servo/components/style/values/computed/mod.rs
author Bogdan Tara <btara@mozilla.com>
Thu, 10 Jan 2019 18:49:22 +0200
changeset 510378 842b7a62d9cefd5030c5561d536af8414899af7a
parent 510357 c66c00f7329619d53bc14ec615a0d92f06b6a892
child 510486 8c9be913b3e6ec0697508da6a1afafec3f2d194e
permissions -rw-r--r--
Backed out 15 changesets (bug 1305957) for ASAN failures CLOSED TREE Backed out changeset 4d5eb85d3155 (bug 1305957) Backed out changeset 51c86d025ecb (bug 1305957) Backed out changeset d8eef8f3e396 (bug 1305957) Backed out changeset 950bf6ad1ef2 (bug 1305957) Backed out changeset b4cb2cbebdb6 (bug 1305957) Backed out changeset bfca5019a9cc (bug 1305957) Backed out changeset e76b842c7b7f (bug 1305957) Backed out changeset d9445a5f3458 (bug 1305957) Backed out changeset d9052f7b34d9 (bug 1305957) Backed out changeset e7124fecb721 (bug 1305957) Backed out changeset bdb766faa867 (bug 1305957) Backed out changeset 3033401ef320 (bug 1305957) Backed out changeset 6b96050386f6 (bug 1305957) Backed out changeset c66c00f73296 (bug 1305957) Backed out changeset 6bd0bdab93cb (bug 1305957)

/* 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::{GridLine as GenericGridLine, TrackBreadth as GenericTrackBreadth};
use super::generics::grid::{TrackList as GenericTrackList, TrackSize as GenericTrackSize};
use super::generics::transform::IsParallelTo;
use super::generics::{GreaterThanOrEqualToOne, NonNegative};
use super::specified;
use super::{CSSFloat, CSSInteger};
use crate::context::QuirksMode;
use crate::font_metrics::{get_metrics_provider_for_product, FontMetricsProvider};
use crate::media_queries::Device;
#[cfg(feature = "gecko")]
use crate::properties;
use crate::properties::{ComputedValues, LonghandId, StyleBuilder};
use crate::rule_cache::RuleCacheConditions;
use crate::Atom;
#[cfg(feature = "servo")]
use crate::Prefix;
use euclid::Size2D;
use std::cell::RefCell;
use std::cmp;
use std::f32;
use std::fmt::{self, Write};
use style_traits::cursor::CursorKind;
use style_traits::{CssWriter, ToCss};

#[cfg(feature = "gecko")]
pub use self::align::{AlignContent, AlignItems, JustifyContent, JustifyItems, 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, Contain};
pub use self::box_::{Appearance, BreakBetween, BreakWithin, Clear, Float};
pub use self::box_::{Display, Overflow, TransitionProperty};
pub use self::box_::{OverflowClipBox, OverscrollBehavior, Perspective, Resize};
pub use self::box_::{ScrollSnapType, TouchAction, VerticalAlign, WillChange};
pub use self::color::{Color, ColorPropertyValue, RGBAColor};
pub use self::column::ColumnCount;
pub use self::counters::{Content, ContentItem, CounterIncrement, CounterReset};
pub use self::easing::TimingFunction;
pub use self::effects::{BoxShadow, Filter, SimpleShadow};
pub use self::flex::FlexBasis;
pub use self::font::{FontFamily, FontLanguageOverride, FontStyle};
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::{MozScriptLevel, MozScriptMinSize, MozScriptSizeMultiplier, XLang, XTextZoom};
#[cfg(feature = "gecko")]
pub use self::gecko::ScrollSnapPoint;
pub use self::image::{Gradient, GradientItem, Image, ImageLayer, LineDirection, MozImageRect};
pub use self::length::{CSSPixelLength, ExtremumLength, NonNegativeLength};
pub use self::length::{Length, LengthOrNumber, LengthPercentage};
pub use self::length::{LengthPercentageOrAuto, LengthPercentageOrNone, MaxLength, MozLength};
pub use self::length::{NonNegativeLengthPercentage, NonNegativeLengthPercentageOrAuto};
#[cfg(feature = "gecko")]
pub use self::list::ListStyleType;
pub use self::list::{QuotePair, Quotes};
pub use self::motion::OffsetPath;
pub use self::outline::OutlineStyle;
pub use self::percentage::{NonNegativePercentage, Percentage};
pub use self::position::{GridAutoFlow, GridTemplateAreas, Position, ZIndex};
pub use self::rect::LengthOrNumberRect;
pub use self::resolution::Resolution;
pub use self::svg::MozContextProperties;
pub use self::svg::{SVGLength, SVGOpacity, SVGPaint, SVGPaintKind};
pub use self::svg::{SVGPaintOrder, SVGStrokeDashArray, SVGWidth};
pub use self::table::XSpan;
pub use self::text::{InitialLetter, LetterSpacing, LineHeight, MozTabSize};
pub use self::text::{OverflowWrap, TextOverflow, WordSpacing};
pub use self::text::{TextAlign, TextEmphasisPosition, TextEmphasisStyle};
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::{ColorOrAuto, Cursor, MozForceBrokenImageIcon, UserSelect};
pub use super::specified::{BorderStyle, TextDecorationLine};
pub use super::{Auto, Either, None_};
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;
#[cfg(feature = "gecko")]
pub mod gecko;
pub mod image;
pub mod length;
pub mod list;
pub mod motion;
pub mod outline;
pub mod percentage;
pub mod position;
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> {
    /// Whether the current element is the root element.
    pub is_root_element: bool,

    /// 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<()>,

    /// A font metrics provider, used to access font metrics to implement
    /// font-relative units.
    pub font_metrics_provider: &'a FontMetricsProvider,

    /// Whether or not we are computing the media list in a media query
    pub in_media_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,

    /// 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>,
}

impl<'a> Context<'a> {
    /// 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 provider = get_metrics_provider_for_product();

        let context = Context {
            is_root_element: false,
            builder: StyleBuilder::for_inheritance(device, None, None),
            font_metrics_provider: &provider,
            cached_system_font: None,
            in_media_query: true,
            quirks_mode,
            for_smil_animation: false,
            for_non_inherited_property: None,
            rule_cache_conditions: RefCell::new(&mut conditions),
        };

        f(&context)
    }

    /// Whether the current element is the root element.
    pub fn is_root_element(&self) -> bool {
        self.is_root_element
    }

    /// The current device.
    pub fn device(&self) -> &Device {
        self.builder.device
    }

    /// The current viewport size, used to resolve viewport units.
    pub fn viewport_size_for_viewport_unit_resolution(&self) -> Size2D<Au> {
        self.builder
            .device
            .au_viewport_size_for_viewport_unit_resolution()
    }

    /// 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: NonNegativeLength) -> NonNegativeLength {
        // We disable zoom for <svg:text> by unsetting the
        // -x-text-zoom property, which leads to a false value
        // in mAllowZoom
        if self.style().get_font().gecko.mAllowZoom {
            self.device().zoom_text(Au::from(size)).into()
        } else {
            size
        }
    }

    /// (Servo doesn't do text-zoom)
    #[cfg(feature = "servo")]
    pub fn maybe_zoom_text(&self, size: NonNegativeLength) -> NonNegativeLength {
        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: cx,
            values: 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`.
    #[inline]
    fn to_computed_value(&self, context: &Context) -> Self::ComputedValue;

    #[inline]
    /// 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 Size2D<T>
where
    T: ToComputedValue,
{
    type ComputedValue = 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()
    }
}

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!(Atom);
trivial_to_computed_value!(CursorKind);
#[cfg(feature = "servo")]
trivial_to_computed_value!(Prefix);
trivial_to_computed_value!(String);
trivial_to_computed_value!(Box<str>);

/// 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
    }
}

/// 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(Clone, ComputeSquaredDistance, Copy, Debug, MallocSizeOf, PartialEq, ToCss)]
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)
    }
}

#[allow(missing_docs)]
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
#[derive(Clone, ComputeSquaredDistance, Copy, Debug, PartialEq)]
/// A computed cliprect for clip and image-region
pub struct ClipRect {
    pub top: Option<Length>,
    pub right: Option<Length>,
    pub bottom: Option<Length>,
    pub left: Option<Length>,
}

impl ToCss for ClipRect {
    fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
    where
        W: Write,
    {
        dest.write_str("rect(")?;
        if let Some(top) = self.top {
            top.to_css(dest)?;
            dest.write_str(", ")?;
        } else {
            dest.write_str("auto, ")?;
        }

        if let Some(right) = self.right {
            right.to_css(dest)?;
            dest.write_str(", ")?;
        } else {
            dest.write_str("auto, ")?;
        }

        if let Some(bottom) = self.bottom {
            bottom.to_css(dest)?;
            dest.write_str(", ")?;
        } else {
            dest.write_str("auto, ")?;
        }

        if let Some(left) = self.left {
            left.to_css(dest)?;
        } else {
            dest.write_str("auto")?;
        }
        dest.write_str(")")
    }
}

/// rect(...) | auto
pub type ClipRectOrAuto = Either<ClipRect, Auto>;

/// 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-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 ClipRectOrAuto {
    /// Return an auto (default for clip-rect and image-region) value
    pub fn auto() -> Self {
        Either::Second(Auto)
    }

    /// Check if it is auto
    pub fn is_auto(&self) -> bool {
        match *self {
            Either::Second(_) => true,
            _ => false,
        }
    }
}