+    false
+}
+
+#[cfg(feature = "gecko")]
+#[inline]
+fn allow_grid_template_masonry() -> bool {
+    static_prefs::pref!("layout.css.grid-template-masonry-value.enabled")
+}
+
+#[cfg(feature = "servo")]
+#[inline]
+fn allow_grid_template_masonry() -> bool {
+    false
+}
+
+impl Parse for GridTemplateComponent<LengthPercentage, Integer> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(GridTemplateComponent::None);
+        }
+
+        Self::parse_without_none(context, input)
+    }
+}
+
+impl GridTemplateComponent<LengthPercentage, Integer> {
+    /// Parses a `GridTemplateComponent<LengthPercentage>` except `none` keyword.
+    pub fn parse_without_none<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if allow_grid_template_subgrids() {
+            if let Ok(t) = input.try_parse(|i| LineNameList::parse(context, i)) {
+                return Ok(GridTemplateComponent::Subgrid(Box::new(t)));
+            }
+        }
+        if allow_grid_template_masonry() {
+            if input
+                .try_parse(|i| i.expect_ident_matching("masonry"))
+                .is_ok()
+            {
+                return Ok(GridTemplateComponent::Masonry);
+            }
+        }
+        let track_list = TrackList::parse(context, input)?;
+        Ok(GridTemplateComponent::TrackList(Box::new(track_list)))
+    }
+}
diff --git a/servo/components/style/values/specified/image.rs b/servo/components/style/values/specified/image.rs
new file mode 100644
index 0000000000..35d882b18d
--- /dev/null
+++ b/servo/components/style/values/specified/image.rs
@@ -0,0 +1,1273 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the specified value of
+//! [`image`][image]s
+//!
+//! [image]: https://drafts.csswg.org/css-images/#image-values
+
+use crate::custom_properties::SpecifiedValue;
+use crate::parser::{Parse, ParserContext};
+use crate::stylesheets::CorsMode;
+use crate::values::generics::image::PaintWorklet;
+use crate::values::generics::image::{
+    self as generic, Circle, Ellipse, GradientCompatMode, ShapeExtent,
+};
+use crate::values::generics::position::Position as GenericPosition;
+use crate::values::generics::NonNegative;
+use crate::values::specified::position::{HorizontalPositionKeyword, VerticalPositionKeyword};
+use crate::values::specified::position::{Position, PositionComponent, Side};
+use crate::values::specified::url::SpecifiedImageUrl;
+use crate::values::specified::{
+    Angle, AngleOrPercentage, Color, Length, LengthPercentage, NonNegativeLength,
+    NonNegativeLengthPercentage, Resolution,
+};
+use crate::values::specified::{Number, NumberOrPercentage, Percentage};
+use crate::Atom;
+use cssparser::{Delimiter, Parser, Token};
+use selectors::parser::SelectorParseErrorKind;
+#[cfg(feature = "servo")]
+use servo_url::ServoUrl;
+use std::cmp::Ordering;
+use std::fmt::{self, Write};
+use style_traits::{CssType, CssWriter, KeywordsCollectFn, ParseError};
+use style_traits::{SpecifiedValueInfo, StyleParseErrorKind, ToCss};
+
+/// Specified values for an image according to CSS-IMAGES.
+/// <https://drafts.csswg.org/css-images/#image-values>
+pub type Image =
+    generic::Image<Gradient, MozImageRect, SpecifiedImageUrl, Color, Percentage, Resolution>;
+
+// Images should remain small, see https://github.com/servo/servo/pull/18430
+size_of_test!(Image, 16);
+
+/// Specified values for a CSS gradient.
+/// <https://drafts.csswg.org/css-images/#gradients>
+pub type Gradient = generic::Gradient<
+    LineDirection,
+    LengthPercentage,
+    NonNegativeLength,
+    NonNegativeLengthPercentage,
+    Position,
+    Angle,
+    AngleOrPercentage,
+    Color,
+>;
+
+/// Specified values for CSS cross-fade
+/// cross-fade( CrossFadeElement, ...)
+/// <https://drafts.csswg.org/css-images-4/#cross-fade-function>
+pub type CrossFade = generic::CrossFade<Image, Color, Percentage>;
+/// CrossFadeElement = percent? CrossFadeImage
+pub type CrossFadeElement = generic::CrossFadeElement<Image, Color, Percentage>;
+/// CrossFadeImage = image | color
+pub type CrossFadeImage = generic::CrossFadeImage<Image, Color>;
+
+/// `image-set()`
+pub type ImageSet = generic::ImageSet<Image, Resolution>;
+
+/// Each of the arguments to `image-set()`
+pub type ImageSetItem = generic::ImageSetItem<Image, Resolution>;
+
+type LengthPercentageItemList = crate::OwnedSlice<generic::GradientItem<Color, LengthPercentage>>;
+
+#[cfg(feature = "gecko")]
+fn cross_fade_enabled() -> bool {
+    static_prefs::pref!("layout.css.cross-fade.enabled")
+}
+
+#[cfg(feature = "servo")]
+fn cross_fade_enabled() -> bool {
+    false
+}
+
+impl SpecifiedValueInfo for Gradient {
+    const SUPPORTED_TYPES: u8 = CssType::GRADIENT;
+
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        // This list here should keep sync with that in Gradient::parse.
+        f(&[
+            "linear-gradient",
+            "-webkit-linear-gradient",
+            "-moz-linear-gradient",
+            "repeating-linear-gradient",
+            "-webkit-repeating-linear-gradient",
+            "-moz-repeating-linear-gradient",
+            "radial-gradient",
+            "-webkit-radial-gradient",
+            "-moz-radial-gradient",
+            "repeating-radial-gradient",
+            "-webkit-repeating-radial-gradient",
+            "-moz-repeating-radial-gradient",
+            "-webkit-gradient",
+            "conic-gradient",
+            "repeating-conic-gradient",
+        ]);
+    }
+}
+
+// Need to manually implement as whether or not cross-fade shows up in
+// completions & etc is dependent on it being enabled.
+impl<Image, Color, Percentage> SpecifiedValueInfo for generic::CrossFade<Image, Color, Percentage> {
+    const SUPPORTED_TYPES: u8 = 0;
+
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        if cross_fade_enabled() {
+            f(&["cross-fade"]);
+        }
+    }
+}
+
+impl<Image, Resolution> SpecifiedValueInfo for generic::ImageSet<Image, Resolution> {
+    const SUPPORTED_TYPES: u8 = 0;
+
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&["image-set"]);
+    }
+}
+
+/// A specified gradient line direction.
+///
+/// FIXME(emilio): This should be generic over Angle.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
+pub enum LineDirection {
+    /// An angular direction.
+    Angle(Angle),
+    /// A horizontal direction.
+    Horizontal(HorizontalPositionKeyword),
+    /// A vertical direction.
+    Vertical(VerticalPositionKeyword),
+    /// A direction towards a corner of a box.
+    Corner(HorizontalPositionKeyword, VerticalPositionKeyword),
+}
+
+/// A specified ending shape.
+pub type EndingShape = generic::EndingShape<NonNegativeLength, NonNegativeLengthPercentage>;
+
+/// Specified values for `moz-image-rect`
+/// -moz-image-rect(<uri>, top, right, bottom, left);
+#[cfg(all(feature = "gecko", not(feature = "cbindgen")))]
+pub type MozImageRect = generic::GenericMozImageRect<NumberOrPercentage, SpecifiedImageUrl>;
+
+#[cfg(not(feature = "gecko"))]
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+/// Empty enum on non-Gecko
+pub enum MozImageRect {}
+
+impl Parse for Image {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Image, ParseError<'i>> {
+        Image::parse_with_cors_mode(
+            context,
+            input,
+            CorsMode::None,
+            /* allow_none = */ true,
+            /* only_url = */ false,
+        )
+    }
+}
+
+impl Image {
+    fn parse_with_cors_mode<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+        allow_none: bool,
+        only_url: bool,
+    ) -> Result<Image, ParseError<'i>> {
+        if allow_none && input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(generic::Image::None);
+        }
+
+        if let Ok(url) = input
+            .try_parse(|input| SpecifiedImageUrl::parse_with_cors_mode(context, input, cors_mode))
+        {
+            return Ok(generic::Image::Url(url));
+        }
+
+        if let Ok(is) =
+            input.try_parse(|input| ImageSet::parse(context, input, cors_mode, only_url))
+        {
+            return Ok(generic::Image::ImageSet(Box::new(is)));
+        }
+
+        if only_url {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        if let Ok(gradient) = input.try_parse(|i| Gradient::parse(context, i)) {
+            return Ok(generic::Image::Gradient(Box::new(gradient)));
+        }
+
+        if cross_fade_enabled() {
+            if let Ok(cf) = input.try_parse(|input| CrossFade::parse(context, input, cors_mode)) {
+                return Ok(generic::Image::CrossFade(Box::new(cf)));
+            }
+        }
+        #[cfg(feature = "servo-layout-2013")]
+        {
+            if let Ok(paint_worklet) = input.try_parse(|i| PaintWorklet::parse(context, i)) {
+                return Ok(generic::Image::PaintWorklet(paint_worklet));
+            }
+        }
+        #[cfg(feature = "gecko")]
+        {
+            if let Ok(image_rect) =
+                input.try_parse(|input| MozImageRect::parse(context, input, cors_mode))
+            {
+                return Ok(generic::Image::Rect(Box::new(image_rect)));
+            }
+            Ok(generic::Image::Element(Image::parse_element(input)?))
+        }
+        #[cfg(not(feature = "gecko"))]
+        Err(input.new_error_for_next_token())
+    }
+}
+
+impl Image {
+    /// Creates an already specified image value from an already resolved URL
+    /// for insertion in the cascade.
+    #[cfg(feature = "servo")]
+    pub fn for_cascade(url: ServoUrl) -> Self {
+        use crate::values::CssUrl;
+        generic::Image::Url(CssUrl::for_cascade(url))
+    }
+
+    /// Parses a `-moz-element(# <element-id>)`.
+    #[cfg(feature = "gecko")]
+    fn parse_element<'i, 't>(input: &mut Parser<'i, 't>) -> Result<Atom, ParseError<'i>> {
+        input.try_parse(|i| i.expect_function_matching("-moz-element"))?;
+        let location = input.current_source_location();
+        input.parse_nested_block(|i| match *i.next()? {
+            Token::IDHash(ref id) => Ok(Atom::from(id.as_ref())),
+            ref t => Err(location.new_unexpected_token_error(t.clone())),
+        })
+    }
+
+    /// Provides an alternate method for parsing that associates the URL with
+    /// anonymous CORS headers.
+    pub fn parse_with_cors_anonymous<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Image, ParseError<'i>> {
+        Self::parse_with_cors_mode(
+            context,
+            input,
+            CorsMode::Anonymous,
+            /* allow_none = */ true,
+            /* only_url = */ false,
+        )
+    }
+
+    /// Provides an alternate method for parsing, but only for urls.
+    pub fn parse_only_url<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Image, ParseError<'i>> {
+        Self::parse_with_cors_mode(
+            context,
+            input,
+            CorsMode::None,
+            /* allow_none = */ false,
+            /* only_url = */ true,
+        )
+    }
+}
+
+impl CrossFade {
+    /// cross-fade() = cross-fade( <cf-image># )
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("cross-fade")?;
+        let elements = input.parse_nested_block(|input| {
+            input.parse_comma_separated(|input| CrossFadeElement::parse(context, input, cors_mode))
+        })?;
+        let elements = crate::OwnedSlice::from(elements);
+        Ok(Self { elements })
+    }
+}
+
+impl CrossFadeElement {
+    fn parse_percentage<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Option<Percentage> {
+        // We clamp our values here as this is the way that Safari and Chrome's
+        // implementation handle out-of-bounds percentages but whether or not
+        // this behavior follows the specification is still being discussed.
+        // See: <https://github.com/w3c/csswg-drafts/issues/5333>
+        input
+            .try_parse(|input| Percentage::parse_non_negative(context, input))
+            .ok()
+            .map(|p| p.clamp_to_hundred())
+    }
+
+    /// <cf-image> = <percentage>? && [ <image> | <color> ]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+    ) -> Result<Self, ParseError<'i>> {
+        // Try and parse a leading percent sign.
+        let mut percent = Self::parse_percentage(context, input);
+        // Parse the image
+        let image = CrossFadeImage::parse(context, input, cors_mode)?;
+        // Try and parse a trailing percent sign.
+        if percent.is_none() {
+            percent = Self::parse_percentage(context, input);
+        }
+        Ok(Self {
+            percent: percent.into(),
+            image,
+        })
+    }
+}
+
+impl CrossFadeImage {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(image) = input.try_parse(|input| {
+            Image::parse_with_cors_mode(
+                context, input, cors_mode, /* allow_none = */ false,
+                /* only_url = */ false,
+            )
+        }) {
+            return Ok(Self::Image(image));
+        }
+        Ok(Self::Color(Color::parse(context, input)?))
+    }
+}
+
+impl ImageSet {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+        only_url: bool,
+    ) -> Result<Self, ParseError<'i>> {
+        let function = input.expect_function()?;
+        match_ignore_ascii_case! { &function,
+            "-webkit-image-set" | "image-set" => {},
+            _ => {
+                let func = function.clone();
+                return Err(input.new_custom_error(StyleParseErrorKind::UnexpectedFunction(func)));
+            }
+        }
+        let items = input.parse_nested_block(|input| {
+            input.parse_comma_separated(|input| {
+                ImageSetItem::parse(context, input, cors_mode, only_url)
+            })
+        })?;
+        Ok(Self {
+            selected_index: 0,
+            items: items.into(),
+        })
+    }
+}
+
+impl ImageSetItem {
+    fn parse_type<'i>(p: &mut Parser<'i, '_>) -> Result<crate::OwnedStr, ParseError<'i>> {
+        p.expect_function_matching("type")?;
+        p.parse_nested_block(|input| Ok(input.expect_string()?.as_ref().to_owned().into()))
+    }
+
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+        only_url: bool,
+    ) -> Result<Self, ParseError<'i>> {
+        let image = match input.try_parse(|i| i.expect_url_or_string()) {
+            Ok(url) => Image::Url(SpecifiedImageUrl::parse_from_string(
+                url.as_ref().into(),
+                context,
+                cors_mode,
+            )),
+            Err(..) => Image::parse_with_cors_mode(
+                context, input, cors_mode, /* allow_none = */ false,
+                /* only_url = */ only_url,
+            )?,
+        };
+
+        let mut resolution = input
+            .try_parse(|input| Resolution::parse(context, input))
+            .ok();
+        let mime_type = input.try_parse(Self::parse_type).ok();
+
+        // Try to parse resolution after type().
+        if mime_type.is_some() && resolution.is_none() {
+            resolution = input
+                .try_parse(|input| Resolution::parse(context, input))
+                .ok();
+        }
+
+        let resolution = resolution.unwrap_or(Resolution::X(1.0));
+        let has_mime_type = mime_type.is_some();
+        let mime_type = mime_type.unwrap_or_default();
+
+        Ok(Self {
+            image,
+            resolution,
+            has_mime_type,
+            mime_type,
+        })
+    }
+}
+
+impl Parse for Gradient {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        enum Shape {
+            Linear,
+            Radial,
+            Conic,
+        }
+
+        let func = input.expect_function()?;
+        let (shape, repeating, compat_mode) = match_ignore_ascii_case! { &func,
+            "linear-gradient" => {
+                (Shape::Linear, false, GradientCompatMode::Modern)
+            },
+            "-webkit-linear-gradient" => {
+                (Shape::Linear, false, GradientCompatMode::WebKit)
+            },
+            #[cfg(feature = "gecko")]
+            "-moz-linear-gradient" => {
+                (Shape::Linear, false, GradientCompatMode::Moz)
+            },
+            "repeating-linear-gradient" => {
+                (Shape::Linear, true, GradientCompatMode::Modern)
+            },
+            "-webkit-repeating-linear-gradient" => {
+                (Shape::Linear, true, GradientCompatMode::WebKit)
+            },
+            #[cfg(feature = "gecko")]
+            "-moz-repeating-linear-gradient" => {
+                (Shape::Linear, true, GradientCompatMode::Moz)
+            },
+            "radial-gradient" => {
+                (Shape::Radial, false, GradientCompatMode::Modern)
+            },
+            "-webkit-radial-gradient" => {
+                (Shape::Radial, false, GradientCompatMode::WebKit)
+            },
+            #[cfg(feature = "gecko")]
+            "-moz-radial-gradient" => {
+                (Shape::Radial, false, GradientCompatMode::Moz)
+            },
+            "repeating-radial-gradient" => {
+                (Shape::Radial, true, GradientCompatMode::Modern)
+            },
+            "-webkit-repeating-radial-gradient" => {
+                (Shape::Radial, true, GradientCompatMode::WebKit)
+            },
+            #[cfg(feature = "gecko")]
+            "-moz-repeating-radial-gradient" => {
+                (Shape::Radial, true, GradientCompatMode::Moz)
+            },
+            "conic-gradient" => {
+                (Shape::Conic, false, GradientCompatMode::Modern)
+            },
+            "repeating-conic-gradient" => {
+                (Shape::Conic, true, GradientCompatMode::Modern)
+            },
+            "-webkit-gradient" => {
+                return input.parse_nested_block(|i| {
+                    Self::parse_webkit_gradient_argument(context, i)
+                });
+            },
+            _ => {
+                let func = func.clone();
+                return Err(input.new_custom_error(StyleParseErrorKind::UnexpectedFunction(func)));
+            }
+        };
+
+        Ok(input.parse_nested_block(|i| {
+            Ok(match shape {
+                Shape::Linear => Self::parse_linear(context, i, repeating, compat_mode)?,
+                Shape::Radial => Self::parse_radial(context, i, repeating, compat_mode)?,
+                Shape::Conic => Self::parse_conic(context, i, repeating)?,
+            })
+        })?)
+    }
+}
+
+impl Gradient {
+    fn parse_webkit_gradient_argument<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        use crate::values::specified::position::{
+            HorizontalPositionKeyword as X, VerticalPositionKeyword as Y,
+        };
+        type Point = GenericPosition<Component<X>, Component<Y>>;
+
+        #[derive(Clone, Copy, Parse)]
+        enum Component<S> {
+            Center,
+            Number(NumberOrPercentage),
+            Side(S),
+        }
+
+        impl LineDirection {
+            fn from_points(first: Point, second: Point) -> Self {
+                let h_ord = first.horizontal.partial_cmp(&second.horizontal);
+                let v_ord = first.vertical.partial_cmp(&second.vertical);
+                let (h, v) = match (h_ord, v_ord) {
+                    (Some(h), Some(v)) => (h, v),
+                    _ => return LineDirection::Vertical(Y::Bottom),
+                };
+                match (h, v) {
+                    (Ordering::Less, Ordering::Less) => LineDirection::Corner(X::Right, Y::Bottom),
+                    (Ordering::Less, Ordering::Equal) => LineDirection::Horizontal(X::Right),
+                    (Ordering::Less, Ordering::Greater) => LineDirection::Corner(X::Right, Y::Top),
+                    (Ordering::Equal, Ordering::Greater) => LineDirection::Vertical(Y::Top),
+                    (Ordering::Equal, Ordering::Equal) | (Ordering::Equal, Ordering::Less) => {
+                        LineDirection::Vertical(Y::Bottom)
+                    },
+                    (Ordering::Greater, Ordering::Less) => {
+                        LineDirection::Corner(X::Left, Y::Bottom)
+                    },
+                    (Ordering::Greater, Ordering::Equal) => LineDirection::Horizontal(X::Left),
+                    (Ordering::Greater, Ordering::Greater) => {
+                        LineDirection::Corner(X::Left, Y::Top)
+                    },
+                }
+            }
+        }
+
+        impl From<Point> for Position {
+            fn from(point: Point) -> Self {
+                Self::new(point.horizontal.into(), point.vertical.into())
+            }
+        }
+
+        impl Parse for Point {
+            fn parse<'i, 't>(
+                context: &ParserContext,
+                input: &mut Parser<'i, 't>,
+            ) -> Result<Self, ParseError<'i>> {
+                input.try_parse(|i| {
+                    let x = Component::parse(context, i)?;
+                    let y = Component::parse(context, i)?;
+
+                    Ok(Self::new(x, y))
+                })
+            }
+        }
+
+        impl<S: Side> From<Component<S>> for NumberOrPercentage {
+            fn from(component: Component<S>) -> Self {
+                match component {
+                    Component::Center => NumberOrPercentage::Percentage(Percentage::new(0.5)),
+                    Component::Number(number) => number,
+                    Component::Side(side) => {
+                        let p = if side.is_start() {
+                            Percentage::zero()
+                        } else {
+                            Percentage::hundred()
+                        };
+                        NumberOrPercentage::Percentage(p)
+                    },
+                }
+            }
+        }
+
+        impl<S: Side> From<Component<S>> for PositionComponent<S> {
+            fn from(component: Component<S>) -> Self {
+                match component {
+                    Component::Center => PositionComponent::Center,
+                    Component::Number(NumberOrPercentage::Number(number)) => {
+                        PositionComponent::Length(Length::from_px(number.value).into())
+                    },
+                    Component::Number(NumberOrPercentage::Percentage(p)) => {
+                        PositionComponent::Length(p.into())
+                    },
+                    Component::Side(side) => PositionComponent::Side(side, None),
+                }
+            }
+        }
+
+        impl<S: Copy + Side> Component<S> {
+            fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+                match (
+                    NumberOrPercentage::from(*self),
+                    NumberOrPercentage::from(*other),
+                ) {
+                    (NumberOrPercentage::Percentage(a), NumberOrPercentage::Percentage(b)) => {
+                        a.get().partial_cmp(&b.get())
+                    },
+                    (NumberOrPercentage::Number(a), NumberOrPercentage::Number(b)) => {
+                        a.value.partial_cmp(&b.value)
+                    },
+                    (_, _) => None,
+                }
+            }
+        }
+
+        let ident = input.expect_ident_cloned()?;
+        input.expect_comma()?;
+
+        Ok(match_ignore_ascii_case! { &ident,
+            "linear" => {
+                let first = Point::parse(context, input)?;
+                input.expect_comma()?;
+                let second = Point::parse(context, input)?;
+
+                let direction = LineDirection::from_points(first, second);
+                let items = Gradient::parse_webkit_gradient_stops(context, input, false)?;
+
+                generic::Gradient::Linear {
+                    direction,
+                    items,
+                    repeating: false,
+                    compat_mode: GradientCompatMode::Modern,
+                }
+            },
+            "radial" => {
+                let first_point = Point::parse(context, input)?;
+                input.expect_comma()?;
+                let first_radius = Number::parse_non_negative(context, input)?;
+                input.expect_comma()?;
+                let second_point = Point::parse(context, input)?;
+                input.expect_comma()?;
+                let second_radius = Number::parse_non_negative(context, input)?;
+
+                let (reverse_stops, point, radius) = if second_radius.value >= first_radius.value {
+                    (false, second_point, second_radius)
+                } else {
+                    (true, first_point, first_radius)
+                };
+
+                let rad = Circle::Radius(NonNegative(Length::from_px(radius.value)));
+                let shape = generic::EndingShape::Circle(rad);
+                let position: Position = point.into();
+                let items = Gradient::parse_webkit_gradient_stops(context, input, reverse_stops)?;
+
+                generic::Gradient::Radial {
+                    shape,
+                    position,
+                    items,
+                    repeating: false,
+                    compat_mode: GradientCompatMode::Modern,
+                }
+            },
+            _ => {
+                let e = SelectorParseErrorKind::UnexpectedIdent(ident.clone());
+                return Err(input.new_custom_error(e));
+            },
+        })
+    }
+
+    fn parse_webkit_gradient_stops<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        reverse_stops: bool,
+    ) -> Result<LengthPercentageItemList, ParseError<'i>> {
+        let mut items = input
+            .try_parse(|i| {
+                i.expect_comma()?;
+                i.parse_comma_separated(|i| {
+                    let function = i.expect_function()?.clone();
+                    let (color, mut p) = i.parse_nested_block(|i| {
+                        let p = match_ignore_ascii_case! { &function,
+                            "color-stop" => {
+                                let p = NumberOrPercentage::parse(context, i)?.to_percentage();
+                                i.expect_comma()?;
+                                p
+                            },
+                            "from" => Percentage::zero(),
+                            "to" => Percentage::hundred(),
+                            _ => {
+                                return Err(i.new_custom_error(
+                                    StyleParseErrorKind::UnexpectedFunction(function.clone())
+                                ))
+                            },
+                        };
+                        let color = Color::parse(context, i)?;
+                        if color == Color::CurrentColor {
+                            return Err(i.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                        }
+                        Ok((color.into(), p))
+                    })?;
+                    if reverse_stops {
+                        p.reverse();
+                    }
+                    Ok(generic::GradientItem::ComplexColorStop {
+                        color,
+                        position: p.into(),
+                    })
+                })
+            })
+            .unwrap_or(vec![]);
+
+        if items.is_empty() {
+            items = vec![
+                generic::GradientItem::ComplexColorStop {
+                    color: Color::transparent(),
+                    position: LengthPercentage::zero_percent(),
+                },
+                generic::GradientItem::ComplexColorStop {
+                    color: Color::transparent(),
+                    position: LengthPercentage::hundred_percent(),
+                },
+            ];
+        } else if items.len() == 1 {
+            let first = items[0].clone();
+            items.push(first);
+        } else {
+            items.sort_by(|a, b| {
+                match (a, b) {
+                    (
+                        &generic::GradientItem::ComplexColorStop {
+                            position: ref a_position,
+                            ..
+                        },
+                        &generic::GradientItem::ComplexColorStop {
+                            position: ref b_position,
+                            ..
+                        },
+                    ) => match (a_position, b_position) {
+                        (&LengthPercentage::Percentage(a), &LengthPercentage::Percentage(b)) => {
+                            return a.0.partial_cmp(&b.0).unwrap_or(Ordering::Equal);
+                        },
+                        _ => {},
+                    },
+                    _ => {},
+                }
+                if reverse_stops {
+                    Ordering::Greater
+                } else {
+                    Ordering::Less
+                }
+            })
+        }
+        Ok(items.into())
+    }
+
+    /// Not used for -webkit-gradient syntax and conic-gradient
+    fn parse_stops<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<LengthPercentageItemList, ParseError<'i>> {
+        let items =
+            generic::GradientItem::parse_comma_separated(context, input, LengthPercentage::parse)?;
+        if items.len() < 2 {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        Ok(items)
+    }
+
+    /// Parses a linear gradient.
+    /// GradientCompatMode can change during `-moz-` prefixed gradient parsing if it come across a `to` keyword.
+    fn parse_linear<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        repeating: bool,
+        mut compat_mode: GradientCompatMode,
+    ) -> Result<Self, ParseError<'i>> {
+        let direction = if let Ok(d) =
+            input.try_parse(|i| LineDirection::parse(context, i, &mut compat_mode))
+        {
+            input.expect_comma()?;
+            d
+        } else {
+            match compat_mode {
+                GradientCompatMode::Modern => {
+                    LineDirection::Vertical(VerticalPositionKeyword::Bottom)
+                },
+                _ => LineDirection::Vertical(VerticalPositionKeyword::Top),
+            }
+        };
+        let items = Gradient::parse_stops(context, input)?;
+
+        Ok(Gradient::Linear {
+            direction,
+            items,
+            repeating,
+            compat_mode,
+        })
+    }
+
+    /// Parses a radial gradient.
+    fn parse_radial<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        repeating: bool,
+        compat_mode: GradientCompatMode,
+    ) -> Result<Self, ParseError<'i>> {
+        let (shape, position) = match compat_mode {
+            GradientCompatMode::Modern => {
+                let shape = input.try_parse(|i| EndingShape::parse(context, i, compat_mode));
+                let position = input.try_parse(|i| {
+                    i.expect_ident_matching("at")?;
+                    Position::parse(context, i)
+                });
+                (shape, position.ok())
+            },
+            _ => {
+                let position = input.try_parse(|i| Position::parse(context, i));
+                let shape = input.try_parse(|i| {
+                    if position.is_ok() {
+                        i.expect_comma()?;
+                    }
+                    EndingShape::parse(context, i, compat_mode)
+                });
+                (shape, position.ok())
+            },
+        };
+
+        if shape.is_ok() || position.is_some() {
+            input.expect_comma()?;
+        }
+
+        let shape = shape.unwrap_or({
+            generic::EndingShape::Ellipse(Ellipse::Extent(ShapeExtent::FarthestCorner))
+        });
+
+        let position = position.unwrap_or(Position::center());
+
+        let items = Gradient::parse_stops(context, input)?;
+
+        Ok(Gradient::Radial {
+            shape,
+            position,
+            items,
+            repeating,
+            compat_mode,
+        })
+    }
+    fn parse_conic<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        repeating: bool,
+    ) -> Result<Self, ParseError<'i>> {
+        let angle = input.try_parse(|i| {
+            i.expect_ident_matching("from")?;
+            // Spec allows unitless zero start angles
+            // https://drafts.csswg.org/css-images-4/#valdef-conic-gradient-angle
+            Angle::parse_with_unitless(context, i)
+        });
+        let position = input.try_parse(|i| {
+            i.expect_ident_matching("at")?;
+            Position::parse(context, i)
+        });
+        if angle.is_ok() || position.is_ok() {
+            input.expect_comma()?;
+        }
+
+        let angle = angle.unwrap_or(Angle::zero());
+        let position = position.unwrap_or(Position::center());
+        let items = generic::GradientItem::parse_comma_separated(
+            context,
+            input,
+            AngleOrPercentage::parse_with_unitless,
+        )?;
+
+        if items.len() < 2 {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(Gradient::Conic {
+            angle,
+            position,
+            items,
+            repeating,
+        })
+    }
+}
+
+impl generic::LineDirection for LineDirection {
+    fn points_downwards(&self, compat_mode: GradientCompatMode) -> bool {
+        match *self {
+            LineDirection::Angle(ref angle) => angle.degrees() == 180.0,
+            LineDirection::Vertical(VerticalPositionKeyword::Bottom) => {
+                compat_mode == GradientCompatMode::Modern
+            },
+            LineDirection::Vertical(VerticalPositionKeyword::Top) => {
+                compat_mode != GradientCompatMode::Modern
+            },
+            _ => false,
+        }
+    }
+
+    fn to_css<W>(&self, dest: &mut CssWriter<W>, compat_mode: GradientCompatMode) -> fmt::Result
+    where
+        W: Write,
+    {
+        match *self {
+            LineDirection::Angle(angle) => angle.to_css(dest),
+            LineDirection::Horizontal(x) => {
+                if compat_mode == GradientCompatMode::Modern {
+                    dest.write_str("to ")?;
+                }
+                x.to_css(dest)
+            },
+            LineDirection::Vertical(y) => {
+                if compat_mode == GradientCompatMode::Modern {
+                    dest.write_str("to ")?;
+                }
+                y.to_css(dest)
+            },
+            LineDirection::Corner(x, y) => {
+                if compat_mode == GradientCompatMode::Modern {
+                    dest.write_str("to ")?;
+                }
+                x.to_css(dest)?;
+                dest.write_str(" ")?;
+                y.to_css(dest)
+            },
+        }
+    }
+}
+
+impl LineDirection {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        compat_mode: &mut GradientCompatMode,
+    ) -> Result<Self, ParseError<'i>> {
+        // Gradients allow unitless zero angles as an exception, see:
+        // https://github.com/w3c/csswg-drafts/issues/1162
+        if let Ok(angle) = input.try_parse(|i| Angle::parse_with_unitless(context, i)) {
+            return Ok(LineDirection::Angle(angle));
+        }
+
+        input.try_parse(|i| {
+            let to_ident = i.try_parse(|i| i.expect_ident_matching("to"));
+            match *compat_mode {
+                // `to` keyword is mandatory in modern syntax.
+                GradientCompatMode::Modern => to_ident?,
+                // Fall back to Modern compatibility mode in case there is a `to` keyword.
+                // According to Gecko, `-moz-linear-gradient(to ...)` should serialize like
+                // `linear-gradient(to ...)`.
+                GradientCompatMode::Moz if to_ident.is_ok() => {
+                    *compat_mode = GradientCompatMode::Modern
+                },
+                // There is no `to` keyword in webkit prefixed syntax. If it's consumed,
+                // parsing should throw an error.
+                GradientCompatMode::WebKit if to_ident.is_ok() => {
+                    return Err(
+                        i.new_custom_error(SelectorParseErrorKind::UnexpectedIdent("to".into()))
+                    );
+                },
+                _ => {},
+            }
+
+            if let Ok(x) = i.try_parse(HorizontalPositionKeyword::parse) {
+                if let Ok(y) = i.try_parse(VerticalPositionKeyword::parse) {
+                    return Ok(LineDirection::Corner(x, y));
+                }
+                return Ok(LineDirection::Horizontal(x));
+            }
+            let y = VerticalPositionKeyword::parse(i)?;
+            if let Ok(x) = i.try_parse(HorizontalPositionKeyword::parse) {
+                return Ok(LineDirection::Corner(x, y));
+            }
+            Ok(LineDirection::Vertical(y))
+        })
+    }
+}
+
+impl EndingShape {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        compat_mode: GradientCompatMode,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(extent) = input.try_parse(|i| ShapeExtent::parse_with_compat_mode(i, compat_mode))
+        {
+            if input
+                .try_parse(|i| i.expect_ident_matching("circle"))
+                .is_ok()
+            {
+                return Ok(generic::EndingShape::Circle(Circle::Extent(extent)));
+            }
+            let _ = input.try_parse(|i| i.expect_ident_matching("ellipse"));
+            return Ok(generic::EndingShape::Ellipse(Ellipse::Extent(extent)));
+        }
+        if input
+            .try_parse(|i| i.expect_ident_matching("circle"))
+            .is_ok()
+        {
+            if let Ok(extent) =
+                input.try_parse(|i| ShapeExtent::parse_with_compat_mode(i, compat_mode))
+            {
+                return Ok(generic::EndingShape::Circle(Circle::Extent(extent)));
+            }
+            if compat_mode == GradientCompatMode::Modern {
+                if let Ok(length) = input.try_parse(|i| NonNegativeLength::parse(context, i)) {
+                    return Ok(generic::EndingShape::Circle(Circle::Radius(length)));
+                }
+            }
+            return Ok(generic::EndingShape::Circle(Circle::Extent(
+                ShapeExtent::FarthestCorner,
+            )));
+        }
+        if input
+            .try_parse(|i| i.expect_ident_matching("ellipse"))
+            .is_ok()
+        {
+            if let Ok(extent) =
+                input.try_parse(|i| ShapeExtent::parse_with_compat_mode(i, compat_mode))
+            {
+                return Ok(generic::EndingShape::Ellipse(Ellipse::Extent(extent)));
+            }
+            if compat_mode == GradientCompatMode::Modern {
+                let pair: Result<_, ParseError> = input.try_parse(|i| {
+                    let x = NonNegativeLengthPercentage::parse(context, i)?;
+                    let y = NonNegativeLengthPercentage::parse(context, i)?;
+                    Ok((x, y))
+                });
+                if let Ok((x, y)) = pair {
+                    return Ok(generic::EndingShape::Ellipse(Ellipse::Radii(x, y)));
+                }
+            }
+            return Ok(generic::EndingShape::Ellipse(Ellipse::Extent(
+                ShapeExtent::FarthestCorner,
+            )));
+        }
+        if let Ok(length) = input.try_parse(|i| NonNegativeLength::parse(context, i)) {
+            if let Ok(y) = input.try_parse(|i| NonNegativeLengthPercentage::parse(context, i)) {
+                if compat_mode == GradientCompatMode::Modern {
+                    let _ = input.try_parse(|i| i.expect_ident_matching("ellipse"));
+                }
+                return Ok(generic::EndingShape::Ellipse(Ellipse::Radii(
+                    NonNegative(LengthPercentage::from(length.0)),
+                    y,
+                )));
+            }
+            if compat_mode == GradientCompatMode::Modern {
+                let y = input.try_parse(|i| {
+                    i.expect_ident_matching("ellipse")?;
+                    NonNegativeLengthPercentage::parse(context, i)
+                });
+                if let Ok(y) = y {
+                    return Ok(generic::EndingShape::Ellipse(Ellipse::Radii(
+                        NonNegative(LengthPercentage::from(length.0)),
+                        y,
+                    )));
+                }
+                let _ = input.try_parse(|i| i.expect_ident_matching("circle"));
+            }
+
+            return Ok(generic::EndingShape::Circle(Circle::Radius(length)));
+        }
+        input.try_parse(|i| {
+            let x = Percentage::parse_non_negative(context, i)?;
+            let y = if let Ok(y) = i.try_parse(|i| NonNegativeLengthPercentage::parse(context, i)) {
+                if compat_mode == GradientCompatMode::Modern {
+                    let _ = i.try_parse(|i| i.expect_ident_matching("ellipse"));
+                }
+                y
+            } else {
+                if compat_mode == GradientCompatMode::Modern {
+                    i.expect_ident_matching("ellipse")?;
+                }
+                NonNegativeLengthPercentage::parse(context, i)?
+            };
+            Ok(generic::EndingShape::Ellipse(Ellipse::Radii(
+                NonNegative(LengthPercentage::from(x)),
+                y,
+            )))
+        })
+    }
+}
+
+impl ShapeExtent {
+    fn parse_with_compat_mode<'i, 't>(
+        input: &mut Parser<'i, 't>,
+        compat_mode: GradientCompatMode,
+    ) -> Result<Self, ParseError<'i>> {
+        match Self::parse(input)? {
+            ShapeExtent::Contain | ShapeExtent::Cover
+                if compat_mode == GradientCompatMode::Modern =>
+            {
+                Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+            },
+            ShapeExtent::Contain => Ok(ShapeExtent::ClosestSide),
+            ShapeExtent::Cover => Ok(ShapeExtent::FarthestCorner),
+            keyword => Ok(keyword),
+        }
+    }
+}
+
+impl<T> generic::GradientItem<Color, T> {
+    fn parse_comma_separated<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        parse_position: impl for<'i1, 't1> Fn(&ParserContext, &mut Parser<'i1, 't1>) -> Result<T, ParseError<'i1>>
+            + Copy,
+    ) -> Result<crate::OwnedSlice<Self>, ParseError<'i>> {
+        let mut items = Vec::new();
+        let mut seen_stop = false;
+
+        loop {
+            input.parse_until_before(Delimiter::Comma, |input| {
+                if seen_stop {
+                    if let Ok(hint) = input.try_parse(|i| parse_position(context, i)) {
+                        seen_stop = false;
+                        items.push(generic::GradientItem::InterpolationHint(hint));
+                        return Ok(());
+                    }
+                }
+
+                let stop = generic::ColorStop::parse(context, input, parse_position)?;
+
+                if let Ok(multi_position) = input.try_parse(|i| parse_position(context, i)) {
+                    let stop_color = stop.color.clone();
+                    items.push(stop.into_item());
+                    items.push(
+                        generic::ColorStop {
+                            color: stop_color,
+                            position: Some(multi_position),
+                        }
+                        .into_item(),
+                    );
+                } else {
+                    items.push(stop.into_item());
+                }
+
+                seen_stop = true;
+                Ok(())
+            })?;
+
+            match input.next() {
+                Err(_) => break,
+                Ok(&Token::Comma) => continue,
+                Ok(_) => unreachable!(),
+            }
+        }
+
+        if !seen_stop || items.len() < 2 {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        Ok(items.into())
+    }
+}
+
+impl<T> generic::ColorStop<Color, T> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        parse_position: impl for<'i1, 't1> Fn(
+            &ParserContext,
+            &mut Parser<'i1, 't1>,
+        ) -> Result<T, ParseError<'i1>>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(generic::ColorStop {
+            color: Color::parse(context, input)?,
+            position: input.try_parse(|i| parse_position(context, i)).ok(),
+        })
+    }
+}
+
+impl Parse for PaintWorklet {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("paint")?;
+        input.parse_nested_block(|input| {
+            let name = Atom::from(&**input.expect_ident()?);
+            let arguments = input
+                .try_parse(|input| {
+                    input.expect_comma()?;
+                    input.parse_comma_separated(|input| SpecifiedValue::parse(input))
+                })
+                .unwrap_or(vec![]);
+            Ok(PaintWorklet { name, arguments })
+        })
+    }
+}
+
+impl MozImageRect {
+    #[cfg(feature = "gecko")]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        cors_mode: CorsMode,
+    ) -> Result<Self, ParseError<'i>> {
+        input.try_parse(|i| i.expect_function_matching("-moz-image-rect"))?;
+        input.parse_nested_block(|i| {
+            let string = i.expect_url_or_string()?;
+            let url = SpecifiedImageUrl::parse_from_string(
+                string.as_ref().to_owned(),
+                context,
+                cors_mode,
+            );
+            i.expect_comma()?;
+            let top = NumberOrPercentage::parse_non_negative(context, i)?;
+            i.expect_comma()?;
+            let right = NumberOrPercentage::parse_non_negative(context, i)?;
+            i.expect_comma()?;
+            let bottom = NumberOrPercentage::parse_non_negative(context, i)?;
+            i.expect_comma()?;
+            let left = NumberOrPercentage::parse_non_negative(context, i)?;
+            Ok(MozImageRect {
+                url,
+                top,
+                right,
+                bottom,
+                left,
+            })
+        })
+    }
+}
+
+/// https://drafts.csswg.org/css-images/#propdef-image-rendering
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum ImageRendering {
+    Auto,
+    Smooth,
+    #[parse(aliases = "-moz-crisp-edges")]
+    CrispEdges,
+    Pixelated,
+    // From the spec:
+    //
+    //     This property previously accepted the values optimizeSpeed and
+    //     optimizeQuality. These are now deprecated; a user agent must accept
+    //     them as valid values but must treat them as having the same behavior
+    //     as crisp-edges and smooth respectively, and authors must not use
+    //     them.
+    //
+    Optimizespeed,
+    Optimizequality,
+}
diff --git a/servo/components/style/values/specified/length.rs b/servo/components/style/values/specified/length.rs
new file mode 100644
index 0000000000..19b6f9bade
--- /dev/null
+++ b/servo/components/style/values/specified/length.rs
@@ -0,0 +1,1841 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! [Length values][length].
+//!
+//! [length]: https://drafts.csswg.org/css-values/#lengths
+
+use super::{AllowQuirks, Number, Percentage, ToComputedValue};
+use crate::font_metrics::{FontMetrics, FontMetricsOrientation};
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::{self, CSSPixelLength, Context};
+use crate::values::generics::length as generics;
+use crate::values::generics::length::{
+    GenericLengthOrNumber, GenericLengthPercentageOrNormal, GenericMaxSize, GenericSize,
+};
+use crate::values::generics::NonNegative;
+use crate::values::specified::calc::{self, CalcNode};
+use crate::values::specified::NonNegativeNumber;
+use crate::values::CSSFloat;
+use crate::{Zero, ZeroNoPercent};
+use app_units::Au;
+use cssparser::{Parser, Token};
+use std::cmp;
+use std::ops::{Add, Mul, Sub};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{ParseError, SpecifiedValueInfo, StyleParseErrorKind};
+
+pub use super::image::Image;
+pub use super::image::{EndingShape as GradientEndingShape, Gradient};
+pub use crate::values::specified::calc::CalcLengthPercentage;
+
+/// Number of pixels per inch
+pub const PX_PER_IN: CSSFloat = 96.;
+/// Number of pixels per centimeter
+pub const PX_PER_CM: CSSFloat = PX_PER_IN / 2.54;
+/// Number of pixels per millimeter
+pub const PX_PER_MM: CSSFloat = PX_PER_IN / 25.4;
+/// Number of pixels per quarter
+pub const PX_PER_Q: CSSFloat = PX_PER_MM / 4.;
+/// Number of pixels per point
+pub const PX_PER_PT: CSSFloat = PX_PER_IN / 72.;
+/// Number of pixels per pica
+pub const PX_PER_PC: CSSFloat = PX_PER_PT * 12.;
+
+/// A font relative length.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+pub enum FontRelativeLength {
+    /// A "em" value: https://drafts.csswg.org/css-values/#em
+    #[css(dimension)]
+    Em(CSSFloat),
+    /// A "ex" value: https://drafts.csswg.org/css-values/#ex
+    #[css(dimension)]
+    Ex(CSSFloat),
+    /// A "ch" value: https://drafts.csswg.org/css-values/#ch
+    #[css(dimension)]
+    Ch(CSSFloat),
+    /// A "cap" value: https://drafts.csswg.org/css-values/#cap
+    #[css(dimension)]
+    Cap(CSSFloat),
+    /// An "ic" value: https://drafts.csswg.org/css-values/#ic
+    #[css(dimension)]
+    Ic(CSSFloat),
+    /// A "rem" value: https://drafts.csswg.org/css-values/#rem
+    #[css(dimension)]
+    Rem(CSSFloat),
+}
+
+/// A source to resolve font-relative units against
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum FontBaseSize {
+    /// Use the font-size of the current element.
+    CurrentStyle,
+    /// Use the inherited font-size.
+    InheritedStyle,
+}
+
+impl FontBaseSize {
+    /// Calculate the actual size for a given context
+    pub fn resolve(&self, context: &Context) -> computed::FontSize {
+        match *self {
+            FontBaseSize::CurrentStyle => context.style().get_font().clone_font_size(),
+            FontBaseSize::InheritedStyle => context.style().get_parent_font().clone_font_size(),
+        }
+    }
+}
+
+impl FontRelativeLength {
+    /// Return the unitless, raw value.
+    fn unitless_value(&self) -> CSSFloat {
+        match *self {
+            FontRelativeLength::Em(v) |
+            FontRelativeLength::Ex(v) |
+            FontRelativeLength::Ch(v) |
+            FontRelativeLength::Cap(v) |
+            FontRelativeLength::Ic(v) |
+            FontRelativeLength::Rem(v) => v,
+        }
+    }
+
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        use self::FontRelativeLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        Ok(match (self, other) {
+            (&Em(one), &Em(other)) => Em(op(one, other)),
+            (&Ex(one), &Ex(other)) => Ex(op(one, other)),
+            (&Ch(one), &Ch(other)) => Ch(op(one, other)),
+            (&Cap(one), &Cap(other)) => Cap(op(one, other)),
+            (&Ic(one), &Ic(other)) => Ic(op(one, other)),
+            (&Rem(one), &Rem(other)) => Rem(op(one, other)),
+            // See https://github.com/rust-lang/rust/issues/68867. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Em(..) | Ex(..) | Ch(..) | Cap(..) | Ic(..) | Rem(..) => {},
+                }
+                debug_unreachable!("Forgot to handle unit in try_op()")
+            },
+        })
+    }
+
+    /// Computes the font-relative length.
+    pub fn to_computed_value(
+        &self,
+        context: &Context,
+        base_size: FontBaseSize,
+    ) -> computed::Length {
+        let (reference_size, length) = self.reference_font_size_and_length(context, base_size);
+        (reference_size * length).normalized()
+    }
+
+    /// Return reference font size.
+    ///
+    /// We use the base_size flag to pass a different size for computing
+    /// font-size and unconstrained font-size.
+    ///
+    /// This returns a pair, the first one is the reference font size, and the
+    /// second one is the unpacked relative length.
+    fn reference_font_size_and_length(
+        &self,
+        context: &Context,
+        base_size: FontBaseSize,
+    ) -> (computed::Length, CSSFloat) {
+        fn query_font_metrics(
+            context: &Context,
+            base_size: FontBaseSize,
+            orientation: FontMetricsOrientation,
+        ) -> FontMetrics {
+            let retrieve_math_scales = false;
+            context.query_font_metrics(base_size, orientation, retrieve_math_scales)
+        }
+
+        let reference_font_size = base_size.resolve(context);
+        match *self {
+            FontRelativeLength::Em(length) => {
+                if context.for_non_inherited_property.is_some() {
+                    if base_size == FontBaseSize::CurrentStyle {
+                        context
+                            .rule_cache_conditions
+                            .borrow_mut()
+                            .set_font_size_dependency(reference_font_size.computed_size);
+                    }
+                }
+
+                (reference_font_size.computed_size(), length)
+            },
+            FontRelativeLength::Ex(length) => {
+                // The x-height is an intrinsically horizontal metric.
+                let metrics =
+                    query_font_metrics(context, base_size, FontMetricsOrientation::Horizontal);
+                let reference_size = metrics.x_height.unwrap_or_else(|| {
+                    // https://drafts.csswg.org/css-values/#ex
+                    //
+                    //     In the cases where it is impossible or impractical to
+                    //     determine the x-height, a value of 0.5em must be
+                    //     assumed.
+                    //
+                    // (But note we use 0.5em of the used, not computed
+                    // font-size)
+                    reference_font_size.used_size() * 0.5
+                });
+                (reference_size, length)
+            },
+            FontRelativeLength::Ch(length) => {
+                // https://drafts.csswg.org/css-values/#ch:
+                //
+                //     Equal to the used advance measure of the “0” (ZERO,
+                //     U+0030) glyph in the font used to render it. (The advance
+                //     measure of a glyph is its advance width or height,
+                //     whichever is in the inline axis of the element.)
+                //
+                let metrics = query_font_metrics(
+                    context,
+                    base_size,
+                    FontMetricsOrientation::MatchContextPreferHorizontal,
+                );
+                let reference_size = metrics.zero_advance_measure.unwrap_or_else(|| {
+                    // https://drafts.csswg.org/css-values/#ch
+                    //
+                    //     In the cases where it is impossible or impractical to
+                    //     determine the measure of the “0” glyph, it must be
+                    //     assumed to be 0.5em wide by 1em tall. Thus, the ch
+                    //     unit falls back to 0.5em in the general case, and to
+                    //     1em when it would be typeset upright (i.e.
+                    //     writing-mode is vertical-rl or vertical-lr and
+                    //     text-orientation is upright).
+                    //
+                    // Same caveat about computed vs. used font-size applies
+                    // above.
+                    let wm = context.style().writing_mode;
+                    if wm.is_vertical() && wm.is_upright() {
+                        reference_font_size.used_size()
+                    } else {
+                        reference_font_size.used_size() * 0.5
+                    }
+                });
+                (reference_size, length)
+            },
+            FontRelativeLength::Cap(length) => {
+                let metrics =
+                    query_font_metrics(context, base_size, FontMetricsOrientation::Horizontal);
+                let reference_size = metrics.cap_height.unwrap_or_else(|| {
+                    // https://drafts.csswg.org/css-values/#cap
+                    //
+                    //     In the cases where it is impossible or impractical to
+                    //     determine the cap-height, the font’s ascent must be
+                    //     used.
+                    //
+                    metrics.ascent
+                });
+                (reference_size, length)
+            },
+            FontRelativeLength::Ic(length) => {
+                let metrics = query_font_metrics(
+                    context,
+                    base_size,
+                    FontMetricsOrientation::MatchContextPreferVertical,
+                );
+                let reference_size = metrics.ic_width.unwrap_or_else(|| {
+                    // https://drafts.csswg.org/css-values/#ic
+                    //
+                    //     In the cases where it is impossible or impractical to
+                    //     determine the ideographic advance measure, it must be
+                    //     assumed to be 1em.
+                    //
+                    // Same caveat about computed vs. used as for other
+                    // metric-dependent units.
+                    reference_font_size.used_size()
+                });
+                (reference_size, length)
+            },
+            FontRelativeLength::Rem(length) => {
+                // https://drafts.csswg.org/css-values/#rem:
+                //
+                //     When specified on the font-size property of the root
+                //     element, the rem units refer to the property's initial
+                //     value.
+                //
+                let reference_size = if context.builder.is_root_element || context.in_media_query {
+                    reference_font_size.computed_size()
+                } else {
+                    context.device().root_font_size()
+                };
+                (reference_size, length)
+            },
+        }
+    }
+}
+
+/// https://drafts.csswg.org/css-values/#viewport-variants
+pub enum ViewportVariant {
+    /// https://drafts.csswg.org/css-values/#ua-default-viewport-size
+    UADefault,
+    /// https://drafts.csswg.org/css-values/#small-viewport-percentage-units
+    Small,
+    /// https://drafts.csswg.org/css-values/#large-viewport-percentage-units
+    Large,
+    /// https://drafts.csswg.org/css-values/#dynamic-viewport-percentage-units
+    Dynamic,
+}
+
+/// https://drafts.csswg.org/css-values/#viewport-relative-units
+#[derive(PartialEq)]
+enum ViewportUnit {
+    /// *vw units.
+    Vw,
+    /// *vh units.
+    Vh,
+    /// *vmin units.
+    Vmin,
+    /// *vmax units.
+    Vmax,
+    /// *vb units.
+    Vb,
+    /// *vi units.
+    Vi,
+}
+
+/// A viewport-relative length.
+///
+/// <https://drafts.csswg.org/css-values/#viewport-relative-lengths>
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+pub enum ViewportPercentageLength {
+    /// <https://drafts.csswg.org/css-values/#valdef-length-vw>
+    #[css(dimension)]
+    Vw(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-svw>
+    #[css(dimension)]
+    Svw(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-lvw>
+    #[css(dimension)]
+    Lvw(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-dvw>
+    #[css(dimension)]
+    Dvw(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-vh>
+    #[css(dimension)]
+    Vh(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-svh>
+    #[css(dimension)]
+    Svh(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-lvh>
+    #[css(dimension)]
+    Lvh(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-dvh>
+    #[css(dimension)]
+    Dvh(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-vmin>
+    #[css(dimension)]
+    Vmin(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-svmin>
+    #[css(dimension)]
+    Svmin(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-lvmin>
+    #[css(dimension)]
+    Lvmin(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-dvmin>
+    #[css(dimension)]
+    Dvmin(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-vmax>
+    #[css(dimension)]
+    Vmax(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-svmax>
+    #[css(dimension)]
+    Svmax(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-lvmax>
+    #[css(dimension)]
+    Lvmax(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-dvmax>
+    #[css(dimension)]
+    Dvmax(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-vb>
+    #[css(dimension)]
+    Vb(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-svb>
+    #[css(dimension)]
+    Svb(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-lvb>
+    #[css(dimension)]
+    Lvb(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-dvb>
+    #[css(dimension)]
+    Dvb(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-vi>
+    #[css(dimension)]
+    Vi(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-svi>
+    #[css(dimension)]
+    Svi(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-lvi>
+    #[css(dimension)]
+    Lvi(CSSFloat),
+    /// <https://drafts.csswg.org/css-values/#valdef-length-dvi>
+    #[css(dimension)]
+    Dvi(CSSFloat),
+}
+
+impl ViewportPercentageLength {
+    /// Return the unitless, raw value.
+    fn unitless_value(&self) -> CSSFloat {
+        self.unpack().2
+    }
+
+    fn unpack(&self) -> (ViewportVariant, ViewportUnit, CSSFloat) {
+        match *self {
+            ViewportPercentageLength::Vw(v) => (ViewportVariant::UADefault, ViewportUnit::Vw, v),
+            ViewportPercentageLength::Svw(v) => (ViewportVariant::Small, ViewportUnit::Vw, v),
+            ViewportPercentageLength::Lvw(v) => (ViewportVariant::Large, ViewportUnit::Vw, v),
+            ViewportPercentageLength::Dvw(v) => (ViewportVariant::Dynamic, ViewportUnit::Vw, v),
+            ViewportPercentageLength::Vh(v) => (ViewportVariant::UADefault, ViewportUnit::Vh, v),
+            ViewportPercentageLength::Svh(v) => (ViewportVariant::Small, ViewportUnit::Vh, v),
+            ViewportPercentageLength::Lvh(v) => (ViewportVariant::Large, ViewportUnit::Vh, v),
+            ViewportPercentageLength::Dvh(v) => (ViewportVariant::Dynamic, ViewportUnit::Vh, v),
+            ViewportPercentageLength::Vmin(v) => {
+                (ViewportVariant::UADefault, ViewportUnit::Vmin, v)
+            },
+            ViewportPercentageLength::Svmin(v) => (ViewportVariant::Small, ViewportUnit::Vmin, v),
+            ViewportPercentageLength::Lvmin(v) => (ViewportVariant::Large, ViewportUnit::Vmin, v),
+            ViewportPercentageLength::Dvmin(v) => (ViewportVariant::Dynamic, ViewportUnit::Vmin, v),
+            ViewportPercentageLength::Vmax(v) => {
+                (ViewportVariant::UADefault, ViewportUnit::Vmax, v)
+            },
+            ViewportPercentageLength::Svmax(v) => (ViewportVariant::Small, ViewportUnit::Vmax, v),
+            ViewportPercentageLength::Lvmax(v) => (ViewportVariant::Large, ViewportUnit::Vmax, v),
+            ViewportPercentageLength::Dvmax(v) => (ViewportVariant::Dynamic, ViewportUnit::Vmax, v),
+            ViewportPercentageLength::Vb(v) => (ViewportVariant::UADefault, ViewportUnit::Vb, v),
+            ViewportPercentageLength::Svb(v) => (ViewportVariant::Small, ViewportUnit::Vb, v),
+            ViewportPercentageLength::Lvb(v) => (ViewportVariant::Large, ViewportUnit::Vb, v),
+            ViewportPercentageLength::Dvb(v) => (ViewportVariant::Dynamic, ViewportUnit::Vb, v),
+            ViewportPercentageLength::Vi(v) => (ViewportVariant::UADefault, ViewportUnit::Vi, v),
+            ViewportPercentageLength::Svi(v) => (ViewportVariant::Small, ViewportUnit::Vi, v),
+            ViewportPercentageLength::Lvi(v) => (ViewportVariant::Large, ViewportUnit::Vi, v),
+            ViewportPercentageLength::Dvi(v) => (ViewportVariant::Dynamic, ViewportUnit::Vi, v),
+        }
+    }
+
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        use self::ViewportPercentageLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        Ok(match (self, other) {
+            (&Vw(one), &Vw(other)) => Vw(op(one, other)),
+            (&Svw(one), &Svw(other)) => Svw(op(one, other)),
+            (&Lvw(one), &Lvw(other)) => Lvw(op(one, other)),
+            (&Dvw(one), &Dvw(other)) => Dvw(op(one, other)),
+            (&Vh(one), &Vh(other)) => Vh(op(one, other)),
+            (&Svh(one), &Svh(other)) => Svh(op(one, other)),
+            (&Lvh(one), &Lvh(other)) => Lvh(op(one, other)),
+            (&Dvh(one), &Dvh(other)) => Dvh(op(one, other)),
+            (&Vmin(one), &Vmin(other)) => Vmin(op(one, other)),
+            (&Svmin(one), &Svmin(other)) => Svmin(op(one, other)),
+            (&Lvmin(one), &Lvmin(other)) => Lvmin(op(one, other)),
+            (&Dvmin(one), &Dvmin(other)) => Dvmin(op(one, other)),
+            (&Vmax(one), &Vmax(other)) => Vmax(op(one, other)),
+            (&Svmax(one), &Svmax(other)) => Svmax(op(one, other)),
+            (&Lvmax(one), &Lvmax(other)) => Lvmax(op(one, other)),
+            (&Dvmax(one), &Dvmax(other)) => Dvmax(op(one, other)),
+            (&Vb(one), &Vb(other)) => Vb(op(one, other)),
+            (&Svb(one), &Svb(other)) => Svb(op(one, other)),
+            (&Lvb(one), &Lvb(other)) => Lvb(op(one, other)),
+            (&Dvb(one), &Dvb(other)) => Dvb(op(one, other)),
+            (&Vi(one), &Vi(other)) => Vi(op(one, other)),
+            (&Svi(one), &Svi(other)) => Svi(op(one, other)),
+            (&Lvi(one), &Lvi(other)) => Lvi(op(one, other)),
+            (&Dvi(one), &Dvi(other)) => Dvi(op(one, other)),
+            // See https://github.com/rust-lang/rust/issues/68867. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Vw(..) | Svw(..) | Lvw(..) | Dvw(..) | Vh(..) | Svh(..) | Lvh(..) |
+                    Dvh(..) | Vmin(..) | Svmin(..) | Lvmin(..) | Dvmin(..) | Vmax(..) |
+                    Svmax(..) | Lvmax(..) | Dvmax(..) | Vb(..) | Svb(..) | Lvb(..) | Dvb(..) |
+                    Vi(..) | Svi(..) | Lvi(..) | Dvi(..) => {},
+                }
+                debug_unreachable!("Forgot to handle unit in try_op()")
+            },
+        })
+    }
+
+    /// Computes the given viewport-relative length for the given viewport size.
+    pub fn to_computed_value(&self, context: &Context) -> CSSPixelLength {
+        let (variant, unit, factor) = self.unpack();
+        let size = context.viewport_size_for_viewport_unit_resolution(variant);
+        let length = match unit {
+            ViewportUnit::Vw => size.width,
+            ViewportUnit::Vh => size.height,
+            ViewportUnit::Vmin => cmp::min(size.width, size.height),
+            ViewportUnit::Vmax => cmp::max(size.width, size.height),
+            ViewportUnit::Vi | ViewportUnit::Vb => {
+                context
+                    .rule_cache_conditions
+                    .borrow_mut()
+                    .set_writing_mode_dependency(context.builder.writing_mode);
+                if (unit == ViewportUnit::Vb) == context.style().writing_mode.is_vertical() {
+                    size.width
+                } else {
+                    size.height
+                }
+            },
+        };
+
+        // FIXME: Bug 1396535, we need to fix the extremely small viewport length for transform.
+        // See bug 989802. We truncate so that adding multiple viewport units
+        // that add up to 100 does not overflow due to rounding differences
+        let trunc_scaled = ((length.0 as f64) * factor as f64 / 100.).trunc();
+        Au::from_f64_au(trunc_scaled).into()
+    }
+}
+
+/// HTML5 "character width", as defined in HTML5 § 14.5.4.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+pub struct CharacterWidth(pub i32);
+
+impl CharacterWidth {
+    /// Computes the given character width.
+    pub fn to_computed_value(&self, reference_font_size: computed::Length) -> computed::Length {
+        // This applies the *converting a character width to pixels* algorithm
+        // as specified in HTML5 § 14.5.4.
+        //
+        // TODO(pcwalton): Find these from the font.
+        let average_advance = reference_font_size * 0.5;
+        let max_advance = reference_font_size;
+        average_advance * (self.0 as CSSFloat - 1.0) + max_advance
+    }
+}
+
+/// Represents an absolute length with its unit
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+pub enum AbsoluteLength {
+    /// An absolute length in pixels (px)
+    #[css(dimension)]
+    Px(CSSFloat),
+    /// An absolute length in inches (in)
+    #[css(dimension)]
+    In(CSSFloat),
+    /// An absolute length in centimeters (cm)
+    #[css(dimension)]
+    Cm(CSSFloat),
+    /// An absolute length in millimeters (mm)
+    #[css(dimension)]
+    Mm(CSSFloat),
+    /// An absolute length in quarter-millimeters (q)
+    #[css(dimension)]
+    Q(CSSFloat),
+    /// An absolute length in points (pt)
+    #[css(dimension)]
+    Pt(CSSFloat),
+    /// An absolute length in pica (pc)
+    #[css(dimension)]
+    Pc(CSSFloat),
+}
+
+impl AbsoluteLength {
+    /// Return the unitless, raw value.
+    fn unitless_value(&self) -> CSSFloat {
+        match *self {
+            AbsoluteLength::Px(v) |
+            AbsoluteLength::In(v) |
+            AbsoluteLength::Cm(v) |
+            AbsoluteLength::Mm(v) |
+            AbsoluteLength::Q(v) |
+            AbsoluteLength::Pt(v) |
+            AbsoluteLength::Pc(v) => v,
+        }
+    }
+
+    /// Convert this into a pixel value.
+    #[inline]
+    pub fn to_px(&self) -> CSSFloat {
+        use std::f32;
+
+        let pixel = match *self {
+            AbsoluteLength::Px(value) => value,
+            AbsoluteLength::In(value) => value * PX_PER_IN,
+            AbsoluteLength::Cm(value) => value * PX_PER_CM,
+            AbsoluteLength::Mm(value) => value * PX_PER_MM,
+            AbsoluteLength::Q(value) => value * PX_PER_Q,
+            AbsoluteLength::Pt(value) => value * PX_PER_PT,
+            AbsoluteLength::Pc(value) => value * PX_PER_PC,
+        };
+        pixel.min(f32::MAX).max(f32::MIN)
+    }
+
+    fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        Ok(match (self, other) {
+            (AbsoluteLength::Px(x), AbsoluteLength::Px(y)) => AbsoluteLength::Px(op(*x, *y)),
+            (AbsoluteLength::In(x), AbsoluteLength::In(y)) => AbsoluteLength::In(op(*x, *y)),
+            (AbsoluteLength::Cm(x), AbsoluteLength::Cm(y)) => AbsoluteLength::Cm(op(*x, *y)),
+            (AbsoluteLength::Mm(x), AbsoluteLength::Mm(y)) => AbsoluteLength::Mm(op(*x, *y)),
+            (AbsoluteLength::Q(x), AbsoluteLength::Q(y)) => AbsoluteLength::Q(op(*x, *y)),
+            (AbsoluteLength::Pt(x), AbsoluteLength::Pt(y)) => AbsoluteLength::Pt(op(*x, *y)),
+            (AbsoluteLength::Pc(x), AbsoluteLength::Pc(y)) => AbsoluteLength::Pc(op(*x, *y)),
+            _ => AbsoluteLength::Px(op(self.to_px(), other.to_px())),
+        })
+    }
+}
+
+impl ToComputedValue for AbsoluteLength {
+    type ComputedValue = CSSPixelLength;
+
+    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
+        CSSPixelLength::new(self.to_px())
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        AbsoluteLength::Px(computed.px())
+    }
+}
+
+impl PartialOrd for AbsoluteLength {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        self.to_px().partial_cmp(&other.to_px())
+    }
+}
+
+impl Mul<CSSFloat> for AbsoluteLength {
+    type Output = AbsoluteLength;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> AbsoluteLength {
+        match self {
+            AbsoluteLength::Px(v) => AbsoluteLength::Px(v * scalar),
+            AbsoluteLength::In(v) => AbsoluteLength::In(v * scalar),
+            AbsoluteLength::Cm(v) => AbsoluteLength::Cm(v * scalar),
+            AbsoluteLength::Mm(v) => AbsoluteLength::Mm(v * scalar),
+            AbsoluteLength::Q(v) => AbsoluteLength::Q(v * scalar),
+            AbsoluteLength::Pt(v) => AbsoluteLength::Pt(v * scalar),
+            AbsoluteLength::Pc(v) => AbsoluteLength::Pc(v * scalar),
+        }
+    }
+}
+
+impl Add<AbsoluteLength> for AbsoluteLength {
+    type Output = Self;
+
+    #[inline]
+    fn add(self, rhs: Self) -> Self {
+        match (self, rhs) {
+            (AbsoluteLength::Px(x), AbsoluteLength::Px(y)) => AbsoluteLength::Px(x + y),
+            (AbsoluteLength::In(x), AbsoluteLength::In(y)) => AbsoluteLength::In(x + y),
+            (AbsoluteLength::Cm(x), AbsoluteLength::Cm(y)) => AbsoluteLength::Cm(x + y),
+            (AbsoluteLength::Mm(x), AbsoluteLength::Mm(y)) => AbsoluteLength::Mm(x + y),
+            (AbsoluteLength::Q(x), AbsoluteLength::Q(y)) => AbsoluteLength::Q(x + y),
+            (AbsoluteLength::Pt(x), AbsoluteLength::Pt(y)) => AbsoluteLength::Pt(x + y),
+            (AbsoluteLength::Pc(x), AbsoluteLength::Pc(y)) => AbsoluteLength::Pc(x + y),
+            _ => AbsoluteLength::Px(self.to_px() + rhs.to_px()),
+        }
+    }
+}
+
+/// A container query length.
+///
+/// <https://drafts.csswg.org/css-contain-3/#container-lengths>
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+pub enum ContainerRelativeLength {
+    /// 1% of query container's width
+    #[css(dimension)]
+    Cqw(CSSFloat),
+    /// 1% of query container's height
+    #[css(dimension)]
+    Cqh(CSSFloat),
+    /// 1% of query container's inline size
+    #[css(dimension)]
+    Cqi(CSSFloat),
+    /// 1% of query container's block size
+    #[css(dimension)]
+    Cqb(CSSFloat),
+    /// The smaller value of `cqi` or `cqb`
+    #[css(dimension)]
+    Cqmin(CSSFloat),
+    /// The larger value of `cqi` or `cqb`
+    #[css(dimension)]
+    Cqmax(CSSFloat),
+}
+
+impl ContainerRelativeLength {
+    fn unitless_value(&self) -> CSSFloat {
+        match *self {
+            ContainerRelativeLength::Cqw(v) |
+            ContainerRelativeLength::Cqh(v) |
+            ContainerRelativeLength::Cqi(v) |
+            ContainerRelativeLength::Cqb(v) |
+            ContainerRelativeLength::Cqmin(v) |
+            ContainerRelativeLength::Cqmax(v) => v,
+        }
+    }
+
+    pub(crate) fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        use self::ContainerRelativeLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        Ok(match (self, other) {
+            (&Cqw(one), &Cqw(other)) => Cqw(op(one, other)),
+            (&Cqh(one), &Cqh(other)) => Cqh(op(one, other)),
+            (&Cqi(one), &Cqi(other)) => Cqi(op(one, other)),
+            (&Cqb(one), &Cqb(other)) => Cqb(op(one, other)),
+            (&Cqmin(one), &Cqmin(other)) => Cqmin(op(one, other)),
+            (&Cqmax(one), &Cqmax(other)) => Cqmax(op(one, other)),
+
+            // See https://github.com/rust-lang/rust/issues/68867, then
+            // https://github.com/rust-lang/rust/pull/95161. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Cqw(..) | Cqh(..) | Cqi(..) | Cqb(..) | Cqmin(..) | Cqmax(..) => {},
+                }
+                debug_unreachable!("Forgot to handle unit in try_op()")
+            },
+        })
+    }
+
+    /// Computes the given container-relative length.
+    pub fn to_computed_value(&self, context: &Context) -> CSSPixelLength {
+        let size = context.get_container_size_query();
+        let (factor, container_length) = match *self {
+            ContainerRelativeLength::Cqw(v) => (v, size.get_container_width(context)),
+            ContainerRelativeLength::Cqh(v) => (v, size.get_container_height(context)),
+            ContainerRelativeLength::Cqi(v) => (v, size.get_container_inline_size(context)),
+            ContainerRelativeLength::Cqb(v) => (v, size.get_container_block_size(context)),
+            ContainerRelativeLength::Cqmin(v) => (
+                v,
+                cmp::min(
+                    size.get_container_inline_size(context),
+                    size.get_container_block_size(context),
+                ),
+            ),
+            ContainerRelativeLength::Cqmax(v) => (
+                v,
+                cmp::max(
+                    size.get_container_inline_size(context),
+                    size.get_container_block_size(context),
+                ),
+            ),
+        };
+        CSSPixelLength::new(((container_length.to_f64_px()) * factor as f64 / 100.0) as f32)
+    }
+}
+
+#[cfg(feature = "gecko")]
+fn are_container_queries_enabled() -> bool {
+    static_prefs::pref!("layout.css.container-queries.enabled")
+}
+#[cfg(feature = "servo")]
+fn are_container_queries_enabled() -> bool {
+    false
+}
+
+impl Sub<AbsoluteLength> for AbsoluteLength {
+    type Output = Self;
+
+    #[inline]
+    fn sub(self, rhs: Self) -> Self {
+        match (self, rhs) {
+            (AbsoluteLength::Px(x), AbsoluteLength::Px(y)) => AbsoluteLength::Px(x - y),
+            (AbsoluteLength::In(x), AbsoluteLength::In(y)) => AbsoluteLength::In(x - y),
+            (AbsoluteLength::Cm(x), AbsoluteLength::Cm(y)) => AbsoluteLength::Cm(x - y),
+            (AbsoluteLength::Mm(x), AbsoluteLength::Mm(y)) => AbsoluteLength::Mm(x - y),
+            (AbsoluteLength::Q(x), AbsoluteLength::Q(y)) => AbsoluteLength::Q(x - y),
+            (AbsoluteLength::Pt(x), AbsoluteLength::Pt(y)) => AbsoluteLength::Pt(x - y),
+            (AbsoluteLength::Pc(x), AbsoluteLength::Pc(y)) => AbsoluteLength::Pc(x - y),
+            _ => AbsoluteLength::Px(self.to_px() - rhs.to_px()),
+        }
+    }
+}
+
+/// A `<length>` without taking `calc` expressions into account
+///
+/// <https://drafts.csswg.org/css-values/#lengths>
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToCss, ToShmem)]
+pub enum NoCalcLength {
+    /// An absolute length
+    ///
+    /// <https://drafts.csswg.org/css-values/#absolute-length>
+    Absolute(AbsoluteLength),
+
+    /// A font-relative length:
+    ///
+    /// <https://drafts.csswg.org/css-values/#font-relative-lengths>
+    FontRelative(FontRelativeLength),
+
+    /// A viewport-relative length.
+    ///
+    /// <https://drafts.csswg.org/css-values/#viewport-relative-lengths>
+    ViewportPercentage(ViewportPercentageLength),
+
+    /// A container query length.
+    ///
+    /// <https://drafts.csswg.org/css-contain-3/#container-lengths>
+    ContainerRelative(ContainerRelativeLength),
+    /// HTML5 "character width", as defined in HTML5 § 14.5.4.
+    ///
+    /// This cannot be specified by the user directly and is only generated by
+    /// `Stylist::synthesize_rules_for_legacy_attributes()`.
+    #[css(function)]
+    ServoCharacterWidth(CharacterWidth),
+}
+
+impl Mul<CSSFloat> for NoCalcLength {
+    type Output = NoCalcLength;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> NoCalcLength {
+        match self {
+            NoCalcLength::Absolute(v) => NoCalcLength::Absolute(v * scalar),
+            NoCalcLength::FontRelative(v) => NoCalcLength::FontRelative(v * scalar),
+            NoCalcLength::ViewportPercentage(v) => NoCalcLength::ViewportPercentage(v * scalar),
+            NoCalcLength::ContainerRelative(v) => NoCalcLength::ContainerRelative(v * scalar),
+            NoCalcLength::ServoCharacterWidth(_) => panic!("Can't multiply ServoCharacterWidth!"),
+        }
+    }
+}
+
+impl NoCalcLength {
+    /// Return the unitless, raw value.
+    pub fn unitless_value(&self) -> CSSFloat {
+        match *self {
+            NoCalcLength::Absolute(v) => v.unitless_value(),
+            NoCalcLength::FontRelative(v) => v.unitless_value(),
+            NoCalcLength::ViewportPercentage(v) => v.unitless_value(),
+            NoCalcLength::ContainerRelative(v) => v.unitless_value(),
+            NoCalcLength::ServoCharacterWidth(c) => c.0 as f32,
+        }
+    }
+
+    /// Returns whether the value of this length without unit is less than zero.
+    pub fn is_negative(&self) -> bool {
+        self.unitless_value().is_sign_negative()
+    }
+
+    /// Returns whether the value of this length without unit is equal to zero.
+    pub fn is_zero(&self) -> bool {
+        self.unitless_value() == 0.0
+    }
+
+    /// Returns whether the value of this length without unit is infinite.
+    pub fn is_infinite(&self) -> bool {
+        self.unitless_value().is_infinite()
+    }
+
+    /// Returns whether the value of this length without unit is NaN.
+    pub fn is_nan(&self) -> bool {
+        self.unitless_value().is_nan()
+    }
+
+    /// Whether text-only zoom should be applied to this length.
+    ///
+    /// Generally, font-dependent/relative units don't get text-only-zoomed,
+    /// because the font they're relative to should be zoomed already.
+    pub fn should_zoom_text(&self) -> bool {
+        match *self {
+            Self::Absolute(..) |
+            Self::ViewportPercentage(..) |
+            Self::ContainerRelative(..) => true,
+            Self::ServoCharacterWidth(..) |
+            Self::FontRelative(..) => false,
+        }
+    }
+
+    /// Parse a given absolute or relative dimension.
+    pub fn parse_dimension(
+        context: &ParserContext,
+        value: CSSFloat,
+        unit: &str,
+    ) -> Result<Self, ()> {
+        Ok(match_ignore_ascii_case! { unit,
+            "px" => NoCalcLength::Absolute(AbsoluteLength::Px(value)),
+            "in" => NoCalcLength::Absolute(AbsoluteLength::In(value)),
+            "cm" => NoCalcLength::Absolute(AbsoluteLength::Cm(value)),
+            "mm" => NoCalcLength::Absolute(AbsoluteLength::Mm(value)),
+            "q" => NoCalcLength::Absolute(AbsoluteLength::Q(value)),
+            "pt" => NoCalcLength::Absolute(AbsoluteLength::Pt(value)),
+            "pc" => NoCalcLength::Absolute(AbsoluteLength::Pc(value)),
+            // font-relative
+            "em" => NoCalcLength::FontRelative(FontRelativeLength::Em(value)),
+            "ex" => NoCalcLength::FontRelative(FontRelativeLength::Ex(value)),
+            "ch" => NoCalcLength::FontRelative(FontRelativeLength::Ch(value)),
+            "cap" => NoCalcLength::FontRelative(FontRelativeLength::Cap(value)),
+            "ic" => NoCalcLength::FontRelative(FontRelativeLength::Ic(value)),
+            "rem" => NoCalcLength::FontRelative(FontRelativeLength::Rem(value)),
+            // viewport percentages
+            "vw" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Vw(value))
+            },
+            "svw" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Svw(value))
+            },
+            "lvw" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Lvw(value))
+            },
+            "dvw" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Dvw(value))
+            },
+            "vh" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Vh(value))
+            },
+            "svh" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Svh(value))
+            },
+            "lvh" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Lvh(value))
+            },
+            "dvh" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Dvh(value))
+            },
+            "vmin" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Vmin(value))
+            },
+            "svmin" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Svmin(value))
+            },
+            "lvmin" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Lvmin(value))
+            },
+            "dvmin" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Dvmin(value))
+            },
+            "vmax" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Vmax(value))
+            },
+            "svmax" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Svmax(value))
+            },
+            "lvmax" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Lvmax(value))
+            },
+            "dvmax" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Dvmax(value))
+            },
+            "vb" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Vb(value))
+            },
+            "svb" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Svb(value))
+            },
+            "lvb" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Lvb(value))
+            },
+            "dvb" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Dvb(value))
+            },
+            "vi" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Vi(value))
+            },
+            "svi" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Svi(value))
+            },
+            "lvi" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Lvi(value))
+            },
+            "dvi" if !context.in_page_rule() => {
+                NoCalcLength::ViewportPercentage(ViewportPercentageLength::Dvi(value))
+            },
+            // Container query lengths. Inherit the limitation from viewport units since
+            // we may fall back to them.
+            "cqw" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqw(value))
+            },
+            "cqh" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqh(value))
+            },
+            "cqi" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqi(value))
+            },
+            "cqb" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqb(value))
+            },
+            "cqmin" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqmin(value))
+            },
+            "cqmax" if !context.in_page_rule() && are_container_queries_enabled() => {
+                NoCalcLength::ContainerRelative(ContainerRelativeLength::Cqmax(value))
+            },
+            _ => return Err(()),
+        })
+    }
+
+    pub(crate) fn try_op<O>(&self, other: &Self, op: O) -> Result<Self, ()>
+    where
+        O: Fn(f32, f32) -> f32,
+    {
+        use self::NoCalcLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return Err(());
+        }
+
+        Ok(match (self, other) {
+            (&Absolute(ref one), &Absolute(ref other)) => Absolute(one.try_op(other, op)?),
+            (&FontRelative(ref one), &FontRelative(ref other)) => {
+                FontRelative(one.try_op(other, op)?)
+            },
+            (&ViewportPercentage(ref one), &ViewportPercentage(ref other)) => {
+                ViewportPercentage(one.try_op(other, op)?)
+            },
+            (&ContainerRelative(ref one), &ContainerRelative(ref other)) => {
+                ContainerRelative(one.try_op(other, op)?)
+            },
+            (&ServoCharacterWidth(ref one), &ServoCharacterWidth(ref other)) => {
+                ServoCharacterWidth(CharacterWidth(op(one.0 as f32, other.0 as f32) as i32))
+            },
+            // See https://github.com/rust-lang/rust/issues/68867. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Absolute(..) |
+                    FontRelative(..) |
+                    ViewportPercentage(..) |
+                    ContainerRelative(..) |
+                    ServoCharacterWidth(..) => {},
+                }
+                debug_unreachable!("Forgot to handle unit in try_op()")
+            },
+        })
+    }
+
+    /// Get a px value without context.
+    #[inline]
+    pub fn to_computed_pixel_length_without_context(&self) -> Result<CSSFloat, ()> {
+        match *self {
+            NoCalcLength::Absolute(len) => Ok(len.to_px()),
+            _ => Err(()),
+        }
+    }
+
+    /// Get an absolute length from a px value.
+    #[inline]
+    pub fn from_px(px_value: CSSFloat) -> NoCalcLength {
+        NoCalcLength::Absolute(AbsoluteLength::Px(px_value))
+    }
+}
+
+impl SpecifiedValueInfo for NoCalcLength {}
+
+impl PartialOrd for NoCalcLength {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        use self::NoCalcLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return None;
+        }
+
+        match (self, other) {
+            (&Absolute(ref one), &Absolute(ref other)) => one.to_px().partial_cmp(&other.to_px()),
+            (&FontRelative(ref one), &FontRelative(ref other)) => one.partial_cmp(other),
+            (&ViewportPercentage(ref one), &ViewportPercentage(ref other)) => {
+                one.partial_cmp(other)
+            },
+            (&ContainerRelative(ref one), &ContainerRelative(ref other)) => one.partial_cmp(other),
+            (&ServoCharacterWidth(ref one), &ServoCharacterWidth(ref other)) => {
+                one.0.partial_cmp(&other.0)
+            },
+            // See https://github.com/rust-lang/rust/issues/68867. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Absolute(..) |
+                    FontRelative(..) |
+                    ViewportPercentage(..) |
+                    ContainerRelative(..) |
+                    ServoCharacterWidth(..) => {},
+                }
+                debug_unreachable!("Forgot an arm in partial_cmp?")
+            },
+        }
+    }
+}
+
+impl Zero for NoCalcLength {
+    fn zero() -> Self {
+        NoCalcLength::Absolute(AbsoluteLength::Px(0.))
+    }
+
+    fn is_zero(&self) -> bool {
+        NoCalcLength::is_zero(self)
+    }
+}
+
+/// An extension to `NoCalcLength` to parse `calc` expressions.
+/// This is commonly used for the `<length>` values.
+///
+/// <https://drafts.csswg.org/css-values/#lengths>
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum Length {
+    /// The internal length type that cannot parse `calc`
+    NoCalc(NoCalcLength),
+    /// A calc expression.
+    ///
+    /// <https://drafts.csswg.org/css-values/#calc-notation>
+    Calc(Box<CalcLengthPercentage>),
+}
+
+impl From<NoCalcLength> for Length {
+    #[inline]
+    fn from(len: NoCalcLength) -> Self {
+        Length::NoCalc(len)
+    }
+}
+
+impl Mul<CSSFloat> for Length {
+    type Output = Length;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> Length {
+        match self {
+            Length::NoCalc(inner) => Length::NoCalc(inner * scalar),
+            Length::Calc(..) => panic!("Can't multiply Calc!"),
+        }
+    }
+}
+
+impl PartialOrd for FontRelativeLength {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        use self::FontRelativeLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return None;
+        }
+
+        match (self, other) {
+            (&Em(ref one), &Em(ref other)) => one.partial_cmp(other),
+            (&Ex(ref one), &Ex(ref other)) => one.partial_cmp(other),
+            (&Ch(ref one), &Ch(ref other)) => one.partial_cmp(other),
+            (&Cap(ref one), &Cap(ref other)) => one.partial_cmp(other),
+            (&Ic(ref one), &Ic(ref other)) => one.partial_cmp(other),
+            (&Rem(ref one), &Rem(ref other)) => one.partial_cmp(other),
+            // See https://github.com/rust-lang/rust/issues/68867. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Em(..) | Ex(..) | Ch(..) | Cap(..) | Ic(..) | Rem(..) => {},
+                }
+                debug_unreachable!("Forgot an arm in partial_cmp?")
+            },
+        }
+    }
+}
+
+impl Mul<CSSFloat> for FontRelativeLength {
+    type Output = FontRelativeLength;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> FontRelativeLength {
+        match self {
+            FontRelativeLength::Em(v) => FontRelativeLength::Em(v * scalar),
+            FontRelativeLength::Ex(v) => FontRelativeLength::Ex(v * scalar),
+            FontRelativeLength::Ch(v) => FontRelativeLength::Ch(v * scalar),
+            FontRelativeLength::Cap(v) => FontRelativeLength::Cap(v * scalar),
+            FontRelativeLength::Ic(v) => FontRelativeLength::Ic(v * scalar),
+            FontRelativeLength::Rem(v) => FontRelativeLength::Rem(v * scalar),
+        }
+    }
+}
+
+impl Mul<CSSFloat> for ContainerRelativeLength {
+    type Output = ContainerRelativeLength;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> ContainerRelativeLength {
+        match self {
+            ContainerRelativeLength::Cqw(v) => ContainerRelativeLength::Cqw(v * scalar),
+            ContainerRelativeLength::Cqh(v) => ContainerRelativeLength::Cqh(v * scalar),
+            ContainerRelativeLength::Cqi(v) => ContainerRelativeLength::Cqi(v * scalar),
+            ContainerRelativeLength::Cqb(v) => ContainerRelativeLength::Cqb(v * scalar),
+            ContainerRelativeLength::Cqmin(v) => ContainerRelativeLength::Cqmin(v * scalar),
+            ContainerRelativeLength::Cqmax(v) => ContainerRelativeLength::Cqmax(v * scalar),
+        }
+    }
+}
+
+impl PartialOrd for ContainerRelativeLength {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        use self::ContainerRelativeLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return None;
+        }
+
+        match (self, other) {
+            (&Cqw(ref one), &Cqw(ref other)) => one.partial_cmp(other),
+            (&Cqh(ref one), &Cqh(ref other)) => one.partial_cmp(other),
+            (&Cqi(ref one), &Cqi(ref other)) => one.partial_cmp(other),
+            (&Cqb(ref one), &Cqb(ref other)) => one.partial_cmp(other),
+            (&Cqmin(ref one), &Cqmin(ref other)) => one.partial_cmp(other),
+            (&Cqmax(ref one), &Cqmax(ref other)) => one.partial_cmp(other),
+
+            // See https://github.com/rust-lang/rust/issues/68867, then
+            // https://github.com/rust-lang/rust/pull/95161. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Cqw(..) | Cqh(..) | Cqi(..) | Cqb(..) | Cqmin(..) | Cqmax(..) => {},
+                }
+                debug_unreachable!("Forgot to handle unit in partial_cmp()")
+            },
+        }
+    }
+}
+
+impl Mul<CSSFloat> for ViewportPercentageLength {
+    type Output = ViewportPercentageLength;
+
+    #[inline]
+    fn mul(self, scalar: CSSFloat) -> ViewportPercentageLength {
+        match self {
+            ViewportPercentageLength::Vw(v) => ViewportPercentageLength::Vw(v * scalar),
+            ViewportPercentageLength::Svw(v) => ViewportPercentageLength::Svw(v * scalar),
+            ViewportPercentageLength::Lvw(v) => ViewportPercentageLength::Lvw(v * scalar),
+            ViewportPercentageLength::Dvw(v) => ViewportPercentageLength::Dvw(v * scalar),
+            ViewportPercentageLength::Vh(v) => ViewportPercentageLength::Vh(v * scalar),
+            ViewportPercentageLength::Svh(v) => ViewportPercentageLength::Svh(v * scalar),
+            ViewportPercentageLength::Lvh(v) => ViewportPercentageLength::Lvh(v * scalar),
+            ViewportPercentageLength::Dvh(v) => ViewportPercentageLength::Dvh(v * scalar),
+            ViewportPercentageLength::Vmin(v) => ViewportPercentageLength::Vmin(v * scalar),
+            ViewportPercentageLength::Svmin(v) => ViewportPercentageLength::Svmin(v * scalar),
+            ViewportPercentageLength::Lvmin(v) => ViewportPercentageLength::Lvmin(v * scalar),
+            ViewportPercentageLength::Dvmin(v) => ViewportPercentageLength::Dvmin(v * scalar),
+            ViewportPercentageLength::Vmax(v) => ViewportPercentageLength::Vmax(v * scalar),
+            ViewportPercentageLength::Svmax(v) => ViewportPercentageLength::Svmax(v * scalar),
+            ViewportPercentageLength::Lvmax(v) => ViewportPercentageLength::Lvmax(v * scalar),
+            ViewportPercentageLength::Dvmax(v) => ViewportPercentageLength::Dvmax(v * scalar),
+            ViewportPercentageLength::Vb(v) => ViewportPercentageLength::Vb(v * scalar),
+            ViewportPercentageLength::Svb(v) => ViewportPercentageLength::Svb(v * scalar),
+            ViewportPercentageLength::Lvb(v) => ViewportPercentageLength::Lvb(v * scalar),
+            ViewportPercentageLength::Dvb(v) => ViewportPercentageLength::Dvb(v * scalar),
+            ViewportPercentageLength::Vi(v) => ViewportPercentageLength::Vi(v * scalar),
+            ViewportPercentageLength::Svi(v) => ViewportPercentageLength::Svi(v * scalar),
+            ViewportPercentageLength::Lvi(v) => ViewportPercentageLength::Lvi(v * scalar),
+            ViewportPercentageLength::Dvi(v) => ViewportPercentageLength::Dvi(v * scalar),
+        }
+    }
+}
+
+impl PartialOrd for ViewportPercentageLength {
+    fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
+        use self::ViewportPercentageLength::*;
+
+        if std::mem::discriminant(self) != std::mem::discriminant(other) {
+            return None;
+        }
+
+        match (self, other) {
+            (&Vw(ref one), &Vw(ref other)) => one.partial_cmp(other),
+            (&Svw(ref one), &Svw(ref other)) => one.partial_cmp(other),
+            (&Lvw(ref one), &Lvw(ref other)) => one.partial_cmp(other),
+            (&Dvw(ref one), &Dvw(ref other)) => one.partial_cmp(other),
+            (&Vh(ref one), &Vh(ref other)) => one.partial_cmp(other),
+            (&Svh(ref one), &Svh(ref other)) => one.partial_cmp(other),
+            (&Lvh(ref one), &Lvh(ref other)) => one.partial_cmp(other),
+            (&Dvh(ref one), &Dvh(ref other)) => one.partial_cmp(other),
+            (&Vmin(ref one), &Vmin(ref other)) => one.partial_cmp(other),
+            (&Svmin(ref one), &Svmin(ref other)) => one.partial_cmp(other),
+            (&Lvmin(ref one), &Lvmin(ref other)) => one.partial_cmp(other),
+            (&Dvmin(ref one), &Dvmin(ref other)) => one.partial_cmp(other),
+            (&Vmax(ref one), &Vmax(ref other)) => one.partial_cmp(other),
+            (&Svmax(ref one), &Svmax(ref other)) => one.partial_cmp(other),
+            (&Lvmax(ref one), &Lvmax(ref other)) => one.partial_cmp(other),
+            (&Dvmax(ref one), &Dvmax(ref other)) => one.partial_cmp(other),
+            (&Vb(ref one), &Vb(ref other)) => one.partial_cmp(other),
+            (&Svb(ref one), &Svb(ref other)) => one.partial_cmp(other),
+            (&Lvb(ref one), &Lvb(ref other)) => one.partial_cmp(other),
+            (&Dvb(ref one), &Dvb(ref other)) => one.partial_cmp(other),
+            (&Vi(ref one), &Vi(ref other)) => one.partial_cmp(other),
+            (&Svi(ref one), &Svi(ref other)) => one.partial_cmp(other),
+            (&Lvi(ref one), &Lvi(ref other)) => one.partial_cmp(other),
+            (&Dvi(ref one), &Dvi(ref other)) => one.partial_cmp(other),
+            // See https://github.com/rust-lang/rust/issues/68867. rustc isn't
+            // able to figure it own on its own so we help.
+            _ => unsafe {
+                match *self {
+                    Vw(..) | Svw(..) | Lvw(..) | Dvw(..) | Vh(..) | Svh(..) | Lvh(..) |
+                    Dvh(..) | Vmin(..) | Svmin(..) | Lvmin(..) | Dvmin(..) | Vmax(..) |
+                    Svmax(..) | Lvmax(..) | Dvmax(..) | Vb(..) | Svb(..) | Lvb(..) | Dvb(..) |
+                    Vi(..) | Svi(..) | Lvi(..) | Dvi(..) => {},
+                }
+                debug_unreachable!("Forgot an arm in partial_cmp?")
+            },
+        }
+    }
+}
+
+impl Length {
+    #[inline]
+    fn parse_internal<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        num_context: AllowedNumericType,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let token = input.next()?;
+        match *token {
+            Token::Dimension {
+                value, ref unit, ..
+            } if num_context.is_ok(context.parsing_mode, value) => {
+                NoCalcLength::parse_dimension(context, value, unit)
+                    .map(Length::NoCalc)
+                    .map_err(|()| location.new_unexpected_token_error(token.clone()))
+            },
+            Token::Number { value, .. } if num_context.is_ok(context.parsing_mode, value) => {
+                if value != 0. &&
+                    !context.parsing_mode.allows_unitless_lengths() &&
+                    !allow_quirks.allowed(context.quirks_mode)
+                {
+                    return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+                Ok(Length::NoCalc(NoCalcLength::Absolute(AbsoluteLength::Px(
+                    value,
+                ))))
+            },
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                let calc = CalcNode::parse_length(context, input, num_context, function)?;
+                Ok(Length::Calc(Box::new(calc)))
+            },
+            ref token => return Err(location.new_unexpected_token_error(token.clone())),
+        }
+    }
+
+    /// Parse a non-negative length
+    #[inline]
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_non_negative_quirky(context, input, AllowQuirks::No)
+    }
+
+    /// Parse a non-negative length, allowing quirks.
+    #[inline]
+    pub fn parse_non_negative_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(
+            context,
+            input,
+            AllowedNumericType::NonNegative,
+            allow_quirks,
+        )
+    }
+
+    /// Get an absolute length from a px value.
+    #[inline]
+    pub fn from_px(px_value: CSSFloat) -> Length {
+        Length::NoCalc(NoCalcLength::from_px(px_value))
+    }
+}
+
+impl Parse for Length {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl Zero for Length {
+    fn zero() -> Self {
+        Length::NoCalc(NoCalcLength::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        // FIXME(emilio): Seems a bit weird to treat calc() unconditionally as
+        // non-zero here?
+        match *self {
+            Length::NoCalc(ref l) => l.is_zero(),
+            Length::Calc(..) => false,
+        }
+    }
+}
+
+impl Length {
+    /// Parses a length, with quirks.
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(context, input, AllowedNumericType::All, allow_quirks)
+    }
+}
+
+/// A wrapper of Length, whose value must be >= 0.
+pub type NonNegativeLength = NonNegative<Length>;
+
+impl Parse for NonNegativeLength {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(NonNegative(Length::parse_non_negative(context, input)?))
+    }
+}
+
+impl From<NoCalcLength> for NonNegativeLength {
+    #[inline]
+    fn from(len: NoCalcLength) -> Self {
+        NonNegative(Length::NoCalc(len))
+    }
+}
+
+impl From<Length> for NonNegativeLength {
+    #[inline]
+    fn from(len: Length) -> Self {
+        NonNegative(len)
+    }
+}
+
+impl NonNegativeLength {
+    /// Get an absolute length from a px value.
+    #[inline]
+    pub fn from_px(px_value: CSSFloat) -> Self {
+        Length::from_px(px_value.max(0.)).into()
+    }
+
+    /// Parses a non-negative length, optionally with quirks.
+    #[inline]
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(NonNegative(Length::parse_non_negative_quirky(
+            context,
+            input,
+            allow_quirks,
+        )?))
+    }
+}
+
+/// A `<length-percentage>` value. This can be either a `<length>`, a
+/// `<percentage>`, or a combination of both via `calc()`.
+///
+/// https://drafts.csswg.org/css-values-4/#typedef-length-percentage
+#[allow(missing_docs)]
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum LengthPercentage {
+    Length(NoCalcLength),
+    Percentage(computed::Percentage),
+    Calc(Box<CalcLengthPercentage>),
+}
+
+impl From<Length> for LengthPercentage {
+    fn from(len: Length) -> LengthPercentage {
+        match len {
+            Length::NoCalc(l) => LengthPercentage::Length(l),
+            Length::Calc(l) => LengthPercentage::Calc(l),
+        }
+    }
+}
+
+impl From<NoCalcLength> for LengthPercentage {
+    #[inline]
+    fn from(len: NoCalcLength) -> Self {
+        LengthPercentage::Length(len)
+    }
+}
+
+impl From<Percentage> for LengthPercentage {
+    #[inline]
+    fn from(pc: Percentage) -> Self {
+        if let Some(clamping_mode) = pc.calc_clamping_mode() {
+            LengthPercentage::Calc(Box::new(CalcLengthPercentage {
+                clamping_mode,
+                node: CalcNode::Leaf(calc::Leaf::Percentage(pc.get())),
+            }))
+        } else {
+            LengthPercentage::Percentage(computed::Percentage(pc.get()))
+        }
+    }
+}
+
+impl From<computed::Percentage> for LengthPercentage {
+    #[inline]
+    fn from(pc: computed::Percentage) -> Self {
+        LengthPercentage::Percentage(pc)
+    }
+}
+
+impl Parse for LengthPercentage {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl LengthPercentage {
+    #[inline]
+    /// Returns a `0%` value.
+    pub fn zero_percent() -> LengthPercentage {
+        LengthPercentage::Percentage(computed::Percentage::zero())
+    }
+
+    #[inline]
+    /// Returns a `100%` value.
+    pub fn hundred_percent() -> LengthPercentage {
+        LengthPercentage::Percentage(computed::Percentage::hundred())
+    }
+
+    fn parse_internal<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        num_context: AllowedNumericType,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let token = input.next()?;
+        match *token {
+            Token::Dimension {
+                value, ref unit, ..
+            } if num_context.is_ok(context.parsing_mode, value) => {
+                return NoCalcLength::parse_dimension(context, value, unit)
+                    .map(LengthPercentage::Length)
+                    .map_err(|()| location.new_unexpected_token_error(token.clone()));
+            },
+            Token::Percentage { unit_value, .. }
+                if num_context.is_ok(context.parsing_mode, unit_value) =>
+            {
+                return Ok(LengthPercentage::Percentage(computed::Percentage(
+                    unit_value,
+                )));
+            },
+            Token::Number { value, .. } if num_context.is_ok(context.parsing_mode, value) => {
+                if value != 0. &&
+                    !context.parsing_mode.allows_unitless_lengths() &&
+                    !allow_quirks.allowed(context.quirks_mode)
+                {
+                    return Err(location.new_unexpected_token_error(token.clone()));
+                } else {
+                    return Ok(LengthPercentage::Length(NoCalcLength::from_px(value)));
+                }
+            },
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                let calc =
+                    CalcNode::parse_length_or_percentage(context, input, num_context, function)?;
+                Ok(LengthPercentage::Calc(Box::new(calc)))
+            },
+            _ => return Err(location.new_unexpected_token_error(token.clone())),
+        }
+    }
+
+    /// Parses allowing the unitless length quirk.
+    /// <https://quirks.spec.whatwg.org/#the-unitless-length-quirk>
+    #[inline]
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(context, input, AllowedNumericType::All, allow_quirks)
+    }
+
+    /// Parse a non-negative length.
+    ///
+    /// FIXME(emilio): This should be not public and we should use
+    /// NonNegativeLengthPercentage instead.
+    #[inline]
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_non_negative_quirky(context, input, AllowQuirks::No)
+    }
+
+    /// Parse a non-negative length, with quirks.
+    #[inline]
+    pub fn parse_non_negative_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_internal(
+            context,
+            input,
+            AllowedNumericType::NonNegative,
+            allow_quirks,
+        )
+    }
+}
+
+impl Zero for LengthPercentage {
+    fn zero() -> Self {
+        LengthPercentage::Length(NoCalcLength::zero())
+    }
+
+    fn is_zero(&self) -> bool {
+        match *self {
+            LengthPercentage::Length(l) => l.is_zero(),
+            LengthPercentage::Percentage(p) => p.0 == 0.0,
+            LengthPercentage::Calc(_) => false,
+        }
+    }
+}
+
+impl ZeroNoPercent for LengthPercentage {
+    fn is_zero_no_percent(&self) -> bool {
+        match *self {
+            LengthPercentage::Percentage(_) => false,
+            _ => self.is_zero(),
+        }
+    }
+}
+
+/// A specified type for `<length-percentage> | auto`.
+pub type LengthPercentageOrAuto = generics::LengthPercentageOrAuto<LengthPercentage>;
+
+impl LengthPercentageOrAuto {
+    /// Returns a value representing `0%`.
+    #[inline]
+    pub fn zero_percent() -> Self {
+        generics::LengthPercentageOrAuto::LengthPercentage(LengthPercentage::zero_percent())
+    }
+
+    /// Parses a length or a percentage, allowing the unitless length quirk.
+    /// <https://quirks.spec.whatwg.org/#the-unitless-length-quirk>
+    #[inline]
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with(context, input, |context, input| {
+            LengthPercentage::parse_quirky(context, input, allow_quirks)
+        })
+    }
+}
+
+/// A wrapper of LengthPercentageOrAuto, whose value must be >= 0.
+pub type NonNegativeLengthPercentageOrAuto =
+    generics::LengthPercentageOrAuto<NonNegativeLengthPercentage>;
+
+impl NonNegativeLengthPercentageOrAuto {
+    /// Returns a value representing `0%`.
+    #[inline]
+    pub fn zero_percent() -> Self {
+        generics::LengthPercentageOrAuto::LengthPercentage(
+            NonNegativeLengthPercentage::zero_percent(),
+        )
+    }
+
+    /// Parses a non-negative length-percentage, allowing the unitless length
+    /// quirk.
+    #[inline]
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with(context, input, |context, input| {
+            NonNegativeLengthPercentage::parse_quirky(context, input, allow_quirks)
+        })
+    }
+}
+
+/// A wrapper of LengthPercentage, whose value must be >= 0.
+pub type NonNegativeLengthPercentage = NonNegative<LengthPercentage>;
+
+/// Either a NonNegativeLengthPercentage or the `normal` keyword.
+pub type NonNegativeLengthPercentageOrNormal =
+    GenericLengthPercentageOrNormal<NonNegativeLengthPercentage>;
+
+impl From<NoCalcLength> for NonNegativeLengthPercentage {
+    #[inline]
+    fn from(len: NoCalcLength) -> Self {
+        NonNegative(LengthPercentage::from(len))
+    }
+}
+
+impl Parse for NonNegativeLengthPercentage {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl NonNegativeLengthPercentage {
+    #[inline]
+    /// Returns a `0%` value.
+    pub fn zero_percent() -> Self {
+        NonNegative(LengthPercentage::zero_percent())
+    }
+
+    /// Parses a length or a percentage, allowing the unitless length quirk.
+    /// <https://quirks.spec.whatwg.org/#the-unitless-length-quirk>
+    #[inline]
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        LengthPercentage::parse_non_negative_quirky(context, input, allow_quirks).map(NonNegative)
+    }
+}
+
+/// Either a `<length>` or the `auto` keyword.
+///
+/// Note that we use LengthPercentage just for convenience, since it pretty much
+/// is everything we care about, but we could just add a similar LengthOrAuto
+/// instead if we think getting rid of this weirdness is worth it.
+pub type LengthOrAuto = generics::LengthPercentageOrAuto<Length>;
+
+impl LengthOrAuto {
+    /// Parses a length, allowing the unitless length quirk.
+    /// <https://quirks.spec.whatwg.org/#the-unitless-length-quirk>
+    #[inline]
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with(context, input, |context, input| {
+            Length::parse_quirky(context, input, allow_quirks)
+        })
+    }
+}
+
+/// Either a non-negative `<length>` or the `auto` keyword.
+pub type NonNegativeLengthOrAuto = generics::LengthPercentageOrAuto<NonNegativeLength>;
+
+/// Either a `<length>` or a `<number>`.
+pub type LengthOrNumber = GenericLengthOrNumber<Length, Number>;
+
+/// A specified value for `min-width`, `min-height`, `width` or `height` property.
+pub type Size = GenericSize<NonNegativeLengthPercentage>;
+
+impl Parse for Size {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Size::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+macro_rules! parse_size_non_length {
+    ($size:ident, $input:expr, $auto_or_none:expr => $auto_or_none_ident:ident) => {{
+        let size = $input.try_parse(|input| {
+            Ok(try_match_ident_ignore_ascii_case! { input,
+                #[cfg(feature = "gecko")]
+                "min-content" | "-moz-min-content" => $size::MinContent,
+                #[cfg(feature = "gecko")]
+                "max-content" | "-moz-max-content" => $size::MaxContent,
+                #[cfg(feature = "gecko")]
+                "fit-content" | "-moz-fit-content" => $size::FitContent,
+                #[cfg(feature = "gecko")]
+                "-moz-available" => $size::MozAvailable,
+                $auto_or_none => $size::$auto_or_none_ident,
+            })
+        });
+        if size.is_ok() {
+            return size;
+        }
+    }};
+}
+
+#[cfg(feature = "gecko")]
+fn is_fit_content_function_enabled() -> bool {
+    static_prefs::pref!("layout.css.fit-content-function.enabled")
+}
+#[cfg(feature = "servo")]
+fn is_fit_content_function_enabled() -> bool {
+    false
+}
+
+macro_rules! parse_fit_content_function {
+    ($size:ident, $input:expr, $context:expr, $allow_quirks:expr) => {
+        if is_fit_content_function_enabled() {
+            if let Ok(length) = $input.try_parse(|input| {
+                input.expect_function_matching("fit-content")?;
+                input.parse_nested_block(|i| {
+                    NonNegativeLengthPercentage::parse_quirky($context, i, $allow_quirks)
+                })
+            }) {
+                return Ok($size::FitContentFunction(length));
+            }
+        }
+    };
+}
+
+impl Size {
+    /// Parses, with quirks.
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        parse_size_non_length!(Size, input, "auto" => Auto);
+        parse_fit_content_function!(Size, input, context, allow_quirks);
+
+        let length = NonNegativeLengthPercentage::parse_quirky(context, input, allow_quirks)?;
+        Ok(GenericSize::LengthPercentage(length))
+    }
+
+    /// Returns `0%`.
+    #[inline]
+    pub fn zero_percent() -> Self {
+        GenericSize::LengthPercentage(NonNegativeLengthPercentage::zero_percent())
+    }
+}
+
+/// A specified value for `max-width` or `max-height` property.
+pub type MaxSize = GenericMaxSize<NonNegativeLengthPercentage>;
+
+impl Parse for MaxSize {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        MaxSize::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl MaxSize {
+    /// Parses, with quirks.
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        parse_size_non_length!(MaxSize, input, "none" => None);
+        parse_fit_content_function!(MaxSize, input, context, allow_quirks);
+
+        let length = NonNegativeLengthPercentage::parse_quirky(context, input, allow_quirks)?;
+        Ok(GenericMaxSize::LengthPercentage(length))
+    }
+}
+
+/// A specified non-negative `<length>` | `<number>`.
+pub type NonNegativeLengthOrNumber = GenericLengthOrNumber<NonNegativeLength, NonNegativeNumber>;
diff --git a/servo/components/style/values/specified/list.rs b/servo/components/style/values/specified/list.rs
new file mode 100644
index 0000000000..693471e478
--- /dev/null
+++ b/servo/components/style/values/specified/list.rs
@@ -0,0 +1,202 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! `list` specified values.
+
+use crate::parser::{Parse, ParserContext};
+#[cfg(feature = "gecko")]
+use crate::values::generics::CounterStyle;
+#[cfg(feature = "gecko")]
+use crate::values::CustomIdent;
+use cssparser::{Parser, Token};
+use style_traits::{ParseError, StyleParseErrorKind};
+
+/// Specified and computed `list-style-type` property.
+#[cfg(feature = "gecko")]
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum ListStyleType {
+    /// `none`
+    None,
+    /// <counter-style>
+    CounterStyle(CounterStyle),
+    /// <string>
+    String(String),
+}
+
+#[cfg(feature = "gecko")]
+impl ListStyleType {
+    /// Initial specified value for `list-style-type`.
+    #[inline]
+    pub fn disc() -> Self {
+        ListStyleType::CounterStyle(CounterStyle::disc())
+    }
+
+    /// Convert from gecko keyword to list-style-type.
+    ///
+    /// This should only be used for mapping type attribute to
+    /// list-style-type, and thus only values possible in that
+    /// attribute is considered here.
+    pub fn from_gecko_keyword(value: u32) -> Self {
+        use crate::gecko_bindings::structs;
+        let v8 = value as u8;
+
+        if v8 == structs::ListStyle_None {
+            return ListStyleType::None;
+        }
+
+        ListStyleType::CounterStyle(CounterStyle::Name(CustomIdent(match v8 {
+            structs::ListStyle_Disc => atom!("disc"),
+            structs::ListStyle_Circle => atom!("circle"),
+            structs::ListStyle_Square => atom!("square"),
+            structs::ListStyle_Decimal => atom!("decimal"),
+            structs::ListStyle_LowerRoman => atom!("lower-roman"),
+            structs::ListStyle_UpperRoman => atom!("upper-roman"),
+            structs::ListStyle_LowerAlpha => atom!("lower-alpha"),
+            structs::ListStyle_UpperAlpha => atom!("upper-alpha"),
+            _ => unreachable!("Unknown counter style keyword value"),
+        })))
+    }
+
+    /// Is this a bullet? (i.e. `list-style-type: disc|circle|square|disclosure-closed|disclosure-open`)
+    #[inline]
+    pub fn is_bullet(&self) -> bool {
+        match self {
+            ListStyleType::CounterStyle(ref style) => style.is_bullet(),
+            _ => false,
+        }
+    }
+}
+
+#[cfg(feature = "gecko")]
+impl Parse for ListStyleType {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(style) = input.try_parse(|i| CounterStyle::parse(context, i)) {
+            return Ok(ListStyleType::CounterStyle(style));
+        }
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(ListStyleType::None);
+        }
+        Ok(ListStyleType::String(
+            input.expect_string()?.as_ref().to_owned(),
+        ))
+    }
+}
+
+/// A quote pair.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct QuotePair {
+    /// The opening quote.
+    pub opening: crate::OwnedStr,
+
+    /// The closing quote.
+    pub closing: crate::OwnedStr,
+}
+
+/// List of quote pairs for the specified/computed value of `quotes` property.
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct QuoteList(
+    #[css(iterable, if_empty = "none")]
+    #[ignore_malloc_size_of = "Arc"]
+    pub crate::ArcSlice<QuotePair>,
+);
+
+/// Specified and computed `quotes` property: `auto`, `none`, or a list
+/// of characters.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub enum Quotes {
+    /// list of quote pairs
+    QuoteList(QuoteList),
+    /// auto (use lang-dependent quote marks)
+    Auto,
+}
+
+impl Parse for Quotes {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Quotes, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("auto"))
+            .is_ok()
+        {
+            return Ok(Quotes::Auto);
+        }
+
+        if input
+            .try_parse(|input| input.expect_ident_matching("none"))
+            .is_ok()
+        {
+            return Ok(Quotes::QuoteList(QuoteList::default()));
+        }
+
+        let mut quotes = Vec::new();
+        loop {
+            let location = input.current_source_location();
+            let opening = match input.next() {
+                Ok(&Token::QuotedString(ref value)) => value.as_ref().to_owned().into(),
+                Ok(t) => return Err(location.new_unexpected_token_error(t.clone())),
+                Err(_) => break,
+            };
+
+            let closing = input.expect_string()?.as_ref().to_owned().into();
+            quotes.push(QuotePair { opening, closing });
+        }
+
+        if !quotes.is_empty() {
+            Ok(Quotes::QuoteList(QuoteList(crate::ArcSlice::from_iter(
+                quotes.into_iter(),
+            ))))
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
diff --git a/servo/components/style/values/specified/mod.rs b/servo/components/style/values/specified/mod.rs
new file mode 100644
index 0000000000..fd1307f4e1
--- /dev/null
+++ b/servo/components/style/values/specified/mod.rs
@@ -0,0 +1,958 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified values.
+//!
+//! TODO(emilio): Enhance docs.
+
+use super::computed::transform::DirectionVector;
+use super::computed::{Context, ToComputedValue};
+use super::generics::grid::ImplicitGridTracks as GenericImplicitGridTracks;
+use super::generics::grid::{GridLine as GenericGridLine, TrackBreadth as GenericTrackBreadth};
+use super::generics::grid::{TrackList as GenericTrackList, TrackSize as GenericTrackSize};
+use super::generics::transform::IsParallelTo;
+use super::generics::{self, GreaterThanOrEqualToOne, NonNegative};
+use super::{CSSFloat, CSSInteger};
+use crate::context::QuirksMode;
+use crate::parser::{Parse, ParserContext};
+use crate::values::serialize_atom_identifier;
+use crate::values::specified::calc::CalcNode;
+use crate::{Atom, Namespace, One, Prefix, Zero};
+use cssparser::{Parser, Token};
+use std::f32;
+use std::fmt::{self, Write};
+use std::ops::Add;
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, StyleParseErrorKind, ToCss};
+
+#[cfg(feature = "gecko")]
+pub use self::align::{AlignContent, AlignItems, AlignSelf, AlignTracks, ContentDistribution};
+#[cfg(feature = "gecko")]
+pub use self::align::{JustifyContent, JustifyItems, JustifySelf, JustifyTracks, SelfAlignment};
+pub use self::angle::{AllowUnitlessZeroAngle, Angle};
+pub use self::background::{BackgroundRepeat, BackgroundSize};
+pub use self::basic_shape::FillRule;
+pub use self::border::{BorderCornerRadius, BorderImageSlice, BorderImageWidth};
+pub use self::border::{BorderImageRepeat, BorderImageSideWidth};
+pub use self::border::{BorderRadius, BorderSideWidth, BorderSpacing, BorderStyle};
+pub use self::box_::{AnimationIterationCount, AnimationName, AnimationTimeline, Contain, Display};
+pub use self::box_::{Appearance, BreakBetween, BreakWithin, ContainerName, ContainerType};
+pub use self::box_::{
+    Clear, ContainIntrinsicSize, ContentVisibility, Float, LineClamp, Overflow, OverflowAnchor,
+};
+pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize, ScrollbarGutter};
+pub use self::box_::{ScrollAxis, ScrollSnapAlign, ScrollSnapAxis, ScrollSnapStop};
+pub use self::box_::{ScrollSnapStrictness, ScrollSnapType, ScrollTimelineName};
+pub use self::box_::{TouchAction, TransitionProperty, VerticalAlign, WillChange};
+pub use self::color::{Color, ColorOrAuto, ColorPropertyValue, ColorScheme, PrintColorAdjust};
+pub use self::column::ColumnCount;
+pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset, CounterSet};
+pub use self::easing::TimingFunction;
+pub use self::effects::{BoxShadow, Filter, SimpleShadow};
+pub use self::flex::FlexBasis;
+pub use self::font::{FontFamily, FontLanguageOverride, FontStyle, FontPalette};
+pub use self::font::{FontFeatureSettings, FontVariantLigatures, FontVariantNumeric};
+pub use self::font::{FontSize, FontSizeAdjust, FontSizeKeyword, FontStretch, FontSynthesis};
+pub use self::font::{FontVariantAlternates, FontWeight};
+pub use self::font::{FontVariantEastAsian, FontVariationSettings};
+pub use self::font::{MathDepth, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextZoom};
+pub use self::image::{EndingShape as GradientEndingShape, Gradient};
+pub use self::image::{Image, ImageRendering, MozImageRect};
+pub use self::length::{AbsoluteLength, CalcLengthPercentage, CharacterWidth};
+pub use self::length::{FontRelativeLength, Length, LengthOrNumber, NonNegativeLengthOrNumber};
+pub use self::length::{LengthOrAuto, LengthPercentage, LengthPercentageOrAuto};
+pub use self::length::{MaxSize, Size};
+pub use self::length::{NoCalcLength, ViewportPercentageLength, ViewportVariant};
+pub use self::length::{
+    NonNegativeLength, NonNegativeLengthPercentage, NonNegativeLengthPercentageOrAuto,
+};
+#[cfg(feature = "gecko")]
+pub use self::list::ListStyleType;
+pub use self::list::Quotes;
+pub use self::motion::{OffsetPath, OffsetRotate};
+pub use self::outline::OutlineStyle;
+pub use self::page::{PageName, PageSize, PageSizeOrientation, PaperSize};
+pub use self::percentage::{NonNegativePercentage, Percentage};
+pub use self::position::AspectRatio;
+pub use self::position::{
+    GridAutoFlow, GridTemplateAreas, Position, PositionOrAuto,
+};
+pub use self::position::{MasonryAutoFlow, MasonryPlacement, MasonryItemOrder};
+pub use self::position::{PositionComponent, ZIndex};
+pub use self::ratio::Ratio;
+pub use self::rect::NonNegativeLengthOrNumberRect;
+pub use self::resolution::Resolution;
+pub use self::svg::{DProperty, MozContextProperties};
+pub use self::svg::{SVGLength, SVGOpacity, SVGPaint};
+pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
+pub use self::svg_path::SVGPathData;
+pub use self::text::HyphenateCharacter;
+pub use self::text::RubyPosition;
+pub use self::text::TextAlignLast;
+pub use self::text::TextUnderlinePosition;
+pub use self::text::{InitialLetter, LetterSpacing, LineBreak, LineHeight, TextAlign};
+pub use self::text::{OverflowWrap, TextEmphasisPosition, TextEmphasisStyle, WordBreak};
+pub use self::text::{TextAlignKeyword, TextDecorationLine, TextOverflow, WordSpacing};
+pub use self::text::{TextDecorationLength, TextDecorationSkipInk, TextJustify, TextTransform};
+pub use self::time::Time;
+pub use self::transform::{Rotate, Scale, Transform};
+pub use self::transform::{TransformOrigin, TransformStyle, Translate};
+#[cfg(feature = "gecko")]
+pub use self::ui::CursorImage;
+pub use self::ui::{BoolInteger, Cursor, UserSelect};
+pub use super::generics::grid::GridTemplateComponent as GenericGridTemplateComponent;
+
+#[cfg(feature = "gecko")]
+pub mod align;
+pub mod angle;
+pub mod background;
+pub mod basic_shape;
+pub mod border;
+#[path = "box.rs"]
+pub mod box_;
+pub mod calc;
+pub mod color;
+pub mod column;
+pub mod counters;
+pub mod easing;
+pub mod effects;
+pub mod flex;
+pub mod font;
+#[cfg(feature = "gecko")]
+pub mod gecko;
+pub mod grid;
+pub mod image;
+pub mod length;
+pub mod list;
+pub mod motion;
+pub mod outline;
+pub mod page;
+pub mod percentage;
+pub mod position;
+pub mod ratio;
+pub mod rect;
+pub mod resolution;
+pub mod source_size_list;
+pub mod svg;
+pub mod svg_path;
+pub mod table;
+pub mod text;
+pub mod time;
+pub mod transform;
+pub mod ui;
+pub mod url;
+
+/// <angle> | <percentage>
+/// https://drafts.csswg.org/css-values/#typedef-angle-percentage
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum AngleOrPercentage {
+    Percentage(Percentage),
+    Angle(Angle),
+}
+
+impl AngleOrPercentage {
+    fn parse_internal<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_unitless_zero: AllowUnitlessZeroAngle,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(per) = input.try_parse(|i| Percentage::parse(context, i)) {
+            return Ok(AngleOrPercentage::Percentage(per));
+        }
+
+        Angle::parse_internal(context, input, allow_unitless_zero).map(AngleOrPercentage::Angle)
+    }
+
+    /// Allow unitless angles, used for conic-gradients as specified by the spec.
+    /// https://drafts.csswg.org/css-images-4/#valdef-conic-gradient-angle
+    pub fn parse_with_unitless<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        AngleOrPercentage::parse_internal(context, input, AllowUnitlessZeroAngle::Yes)
+    }
+}
+
+impl Parse for AngleOrPercentage {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        AngleOrPercentage::parse_internal(context, input, AllowUnitlessZeroAngle::No)
+    }
+}
+
+/// Parse a `<number>` value, with a given clamping mode.
+fn parse_number_with_clamping_mode<'i, 't>(
+    context: &ParserContext,
+    input: &mut Parser<'i, 't>,
+    clamping_mode: AllowedNumericType,
+) -> Result<Number, ParseError<'i>> {
+    let location = input.current_source_location();
+    match *input.next()? {
+        Token::Number { value, .. } if clamping_mode.is_ok(context.parsing_mode, value) => {
+            Ok(Number {
+                value: value.min(f32::MAX).max(f32::MIN),
+                calc_clamping_mode: None,
+            })
+        },
+        Token::Function(ref name) => {
+            let function = CalcNode::math_function(name, location)?;
+            let result = CalcNode::parse_number(context, input, function)?;
+            Ok(Number {
+                value: result.min(f32::MAX).max(f32::MIN),
+                calc_clamping_mode: Some(clamping_mode),
+            })
+        },
+        ref t => Err(location.new_unexpected_token_error(t.clone())),
+    }
+}
+
+/// A CSS `<number>` specified value.
+///
+/// https://drafts.csswg.org/css-values-3/#number-value
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, PartialOrd, ToShmem)]
+pub struct Number {
+    /// The numeric value itself.
+    value: CSSFloat,
+    /// If this number came from a calc() expression, this tells how clamping
+    /// should be done on the value.
+    calc_clamping_mode: Option<AllowedNumericType>,
+}
+
+impl Parse for Number {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        parse_number_with_clamping_mode(context, input, AllowedNumericType::All)
+    }
+}
+
+impl Number {
+    /// Returns a new number with the value `val`.
+    fn new_with_clamping_mode(
+        value: CSSFloat,
+        calc_clamping_mode: Option<AllowedNumericType>,
+    ) -> Self {
+        Self {
+            value,
+            calc_clamping_mode,
+        }
+    }
+
+    /// Returns this percentage as a number.
+    pub fn to_percentage(&self) -> Percentage {
+        Percentage::new_with_clamping_mode(self.value, self.calc_clamping_mode)
+    }
+
+    /// Returns a new number with the value `val`.
+    pub fn new(val: CSSFloat) -> Self {
+        Self::new_with_clamping_mode(val, None)
+    }
+
+    /// Returns whether this number came from a `calc()` expression.
+    #[inline]
+    pub fn was_calc(&self) -> bool {
+        self.calc_clamping_mode.is_some()
+    }
+
+    /// Returns the numeric value, clamped if needed.
+    #[inline]
+    pub fn get(&self) -> f32 {
+        self.calc_clamping_mode
+            .map_or(self.value, |mode| mode.clamp(self.value))
+    }
+
+    #[allow(missing_docs)]
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Number, ParseError<'i>> {
+        parse_number_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+    }
+
+    #[allow(missing_docs)]
+    pub fn parse_at_least_one<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Number, ParseError<'i>> {
+        parse_number_with_clamping_mode(context, input, AllowedNumericType::AtLeastOne)
+    }
+
+    /// Clamp to 1.0 if the value is over 1.0.
+    #[inline]
+    pub fn clamp_to_one(self) -> Self {
+        Number {
+            value: self.value.min(1.),
+            calc_clamping_mode: self.calc_clamping_mode,
+        }
+    }
+}
+
+impl ToComputedValue for Number {
+    type ComputedValue = CSSFloat;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> CSSFloat {
+        self.get()
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &CSSFloat) -> Self {
+        Number {
+            value: *computed,
+            calc_clamping_mode: None,
+        }
+    }
+}
+
+impl ToCss for Number {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.calc_clamping_mode.is_some() {
+            dest.write_str("calc(")?;
+        }
+        self.value.to_css(dest)?;
+        if self.calc_clamping_mode.is_some() {
+            dest.write_str(")")?;
+        }
+        Ok(())
+    }
+}
+
+impl IsParallelTo for (Number, Number, Number) {
+    fn is_parallel_to(&self, vector: &DirectionVector) -> bool {
+        use euclid::approxeq::ApproxEq;
+        // If a and b is parallel, the angle between them is 0deg, so
+        // a x b = |a|*|b|*sin(0)*n = 0 * n, |a x b| == 0.
+        let self_vector = DirectionVector::new(self.0.get(), self.1.get(), self.2.get());
+        self_vector
+            .cross(*vector)
+            .square_length()
+            .approx_eq(&0.0f32)
+    }
+}
+
+impl SpecifiedValueInfo for Number {}
+
+impl Add for Number {
+    type Output = Self;
+
+    fn add(self, other: Self) -> Self {
+        Self::new(self.get() + other.get())
+    }
+}
+
+impl Zero for Number {
+    #[inline]
+    fn zero() -> Self {
+        Self::new(0.)
+    }
+
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.get() == 0.
+    }
+}
+
+impl From<Number> for f32 {
+    #[inline]
+    fn from(n: Number) -> Self {
+        n.get()
+    }
+}
+
+impl From<Number> for f64 {
+    #[inline]
+    fn from(n: Number) -> Self {
+        n.get() as f64
+    }
+}
+
+/// A Number which is >= 0.0.
+pub type NonNegativeNumber = NonNegative<Number>;
+
+impl Parse for NonNegativeNumber {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        parse_number_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+            .map(NonNegative::<Number>)
+    }
+}
+
+impl One for NonNegativeNumber {
+    #[inline]
+    fn one() -> Self {
+        NonNegativeNumber::new(1.0)
+    }
+
+    #[inline]
+    fn is_one(&self) -> bool {
+        self.get() == 1.0
+    }
+}
+
+impl NonNegativeNumber {
+    /// Returns a new non-negative number with the value `val`.
+    pub fn new(val: CSSFloat) -> Self {
+        NonNegative::<Number>(Number::new(val.max(0.)))
+    }
+
+    /// Returns the numeric value.
+    #[inline]
+    pub fn get(&self) -> f32 {
+        self.0.get()
+    }
+}
+
+/// An Integer which is >= 0.
+pub type NonNegativeInteger = NonNegative<Integer>;
+
+impl Parse for NonNegativeInteger {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(NonNegative(Integer::parse_non_negative(context, input)?))
+    }
+}
+
+/// A Number which is >= 1.0.
+pub type GreaterThanOrEqualToOneNumber = GreaterThanOrEqualToOne<Number>;
+
+impl Parse for GreaterThanOrEqualToOneNumber {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        parse_number_with_clamping_mode(context, input, AllowedNumericType::AtLeastOne)
+            .map(GreaterThanOrEqualToOne::<Number>)
+    }
+}
+
+/// <number> | <percentage>
+///
+/// Accepts only non-negative numbers.
+#[allow(missing_docs)]
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum NumberOrPercentage {
+    Percentage(Percentage),
+    Number(Number),
+}
+
+impl NumberOrPercentage {
+    fn parse_with_clamping_mode<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        type_: AllowedNumericType,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(per) =
+            input.try_parse(|i| Percentage::parse_with_clamping_mode(context, i, type_))
+        {
+            return Ok(NumberOrPercentage::Percentage(per));
+        }
+
+        parse_number_with_clamping_mode(context, input, type_).map(NumberOrPercentage::Number)
+    }
+
+    /// Parse a non-negative number or percentage.
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+    }
+
+    /// Convert the number or the percentage to a number.
+    pub fn to_percentage(self) -> Percentage {
+        match self {
+            Self::Percentage(p) => p,
+            Self::Number(n) => n.to_percentage(),
+        }
+    }
+
+    /// Convert the number or the percentage to a number.
+    pub fn to_number(self) -> Number {
+        match self {
+            Self::Percentage(p) => p.to_number(),
+            Self::Number(n) => n,
+        }
+    }
+}
+
+impl Parse for NumberOrPercentage {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::All)
+    }
+}
+
+/// A non-negative <number> | <percentage>.
+pub type NonNegativeNumberOrPercentage = NonNegative<NumberOrPercentage>;
+
+impl NonNegativeNumberOrPercentage {
+    /// Returns the `100%` value.
+    #[inline]
+    pub fn hundred_percent() -> Self {
+        NonNegative(NumberOrPercentage::Percentage(Percentage::hundred()))
+    }
+}
+
+impl Parse for NonNegativeNumberOrPercentage {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(NonNegative(NumberOrPercentage::parse_non_negative(
+            context, input,
+        )?))
+    }
+}
+
+/// The value of Opacity is <alpha-value>, which is "<number> | <percentage>".
+/// However, we serialize the specified value as number, so it's ok to store
+/// the Opacity as Number.
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, PartialEq, PartialOrd, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+pub struct Opacity(Number);
+
+impl Parse for Opacity {
+    /// Opacity accepts <number> | <percentage>, so we parse it as NumberOrPercentage,
+    /// and then convert into an Number if it's a Percentage.
+    /// https://drafts.csswg.org/cssom/#serializing-css-values
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let number = NumberOrPercentage::parse(context, input)?.to_number();
+        Ok(Opacity(number))
+    }
+}
+
+impl ToComputedValue for Opacity {
+    type ComputedValue = CSSFloat;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> CSSFloat {
+        let value = self.0.to_computed_value(context);
+        if context.for_smil_animation {
+            // SMIL expects to be able to interpolate between out-of-range
+            // opacity values.
+            value
+        } else {
+            value.min(1.0).max(0.0)
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &CSSFloat) -> Self {
+        Opacity(Number::from_computed_value(computed))
+    }
+}
+
+/// A specified `<integer>`, optionally coming from a `calc()` expression.
+///
+/// <https://drafts.csswg.org/css-values/#integers>
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, PartialOrd, ToShmem)]
+pub struct Integer {
+    value: CSSInteger,
+    was_calc: bool,
+}
+
+impl Zero for Integer {
+    #[inline]
+    fn zero() -> Self {
+        Self::new(0)
+    }
+
+    #[inline]
+    fn is_zero(&self) -> bool {
+        self.value() == 0
+    }
+}
+
+impl One for Integer {
+    #[inline]
+    fn one() -> Self {
+        Self::new(1)
+    }
+
+    #[inline]
+    fn is_one(&self) -> bool {
+        self.value() == 1
+    }
+}
+
+impl PartialEq<i32> for Integer {
+    fn eq(&self, value: &i32) -> bool {
+        self.value() == *value
+    }
+}
+
+impl Integer {
+    /// Trivially constructs a new `Integer` value.
+    pub fn new(val: CSSInteger) -> Self {
+        Integer {
+            value: val,
+            was_calc: false,
+        }
+    }
+
+    /// Returns the integer value associated with this value.
+    pub fn value(&self) -> CSSInteger {
+        self.value
+    }
+
+    /// Trivially constructs a new integer value from a `calc()` expression.
+    fn from_calc(val: CSSInteger) -> Self {
+        Integer {
+            value: val,
+            was_calc: true,
+        }
+    }
+}
+
+impl Parse for Integer {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        match *input.next()? {
+            Token::Number {
+                int_value: Some(v), ..
+            } => Ok(Integer::new(v)),
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                let result = CalcNode::parse_integer(context, input, function)?;
+                Ok(Integer::from_calc(result))
+            },
+            ref t => Err(location.new_unexpected_token_error(t.clone())),
+        }
+    }
+}
+
+impl Integer {
+    /// Parse an integer value which is at least `min`.
+    pub fn parse_with_minimum<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        min: i32,
+    ) -> Result<Integer, ParseError<'i>> {
+        let value = Integer::parse(context, input)?;
+        // FIXME(emilio): The spec asks us to avoid rejecting it at parse
+        // time except until computed value time.
+        //
+        // It's not totally clear it's worth it though, and no other browser
+        // does this.
+        if value.value() < min {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        Ok(value)
+    }
+
+    /// Parse a non-negative integer.
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Integer, ParseError<'i>> {
+        Integer::parse_with_minimum(context, input, 0)
+    }
+
+    /// Parse a positive integer (>= 1).
+    pub fn parse_positive<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Integer, ParseError<'i>> {
+        Integer::parse_with_minimum(context, input, 1)
+    }
+}
+
+impl ToComputedValue for Integer {
+    type ComputedValue = i32;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> i32 {
+        self.value
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &i32) -> Self {
+        Integer::new(*computed)
+    }
+}
+
+impl ToCss for Integer {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.was_calc {
+            dest.write_str("calc(")?;
+        }
+        self.value.to_css(dest)?;
+        if self.was_calc {
+            dest.write_str(")")?;
+        }
+        Ok(())
+    }
+}
+
+impl SpecifiedValueInfo for Integer {}
+
+/// A wrapper of Integer, with value >= 1.
+pub type PositiveInteger = GreaterThanOrEqualToOne<Integer>;
+
+impl Parse for PositiveInteger {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Integer::parse_positive(context, input).map(GreaterThanOrEqualToOne)
+    }
+}
+
+/// The specified value of a grid `<track-breadth>`
+pub type TrackBreadth = GenericTrackBreadth<LengthPercentage>;
+
+/// The specified value of a grid `<track-size>`
+pub type TrackSize = GenericTrackSize<LengthPercentage>;
+
+/// The specified value of a grid `<track-size>+`
+pub type ImplicitGridTracks = GenericImplicitGridTracks<TrackSize>;
+
+/// The specified value of a grid `<track-list>`
+/// (could also be `<auto-track-list>` or `<explicit-track-list>`)
+pub type TrackList = GenericTrackList<LengthPercentage, Integer>;
+
+/// The specified value of a `<grid-line>`.
+pub type GridLine = GenericGridLine<Integer>;
+
+/// `<grid-template-rows> | <grid-template-columns>`
+pub type GridTemplateComponent = GenericGridTemplateComponent<LengthPercentage, Integer>;
+
+/// rect(...)
+pub type ClipRect = generics::GenericClipRect<LengthOrAuto>;
+
+impl Parse for ClipRect {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl ClipRect {
+    /// Parses a rect(<top>, <left>, <bottom>, <right>), allowing quirks.
+    fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        input.expect_function_matching("rect")?;
+
+        fn parse_argument<'i, 't>(
+            context: &ParserContext,
+            input: &mut Parser<'i, 't>,
+            allow_quirks: AllowQuirks,
+        ) -> Result<LengthOrAuto, ParseError<'i>> {
+            LengthOrAuto::parse_quirky(context, input, allow_quirks)
+        }
+
+        input.parse_nested_block(|input| {
+            let top = parse_argument(context, input, allow_quirks)?;
+            let right;
+            let bottom;
+            let left;
+
+            if input.try_parse(|input| input.expect_comma()).is_ok() {
+                right = parse_argument(context, input, allow_quirks)?;
+                input.expect_comma()?;
+                bottom = parse_argument(context, input, allow_quirks)?;
+                input.expect_comma()?;
+                left = parse_argument(context, input, allow_quirks)?;
+            } else {
+                right = parse_argument(context, input, allow_quirks)?;
+                bottom = parse_argument(context, input, allow_quirks)?;
+                left = parse_argument(context, input, allow_quirks)?;
+            }
+
+            Ok(ClipRect {
+                top,
+                right,
+                bottom,
+                left,
+            })
+        })
+    }
+}
+
+/// rect(...) | auto
+pub type ClipRectOrAuto = generics::GenericClipRectOrAuto<ClipRect>;
+
+impl ClipRectOrAuto {
+    /// Parses a ClipRect or Auto, allowing quirks.
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(v) = input.try_parse(|i| ClipRect::parse_quirky(context, i, allow_quirks)) {
+            return Ok(generics::GenericClipRectOrAuto::Rect(v));
+        }
+        input.expect_ident_matching("auto")?;
+        Ok(generics::GenericClipRectOrAuto::Auto)
+    }
+}
+
+/// Whether quirks are allowed in this context.
+#[derive(Clone, Copy, PartialEq)]
+pub enum AllowQuirks {
+    /// Quirks are not allowed.
+    No,
+    /// Quirks are allowed, in quirks mode.
+    Yes,
+    /// Quirks are always allowed, used for SVG lengths.
+    Always,
+}
+
+impl AllowQuirks {
+    /// Returns `true` if quirks are allowed in this context.
+    pub fn allowed(self, quirks_mode: QuirksMode) -> bool {
+        match self {
+            AllowQuirks::Always => true,
+            AllowQuirks::No => false,
+            AllowQuirks::Yes => quirks_mode == QuirksMode::Quirks,
+        }
+    }
+}
+
+/// An attr(...) rule
+///
+/// `[namespace? `|`]? ident`
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[css(function)]
+#[repr(C)]
+pub struct Attr {
+    /// Optional namespace prefix.
+    pub namespace_prefix: Prefix,
+    /// Optional namespace URL.
+    pub namespace_url: Namespace,
+    /// Attribute name
+    pub attribute: Atom,
+}
+
+impl Parse for Attr {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Attr, ParseError<'i>> {
+        input.expect_function_matching("attr")?;
+        input.parse_nested_block(|i| Attr::parse_function(context, i))
+    }
+}
+
+/// Get the Namespace for a given prefix from the namespace map.
+fn get_namespace_for_prefix(prefix: &Prefix, context: &ParserContext) -> Option<Namespace> {
+    context
+        .namespaces
+        .as_ref()?
+        .prefixes
+        .get(prefix)
+        .map(|x| x.clone())
+}
+
+impl Attr {
+    /// Parse contents of attr() assuming we have already parsed `attr` and are
+    /// within a parse_nested_block()
+    pub fn parse_function<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Attr, ParseError<'i>> {
+        // Syntax is `[namespace? `|`]? ident`
+        // no spaces allowed
+        let first = input.try_parse(|i| i.expect_ident_cloned()).ok();
+        if let Ok(token) = input.try_parse(|i| i.next_including_whitespace().map(|t| t.clone())) {
+            match token {
+                Token::Delim('|') => {
+                    let location = input.current_source_location();
+                    // must be followed by an ident
+                    let second_token = match *input.next_including_whitespace()? {
+                        Token::Ident(ref second) => second,
+                        ref t => return Err(location.new_unexpected_token_error(t.clone())),
+                    };
+
+                    let (namespace_prefix, namespace_url) = if let Some(ns) = first {
+                        let prefix = Prefix::from(ns.as_ref());
+                        let ns = match get_namespace_for_prefix(&prefix, context) {
+                            Some(ns) => ns,
+                            None => {
+                                return Err(location
+                                    .new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                            },
+                        };
+                        (prefix, ns)
+                    } else {
+                        (Prefix::default(), Namespace::default())
+                    };
+                    return Ok(Attr {
+                        namespace_prefix,
+                        namespace_url,
+                        attribute: Atom::from(second_token.as_ref()),
+                    });
+                },
+                // In the case of attr(foobar    ) we don't want to error out
+                // because of the trailing whitespace.
+                Token::WhiteSpace(..) => {},
+                ref t => return Err(input.new_unexpected_token_error(t.clone())),
+            }
+        }
+
+        if let Some(first) = first {
+            Ok(Attr {
+                namespace_prefix: Prefix::default(),
+                namespace_url: Namespace::default(),
+                attribute: Atom::from(first.as_ref()),
+            })
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+impl ToCss for Attr {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str("attr(")?;
+        if !self.namespace_prefix.is_empty() {
+            serialize_atom_identifier(&self.namespace_prefix, dest)?;
+            dest.write_str("|")?;
+        }
+        serialize_atom_identifier(&self.attribute, dest)?;
+        dest.write_str(")")
+    }
+}
diff --git a/servo/components/style/values/specified/motion.rs b/servo/components/style/values/specified/motion.rs
new file mode 100644
index 0000000000..944a011084
--- /dev/null
+++ b/servo/components/style/values/specified/motion.rs
@@ -0,0 +1,222 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS values that are related to motion path.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::motion::OffsetRotate as ComputedOffsetRotate;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics::motion::{GenericOffsetPath, RayFunction, RaySize};
+use crate::values::specified::{Angle, SVGPathData};
+use crate::Zero;
+use cssparser::Parser;
+use style_traits::{ParseError, StyleParseErrorKind};
+
+/// The specified value of `offset-path`.
+pub type OffsetPath = GenericOffsetPath<Angle>;
+
+#[cfg(feature = "gecko")]
+fn is_ray_enabled() -> bool {
+    static_prefs::pref!("layout.css.motion-path-ray.enabled")
+}
+#[cfg(feature = "servo")]
+fn is_ray_enabled() -> bool {
+    false
+}
+
+impl Parse for RayFunction<Angle> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if !is_ray_enabled() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        let mut angle = None;
+        let mut size = None;
+        let mut contain = false;
+        loop {
+            if angle.is_none() {
+                angle = input.try_parse(|i| Angle::parse(context, i)).ok();
+            }
+
+            if size.is_none() {
+                size = input.try_parse(RaySize::parse).ok();
+                if size.is_some() {
+                    continue;
+                }
+            }
+
+            if !contain {
+                contain = input
+                    .try_parse(|i| i.expect_ident_matching("contain"))
+                    .is_ok();
+                if contain {
+                    continue;
+                }
+            }
+            break;
+        }
+
+        if angle.is_none() || size.is_none() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(RayFunction {
+            angle: angle.unwrap(),
+            size: size.unwrap(),
+            contain,
+        })
+    }
+}
+
+impl Parse for OffsetPath {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // Parse none.
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(OffsetPath::none());
+        }
+
+        // Parse possible functions.
+        let location = input.current_source_location();
+        let function = input.expect_function()?.clone();
+        input.parse_nested_block(move |i| {
+            match_ignore_ascii_case! { &function,
+                // Bug 1186329: Implement the parser for <basic-shape>, <geometry-box>,
+                // and <url>.
+                "path" => SVGPathData::parse(context, i).map(GenericOffsetPath::Path),
+                "ray" => RayFunction::parse(context, i).map(GenericOffsetPath::Ray),
+                _ => {
+                    Err(location.new_custom_error(
+                        StyleParseErrorKind::UnexpectedFunction(function.clone())
+                    ))
+                },
+            }
+        })
+    }
+}
+
+/// The direction of offset-rotate.
+#[derive(
+    Clone, Copy, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+#[repr(u8)]
+pub enum OffsetRotateDirection {
+    /// Unspecified direction keyword.
+    #[css(skip)]
+    None,
+    /// 0deg offset (face forward).
+    Auto,
+    /// 180deg offset (face backward).
+    Reverse,
+}
+
+impl OffsetRotateDirection {
+    /// Returns true if it is none (i.e. the keyword is not specified).
+    #[inline]
+    fn is_none(&self) -> bool {
+        *self == OffsetRotateDirection::None
+    }
+}
+
+#[inline]
+fn direction_specified_and_angle_is_zero(direction: &OffsetRotateDirection, angle: &Angle) -> bool {
+    !direction.is_none() && angle.is_zero()
+}
+
+/// The specified offset-rotate.
+/// The syntax is: "[ auto | reverse ] || <angle>"
+///
+/// https://drafts.fxtf.org/motion-1/#offset-rotate-property
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub struct OffsetRotate {
+    /// [auto | reverse].
+    #[css(skip_if = "OffsetRotateDirection::is_none")]
+    direction: OffsetRotateDirection,
+    /// <angle>.
+    /// If direction is None, this is a fixed angle which indicates a
+    /// constant clockwise rotation transformation applied to it by this
+    /// specified rotation angle. Otherwise, the angle will be added to
+    /// the angle of the direction in layout.
+    #[css(contextual_skip_if = "direction_specified_and_angle_is_zero")]
+    angle: Angle,
+}
+
+impl OffsetRotate {
+    /// Returns the initial value, auto.
+    #[inline]
+    pub fn auto() -> Self {
+        OffsetRotate {
+            direction: OffsetRotateDirection::Auto,
+            angle: Angle::zero(),
+        }
+    }
+
+    /// Returns true if self is auto 0deg.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        self.direction == OffsetRotateDirection::Auto && self.angle.is_zero()
+    }
+}
+
+impl Parse for OffsetRotate {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let mut direction = input.try_parse(OffsetRotateDirection::parse);
+        let angle = input.try_parse(|i| Angle::parse(context, i));
+        if direction.is_err() {
+            // The direction and angle could be any order, so give it a change to parse
+            // direction again.
+            direction = input.try_parse(OffsetRotateDirection::parse);
+        }
+
+        if direction.is_err() && angle.is_err() {
+            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(OffsetRotate {
+            direction: direction.unwrap_or(OffsetRotateDirection::None),
+            angle: angle.unwrap_or(Zero::zero()),
+        })
+    }
+}
+
+impl ToComputedValue for OffsetRotate {
+    type ComputedValue = ComputedOffsetRotate;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        use crate::values::computed::Angle as ComputedAngle;
+
+        ComputedOffsetRotate {
+            auto: !self.direction.is_none(),
+            angle: if self.direction == OffsetRotateDirection::Reverse {
+                // The computed value should always convert "reverse" into "auto".
+                // e.g. "reverse calc(20deg + 10deg)" => "auto 210deg"
+                self.angle.to_computed_value(context) + ComputedAngle::from_degrees(180.0)
+            } else {
+                self.angle.to_computed_value(context)
+            },
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        OffsetRotate {
+            direction: if computed.auto {
+                OffsetRotateDirection::Auto
+            } else {
+                OffsetRotateDirection::None
+            },
+            angle: ToComputedValue::from_computed_value(&computed.angle),
+        }
+    }
+}
diff --git a/servo/components/style/values/specified/outline.rs b/servo/components/style/values/specified/outline.rs
new file mode 100644
index 0000000000..6e5382d4c2
--- /dev/null
+++ b/servo/components/style/values/specified/outline.rs
@@ -0,0 +1,71 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified values for outline properties
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::specified::BorderStyle;
+use cssparser::Parser;
+use selectors::parser::SelectorParseErrorKind;
+use style_traits::ParseError;
+
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Ord,
+    PartialEq,
+    PartialOrd,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+/// <https://drafts.csswg.org/css-ui/#propdef-outline-style>
+pub enum OutlineStyle {
+    /// auto
+    Auto,
+    /// <border-style>
+    BorderStyle(BorderStyle),
+}
+
+impl OutlineStyle {
+    #[inline]
+    /// Get default value as None
+    pub fn none() -> OutlineStyle {
+        OutlineStyle::BorderStyle(BorderStyle::None)
+    }
+
+    #[inline]
+    /// Get value for None or Hidden
+    pub fn none_or_hidden(&self) -> bool {
+        match *self {
+            OutlineStyle::Auto => false,
+            OutlineStyle::BorderStyle(ref style) => style.none_or_hidden(),
+        }
+    }
+}
+
+impl Parse for OutlineStyle {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<OutlineStyle, ParseError<'i>> {
+        if let Ok(border_style) = input.try_parse(BorderStyle::parse) {
+            if let BorderStyle::Hidden = border_style {
+                return Err(input
+                    .new_custom_error(SelectorParseErrorKind::UnexpectedIdent("hidden".into())));
+            }
+
+            return Ok(OutlineStyle::BorderStyle(border_style));
+        }
+
+        input.expect_ident_matching("auto")?;
+        Ok(OutlineStyle::Auto)
+    }
+}
diff --git a/servo/components/style/values/specified/page.rs b/servo/components/style/values/specified/page.rs
new file mode 100644
index 0000000000..f8727a9c1d
--- /dev/null
+++ b/servo/components/style/values/specified/page.rs
@@ -0,0 +1,98 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified @page at-rule properties and named-page style properties
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::size::Size2D;
+use crate::values::specified::length::NonNegativeLength;
+use crate::values::{generics, CustomIdent};
+use cssparser::Parser;
+use style_traits::ParseError;
+
+pub use generics::page::PageSizeOrientation;
+pub use generics::page::PaperSize;
+/// Specified value of the @page size descriptor
+pub type PageSize = generics::page::PageSize<Size2D<NonNegativeLength>>;
+
+impl Parse for PageSize {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // Try to parse as <page-size> [ <orientation> ]
+        if let Ok(paper_size) = input.try_parse(PaperSize::parse) {
+            let orientation = input
+                .try_parse(PageSizeOrientation::parse)
+                .unwrap_or(PageSizeOrientation::Portrait);
+            return Ok(PageSize::PaperSize(paper_size, orientation));
+        }
+        // Try to parse as <orientation> [ <page-size> ]
+        if let Ok(orientation) = input.try_parse(PageSizeOrientation::parse) {
+            if let Ok(paper_size) = input.try_parse(PaperSize::parse) {
+                return Ok(PageSize::PaperSize(paper_size, orientation));
+            }
+            return Ok(PageSize::Orientation(orientation));
+        }
+        // Try to parse dimensions
+        if let Ok(size) =
+            input.try_parse(|i| Size2D::parse_with(context, i, NonNegativeLength::parse))
+        {
+            return Ok(PageSize::Size(size));
+        }
+        // auto value
+        input.expect_ident_matching("auto")?;
+        Ok(PageSize::Auto)
+    }
+}
+
+/// Page name value.
+///
+/// https://drafts.csswg.org/css-page-3/#using-named-pages
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum PageName {
+    /// `auto` value.
+    Auto,
+    /// Page name value
+    PageName(CustomIdent),
+}
+
+impl Parse for PageName {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let ident = input.expect_ident()?;
+        Ok(match_ignore_ascii_case! { ident,
+            "auto" => PageName::auto(),
+            _ => PageName::PageName(CustomIdent::from_ident(location, ident, &[])?),
+        })
+    }
+}
+
+impl PageName {
+    /// `auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        PageName::Auto
+    }
+
+    /// Whether this is the `auto` value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, PageName::Auto)
+    }
+}
diff --git a/servo/components/style/values/specified/percentage.rs b/servo/components/style/values/specified/percentage.rs
new file mode 100644
index 0000000000..ba5f92db92
--- /dev/null
+++ b/servo/components/style/values/specified/percentage.rs
@@ -0,0 +1,225 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified percentages.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::percentage::Percentage as ComputedPercentage;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics::NonNegative;
+use crate::values::specified::calc::CalcNode;
+use crate::values::specified::Number;
+use crate::values::{serialize_percentage, CSSFloat};
+use cssparser::{Parser, Token};
+use std::fmt::{self, Write};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, ToCss};
+
+/// A percentage value.
+#[derive(Clone, Copy, Debug, Default, MallocSizeOf, PartialEq, ToShmem)]
+pub struct Percentage {
+    /// The percentage value as a float.
+    ///
+    /// [0 .. 100%] maps to [0.0 .. 1.0]
+    value: CSSFloat,
+    /// If this percentage came from a calc() expression, this tells how
+    /// clamping should be done on the value.
+    calc_clamping_mode: Option<AllowedNumericType>,
+}
+
+impl ToCss for Percentage {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.calc_clamping_mode.is_some() {
+            dest.write_str("calc(")?;
+        }
+
+        serialize_percentage(self.value, dest)?;
+
+        if self.calc_clamping_mode.is_some() {
+            dest.write_str(")")?;
+        }
+        Ok(())
+    }
+}
+
+impl Percentage {
+    /// Creates a percentage from a numeric value.
+    pub(super) fn new_with_clamping_mode(
+        value: CSSFloat,
+        calc_clamping_mode: Option<AllowedNumericType>,
+    ) -> Self {
+        Self {
+            value,
+            calc_clamping_mode,
+        }
+    }
+
+    /// Creates a percentage from a numeric value.
+    pub fn new(value: CSSFloat) -> Self {
+        Self::new_with_clamping_mode(value, None)
+    }
+
+    /// `0%`
+    #[inline]
+    pub fn zero() -> Self {
+        Percentage {
+            value: 0.,
+            calc_clamping_mode: None,
+        }
+    }
+
+    /// `100%`
+    #[inline]
+    pub fn hundred() -> Self {
+        Percentage {
+            value: 1.,
+            calc_clamping_mode: None,
+        }
+    }
+
+    /// Gets the underlying value for this float.
+    pub fn get(&self) -> CSSFloat {
+        self.calc_clamping_mode
+            .map_or(self.value, |mode| mode.clamp(self.value))
+    }
+
+    /// Returns this percentage as a number.
+    pub fn to_number(&self) -> Number {
+        Number::new_with_clamping_mode(self.value, self.calc_clamping_mode)
+    }
+
+    /// Returns the calc() clamping mode for this percentage.
+    pub fn calc_clamping_mode(&self) -> Option<AllowedNumericType> {
+        self.calc_clamping_mode
+    }
+
+    /// Reverses this percentage, preserving calc-ness.
+    ///
+    /// For example: If it was 20%, convert it into 80%.
+    pub fn reverse(&mut self) {
+        let new_value = 1. - self.value;
+        self.value = new_value;
+    }
+
+    /// Parses a specific kind of percentage.
+    pub fn parse_with_clamping_mode<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        num_context: AllowedNumericType,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        match *input.next()? {
+            Token::Percentage { unit_value, .. }
+                if num_context.is_ok(context.parsing_mode, unit_value) =>
+            {
+                Ok(Percentage::new(unit_value))
+            },
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                let value = CalcNode::parse_percentage(context, input, function)?;
+                Ok(Percentage {
+                    value,
+                    calc_clamping_mode: Some(num_context),
+                })
+            },
+            ref t => Err(location.new_unexpected_token_error(t.clone())),
+        }
+    }
+
+    /// Parses a percentage token, but rejects it if it's negative.
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+    }
+
+    /// Parses a percentage token, but rejects it if it's negative or more than
+    /// 100%.
+    pub fn parse_zero_to_a_hundred<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::ZeroToOne)
+    }
+
+    /// Clamp to 100% if the value is over 100%.
+    #[inline]
+    pub fn clamp_to_hundred(self) -> Self {
+        Percentage {
+            value: self.value.min(1.),
+            calc_clamping_mode: self.calc_clamping_mode,
+        }
+    }
+}
+
+impl Parse for Percentage {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::All)
+    }
+}
+
+impl ToComputedValue for Percentage {
+    type ComputedValue = ComputedPercentage;
+
+    #[inline]
+    fn to_computed_value(&self, _: &Context) -> Self::ComputedValue {
+        ComputedPercentage(self.get())
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Percentage::new(computed.0)
+    }
+}
+
+impl SpecifiedValueInfo for Percentage {}
+
+/// Turns the percentage into a plain float.
+pub trait ToPercentage {
+    /// Returns whether this percentage used to be a calc().
+    fn is_calc(&self) -> bool {
+        false
+    }
+    /// Turns the percentage into a plain float.
+    fn to_percentage(&self) -> CSSFloat;
+}
+
+impl ToPercentage for Percentage {
+    fn is_calc(&self) -> bool {
+        self.calc_clamping_mode.is_some()
+    }
+
+    fn to_percentage(&self) -> CSSFloat {
+        self.get()
+    }
+}
+
+/// A wrapper of Percentage, whose value must be >= 0.
+pub type NonNegativePercentage = NonNegative<Percentage>;
+
+impl Parse for NonNegativePercentage {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(NonNegative(Percentage::parse_non_negative(context, input)?))
+    }
+}
+
+impl NonNegativePercentage {
+    /// Convert to ComputedPercentage, for FontFaceRule size-adjust getter.
+    #[inline]
+    pub fn compute(&self) -> ComputedPercentage {
+        ComputedPercentage(self.0.get())
+    }
+}
diff --git a/servo/components/style/values/specified/position.rs b/servo/components/style/values/specified/position.rs
new file mode 100644
index 0000000000..e447c52f0c
--- /dev/null
+++ b/servo/components/style/values/specified/position.rs
@@ -0,0 +1,911 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! CSS handling for the specified value of
+//! [`position`][position]s
+//!
+//! [position]: https://drafts.csswg.org/css-backgrounds-3/#position
+
+use crate::parser::{Parse, ParserContext};
+use crate::selector_map::PrecomputedHashMap;
+use crate::str::HTML_SPACE_CHARACTERS;
+use crate::values::computed::LengthPercentage as ComputedLengthPercentage;
+use crate::values::computed::{Context, Percentage, ToComputedValue};
+use crate::values::generics::position::AspectRatio as GenericAspectRatio;
+use crate::values::generics::position::Position as GenericPosition;
+use crate::values::generics::position::PositionComponent as GenericPositionComponent;
+use crate::values::generics::position::PositionOrAuto as GenericPositionOrAuto;
+use crate::values::generics::position::ZIndex as GenericZIndex;
+use crate::values::specified::{AllowQuirks, Integer, LengthPercentage, NonNegativeNumber};
+use crate::{Atom, Zero};
+use cssparser::Parser;
+use selectors::parser::SelectorParseErrorKind;
+use servo_arc::Arc;
+use std::fmt::{self, Write};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+
+/// The specified value of a CSS `<position>`
+pub type Position = GenericPosition<HorizontalPosition, VerticalPosition>;
+
+/// The specified value of an `auto | <position>`.
+pub type PositionOrAuto = GenericPositionOrAuto<Position>;
+
+/// The specified value of a horizontal position.
+pub type HorizontalPosition = PositionComponent<HorizontalPositionKeyword>;
+
+/// The specified value of a vertical position.
+pub type VerticalPosition = PositionComponent<VerticalPositionKeyword>;
+
+/// The specified value of a component of a CSS `<position>`.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum PositionComponent<S> {
+    /// `center`
+    Center,
+    /// `<length-percentage>`
+    Length(LengthPercentage),
+    /// `<side> <length-percentage>?`
+    Side(S, Option<LengthPercentage>),
+}
+
+/// A keyword for the X direction.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[repr(u8)]
+pub enum HorizontalPositionKeyword {
+    Left,
+    Right,
+}
+
+/// A keyword for the Y direction.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[repr(u8)]
+pub enum VerticalPositionKeyword {
+    Top,
+    Bottom,
+}
+
+impl Parse for Position {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let position = Self::parse_three_value_quirky(context, input, AllowQuirks::No)?;
+        if position.is_three_value_syntax() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+        Ok(position)
+    }
+}
+
+impl Position {
+    /// Parses a `<bg-position>`, with quirks.
+    pub fn parse_three_value_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        match input.try_parse(|i| PositionComponent::parse_quirky(context, i, allow_quirks)) {
+            Ok(x_pos @ PositionComponent::Center) => {
+                if let Ok(y_pos) =
+                    input.try_parse(|i| PositionComponent::parse_quirky(context, i, allow_quirks))
+                {
+                    return Ok(Self::new(x_pos, y_pos));
+                }
+                let x_pos = input
+                    .try_parse(|i| PositionComponent::parse_quirky(context, i, allow_quirks))
+                    .unwrap_or(x_pos);
+                let y_pos = PositionComponent::Center;
+                return Ok(Self::new(x_pos, y_pos));
+            },
+            Ok(PositionComponent::Side(x_keyword, lp)) => {
+                if input
+                    .try_parse(|i| i.expect_ident_matching("center"))
+                    .is_ok()
+                {
+                    let x_pos = PositionComponent::Side(x_keyword, lp);
+                    let y_pos = PositionComponent::Center;
+                    return Ok(Self::new(x_pos, y_pos));
+                }
+                if let Ok(y_keyword) = input.try_parse(VerticalPositionKeyword::parse) {
+                    let y_lp = input
+                        .try_parse(|i| LengthPercentage::parse_quirky(context, i, allow_quirks))
+                        .ok();
+                    let x_pos = PositionComponent::Side(x_keyword, lp);
+                    let y_pos = PositionComponent::Side(y_keyword, y_lp);
+                    return Ok(Self::new(x_pos, y_pos));
+                }
+                let x_pos = PositionComponent::Side(x_keyword, None);
+                let y_pos = lp.map_or(PositionComponent::Center, PositionComponent::Length);
+                return Ok(Self::new(x_pos, y_pos));
+            },
+            Ok(x_pos @ PositionComponent::Length(_)) => {
+                if let Ok(y_keyword) = input.try_parse(VerticalPositionKeyword::parse) {
+                    let y_pos = PositionComponent::Side(y_keyword, None);
+                    return Ok(Self::new(x_pos, y_pos));
+                }
+                if let Ok(y_lp) =
+                    input.try_parse(|i| LengthPercentage::parse_quirky(context, i, allow_quirks))
+                {
+                    let y_pos = PositionComponent::Length(y_lp);
+                    return Ok(Self::new(x_pos, y_pos));
+                }
+                let y_pos = PositionComponent::Center;
+                let _ = input.try_parse(|i| i.expect_ident_matching("center"));
+                return Ok(Self::new(x_pos, y_pos));
+            },
+            Err(_) => {},
+        }
+        let y_keyword = VerticalPositionKeyword::parse(input)?;
+        let lp_and_x_pos: Result<_, ParseError> = input.try_parse(|i| {
+            let y_lp = i
+                .try_parse(|i| LengthPercentage::parse_quirky(context, i, allow_quirks))
+                .ok();
+            if let Ok(x_keyword) = i.try_parse(HorizontalPositionKeyword::parse) {
+                let x_lp = i
+                    .try_parse(|i| LengthPercentage::parse_quirky(context, i, allow_quirks))
+                    .ok();
+                let x_pos = PositionComponent::Side(x_keyword, x_lp);
+                return Ok((y_lp, x_pos));
+            };
+            i.expect_ident_matching("center")?;
+            let x_pos = PositionComponent::Center;
+            Ok((y_lp, x_pos))
+        });
+        if let Ok((y_lp, x_pos)) = lp_and_x_pos {
+            let y_pos = PositionComponent::Side(y_keyword, y_lp);
+            return Ok(Self::new(x_pos, y_pos));
+        }
+        let x_pos = PositionComponent::Center;
+        let y_pos = PositionComponent::Side(y_keyword, None);
+        Ok(Self::new(x_pos, y_pos))
+    }
+
+    /// `center center`
+    #[inline]
+    pub fn center() -> Self {
+        Self::new(PositionComponent::Center, PositionComponent::Center)
+    }
+
+    /// Returns true if this uses a 3 value syntax.
+    #[inline]
+    fn is_three_value_syntax(&self) -> bool {
+        self.horizontal.component_count() != self.vertical.component_count()
+    }
+}
+
+impl ToCss for Position {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        match (&self.horizontal, &self.vertical) {
+            (
+                x_pos @ &PositionComponent::Side(_, Some(_)),
+                &PositionComponent::Length(ref y_lp),
+            ) => {
+                x_pos.to_css(dest)?;
+                dest.write_str(" top ")?;
+                y_lp.to_css(dest)
+            },
+            (
+                &PositionComponent::Length(ref x_lp),
+                y_pos @ &PositionComponent::Side(_, Some(_)),
+            ) => {
+                dest.write_str("left ")?;
+                x_lp.to_css(dest)?;
+                dest.write_str(" ")?;
+                y_pos.to_css(dest)
+            },
+            (x_pos, y_pos) => {
+                x_pos.to_css(dest)?;
+                dest.write_str(" ")?;
+                y_pos.to_css(dest)
+            },
+        }
+    }
+}
+
+impl<S: Parse> Parse for PositionComponent<S> {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_quirky(context, input, AllowQuirks::No)
+    }
+}
+
+impl<S: Parse> PositionComponent<S> {
+    /// Parses a component of a CSS position, with quirks.
+    pub fn parse_quirky<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        allow_quirks: AllowQuirks,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|i| i.expect_ident_matching("center"))
+            .is_ok()
+        {
+            return Ok(PositionComponent::Center);
+        }
+        if let Ok(lp) =
+            input.try_parse(|i| LengthPercentage::parse_quirky(context, i, allow_quirks))
+        {
+            return Ok(PositionComponent::Length(lp));
+        }
+        let keyword = S::parse(context, input)?;
+        let lp = input
+            .try_parse(|i| LengthPercentage::parse_quirky(context, i, allow_quirks))
+            .ok();
+        Ok(PositionComponent::Side(keyword, lp))
+    }
+}
+
+impl<S> GenericPositionComponent for PositionComponent<S> {
+    fn is_center(&self) -> bool {
+        match *self {
+            PositionComponent::Center => true,
+            PositionComponent::Length(LengthPercentage::Percentage(ref per)) => per.0 == 0.5,
+            // 50% from any side is still the center.
+            PositionComponent::Side(_, Some(LengthPercentage::Percentage(ref per))) => per.0 == 0.5,
+            _ => false,
+        }
+    }
+}
+
+impl<S> PositionComponent<S> {
+    /// `0%`
+    pub fn zero() -> Self {
+        PositionComponent::Length(LengthPercentage::Percentage(Percentage::zero()))
+    }
+
+    /// Returns the count of this component.
+    fn component_count(&self) -> usize {
+        match *self {
+            PositionComponent::Length(..) | PositionComponent::Center => 1,
+            PositionComponent::Side(_, ref lp) => {
+                if lp.is_some() {
+                    2
+                } else {
+                    1
+                }
+            },
+        }
+    }
+}
+
+impl<S: Side> ToComputedValue for PositionComponent<S> {
+    type ComputedValue = ComputedLengthPercentage;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            PositionComponent::Center => ComputedLengthPercentage::new_percent(Percentage(0.5)),
+            PositionComponent::Side(ref keyword, None) => {
+                let p = Percentage(if keyword.is_start() { 0. } else { 1. });
+                ComputedLengthPercentage::new_percent(p)
+            },
+            PositionComponent::Side(ref keyword, Some(ref length)) if !keyword.is_start() => {
+                let length = length.to_computed_value(context);
+                // We represent `<end-side> <length>` as `calc(100% - <length>)`.
+                ComputedLengthPercentage::hundred_percent_minus(length, AllowedNumericType::All)
+            },
+            PositionComponent::Side(_, Some(ref length)) |
+            PositionComponent::Length(ref length) => length.to_computed_value(context),
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        PositionComponent::Length(ToComputedValue::from_computed_value(computed))
+    }
+}
+
+impl<S: Side> PositionComponent<S> {
+    /// The initial specified value of a position component, i.e. the start side.
+    pub fn initial_specified_value() -> Self {
+        PositionComponent::Side(S::start(), None)
+    }
+}
+
+/// Represents a side, either horizontal or vertical, of a CSS position.
+pub trait Side {
+    /// Returns the start side.
+    fn start() -> Self;
+
+    /// Returns whether this side is the start side.
+    fn is_start(&self) -> bool;
+}
+
+impl Side for HorizontalPositionKeyword {
+    #[inline]
+    fn start() -> Self {
+        HorizontalPositionKeyword::Left
+    }
+
+    #[inline]
+    fn is_start(&self) -> bool {
+        *self == Self::start()
+    }
+}
+
+impl Side for VerticalPositionKeyword {
+    #[inline]
+    fn start() -> Self {
+        VerticalPositionKeyword::Top
+    }
+
+    #[inline]
+    fn is_start(&self) -> bool {
+        *self == Self::start()
+    }
+}
+
+bitflags! {
+    /// Controls how the auto-placement algorithm works
+    /// specifying exactly how auto-placed items get flowed into the grid
+    #[derive(
+        MallocSizeOf,
+        SpecifiedValueInfo,
+        ToComputedValue,
+        ToResolvedValue,
+        ToShmem
+    )]
+    #[value_info(other_values = "row,column,dense")]
+    #[repr(C)]
+    pub struct GridAutoFlow: u8 {
+        /// 'row' - mutually exclusive with 'column'
+        const ROW = 1 << 0;
+        /// 'column' - mutually exclusive with 'row'
+        const COLUMN = 1 << 1;
+        /// 'dense'
+        const DENSE = 1 << 2;
+    }
+}
+
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+/// Masonry auto-placement algorithm packing.
+pub enum MasonryPlacement {
+    /// Place the item in the track(s) with the smallest extent so far.
+    Pack,
+    /// Place the item after the last item, from start to end.
+    Next,
+}
+
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+/// Masonry auto-placement algorithm item sorting option.
+pub enum MasonryItemOrder {
+    /// Place all items with a definite placement before auto-placed items.
+    DefiniteFirst,
+    /// Place items in `order-modified document order`.
+    Ordered,
+}
+
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// Controls how the Masonry layout algorithm works
+/// specifying exactly how auto-placed items get flowed in the masonry axis.
+pub struct MasonryAutoFlow {
+    /// Specify how to pick a auto-placement track.
+    #[css(contextual_skip_if = "is_pack_with_non_default_order")]
+    pub placement: MasonryPlacement,
+    /// Specify how to pick an item to place.
+    #[css(skip_if = "is_item_order_definite_first")]
+    pub order: MasonryItemOrder,
+}
+
+#[inline]
+fn is_pack_with_non_default_order(placement: &MasonryPlacement, order: &MasonryItemOrder) -> bool {
+    *placement == MasonryPlacement::Pack && *order != MasonryItemOrder::DefiniteFirst
+}
+
+#[inline]
+fn is_item_order_definite_first(order: &MasonryItemOrder) -> bool {
+    *order == MasonryItemOrder::DefiniteFirst
+}
+
+impl MasonryAutoFlow {
+    #[inline]
+    /// Get initial `masonry-auto-flow` value.
+    pub fn initial() -> MasonryAutoFlow {
+        MasonryAutoFlow {
+            placement: MasonryPlacement::Pack,
+            order: MasonryItemOrder::DefiniteFirst,
+        }
+    }
+}
+
+impl Parse for MasonryAutoFlow {
+    /// [ definite-first | ordered ] || [ pack | next ]
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<MasonryAutoFlow, ParseError<'i>> {
+        let mut value = MasonryAutoFlow::initial();
+        let mut got_placement = false;
+        let mut got_order = false;
+        while !input.is_exhausted() {
+            let location = input.current_source_location();
+            let ident = input.expect_ident()?;
+            let success = match_ignore_ascii_case! { &ident,
+                "pack" if !got_placement => {
+                    got_placement = true;
+                    true
+                },
+                "next" if !got_placement => {
+                    value.placement = MasonryPlacement::Next;
+                    got_placement = true;
+                    true
+                },
+                "definite-first" if !got_order => {
+                    got_order = true;
+                    true
+                },
+                "ordered" if !got_order => {
+                    value.order = MasonryItemOrder::Ordered;
+                    got_order = true;
+                    true
+                },
+                _ => false
+            };
+            if !success {
+                return Err(location
+                    .new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())));
+            }
+        }
+
+        if got_placement || got_order {
+            Ok(value)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+// TODO: Can be derived with some care.
+impl Parse for GridAutoFlow {
+    /// [ row | column ] || dense
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<GridAutoFlow, ParseError<'i>> {
+        let mut track = None;
+        let mut dense = GridAutoFlow::empty();
+
+        while !input.is_exhausted() {
+            let location = input.current_source_location();
+            let ident = input.expect_ident()?;
+            let success = match_ignore_ascii_case! { &ident,
+                "row" if track.is_none() => {
+                    track = Some(GridAutoFlow::ROW);
+                    true
+                },
+                "column" if track.is_none() => {
+                    track = Some(GridAutoFlow::COLUMN);
+                    true
+                },
+                "dense" if dense.is_empty() => {
+                    dense = GridAutoFlow::DENSE;
+                    true
+                },
+                _ => false,
+            };
+            if !success {
+                return Err(location
+                    .new_custom_error(SelectorParseErrorKind::UnexpectedIdent(ident.clone())));
+            }
+        }
+
+        if track.is_some() || !dense.is_empty() {
+            Ok(track.unwrap_or(GridAutoFlow::ROW) | dense)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+impl ToCss for GridAutoFlow {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if *self == GridAutoFlow::ROW {
+            return dest.write_str("row");
+        }
+
+        if *self == GridAutoFlow::COLUMN {
+            return dest.write_str("column");
+        }
+
+        if *self == GridAutoFlow::ROW | GridAutoFlow::DENSE {
+            return dest.write_str("dense");
+        }
+
+        if *self == GridAutoFlow::COLUMN | GridAutoFlow::DENSE {
+            return dest.write_str("column dense");
+        }
+
+        debug_assert!(false, "Unknown or invalid grid-autoflow value");
+        Ok(())
+    }
+}
+
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// https://drafts.csswg.org/css-grid/#named-grid-area
+pub struct TemplateAreas {
+    /// `named area` containing for each template area
+    #[css(skip)]
+    pub areas: crate::OwnedSlice<NamedArea>,
+    /// The original CSS string value of each template area
+    #[css(iterable)]
+    pub strings: crate::OwnedSlice<crate::OwnedStr>,
+    /// The number of columns of the grid.
+    #[css(skip)]
+    pub width: u32,
+}
+
+impl TemplateAreas {
+    /// Transform `vector` of str into `template area`
+    pub fn from_vec(strings: Vec<crate::OwnedStr>) -> Result<Self, ()> {
+        if strings.is_empty() {
+            return Err(());
+        }
+        let mut areas: Vec<NamedArea> = vec![];
+        let mut width = 0;
+        {
+            let mut row = 0u32;
+            let mut area_indices = PrecomputedHashMap::<Atom, usize>::default();
+            for string in &strings {
+                let mut current_area_index: Option<usize> = None;
+                row += 1;
+                let mut column = 0u32;
+                for token in TemplateAreasTokenizer(string) {
+                    column += 1;
+                    let name = if let Some(token) = token? {
+                        Atom::from(token)
+                    } else {
+                        if let Some(index) = current_area_index.take() {
+                            if areas[index].columns.end != column {
+                                return Err(());
+                            }
+                        }
+                        continue;
+                    };
+                    if let Some(index) = current_area_index {
+                        if areas[index].name == name {
+                            if areas[index].rows.start == row {
+                                areas[index].columns.end += 1;
+                            }
+                            continue;
+                        }
+                        if areas[index].columns.end != column {
+                            return Err(());
+                        }
+                    }
+                    if let Some(index) = area_indices.get(&name).cloned() {
+                        if areas[index].columns.start != column || areas[index].rows.end != row {
+                            return Err(());
+                        }
+                        areas[index].rows.end += 1;
+                        current_area_index = Some(index);
+                        continue;
+                    }
+                    let index = areas.len();
+                    assert!(area_indices.insert(name.clone(), index).is_none());
+                    areas.push(NamedArea {
+                        name,
+                        columns: UnsignedRange {
+                            start: column,
+                            end: column + 1,
+                        },
+                        rows: UnsignedRange {
+                            start: row,
+                            end: row + 1,
+                        },
+                    });
+                    current_area_index = Some(index);
+                }
+                if column == 0 {
+                    // Each string must produce a valid token.
+                    // https://github.com/w3c/csswg-drafts/issues/5110
+                    return Err(());
+                }
+                if let Some(index) = current_area_index {
+                    if areas[index].columns.end != column + 1 {
+                        assert_ne!(areas[index].rows.start, row);
+                        return Err(());
+                    }
+                }
+                if row == 1 {
+                    width = column;
+                } else if width != column {
+                    return Err(());
+                }
+            }
+        }
+        Ok(TemplateAreas {
+            areas: areas.into(),
+            strings: strings.into(),
+            width,
+        })
+    }
+}
+
+impl Parse for TemplateAreas {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut strings = vec![];
+        while let Ok(string) =
+            input.try_parse(|i| i.expect_string().map(|s| s.as_ref().to_owned().into()))
+        {
+            strings.push(string);
+        }
+
+        TemplateAreas::from_vec(strings)
+            .map_err(|()| input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+    }
+}
+
+/// Arc type for `Arc<TemplateAreas>`
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct TemplateAreasArc(#[ignore_malloc_size_of = "Arc"] pub Arc<TemplateAreas>);
+
+impl Parse for TemplateAreasArc {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let parsed = TemplateAreas::parse(context, input)?;
+        Ok(TemplateAreasArc(Arc::new(parsed)))
+    }
+}
+
+/// A range of rows or columns. Using this instead of std::ops::Range for FFI
+/// purposes.
+#[repr(C)]
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub struct UnsignedRange {
+    /// The start of the range.
+    pub start: u32,
+    /// The end of the range.
+    pub end: u32,
+}
+
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// Not associated with any particular grid item, but can be referenced from the
+/// grid-placement properties.
+pub struct NamedArea {
+    /// Name of the `named area`
+    pub name: Atom,
+    /// Rows of the `named area`
+    pub rows: UnsignedRange,
+    /// Columns of the `named area`
+    pub columns: UnsignedRange,
+}
+
+/// Tokenize the string into a list of the tokens,
+/// using longest-match semantics
+struct TemplateAreasTokenizer<'a>(&'a str);
+
+impl<'a> Iterator for TemplateAreasTokenizer<'a> {
+    type Item = Result<Option<&'a str>, ()>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let rest = self.0.trim_start_matches(HTML_SPACE_CHARACTERS);
+        if rest.is_empty() {
+            return None;
+        }
+        if rest.starts_with('.') {
+            self.0 = &rest[rest.find(|c| c != '.').unwrap_or(rest.len())..];
+            return Some(Ok(None));
+        }
+        if !rest.starts_with(is_name_code_point) {
+            return Some(Err(()));
+        }
+        let token_len = rest.find(|c| !is_name_code_point(c)).unwrap_or(rest.len());
+        let token = &rest[..token_len];
+        self.0 = &rest[token_len..];
+        Some(Ok(Some(token)))
+    }
+}
+
+fn is_name_code_point(c: char) -> bool {
+    c >= 'A' && c <= 'Z' ||
+        c >= 'a' && c <= 'z' ||
+        c >= '\u{80}' ||
+        c == '_' ||
+        c >= '0' && c <= '9' ||
+        c == '-'
+}
+
+/// This property specifies named grid areas.
+///
+/// The syntax of this property also provides a visualization of the structure
+/// of the grid, making the overall layout of the grid container easier to
+/// understand.
+#[repr(C, u8)]
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+pub enum GridTemplateAreas {
+    /// The `none` value.
+    None,
+    /// The actual value.
+    Areas(TemplateAreasArc),
+}
+
+impl GridTemplateAreas {
+    #[inline]
+    /// Get default value as `none`
+    pub fn none() -> GridTemplateAreas {
+        GridTemplateAreas::None
+    }
+}
+
+/// A specified value for the `z-index` property.
+pub type ZIndex = GenericZIndex<Integer>;
+
+/// A specified value for the `aspect-ratio` property.
+pub type AspectRatio = GenericAspectRatio<NonNegativeNumber>;
+
+impl Parse for AspectRatio {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        use crate::values::generics::position::PreferredRatio;
+        use crate::values::specified::Ratio;
+
+        let location = input.current_source_location();
+        let mut auto = input.try_parse(|i| i.expect_ident_matching("auto"));
+        let ratio = input.try_parse(|i| Ratio::parse(context, i));
+        if auto.is_err() {
+            auto = input.try_parse(|i| i.expect_ident_matching("auto"));
+        }
+
+        if auto.is_err() && ratio.is_err() {
+            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(AspectRatio {
+            auto: auto.is_ok(),
+            ratio: match ratio {
+                Ok(ratio) => PreferredRatio::Ratio(ratio),
+                Err(..) => PreferredRatio::None,
+            },
+        })
+    }
+}
+
+impl AspectRatio {
+    /// Returns Self by a valid ratio.
+    pub fn from_mapped_ratio(w: f32, h: f32) -> Self {
+        use crate::values::generics::position::PreferredRatio;
+        use crate::values::generics::ratio::Ratio;
+        AspectRatio {
+            auto: true,
+            ratio: PreferredRatio::Ratio(Ratio(
+                NonNegativeNumber::new(w),
+                NonNegativeNumber::new(h),
+            )),
+        }
+    }
+}
diff --git a/servo/components/style/values/specified/ratio.rs b/servo/components/style/values/specified/ratio.rs
new file mode 100644
index 0000000000..4cdddd452e
--- /dev/null
+++ b/servo/components/style/values/specified/ratio.rs
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for <ratio>.
+//!
+//! [ratio]: https://drafts.csswg.org/css-values/#ratios
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::ratio::Ratio as GenericRatio;
+use crate::values::specified::NonNegativeNumber;
+use crate::One;
+use cssparser::Parser;
+use style_traits::ParseError;
+
+/// A specified <ratio> value.
+pub type Ratio = GenericRatio<NonNegativeNumber>;
+
+impl Parse for Ratio {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let a = NonNegativeNumber::parse(context, input)?;
+        let b = match input.try_parse(|input| input.expect_delim('/')) {
+            Ok(()) => NonNegativeNumber::parse(context, input)?,
+            _ => One::one(),
+        };
+
+        Ok(GenericRatio(a, b))
+    }
+}
diff --git a/servo/components/style/values/specified/rect.rs b/servo/components/style/values/specified/rect.rs
new file mode 100644
index 0000000000..7955ecaa48
--- /dev/null
+++ b/servo/components/style/values/specified/rect.rs
@@ -0,0 +1,11 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS borders.
+
+use crate::values::generics::rect::Rect;
+use crate::values::specified::length::NonNegativeLengthOrNumber;
+
+/// A specified rectangle made of four `<length-or-number>` values.
+pub type NonNegativeLengthOrNumberRect = Rect<NonNegativeLengthOrNumber>;
diff --git a/servo/components/style/values/specified/resolution.rs b/servo/components/style/values/specified/resolution.rs
new file mode 100644
index 0000000000..5ed642f981
--- /dev/null
+++ b/servo/components/style/values/specified/resolution.rs
@@ -0,0 +1,77 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Resolution values:
+//!
+//! https://drafts.csswg.org/css-values/#resolution
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::CSSFloat;
+use cssparser::{Parser, Token};
+use style_traits::{ParseError, StyleParseErrorKind};
+
+/// A specified resolution.
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum Resolution {
+    /// Dots per inch.
+    #[css(dimension)]
+    Dpi(CSSFloat),
+    /// An alias unit for dots per pixel.
+    #[css(dimension)]
+    X(CSSFloat),
+    /// Dots per pixel.
+    #[css(dimension)]
+    Dppx(CSSFloat),
+    /// Dots per centimeter.
+    #[css(dimension)]
+    Dpcm(CSSFloat),
+}
+
+impl Resolution {
+    /// Convert this resolution value to dppx units.
+    pub fn to_dppx(&self) -> CSSFloat {
+        match *self {
+            Resolution::X(f) | Resolution::Dppx(f) => f,
+            _ => self.to_dpi() / 96.0,
+        }
+    }
+
+    /// Convert this resolution value to dpi units.
+    pub fn to_dpi(&self) -> CSSFloat {
+        match *self {
+            Resolution::Dpi(f) => f,
+            Resolution::X(f) | Resolution::Dppx(f) => f * 96.0,
+            Resolution::Dpcm(f) => f * 2.54,
+        }
+    }
+}
+
+impl Parse for Resolution {
+    fn parse<'i, 't>(
+        _: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let (value, unit) = match *input.next()? {
+            Token::Dimension {
+                value, ref unit, ..
+            } => (value, unit),
+            ref t => return Err(location.new_unexpected_token_error(t.clone())),
+        };
+
+        if value <= 0. {
+            return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        match_ignore_ascii_case! { &unit,
+            "dpi" => Ok(Resolution::Dpi(value)),
+            "dppx" => Ok(Resolution::Dppx(value)),
+            "dpcm" => Ok(Resolution::Dpcm(value)),
+            "x" => Ok(Resolution::X(value)),
+            _ => Err(location.new_custom_error(
+                StyleParseErrorKind::UnexpectedDimension(unit.clone())
+            )),
+        }
+    }
+}
diff --git a/servo/components/style/values/specified/source_size_list.rs b/servo/components/style/values/specified/source_size_list.rs
new file mode 100644
index 0000000000..faafbb9016
--- /dev/null
+++ b/servo/components/style/values/specified/source_size_list.rs
@@ -0,0 +1,145 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! https://html.spec.whatwg.org/multipage/#source-size-list
+
+#[cfg(feature = "gecko")]
+use crate::gecko_bindings::sugar::ownership::{HasBoxFFI, HasFFI, HasSimpleFFI};
+use crate::media_queries::Device;
+use crate::parser::{Parse, ParserContext};
+use crate::queries::{FeatureType, QueryCondition};
+use crate::values::computed::{self, ToComputedValue};
+use crate::values::specified::{Length, NoCalcLength, ViewportPercentageLength};
+use app_units::Au;
+use cssparser::{Delimiter, Parser, Token};
+use selectors::context::QuirksMode;
+use style_traits::ParseError;
+
+/// A value for a `<source-size>`:
+///
+/// https://html.spec.whatwg.org/multipage/#source-size
+#[derive(Debug)]
+pub struct SourceSize {
+    condition: QueryCondition,
+    value: Length,
+}
+
+impl Parse for SourceSize {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let condition = QueryCondition::parse(context, input, FeatureType::Media)?;
+        let value = Length::parse_non_negative(context, input)?;
+        Ok(Self { condition, value })
+    }
+}
+
+/// A value for a `<source-size-list>`:
+///
+/// https://html.spec.whatwg.org/multipage/#source-size-list
+#[derive(Debug)]
+pub struct SourceSizeList {
+    source_sizes: Vec<SourceSize>,
+    value: Option<Length>,
+}
+
+impl SourceSizeList {
+    /// Create an empty `SourceSizeList`, which can be used as a fall-back.
+    pub fn empty() -> Self {
+        Self {
+            source_sizes: vec![],
+            value: None,
+        }
+    }
+
+    /// Evaluate this <source-size-list> to get the final viewport length.
+    pub fn evaluate(&self, device: &Device, quirks_mode: QuirksMode) -> Au {
+        computed::Context::for_media_query_evaluation(device, quirks_mode, |context| {
+            let matching_source_size = self
+                .source_sizes
+                .iter()
+                .find(|source_size| source_size.condition.matches(context).to_bool(/* unknown = */ false));
+
+            match matching_source_size {
+                Some(source_size) => source_size.value.to_computed_value(context),
+                None => match self.value {
+                    Some(ref v) => v.to_computed_value(context),
+                    None => Length::NoCalc(NoCalcLength::ViewportPercentage(
+                        ViewportPercentageLength::Vw(100.),
+                    ))
+                    .to_computed_value(context),
+                },
+            }
+        })
+        .into()
+    }
+}
+
+enum SourceSizeOrLength {
+    SourceSize(SourceSize),
+    Length(Length),
+}
+
+impl Parse for SourceSizeOrLength {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(size) = input.try_parse(|input| SourceSize::parse(context, input)) {
+            return Ok(SourceSizeOrLength::SourceSize(size));
+        }
+
+        let length = Length::parse_non_negative(context, input)?;
+        Ok(SourceSizeOrLength::Length(length))
+    }
+}
+
+impl SourceSizeList {
+    /// NOTE(emilio): This doesn't match the grammar in the spec, see:
+    ///
+    /// https://html.spec.whatwg.org/multipage/#parsing-a-sizes-attribute
+    pub fn parse<'i, 't>(context: &ParserContext, input: &mut Parser<'i, 't>) -> Self {
+        let mut source_sizes = vec![];
+
+        loop {
+            let result = input.parse_until_before(Delimiter::Comma, |input| {
+                SourceSizeOrLength::parse(context, input)
+            });
+
+            match result {
+                Ok(SourceSizeOrLength::Length(value)) => {
+                    return Self {
+                        source_sizes,
+                        value: Some(value),
+                    };
+                },
+                Ok(SourceSizeOrLength::SourceSize(source_size)) => {
+                    source_sizes.push(source_size);
+                },
+                Err(..) => {},
+            }
+
+            match input.next() {
+                Ok(&Token::Comma) => {},
+                Err(..) => break,
+                _ => unreachable!(),
+            }
+        }
+
+        SourceSizeList {
+            source_sizes,
+            value: None,
+        }
+    }
+}
+
+#[cfg(feature = "gecko")]
+unsafe impl HasFFI for SourceSizeList {
+    type FFIType = crate::gecko_bindings::structs::RawServoSourceSizeList;
+}
+#[cfg(feature = "gecko")]
+unsafe impl HasSimpleFFI for SourceSizeList {}
+#[cfg(feature = "gecko")]
+unsafe impl HasBoxFFI for SourceSizeList {}
diff --git a/servo/components/style/values/specified/svg.rs b/servo/components/style/values/specified/svg.rs
new file mode 100644
index 0000000000..f06fc43c46
--- /dev/null
+++ b/servo/components/style/values/specified/svg.rs
@@ -0,0 +1,391 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for SVG properties.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::svg as generic;
+use crate::values::specified::color::Color;
+use crate::values::specified::url::SpecifiedUrl;
+use crate::values::specified::AllowQuirks;
+use crate::values::specified::LengthPercentage;
+use crate::values::specified::SVGPathData;
+use crate::values::specified::{NonNegativeLengthPercentage, Opacity};
+use crate::values::CustomIdent;
+use cssparser::{Parser, Token};
+use std::fmt::{self, Write};
+use style_traits::{CommaWithSpace, CssWriter, ParseError, Separator};
+use style_traits::{StyleParseErrorKind, ToCss};
+
+/// Specified SVG Paint value
+pub type SVGPaint = generic::GenericSVGPaint<Color, SpecifiedUrl>;
+
+/// <length> | <percentage> | <number> | context-value
+pub type SVGLength = generic::GenericSVGLength<LengthPercentage>;
+
+/// A non-negative version of SVGLength.
+pub type SVGWidth = generic::GenericSVGLength<NonNegativeLengthPercentage>;
+
+/// [ <length> | <percentage> | <number> ]# | context-value
+pub type SVGStrokeDashArray = generic::GenericSVGStrokeDashArray<NonNegativeLengthPercentage>;
+
+/// Whether the `context-value` value is enabled.
+#[cfg(feature = "gecko")]
+pub fn is_context_value_enabled() -> bool {
+    static_prefs::pref!("gfx.font_rendering.opentype_svg.enabled")
+}
+
+/// Whether the `context-value` value is enabled.
+#[cfg(not(feature = "gecko"))]
+pub fn is_context_value_enabled() -> bool {
+    false
+}
+
+macro_rules! parse_svg_length {
+    ($ty:ty, $lp:ty) => {
+        impl Parse for $ty {
+            fn parse<'i, 't>(
+                context: &ParserContext,
+                input: &mut Parser<'i, 't>,
+            ) -> Result<Self, ParseError<'i>> {
+                if let Ok(lp) =
+                    input.try_parse(|i| <$lp>::parse_quirky(context, i, AllowQuirks::Always))
+                {
+                    return Ok(generic::SVGLength::LengthPercentage(lp));
+                }
+
+                try_match_ident_ignore_ascii_case! { input,
+                    "context-value" if is_context_value_enabled() => {
+                        Ok(generic::SVGLength::ContextValue)
+                    },
+                }
+            }
+        }
+    };
+}
+
+parse_svg_length!(SVGLength, LengthPercentage);
+parse_svg_length!(SVGWidth, NonNegativeLengthPercentage);
+
+impl Parse for SVGStrokeDashArray {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if let Ok(values) = input.try_parse(|i| {
+            CommaWithSpace::parse(i, |i| {
+                NonNegativeLengthPercentage::parse_quirky(context, i, AllowQuirks::Always)
+            })
+        }) {
+            return Ok(generic::SVGStrokeDashArray::Values(values.into()));
+        }
+
+        try_match_ident_ignore_ascii_case! { input,
+            "context-value" if is_context_value_enabled() => {
+                Ok(generic::SVGStrokeDashArray::ContextValue)
+            },
+            "none" => Ok(generic::SVGStrokeDashArray::Values(Default::default())),
+        }
+    }
+}
+
+/// <opacity-value> | context-fill-opacity | context-stroke-opacity
+pub type SVGOpacity = generic::SVGOpacity<Opacity>;
+
+/// The specified value for a single CSS paint-order property.
+#[repr(u8)]
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd, ToCss)]
+pub enum PaintOrder {
+    /// `normal` variant
+    Normal = 0,
+    /// `fill` variant
+    Fill = 1,
+    /// `stroke` variant
+    Stroke = 2,
+    /// `markers` variant
+    Markers = 3,
+}
+
+/// Number of non-normal components
+pub const PAINT_ORDER_COUNT: u8 = 3;
+
+/// Number of bits for each component
+pub const PAINT_ORDER_SHIFT: u8 = 2;
+
+/// Mask with above bits set
+pub const PAINT_ORDER_MASK: u8 = 0b11;
+
+/// The specified value is tree `PaintOrder` values packed into the
+/// bitfields below, as a six-bit field, of 3 two-bit pairs
+///
+/// Each pair can be set to FILL, STROKE, or MARKERS
+/// Lowest significant bit pairs are highest priority.
+///  `normal` is the empty bitfield. The three pairs are
+/// never zero in any case other than `normal`.
+///
+/// Higher priority values, i.e. the values specified first,
+/// will be painted first (and may be covered by paintings of lower priority)
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct SVGPaintOrder(pub u8);
+
+impl SVGPaintOrder {
+    /// Get default `paint-order` with `0`
+    pub fn normal() -> Self {
+        SVGPaintOrder(0)
+    }
+
+    /// Get variant of `paint-order`
+    pub fn order_at(&self, pos: u8) -> PaintOrder {
+        match (self.0 >> pos * PAINT_ORDER_SHIFT) & PAINT_ORDER_MASK {
+            0 => PaintOrder::Normal,
+            1 => PaintOrder::Fill,
+            2 => PaintOrder::Stroke,
+            3 => PaintOrder::Markers,
+            _ => unreachable!("this cannot happen"),
+        }
+    }
+}
+
+impl Parse for SVGPaintOrder {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<SVGPaintOrder, ParseError<'i>> {
+        if let Ok(()) = input.try_parse(|i| i.expect_ident_matching("normal")) {
+            return Ok(SVGPaintOrder::normal());
+        }
+
+        let mut value = 0;
+        // bitfield representing what we've seen so far
+        // bit 1 is fill, bit 2 is stroke, bit 3 is markers
+        let mut seen = 0;
+        let mut pos = 0;
+
+        loop {
+            let result: Result<_, ParseError> = input.try_parse(|input| {
+                try_match_ident_ignore_ascii_case! { input,
+                    "fill" => Ok(PaintOrder::Fill),
+                    "stroke" => Ok(PaintOrder::Stroke),
+                    "markers" => Ok(PaintOrder::Markers),
+                }
+            });
+
+            match result {
+                Ok(val) => {
+                    if (seen & (1 << val as u8)) != 0 {
+                        // don't parse the same ident twice
+                        return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                    }
+
+                    value |= (val as u8) << (pos * PAINT_ORDER_SHIFT);
+                    seen |= 1 << (val as u8);
+                    pos += 1;
+                },
+                Err(_) => break,
+            }
+        }
+
+        if value == 0 {
+            // Couldn't find any keyword
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        // fill in rest
+        for i in pos..PAINT_ORDER_COUNT {
+            for paint in 1..(PAINT_ORDER_COUNT + 1) {
+                // if not seen, set bit at position, mark as seen
+                if (seen & (1 << paint)) == 0 {
+                    seen |= 1 << paint;
+                    value |= paint << (i * PAINT_ORDER_SHIFT);
+                    break;
+                }
+            }
+        }
+
+        Ok(SVGPaintOrder(value))
+    }
+}
+
+impl ToCss for SVGPaintOrder {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.0 == 0 {
+            return dest.write_str("normal");
+        }
+
+        let mut last_pos_to_serialize = 0;
+        for i in (1..PAINT_ORDER_COUNT).rev() {
+            let component = self.order_at(i);
+            let earlier_component = self.order_at(i - 1);
+            if component < earlier_component {
+                last_pos_to_serialize = i - 1;
+                break;
+            }
+        }
+
+        for pos in 0..last_pos_to_serialize + 1 {
+            if pos != 0 {
+                dest.write_str(" ")?
+            }
+            self.order_at(pos).to_css(dest)?;
+        }
+        Ok(())
+    }
+}
+
+bitflags! {
+    /// The context properties we understand.
+    #[derive(Default, MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[repr(C)]
+    pub struct ContextPropertyBits: u8 {
+        /// `fill`
+        const FILL = 1 << 0;
+        /// `stroke`
+        const STROKE = 1 << 1;
+        /// `fill-opacity`
+        const FILL_OPACITY = 1 << 2;
+        /// `stroke-opacity`
+        const STROKE_OPACITY = 1 << 3;
+    }
+}
+
+/// Specified MozContextProperties value.
+/// Nonstandard (https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-context-properties)
+#[derive(
+    Clone,
+    Debug,
+    Default,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct MozContextProperties {
+    #[css(iterable, if_empty = "none")]
+    #[ignore_malloc_size_of = "Arc"]
+    idents: crate::ArcSlice<CustomIdent>,
+    #[css(skip)]
+    bits: ContextPropertyBits,
+}
+
+impl Parse for MozContextProperties {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<MozContextProperties, ParseError<'i>> {
+        let mut values = vec![];
+        let mut bits = ContextPropertyBits::empty();
+        loop {
+            {
+                let location = input.current_source_location();
+                let ident = input.expect_ident()?;
+
+                if ident.eq_ignore_ascii_case("none") && values.is_empty() {
+                    return Ok(Self::default());
+                }
+
+                let ident = CustomIdent::from_ident(location, ident, &["all", "none", "auto"])?;
+
+                if ident.0 == atom!("fill") {
+                    bits.insert(ContextPropertyBits::FILL);
+                } else if ident.0 == atom!("stroke") {
+                    bits.insert(ContextPropertyBits::STROKE);
+                } else if ident.0 == atom!("fill-opacity") {
+                    bits.insert(ContextPropertyBits::FILL_OPACITY);
+                } else if ident.0 == atom!("stroke-opacity") {
+                    bits.insert(ContextPropertyBits::STROKE_OPACITY);
+                }
+
+                values.push(ident);
+            }
+
+            let location = input.current_source_location();
+            match input.next() {
+                Ok(&Token::Comma) => continue,
+                Err(..) => break,
+                Ok(other) => return Err(location.new_unexpected_token_error(other.clone())),
+            }
+        }
+
+        if values.is_empty() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        Ok(MozContextProperties {
+            idents: crate::ArcSlice::from_iter(values.into_iter()),
+            bits,
+        })
+    }
+}
+
+/// The svg d property type.
+///
+/// https://svgwg.org/svg2-draft/paths.html#TheDProperty
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum DProperty {
+    /// Path value for path(<string>) or just a <string>.
+    #[css(function)]
+    Path(SVGPathData),
+    /// None value.
+    #[animation(error)]
+    None,
+}
+
+impl DProperty {
+    /// return none.
+    #[inline]
+    pub fn none() -> Self {
+        DProperty::None
+    }
+}
+
+impl Parse for DProperty {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // Parse none.
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(DProperty::none());
+        }
+
+        // Parse possible functions.
+        input.expect_function_matching("path")?;
+        let path_data = input.parse_nested_block(|i| SVGPathData::parse(context, i))?;
+        Ok(DProperty::Path(path_data))
+    }
+}
diff --git a/servo/components/style/values/specified/svg_path.rs b/servo/components/style/values/specified/svg_path.rs
new file mode 100644
index 0000000000..7dda8a9e73
--- /dev/null
+++ b/servo/components/style/values/specified/svg_path.rs
@@ -0,0 +1,1011 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for SVG Path.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::animated::{Animate, Procedure, ToAnimatedZero};
+use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
+use crate::values::CSSFloat;
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use std::iter::{Cloned, Peekable};
+use std::slice;
+use style_traits::values::SequenceWriter;
+use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+
+/// The SVG path data.
+///
+/// https://www.w3.org/TR/SVG11/paths.html#PathData
+#[derive(
+    Clone,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct SVGPathData(
+    // TODO(emilio): Should probably measure this somehow only from the
+    // specified values.
+    #[ignore_malloc_size_of = "Arc"] pub crate::ArcSlice<PathCommand>,
+);
+
+impl SVGPathData {
+    /// Get the array of PathCommand.
+    #[inline]
+    pub fn commands(&self) -> &[PathCommand] {
+        &self.0
+    }
+
+    /// Create a normalized copy of this path by converting each relative
+    /// command to an absolute command.
+    pub fn normalize(&self) -> Self {
+        let mut state = PathTraversalState {
+            subpath_start: CoordPair::new(0.0, 0.0),
+            pos: CoordPair::new(0.0, 0.0),
+        };
+        let result = self
+            .0
+            .iter()
+            .map(|seg| seg.normalize(&mut state))
+            .collect::<Vec<_>>();
+
+        SVGPathData(crate::ArcSlice::from_iter(result.into_iter()))
+    }
+
+    // FIXME: Bug 1714238, we may drop this once we use the same data structure for both SVG and
+    // CSS.
+    /// Decode the svg path raw data from Gecko.
+    #[cfg(feature = "gecko")]
+    pub fn decode_from_f32_array(path: &[f32]) -> Result<Self, ()> {
+        use crate::gecko_bindings::structs::dom::SVGPathSeg_Binding::*;
+
+        let mut result: Vec<PathCommand> = Vec::new();
+        let mut i: usize = 0;
+        while i < path.len() {
+            // See EncodeType() and DecodeType() in SVGPathSegUtils.h.
+            // We are using reinterpret_cast<> to encode and decode between u32 and f32, so here we
+            // use to_bits() to decode the type.
+            let seg_type = path[i].to_bits() as u16;
+            i = i + 1;
+            match seg_type {
+                PATHSEG_CLOSEPATH => result.push(PathCommand::ClosePath),
+                PATHSEG_MOVETO_ABS | PATHSEG_MOVETO_REL => {
+                    debug_assert!(i + 1 < path.len());
+                    result.push(PathCommand::MoveTo {
+                        point: CoordPair::new(path[i], path[i + 1]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_MOVETO_ABS),
+                    });
+                    i = i + 2;
+                },
+                PATHSEG_LINETO_ABS | PATHSEG_LINETO_REL => {
+                    debug_assert!(i + 1 < path.len());
+                    result.push(PathCommand::LineTo {
+                        point: CoordPair::new(path[i], path[i + 1]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_LINETO_ABS),
+                    });
+                    i = i + 2;
+                },
+                PATHSEG_CURVETO_CUBIC_ABS | PATHSEG_CURVETO_CUBIC_REL => {
+                    debug_assert!(i + 5 < path.len());
+                    result.push(PathCommand::CurveTo {
+                        control1: CoordPair::new(path[i], path[i + 1]),
+                        control2: CoordPair::new(path[i + 2], path[i + 3]),
+                        point: CoordPair::new(path[i + 4], path[i + 5]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_CUBIC_ABS),
+                    });
+                    i = i + 6;
+                },
+                PATHSEG_CURVETO_QUADRATIC_ABS | PATHSEG_CURVETO_QUADRATIC_REL => {
+                    debug_assert!(i + 3 < path.len());
+                    result.push(PathCommand::QuadBezierCurveTo {
+                        control1: CoordPair::new(path[i], path[i + 1]),
+                        point: CoordPair::new(path[i + 2], path[i + 3]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_QUADRATIC_ABS),
+                    });
+                    i = i + 4;
+                },
+                PATHSEG_ARC_ABS | PATHSEG_ARC_REL => {
+                    debug_assert!(i + 6 < path.len());
+                    result.push(PathCommand::EllipticalArc {
+                        rx: path[i],
+                        ry: path[i + 1],
+                        angle: path[i + 2],
+                        large_arc_flag: ArcFlag(path[i + 3] != 0.0f32),
+                        sweep_flag: ArcFlag(path[i + 4] != 0.0f32),
+                        point: CoordPair::new(path[i + 5], path[i + 6]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_ARC_ABS),
+                    });
+                    i = i + 7;
+                },
+                PATHSEG_LINETO_HORIZONTAL_ABS | PATHSEG_LINETO_HORIZONTAL_REL => {
+                    debug_assert!(i < path.len());
+                    result.push(PathCommand::HorizontalLineTo {
+                        x: path[i],
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_LINETO_HORIZONTAL_ABS),
+                    });
+                    i = i + 1;
+                },
+                PATHSEG_LINETO_VERTICAL_ABS | PATHSEG_LINETO_VERTICAL_REL => {
+                    debug_assert!(i < path.len());
+                    result.push(PathCommand::VerticalLineTo {
+                        y: path[i],
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_LINETO_VERTICAL_ABS),
+                    });
+                    i = i + 1;
+                },
+                PATHSEG_CURVETO_CUBIC_SMOOTH_ABS | PATHSEG_CURVETO_CUBIC_SMOOTH_REL => {
+                    debug_assert!(i + 3 < path.len());
+                    result.push(PathCommand::SmoothCurveTo {
+                        control2: CoordPair::new(path[i], path[i + 1]),
+                        point: CoordPair::new(path[i + 2], path[i + 3]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_CUBIC_SMOOTH_ABS),
+                    });
+                    i = i + 4;
+                },
+                PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS | PATHSEG_CURVETO_QUADRATIC_SMOOTH_REL => {
+                    debug_assert!(i + 1 < path.len());
+                    result.push(PathCommand::SmoothQuadBezierCurveTo {
+                        point: CoordPair::new(path[i], path[i + 1]),
+                        absolute: IsAbsolute::new(seg_type == PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS),
+                    });
+                    i = i + 2;
+                },
+                PATHSEG_UNKNOWN | _ => return Err(()),
+            }
+        }
+
+        Ok(SVGPathData(crate::ArcSlice::from_iter(result.into_iter())))
+    }
+}
+
+impl ToCss for SVGPathData {
+    #[inline]
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        dest.write_char('"')?;
+        {
+            let mut writer = SequenceWriter::new(dest, " ");
+            for command in self.commands() {
+                writer.item(command)?;
+            }
+        }
+        dest.write_char('"')
+    }
+}
+
+impl Parse for SVGPathData {
+    // We cannot use cssparser::Parser to parse a SVG path string because the spec wants to make
+    // the SVG path string as compact as possible. (i.e. The whitespaces may be dropped.)
+    // e.g. "M100 200L100 200" is a valid SVG path string. If we use tokenizer, the first ident
+    // is "M100", instead of "M", and this is not correct. Therefore, we use a Peekable
+    // str::Char iterator to check each character.
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let location = input.current_source_location();
+        let path_string = input.expect_string()?.as_ref();
+
+        // Parse the svg path string as multiple sub-paths.
+        let mut path_parser = PathParser::new(path_string);
+        while skip_wsp(&mut path_parser.chars) {
+            if path_parser.parse_subpath().is_err() {
+                return Err(location.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+            }
+        }
+
+        Ok(SVGPathData(crate::ArcSlice::from_iter(
+            path_parser.path.into_iter(),
+        )))
+    }
+}
+
+impl Animate for SVGPathData {
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        if self.0.len() != other.0.len() {
+            return Err(());
+        }
+
+        // FIXME(emilio): This allocates three copies of the path, that's not
+        // great! Specially, once we're normalized once, we don't need to
+        // re-normalize again.
+        let result = self
+            .normalize()
+            .0
+            .iter()
+            .zip(other.normalize().0.iter())
+            .map(|(a, b)| a.animate(&b, procedure))
+            .collect::<Result<Vec<_>, _>>()?;
+
+        Ok(SVGPathData(crate::ArcSlice::from_iter(result.into_iter())))
+    }
+}
+
+impl ComputeSquaredDistance for SVGPathData {
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        if self.0.len() != other.0.len() {
+            return Err(());
+        }
+        self.normalize()
+            .0
+            .iter()
+            .zip(other.normalize().0.iter())
+            .map(|(this, other)| this.compute_squared_distance(&other))
+            .sum()
+    }
+}
+
+/// The SVG path command.
+/// The fields of these commands are self-explanatory, so we skip the documents.
+/// Note: the index of the control points, e.g. control1, control2, are mapping to the control
+/// points of the Bézier curve in the spec.
+///
+/// https://www.w3.org/TR/SVG11/paths.html#PathData
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[repr(C, u8)]
+pub enum PathCommand {
+    /// The unknown type.
+    /// https://www.w3.org/TR/SVG/paths.html#__svg__SVGPathSeg__PATHSEG_UNKNOWN
+    Unknown,
+    /// The "moveto" command.
+    MoveTo {
+        point: CoordPair,
+        absolute: IsAbsolute,
+    },
+    /// The "lineto" command.
+    LineTo {
+        point: CoordPair,
+        absolute: IsAbsolute,
+    },
+    /// The horizontal "lineto" command.
+    HorizontalLineTo { x: CSSFloat, absolute: IsAbsolute },
+    /// The vertical "lineto" command.
+    VerticalLineTo { y: CSSFloat, absolute: IsAbsolute },
+    /// The cubic Bézier curve command.
+    CurveTo {
+        control1: CoordPair,
+        control2: CoordPair,
+        point: CoordPair,
+        absolute: IsAbsolute,
+    },
+    /// The smooth curve command.
+    SmoothCurveTo {
+        control2: CoordPair,
+        point: CoordPair,
+        absolute: IsAbsolute,
+    },
+    /// The quadratic Bézier curve command.
+    QuadBezierCurveTo {
+        control1: CoordPair,
+        point: CoordPair,
+        absolute: IsAbsolute,
+    },
+    /// The smooth quadratic Bézier curve command.
+    SmoothQuadBezierCurveTo {
+        point: CoordPair,
+        absolute: IsAbsolute,
+    },
+    /// The elliptical arc curve command.
+    EllipticalArc {
+        rx: CSSFloat,
+        ry: CSSFloat,
+        angle: CSSFloat,
+        large_arc_flag: ArcFlag,
+        sweep_flag: ArcFlag,
+        point: CoordPair,
+        absolute: IsAbsolute,
+    },
+    /// The "closepath" command.
+    ClosePath,
+}
+
+/// For internal SVGPath normalization.
+#[allow(missing_docs)]
+struct PathTraversalState {
+    subpath_start: CoordPair,
+    pos: CoordPair,
+}
+
+impl PathCommand {
+    /// Create a normalized copy of this PathCommand. Absolute commands will be copied as-is while
+    /// for relative commands an equivalent absolute command will be returned.
+    ///
+    /// See discussion: https://github.com/w3c/svgwg/issues/321
+    fn normalize(&self, state: &mut PathTraversalState) -> Self {
+        use self::PathCommand::*;
+        match *self {
+            Unknown => Unknown,
+            ClosePath => {
+                state.pos = state.subpath_start;
+                ClosePath
+            },
+            MoveTo {
+                mut point,
+                absolute,
+            } => {
+                if !absolute.is_yes() {
+                    point += state.pos;
+                }
+                state.pos = point;
+                state.subpath_start = point;
+                MoveTo {
+                    point,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            LineTo {
+                mut point,
+                absolute,
+            } => {
+                if !absolute.is_yes() {
+                    point += state.pos;
+                }
+                state.pos = point;
+                LineTo {
+                    point,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            HorizontalLineTo { mut x, absolute } => {
+                if !absolute.is_yes() {
+                    x += state.pos.0;
+                }
+                state.pos.0 = x;
+                HorizontalLineTo {
+                    x,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            VerticalLineTo { mut y, absolute } => {
+                if !absolute.is_yes() {
+                    y += state.pos.1;
+                }
+                state.pos.1 = y;
+                VerticalLineTo {
+                    y,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            CurveTo {
+                mut control1,
+                mut control2,
+                mut point,
+                absolute,
+            } => {
+                if !absolute.is_yes() {
+                    control1 += state.pos;
+                    control2 += state.pos;
+                    point += state.pos;
+                }
+                state.pos = point;
+                CurveTo {
+                    control1,
+                    control2,
+                    point,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            SmoothCurveTo {
+                mut control2,
+                mut point,
+                absolute,
+            } => {
+                if !absolute.is_yes() {
+                    control2 += state.pos;
+                    point += state.pos;
+                }
+                state.pos = point;
+                SmoothCurveTo {
+                    control2,
+                    point,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            QuadBezierCurveTo {
+                mut control1,
+                mut point,
+                absolute,
+            } => {
+                if !absolute.is_yes() {
+                    control1 += state.pos;
+                    point += state.pos;
+                }
+                state.pos = point;
+                QuadBezierCurveTo {
+                    control1,
+                    point,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            SmoothQuadBezierCurveTo {
+                mut point,
+                absolute,
+            } => {
+                if !absolute.is_yes() {
+                    point += state.pos;
+                }
+                state.pos = point;
+                SmoothQuadBezierCurveTo {
+                    point,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+            EllipticalArc {
+                rx,
+                ry,
+                angle,
+                large_arc_flag,
+                sweep_flag,
+                mut point,
+                absolute,
+            } => {
+                if !absolute.is_yes() {
+                    point += state.pos;
+                }
+                state.pos = point;
+                EllipticalArc {
+                    rx,
+                    ry,
+                    angle,
+                    large_arc_flag,
+                    sweep_flag,
+                    point,
+                    absolute: IsAbsolute::Yes,
+                }
+            },
+        }
+    }
+}
+
+impl ToCss for PathCommand {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        use self::PathCommand::*;
+        match *self {
+            Unknown => dest.write_char('X'),
+            ClosePath => dest.write_char('Z'),
+            MoveTo { point, absolute } => {
+                dest.write_char(if absolute.is_yes() { 'M' } else { 'm' })?;
+                dest.write_char(' ')?;
+                point.to_css(dest)
+            },
+            LineTo { point, absolute } => {
+                dest.write_char(if absolute.is_yes() { 'L' } else { 'l' })?;
+                dest.write_char(' ')?;
+                point.to_css(dest)
+            },
+            CurveTo {
+                control1,
+                control2,
+                point,
+                absolute,
+            } => {
+                dest.write_char(if absolute.is_yes() { 'C' } else { 'c' })?;
+                dest.write_char(' ')?;
+                control1.to_css(dest)?;
+                dest.write_char(' ')?;
+                control2.to_css(dest)?;
+                dest.write_char(' ')?;
+                point.to_css(dest)
+            },
+            QuadBezierCurveTo {
+                control1,
+                point,
+                absolute,
+            } => {
+                dest.write_char(if absolute.is_yes() { 'Q' } else { 'q' })?;
+                dest.write_char(' ')?;
+                control1.to_css(dest)?;
+                dest.write_char(' ')?;
+                point.to_css(dest)
+            },
+            EllipticalArc {
+                rx,
+                ry,
+                angle,
+                large_arc_flag,
+                sweep_flag,
+                point,
+                absolute,
+            } => {
+                dest.write_char(if absolute.is_yes() { 'A' } else { 'a' })?;
+                dest.write_char(' ')?;
+                rx.to_css(dest)?;
+                dest.write_char(' ')?;
+                ry.to_css(dest)?;
+                dest.write_char(' ')?;
+                angle.to_css(dest)?;
+                dest.write_char(' ')?;
+                large_arc_flag.to_css(dest)?;
+                dest.write_char(' ')?;
+                sweep_flag.to_css(dest)?;
+                dest.write_char(' ')?;
+                point.to_css(dest)
+            },
+            HorizontalLineTo { x, absolute } => {
+                dest.write_char(if absolute.is_yes() { 'H' } else { 'h' })?;
+                dest.write_char(' ')?;
+                x.to_css(dest)
+            },
+            VerticalLineTo { y, absolute } => {
+                dest.write_char(if absolute.is_yes() { 'V' } else { 'v' })?;
+                dest.write_char(' ')?;
+                y.to_css(dest)
+            },
+            SmoothCurveTo {
+                control2,
+                point,
+                absolute,
+            } => {
+                dest.write_char(if absolute.is_yes() { 'S' } else { 's' })?;
+                dest.write_char(' ')?;
+                control2.to_css(dest)?;
+                dest.write_char(' ')?;
+                point.to_css(dest)
+            },
+            SmoothQuadBezierCurveTo { point, absolute } => {
+                dest.write_char(if absolute.is_yes() { 'T' } else { 't' })?;
+                dest.write_char(' ')?;
+                point.to_css(dest)
+            },
+        }
+    }
+}
+
+/// The path command absolute type.
+#[allow(missing_docs)]
+#[derive(
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum IsAbsolute {
+    Yes,
+    No,
+}
+
+impl IsAbsolute {
+    /// Return true if this is IsAbsolute::Yes.
+    #[inline]
+    pub fn is_yes(&self) -> bool {
+        *self == IsAbsolute::Yes
+    }
+
+    /// Return Yes if value is true. Otherwise, return No.
+    #[inline]
+    fn new(value: bool) -> Self {
+        if value {
+            IsAbsolute::Yes
+        } else {
+            IsAbsolute::No
+        }
+    }
+}
+
+/// The path coord type.
+#[derive(
+    AddAssign,
+    Animate,
+    Clone,
+    ComputeSquaredDistance,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToAnimatedZero,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct CoordPair(CSSFloat, CSSFloat);
+
+impl CoordPair {
+    /// Create a CoordPair.
+    #[inline]
+    pub fn new(x: CSSFloat, y: CSSFloat) -> Self {
+        CoordPair(x, y)
+    }
+}
+
+/// The EllipticalArc flag type.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Deserialize,
+    MallocSizeOf,
+    PartialEq,
+    Serialize,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+pub struct ArcFlag(bool);
+
+impl ToCss for ArcFlag {
+    #[inline]
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: fmt::Write,
+    {
+        (self.0 as i32).to_css(dest)
+    }
+}
+
+impl Animate for ArcFlag {
+    #[inline]
+    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
+        (self.0 as i32)
+            .animate(&(other.0 as i32), procedure)
+            .map(|v| ArcFlag(v > 0))
+    }
+}
+
+impl ComputeSquaredDistance for ArcFlag {
+    #[inline]
+    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
+        (self.0 as i32).compute_squared_distance(&(other.0 as i32))
+    }
+}
+
+impl ToAnimatedZero for ArcFlag {
+    #[inline]
+    fn to_animated_zero(&self) -> Result<Self, ()> {
+        // The 2 ArcFlags in EllipticalArc determine which one of the 4 different arcs will be
+        // used. (i.e. From 4 combinations). In other words, if we change the flag, we get a
+        // different arc. Therefore, we return *self.
+        // https://svgwg.org/svg2-draft/paths.html#PathDataEllipticalArcCommands
+        Ok(*self)
+    }
+}
+
+/// SVG Path parser.
+struct PathParser<'a> {
+    chars: Peekable<Cloned<slice::Iter<'a, u8>>>,
+    path: Vec<PathCommand>,
+}
+
+macro_rules! parse_arguments {
+    (
+        $parser:ident,
+        $abs:ident,
+        $enum:ident,
+        [ $para:ident => $func:ident $(, $other_para:ident => $other_func:ident)* ]
+    ) => {
+        {
+            loop {
+                let $para = $func(&mut $parser.chars)?;
+                $(
+                    skip_comma_wsp(&mut $parser.chars);
+                    let $other_para = $other_func(&mut $parser.chars)?;
+                )*
+                $parser.path.push(PathCommand::$enum { $para $(, $other_para)*, $abs });
+
+                // End of string or the next character is a possible new command.
+                if !skip_wsp(&mut $parser.chars) ||
+                   $parser.chars.peek().map_or(true, |c| c.is_ascii_alphabetic()) {
+                    break;
+                }
+                skip_comma_wsp(&mut $parser.chars);
+            }
+            Ok(())
+        }
+    }
+}
+
+impl<'a> PathParser<'a> {
+    /// Return a PathParser.
+    #[inline]
+    fn new(string: &'a str) -> Self {
+        PathParser {
+            chars: string.as_bytes().iter().cloned().peekable(),
+            path: Vec::new(),
+        }
+    }
+
+    /// Parse a sub-path.
+    fn parse_subpath(&mut self) -> Result<(), ()> {
+        // Handle "moveto" Command first. If there is no "moveto", this is not a valid sub-path
+        // (i.e. not a valid moveto-drawto-command-group).
+        self.parse_moveto()?;
+
+        // Handle other commands.
+        loop {
+            skip_wsp(&mut self.chars);
+            if self.chars.peek().map_or(true, |&m| m == b'M' || m == b'm') {
+                break;
+            }
+
+            let command = self.chars.next().unwrap();
+            let abs = if command.is_ascii_uppercase() {
+                IsAbsolute::Yes
+            } else {
+                IsAbsolute::No
+            };
+
+            skip_wsp(&mut self.chars);
+            match command {
+                b'Z' | b'z' => self.parse_closepath(),
+                b'L' | b'l' => self.parse_lineto(abs),
+                b'H' | b'h' => self.parse_h_lineto(abs),
+                b'V' | b'v' => self.parse_v_lineto(abs),
+                b'C' | b'c' => self.parse_curveto(abs),
+                b'S' | b's' => self.parse_smooth_curveto(abs),
+                b'Q' | b'q' => self.parse_quadratic_bezier_curveto(abs),
+                b'T' | b't' => self.parse_smooth_quadratic_bezier_curveto(abs),
+                b'A' | b'a' => self.parse_elliptical_arc(abs),
+                _ => return Err(()),
+            }?;
+        }
+        Ok(())
+    }
+
+    /// Parse "moveto" command.
+    fn parse_moveto(&mut self) -> Result<(), ()> {
+        let command = match self.chars.next() {
+            Some(c) if c == b'M' || c == b'm' => c,
+            _ => return Err(()),
+        };
+
+        skip_wsp(&mut self.chars);
+        let point = parse_coord(&mut self.chars)?;
+        let absolute = if command == b'M' {
+            IsAbsolute::Yes
+        } else {
+            IsAbsolute::No
+        };
+        self.path.push(PathCommand::MoveTo { point, absolute });
+
+        // End of string or the next character is a possible new command.
+        if !skip_wsp(&mut self.chars) || self.chars.peek().map_or(true, |c| c.is_ascii_alphabetic())
+        {
+            return Ok(());
+        }
+        skip_comma_wsp(&mut self.chars);
+
+        // If a moveto is followed by multiple pairs of coordinates, the subsequent
+        // pairs are treated as implicit lineto commands.
+        self.parse_lineto(absolute)
+    }
+
+    /// Parse "closepath" command.
+    fn parse_closepath(&mut self) -> Result<(), ()> {
+        self.path.push(PathCommand::ClosePath);
+        Ok(())
+    }
+
+    /// Parse "lineto" command.
+    fn parse_lineto(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        parse_arguments!(self, absolute, LineTo, [ point => parse_coord ])
+    }
+
+    /// Parse horizontal "lineto" command.
+    fn parse_h_lineto(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        parse_arguments!(self, absolute, HorizontalLineTo, [ x => parse_number ])
+    }
+
+    /// Parse vertical "lineto" command.
+    fn parse_v_lineto(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        parse_arguments!(self, absolute, VerticalLineTo, [ y => parse_number ])
+    }
+
+    /// Parse cubic Bézier curve command.
+    fn parse_curveto(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        parse_arguments!(self, absolute, CurveTo, [
+            control1 => parse_coord, control2 => parse_coord, point => parse_coord
+        ])
+    }
+
+    /// Parse smooth "curveto" command.
+    fn parse_smooth_curveto(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        parse_arguments!(self, absolute, SmoothCurveTo, [
+            control2 => parse_coord, point => parse_coord
+        ])
+    }
+
+    /// Parse quadratic Bézier curve command.
+    fn parse_quadratic_bezier_curveto(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        parse_arguments!(self, absolute, QuadBezierCurveTo, [
+            control1 => parse_coord, point => parse_coord
+        ])
+    }
+
+    /// Parse smooth quadratic Bézier curveto command.
+    fn parse_smooth_quadratic_bezier_curveto(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        parse_arguments!(self, absolute, SmoothQuadBezierCurveTo, [ point => parse_coord ])
+    }
+
+    /// Parse elliptical arc curve command.
+    fn parse_elliptical_arc(&mut self, absolute: IsAbsolute) -> Result<(), ()> {
+        // Parse a flag whose value is '0' or '1'; otherwise, return Err(()).
+        let parse_flag = |iter: &mut Peekable<Cloned<slice::Iter<u8>>>| match iter.next() {
+            Some(c) if c == b'0' || c == b'1' => Ok(ArcFlag(c == b'1')),
+            _ => Err(()),
+        };
+        parse_arguments!(self, absolute, EllipticalArc, [
+            rx => parse_number,
+            ry => parse_number,
+            angle => parse_number,
+            large_arc_flag => parse_flag,
+            sweep_flag => parse_flag,
+            point => parse_coord
+        ])
+    }
+}
+
+/// Parse a pair of numbers into CoordPair.
+fn parse_coord(iter: &mut Peekable<Cloned<slice::Iter<u8>>>) -> Result<CoordPair, ()> {
+    let x = parse_number(iter)?;
+    skip_comma_wsp(iter);
+    let y = parse_number(iter)?;
+    Ok(CoordPair::new(x, y))
+}
+
+/// This is a special version which parses the number for SVG Path. e.g. "M 0.6.5" should be parsed
+/// as MoveTo with a coordinate of ("0.6", ".5"), instead of treating 0.6.5 as a non-valid floating
+/// point number. In other words, the logic here is similar with that of
+/// tokenizer::consume_numeric, which also consumes the number as many as possible, but here the
+/// input is a Peekable and we only accept an integer of a floating point number.
+///
+/// The "number" syntax in https://www.w3.org/TR/SVG/paths.html#PathDataBNF
+fn parse_number(iter: &mut Peekable<Cloned<slice::Iter<u8>>>) -> Result<CSSFloat, ()> {
+    // 1. Check optional sign.
+    let sign = if iter
+        .peek()
+        .map_or(false, |&sign| sign == b'+' || sign == b'-')
+    {
+        if iter.next().unwrap() == b'-' {
+            -1.
+        } else {
+            1.
+        }
+    } else {
+        1.
+    };
+
+    // 2. Check integer part.
+    let mut integral_part: f64 = 0.;
+    let got_dot = if !iter.peek().map_or(false, |&n| n == b'.') {
+        // If the first digit in integer part is neither a dot nor a digit, this is not a number.
+        if iter.peek().map_or(true, |n| !n.is_ascii_digit()) {
+            return Err(());
+        }
+
+        while iter.peek().map_or(false, |n| n.is_ascii_digit()) {
+            integral_part = integral_part * 10. + (iter.next().unwrap() - b'0') as f64;
+        }
+
+        iter.peek().map_or(false, |&n| n == b'.')
+    } else {
+        true
+    };
+
+    // 3. Check fractional part.
+    let mut fractional_part: f64 = 0.;
+    if got_dot {
+        // Consume '.'.
+        iter.next();
+        // If the first digit in fractional part is not a digit, this is not a number.
+        if iter.peek().map_or(true, |n| !n.is_ascii_digit()) {
+            return Err(());
+        }
+
+        let mut factor = 0.1;
+        while iter.peek().map_or(false, |n| n.is_ascii_digit()) {
+            fractional_part += (iter.next().unwrap() - b'0') as f64 * factor;
+            factor *= 0.1;
+        }
+    }
+
+    let mut value = sign * (integral_part + fractional_part);
+
+    // 4. Check exp part. The segment name of SVG Path doesn't include 'E' or 'e', so it's ok to
+    //    treat the numbers after 'E' or 'e' are in the exponential part.
+    if iter.peek().map_or(false, |&exp| exp == b'E' || exp == b'e') {
+        // Consume 'E' or 'e'.
+        iter.next();
+        let exp_sign = if iter
+            .peek()
+            .map_or(false, |&sign| sign == b'+' || sign == b'-')
+        {
+            if iter.next().unwrap() == b'-' {
+                -1.
+            } else {
+                1.
+            }
+        } else {
+            1.
+        };
+
+        let mut exp: f64 = 0.;
+        while iter.peek().map_or(false, |n| n.is_ascii_digit()) {
+            exp = exp * 10. + (iter.next().unwrap() - b'0') as f64;
+        }
+
+        value *= f64::powf(10., exp * exp_sign);
+    }
+
+    if value.is_finite() {
+        Ok(value
+            .min(::std::f32::MAX as f64)
+            .max(::std::f32::MIN as f64) as CSSFloat)
+    } else {
+        Err(())
+    }
+}
+
+/// Skip all svg whitespaces, and return true if |iter| hasn't finished.
+#[inline]
+fn skip_wsp(iter: &mut Peekable<Cloned<slice::Iter<u8>>>) -> bool {
+    // Note: SVG 1.1 defines the whitespaces as \u{9}, \u{20}, \u{A}, \u{D}.
+    //       However, SVG 2 has one extra whitespace: \u{C}.
+    //       Therefore, we follow the newest spec for the definition of whitespace,
+    //       i.e. \u{9}, \u{20}, \u{A}, \u{C}, \u{D}.
+    while iter.peek().map_or(false, |c| c.is_ascii_whitespace()) {
+        iter.next();
+    }
+    iter.peek().is_some()
+}
+
+/// Skip all svg whitespaces and one comma, and return true if |iter| hasn't finished.
+#[inline]
+fn skip_comma_wsp(iter: &mut Peekable<Cloned<slice::Iter<u8>>>) -> bool {
+    if !skip_wsp(iter) {
+        return false;
+    }
+
+    if *iter.peek().unwrap() != b',' {
+        return true;
+    }
+    iter.next();
+
+    skip_wsp(iter)
+}
diff --git a/servo/components/style/values/specified/table.rs b/servo/components/style/values/specified/table.rs
new file mode 100644
index 0000000000..88f917ac78
--- /dev/null
+++ b/servo/components/style/values/specified/table.rs
@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS values related to tables.
+
+/// Specified values for the `caption-side` property.
+///
+/// Note that despite having "physical" names, these are actually interpreted
+/// according to the table's writing-mode: Top and Bottom are treated as
+/// block-start and -end respectively.
+///
+/// https://drafts.csswg.org/css-tables/#propdef-caption-side
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    MallocSizeOf,
+    Ord,
+    Parse,
+    PartialEq,
+    PartialOrd,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum CaptionSide {
+    Top,
+    Bottom,
+}
diff --git a/servo/components/style/values/specified/text.rs b/servo/components/style/values/specified/text.rs
new file mode 100644
index 0000000000..64a896cb27
--- /dev/null
+++ b/servo/components/style/values/specified/text.rs
@@ -0,0 +1,1154 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for text properties.
+
+use crate::parser::{Parse, ParserContext};
+use crate::properties::longhands::writing_mode::computed_value::T as SpecifiedWritingMode;
+use crate::values::computed::text::LineHeight as ComputedLineHeight;
+use crate::values::computed::text::TextEmphasisStyle as ComputedTextEmphasisStyle;
+use crate::values::computed::text::TextOverflow as ComputedTextOverflow;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics::text::InitialLetter as GenericInitialLetter;
+use crate::values::generics::text::LineHeight as GenericLineHeight;
+use crate::values::generics::text::{GenericTextDecorationLength, Spacing};
+use crate::values::specified::length::NonNegativeLengthPercentage;
+use crate::values::specified::length::{FontRelativeLength, Length};
+use crate::values::specified::length::{LengthPercentage, NoCalcLength};
+use crate::values::specified::{AllowQuirks, Integer, NonNegativeNumber, Number};
+use cssparser::{Parser, Token};
+use selectors::parser::SelectorParseErrorKind;
+use std::fmt::{self, Write};
+use style_traits::values::SequenceWriter;
+use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss};
+use style_traits::{KeywordsCollectFn, SpecifiedValueInfo};
+use unicode_segmentation::UnicodeSegmentation;
+
+/// A specified type for the `initial-letter` property.
+pub type InitialLetter = GenericInitialLetter<Number, Integer>;
+
+/// A specified value for the `letter-spacing` property.
+pub type LetterSpacing = Spacing<Length>;
+
+/// A specified value for the `word-spacing` property.
+pub type WordSpacing = Spacing<LengthPercentage>;
+
+/// A specified value for the `line-height` property.
+pub type LineHeight = GenericLineHeight<NonNegativeNumber, NonNegativeLengthPercentage>;
+
+/// A value for the `hyphenate-character` property.
+#[derive(
+    Clone,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum HyphenateCharacter {
+    /// `auto`
+    Auto,
+    /// `<string>`
+    String(crate::OwnedStr),
+}
+
+impl Parse for InitialLetter {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|i| i.expect_ident_matching("normal"))
+            .is_ok()
+        {
+            return Ok(GenericInitialLetter::Normal);
+        }
+        let size = Number::parse_at_least_one(context, input)?;
+        let sink = input
+            .try_parse(|i| Integer::parse_positive(context, i))
+            .ok();
+        Ok(GenericInitialLetter::Specified(size, sink))
+    }
+}
+
+impl Parse for LetterSpacing {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Spacing::parse_with(context, input, |c, i| {
+            Length::parse_quirky(c, i, AllowQuirks::Yes)
+        })
+    }
+}
+
+impl Parse for WordSpacing {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Spacing::parse_with(context, input, |c, i| {
+            LengthPercentage::parse_quirky(c, i, AllowQuirks::Yes)
+        })
+    }
+}
+
+impl ToComputedValue for LineHeight {
+    type ComputedValue = ComputedLineHeight;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        use crate::values::specified::length::FontBaseSize;
+        match *self {
+            GenericLineHeight::Normal => GenericLineHeight::Normal,
+            #[cfg(feature = "gecko")]
+            GenericLineHeight::MozBlockHeight => GenericLineHeight::MozBlockHeight,
+            GenericLineHeight::Number(number) => {
+                GenericLineHeight::Number(number.to_computed_value(context))
+            },
+            GenericLineHeight::Length(ref non_negative_lp) => {
+                let result = match non_negative_lp.0 {
+                    LengthPercentage::Length(NoCalcLength::Absolute(ref abs)) => {
+                        context.maybe_zoom_text(abs.to_computed_value(context))
+                    },
+                    LengthPercentage::Length(ref length) => length.to_computed_value(context),
+                    LengthPercentage::Percentage(ref p) => FontRelativeLength::Em(p.0)
+                        .to_computed_value(context, FontBaseSize::CurrentStyle),
+                    LengthPercentage::Calc(ref calc) => {
+                        let computed_calc =
+                            calc.to_computed_value_zoomed(context, FontBaseSize::CurrentStyle);
+                        let base = context.style().get_font().clone_font_size().computed_size();
+                        computed_calc.resolve(base)
+                    },
+                };
+                GenericLineHeight::Length(result.into())
+            },
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        match *computed {
+            GenericLineHeight::Normal => GenericLineHeight::Normal,
+            #[cfg(feature = "gecko")]
+            GenericLineHeight::MozBlockHeight => GenericLineHeight::MozBlockHeight,
+            GenericLineHeight::Number(ref number) => {
+                GenericLineHeight::Number(NonNegativeNumber::from_computed_value(number))
+            },
+            GenericLineHeight::Length(ref length) => {
+                GenericLineHeight::Length(NoCalcLength::from_computed_value(&length.0).into())
+            },
+        }
+    }
+}
+
+/// A generic value for the `text-overflow` property.
+#[derive(
+    Clone,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    Parse,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C, u8)]
+pub enum TextOverflowSide {
+    /// Clip inline content.
+    Clip,
+    /// Render ellipsis to represent clipped inline content.
+    Ellipsis,
+    /// Render a given string to represent clipped inline content.
+    String(crate::OwnedStr),
+}
+
+#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+/// text-overflow. Specifies rendering when inline content overflows its line box edge.
+pub struct TextOverflow {
+    /// First value. Applies to end line box edge if no second is supplied; line-left edge otherwise.
+    pub first: TextOverflowSide,
+    /// Second value. Applies to the line-right edge if supplied.
+    pub second: Option<TextOverflowSide>,
+}
+
+impl Parse for TextOverflow {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<TextOverflow, ParseError<'i>> {
+        let first = TextOverflowSide::parse(context, input)?;
+        let second = input
+            .try_parse(|input| TextOverflowSide::parse(context, input))
+            .ok();
+        Ok(TextOverflow { first, second })
+    }
+}
+
+impl ToComputedValue for TextOverflow {
+    type ComputedValue = ComputedTextOverflow;
+
+    #[inline]
+    fn to_computed_value(&self, _context: &Context) -> Self::ComputedValue {
+        if let Some(ref second) = self.second {
+            Self::ComputedValue {
+                first: self.first.clone(),
+                second: second.clone(),
+                sides_are_logical: false,
+            }
+        } else {
+            Self::ComputedValue {
+                first: TextOverflowSide::Clip,
+                second: self.first.clone(),
+                sides_are_logical: true,
+            }
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        if computed.sides_are_logical {
+            assert_eq!(computed.first, TextOverflowSide::Clip);
+            TextOverflow {
+                first: computed.second.clone(),
+                second: None,
+            }
+        } else {
+            TextOverflow {
+                first: computed.first.clone(),
+                second: Some(computed.second.clone()),
+            }
+        }
+    }
+}
+
+bitflags! {
+    #[derive(MallocSizeOf, Parse, Serialize, SpecifiedValueInfo, ToCss, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[css(bitflags(single = "none", mixed = "underline,overline,line-through,blink"))]
+    #[repr(C)]
+    /// Specified keyword values for the text-decoration-line property.
+    pub struct TextDecorationLine: u8 {
+        /// No text decoration line is specified.
+        const NONE = 0;
+        /// underline
+        const UNDERLINE = 1 << 0;
+        /// overline
+        const OVERLINE = 1 << 1;
+        /// line-through
+        const LINE_THROUGH = 1 << 2;
+        /// blink
+        const BLINK = 1 << 3;
+        /// Only set by presentation attributes
+        ///
+        /// Setting this will mean that text-decorations use the color
+        /// specified by `color` in quirks mode.
+        ///
+        /// For example, this gives <a href=foo><font color="red">text</font></a>
+        /// a red text decoration
+        #[cfg(feature = "gecko")]
+        const COLOR_OVERRIDE = 0x10;
+    }
+}
+
+impl Default for TextDecorationLine {
+    fn default() -> Self {
+        TextDecorationLine::NONE
+    }
+}
+
+impl TextDecorationLine {
+    #[inline]
+    /// Returns the initial value of text-decoration-line
+    pub fn none() -> Self {
+        TextDecorationLine::NONE
+    }
+}
+
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// Specified value of the text-transform property, stored in two parts:
+/// the case-related transforms (mutually exclusive, only one may be in effect), and others (non-exclusive).
+pub struct TextTransform {
+    /// Case transform, if any.
+    pub case_: TextTransformCase,
+    /// Non-case transforms.
+    pub other_: TextTransformOther,
+}
+
+impl TextTransform {
+    #[inline]
+    /// Returns the initial value of text-transform
+    pub fn none() -> Self {
+        TextTransform {
+            case_: TextTransformCase::None,
+            other_: TextTransformOther::empty(),
+        }
+    }
+    #[inline]
+    /// Returns whether the value is 'none'
+    pub fn is_none(&self) -> bool {
+        self.case_ == TextTransformCase::None && self.other_.is_empty()
+    }
+}
+
+// TODO: This can be simplified by deriving it.
+impl Parse for TextTransform {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut result = TextTransform::none();
+
+        // Case keywords are mutually exclusive; other transforms may co-occur.
+        loop {
+            let location = input.current_source_location();
+            let ident = match input.next() {
+                Ok(&Token::Ident(ref ident)) => ident,
+                Ok(other) => return Err(location.new_unexpected_token_error(other.clone())),
+                Err(..) => break,
+            };
+
+            match_ignore_ascii_case! { ident,
+                "none" if result.is_none() => {
+                    return Ok(result);
+                },
+                "uppercase" if result.case_ == TextTransformCase::None => {
+                    result.case_ = TextTransformCase::Uppercase
+                },
+                "lowercase" if result.case_ == TextTransformCase::None => {
+                    result.case_ = TextTransformCase::Lowercase
+                },
+                "capitalize" if result.case_ == TextTransformCase::None => {
+                    result.case_ = TextTransformCase::Capitalize
+                },
+                "full-width" if !result.other_.intersects(TextTransformOther::FULL_WIDTH) => {
+                    result.other_.insert(TextTransformOther::FULL_WIDTH)
+                },
+                "full-size-kana" if !result.other_.intersects(TextTransformOther::FULL_SIZE_KANA) => {
+                    result.other_.insert(TextTransformOther::FULL_SIZE_KANA)
+                },
+                _ => return Err(location.new_custom_error(
+                    SelectorParseErrorKind::UnexpectedIdent(ident.clone())
+                )),
+            }
+        }
+
+        if result.is_none() {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        } else {
+            Ok(result)
+        }
+    }
+}
+
+impl ToCss for TextTransform {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.is_none() {
+            return dest.write_str("none");
+        }
+
+        if self.case_ != TextTransformCase::None {
+            self.case_.to_css(dest)?;
+            if !self.other_.is_empty() {
+                dest.write_str(" ")?;
+            }
+        }
+
+        self.other_.to_css(dest)
+    }
+}
+
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(C)]
+/// Specified keyword values for case transforms in the text-transform property. (These are exclusive.)
+pub enum TextTransformCase {
+    /// No case transform.
+    None,
+    /// All uppercase.
+    Uppercase,
+    /// All lowercase.
+    Lowercase,
+    /// Capitalize each word.
+    Capitalize,
+}
+
+bitflags! {
+    #[derive(MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[value_info(other_values = "none,full-width,full-size-kana")]
+    #[repr(C)]
+    /// Specified keyword values for non-case transforms in the text-transform property. (Non-exclusive.)
+    pub struct TextTransformOther: u8 {
+        /// full-width
+        const FULL_WIDTH = 1 << 0;
+        /// full-size-kana
+        const FULL_SIZE_KANA = 1 << 1;
+    }
+}
+
+impl ToCss for TextTransformOther {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        let mut writer = SequenceWriter::new(dest, " ");
+        let mut any = false;
+        macro_rules! maybe_write {
+            ($ident:ident => $str:expr) => {
+                if self.contains(TextTransformOther::$ident) {
+                    writer.raw_item($str)?;
+                    any = true;
+                }
+            };
+        }
+
+        maybe_write!(FULL_WIDTH => "full-width");
+        maybe_write!(FULL_SIZE_KANA => "full-size-kana");
+
+        debug_assert!(any || self.is_empty());
+
+        Ok(())
+    }
+}
+
+/// Specified and computed value of text-align-last.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[repr(u8)]
+pub enum TextAlignLast {
+    Auto,
+    Start,
+    End,
+    Left,
+    Right,
+    Center,
+    Justify,
+}
+
+/// Specified value of text-align keyword value.
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    Hash,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+#[repr(u8)]
+pub enum TextAlignKeyword {
+    Start,
+    Left,
+    Right,
+    Center,
+    #[cfg(any(feature = "gecko", feature = "servo-layout-2013"))]
+    Justify,
+    #[css(skip)]
+    #[cfg(feature = "gecko")]
+    Char,
+    End,
+    #[cfg(feature = "gecko")]
+    MozCenter,
+    #[cfg(feature = "gecko")]
+    MozLeft,
+    #[cfg(feature = "gecko")]
+    MozRight,
+    #[cfg(feature = "servo-layout-2013")]
+    ServoCenter,
+    #[cfg(feature = "servo-layout-2013")]
+    ServoLeft,
+    #[cfg(feature = "servo-layout-2013")]
+    ServoRight,
+}
+
+/// Specified value of text-align property.
+#[derive(
+    Clone, Copy, Debug, Eq, Hash, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem,
+)]
+pub enum TextAlign {
+    /// Keyword value of text-align property.
+    Keyword(TextAlignKeyword),
+    /// `match-parent` value of text-align property. It has a different handling
+    /// unlike other keywords.
+    #[cfg(feature = "gecko")]
+    MatchParent,
+    /// This is how we implement the following HTML behavior from
+    /// https://html.spec.whatwg.org/#tables-2:
+    ///
+    ///     User agents are expected to have a rule in their user agent style sheet
+    ///     that matches th elements that have a parent node whose computed value
+    ///     for the 'text-align' property is its initial value, whose declaration
+    ///     block consists of just a single declaration that sets the 'text-align'
+    ///     property to the value 'center'.
+    ///
+    /// Since selectors can't depend on the ancestor styles, we implement it with a
+    /// magic value that computes to the right thing. Since this is an
+    /// implementation detail, it shouldn't be exposed to web content.
+    #[cfg(feature = "gecko")]
+    #[parse(condition = "ParserContext::in_ua_or_chrome_sheet")]
+    MozCenterOrInherit,
+}
+
+impl ToComputedValue for TextAlign {
+    type ComputedValue = TextAlignKeyword;
+
+    #[inline]
+    fn to_computed_value(&self, _context: &Context) -> Self::ComputedValue {
+        match *self {
+            TextAlign::Keyword(key) => key,
+            #[cfg(feature = "gecko")]
+            TextAlign::MatchParent => {
+                // on the root <html> element we should still respect the dir
+                // but the parent dir of that element is LTR even if it's <html dir=rtl>
+                // and will only be RTL if certain prefs have been set.
+                // In that case, the default behavior here will set it to left,
+                // but we want to set it to right -- instead set it to the default (`start`),
+                // which will do the right thing in this case (but not the general case)
+                if _context.builder.is_root_element {
+                    return TextAlignKeyword::Start;
+                }
+                let parent = _context
+                    .builder
+                    .get_parent_inherited_text()
+                    .clone_text_align();
+                let ltr = _context.builder.inherited_writing_mode().is_bidi_ltr();
+                match (parent, ltr) {
+                    (TextAlignKeyword::Start, true) => TextAlignKeyword::Left,
+                    (TextAlignKeyword::Start, false) => TextAlignKeyword::Right,
+                    (TextAlignKeyword::End, true) => TextAlignKeyword::Right,
+                    (TextAlignKeyword::End, false) => TextAlignKeyword::Left,
+                    _ => parent,
+                }
+            },
+            #[cfg(feature = "gecko")]
+            TextAlign::MozCenterOrInherit => {
+                let parent = _context
+                    .builder
+                    .get_parent_inherited_text()
+                    .clone_text_align();
+                if parent == TextAlignKeyword::Start {
+                    TextAlignKeyword::Center
+                } else {
+                    parent
+                }
+            },
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        TextAlign::Keyword(*computed)
+    }
+}
+
+fn fill_mode_is_default_and_shape_exists(
+    fill: &TextEmphasisFillMode,
+    shape: &Option<TextEmphasisShapeKeyword>,
+) -> bool {
+    shape.is_some() && fill.is_filled()
+}
+
+/// Specified value of text-emphasis-style property.
+///
+/// https://drafts.csswg.org/css-text-decor/#propdef-text-emphasis-style
+#[derive(Clone, Debug, MallocSizeOf, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+#[allow(missing_docs)]
+pub enum TextEmphasisStyle {
+    /// [ <fill> || <shape> ]
+    Keyword {
+        #[css(contextual_skip_if = "fill_mode_is_default_and_shape_exists")]
+        fill: TextEmphasisFillMode,
+        shape: Option<TextEmphasisShapeKeyword>,
+    },
+    /// `none`
+    None,
+    /// `<string>` (of which only the first grapheme cluster will be used).
+    String(crate::OwnedStr),
+}
+
+/// Fill mode for the text-emphasis-style property
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum TextEmphasisFillMode {
+    /// `filled`
+    Filled,
+    /// `open`
+    Open,
+}
+
+impl TextEmphasisFillMode {
+    /// Whether the value is `filled`.
+    #[inline]
+    pub fn is_filled(&self) -> bool {
+        matches!(*self, TextEmphasisFillMode::Filled)
+    }
+}
+
+/// Shape keyword for the text-emphasis-style property
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToCss,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum TextEmphasisShapeKeyword {
+    /// `dot`
+    Dot,
+    /// `circle`
+    Circle,
+    /// `double-circle`
+    DoubleCircle,
+    /// `triangle`
+    Triangle,
+    /// `sesame`
+    Sesame,
+}
+
+impl ToComputedValue for TextEmphasisStyle {
+    type ComputedValue = ComputedTextEmphasisStyle;
+
+    #[inline]
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            TextEmphasisStyle::Keyword { fill, shape } => {
+                let shape = shape.unwrap_or_else(|| {
+                    // FIXME(emilio, bug 1572958): This should set the
+                    // rule_cache_conditions properly.
+                    //
+                    // Also should probably use WritingMode::is_vertical rather
+                    // than the computed value of the `writing-mode` property.
+                    if context.style().get_inherited_box().clone_writing_mode() ==
+                        SpecifiedWritingMode::HorizontalTb
+                    {
+                        TextEmphasisShapeKeyword::Circle
+                    } else {
+                        TextEmphasisShapeKeyword::Sesame
+                    }
+                });
+                ComputedTextEmphasisStyle::Keyword { fill, shape }
+            },
+            TextEmphasisStyle::None => ComputedTextEmphasisStyle::None,
+            TextEmphasisStyle::String(ref s) => {
+                // Passing `true` to iterate over extended grapheme clusters, following
+                // recommendation at http://www.unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries
+                //
+                // FIXME(emilio): Doing this at computed value time seems wrong.
+                // The spec doesn't say that this should be a computed-value
+                // time operation. This is observable from getComputedStyle().
+                let s = s.graphemes(true).next().unwrap_or("").to_string();
+                ComputedTextEmphasisStyle::String(s.into())
+            },
+        }
+    }
+
+    #[inline]
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        match *computed {
+            ComputedTextEmphasisStyle::Keyword { fill, shape } => TextEmphasisStyle::Keyword {
+                fill,
+                shape: Some(shape),
+            },
+            ComputedTextEmphasisStyle::None => TextEmphasisStyle::None,
+            ComputedTextEmphasisStyle::String(ref string) => {
+                TextEmphasisStyle::String(string.clone())
+            },
+        }
+    }
+}
+
+impl Parse for TextEmphasisStyle {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input
+            .try_parse(|input| input.expect_ident_matching("none"))
+            .is_ok()
+        {
+            return Ok(TextEmphasisStyle::None);
+        }
+
+        if let Ok(s) = input.try_parse(|i| i.expect_string().map(|s| s.as_ref().to_owned())) {
+            // Handle <string>
+            return Ok(TextEmphasisStyle::String(s.into()));
+        }
+
+        // Handle a pair of keywords
+        let mut shape = input.try_parse(TextEmphasisShapeKeyword::parse).ok();
+        let fill = input.try_parse(TextEmphasisFillMode::parse).ok();
+        if shape.is_none() {
+            shape = input.try_parse(TextEmphasisShapeKeyword::parse).ok();
+        }
+
+        if shape.is_none() && fill.is_none() {
+            return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+        }
+
+        // If a shape keyword is specified but neither filled nor open is
+        // specified, filled is assumed.
+        let fill = fill.unwrap_or(TextEmphasisFillMode::Filled);
+
+        // We cannot do the same because the default `<shape>` depends on the
+        // computed writing-mode.
+        Ok(TextEmphasisStyle::Keyword { fill, shape })
+    }
+}
+
+bitflags! {
+    #[derive(MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem, Parse, ToCss)]
+    #[repr(C)]
+    #[css(bitflags(mixed="over,under,left,right", validate_mixed="Self::validate_and_simplify"))]
+    /// Values for text-emphasis-position:
+    /// <https://drafts.csswg.org/css-text-decor/#text-emphasis-position-property>
+    pub struct TextEmphasisPosition: u8 {
+        /// Draws marks to the right of the text in vertical writing mode.
+        const OVER = 1 << 0;
+        /// Draw marks under the text in horizontal writing mode.
+        const UNDER = 1 << 1;
+        /// Draw marks to the left of the text in vertical writing mode.
+        const LEFT = 1 << 2;
+        /// Draws marks to the right of the text in vertical writing mode.
+        const RIGHT = 1 << 3;
+    }
+}
+
+impl TextEmphasisPosition {
+    fn validate_and_simplify(&mut self) -> bool {
+        if self.intersects(Self::OVER) == self.intersects(Self::UNDER) {
+            return false;
+        }
+
+        if self.intersects(Self::LEFT) {
+            return !self.intersects(Self::RIGHT);
+        }
+
+        self.remove(Self::RIGHT); // Right is the default
+        true
+    }
+}
+
+/// Values for the `word-break` property.
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum WordBreak {
+    Normal,
+    BreakAll,
+    KeepAll,
+    /// The break-word value, needed for compat.
+    ///
+    /// Specifying `word-break: break-word` makes `overflow-wrap` behave as
+    /// `anywhere`, and `word-break` behave like `normal`.
+    #[cfg(feature = "gecko")]
+    BreakWord,
+}
+
+/// Values for the `text-justify` CSS property.
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum TextJustify {
+    Auto,
+    None,
+    InterWord,
+    // See https://drafts.csswg.org/css-text-3/#valdef-text-justify-distribute
+    // and https://github.com/w3c/csswg-drafts/issues/6156 for the alias.
+    #[parse(aliases = "distribute")]
+    InterCharacter,
+}
+
+/// Values for the `-moz-control-character-visibility` CSS property.
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum MozControlCharacterVisibility {
+    Hidden,
+    Visible,
+}
+
+impl Default for MozControlCharacterVisibility {
+    fn default() -> Self {
+        if static_prefs::pref!("layout.css.control-characters.visible") {
+            Self::Visible
+        } else {
+            Self::Hidden
+        }
+    }
+}
+
+/// Values for the `line-break` property.
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum LineBreak {
+    Auto,
+    Loose,
+    Normal,
+    Strict,
+    Anywhere,
+}
+
+/// Values for the `overflow-wrap` property.
+#[repr(u8)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum OverflowWrap {
+    Normal,
+    BreakWord,
+    Anywhere,
+}
+
+/// Implements text-decoration-skip-ink which takes the keywords auto | none | all
+///
+/// https://drafts.csswg.org/css-text-decor-4/#text-decoration-skip-ink-property
+#[repr(u8)]
+#[cfg_attr(feature = "servo", derive(Deserialize, Serialize))]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum TextDecorationSkipInk {
+    Auto,
+    None,
+    All,
+}
+
+/// Implements type for `text-decoration-thickness` property
+pub type TextDecorationLength = GenericTextDecorationLength<LengthPercentage>;
+
+impl TextDecorationLength {
+    /// `Auto` value.
+    #[inline]
+    pub fn auto() -> Self {
+        GenericTextDecorationLength::Auto
+    }
+
+    /// Whether this is the `Auto` value.
+    #[inline]
+    pub fn is_auto(&self) -> bool {
+        matches!(*self, GenericTextDecorationLength::Auto)
+    }
+}
+
+bitflags! {
+    #[derive(MallocSizeOf, SpecifiedValueInfo, ToComputedValue, ToResolvedValue, ToShmem)]
+    #[value_info(other_values = "auto,from-font,under,left,right")]
+    #[repr(C)]
+    /// Specified keyword values for the text-underline-position property.
+    /// (Non-exclusive, but not all combinations are allowed: the spec grammar gives
+    /// `auto | [ from-font | under ] || [ left | right ]`.)
+    /// https://drafts.csswg.org/css-text-decor-4/#text-underline-position-property
+    pub struct TextUnderlinePosition: u8 {
+        /// Use automatic positioning below the alphabetic baseline.
+        const AUTO = 0;
+        /// Use underline position from the first available font.
+        const FROM_FONT = 1 << 0;
+        /// Below the glyph box.
+        const UNDER = 1 << 1;
+        /// In vertical mode, place to the left of the text.
+        const LEFT = 1 << 2;
+        /// In vertical mode, place to the right of the text.
+        const RIGHT = 1 << 3;
+    }
+}
+
+// TODO: This can be derived with some care.
+impl Parse for TextUnderlinePosition {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<TextUnderlinePosition, ParseError<'i>> {
+        let mut result = TextUnderlinePosition::empty();
+
+        loop {
+            let location = input.current_source_location();
+            let ident = match input.next() {
+                Ok(&Token::Ident(ref ident)) => ident,
+                Ok(other) => return Err(location.new_unexpected_token_error(other.clone())),
+                Err(..) => break,
+            };
+
+            match_ignore_ascii_case! { ident,
+                "auto" if result.is_empty() => {
+                    return Ok(result);
+                },
+                "from-font" if !result.intersects(TextUnderlinePosition::FROM_FONT |
+                                                  TextUnderlinePosition::UNDER) => {
+                    result.insert(TextUnderlinePosition::FROM_FONT);
+                },
+                "under" if !result.intersects(TextUnderlinePosition::FROM_FONT |
+                                              TextUnderlinePosition::UNDER) => {
+                    result.insert(TextUnderlinePosition::UNDER);
+                },
+                "left" if !result.intersects(TextUnderlinePosition::LEFT |
+                                             TextUnderlinePosition::RIGHT) => {
+                    result.insert(TextUnderlinePosition::LEFT);
+                },
+                "right" if !result.intersects(TextUnderlinePosition::LEFT |
+                                              TextUnderlinePosition::RIGHT) => {
+                    result.insert(TextUnderlinePosition::RIGHT);
+                },
+                _ => return Err(location.new_custom_error(
+                    SelectorParseErrorKind::UnexpectedIdent(ident.clone())
+                )),
+            }
+        }
+
+        if !result.is_empty() {
+            Ok(result)
+        } else {
+            Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+        }
+    }
+}
+
+impl ToCss for TextUnderlinePosition {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.is_empty() {
+            return dest.write_str("auto");
+        }
+
+        let mut writer = SequenceWriter::new(dest, " ");
+        let mut any = false;
+
+        macro_rules! maybe_write {
+            ($ident:ident => $str:expr) => {
+                if self.contains(TextUnderlinePosition::$ident) {
+                    any = true;
+                    writer.raw_item($str)?;
+                }
+            };
+        }
+
+        maybe_write!(FROM_FONT => "from-font");
+        maybe_write!(UNDER => "under");
+        maybe_write!(LEFT => "left");
+        maybe_write!(RIGHT => "right");
+
+        debug_assert!(any);
+
+        Ok(())
+    }
+}
+
+/// Values for `ruby-position` property
+#[repr(u8)]
+#[derive(
+    Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToComputedValue, ToResolvedValue, ToShmem,
+)]
+#[allow(missing_docs)]
+pub enum RubyPosition {
+    AlternateOver,
+    AlternateUnder,
+    Over,
+    Under,
+}
+
+impl Parse for RubyPosition {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<RubyPosition, ParseError<'i>> {
+        // Parse alternate before
+        let alternate = input
+            .try_parse(|i| i.expect_ident_matching("alternate"))
+            .is_ok();
+        if alternate && input.is_exhausted() {
+            return Ok(RubyPosition::AlternateOver);
+        }
+        // Parse over / under
+        let over = try_match_ident_ignore_ascii_case! { input,
+            "over" => true,
+            "under" => false,
+        };
+        // Parse alternate after
+        let alternate = alternate ||
+            input
+                .try_parse(|i| i.expect_ident_matching("alternate"))
+                .is_ok();
+
+        Ok(match (over, alternate) {
+            (true, true) => RubyPosition::AlternateOver,
+            (false, true) => RubyPosition::AlternateUnder,
+            (true, false) => RubyPosition::Over,
+            (false, false) => RubyPosition::Under,
+        })
+    }
+}
+
+impl ToCss for RubyPosition {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str(match self {
+            RubyPosition::AlternateOver => "alternate",
+            RubyPosition::AlternateUnder => "alternate under",
+            RubyPosition::Over => "over",
+            RubyPosition::Under => "under",
+        })
+    }
+}
+
+impl SpecifiedValueInfo for RubyPosition {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&["alternate", "over", "under"])
+    }
+}
diff --git a/servo/components/style/values/specified/time.rs b/servo/components/style/values/specified/time.rs
new file mode 100644
index 0000000000..aba3f0a828
--- /dev/null
+++ b/servo/components/style/values/specified/time.rs
@@ -0,0 +1,176 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified time values.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::time::Time as ComputedTime;
+use crate::values::computed::{Context, ToComputedValue};
+use crate::values::specified::calc::CalcNode;
+use crate::values::CSSFloat;
+use cssparser::{Parser, Token};
+use std::fmt::{self, Write};
+use style_traits::values::specified::AllowedNumericType;
+use style_traits::{CssWriter, ParseError, SpecifiedValueInfo, StyleParseErrorKind, ToCss};
+
+/// A time value according to CSS-VALUES § 6.2.
+#[derive(Clone, Copy, Debug, MallocSizeOf, PartialEq, ToShmem)]
+pub struct Time {
+    seconds: CSSFloat,
+    unit: TimeUnit,
+    was_calc: bool,
+}
+
+/// A time unit.
+#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq, ToShmem)]
+pub enum TimeUnit {
+    /// `s`
+    Second,
+    /// `ms`
+    Millisecond,
+}
+
+impl Time {
+    /// Returns a time value that represents `seconds` seconds.
+    pub fn from_seconds(seconds: CSSFloat) -> Self {
+        Time {
+            seconds,
+            unit: TimeUnit::Second,
+            was_calc: false,
+        }
+    }
+
+    /// Returns `0s`.
+    pub fn zero() -> Self {
+        Self::from_seconds(0.0)
+    }
+
+    /// Returns the time in fractional seconds.
+    pub fn seconds(self) -> CSSFloat {
+        self.seconds
+    }
+
+    /// Parses a time according to CSS-VALUES § 6.2.
+    pub fn parse_dimension(value: CSSFloat, unit: &str, was_calc: bool) -> Result<Time, ()> {
+        let (seconds, unit) = match_ignore_ascii_case! { unit,
+            "s" => (value, TimeUnit::Second),
+            "ms" => (value / 1000.0, TimeUnit::Millisecond),
+            _ => return Err(())
+        };
+
+        Ok(Time {
+            seconds,
+            unit,
+            was_calc,
+        })
+    }
+
+    /// Returns a `Time` value from a CSS `calc()` expression.
+    pub fn from_calc(seconds: CSSFloat) -> Self {
+        Time {
+            seconds,
+            unit: TimeUnit::Second,
+            was_calc: true,
+        }
+    }
+
+    fn parse_with_clamping_mode<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+        clamping_mode: AllowedNumericType,
+    ) -> Result<Self, ParseError<'i>> {
+        use style_traits::ParsingMode;
+
+        let location = input.current_source_location();
+        match *input.next()? {
+            // Note that we generally pass ParserContext to is_ok() to check
+            // that the ParserMode of the ParserContext allows all numeric
+            // values for SMIL regardless of clamping_mode, but in this Time
+            // value case, the value does not animate for SMIL at all, so we use
+            // ParsingMode::DEFAULT directly.
+            Token::Dimension {
+                value, ref unit, ..
+            } if clamping_mode.is_ok(ParsingMode::DEFAULT, value) => {
+                Time::parse_dimension(value, unit, /* from_calc = */ false)
+                    .map_err(|()| location.new_custom_error(StyleParseErrorKind::UnspecifiedError))
+            },
+            Token::Function(ref name) => {
+                let function = CalcNode::math_function(name, location)?;
+                let time = CalcNode::parse_time(context, input, function)?;
+
+                // FIXME(emilio): Rejecting calc() at parse time is wrong,
+                // was_calc should probably be replaced by calc_clamping_mode or
+                // something like we do for numbers, or we should do the
+                // clamping here instead (simpler, but technically incorrect,
+                // though still more correct than this!).
+                if !clamping_mode.is_ok(ParsingMode::DEFAULT, time.seconds) {
+                    return Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError));
+                }
+
+                Ok(time)
+            },
+            ref t => return Err(location.new_unexpected_token_error(t.clone())),
+        }
+    }
+
+    /// Parses a non-negative time value.
+    pub fn parse_non_negative<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::NonNegative)
+    }
+}
+
+impl ToComputedValue for Time {
+    type ComputedValue = ComputedTime;
+
+    fn to_computed_value(&self, _context: &Context) -> Self::ComputedValue {
+        ComputedTime::from_seconds(self.seconds())
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        Time {
+            seconds: computed.seconds(),
+            unit: TimeUnit::Second,
+            was_calc: false,
+        }
+    }
+}
+
+impl Parse for Time {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Self::parse_with_clamping_mode(context, input, AllowedNumericType::All)
+    }
+}
+
+impl ToCss for Time {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        if self.was_calc {
+            dest.write_str("calc(")?;
+        }
+        match self.unit {
+            TimeUnit::Second => {
+                self.seconds.to_css(dest)?;
+                dest.write_str("s")?;
+            },
+            TimeUnit::Millisecond => {
+                (self.seconds * 1000.).to_css(dest)?;
+                dest.write_str("ms")?;
+            },
+        }
+        if self.was_calc {
+            dest.write_str(")")?;
+        }
+        Ok(())
+    }
+}
+
+impl SpecifiedValueInfo for Time {}
diff --git a/servo/components/style/values/specified/transform.rs b/servo/components/style/values/specified/transform.rs
new file mode 100644
index 0000000000..c10b79a089
--- /dev/null
+++ b/servo/components/style/values/specified/transform.rs
@@ -0,0 +1,487 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for CSS values that are related to transformations.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::computed::{Context, LengthPercentage as ComputedLengthPercentage};
+use crate::values::computed::{Percentage as ComputedPercentage, ToComputedValue};
+use crate::values::generics::transform as generic;
+use crate::values::generics::transform::{Matrix, Matrix3D};
+use crate::values::specified::position::{
+    HorizontalPositionKeyword, Side, VerticalPositionKeyword,
+};
+use crate::values::specified::{
+    self, Angle, Integer, Length, LengthPercentage, Number, NumberOrPercentage,
+};
+use crate::Zero;
+use cssparser::Parser;
+use style_traits::{ParseError, StyleParseErrorKind};
+
+pub use crate::values::generics::transform::TransformStyle;
+
+/// A single operation in a specified CSS `transform`
+pub type TransformOperation =
+    generic::TransformOperation<Angle, Number, Length, Integer, LengthPercentage>;
+
+/// A specified CSS `transform`
+pub type Transform = generic::Transform<TransformOperation>;
+
+/// The specified value of a CSS `<transform-origin>`
+pub type TransformOrigin = generic::TransformOrigin<
+    OriginComponent<HorizontalPositionKeyword>,
+    OriginComponent<VerticalPositionKeyword>,
+    Length,
+>;
+
+impl TransformOrigin {
+    /// Returns the initial specified value for `transform-origin`.
+    #[inline]
+    pub fn initial_value() -> Self {
+        Self::new(
+            OriginComponent::Length(LengthPercentage::Percentage(ComputedPercentage(0.5))),
+            OriginComponent::Length(LengthPercentage::Percentage(ComputedPercentage(0.5))),
+            Length::zero(),
+        )
+    }
+
+    /// Returns the `0 0` value.
+    pub fn zero_zero() -> Self {
+        Self::new(
+            OriginComponent::Length(LengthPercentage::zero()),
+            OriginComponent::Length(LengthPercentage::zero()),
+            Length::zero(),
+        )
+    }
+}
+
+impl Transform {
+    /// Internal parse function for deciding if we wish to accept prefixed values or not
+    ///
+    /// `transform` allows unitless zero angles as an exception, see:
+    /// https://github.com/w3c/csswg-drafts/issues/1162
+    fn parse_internal<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        use style_traits::{Separator, Space};
+
+        if input
+            .try_parse(|input| input.expect_ident_matching("none"))
+            .is_ok()
+        {
+            return Ok(generic::Transform::none());
+        }
+
+        Ok(generic::Transform(
+            Space::parse(input, |input| {
+                let function = input.expect_function()?.clone();
+                input.parse_nested_block(|input| {
+                    let location = input.current_source_location();
+                    let result = match_ignore_ascii_case! { &function,
+                        "matrix" => {
+                            let a = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let b = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let c = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let d = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            // Standard matrix parsing.
+                            let e = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let f = Number::parse(context, input)?;
+                            Ok(generic::TransformOperation::Matrix(Matrix { a, b, c, d, e, f }))
+                        },
+                        "matrix3d" => {
+                            let m11 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m12 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m13 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m14 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m21 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m22 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m23 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m24 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m31 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m32 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m33 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m34 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            // Standard matrix3d parsing.
+                            let m41 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m42 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m43 = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let m44 = Number::parse(context, input)?;
+                            Ok(generic::TransformOperation::Matrix3D(Matrix3D {
+                                m11, m12, m13, m14,
+                                m21, m22, m23, m24,
+                                m31, m32, m33, m34,
+                                m41, m42, m43, m44,
+                            }))
+                        },
+                        "translate" => {
+                            let sx = specified::LengthPercentage::parse(context, input)?;
+                            if input.try_parse(|input| input.expect_comma()).is_ok() {
+                                let sy = specified::LengthPercentage::parse(context, input)?;
+                                Ok(generic::TransformOperation::Translate(sx, sy))
+                            } else {
+                                Ok(generic::TransformOperation::Translate(sx, Zero::zero()))
+                            }
+                        },
+                        "translatex" => {
+                            let tx = specified::LengthPercentage::parse(context, input)?;
+                            Ok(generic::TransformOperation::TranslateX(tx))
+                        },
+                        "translatey" => {
+                            let ty = specified::LengthPercentage::parse(context, input)?;
+                            Ok(generic::TransformOperation::TranslateY(ty))
+                        },
+                        "translatez" => {
+                            let tz = specified::Length::parse(context, input)?;
+                            Ok(generic::TransformOperation::TranslateZ(tz))
+                        },
+                        "translate3d" => {
+                            let tx = specified::LengthPercentage::parse(context, input)?;
+                            input.expect_comma()?;
+                            let ty = specified::LengthPercentage::parse(context, input)?;
+                            input.expect_comma()?;
+                            let tz = specified::Length::parse(context, input)?;
+                            Ok(generic::TransformOperation::Translate3D(tx, ty, tz))
+                        },
+                        "scale" => {
+                            let sx = NumberOrPercentage::parse(context, input)?.to_number();
+                            if input.try_parse(|input| input.expect_comma()).is_ok() {
+                                let sy = NumberOrPercentage::parse(context, input)?.to_number();
+                                Ok(generic::TransformOperation::Scale(sx, sy))
+                            } else {
+                                Ok(generic::TransformOperation::Scale(sx, sx))
+                            }
+                        },
+                        "scalex" => {
+                            let sx = NumberOrPercentage::parse(context, input)?.to_number();
+                            Ok(generic::TransformOperation::ScaleX(sx))
+                        },
+                        "scaley" => {
+                            let sy = NumberOrPercentage::parse(context, input)?.to_number();
+                            Ok(generic::TransformOperation::ScaleY(sy))
+                        },
+                        "scalez" => {
+                            let sz = NumberOrPercentage::parse(context, input)?.to_number();
+                            Ok(generic::TransformOperation::ScaleZ(sz))
+                        },
+                        "scale3d" => {
+                            let sx = NumberOrPercentage::parse(context, input)?.to_number();
+                            input.expect_comma()?;
+                            let sy = NumberOrPercentage::parse(context, input)?.to_number();
+                            input.expect_comma()?;
+                            let sz = NumberOrPercentage::parse(context, input)?.to_number();
+                            Ok(generic::TransformOperation::Scale3D(sx, sy, sz))
+                        },
+                        "rotate" => {
+                            let theta = specified::Angle::parse_with_unitless(context, input)?;
+                            Ok(generic::TransformOperation::Rotate(theta))
+                        },
+                        "rotatex" => {
+                            let theta = specified::Angle::parse_with_unitless(context, input)?;
+                            Ok(generic::TransformOperation::RotateX(theta))
+                        },
+                        "rotatey" => {
+                            let theta = specified::Angle::parse_with_unitless(context, input)?;
+                            Ok(generic::TransformOperation::RotateY(theta))
+                        },
+                        "rotatez" => {
+                            let theta = specified::Angle::parse_with_unitless(context, input)?;
+                            Ok(generic::TransformOperation::RotateZ(theta))
+                        },
+                        "rotate3d" => {
+                            let ax = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let ay = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let az = Number::parse(context, input)?;
+                            input.expect_comma()?;
+                            let theta = specified::Angle::parse_with_unitless(context, input)?;
+                            // TODO(gw): Check that the axis can be normalized.
+                            Ok(generic::TransformOperation::Rotate3D(ax, ay, az, theta))
+                        },
+                        "skew" => {
+                            let ax = specified::Angle::parse_with_unitless(context, input)?;
+                            if input.try_parse(|input| input.expect_comma()).is_ok() {
+                                let ay = specified::Angle::parse_with_unitless(context, input)?;
+                                Ok(generic::TransformOperation::Skew(ax, ay))
+                            } else {
+                                Ok(generic::TransformOperation::Skew(ax, Zero::zero()))
+                            }
+                        },
+                        "skewx" => {
+                            let theta = specified::Angle::parse_with_unitless(context, input)?;
+                            Ok(generic::TransformOperation::SkewX(theta))
+                        },
+                        "skewy" => {
+                            let theta = specified::Angle::parse_with_unitless(context, input)?;
+                            Ok(generic::TransformOperation::SkewY(theta))
+                        },
+                        "perspective" => {
+                            let p = match input.try_parse(|input| specified::Length::parse_non_negative(context, input)) {
+                                Ok(p) => generic::PerspectiveFunction::Length(p),
+                                Err(..) => {
+                                    input.expect_ident_matching("none")?;
+                                    generic::PerspectiveFunction::None
+                                }
+                            };
+                            Ok(generic::TransformOperation::Perspective(p))
+                        },
+                        _ => Err(()),
+                    };
+                    result.map_err(|()| {
+                        location.new_custom_error(StyleParseErrorKind::UnexpectedFunction(
+                            function.clone(),
+                        ))
+                    })
+                })
+            })?
+            .into(),
+        ))
+    }
+}
+
+impl Parse for Transform {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Transform::parse_internal(context, input)
+    }
+}
+
+/// The specified value of a component of a CSS `<transform-origin>`.
+#[derive(Clone, Debug, MallocSizeOf, Parse, PartialEq, SpecifiedValueInfo, ToCss, ToShmem)]
+pub enum OriginComponent<S> {
+    /// `center`
+    Center,
+    /// `<length-percentage>`
+    Length(LengthPercentage),
+    /// `<side>`
+    Side(S),
+}
+
+impl Parse for TransformOrigin {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let parse_depth = |input: &mut Parser| {
+            input
+                .try_parse(|i| Length::parse(context, i))
+                .unwrap_or(Length::zero())
+        };
+        match input.try_parse(|i| OriginComponent::parse(context, i)) {
+            Ok(x_origin @ OriginComponent::Center) => {
+                if let Ok(y_origin) = input.try_parse(|i| OriginComponent::parse(context, i)) {
+                    let depth = parse_depth(input);
+                    return Ok(Self::new(x_origin, y_origin, depth));
+                }
+                let y_origin = OriginComponent::Center;
+                if let Ok(x_keyword) = input.try_parse(HorizontalPositionKeyword::parse) {
+                    let x_origin = OriginComponent::Side(x_keyword);
+                    let depth = parse_depth(input);
+                    return Ok(Self::new(x_origin, y_origin, depth));
+                }
+                let depth = Length::from_px(0.);
+                return Ok(Self::new(x_origin, y_origin, depth));
+            },
+            Ok(x_origin) => {
+                if let Ok(y_origin) = input.try_parse(|i| OriginComponent::parse(context, i)) {
+                    let depth = parse_depth(input);
+                    return Ok(Self::new(x_origin, y_origin, depth));
+                }
+                let y_origin = OriginComponent::Center;
+                let depth = Length::from_px(0.);
+                return Ok(Self::new(x_origin, y_origin, depth));
+            },
+            Err(_) => {},
+        }
+        let y_keyword = VerticalPositionKeyword::parse(input)?;
+        let y_origin = OriginComponent::Side(y_keyword);
+        if let Ok(x_keyword) = input.try_parse(HorizontalPositionKeyword::parse) {
+            let x_origin = OriginComponent::Side(x_keyword);
+            let depth = parse_depth(input);
+            return Ok(Self::new(x_origin, y_origin, depth));
+        }
+        if input
+            .try_parse(|i| i.expect_ident_matching("center"))
+            .is_ok()
+        {
+            let x_origin = OriginComponent::Center;
+            let depth = parse_depth(input);
+            return Ok(Self::new(x_origin, y_origin, depth));
+        }
+        let x_origin = OriginComponent::Center;
+        let depth = Length::from_px(0.);
+        Ok(Self::new(x_origin, y_origin, depth))
+    }
+}
+
+impl<S> ToComputedValue for OriginComponent<S>
+where
+    S: Side,
+{
+    type ComputedValue = ComputedLengthPercentage;
+
+    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue {
+        match *self {
+            OriginComponent::Center => {
+                ComputedLengthPercentage::new_percent(ComputedPercentage(0.5))
+            },
+            OriginComponent::Length(ref length) => length.to_computed_value(context),
+            OriginComponent::Side(ref keyword) => {
+                let p = ComputedPercentage(if keyword.is_start() { 0. } else { 1. });
+                ComputedLengthPercentage::new_percent(p)
+            },
+        }
+    }
+
+    fn from_computed_value(computed: &Self::ComputedValue) -> Self {
+        OriginComponent::Length(ToComputedValue::from_computed_value(computed))
+    }
+}
+
+impl<S> OriginComponent<S> {
+    /// `0%`
+    pub fn zero() -> Self {
+        OriginComponent::Length(LengthPercentage::Percentage(ComputedPercentage::zero()))
+    }
+}
+
+/// A specified CSS `rotate`
+pub type Rotate = generic::Rotate<Number, Angle>;
+
+impl Parse for Rotate {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(generic::Rotate::None);
+        }
+
+        // Parse <angle> or [ x | y | z | <number>{3} ] && <angle>.
+        //
+        // The rotate axis and angle could be in any order, so we parse angle twice to cover
+        // two cases. i.e. `<number>{3} <angle>` or `<angle> <number>{3}`
+        let angle = input
+            .try_parse(|i| specified::Angle::parse(context, i))
+            .ok();
+        let axis = input
+            .try_parse(|i| {
+                Ok(try_match_ident_ignore_ascii_case! { i,
+                    "x" => (Number::new(1.), Number::new(0.), Number::new(0.)),
+                    "y" => (Number::new(0.), Number::new(1.), Number::new(0.)),
+                    "z" => (Number::new(0.), Number::new(0.), Number::new(1.)),
+                })
+            })
+            .or_else(|_: ParseError| -> Result<_, ParseError> {
+                input.try_parse(|i| {
+                    Ok((
+                        Number::parse(context, i)?,
+                        Number::parse(context, i)?,
+                        Number::parse(context, i)?,
+                    ))
+                })
+            })
+            .ok();
+        let angle = match angle {
+            Some(a) => a,
+            None => specified::Angle::parse(context, input)?,
+        };
+
+        Ok(match axis {
+            Some((x, y, z)) => generic::Rotate::Rotate3D(x, y, z, angle),
+            None => generic::Rotate::Rotate(angle),
+        })
+    }
+}
+
+/// A specified CSS `translate`
+pub type Translate = generic::Translate<LengthPercentage, Length>;
+
+impl Parse for Translate {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(generic::Translate::None);
+        }
+
+        let tx = specified::LengthPercentage::parse(context, input)?;
+        if let Ok(ty) = input.try_parse(|i| specified::LengthPercentage::parse(context, i)) {
+            if let Ok(tz) = input.try_parse(|i| specified::Length::parse(context, i)) {
+                // 'translate: <length-percentage> <length-percentage> <length>'
+                return Ok(generic::Translate::Translate(tx, ty, tz));
+            }
+
+            // translate: <length-percentage> <length-percentage>'
+            return Ok(generic::Translate::Translate(
+                tx,
+                ty,
+                specified::Length::zero(),
+            ));
+        }
+
+        // 'translate: <length-percentage> '
+        Ok(generic::Translate::Translate(
+            tx,
+            specified::LengthPercentage::zero(),
+            specified::Length::zero(),
+        ))
+    }
+}
+
+/// A specified CSS `scale`
+pub type Scale = generic::Scale<Number>;
+
+impl Parse for Scale {
+    /// Scale accepts <number> | <percentage>, so we parse it as NumberOrPercentage,
+    /// and then convert into an Number if it's a Percentage.
+    /// https://github.com/w3c/csswg-drafts/pull/4396
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try_parse(|i| i.expect_ident_matching("none")).is_ok() {
+            return Ok(generic::Scale::None);
+        }
+
+        let sx = NumberOrPercentage::parse(context, input)?.to_number();
+        if let Ok(sy) = input.try_parse(|i| NumberOrPercentage::parse(context, i)) {
+            let sy = sy.to_number();
+            if let Ok(sz) = input.try_parse(|i| NumberOrPercentage::parse(context, i)) {
+                // 'scale: <number> <number> <number>'
+                return Ok(generic::Scale::Scale(sx, sy, sz.to_number()));
+            }
+
+            // 'scale: <number> <number>'
+            return Ok(generic::Scale::Scale(sx, sy, Number::new(1.0)));
+        }
+
+        // 'scale: <number>'
+        Ok(generic::Scale::Scale(sx, sx, Number::new(1.0)))
+    }
+}
diff --git a/servo/components/style/values/specified/ui.rs b/servo/components/style/values/specified/ui.rs
new file mode 100644
index 0000000000..0c656faab2
--- /dev/null
+++ b/servo/components/style/values/specified/ui.rs
@@ -0,0 +1,232 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Specified types for UI properties.
+
+use crate::parser::{Parse, ParserContext};
+use crate::values::generics::ui as generics;
+use crate::values::specified::color::Color;
+use crate::values::specified::image::Image;
+use crate::values::specified::Number;
+use cssparser::Parser;
+use std::fmt::{self, Write};
+use style_traits::{
+    CssWriter, KeywordsCollectFn, ParseError, SpecifiedValueInfo, StyleParseErrorKind, ToCss,
+};
+
+/// A specified value for the `cursor` property.
+pub type Cursor = generics::GenericCursor<CursorImage>;
+
+/// A specified value for item of `image cursors`.
+pub type CursorImage = generics::GenericCursorImage<Image, Number>;
+
+impl Parse for Cursor {
+    /// cursor: [<url> [<number> <number>]?]# [auto | default | ...]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        let mut images = vec![];
+        loop {
+            match input.try_parse(|input| CursorImage::parse(context, input)) {
+                Ok(image) => images.push(image),
+                Err(_) => break,
+            }
+            input.expect_comma()?;
+        }
+        Ok(Self {
+            images: images.into(),
+            keyword: CursorKind::parse(input)?,
+        })
+    }
+}
+
+impl Parse for CursorImage {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        use crate::Zero;
+
+        let image = Image::parse_only_url(context, input)?;
+        let mut has_hotspot = false;
+        let mut hotspot_x = Number::zero();
+        let mut hotspot_y = Number::zero();
+
+        if let Ok(x) = input.try_parse(|input| Number::parse(context, input)) {
+            has_hotspot = true;
+            hotspot_x = x;
+            hotspot_y = Number::parse(context, input)?;
+        }
+
+        Ok(Self {
+            image,
+            has_hotspot,
+            hotspot_x,
+            hotspot_y,
+        })
+    }
+}
+
+// This trait is manually implemented because we don't support the whole <image>
+// syntax for cursors
+impl SpecifiedValueInfo for CursorImage {
+    fn collect_completion_keywords(f: KeywordsCollectFn) {
+        f(&["url", "image-set"]);
+    }
+}
+/// Specified value of `-moz-force-broken-image-icon`
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    MallocSizeOf,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(transparent)]
+pub struct BoolInteger(pub bool);
+
+impl BoolInteger {
+    /// Returns 0
+    #[inline]
+    pub fn zero() -> Self {
+        Self(false)
+    }
+}
+
+impl Parse for BoolInteger {
+    fn parse<'i, 't>(
+        _context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        // We intentionally don't support calc values here.
+        match input.expect_integer()? {
+            0 => Ok(Self(false)),
+            1 => Ok(Self(true)),
+            _ => Err(input.new_custom_error(StyleParseErrorKind::UnspecifiedError)),
+        }
+    }
+}
+
+impl ToCss for BoolInteger {
+    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
+    where
+        W: Write,
+    {
+        dest.write_str(if self.0 { "1" } else { "0" })
+    }
+}
+
+/// A specified value for `scrollbar-color` property
+pub type ScrollbarColor = generics::ScrollbarColor<Color>;
+
+impl Parse for ScrollbarColor {
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        if input.try_parse(|i| i.expect_ident_matching("auto")).is_ok() {
+            return Ok(generics::ScrollbarColor::Auto);
+        }
+        Ok(generics::ScrollbarColor::Colors {
+            thumb: Color::parse(context, input)?,
+            track: Color::parse(context, input)?,
+        })
+    }
+}
+
+/// The specified value for the `user-select` property.
+///
+/// https://drafts.csswg.org/css-ui-4/#propdef-user-select
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum UserSelect {
+    Auto,
+    Text,
+    #[parse(aliases = "-moz-none")]
+    None,
+    /// Force selection of all children.
+    All,
+}
+
+/// The keywords allowed in the Cursor property.
+///
+/// https://drafts.csswg.org/css-ui-4/#propdef-cursor
+#[allow(missing_docs)]
+#[derive(
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    FromPrimitive,
+    MallocSizeOf,
+    Parse,
+    PartialEq,
+    SpecifiedValueInfo,
+    ToComputedValue,
+    ToCss,
+    ToResolvedValue,
+    ToShmem,
+)]
+#[repr(u8)]
+pub enum CursorKind {
+    None,
+    Default,
+    Pointer,
+    ContextMenu,
+    Help,
+    Progress,
+    Wait,
+    Cell,
+    Crosshair,
+    Text,
+    VerticalText,
+    Alias,
+    Copy,
+    Move,
+    NoDrop,
+    NotAllowed,
+    #[parse(aliases = "-moz-grab")]
+    Grab,
+    #[parse(aliases = "-moz-grabbing")]
+    Grabbing,
+    EResize,
+    NResize,
+    NeResize,
+    NwResize,
+    SResize,
+    SeResize,
+    SwResize,
+    WResize,
+    EwResize,
+    NsResize,
+    NeswResize,
+    NwseResize,
+    ColResize,
+    RowResize,
+    AllScroll,
+    #[parse(aliases = "-moz-zoom-in")]
+    ZoomIn,
+    #[parse(aliases = "-moz-zoom-out")]
+    ZoomOut,
+    Auto,
+}
diff --git a/servo/components/style/values/specified/url.rs b/servo/components/style/values/specified/url.rs
new file mode 100644
index 0000000000..17ecbe0d5e
--- /dev/null
+++ b/servo/components/style/values/specified/url.rs
@@ -0,0 +1,15 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+//! Common handling for the specified value CSS url() values.
+
+use crate::values::generics::url::GenericUrlOrNone;
+
+#[cfg(feature = "gecko")]
+pub use crate::gecko::url::{SpecifiedImageUrl, SpecifiedUrl};
+#[cfg(feature = "servo")]
+pub use crate::servo::url::{SpecifiedImageUrl, SpecifiedUrl};
+
+/// Specified <url> | <none>
+pub type UrlOrNone = GenericUrlOrNone<SpecifiedUrl>;