path: root/components/style/values/computed/length.rs

/* 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 http://mozilla.org/MPL/2.0/. */

//! `<length>` computed values, and related ones.

use app_units::{Au, AU_PER_PX};
use ordered_float::NotNaN;
use std::fmt;
use style_traits::ToCss;
use style_traits::values::specified::AllowedLengthType;
use super::{Number, ToComputedValue, Context};
use values::{Auto, CSSFloat, Either, ExtremumLength, None_, Normal, specified};
use values::specified::length::{AbsoluteLength, FontBaseSize, FontRelativeLength, ViewportPercentageLength};

pub use super::image::Image;
pub use values::specified::{Angle, BorderStyle, Time, UrlOrNone};

impl ToComputedValue for specified::NoCalcLength {
    type ComputedValue = Au;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> Au {
        match *self {
            specified::NoCalcLength::Absolute(length) =>
                length.to_computed_value(context),
            specified::NoCalcLength::FontRelative(length) =>
                length.to_computed_value(context, FontBaseSize::CurrentStyle),
            specified::NoCalcLength::ViewportPercentage(length) =>
                length.to_computed_value(context.viewport_size()),
            specified::NoCalcLength::ServoCharacterWidth(length) =>
                length.to_computed_value(context.style().get_font().clone_font_size()),
            #[cfg(feature = "gecko")]
            specified::NoCalcLength::Physical(length) =>
                length.to_computed_value(context),
        }
    }

    #[inline]
    fn from_computed_value(computed: &Au) -> Self {
        specified::NoCalcLength::Absolute(AbsoluteLength::Px(computed.to_f32_px()))
    }
}

impl ToComputedValue for specified::Length {
    type ComputedValue = Au;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> Au {
        match *self {
            specified::Length::NoCalc(l) => l.to_computed_value(context),
            specified::Length::Calc(ref calc) => calc.to_computed_value(context).length(),
        }
    }

    #[inline]
    fn from_computed_value(computed: &Au) -> Self {
        specified::Length::NoCalc(specified::NoCalcLength::from_computed_value(computed))
    }
}

#[derive(Clone, PartialEq, Copy, Debug)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub struct CalcLengthOrPercentage {
    pub clamping_mode: AllowedLengthType,
    length: Au,
    pub percentage: Option<CSSFloat>,
}

impl CalcLengthOrPercentage {
    /// Returns a new `CalcLengthOrPercentage`.
    #[inline]
    pub fn new(length: Au, percentage: Option<CSSFloat>) -> Self {
        Self::with_clamping_mode(length, percentage, AllowedLengthType::All)
    }

    /// Returns a new `CalcLengthOrPercentage` with a specific clamping mode.
    #[inline]
    pub fn with_clamping_mode(length: Au,
                              percentage: Option<CSSFloat>,
                              clamping_mode: AllowedLengthType)
                              -> Self {
        Self {
            clamping_mode: clamping_mode,
            length: length,
            percentage: percentage,
        }
    }

    /// Returns this `calc()` as a `<length>`.
    ///
    /// Panics in debug mode if a percentage is present in the expression.
    #[inline]
    pub fn length(&self) -> Au {
        debug_assert!(self.percentage.is_none());
        self.clamping_mode.clamp(self.length)
    }

    /// Returns the `<length>` component of this `calc()`, unclamped.
    #[inline]
    pub fn unclamped_length(&self) -> Au {
        self.length
    }

    #[inline]
    #[allow(missing_docs)]
    pub fn percentage(&self) -> CSSFloat {
        self.percentage.unwrap_or(0.)
    }

    /// 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 to_used_value(&self, container_len: Option<Au>) -> Option<Au> {
        match (container_len, self.percentage) {
            (Some(len), Some(percent)) => {
                Some(self.clamping_mode.clamp(self.length + len.scale_by(percent)))
            },
            (_, None) => Some(self.length()),
            _ => None,
        }
    }
}

impl From<LengthOrPercentage> for CalcLengthOrPercentage {
    fn from(len: LengthOrPercentage) -> CalcLengthOrPercentage {
        match len {
            LengthOrPercentage::Percentage(this) => {
                CalcLengthOrPercentage::new(Au(0), Some(this))
            }
            LengthOrPercentage::Length(this) => {
                CalcLengthOrPercentage::new(this, None)
            }
            LengthOrPercentage::Calc(this) => {
                this
            }
        }
    }
}

impl From<LengthOrPercentageOrAuto> for Option<CalcLengthOrPercentage> {
    fn from(len: LengthOrPercentageOrAuto) -> Option<CalcLengthOrPercentage> {
        match len {
            LengthOrPercentageOrAuto::Percentage(this) => {
                Some(CalcLengthOrPercentage::new(Au(0), Some(this)))
            }
            LengthOrPercentageOrAuto::Length(this) => {
                Some(CalcLengthOrPercentage::new(this, None))
            }
            LengthOrPercentageOrAuto::Calc(this) => {
                Some(this)
            }
            LengthOrPercentageOrAuto::Auto => {
                None
            }
        }
    }
}

impl ToCss for CalcLengthOrPercentage {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match (self.length, self.percentage) {
            (l, Some(p)) if l == Au(0) => write!(dest, "{}%", p * 100.),
            (l, Some(p)) => write!(dest, "calc({}px + {}%)", Au::to_px(l), p * 100.),
            (l, None) => write!(dest, "{}px", Au::to_px(l)),
        }
    }
}

impl ToComputedValue for specified::CalcLengthOrPercentage {
    type ComputedValue = CalcLengthOrPercentage;

    fn to_computed_value(&self, context: &Context) -> CalcLengthOrPercentage {
        let mut length = Au(0);

        if let Some(absolute) = self.absolute {
            length += absolute;
        }

        for val in &[self.vw.map(ViewportPercentageLength::Vw),
                     self.vh.map(ViewportPercentageLength::Vh),
                     self.vmin.map(ViewportPercentageLength::Vmin),
                     self.vmax.map(ViewportPercentageLength::Vmax)] {
            if let Some(val) = *val {
                length += val.to_computed_value(context.viewport_size());
            }
        }

        for val in &[self.ch.map(FontRelativeLength::Ch),
                     self.em.map(FontRelativeLength::Em),
                     self.ex.map(FontRelativeLength::Ex),
                     self.rem.map(FontRelativeLength::Rem)] {
            if let Some(val) = *val {
                length += val.to_computed_value(context, FontBaseSize::CurrentStyle);
            }
        }

        CalcLengthOrPercentage {
            clamping_mode: self.clamping_mode,
            length: length,
            percentage: self.percentage,
        }
    }

    #[inline]
    fn from_computed_value(computed: &CalcLengthOrPercentage) -> Self {
        specified::CalcLengthOrPercentage {
            clamping_mode: computed.clamping_mode,
            absolute: Some(computed.length),
            percentage: computed.percentage,
            ..Default::default()
        }
    }
}

#[derive(PartialEq, Clone, Copy)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum LengthOrPercentage {
    Length(Au),
    Percentage(CSSFloat),
    Calc(CalcLengthOrPercentage),
}

impl LengthOrPercentage {
    #[inline]
    #[allow(missing_docs)]
    pub fn zero() -> LengthOrPercentage {
        LengthOrPercentage::Length(Au(0))
    }

    #[inline]
    /// 1px length value for SVG defaults
    pub fn one() -> LengthOrPercentage {
        LengthOrPercentage::Length(Au(AU_PER_PX))
    }

    /// Returns true if the computed value is absolute 0 or 0%.
    ///
    /// (Returns false for calc() values, even if ones that may resolve to zero.)
    #[inline]
    pub fn is_definitely_zero(&self) -> bool {
        use self::LengthOrPercentage::*;
        match *self {
            Length(Au(0)) => true,
            Percentage(p) => p == 0.0,
            Length(_) | Calc(_) => false
        }
    }

    #[allow(missing_docs)]
    pub fn to_hash_key(&self) -> (Au, NotNaN<f32>) {
        use self::LengthOrPercentage::*;
        match *self {
            Length(l) => (l, NotNaN::new(0.0).unwrap()),
            Percentage(p) => (Au(0), NotNaN::new(p).unwrap()),
            Calc(c) => (c.unclamped_length(), NotNaN::new(c.percentage()).unwrap()),
        }
    }

    /// Returns the used value.
    pub fn to_used_value(&self, containing_length: Au) -> Au {
        match *self {
            LengthOrPercentage::Length(length) => length,
            LengthOrPercentage::Percentage(p) => containing_length.scale_by(p),
            LengthOrPercentage::Calc(ref calc) => {
                calc.to_used_value(Some(containing_length)).unwrap()
            },
        }
    }
}

impl fmt::Debug for LengthOrPercentage {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            LengthOrPercentage::Length(length) => write!(f, "{:?}", length),
            LengthOrPercentage::Percentage(percentage) => write!(f, "{}%", percentage * 100.),
            LengthOrPercentage::Calc(calc) => write!(f, "{:?}", calc),
        }
    }
}

impl ToComputedValue for specified::LengthOrPercentage {
    type ComputedValue = LengthOrPercentage;

    fn to_computed_value(&self, context: &Context) -> LengthOrPercentage {
        match *self {
            specified::LengthOrPercentage::Length(ref value) => {
                LengthOrPercentage::Length(value.to_computed_value(context))
            }
            specified::LengthOrPercentage::Percentage(value) => {
                LengthOrPercentage::Percentage(value.0)
            }
            specified::LengthOrPercentage::Calc(ref calc) => {
                LengthOrPercentage::Calc(calc.to_computed_value(context))
            }
        }
    }

    fn from_computed_value(computed: &LengthOrPercentage) -> Self {
        match *computed {
            LengthOrPercentage::Length(value) => {
                specified::LengthOrPercentage::Length(
                    ToComputedValue::from_computed_value(&value)
                )
            }
            LengthOrPercentage::Percentage(value) => {
                specified::LengthOrPercentage::Percentage(specified::Percentage(value))
            }
            LengthOrPercentage::Calc(ref calc) => {
                specified::LengthOrPercentage::Calc(
                    Box::new(ToComputedValue::from_computed_value(calc))
                )
            }
        }
    }
}

impl ToCss for LengthOrPercentage {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            LengthOrPercentage::Length(length) => length.to_css(dest),
            LengthOrPercentage::Percentage(percentage)
            => write!(dest, "{}%", percentage * 100.),
            LengthOrPercentage::Calc(calc) => calc.to_css(dest),
        }
    }
}

#[derive(PartialEq, Clone, Copy)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum LengthOrPercentageOrAuto {
    Length(Au),
    Percentage(CSSFloat),
    Auto,
    Calc(CalcLengthOrPercentage),
}

impl LengthOrPercentageOrAuto {
    /// Returns true if the computed value is absolute 0 or 0%.
    ///
    /// (Returns false for calc() values, even if ones that may resolve to zero.)
    #[inline]
    pub fn is_definitely_zero(&self) -> bool {
        use self::LengthOrPercentageOrAuto::*;
        match *self {
            Length(Au(0)) => true,
            Percentage(p) => p == 0.0,
            Length(_) | Calc(_) | Auto => false
        }
    }
}

impl fmt::Debug for LengthOrPercentageOrAuto {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            LengthOrPercentageOrAuto::Length(length) => write!(f, "{:?}", length),
            LengthOrPercentageOrAuto::Percentage(percentage) => write!(f, "{}%", percentage * 100.),
            LengthOrPercentageOrAuto::Auto => write!(f, "auto"),
            LengthOrPercentageOrAuto::Calc(calc) => write!(f, "{:?}", calc),
        }
    }
}

impl ToComputedValue for specified::LengthOrPercentageOrAuto {
    type ComputedValue = LengthOrPercentageOrAuto;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> LengthOrPercentageOrAuto {
        match *self {
            specified::LengthOrPercentageOrAuto::Length(ref value) => {
                LengthOrPercentageOrAuto::Length(value.to_computed_value(context))
            }
            specified::LengthOrPercentageOrAuto::Percentage(value) => {
                LengthOrPercentageOrAuto::Percentage(value.0)
            }
            specified::LengthOrPercentageOrAuto::Auto => {
                LengthOrPercentageOrAuto::Auto
            }
            specified::LengthOrPercentageOrAuto::Calc(ref calc) => {
                LengthOrPercentageOrAuto::Calc(calc.to_computed_value(context))
            }
        }
    }

    #[inline]
    fn from_computed_value(computed: &LengthOrPercentageOrAuto) -> Self {
        match *computed {
            LengthOrPercentageOrAuto::Auto => specified::LengthOrPercentageOrAuto::Auto,
            LengthOrPercentageOrAuto::Length(value) => {
                specified::LengthOrPercentageOrAuto::Length(
                    ToComputedValue::from_computed_value(&value)
                )
            }
            LengthOrPercentageOrAuto::Percentage(value) => {
                specified::LengthOrPercentageOrAuto::Percentage(specified::Percentage(value))
            }
            LengthOrPercentageOrAuto::Calc(calc) => {
                specified::LengthOrPercentageOrAuto::Calc(
                    Box::new(ToComputedValue::from_computed_value(&calc))
                )
            }
        }
    }
}

impl ToCss for LengthOrPercentageOrAuto {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            LengthOrPercentageOrAuto::Length(length) => length.to_css(dest),
            LengthOrPercentageOrAuto::Percentage(percentage)
            => write!(dest, "{}%", percentage * 100.),
            LengthOrPercentageOrAuto::Auto => dest.write_str("auto"),
            LengthOrPercentageOrAuto::Calc(calc) => calc.to_css(dest),
        }
    }
}

#[derive(PartialEq, Clone, Copy)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum LengthOrPercentageOrAutoOrContent {
    Length(Au),
    Percentage(CSSFloat),
    Calc(CalcLengthOrPercentage),
    Auto,
    Content
}

impl fmt::Debug for LengthOrPercentageOrAutoOrContent {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            LengthOrPercentageOrAutoOrContent::Length(length) => write!(f, "{:?}", length),
            LengthOrPercentageOrAutoOrContent::Percentage(percentage) => write!(f, "{}%", percentage * 100.),
            LengthOrPercentageOrAutoOrContent::Calc(calc) => write!(f, "{:?}", calc),
            LengthOrPercentageOrAutoOrContent::Auto => write!(f, "auto"),
            LengthOrPercentageOrAutoOrContent::Content => write!(f, "content")
        }
    }
}

impl ToComputedValue for specified::LengthOrPercentageOrAutoOrContent {
    type ComputedValue = LengthOrPercentageOrAutoOrContent;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> LengthOrPercentageOrAutoOrContent {
        match *self {
            specified::LengthOrPercentageOrAutoOrContent::Length(ref value) => {
                LengthOrPercentageOrAutoOrContent::Length(value.to_computed_value(context))
            },
            specified::LengthOrPercentageOrAutoOrContent::Percentage(value) => {
                LengthOrPercentageOrAutoOrContent::Percentage(value.0)
            },
            specified::LengthOrPercentageOrAutoOrContent::Calc(ref calc) => {
                LengthOrPercentageOrAutoOrContent::Calc(calc.to_computed_value(context))
            },
            specified::LengthOrPercentageOrAutoOrContent::Auto => {
                LengthOrPercentageOrAutoOrContent::Auto
            },
            specified::LengthOrPercentageOrAutoOrContent::Content => {
                LengthOrPercentageOrAutoOrContent::Content
            }
        }
    }


    #[inline]
    fn from_computed_value(computed: &LengthOrPercentageOrAutoOrContent) -> Self {
        match *computed {
            LengthOrPercentageOrAutoOrContent::Auto => {
                specified::LengthOrPercentageOrAutoOrContent::Auto
            }
            LengthOrPercentageOrAutoOrContent::Content => {
                specified::LengthOrPercentageOrAutoOrContent::Content
            }
            LengthOrPercentageOrAutoOrContent::Length(value) => {
                specified::LengthOrPercentageOrAutoOrContent::Length(
                    ToComputedValue::from_computed_value(&value)
                )
            }
            LengthOrPercentageOrAutoOrContent::Percentage(value) => {
                specified::LengthOrPercentageOrAutoOrContent::Percentage(specified::Percentage(value))
            }
            LengthOrPercentageOrAutoOrContent::Calc(calc) => {
                specified::LengthOrPercentageOrAutoOrContent::Calc(
                    Box::new(ToComputedValue::from_computed_value(&calc))
                )
            }
        }
    }
}

impl ToCss for LengthOrPercentageOrAutoOrContent {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            LengthOrPercentageOrAutoOrContent::Length(length) => length.to_css(dest),
            LengthOrPercentageOrAutoOrContent::Percentage(percentage)
            => write!(dest, "{}%", percentage * 100.),
            LengthOrPercentageOrAutoOrContent::Calc(calc) => calc.to_css(dest),
            LengthOrPercentageOrAutoOrContent::Auto => dest.write_str("auto"),
            LengthOrPercentageOrAutoOrContent::Content => dest.write_str("content")
        }
    }
}

#[derive(PartialEq, Clone, Copy)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum LengthOrPercentageOrNone {
    Length(Au),
    Percentage(CSSFloat),
    Calc(CalcLengthOrPercentage),
    None,
}

impl LengthOrPercentageOrNone {
    /// Returns the used value.
    pub fn to_used_value(&self, containing_length: Au) -> Option<Au> {
        match *self {
            LengthOrPercentageOrNone::None => None,
            LengthOrPercentageOrNone::Length(length) => Some(length),
            LengthOrPercentageOrNone::Percentage(percent) => Some(containing_length.scale_by(percent)),
            LengthOrPercentageOrNone::Calc(ref calc) => calc.to_used_value(Some(containing_length)),
        }
    }
}

impl fmt::Debug for LengthOrPercentageOrNone {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            LengthOrPercentageOrNone::Length(length) => write!(f, "{:?}", length),
            LengthOrPercentageOrNone::Percentage(percentage) => write!(f, "{}%", percentage * 100.),
            LengthOrPercentageOrNone::Calc(calc) => write!(f, "{:?}", calc),
            LengthOrPercentageOrNone::None => write!(f, "none"),
        }
    }
}

impl ToComputedValue for specified::LengthOrPercentageOrNone {
    type ComputedValue = LengthOrPercentageOrNone;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> LengthOrPercentageOrNone {
        match *self {
            specified::LengthOrPercentageOrNone::Length(ref value) => {
                LengthOrPercentageOrNone::Length(value.to_computed_value(context))
            }
            specified::LengthOrPercentageOrNone::Percentage(value) => {
                LengthOrPercentageOrNone::Percentage(value.0)
            }
            specified::LengthOrPercentageOrNone::Calc(ref calc) => {
                LengthOrPercentageOrNone::Calc(calc.to_computed_value(context))
            }
            specified::LengthOrPercentageOrNone::None => {
                LengthOrPercentageOrNone::None
            }
        }
    }

    #[inline]
    fn from_computed_value(computed: &LengthOrPercentageOrNone) -> Self {
        match *computed {
            LengthOrPercentageOrNone::None => specified::LengthOrPercentageOrNone::None,
            LengthOrPercentageOrNone::Length(value) => {
                specified::LengthOrPercentageOrNone::Length(
                    ToComputedValue::from_computed_value(&value)
                )
            }
            LengthOrPercentageOrNone::Percentage(value) => {
                specified::LengthOrPercentageOrNone::Percentage(specified::Percentage(value))
            }
            LengthOrPercentageOrNone::Calc(calc) => {
                specified::LengthOrPercentageOrNone::Calc(
                    Box::new(ToComputedValue::from_computed_value(&calc))
                )
            }
        }
    }
}

impl ToCss for LengthOrPercentageOrNone {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            LengthOrPercentageOrNone::Length(length) => length.to_css(dest),
            LengthOrPercentageOrNone::Percentage(percentage) =>
                write!(dest, "{}%", percentage * 100.),
            LengthOrPercentageOrNone::Calc(calc) => calc.to_css(dest),
            LengthOrPercentageOrNone::None => dest.write_str("none"),
        }
    }
}

/// A computed `<length>` value.
pub type Length = Au;

/// Either a computed `<length>` or the `none` keyword.
pub type LengthOrNone = Either<Length, None_>;

/// Either a computed `<length>` or the `auto` keyword.
pub type LengthOrAuto = Either<Length, Auto>;

/// Either a computed `<length>` or a `<number>` value.
pub type LengthOrNumber = Either<Length, Number>;

/// Either a computed `<length>` or the `normal` keyword.
pub type LengthOrNormal = Either<Length, Normal>;

/// A value suitable for a `min-width`, `min-height`, `width` or `height` property.
/// See specified/values/length.rs for more details.
#[derive(Debug, Copy, Clone, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum MozLength {
    LengthOrPercentageOrAuto(LengthOrPercentageOrAuto),
    ExtremumLength(ExtremumLength),
}

impl MozLength {
    /// Returns the `auto` value.
    pub fn auto() -> Self {
        MozLength::LengthOrPercentageOrAuto(LengthOrPercentageOrAuto::Auto)
    }
}

impl ToComputedValue for specified::MozLength {
    type ComputedValue = MozLength;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> MozLength {
        match *self {
            specified::MozLength::LengthOrPercentageOrAuto(ref lopoa) => {
                MozLength::LengthOrPercentageOrAuto(lopoa.to_computed_value(context))
            }
            specified::MozLength::ExtremumLength(ref ext) => {
                MozLength::ExtremumLength(ext.clone())
            }
        }
    }

    #[inline]
    fn from_computed_value(computed: &MozLength) -> Self {
        match *computed {
            MozLength::LengthOrPercentageOrAuto(ref lopoa) =>
                specified::MozLength::LengthOrPercentageOrAuto(
                    specified::LengthOrPercentageOrAuto::from_computed_value(&lopoa)),
            MozLength::ExtremumLength(ref ext) =>
                specified::MozLength::ExtremumLength(ext.clone()),
        }
    }
}

impl ToCss for MozLength {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            MozLength::LengthOrPercentageOrAuto(lopoa) =>
                lopoa.to_css(dest),
            MozLength::ExtremumLength(ext) =>
                ext.to_css(dest),
        }
    }
}

/// A value suitable for a `max-width` or `max-height` property.
/// See specified/values/length.rs for more details.
#[derive(Debug, Copy, Clone, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[allow(missing_docs)]
pub enum MaxLength {
    LengthOrPercentageOrNone(LengthOrPercentageOrNone),
    ExtremumLength(ExtremumLength),
}

impl MaxLength {
    /// Returns the `none` value.
    pub fn none() -> Self {
        MaxLength::LengthOrPercentageOrNone(LengthOrPercentageOrNone::None)
    }
}
impl ToComputedValue for specified::MaxLength {
    type ComputedValue = MaxLength;

    #[inline]
    fn to_computed_value(&self, context: &Context) -> MaxLength {
        match *self {
            specified::MaxLength::LengthOrPercentageOrNone(ref lopon) => {
                MaxLength::LengthOrPercentageOrNone(lopon.to_computed_value(context))
            }
            specified::MaxLength::ExtremumLength(ref ext) => {
                MaxLength::ExtremumLength(ext.clone())
            }
        }
    }

    #[inline]
    fn from_computed_value(computed: &MaxLength) -> Self {
        match *computed {
            MaxLength::LengthOrPercentageOrNone(ref lopon) =>
                specified::MaxLength::LengthOrPercentageOrNone(
                    specified::LengthOrPercentageOrNone::from_computed_value(&lopon)),
            MaxLength::ExtremumLength(ref ext) =>
                specified::MaxLength::ExtremumLength(ext.clone()),
        }
    }
}

impl ToCss for MaxLength {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            MaxLength::LengthOrPercentageOrNone(lopon) =>
                lopon.to_css(dest),
            MaxLength::ExtremumLength(ext) =>
                ext.to_css(dest),
        }
    }
}