servo/components/style/values/generics/image.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/. */

//! Generic types for the handling of [images].
//!
//! [images]: https://drafts.csswg.org/css-images/#image-values

use Atom;
use cssparser::serialize_identifier;
use custom_properties::SpecifiedValue;
use std::fmt;
use style_traits::{HasViewportPercentage, ToCss};
use values::computed::ComputedValueAsSpecified;

/// An [image].
///
/// [image]: https://drafts.csswg.org/css-images/#image-values
#[derive(Clone, PartialEq, ToComputedValue)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub enum Image<Gradient, MozImageRect, ImageUrl> {
    /// A `<url()>` image.
    Url(ImageUrl),
    /// A `<gradient>` image.
    Gradient(Gradient),
    /// A `-moz-image-rect` image
    Rect(MozImageRect),
    /// A `-moz-element(# <element-id>)`
    Element(Atom),
    /// A paint worklet image.
    /// https://drafts.css-houdini.org/css-paint-api/
    #[cfg(feature = "servo")]
    PaintWorklet(PaintWorklet),
}

/// A CSS gradient.
/// https://drafts.csswg.org/css-images/#gradients
#[derive(Clone, Debug, HasViewportPercentage, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub struct Gradient<LineDirection, Length, LengthOrPercentage, Position, Color, Angle> {
    /// Gradients can be linear or radial.
    pub kind: GradientKind<LineDirection, Length, LengthOrPercentage, Position, Angle>,
    /// The color stops and interpolation hints.
    pub items: Vec<GradientItem<Color, LengthOrPercentage>>,
    /// True if this is a repeating gradient.
    pub repeating: bool,
    /// Compatibility mode.
    pub compat_mode: CompatMode,
}

#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
/// Whether we used the modern notation or the compatibility `-webkit`, `-moz` prefixes.
pub enum CompatMode {
    /// Modern syntax.
    Modern,
    /// `-webkit` prefix.
    WebKit,
    /// `-moz` prefix
    Moz,
}

/// A gradient kind.
#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub enum GradientKind<LineDirection, Length, LengthOrPercentage, Position, Angle> {
    /// A linear gradient.
    Linear(LineDirection),
    /// A radial gradient.
    Radial(EndingShape<Length, LengthOrPercentage>, Position, Option<Angle>),
}

/// A radial gradient's ending shape.
#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue, ToCss)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub enum EndingShape<Length, LengthOrPercentage> {
    /// A circular gradient.
    Circle(Circle<Length>),
    /// An elliptic gradient.
    Ellipse(Ellipse<LengthOrPercentage>),
}

/// A circle shape.
#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub enum Circle<Length> {
    /// A circle radius.
    Radius(Length),
    /// A circle extent.
    Extent(ShapeExtent),
}

/// An ellipse shape.
#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue, ToCss)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub enum Ellipse<LengthOrPercentage> {
    /// An ellipse pair of radii.
    Radii(LengthOrPercentage, LengthOrPercentage),
    /// An ellipse extent.
    Extent(ShapeExtent),
}

/// https://drafts.csswg.org/css-images/#typedef-extent-keyword
define_css_keyword_enum!(ShapeExtent:
    "closest-side" => ClosestSide,
    "farthest-side" => FarthestSide,
    "closest-corner" => ClosestCorner,
    "farthest-corner" => FarthestCorner,
    "contain" => Contain,
    "cover" => Cover
);
no_viewport_percentage!(ShapeExtent);
impl ComputedValueAsSpecified for ShapeExtent {}

/// A gradient item.
/// https://drafts.csswg.org/css-images-4/#color-stop-syntax
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[derive(Clone, Copy, Debug, HasViewportPercentage, PartialEq, ToComputedValue, ToCss)]
pub enum GradientItem<Color, LengthOrPercentage> {
    /// A color stop.
    ColorStop(ColorStop<Color, LengthOrPercentage>),
    /// An interpolation hint.
    InterpolationHint(LengthOrPercentage),
}

/// A color stop.
/// https://drafts.csswg.org/css-images/#typedef-color-stop-list
#[derive(Clone, Copy, HasViewportPercentage, PartialEq, ToComputedValue, ToCss)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
pub struct ColorStop<Color, LengthOrPercentage> {
    /// The color of this stop.
    pub color: Color,
    /// The position of this stop.
    pub position: Option<LengthOrPercentage>,
}

/// Specified values for a paint worklet.
/// https://drafts.css-houdini.org/css-paint-api/
#[derive(Clone, Debug, PartialEq)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
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.
    pub arguments: Vec<SpecifiedValue>,
}

impl ComputedValueAsSpecified for PaintWorklet {}

impl ToCss for PaintWorklet {
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        dest.write_str("paint(")?;
        serialize_identifier(&*self.name.to_string(), 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)]
#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
#[css(comma, function)]
#[derive(Clone, Debug, PartialEq, ToComputedValue, ToCss)]
pub struct MozImageRect<NumberOrPercentage, MozImageRectUrl> {
    pub url: MozImageRectUrl,
    pub top: NumberOrPercentage,
    pub right: NumberOrPercentage,
    pub bottom: NumberOrPercentage,
    pub left: NumberOrPercentage,
}

impl<G, R, U> fmt::Debug for Image<G, R, U>
    where G: fmt::Debug, R: fmt::Debug, U: fmt::Debug + ToCss
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Image::Url(ref url) => url.to_css(f),
            Image::Gradient(ref grad) => grad.fmt(f),
            Image::Rect(ref rect) => rect.fmt(f),
            #[cfg(feature = "servo")]
            Image::PaintWorklet(ref paint_worklet) => paint_worklet.fmt(f),
            Image::Element(ref selector) => {
                f.write_str("-moz-element(#")?;
                serialize_identifier(&selector.to_string(), f)?;
                f.write_str(")")
            },
        }
    }
}

impl<G, R, U> ToCss for Image<G, R, U>
    where G: ToCss, R: ToCss, U: ToCss
{
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match *self {
            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")]
            Image::PaintWorklet(ref paint_worklet) => paint_worklet.to_css(dest),
            Image::Element(ref selector) => {
                dest.write_str("-moz-element(#")?;
                serialize_identifier(&selector.to_string(), dest)?;
                dest.write_str(")")
            },
        }
    }
}

impl<G, R, U> HasViewportPercentage for Image<G, R, U>
    where G: HasViewportPercentage
{
    fn has_viewport_percentage(&self) -> bool {
        match *self {
            Image::Gradient(ref gradient) => gradient.has_viewport_percentage(),
            _ => false,
        }
    }
}

impl<D, L, LoP, P, C, A> ToCss for Gradient<D, L, LoP, P, C, A>
    where D: LineDirection, L: ToCss, LoP: ToCss, P: ToCss, C: ToCss, A: ToCss
{
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result where W: fmt::Write {
        match self.compat_mode {
            CompatMode::WebKit => dest.write_str("-webkit-")?,
            CompatMode::Moz => dest.write_str("-moz-")?,
            _ => {},
        }

        if self.repeating {
            dest.write_str("repeating-")?;
        }
        dest.write_str(self.kind.label())?;
        dest.write_str("-gradient(")?;
        let mut skip_comma = match self.kind {
            GradientKind::Linear(ref direction) if direction.points_downwards() => true,
            GradientKind::Linear(ref direction) => {
                direction.to_css(dest, self.compat_mode)?;
                false
            },
            GradientKind::Radial(ref shape, ref position, ref angle) => {
                let omit_shape = match *shape {
                    EndingShape::Ellipse(Ellipse::Extent(ShapeExtent::Cover)) |
                    EndingShape::Ellipse(Ellipse::Extent(ShapeExtent::FarthestCorner)) => {
                        true
                    },
                    _ => false,
                };
                if self.compat_mode == CompatMode::Modern {
                    if !omit_shape {
                        shape.to_css(dest)?;
                        dest.write_str(" ")?;
                    }
                    dest.write_str("at ")?;
                    position.to_css(dest)?;
                } else {
                    position.to_css(dest)?;
                    if let Some(ref a) = *angle {
                        dest.write_str(" ")?;
                        a.to_css(dest)?;
                    }
                    if !omit_shape {
                        dest.write_str(", ")?;
                        shape.to_css(dest)?;
                    }
                }
                false
            },
        };
        for item in &self.items {
            if !skip_comma {
                dest.write_str(", ")?;
            }
            skip_comma = false;
            item.to_css(dest)?;
        }
        dest.write_str(")")
    }
}

impl<D, L, LoP, P, A> GradientKind<D, L, LoP, P, A> {
    fn label(&self) -> &str {
        match *self {
            GradientKind::Linear(..) => "linear",
            GradientKind::Radial(..) => "radial",
        }
    }
}

/// The direction of a linear gradient.
pub trait LineDirection {
    /// Whether this direction points towards, and thus can be omitted.
    fn points_downwards(&self) -> bool;

    /// Serialises this direction according to the compatibility mode.
    fn to_css<W>(&self, dest: &mut W, compat_mode: CompatMode) -> fmt::Result
        where W: fmt::Write;
}

impl<L> ToCss for Circle<L>
where
    L: ToCss,
{
    fn to_css<W>(&self, dest: &mut W) -> fmt::Result
    where
        W: fmt::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)
            },
        }
    }
}

impl<C, L> fmt::Debug for ColorStop<C, L>
    where C: fmt::Debug, L: fmt::Debug,
{
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "{:?}", self.color)?;
        if let Some(ref pos) = self.position {
            write!(f, " {:?}", pos)?;
        }
        Ok(())
    }
}