servo/components/selectors/context.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 https://mozilla.org/MPL/2.0/. */

use crate::attr::CaseSensitivity;
use crate::bloom::BloomFilter;
use crate::nth_index_cache::NthIndexCache;
use crate::parser::SelectorImpl;
use crate::tree::{Element, OpaqueElement};

/// What kind of selector matching mode we should use.
///
/// There are two modes of selector matching. The difference is only noticeable
/// in presence of pseudo-elements.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum MatchingMode {
    /// Don't ignore any pseudo-element selectors.
    Normal,

    /// Ignores any stateless pseudo-element selectors in the rightmost sequence
    /// of simple selectors.
    ///
    /// This is useful, for example, to match against ::before when you aren't a
    /// pseudo-element yourself.
    ///
    /// For example, in presence of `::before:hover`, it would never match, but
    /// `::before` would be ignored as in "matching".
    ///
    /// It's required for all the selectors you match using this mode to have a
    /// pseudo-element.
    ForStatelessPseudoElement,
}

/// The mode to use when matching unvisited and visited links.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum VisitedHandlingMode {
    /// All links are matched as if they are unvisted.
    AllLinksUnvisited,
    /// All links are matched as if they are visited and unvisited (both :link
    /// and :visited match).
    ///
    /// This is intended to be used from invalidation code, to be conservative
    /// about whether we need to restyle a link.
    AllLinksVisitedAndUnvisited,
    /// A element's "relevant link" is the element being matched if it is a link
    /// or the nearest ancestor link. The relevant link is matched as though it
    /// is visited, and all other links are matched as if they are unvisited.
    RelevantLinkVisited,
}

impl VisitedHandlingMode {
    #[inline]
    pub fn matches_visited(&self) -> bool {
        matches!(
            *self,
            VisitedHandlingMode::RelevantLinkVisited |
                VisitedHandlingMode::AllLinksVisitedAndUnvisited
        )
    }

    #[inline]
    pub fn matches_unvisited(&self) -> bool {
        matches!(
            *self,
            VisitedHandlingMode::AllLinksUnvisited |
                VisitedHandlingMode::AllLinksVisitedAndUnvisited
        )
    }
}

/// Whether we need to set selector invalidation flags on elements for this
/// match request.
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum NeedsSelectorFlags {
    No,
    Yes,
}

/// Which quirks mode is this document in.
///
/// See: https://quirks.spec.whatwg.org/
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum QuirksMode {
    /// Quirks mode.
    Quirks,
    /// Limited quirks mode.
    LimitedQuirks,
    /// No quirks mode.
    NoQuirks,
}

impl QuirksMode {
    #[inline]
    pub fn classes_and_ids_case_sensitivity(self) -> CaseSensitivity {
        match self {
            QuirksMode::NoQuirks | QuirksMode::LimitedQuirks => CaseSensitivity::CaseSensitive,
            QuirksMode::Quirks => CaseSensitivity::AsciiCaseInsensitive,
        }
    }
}

/// Data associated with the matching process for a element.  This context is
/// used across many selectors for an element, so it's not appropriate for
/// transient data that applies to only a single selector.
pub struct MatchingContext<'a, Impl>
where
    Impl: SelectorImpl,
{
    /// Input with the matching mode we should use when matching selectors.
    matching_mode: MatchingMode,
    /// Input with the bloom filter used to fast-reject selectors.
    pub bloom_filter: Option<&'a BloomFilter>,
    /// An optional cache to speed up nth-index-like selectors.
    pub nth_index_cache: Option<&'a mut NthIndexCache>,
    /// The element which is going to match :scope pseudo-class. It can be
    /// either one :scope element, or the scoping element.
    ///
    /// Note that, although in theory there can be multiple :scope elements,
    /// in current specs, at most one is specified, and when there is one,
    /// scoping element is not relevant anymore, so we use a single field for
    /// them.
    ///
    /// When this is None, :scope will match the root element.
    ///
    /// See https://drafts.csswg.org/selectors-4/#scope-pseudo
    pub scope_element: Option<OpaqueElement>,

    /// The current shadow host we're collecting :host rules for.
    pub current_host: Option<OpaqueElement>,

    /// Controls how matching for links is handled.
    visited_handling: VisitedHandlingMode,

    /// The current nesting level of selectors that we're matching.
    ///
    /// FIXME(emilio): Consider putting the mutable stuff in a Cell, then make
    /// MatchingContext immutable again.
    nesting_level: usize,

    /// Whether we're inside a negation or not.
    in_negation: bool,

    /// An optional hook function for checking whether a pseudo-element
    /// should match when matching_mode is ForStatelessPseudoElement.
    pub pseudo_element_matching_fn: Option<&'a dyn Fn(&Impl::PseudoElement) -> bool>,

    /// Extra implementation-dependent matching data.
    pub extra_data: Impl::ExtraMatchingData,

    quirks_mode: QuirksMode,
    needs_selector_flags: NeedsSelectorFlags,
    classes_and_ids_case_sensitivity: CaseSensitivity,
    _impl: ::std::marker::PhantomData<Impl>,
}

impl<'a, Impl> MatchingContext<'a, Impl>
where
    Impl: SelectorImpl,
{
    /// Constructs a new `MatchingContext`.
    pub fn new(
        matching_mode: MatchingMode,
        bloom_filter: Option<&'a BloomFilter>,
        nth_index_cache: Option<&'a mut NthIndexCache>,
        quirks_mode: QuirksMode,
        needs_selector_flags: NeedsSelectorFlags,
    ) -> Self {
        Self::new_for_visited(
            matching_mode,
            bloom_filter,
            nth_index_cache,
            VisitedHandlingMode::AllLinksUnvisited,
            quirks_mode,
            needs_selector_flags,
        )
    }

    /// Constructs a new `MatchingContext` for use in visited matching.
    pub fn new_for_visited(
        matching_mode: MatchingMode,
        bloom_filter: Option<&'a BloomFilter>,
        nth_index_cache: Option<&'a mut NthIndexCache>,
        visited_handling: VisitedHandlingMode,
        quirks_mode: QuirksMode,
        needs_selector_flags: NeedsSelectorFlags,
    ) -> Self {
        Self {
            matching_mode,
            bloom_filter,
            visited_handling,
            nth_index_cache,
            quirks_mode,
            classes_and_ids_case_sensitivity: quirks_mode.classes_and_ids_case_sensitivity(),
            needs_selector_flags,
            scope_element: None,
            current_host: None,
            nesting_level: 0,
            in_negation: false,
            pseudo_element_matching_fn: None,
            extra_data: Default::default(),
            _impl: ::std::marker::PhantomData,
        }
    }

    /// Whether we're matching a nested selector.
    #[inline]
    pub fn is_nested(&self) -> bool {
        self.nesting_level != 0
    }

    /// Whether we're matching inside a :not(..) selector.
    #[inline]
    pub fn in_negation(&self) -> bool {
        self.in_negation
    }

    /// The quirks mode of the document.
    #[inline]
    pub fn quirks_mode(&self) -> QuirksMode {
        self.quirks_mode
    }

    /// The matching-mode for this selector-matching operation.
    #[inline]
    pub fn matching_mode(&self) -> MatchingMode {
        self.matching_mode
    }

    /// Whether we need to set selector flags.
    #[inline]
    pub fn needs_selector_flags(&self) -> bool {
        self.needs_selector_flags == NeedsSelectorFlags::Yes
    }

    /// The case-sensitivity for class and ID selectors
    #[inline]
    pub fn classes_and_ids_case_sensitivity(&self) -> CaseSensitivity {
        self.classes_and_ids_case_sensitivity
    }

    /// Runs F with a deeper nesting level.
    #[inline]
    pub fn nest<F, R>(&mut self, f: F) -> R
    where
        F: FnOnce(&mut Self) -> R,
    {
        self.nesting_level += 1;
        let result = f(self);
        self.nesting_level -= 1;
        result
    }

    /// Runs F with a deeper nesting level, and marking ourselves in a negation,
    /// for a :not(..) selector, for example.
    #[inline]
    pub fn nest_for_negation<F, R>(&mut self, f: F) -> R
    where
        F: FnOnce(&mut Self) -> R,
    {
        let old_in_negation = self.in_negation;
        self.in_negation = true;
        let result = self.nest(f);
        self.in_negation = old_in_negation;
        result
    }

    #[inline]
    pub fn visited_handling(&self) -> VisitedHandlingMode {
        self.visited_handling
    }

    /// Runs F with a different VisitedHandlingMode.
    #[inline]
    pub fn with_visited_handling_mode<F, R>(
        &mut self,
        handling_mode: VisitedHandlingMode,
        f: F,
    ) -> R
    where
        F: FnOnce(&mut Self) -> R,
    {
        let original_handling_mode = self.visited_handling;
        self.visited_handling = handling_mode;
        let result = f(self);
        self.visited_handling = original_handling_mode;
        result
    }

    /// Runs F with a given shadow host which is the root of the tree whose
    /// rules we're matching.
    #[inline]
    pub fn with_shadow_host<F, E, R>(&mut self, host: Option<E>, f: F) -> R
    where
        E: Element,
        F: FnOnce(&mut Self) -> R,
    {
        let original_host = self.current_host.take();
        self.current_host = host.map(|h| h.opaque());
        let result = f(self);
        self.current_host = original_host;
        result
    }

    /// Returns the current shadow host whose shadow root we're matching rules
    /// against.
    #[inline]
    pub fn shadow_host(&self) -> Option<OpaqueElement> {
        self.current_host
    }
}