tor-browser

component.rs (7559B)

---

/* 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/. */

//! Parse/serialize and resolve a single color component.

use std::fmt::Write;

use super::{
   parsing::{rcs_enabled, ChannelKeyword},
   AbsoluteColor,
};
use crate::derives::*;
use crate::{
   parser::ParserContext,
   values::{
       animated::ToAnimatedValue,
       generics::calc::{CalcUnits, GenericCalcNode},
       specified::calc::{AllowParse, Leaf},
   },
};
use cssparser::{color::OPAQUE, Parser, Token};
use style_traits::{ParseError, ToCss};

/// A single color component.
#[derive(Clone, Debug, MallocSizeOf, PartialEq, ToShmem)]
#[repr(u8)]
pub enum ColorComponent<ValueType> {
   /// The "none" keyword.
   None,
   /// A absolute value.
   Value(ValueType),
   /// A channel keyword, e.g. `r`, `l`, `alpha`, etc.
   ChannelKeyword(ChannelKeyword),
   /// A calc() value.
   Calc(Box<GenericCalcNode<Leaf>>),
   /// Used when alpha components are not specified.
   AlphaOmitted,
}

impl<ValueType> ColorComponent<ValueType> {
   /// Return true if the component is "none".
   #[inline]
   pub fn is_none(&self) -> bool {
       matches!(self, Self::None)
   }
}

/// An utility trait that allows the construction of [ColorComponent]
/// `ValueType`'s after parsing a color component.
pub trait ColorComponentType: Sized + Clone {
   // TODO(tlouw): This function should be named according to the rules in the spec
   //              stating that all the values coming from color components are
   //              numbers and that each has their own rules dependeing on types.
   /// Construct a new component from a single value.
   fn from_value(value: f32) -> Self;

   /// Return the [CalcUnits] flags that the impl can handle.
   fn units() -> CalcUnits;

   /// Try to create a new component from the given token.
   fn try_from_token(token: &Token) -> Result<Self, ()>;

   /// Try to create a new component from the given [CalcNodeLeaf] that was
   /// resolved from a [CalcNode].
   fn try_from_leaf(leaf: &Leaf) -> Result<Self, ()>;
}

impl<ValueType: ColorComponentType> ColorComponent<ValueType> {
   /// Parse a single [ColorComponent].
   pub fn parse<'i, 't>(
       context: &ParserContext,
       input: &mut Parser<'i, 't>,
       allow_none: bool,
   ) -> Result<Self, ParseError<'i>> {
       let location = input.current_source_location();

       match *input.next()? {
           Token::Ident(ref value) if allow_none && value.eq_ignore_ascii_case("none") => {
               Ok(ColorComponent::None)
           },
           ref t @ Token::Ident(ref ident) => {
               let Ok(channel_keyword) = ChannelKeyword::from_ident(ident) else {
                   return Err(location.new_unexpected_token_error(t.clone()));
               };
               Ok(ColorComponent::ChannelKeyword(channel_keyword))
           },
           Token::Function(ref name) => {
               let function = GenericCalcNode::math_function(context, name, location)?;
               let allow = AllowParse::new(if rcs_enabled() {
                   ValueType::units() | CalcUnits::COLOR_COMPONENT
               } else {
                   ValueType::units()
               });
               let mut node = GenericCalcNode::parse(context, input, function, allow)?;

               // TODO(tlouw): We only have to simplify the node when we have to store it, but we
               //              only know if we have to store it much later when the whole color
               //              can't be resolved to absolute at which point the calc nodes are
               //              burried deep in a [ColorFunction] struct.
               node.simplify_and_sort();

               Ok(Self::Calc(Box::new(node)))
           },
           ref t => ValueType::try_from_token(t)
               .map(Self::Value)
               .map_err(|_| location.new_unexpected_token_error(t.clone())),
       }
   }

   /// Resolve a [ColorComponent] into a float.  None is "none".
   pub fn resolve(&self, origin_color: Option<&AbsoluteColor>) -> Result<Option<ValueType>, ()> {
       Ok(match self {
           ColorComponent::None => None,
           ColorComponent::Value(value) => Some(value.clone()),
           ColorComponent::ChannelKeyword(channel_keyword) => match origin_color {
               Some(origin_color) => {
                   let value = origin_color.get_component_by_channel_keyword(*channel_keyword)?;
                   Some(ValueType::from_value(value.unwrap_or(0.0)))
               },
               None => return Err(()),
           },
           ColorComponent::Calc(node) => {
               let Ok(resolved_leaf) = node.resolve_map(|leaf| {
                   Ok(match leaf {
                       Leaf::ColorComponent(channel_keyword) => match origin_color {
                           Some(origin_color) => {
                               let value = origin_color
                                   .get_component_by_channel_keyword(*channel_keyword)?;
                               Leaf::Number(value.unwrap_or(0.0))
                           },
                           None => return Err(()),
                       },
                       l => l.clone(),
                   })
               }) else {
                   return Err(());
               };

               Some(ValueType::try_from_leaf(&resolved_leaf)?)
           },
           ColorComponent::AlphaOmitted => {
               if let Some(origin_color) = origin_color {
                   // <https://drafts.csswg.org/css-color-5/#rcs-intro>
                   // If the alpha value of the relative color is omitted, it defaults to that of
                   // the origin color (rather than defaulting to 100%, as it does in the absolute
                   // syntax).
                   origin_color.alpha().map(ValueType::from_value)
               } else {
                   Some(ValueType::from_value(OPAQUE))
               }
           },
       })
   }
}

impl<ValueType: ToCss> ToCss for ColorComponent<ValueType> {
   fn to_css<W>(&self, dest: &mut style_traits::CssWriter<W>) -> std::fmt::Result
   where
       W: Write,
   {
       match self {
           ColorComponent::None => dest.write_str("none")?,
           ColorComponent::Value(value) => value.to_css(dest)?,
           ColorComponent::ChannelKeyword(channel_keyword) => channel_keyword.to_css(dest)?,
           ColorComponent::Calc(node) => {
               // When we only have a channel keyword in a leaf node, we should serialize it with
               // calc(..), except when one of the rgb color space functions are used, e.g.
               // rgb(..), hsl(..) or hwb(..) for historical reasons.
               // <https://github.com/web-platform-tests/wpt/issues/47921>
               node.to_css(dest)?;
           },
           ColorComponent::AlphaOmitted => {
               debug_assert!(false, "can't serialize an omitted alpha component");
           },
       }

       Ok(())
   }
}

impl<ValueType> ToAnimatedValue for ColorComponent<ValueType> {
   type AnimatedValue = Self;

   fn to_animated_value(self, _context: &crate::values::animated::Context) -> Self::AnimatedValue {
       self
   }

   fn from_animated_value(animated: Self::AnimatedValue) -> Self {
       animated
   }
}