tor-browser

media_rule.rs (7137B)

---

/* 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/. */

//! An [`@media`][media] rule.
//!
//! [media]: https://drafts.csswg.org/css-conditional/#at-ruledef-media

use crate::derives::*;
use crate::media_queries::MediaList;
use crate::selector_map::{PrecomputedHashMap, PrecomputedHashSet};
use crate::shared_lock::{DeepCloneWithLock, Locked};
use crate::shared_lock::{SharedRwLock, SharedRwLockReadGuard, ToCssWithGuard};
use crate::stylesheets::CssRules;
use crate::values::{computed, DashedIdent};
use crate::Atom;
use cssparser::Parser;
use cssparser::SourceLocation;
#[cfg(feature = "gecko")]
use malloc_size_of::{MallocSizeOfOps, MallocUnconditionalShallowSizeOf};
use selectors::kleene_value::KleeneValue;
use servo_arc::Arc;
use std::fmt::{self, Write};
use style_traits::{CssStringWriter, CssWriter, ParseError, ToCss};

/// An [`@media`][media] rule.
///
/// [media]: https://drafts.csswg.org/css-conditional/#at-ruledef-media
#[derive(Debug, ToShmem)]
pub struct MediaRule {
   /// The list of media queries used by this media rule.
   pub media_queries: Arc<Locked<MediaList>>,
   /// The nested rules to this media rule.
   pub rules: Arc<Locked<CssRules>>,
   /// The source position where this media rule was found.
   pub source_location: SourceLocation,
}

impl MediaRule {
   /// Measure heap usage.
   #[cfg(feature = "gecko")]
   pub fn size_of(&self, guard: &SharedRwLockReadGuard, ops: &mut MallocSizeOfOps) -> usize {
       // Measurement of other fields may be added later.
       self.rules.unconditional_shallow_size_of(ops)
           + self.rules.read_with(guard).size_of(guard, ops)
   }
}

impl ToCssWithGuard for MediaRule {
   // Serialization of MediaRule is not specced.
   // https://drafts.csswg.org/cssom/#serialize-a-css-rule CSSMediaRule
   fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
       dest.write_str("@media ")?;
       self.media_queries
           .read_with(guard)
           .to_css(&mut CssWriter::new(dest))?;
       self.rules.read_with(guard).to_css_block(guard, dest)
   }
}

impl DeepCloneWithLock for MediaRule {
   fn deep_clone_with_lock(&self, lock: &SharedRwLock, guard: &SharedRwLockReadGuard) -> Self {
       let media_queries = self.media_queries.read_with(guard);
       let rules = self.rules.read_with(guard);
       MediaRule {
           media_queries: Arc::new(lock.wrap(media_queries.clone())),
           rules: Arc::new(lock.wrap(rules.deep_clone_with_lock(lock, guard))),
           source_location: self.source_location.clone(),
       }
   }
}

/// The condition associated to a custom-media query.
#[derive(Debug, ToShmem, Clone, MallocSizeOf)]
pub enum CustomMediaCondition {
   /// Unconditionally true.
   True,
   /// Unconditionally false.
   False,
   /// A MediaList.
   MediaList(#[ignore_malloc_size_of = "Arc"] Arc<Locked<MediaList>>),
}

impl CustomMediaCondition {
   /// Parses the possible keywords for this condition.
   pub(crate) fn parse_keyword<'i>(input: &mut Parser<'i, '_>) -> Result<Self, ParseError<'i>> {
       Ok(try_match_ident_ignore_ascii_case! { input,
           "true" => Self::True,
           "false" => Self::False,
       })
   }
}

impl DeepCloneWithLock for CustomMediaCondition {
   fn deep_clone_with_lock(&self, lock: &SharedRwLock, guard: &SharedRwLockReadGuard) -> Self {
       match self {
           Self::True => Self::True,
           Self::False => Self::False,
           Self::MediaList(ref m) => {
               Self::MediaList(Arc::new(lock.wrap(m.read_with(guard).clone())))
           },
       }
   }
}

/// A `@custom-media` rule.
/// https://drafts.csswg.org/mediaqueries-5/#custom-mq
#[derive(Debug, ToShmem)]
pub struct CustomMediaRule {
   /// The name of the custom media rule.
   pub name: DashedIdent,
   /// The list of media conditions used by this media rule.
   pub condition: CustomMediaCondition,
   /// The source position where this media rule was found.
   pub source_location: SourceLocation,
}

impl DeepCloneWithLock for CustomMediaRule {
   fn deep_clone_with_lock(&self, lock: &SharedRwLock, guard: &SharedRwLockReadGuard) -> Self {
       Self {
           name: self.name.clone(),
           condition: self.condition.deep_clone_with_lock(lock, guard),
           source_location: self.source_location.clone(),
       }
   }
}

impl ToCssWithGuard for CustomMediaRule {
   // Serialization of MediaRule is not specced.
   // https://drafts.csswg.org/cssom/#serialize-a-css-rule CSSMediaRule
   fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
       dest.write_str("@custom-media ")?;
       self.name.to_css(&mut CssWriter::new(dest))?;
       dest.write_char(' ')?;
       match self.condition {
           CustomMediaCondition::True => dest.write_str("true"),
           CustomMediaCondition::False => dest.write_str("false"),
           CustomMediaCondition::MediaList(ref m) => {
               m.read_with(guard).to_css(&mut CssWriter::new(dest))
           },
       }
   }
}

/// The currently effective @custom-media conditions.
pub type CustomMediaMap = PrecomputedHashMap<Atom, CustomMediaCondition>;

/// A struct that can evaluate custom media conditions.
pub struct CustomMediaEvaluator<'a> {
   map: Option<(&'a CustomMediaMap, &'a SharedRwLockReadGuard<'a>)>,
   /// Set of media queries we're currently evaluating, needed for cycle detection.
   currently_evaluating: PrecomputedHashSet<Atom>,
}

impl<'a> CustomMediaEvaluator<'a> {
   /// Construct a new custom media evaluator with the given map and guard.
   pub fn new(map: &'a CustomMediaMap, guard: &'a SharedRwLockReadGuard<'a>) -> Self {
       Self {
           map: Some((map, guard)),
           currently_evaluating: Default::default(),
       }
   }

   /// Returns an evaluator that can't evaluate custom queries.
   pub fn none() -> Self {
       Self {
           map: None,
           currently_evaluating: Default::default(),
       }
   }

   /// Evaluates a custom media query.
   pub fn matches(&mut self, ident: &DashedIdent, context: &computed::Context) -> KleeneValue {
       let Some((map, guard)) = self.map else {
           return KleeneValue::Unknown;
       };
       let Some(condition) = map.get(&ident.0) else {
           return KleeneValue::Unknown;
       };
       let media = match condition {
           CustomMediaCondition::True => return KleeneValue::True,
           CustomMediaCondition::False => return KleeneValue::False,
           CustomMediaCondition::MediaList(ref m) => m,
       };
       if !self.currently_evaluating.insert(ident.0.clone()) {
           // Found a cycle while evaluating this rule.
           return KleeneValue::False;
       }
       let result = media.read_with(guard).matches(context, self);
       self.currently_evaluating.remove(&ident.0);
       result.into()
   }
}