selectors/
visitor.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5//! Visitor traits for selectors.
6
7#![deny(missing_docs)]
8
9use crate::attr::NamespaceConstraint;
10use crate::parser::{Combinator, Component, RelativeSelector, Selector, SelectorImpl};
11use bitflags::bitflags;
12
13/// A trait to visit selector properties.
14///
15/// All the `visit_foo` methods return a boolean indicating whether the
16/// traversal should continue or not.
17pub trait SelectorVisitor: Sized {
18    /// The selector implementation this visitor wants to visit.
19    type Impl: SelectorImpl;
20
21    /// Visit an attribute selector that may match (there are other selectors
22    /// that may never match, like those containing whitespace or the empty
23    /// string).
24    fn visit_attribute_selector(
25        &mut self,
26        _namespace: &NamespaceConstraint<&<Self::Impl as SelectorImpl>::NamespaceUrl>,
27        _local_name: &<Self::Impl as SelectorImpl>::LocalName,
28        _local_name_lower: &<Self::Impl as SelectorImpl>::LocalName,
29    ) -> bool {
30        true
31    }
32
33    /// Visit a simple selector.
34    fn visit_simple_selector(&mut self, _: &Component<Self::Impl>) -> bool {
35        true
36    }
37
38    /// Visit a nested relative selector list. The caller is responsible to call visit
39    /// into the internal selectors if / as needed.
40    ///
41    /// The default implementation skips it altogether.
42    fn visit_relative_selector_list(&mut self, _list: &[RelativeSelector<Self::Impl>]) -> bool {
43        true
44    }
45
46    /// Visit a nested selector list. The caller is responsible to call visit
47    /// into the internal selectors if / as needed.
48    ///
49    /// The default implementation does this.
50    fn visit_selector_list(
51        &mut self,
52        _list_kind: SelectorListKind,
53        list: &[Selector<Self::Impl>],
54    ) -> bool {
55        for nested in list {
56            if !nested.visit(self) {
57                return false;
58            }
59        }
60        true
61    }
62
63    /// Visits a complex selector.
64    ///
65    /// Gets the combinator to the right of the selector, or `None` if the
66    /// selector is the rightmost one.
67    fn visit_complex_selector(&mut self, _combinator_to_right: Option<Combinator>) -> bool {
68        true
69    }
70}
71
72bitflags! {
73    /// The kinds of components the visitor is visiting the selector list of, if any
74    #[derive(Clone, Copy, Default)]
75    pub struct SelectorListKind: u8 {
76        /// The visitor is inside :not(..)
77        const NEGATION = 1 << 0;
78        /// The visitor is inside :is(..)
79        const IS = 1 << 1;
80        /// The visitor is inside :where(..)
81        const WHERE = 1 << 2;
82        /// The visitor is inside :nth-child(.. of <selector list>) or
83        /// :nth-last-child(.. of <selector list>)
84        const NTH_OF = 1 << 3;
85        /// The visitor is inside :has(..)
86        const HAS = 1 << 4;
87    }
88}
89
90impl SelectorListKind {
91    /// Construct a SelectorListKind for the corresponding component.
92    pub fn from_component<Impl: SelectorImpl>(component: &Component<Impl>) -> Self {
93        match component {
94            Component::Negation(_) => SelectorListKind::NEGATION,
95            Component::Is(_) => SelectorListKind::IS,
96            Component::Where(_) => SelectorListKind::WHERE,
97            Component::NthOf(_) => SelectorListKind::NTH_OF,
98            _ => SelectorListKind::empty(),
99        }
100    }
101
102    /// Whether the visitor is inside :not(..)
103    pub fn in_negation(&self) -> bool {
104        self.intersects(SelectorListKind::NEGATION)
105    }
106
107    /// Whether the visitor is inside :is(..)
108    pub fn in_is(&self) -> bool {
109        self.intersects(SelectorListKind::IS)
110    }
111
112    /// Whether the visitor is inside :where(..)
113    pub fn in_where(&self) -> bool {
114        self.intersects(SelectorListKind::WHERE)
115    }
116
117    /// Whether the visitor is inside :nth-child(.. of <selector list>) or
118    /// :nth-last-child(.. of <selector list>)
119    pub fn in_nth_of(&self) -> bool {
120        self.intersects(SelectorListKind::NTH_OF)
121    }
122
123    /// Whether the visitor is inside :has(..)
124    pub fn in_has(&self) -> bool {
125        self.intersects(SelectorListKind::HAS)
126    }
127
128    /// Whether this nested selector is relevant for nth-of dependencies.
129    pub fn relevant_to_nth_of_dependencies(&self) -> bool {
130        // Order of nesting for `:has` and `:nth-child(.. of ..)` doesn't matter, because:
131        // * `:has(:nth-child(.. of ..))`: The location of the anchoring element is
132        //   independent from where `:nth-child(.. of ..)` is applied.
133        // * `:nth-child(.. of :has(..))`: Invalidations inside `:has` must first use the
134        //   `:has` machinary to find the anchor, then carry out the remaining invalidation.
135        self.in_nth_of() && !self.in_has()
136    }
137}
selectors/visitor.rs

selectors/
visitor.rs
