Quelle  stylist.rs   Sprache: unbekannt

/* 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/. */

//! Selector matching.

use crate::applicable_declarations::{
    ApplicableDeclarationBlock, ApplicableDeclarationList, CascadePriority, ScopeProximity,
};
use crate::computed_value_flags::ComputedValueFlags;
use crate::context::{CascadeInputs, QuirksMode};
use crate::custom_properties::ComputedCustomProperties;
use crate::dom::TElement;
#[cfg(feature = "gecko")]
use crate::gecko_bindings::structs::{ServoStyleSetSizes, StyleRuleInclusion};
use crate::invalidation::element::invalidation_map::{
    note_selector_for_invalidation, InvalidationMap, RelativeSelectorInvalidationMap,
};
use crate::invalidation::media_queries::{
    EffectiveMediaQueryResults, MediaListKey, ToMediaListKey,
};
use crate::invalidation::stylesheets::RuleChangeKind;
use crate::media_queries::Device;
use crate::properties::{self, CascadeMode, ComputedValues, FirstLineReparenting};
use crate::properties::{AnimationDeclarations, PropertyDeclarationBlock};
use crate::properties_and_values::registry::{
    PropertyRegistration, PropertyRegistrationData, ScriptRegistry as CustomPropertyScriptRegistry,
};
use crate::rule_cache::{RuleCache, RuleCacheConditions};
use crate::rule_collector::RuleCollector;
use crate::rule_tree::{CascadeLevel, RuleTree, StrongRuleNode, StyleSource};
use crate::selector_map::{PrecomputedHashMap, PrecomputedHashSet, SelectorMap, SelectorMapEntry};
use crate::selector_parser::{
    NonTSPseudoClass, PerPseudoElementMap, PseudoElement, SelectorImpl, SnapshotMap,
};
use crate::shared_lock::{Locked, SharedRwLockReadGuard, StylesheetGuards};
use crate::sharing::{RevalidationResult, ScopeRevalidationResult};
use crate::stylesheet_set::{DataValidity, DocumentStylesheetSet, SheetRebuildKind};
use crate::stylesheet_set::{DocumentStylesheetFlusher, SheetCollectionFlusher};
use crate::stylesheets::container_rule::ContainerCondition;
use crate::stylesheets::import_rule::ImportLayer;
use crate::stylesheets::keyframes_rule::KeyframesAnimation;
use crate::stylesheets::layer_rule::{LayerName, LayerOrder};
use crate::stylesheets::scope_rule::{
    collect_scope_roots, element_is_outside_of_scope, scope_selector_list_is_trivial, ImplicitScopeRoot, ScopeRootCandidate, ScopeSubjectMap, ScopeTarget
};
#[cfg(feature = "gecko")]
use crate::stylesheets::{
    CounterStyleRule, FontFaceRule, FontFeatureValuesRule, FontPaletteValuesRule,
};
use crate::stylesheets::{
    CssRule, EffectiveRulesIterator, Origin, OriginSet, PagePseudoClassFlags, PageRule, PerOrigin,
    PerOriginIter, StylesheetContents, StylesheetInDocument,
};
use crate::values::{computed, AtomIdent};
use crate::AllocErr;
use crate::{Atom, LocalName, Namespace, ShrinkIfNeeded, WeakAtom};
use dom::{DocumentState, ElementState};
use fxhash::FxHashMap;
use malloc_size_of::MallocSizeOf;
#[cfg(feature = "gecko")]
use malloc_size_of::{MallocShallowSizeOf, MallocSizeOfOps, MallocUnconditionalShallowSizeOf};
use selectors::attr::{CaseSensitivity, NamespaceConstraint};
use selectors::bloom::BloomFilter;
use selectors::matching::{
    matches_selector, selector_may_match, MatchingContext, MatchingMode, NeedsSelectorFlags, SelectorCaches
};
use selectors::matching::{MatchingForInvalidation, VisitedHandlingMode};
use selectors::parser::{
    AncestorHashes, Combinator, Component, FeaturelessHostMatches, Selector, SelectorIter,
    SelectorList,
};
use selectors::visitor::{SelectorListKind, SelectorVisitor};
use servo_arc::{Arc, ArcBorrow};
use smallvec::SmallVec;
use std::cmp::Ordering;
use std::hash::{Hash, Hasher};
use std::sync::Mutex;
use std::{mem, ops};

/// The type of the stylesheets that the stylist contains.
#[cfg(feature = "servo")]
pub type StylistSheet = crate::stylesheets::DocumentStyleSheet;

/// The type of the stylesheets that the stylist contains.
#[cfg(feature = "gecko")]
pub type StylistSheet = crate::gecko::data::GeckoStyleSheet;

#[derive(Debug, Clone)]
struct StylesheetContentsPtr(Arc<StylesheetContents>);

impl PartialEq for StylesheetContentsPtr {
    #[inline]
    fn eq(&self, other: &Self) -> bool {
        Arc::ptr_eq(&self.0, &other.0)
    }
}

impl Eq for StylesheetContentsPtr {}

impl Hash for StylesheetContentsPtr {
    fn hash<H: Hasher>(&self, state: &mut H) {
        let contents: &StylesheetContents = &*self.0;
        (contents as *const StylesheetContents).hash(state)
    }
}

type StyleSheetContentList = Vec<StylesheetContentsPtr>;

/// A key in the cascade data cache.
#[derive(Debug, Hash, Default, PartialEq, Eq)]
struct CascadeDataCacheKey {
    media_query_results: Vec<MediaListKey>,
    contents: StyleSheetContentList,
}

unsafe impl Send for CascadeDataCacheKey {}
unsafe impl Sync for CascadeDataCacheKey {}

trait CascadeDataCacheEntry: Sized {
    /// Rebuilds the cascade data for the new stylesheet collection. The
    /// collection is guaranteed to be dirty.
    fn rebuild<S>(
        device: &Device,
        quirks_mode: QuirksMode,
        collection: SheetCollectionFlusher<S>,
        guard: &SharedRwLockReadGuard,
        old_entry: &Self,
    ) -> Result<Arc<Self>, AllocErr>
    where
        S: StylesheetInDocument + PartialEq + 'static;
    /// Measures heap memory usage.
    #[cfg(feature = "gecko")]
    fn add_size_of(&self, ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes);
}

struct CascadeDataCache<Entry> {
    entries: FxHashMap<CascadeDataCacheKey, Arc<Entry>>,
}

impl<Entry> CascadeDataCache<Entry>
where
    Entry: CascadeDataCacheEntry,
{
    fn new() -> Self {
        Self {
            entries: Default::default(),
        }
    }

    fn len(&self) -> usize {
        self.entries.len()
    }

    // FIXME(emilio): This may need to be keyed on quirks-mode too, though for
    // UA sheets there aren't class / id selectors on those sheets, usually, so
    // it's probably ok... For the other cache the quirks mode shouldn't differ
    // so also should be fine.
    fn lookup<'a, S>(
        &'a mut self,
        device: &Device,
        quirks_mode: QuirksMode,
        collection: SheetCollectionFlusher<S>,
        guard: &SharedRwLockReadGuard,
        old_entry: &Entry,
    ) -> Result<Option<Arc<Entry>>, AllocErr>
    where
        S: StylesheetInDocument + PartialEq + 'static,
    {
        use std::collections::hash_map::Entry as HashMapEntry;
        debug!("StyleSheetCache::lookup({})", self.len());

        if !collection.dirty() {
            return Ok(None);
        }

        let mut key = CascadeDataCacheKey::default();
        for sheet in collection.sheets() {
            CascadeData::collect_applicable_media_query_results_into(
                device,
                sheet,
                guard,
                &mut key.media_query_results,
                &mut key.contents,
            )
        }

        let new_entry;
        match self.entries.entry(key) {
            HashMapEntry::Vacant(e) => {
                debug!("> Picking the slow path (not in the cache)");
                new_entry = Entry::rebuild(
                    device,
                    quirks_mode,
                    collection,
                    guard,
                    old_entry,
                )?;
                e.insert(new_entry.clone());
            },
            HashMapEntry::Occupied(mut e) => {
                // Avoid reusing our old entry (this can happen if we get
                // invalidated due to CSSOM mutations and our old stylesheet
                // contents were already unique, for example).
                if !std::ptr::eq(&**e.get(), old_entry) {
                    if log_enabled!(log::Level::Debug) {
                        debug!("cache hit for:");
                        for sheet in collection.sheets() {
                            debug!(" > {:?}", sheet);
                        }
                    }
                    // The line below ensures the "committed" bit is updated
                    // properly.
                    collection.each(|_, _, _| true);
                    return Ok(Some(e.get().clone()));
                }

                debug!("> Picking the slow path due to same entry as old");
                new_entry = Entry::rebuild(
                    device,
                    quirks_mode,
                    collection,
                    guard,
                    old_entry,
                )?;
                e.insert(new_entry.clone());
            },
        }

        Ok(Some(new_entry))
    }

    /// Returns all the cascade datas that are not being used (that is, that are
    /// held alive just by this cache).
    ///
    /// We return them instead of dropping in place because some of them may
    /// keep alive some other documents (like the SVG documents kept alive by
    /// URL references), and thus we don't want to drop them while locking the
    /// cache to not deadlock.
    fn take_unused(&mut self) -> SmallVec<[Arc<Entry>; 3]> {
        let mut unused = SmallVec::new();
        self.entries.retain(|_key, value| {
            // is_unique() returns false for static references, but we never
            // have static references to UserAgentCascadeDatas.  If we did, it
            // may not make sense to put them in the cache in the first place.
            if !value.is_unique() {
                return true;
            }
            unused.push(value.clone());
            false
        });
        unused
    }

    fn take_all(&mut self) -> FxHashMap<CascadeDataCacheKey, Arc<Entry>> {
        mem::take(&mut self.entries)
    }

    #[cfg(feature = "gecko")]
    fn add_size_of(&self, ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes) {
        sizes.mOther += self.entries.shallow_size_of(ops);
        for (_key, arc) in self.entries.iter() {
            // These are primary Arc references that can be measured
            // unconditionally.
            sizes.mOther += arc.unconditional_shallow_size_of(ops);
            arc.add_size_of(ops, sizes);
        }
    }
}

/// Measure heap usage of UA_CASCADE_DATA_CACHE.
#[cfg(feature = "gecko")]
pub fn add_size_of_ua_cache(ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes) {
    UA_CASCADE_DATA_CACHE
        .lock()
        .unwrap()
        .add_size_of(ops, sizes);
}

lazy_static! {
    /// A cache of computed user-agent data, to be shared across documents.
    static ref UA_CASCADE_DATA_CACHE: Mutex<UserAgentCascadeDataCache> =
        Mutex::new(UserAgentCascadeDataCache::new());
}

impl CascadeDataCacheEntry for UserAgentCascadeData {
    fn rebuild<S>(
        device: &Device,
        quirks_mode: QuirksMode,
        collection: SheetCollectionFlusher<S>,
        guard: &SharedRwLockReadGuard,
        _old: &Self,
    ) -> Result<Arc<Self>, AllocErr>
    where
        S: StylesheetInDocument + PartialEq + 'static,
    {
        // TODO: Maybe we should support incremental rebuilds, though they seem
        // uncommon and rebuild() doesn't deal with
        // precomputed_pseudo_element_decls for now so...
        let mut new_data = Self {
            cascade_data: CascadeData::new(),
            precomputed_pseudo_element_decls: PrecomputedPseudoElementDeclarations::default(),
        };

        for (index, sheet) in collection.sheets().enumerate() {
            new_data.cascade_data.add_stylesheet(
                device,
                quirks_mode,
                sheet,
                index,
                guard,
                SheetRebuildKind::Full,
                Some(&mut new_data.precomputed_pseudo_element_decls),
            )?;
        }

        new_data.cascade_data.did_finish_rebuild();

        Ok(Arc::new(new_data))
    }

    #[cfg(feature = "gecko")]
    fn add_size_of(&self, ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes) {
        self.cascade_data.add_size_of(ops, sizes);
        sizes.mPrecomputedPseudos += self.precomputed_pseudo_element_decls.size_of(ops);
    }
}

type UserAgentCascadeDataCache = CascadeDataCache<UserAgentCascadeData>;

type PrecomputedPseudoElementDeclarations = PerPseudoElementMap<Vec<ApplicableDeclarationBlock>>;

#[derive(Default)]
struct UserAgentCascadeData {
    cascade_data: CascadeData,

    /// Applicable declarations for a given non-eagerly cascaded pseudo-element.
    ///
    /// These are eagerly computed once, and then used to resolve the new
    /// computed values on the fly on layout.
    ///
    /// These are only filled from UA stylesheets.
    precomputed_pseudo_element_decls: PrecomputedPseudoElementDeclarations,
}

lazy_static! {
    /// The empty UA cascade data for un-filled stylists.
    static ref EMPTY_UA_CASCADE_DATA: Arc<UserAgentCascadeData> = {
        let arc = Arc::new(UserAgentCascadeData::default());
        arc.mark_as_intentionally_leaked();
        arc
    };
}

/// All the computed information for all the stylesheets that apply to the
/// document.
#[derive(MallocSizeOf)]
pub struct DocumentCascadeData {
    #[ignore_malloc_size_of = "Arc, owned by UserAgentCascadeDataCache or empty"]
    user_agent: Arc<UserAgentCascadeData>,
    user: CascadeData,
    author: CascadeData,
    per_origin: PerOrigin<()>,
}

impl Default for DocumentCascadeData {
    fn default() -> Self {
        Self {
            user_agent: EMPTY_UA_CASCADE_DATA.clone(),
            user: Default::default(),
            author: Default::default(),
            per_origin: Default::default(),
        }
    }
}

/// An iterator over the cascade data of a given document.
pub struct DocumentCascadeDataIter<'a> {
    iter: PerOriginIter<'a, ()>,
    cascade_data: &'a DocumentCascadeData,
}

impl<'a> Iterator for DocumentCascadeDataIter<'a> {
    type Item = (&'a CascadeData, Origin);

    fn next(&mut self) -> Option<Self::Item> {
        let (_, origin) = self.iter.next()?;
        Some((self.cascade_data.borrow_for_origin(origin), origin))
    }
}

impl DocumentCascadeData {
    /// Borrows the cascade data for a given origin.
    #[inline]
    pub fn borrow_for_origin(&self, origin: Origin) -> &CascadeData {
        match origin {
            Origin::UserAgent => &self.user_agent.cascade_data,
            Origin::Author => &self.author,
            Origin::User => &self.user,
        }
    }

    fn iter_origins(&self) -> DocumentCascadeDataIter {
        DocumentCascadeDataIter {
            iter: self.per_origin.iter_origins(),
            cascade_data: self,
        }
    }

    fn iter_origins_rev(&self) -> DocumentCascadeDataIter {
        DocumentCascadeDataIter {
            iter: self.per_origin.iter_origins_rev(),
            cascade_data: self,
        }
    }

    /// Rebuild the cascade data for the given document stylesheets, and
    /// optionally with a set of user agent stylesheets.  Returns Err(..)
    /// to signify OOM.
    fn rebuild<'a, S>(
        &mut self,
        device: &Device,
        quirks_mode: QuirksMode,
        mut flusher: DocumentStylesheetFlusher<'a, S>,
        guards: &StylesheetGuards,
    ) -> Result<(), AllocErr>
    where
        S: StylesheetInDocument + PartialEq + 'static,
    {
        // First do UA sheets.
        {
            let origin_flusher = flusher.flush_origin(Origin::UserAgent);
            // Dirty check is just a minor optimization (no need to grab the
            // lock if nothing has changed).
            if origin_flusher.dirty() {
                let mut ua_cache = UA_CASCADE_DATA_CACHE.lock().unwrap();
                let new_data = ua_cache.lookup(
                    device,
                    quirks_mode,
                    origin_flusher,
                    guards.ua_or_user,
                    &self.user_agent,
                )?;
                if let Some(new_data) = new_data {
                    self.user_agent = new_data;
                }
                let _unused_entries = ua_cache.take_unused();
                // See the comments in take_unused() as for why the following
                // line.
                std::mem::drop(ua_cache);
            }
        }

        // Now do the user sheets.
        self.user.rebuild(
            device,
            quirks_mode,
            flusher.flush_origin(Origin::User),
            guards.ua_or_user,
        )?;

        // And now the author sheets.
        self.author.rebuild(
            device,
            quirks_mode,
            flusher.flush_origin(Origin::Author),
            guards.author,
        )?;

        Ok(())
    }

    /// Measures heap usage.
    #[cfg(feature = "gecko")]
    pub fn add_size_of(&self, ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes) {
        self.user.add_size_of(ops, sizes);
        self.author.add_size_of(ops, sizes);
    }
}

/// Whether author styles are enabled.
///
/// This is used to support Gecko.
#[allow(missing_docs)]
#[derive(Clone, Copy, Debug, Eq, MallocSizeOf, PartialEq)]
pub enum AuthorStylesEnabled {
    Yes,
    No,
}

/// A wrapper over a DocumentStylesheetSet that can be `Sync`, since it's only
/// used and exposed via mutable methods in the `Stylist`.
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
struct StylistStylesheetSet(DocumentStylesheetSet<StylistSheet>);
// Read above to see why this is fine.
unsafe impl Sync for StylistStylesheetSet {}

impl StylistStylesheetSet {
    fn new() -> Self {
        StylistStylesheetSet(DocumentStylesheetSet::new())
    }
}

impl ops::Deref for StylistStylesheetSet {
    type Target = DocumentStylesheetSet<StylistSheet>;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl ops::DerefMut for StylistStylesheetSet {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.0
    }
}

/// This structure holds all the selectors and device characteristics
/// for a given document. The selectors are converted into `Rule`s
/// and sorted into `SelectorMap`s keyed off stylesheet origin and
/// pseudo-element (see `CascadeData`).
///
/// This structure is effectively created once per pipeline, in the
/// LayoutThread corresponding to that pipeline.
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
pub struct Stylist {
    /// Device that the stylist is currently evaluating against.
    ///
    /// This field deserves a bigger comment due to the different use that Gecko
    /// and Servo give to it (that we should eventually unify).
    ///
    /// With Gecko, the device is never changed. Gecko manually tracks whether
    /// the device data should be reconstructed, and "resets" the state of the
    /// device.
    ///
    /// On Servo, on the other hand, the device is a really cheap representation
    /// that is recreated each time some constraint changes and calling
    /// `set_device`.
    device: Device,

    /// The list of stylesheets.
    stylesheets: StylistStylesheetSet,

    /// A cache of CascadeDatas for AuthorStylesheetSets (i.e., shadow DOM).
    author_data_cache: CascadeDataCache<CascadeData>,

    /// If true, the quirks-mode stylesheet is applied.
    #[cfg_attr(feature = "servo", ignore_malloc_size_of = "defined in selectors")]
    quirks_mode: QuirksMode,

    /// Selector maps for all of the style sheets in the stylist, after
    /// evalutaing media rules against the current device, split out per
    /// cascade level.
    cascade_data: DocumentCascadeData,

    /// Whether author styles are enabled.
    author_styles_enabled: AuthorStylesEnabled,

    /// The rule tree, that stores the results of selector matching.
    rule_tree: RuleTree,

    /// The set of registered custom properties from script.
    /// <https://drafts.css-houdini.org/css-properties-values-api-1/#dom-window-registeredpropertyset-slot>
    script_custom_properties: CustomPropertyScriptRegistry,

    /// Initial values for registered custom properties.
    initial_values_for_custom_properties: ComputedCustomProperties,

    /// Flags set from computing registered custom property initial values.
    initial_values_for_custom_properties_flags: ComputedValueFlags,

    /// The total number of times the stylist has been rebuilt.
    num_rebuilds: usize,
}

/// What cascade levels to include when styling elements.
#[derive(Clone, Copy, PartialEq)]
pub enum RuleInclusion {
    /// Include rules for style sheets at all cascade levels.  This is the
    /// normal rule inclusion mode.
    All,
    /// Only include rules from UA and user level sheets.  Used to implement
    /// `getDefaultComputedStyle`.
    DefaultOnly,
}

#[cfg(feature = "gecko")]
impl From<StyleRuleInclusion> for RuleInclusion {
    fn from(value: StyleRuleInclusion) -> Self {
        match value {
            StyleRuleInclusion::All => RuleInclusion::All,
            StyleRuleInclusion::DefaultOnly => RuleInclusion::DefaultOnly,
        }
    }
}

/// `:scope` selector, depending on the use case, can match a shadow host.
/// If used outside of `@scope`, it cannot possibly match the host.
/// Even when inside of `@scope`, it's conditional if the selector will
/// match the shadow host.
#[derive(Clone, Copy, Eq, PartialEq)]
enum ScopeMatchesShadowHost {
    NotApplicable,
    No,
    Yes,
}

impl Default for ScopeMatchesShadowHost {
    fn default() -> Self {
        Self::NotApplicable
    }
}

impl ScopeMatchesShadowHost {
    fn nest_for_scope(&mut self, matches_shadow_host: bool) {
        match *self {
            Self::NotApplicable => {
                // We're at the outermost `@scope`.
                *self = if matches_shadow_host {
                    Self::Yes
                } else {
                    Self::No
                };
            },
            Self::Yes if !matches_shadow_host => {
                // Inner `@scope` will not be able to match the shadow host.
                *self = Self::No;
            },
            _ => (),
        }
    }
}

/// Nested declarations have effectively two behaviors:
///  * Inside style rules (where they behave as the containing selector).
///  * Inside @scope (where they behave as :where(:scope)).
/// It is a bit unfortunate ideally we wouldn't need this, because scope also pushes to the
/// ancestor_selector_lists, but the behavior isn't quite the same as wrapping in `&`, see
/// https://github.com/w3c/csswg-drafts/issues/10431
#[derive(Copy, Clone)]
enum NestedDeclarationsContext {
    Style,
    Scope,
}

/// A struct containing state from ancestor rules like @layer / @import /
/// @container / nesting / @scope.
struct ContainingRuleState {
    layer_name: LayerName,
    layer_id: LayerId,
    container_condition_id: ContainerConditionId,
    in_starting_style: bool,
    scope_condition_id: ScopeConditionId,
    scope_matches_shadow_host: ScopeMatchesShadowHost,
    ancestor_selector_lists: SmallVec<[SelectorList<SelectorImpl>; 2]>,
    nested_declarations_context: NestedDeclarationsContext,
}

impl Default for ContainingRuleState {
    fn default() -> Self {
        Self {
            layer_name: LayerName::new_empty(),
            layer_id: LayerId::root(),
            container_condition_id: ContainerConditionId::none(),
            in_starting_style: false,
            ancestor_selector_lists: Default::default(),
            scope_condition_id: ScopeConditionId::none(),
            scope_matches_shadow_host: Default::default(),
            nested_declarations_context: NestedDeclarationsContext::Style,
        }
    }
}

struct SavedContainingRuleState {
    ancestor_selector_lists_len: usize,
    layer_name_len: usize,
    layer_id: LayerId,
    container_condition_id: ContainerConditionId,
    in_starting_style: bool,
    scope_condition_id: ScopeConditionId,
    scope_matches_shadow_host: ScopeMatchesShadowHost,
    nested_declarations_context: NestedDeclarationsContext,
}

impl ContainingRuleState {
    fn save(&self) -> SavedContainingRuleState {
        SavedContainingRuleState {
            ancestor_selector_lists_len: self.ancestor_selector_lists.len(),
            layer_name_len: self.layer_name.0.len(),
            layer_id: self.layer_id,
            container_condition_id: self.container_condition_id,
            in_starting_style: self.in_starting_style,
            scope_condition_id: self.scope_condition_id,
            scope_matches_shadow_host: self.scope_matches_shadow_host,
            nested_declarations_context: self.nested_declarations_context,
        }
    }

    fn restore(&mut self, saved: &SavedContainingRuleState) {
        debug_assert!(self.layer_name.0.len() >= saved.layer_name_len);
        debug_assert!(self.ancestor_selector_lists.len() >= saved.ancestor_selector_lists_len);
        self.ancestor_selector_lists
            .truncate(saved.ancestor_selector_lists_len);
        self.layer_name.0.truncate(saved.layer_name_len);
        self.layer_id = saved.layer_id;
        self.container_condition_id = saved.container_condition_id;
        self.in_starting_style = saved.in_starting_style;
        self.scope_condition_id = saved.scope_condition_id;
        self.scope_matches_shadow_host = saved.scope_matches_shadow_host;
        self.nested_declarations_context = saved.nested_declarations_context;
    }
}

type ReplacedSelectors = SmallVec<[Selector<SelectorImpl>; 4]>;

impl Stylist {
    /// Construct a new `Stylist`, using given `Device` and `QuirksMode`.
    /// If more members are added here, think about whether they should
    /// be reset in clear().
    #[inline]
    pub fn new(device: Device, quirks_mode: QuirksMode) -> Self {
        Self {
            device,
            quirks_mode,
            stylesheets: StylistStylesheetSet::new(),
            author_data_cache: CascadeDataCache::new(),
            cascade_data: Default::default(),
            author_styles_enabled: AuthorStylesEnabled::Yes,
            rule_tree: RuleTree::new(),
            script_custom_properties: Default::default(),
            initial_values_for_custom_properties: Default::default(),
            initial_values_for_custom_properties_flags: Default::default(),
            num_rebuilds: 0,
        }
    }

    /// Returns the document cascade data.
    #[inline]
    pub fn cascade_data(&self) -> &DocumentCascadeData {
        &self.cascade_data
    }

    /// Returns whether author styles are enabled or not.
    #[inline]
    pub fn author_styles_enabled(&self) -> AuthorStylesEnabled {
        self.author_styles_enabled
    }

    /// Iterate through all the cascade datas from the document.
    #[inline]
    pub fn iter_origins(&self) -> DocumentCascadeDataIter {
        self.cascade_data.iter_origins()
    }

    /// Does what the name says, to prevent author_data_cache to grow without
    /// bound.
    pub fn remove_unique_author_data_cache_entries(&mut self) {
        self.author_data_cache.take_unused();
    }

    /// Returns the custom property registration for this property's name.
    /// https://drafts.css-houdini.org/css-properties-values-api-1/#determining-registration
    pub fn get_custom_property_registration(&self, name: &Atom) -> &PropertyRegistrationData {
        if let Some(registration) = self.custom_property_script_registry().get(name) {
            return ®istration.data;
        }
        for (data, _) in self.iter_origins() {
            if let Some(registration) = data.custom_property_registrations.get(name) {
                return ®istration.data;
            }
        }
        PropertyRegistrationData::unregistered()
    }

    /// Returns custom properties with their registered initial values.
    pub fn get_custom_property_initial_values(&self) -> &ComputedCustomProperties {
        &self.initial_values_for_custom_properties
    }

    /// Returns flags set from computing the registered custom property initial values.
    pub fn get_custom_property_initial_values_flags(&self) -> ComputedValueFlags {
        self.initial_values_for_custom_properties_flags
    }

    /// Rebuild custom properties with their registered initial values.
    /// https://drafts.css-houdini.org/css-properties-values-api-1/#determining-registration
    pub fn rebuild_initial_values_for_custom_properties(&mut self) {
        let mut initial_values = ComputedCustomProperties::default();
        let initial_values_flags;
        {
            let mut seen_names = PrecomputedHashSet::default();
            let mut rule_cache_conditions = RuleCacheConditions::default();
            let context = computed::Context::new_for_initial_at_property_value(
                self,
                &mut rule_cache_conditions,
            );

            for (k, v) in self.custom_property_script_registry().properties().iter() {
                seen_names.insert(k.clone());
                let Ok(value) = v.compute_initial_value(&context) else {
                    continue;
                };
                let map = if v.inherits() {
                    &mut initial_values.inherited
                } else {
                    &mut initial_values.non_inherited
                };
                map.insert(k, value);
            }
            for (data, _) in self.iter_origins() {
                for (k, v) in data.custom_property_registrations.iter() {
                    if seen_names.insert(k.clone()) {
                        let last_value = &v.last().unwrap().0;
                        let Ok(value) = last_value.compute_initial_value(&context) else {
                            continue;
                        };
                        let map = if last_value.inherits() {
                            &mut initial_values.inherited
                        } else {
                            &mut initial_values.non_inherited
                        };
                        map.insert(k, value);
                    }
                }
            }
            initial_values_flags = context.builder.flags();
        }
        self.initial_values_for_custom_properties_flags = initial_values_flags;
        self.initial_values_for_custom_properties = initial_values;
    }

    /// Rebuilds (if needed) the CascadeData given a sheet collection.
    pub fn rebuild_author_data<S>(
        &mut self,
        old_data: &CascadeData,
        collection: SheetCollectionFlusher<S>,
        guard: &SharedRwLockReadGuard,
    ) -> Result<Option<Arc<CascadeData>>, AllocErr>
    where
        S: StylesheetInDocument + PartialEq + 'static,
    {
        self.author_data_cache.lookup(
            &self.device,
            self.quirks_mode,
            collection,
            guard,
            old_data,
        )
    }

    /// Iterate over the extra data in origin order.
    #[inline]
    pub fn iter_extra_data_origins(&self) -> ExtraStyleDataIterator {
        ExtraStyleDataIterator(self.cascade_data.iter_origins())
    }

    /// Iterate over the extra data in reverse origin order.
    #[inline]
    pub fn iter_extra_data_origins_rev(&self) -> ExtraStyleDataIterator {
        ExtraStyleDataIterator(self.cascade_data.iter_origins_rev())
    }

    /// Returns the number of selectors.
    pub fn num_selectors(&self) -> usize {
        self.cascade_data
            .iter_origins()
            .map(|(d, _)| d.num_selectors)
            .sum()
    }

    /// Returns the number of declarations.
    pub fn num_declarations(&self) -> usize {
        self.cascade_data
            .iter_origins()
            .map(|(d, _)| d.num_declarations)
            .sum()
    }

    /// Returns the number of times the stylist has been rebuilt.
    pub fn num_rebuilds(&self) -> usize {
        self.num_rebuilds
    }

    /// Returns the number of revalidation_selectors.
    pub fn num_revalidation_selectors(&self) -> usize {
        self.cascade_data
            .iter_origins()
            .map(|(data, _)| data.selectors_for_cache_revalidation.len())
            .sum()
    }

    /// Returns the number of entries in invalidation maps.
    pub fn num_invalidations(&self) -> usize {
        self.cascade_data
            .iter_origins()
            .map(|(data, _)| {
                data.invalidation_map.len() + data.relative_selector_invalidation_map.len()
            })
            .sum()
    }

    /// Returns whether the given DocumentState bit is relied upon by a selector
    /// of some rule.
    pub fn has_document_state_dependency(&self, state: DocumentState) -> bool {
        self.cascade_data
            .iter_origins()
            .any(|(d, _)| d.document_state_dependencies.intersects(state))
    }

    /// Flush the list of stylesheets if they changed, ensuring the stylist is
    /// up-to-date.
    pub fn flush<E>(
        &mut self,
        guards: &StylesheetGuards,
        document_element: Option<E>,
        snapshots: Option<&SnapshotMap>,
    ) -> bool
    where
        E: TElement,
    {
        if !self.stylesheets.has_changed() {
            return false;
        }

        self.num_rebuilds += 1;

        let flusher = self.stylesheets.flush(document_element, snapshots);

        let had_invalidations = flusher.had_invalidations();

        self.cascade_data
            .rebuild(&self.device, self.quirks_mode, flusher, guards)
            .unwrap_or_else(|_| warn!("OOM in Stylist::flush"));

        self.rebuild_initial_values_for_custom_properties();

        had_invalidations
    }

    /// Insert a given stylesheet before another stylesheet in the document.
    pub fn insert_stylesheet_before(
        &mut self,
        sheet: StylistSheet,
        before_sheet: StylistSheet,
        guard: &SharedRwLockReadGuard,
    ) {
        self.stylesheets
            .insert_stylesheet_before(Some(&self.device), sheet, before_sheet, guard)
    }

    /// Marks a given stylesheet origin as dirty, due to, for example, changes
    /// in the declarations that affect a given rule.
    ///
    /// FIXME(emilio): Eventually it'd be nice for this to become more
    /// fine-grained.
    pub fn force_stylesheet_origins_dirty(&mut self, origins: OriginSet) {
        self.stylesheets.force_dirty(origins)
    }

    /// Sets whether author style is enabled or not.
    pub fn set_author_styles_enabled(&mut self, enabled: AuthorStylesEnabled) {
        self.author_styles_enabled = enabled;
    }

    /// Returns whether we've recorded any stylesheet change so far.
    pub fn stylesheets_have_changed(&self) -> bool {
        self.stylesheets.has_changed()
    }

    /// Appends a new stylesheet to the current set.
    pub fn append_stylesheet(&mut self, sheet: StylistSheet, guard: &SharedRwLockReadGuard) {
        self.stylesheets
            .append_stylesheet(Some(&self.device), sheet, guard)
    }

    /// Remove a given stylesheet to the current set.
    pub fn remove_stylesheet(&mut self, sheet: StylistSheet, guard: &SharedRwLockReadGuard) {
        self.stylesheets
            .remove_stylesheet(Some(&self.device), sheet, guard)
    }

    /// Notify of a change of a given rule.
    pub fn rule_changed(
        &mut self,
        sheet: &StylistSheet,
        rule: &CssRule,
        guard: &SharedRwLockReadGuard,
        change_kind: RuleChangeKind,
    ) {
        self.stylesheets
            .rule_changed(Some(&self.device), sheet, rule, guard, change_kind)
    }

    /// Appends a new stylesheet to the current set.
    #[inline]
    pub fn sheet_count(&self, origin: Origin) -> usize {
        self.stylesheets.sheet_count(origin)
    }

    /// Appends a new stylesheet to the current set.
    #[inline]
    pub fn sheet_at(&self, origin: Origin, index: usize) -> Option<&StylistSheet> {
        self.stylesheets.get(origin, index)
    }

    /// Returns whether for any of the applicable style rule data a given
    /// condition is true.
    pub fn any_applicable_rule_data<E, F>(&self, element: E, mut f: F) -> bool
    where
        E: TElement,
        F: FnMut(&CascadeData) -> bool,
    {
        if f(&self.cascade_data.user_agent.cascade_data) {
            return true;
        }

        let mut maybe = false;

        let doc_author_rules_apply =
            element.each_applicable_non_document_style_rule_data(|data, _| {
                maybe = maybe || f(&*data);
            });

        if maybe || f(&self.cascade_data.user) {
            return true;
        }

        doc_author_rules_apply && f(&self.cascade_data.author)
    }

    /// Execute callback for all applicable style rule data.
    pub fn for_each_cascade_data_with_scope<'a, E, F>(&'a self, element: E, mut f: F)
    where
        E: TElement + 'a,
        F: FnMut(&'a CascadeData, Option<E>),
    {
        f(&self.cascade_data.user_agent.cascade_data, None);
        element.each_applicable_non_document_style_rule_data(|data, scope| {
            f(data, Some(scope));
        });
        f(&self.cascade_data.user, None);
        f(&self.cascade_data.author, None);
    }

    /// Computes the style for a given "precomputed" pseudo-element, taking the
    /// universal rules and applying them.
    pub fn precomputed_values_for_pseudo<E>(
        &self,
        guards: &StylesheetGuards,
        pseudo: &PseudoElement,
        parent: Option<&ComputedValues>,
    ) -> Arc<ComputedValues>
    where
        E: TElement,
    {
        debug_assert!(pseudo.is_precomputed());

        let rule_node = self.rule_node_for_precomputed_pseudo(guards, pseudo, vec![]);

        self.precomputed_values_for_pseudo_with_rule_node::<E>(guards, pseudo, parent, rule_node)
    }

    /// Computes the style for a given "precomputed" pseudo-element with
    /// given rule node.
    ///
    /// TODO(emilio): The type parameter could go away with a void type
    /// implementing TElement.
    pub fn precomputed_values_for_pseudo_with_rule_node<E>(
        &self,
        guards: &StylesheetGuards,
        pseudo: &PseudoElement,
        parent: Option<&ComputedValues>,
        rules: StrongRuleNode,
    ) -> Arc<ComputedValues>
    where
        E: TElement,
    {
        self.compute_pseudo_element_style_with_inputs::<E>(
            CascadeInputs {
                rules: Some(rules),
                visited_rules: None,
                flags: Default::default(),
            },
            pseudo,
            guards,
            parent,
            /* element */ None,
        )
    }

    /// Returns the rule node for a given precomputed pseudo-element.
    ///
    /// If we want to include extra declarations to this precomputed
    /// pseudo-element, we can provide a vector of ApplicableDeclarationBlocks
    /// to extra_declarations. This is useful for @page rules.
    pub fn rule_node_for_precomputed_pseudo(
        &self,
        guards: &StylesheetGuards,
        pseudo: &PseudoElement,
        mut extra_declarations: Vec<ApplicableDeclarationBlock>,
    ) -> StrongRuleNode {
        let mut declarations_with_extra;
        let declarations = match self
            .cascade_data
            .user_agent
            .precomputed_pseudo_element_decls
            .get(pseudo)
        {
            Some(declarations) => {
                if !extra_declarations.is_empty() {
                    declarations_with_extra = declarations.clone();
                    declarations_with_extra.append(&mut extra_declarations);
                    &*declarations_with_extra
                } else {
                    &**declarations
                }
            },
            None => &[],
        };

        self.rule_tree.insert_ordered_rules_with_important(
            declarations.into_iter().map(|a| a.clone().for_rule_tree()),
            guards,
        )
    }

    /// Returns the style for an anonymous box of the given type.
    ///
    /// TODO(emilio): The type parameter could go away with a void type
    /// implementing TElement.
    #[cfg(feature = "servo")]
    pub fn style_for_anonymous<E>(
        &self,
        guards: &StylesheetGuards,
        pseudo: &PseudoElement,
        parent_style: &ComputedValues,
    ) -> Arc<ComputedValues>
    where
        E: TElement,
    {
        self.precomputed_values_for_pseudo::<E>(guards, &pseudo, Some(parent_style))
    }

    /// Computes a pseudo-element style lazily during layout.
    ///
    /// This can only be done for a certain set of pseudo-elements, like
    /// :selection.
    ///
    /// Check the documentation on lazy pseudo-elements in
    /// docs/components/style.md
    pub fn lazily_compute_pseudo_element_style<E>(
        &self,
        guards: &StylesheetGuards,
        element: E,
        pseudo: &PseudoElement,
        rule_inclusion: RuleInclusion,
        originating_element_style: &ComputedValues,
        is_probe: bool,
        matching_fn: Option<&dyn Fn(&PseudoElement) -> bool>,
    ) -> Option<Arc<ComputedValues>>
    where
        E: TElement,
    {
        let cascade_inputs = self.lazy_pseudo_rules(
            guards,
            element,
            originating_element_style,
            pseudo,
            is_probe,
            rule_inclusion,
            matching_fn,
        )?;

        Some(self.compute_pseudo_element_style_with_inputs(
            cascade_inputs,
            pseudo,
            guards,
            Some(originating_element_style),
            Some(element),
        ))
    }

    /// Computes a pseudo-element style lazily using the given CascadeInputs.
    /// This can be used for truly lazy pseudo-elements or to avoid redoing
    /// selector matching for eager pseudo-elements when we need to recompute
    /// their style with a new parent style.
    pub fn compute_pseudo_element_style_with_inputs<E>(
        &self,
        inputs: CascadeInputs,
        pseudo: &PseudoElement,
        guards: &StylesheetGuards,
        parent_style: Option<&ComputedValues>,
        element: Option<E>,
    ) -> Arc<ComputedValues>
    where
        E: TElement,
    {
        // FIXME(emilio): The lack of layout_parent_style here could be
        // worrying, but we're probably dropping the display fixup for
        // pseudos other than before and after, so it's probably ok.
        //
        // (Though the flags don't indicate so!)
        //
        // It'd be fine to assert that this isn't called with a parent style
        // where display contents is in effect, but in practice this is hard to
        // do for stuff like :-moz-fieldset-content with a
        // <fieldset style="display: contents">. That is, the computed value of
        // display for the fieldset is "contents", even though it's not the used
        // value, so we don't need to adjust in a different way anyway.
        self.cascade_style_and_visited(
            element,
            Some(pseudo),
            inputs,
            guards,
            parent_style,
            parent_style,
            FirstLineReparenting::No,
            /* rule_cache = */ None,
            &mut RuleCacheConditions::default(),
        )
    }

    /// Computes a style using the given CascadeInputs.  This can be used to
    /// compute a style any time we know what rules apply and just need to use
    /// the given parent styles.
    ///
    /// parent_style is the style to inherit from for properties affected by
    /// first-line ancestors.
    ///
    /// parent_style_ignoring_first_line is the style to inherit from for
    /// properties not affected by first-line ancestors.
    ///
    /// layout_parent_style is the style used for some property fixups.  It's
    /// the style of the nearest ancestor with a layout box.
    pub fn cascade_style_and_visited<E>(
        &self,
        element: Option<E>,
        pseudo: Option<&PseudoElement>,
        inputs: CascadeInputs,
        guards: &StylesheetGuards,
        parent_style: Option<&ComputedValues>,
        layout_parent_style: Option<&ComputedValues>,
        first_line_reparenting: FirstLineReparenting,
        rule_cache: Option<&RuleCache>,
        rule_cache_conditions: &mut RuleCacheConditions,
    ) -> Arc<ComputedValues>
    where
        E: TElement,
    {
        debug_assert!(pseudo.is_some() || element.is_some(), "Huh?");

        // We need to compute visited values if we have visited rules or if our
        // parent has visited values.
        let visited_rules = match inputs.visited_rules.as_ref() {
            Some(rules) => Some(rules),
            None => {
                if parent_style.and_then(|s| s.visited_style()).is_some() {
                    Some(inputs.rules.as_ref().unwrap_or(self.rule_tree.root()))
                } else {
                    None
                }
            },
        };

        // Read the comment on `precomputed_values_for_pseudo` to see why it's
        // difficult to assert that display: contents nodes never arrive here
        // (tl;dr: It doesn't apply for replaced elements and such, but the
        // computed value is still "contents").
        //
        // FIXME(emilio): We should assert that it holds if pseudo.is_none()!
        properties::cascade::<E>(
            &self,
            pseudo,
            inputs.rules.as_ref().unwrap_or(self.rule_tree.root()),
            guards,
            parent_style,
            layout_parent_style,
            first_line_reparenting,
            visited_rules,
            inputs.flags,
            rule_cache,
            rule_cache_conditions,
            element,
        )
    }

    /// Computes the cascade inputs for a lazily-cascaded pseudo-element.
    ///
    /// See the documentation on lazy pseudo-elements in
    /// docs/components/style.md
    fn lazy_pseudo_rules<E>(
        &self,
        guards: &StylesheetGuards,
        element: E,
        originating_element_style: &ComputedValues,
        pseudo: &PseudoElement,
        is_probe: bool,
        rule_inclusion: RuleInclusion,
        matching_fn: Option<&dyn Fn(&PseudoElement) -> bool>,
    ) -> Option<CascadeInputs>
    where
        E: TElement,
    {
        debug_assert!(pseudo.is_lazy());

        let mut selector_caches = SelectorCaches::default();
        // No need to bother setting the selector flags when we're computing
        // default styles.
        let needs_selector_flags = if rule_inclusion == RuleInclusion::DefaultOnly {
            NeedsSelectorFlags::No
        } else {
            NeedsSelectorFlags::Yes
        };

        let mut declarations = ApplicableDeclarationList::new();
        let mut matching_context = MatchingContext::<'_, E::Impl>::new(
            MatchingMode::ForStatelessPseudoElement,
            None,
            &mut selector_caches,
            self.quirks_mode,
            needs_selector_flags,
            MatchingForInvalidation::No,
        );

        matching_context.pseudo_element_matching_fn = matching_fn;
        matching_context.extra_data.originating_element_style = Some(originating_element_style);

        self.push_applicable_declarations(
            element,
            Some(&pseudo),
            None,
            None,
            /* animation_declarations = */ Default::default(),
            rule_inclusion,
            &mut declarations,
            &mut matching_context,
        );

        if declarations.is_empty() && is_probe {
            return None;
        }

        let rules = self.rule_tree.compute_rule_node(&mut declarations, guards);

        let mut visited_rules = None;
        if originating_element_style.visited_style().is_some() {
            let mut declarations = ApplicableDeclarationList::new();
            let mut selector_caches = SelectorCaches::default();

            let mut matching_context = MatchingContext::<'_, E::Impl>::new_for_visited(
                MatchingMode::ForStatelessPseudoElement,
                None,
                &mut selector_caches,
                VisitedHandlingMode::RelevantLinkVisited,
                selectors::matching::IncludeStartingStyle::No,
                self.quirks_mode,
                needs_selector_flags,
                MatchingForInvalidation::No,
            );
            matching_context.pseudo_element_matching_fn = matching_fn;
            matching_context.extra_data.originating_element_style = Some(originating_element_style);

            self.push_applicable_declarations(
                element,
                Some(&pseudo),
                None,
                None,
                /* animation_declarations = */ Default::default(),
                rule_inclusion,
                &mut declarations,
                &mut matching_context,
            );
            if !declarations.is_empty() {
                let rule_node = self.rule_tree.insert_ordered_rules_with_important(
                    declarations.drain(..).map(|a| a.for_rule_tree()),
                    guards,
                );
                if rule_node != *self.rule_tree.root() {
                    visited_rules = Some(rule_node);
                }
            }
        }

        Some(CascadeInputs {
            rules: Some(rules),
            visited_rules,
            flags: matching_context.extra_data.cascade_input_flags,
        })
    }

    /// Set a given device, which may change the styles that apply to the
    /// document.
    ///
    /// Returns the sheet origins that were actually affected.
    ///
    /// This means that we may need to rebuild style data even if the
    /// stylesheets haven't changed.
    ///
    /// Also, the device that arrives here may need to take the viewport rules
    /// into account.
    pub fn set_device(&mut self, device: Device, guards: &StylesheetGuards) -> OriginSet {
        self.device = device;
        self.media_features_change_changed_style(guards, &self.device)
    }

    /// Returns whether, given a media feature change, any previously-applicable
    /// style has become non-applicable, or vice-versa for each origin, using
    /// `device`.
    pub fn media_features_change_changed_style(
        &self,
        guards: &StylesheetGuards,
        device: &Device,
    ) -> OriginSet {
        debug!("Stylist::media_features_change_changed_style {:?}", device);

        let mut origins = OriginSet::empty();
        let stylesheets = self.stylesheets.iter();

        for (stylesheet, origin) in stylesheets {
            if origins.contains(origin.into()) {
                continue;
            }

            let guard = guards.for_origin(origin);
            let origin_cascade_data = self.cascade_data.borrow_for_origin(origin);

            let affected_changed = !origin_cascade_data.media_feature_affected_matches(
                stylesheet,
                guard,
                device,
                self.quirks_mode,
            );

            if affected_changed {
                origins |= origin;
            }
        }

        origins
    }

    /// Returns the Quirks Mode of the document.
    pub fn quirks_mode(&self) -> QuirksMode {
        self.quirks_mode
    }

    /// Sets the quirks mode of the document.
    pub fn set_quirks_mode(&mut self, quirks_mode: QuirksMode) {
        if self.quirks_mode == quirks_mode {
            return;
        }
        self.quirks_mode = quirks_mode;
        self.force_stylesheet_origins_dirty(OriginSet::all());
    }

    /// Returns the applicable CSS declarations for the given element.
    pub fn push_applicable_declarations<E>(
        &self,
        element: E,
        pseudo_element: Option<&PseudoElement>,
        style_attribute: Option<ArcBorrow<Locked<PropertyDeclarationBlock>>>,
        smil_override: Option<ArcBorrow<Locked<PropertyDeclarationBlock>>>,
        animation_declarations: AnimationDeclarations,
        rule_inclusion: RuleInclusion,
        applicable_declarations: &mut ApplicableDeclarationList,
        context: &mut MatchingContext<E::Impl>,
    ) where
        E: TElement,
    {
        RuleCollector::new(
            self,
            element,
            pseudo_element,
            style_attribute,
            smil_override,
            animation_declarations,
            rule_inclusion,
            applicable_declarations,
            context,
        )
        .collect_all();
    }

    /// Given an id, returns whether there might be any rules for that id in any
    /// of our rule maps.
    #[inline]
    pub fn may_have_rules_for_id<E>(&self, id: &WeakAtom, element: E) -> bool
    where
        E: TElement,
    {
        // If id needs to be compared case-insensitively, the logic below
        // wouldn't work. Just conservatively assume it may have such rules.
        match self.quirks_mode().classes_and_ids_case_sensitivity() {
            CaseSensitivity::AsciiCaseInsensitive => return true,
            CaseSensitivity::CaseSensitive => {},
        }

        self.any_applicable_rule_data(element, |data| data.mapped_ids.contains(id))
    }

    /// Returns the registered `@keyframes` animation for the specified name.
    #[inline]
    pub fn get_animation<'a, E>(&'a self, name: &Atom, element: E) -> Option<&'a KeyframesAnimation>
    where
        E: TElement + 'a,
    {
        macro_rules! try_find_in {
            ($data:expr) => {
                if let Some(animation) = $data.animations.get(name) {
                    return Some(animation);
                }
            };
        }

        // NOTE(emilio): This is a best-effort thing, the right fix is a bit TBD because it
        // involves "recording" which tree the name came from, see [1][2].
        //
        // [1]: https://github.com/w3c/csswg-drafts/issues/1995
        // [2]: https://bugzil.la/1458189
        let mut animation = None;
        let doc_rules_apply =
            element.each_applicable_non_document_style_rule_data(|data, _host| {
                if animation.is_none() {
                    animation = data.animations.get(name);
                }
            });

        if animation.is_some() {
            return animation;
        }

        if doc_rules_apply {
            try_find_in!(self.cascade_data.author);
        }
        try_find_in!(self.cascade_data.user);
        try_find_in!(self.cascade_data.user_agent.cascade_data);

        None
    }

    /// Computes the match results of a given element against the set of
    /// revalidation selectors.
    pub fn match_revalidation_selectors<E>(
        &self,
        element: E,
        bloom: Option<&BloomFilter>,
        selector_caches: &mut SelectorCaches,
        needs_selector_flags: NeedsSelectorFlags,
    ) -> RevalidationResult
    where
        E: TElement,
    {
        // NB: `MatchingMode` doesn't really matter, given we don't share style
        // between pseudos.
        let mut matching_context = MatchingContext::new(
            MatchingMode::Normal,
            bloom,
            selector_caches,
            self.quirks_mode,
            needs_selector_flags,
            MatchingForInvalidation::No,
        );

        // Note that, by the time we're revalidating, we're guaranteed that the
        // candidate and the entry have the same id, classes, and local name.
        // This means we're guaranteed to get the same rulehash buckets for all
        // the lookups, which means that the bitvecs are comparable. We verify
        // this in the caller by asserting that the bitvecs are same-length.
        let mut result = RevalidationResult::default();
        let mut relevant_attributes = &mut result.relevant_attributes;
        let selectors_matched = &mut result.selectors_matched;

        let matches_document_rules =
            element.each_applicable_non_document_style_rule_data(|data, host| {
                matching_context.with_shadow_host(Some(host), |matching_context| {
                    data.selectors_for_cache_revalidation.lookup(
                        element,
                        self.quirks_mode,
                        Some(&mut relevant_attributes),
                        |selector_and_hashes| {
                            selectors_matched.push(matches_selector(
                                &selector_and_hashes.selector,
                                selector_and_hashes.selector_offset,
                                Some(&selector_and_hashes.hashes),
                                &element,
                                matching_context,
                            ));
                            true
                        },
                    );
                })
            });

        for (data, origin) in self.cascade_data.iter_origins() {
            if origin == Origin::Author && !matches_document_rules {
                continue;
            }

            data.selectors_for_cache_revalidation.lookup(
                element,
                self.quirks_mode,
                Some(&mut relevant_attributes),
                |selector_and_hashes| {
                    selectors_matched.push(matches_selector(
                        &selector_and_hashes.selector,
                        selector_and_hashes.selector_offset,
                        Some(&selector_and_hashes.hashes),
                        &element,
                        &mut matching_context,
                    ));
                    true
                },
            );
        }

        result
    }

    /// Computes currently active scopes for the given element for revalidation purposes.
    pub fn revalidate_scopes<E: TElement>(
        &self,
        element: &E,
        selector_caches: &mut SelectorCaches,
        needs_selector_flags: NeedsSelectorFlags,
    ) -> ScopeRevalidationResult {
        let mut matching_context = MatchingContext::new(
            MatchingMode::Normal,
            None,
            selector_caches,
            self.quirks_mode,
            needs_selector_flags,
            MatchingForInvalidation::No,
        );

        let mut result = ScopeRevalidationResult::default();
        let matches_document_rules =
            element.each_applicable_non_document_style_rule_data(|data, host| {
                matching_context.with_shadow_host(Some(host), |matching_context| {
                    data.revalidate_scopes(self, element, matching_context, &mut result);
                })
            });

        for (data, origin) in self.cascade_data.iter_origins() {
            if origin == Origin::Author && !matches_document_rules {
                continue;
            }

            data.revalidate_scopes(self, element, &mut matching_context, &mut result);
        }

        result
    }

    /// Computes styles for a given declaration with parent_style.
    ///
    /// FIXME(emilio): the lack of pseudo / cascade flags look quite dubious,
    /// hopefully this is only used for some canvas font stuff.
    ///
    /// TODO(emilio): The type parameter can go away when
    /// https://github.com/rust-lang/rust/issues/35121 is fixed.
    pub fn compute_for_declarations<E>(
        &self,
        guards: &StylesheetGuards,
        parent_style: &ComputedValues,
        declarations: Arc<Locked<PropertyDeclarationBlock>>,
    ) -> Arc<ComputedValues>
    where
        E: TElement,
    {
        let block = declarations.read_with(guards.author);

        // We don't bother inserting these declarations in the rule tree, since
        // it'd be quite useless and slow.
        //
        // TODO(emilio): Now that we fixed bug 1493420, we should consider
        // reversing this as it shouldn't be slow anymore, and should avoid
        // generating two instantiations of apply_declarations.
        properties::apply_declarations::<E, _>(
            &self,
            /* pseudo = */ None,
            self.rule_tree.root(),
            guards,
            block.declaration_importance_iter().map(|(declaration, _)| {
                (
                    declaration,
                    CascadePriority::new(
                        CascadeLevel::same_tree_author_normal(),
                        LayerOrder::root(),
                    ),
                )
            }),
            Some(parent_style),
            Some(parent_style),
            FirstLineReparenting::No,
            CascadeMode::Unvisited {
                visited_rules: None,
            },
            Default::default(),
            /* rule_cache = */ None,
            &mut Default::default(),
            /* element = */ None,
        )
    }

    /// Accessor for a shared reference to the device.
    #[inline]
    pub fn device(&self) -> &Device {
        &self.device
    }

    /// Accessor for a mutable reference to the device.
    #[inline]
    pub fn device_mut(&mut self) -> &mut Device {
        &mut self.device
    }

    /// Accessor for a shared reference to the rule tree.
    #[inline]
    pub fn rule_tree(&self) -> &RuleTree {
        &self.rule_tree
    }

    /// Returns the script-registered custom property registry.
    #[inline]
    pub fn custom_property_script_registry(&self) -> &CustomPropertyScriptRegistry {
        &self.script_custom_properties
    }

    /// Returns the script-registered custom property registry, as a mutable ref.
    #[inline]
    pub fn custom_property_script_registry_mut(&mut self) -> &mut CustomPropertyScriptRegistry {
        &mut self.script_custom_properties
    }

    /// Measures heap usage.
    #[cfg(feature = "gecko")]
    pub fn add_size_of(&self, ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes) {
        self.cascade_data.add_size_of(ops, sizes);
        self.author_data_cache.add_size_of(ops, sizes);
        sizes.mRuleTree += self.rule_tree.size_of(ops);

        // We may measure other fields in the future if DMD says it's worth it.
    }

    /// Shutdown the static data that this module stores.
    pub fn shutdown() {
        let _entries = UA_CASCADE_DATA_CACHE.lock().unwrap().take_all();
    }
}

/// A vector that is sorted in layer order.
#[derive(Clone, Debug, Deref, MallocSizeOf)]
pub struct LayerOrderedVec<T>(Vec<(T, LayerId)>);
impl<T> Default for LayerOrderedVec<T> {
    fn default() -> Self {
        Self(Default::default())
    }
}

/// A map that is sorted in layer order.
#[derive(Clone, Debug, Deref, MallocSizeOf)]
pub struct LayerOrderedMap<T>(PrecomputedHashMap<Atom, SmallVec<[(T, LayerId); 1]>>);
impl<T> Default for LayerOrderedMap<T> {
    fn default() -> Self {
        Self(Default::default())
    }
}

#[cfg(feature = "gecko")]
impl<T: 'static> LayerOrderedVec<T> {
    fn clear(&mut self) {
        self.0.clear();
    }
    fn push(&mut self, v: T, id: LayerId) {
        self.0.push((v, id));
    }
    fn sort(&mut self, layers: &[CascadeLayer]) {
        self.0
            .sort_by_key(|&(_, ref id)| layers[id.0 as usize].order)
    }
}

impl<T: 'static> LayerOrderedMap<T> {
    fn shrink_if_needed(&mut self) {
        self.0.shrink_if_needed();
    }
    fn clear(&mut self) {
        self.0.clear();
    }
    fn try_insert(&mut self, name: Atom, v: T, id: LayerId) -> Result<(), AllocErr> {
        self.try_insert_with(name, v, id, |_, _| Ordering::Equal)
    }
    fn try_insert_with(
        &mut self,
        name: Atom,
        v: T,
        id: LayerId,
        cmp: impl Fn(&T, &T) -> Ordering,
    ) -> Result<(), AllocErr> {
        self.0.try_reserve(1)?;
        let vec = self.0.entry(name).or_default();
        if let Some(&mut (ref mut val, ref last_id)) = vec.last_mut() {
            if *last_id == id {
                if cmp(&val, &v) != Ordering::Greater {
                    *val = v;
                }
                return Ok(());
            }
        }
        vec.push((v, id));
        Ok(())
    }
    fn sort(&mut self, layers: &[CascadeLayer]) {
        self.sort_with(layers, |_, _| Ordering::Equal)
    }
    fn sort_with(&mut self, layers: &[CascadeLayer], cmp: impl Fn(&T, &T) -> Ordering) {
        for (_, v) in self.0.iter_mut() {
            v.sort_by(|&(ref v1, ref id1), &(ref v2, ref id2)| {
                let order1 = layers[id1.0 as usize].order;
                let order2 = layers[id2.0 as usize].order;
                order1.cmp(&order2).then_with(|| cmp(v1, v2))
            })
        }
    }
    /// Get an entry on the LayerOrderedMap by name.
    pub fn get(&self, name: &Atom) -> Option<&T> {
        let vec = self.0.get(name)?;
        Some(&vec.last()?.0)
    }
}

/// Wrapper to allow better tracking of memory usage by page rule lists.
///
/// This includes the layer ID for use with the named page table.
#[derive(Clone, Debug, MallocSizeOf)]
pub struct PageRuleData {
    /// Layer ID for sorting page rules after matching.
    pub layer: LayerId,
    /// Page rule
    #[ignore_malloc_size_of = "Arc, stylesheet measures as primary ref"]
    pub rule: Arc<Locked<PageRule>>,
}

/// Stores page rules indexed by page names.
#[derive(Clone, Debug, Default, MallocSizeOf)]
pub struct PageRuleMap {
    /// Page rules, indexed by page name. An empty atom indicates no page name.
    pub rules: PrecomputedHashMap<Atom, SmallVec<[PageRuleData; 1]>>,
}

#[cfg(feature = "gecko")]
impl PageRuleMap {
    #[inline]
    fn clear(&mut self) {
        self.rules.clear();
    }

    /// Uses page-name and pseudo-classes to match all applicable
    /// page-rules and append them to the matched_rules vec.
    /// This will ensure correct rule order for cascading.
    pub fn match_and_append_rules(
        &self,
        matched_rules: &mut Vec<ApplicableDeclarationBlock>,
        origin: Origin,
        guards: &StylesheetGuards,
        cascade_data: &DocumentCascadeData,
        name: &Option<Atom>,
        pseudos: PagePseudoClassFlags,
    ) {
        let level = match origin {
            Origin::UserAgent => CascadeLevel::UANormal,
            Origin::User => CascadeLevel::UserNormal,
--> --------------------

--> maximum size reached

--> --------------------