firefox-main/servo/components/style/values/computed/color.rs (file symbol)

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/* 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::color::AbsoluteColor;
use crate::values::animated::ToAnimatedZero;
use crate::values::computed::percentage::Percentage;
use crate::values::generics::color::{
GenericCaretColor, GenericColor, GenericColorMix, GenericColorOrAuto,
};
use std::fmt::{self, Write};
use style_traits::{CssWriter, ToCss};
pub use crate::values::specified::color::{ColorScheme, ForcedColorAdjust, PrintColorAdjust};
/// The computed value of the `color` property.
pub type ColorPropertyValue = AbsoluteColor;
/// A computed value for `<color>`.
pub type Color = GenericColor<Percentage>;
/// A computed color-mix().
pub type ColorMix = GenericColorMix<Color, Percentage>;
impl ToCss for Color {
fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
where
W: fmt::Write,
{
match *self {
Self::Absolute(ref c) => c.to_css(dest),
Self::ColorFunction(ref color_function) => color_function.to_css(dest),
Self::CurrentColor => dest.write_str("currentcolor"),
Self::ColorMix(ref m) => m.to_css(dest),
Self::ContrastColor(ref c) => {
dest.write_str("contrast-color(")?;
c.to_css(dest)?;
dest.write_char(')')
},
}
}
}
impl Color {
/// A fully transparent color.
pub const TRANSPARENT_BLACK: Self = Self::Absolute(AbsoluteColor::TRANSPARENT_BLACK);
/// An opaque black color.
pub const BLACK: Self = Self::Absolute(AbsoluteColor::BLACK);
/// An opaque white color.
pub const WHITE: Self = Self::Absolute(AbsoluteColor::WHITE);
/// Create a new computed [`Color`] from a given color-mix, simplifying it to an absolute color
/// if possible.
pub fn from_color_mix(color_mix: ColorMix) -> Self {
if let Some(absolute) = color_mix.mix_to_absolute() {
Self::Absolute(absolute)
} else {
Self::ColorMix(Box::new(color_mix))
}
}
/// Combine this complex color with the given foreground color into an
/// absolute color.
pub fn resolve_to_absolute(&self, current_color: &AbsoluteColor) -> AbsoluteColor {
use crate::values::specified::percentage::ToPercentage;
match *self {
Self::Absolute(c) => c,
Self::ColorFunction(ref color_function) => {
color_function.resolve_to_absolute(current_color)
},
Self::CurrentColor => *current_color,
Self::ColorMix(ref mix) => {
use crate::color::mix;
mix::mix_many(
mix.interpolation,
mix.items.iter().map(|item| {
mix::ColorMixItem::new(
item.color.resolve_to_absolute(current_color),
item.percentage.to_percentage(),
)
}),
mix.flags,
)
},
Self::ContrastColor(ref c) => {
let bg_color = c.resolve_to_absolute(current_color);
if Self::contrast_ratio(&bg_color, &AbsoluteColor::BLACK)
> Self::contrast_ratio(&bg_color, &AbsoluteColor::WHITE)
{
AbsoluteColor::BLACK
} else {
AbsoluteColor::WHITE
}
},
}
}
fn contrast_ratio(a: &AbsoluteColor, b: &AbsoluteColor) -> f32 {
// TODO: This just implements the WCAG 2.1 algorithm,
// Consider using a more sophisticated contrast algorithm, e.g. see
let compute = |c| -> f32 {
if c <= 0.04045 {
c / 12.92
} else {
f32::powf((c + 0.055) / 1.055, 2.4)
}
};
let luminance = |r, g, b| -> f32 { 0.2126 * r + 0.7152 * g + 0.0722 * b };
let a = a.into_srgb_legacy();
let b = b.into_srgb_legacy();
let a = a.raw_components();
let b = b.raw_components();
let la = luminance(compute(a[0]), compute(a[1]), compute(a[2])) + 0.05;
let lb = luminance(compute(b[0]), compute(b[1]), compute(b[2])) + 0.05;
if la > lb {
la / lb
} else {
lb / la
}
}
}
impl ToAnimatedZero for AbsoluteColor {
fn to_animated_zero(&self) -> Result<Self, ()> {
Ok(Self::TRANSPARENT_BLACK)
}
}
/// auto | <color>
pub type ColorOrAuto = GenericColorOrAuto<Color>;
/// caret-color
pub type CaretColor = GenericCaretColor<Color>;