Source code

Revision control

Copy as Markdown

Other Tools

/* 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 */
//! The pseudo-classes and pseudo-elements supported by the style system.
use crate::stylesheets::{Namespaces, Origin, UrlExtraData};
use crate::values::serialize_atom_identifier;
use crate::Atom;
use cssparser::{Parser as CssParser, ParserInput};
use dom::ElementState;
use selectors::parser::{ParseRelative, SelectorList};
use std::fmt::{self, Debug, Write};
use style_traits::{CssWriter, ParseError, ToCss};
/// A convenient alias for the type that represents an attribute value used for
/// selector parser implementation.
pub type AttrValue = <SelectorImpl as ::selectors::SelectorImpl>::AttrValue;
#[cfg(feature = "servo")]
pub use crate::servo::selector_parser::*;
#[cfg(feature = "gecko")]
pub use crate::gecko::selector_parser::*;
#[cfg(feature = "servo")]
pub use crate::servo::selector_parser::ServoElementSnapshot as Snapshot;
#[cfg(feature = "gecko")]
pub use crate::gecko::snapshot::GeckoElementSnapshot as Snapshot;
#[cfg(feature = "servo")]
pub use crate::servo::restyle_damage::ServoRestyleDamage as RestyleDamage;
#[cfg(feature = "gecko")]
pub use crate::gecko::restyle_damage::GeckoRestyleDamage as RestyleDamage;
/// Servo's selector parser.
#[cfg_attr(feature = "servo", derive(MallocSizeOf))]
pub struct SelectorParser<'a> {
/// The origin of the stylesheet we're parsing.
pub stylesheet_origin: Origin,
/// The namespace set of the stylesheet.
pub namespaces: &'a Namespaces,
/// The extra URL data of the stylesheet, which is used to look up
/// whether we are parsing a chrome:// URL style sheet.
pub url_data: &'a UrlExtraData,
/// Whether we're parsing selectors for `@supports`
pub for_supports_rule: bool,
impl<'a> SelectorParser<'a> {
/// Parse a selector list with an author origin and without taking into
/// account namespaces.
/// This is used for some DOM APIs like `querySelector`.
pub fn parse_author_origin_no_namespace<'i>(
input: &'i str,
url_data: &UrlExtraData,
) -> Result<SelectorList<SelectorImpl>, ParseError<'i>> {
let namespaces = Namespaces::default();
let parser = SelectorParser {
stylesheet_origin: Origin::Author,
namespaces: &namespaces,
for_supports_rule: false,
let mut input = ParserInput::new(input);
SelectorList::parse(&parser, &mut CssParser::new(&mut input), ParseRelative::No)
/// Whether we're parsing selectors in a user-agent stylesheet.
pub fn in_user_agent_stylesheet(&self) -> bool {
matches!(self.stylesheet_origin, Origin::UserAgent)
/// Whether we're parsing selectors in a stylesheet that has chrome
/// privilege.
pub fn chrome_rules_enabled(&self) -> bool {
self.url_data.chrome_rules_enabled() || self.stylesheet_origin == Origin::User
/// This enumeration determines if a pseudo-element is eagerly cascaded or not.
/// If you're implementing a public selector for `Servo` that the end-user might
/// customize, then you probably need to make it eager.
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum PseudoElementCascadeType {
/// Eagerly cascaded pseudo-elements are "normal" pseudo-elements (i.e.
/// `::before` and `::after`). They inherit styles normally as another
/// selector would do, and they're computed as part of the cascade.
/// Lazy pseudo-elements are affected by selector matching, but they're only
/// computed when needed, and not before. They're useful for general
/// pseudo-elements that are not very common.
/// Note that in Servo lazy pseudo-elements are restricted to a subset of
/// selectors, so you can't use it for public pseudo-elements. This is not
/// the case with Gecko though.
/// Precomputed pseudo-elements skip the cascade process entirely, mostly as
/// an optimisation since they are private pseudo-elements (like
/// `::-servo-details-content`).
/// This pseudo-elements are resolved on the fly using *only* global rules
/// (rules of the form `*|*`), and applying them to the parent style.
/// A per-pseudo map, from a given pseudo to a `T`.
#[derive(Clone, MallocSizeOf)]
pub struct PerPseudoElementMap<T> {
entries: [Option<T>; PSEUDO_COUNT],
impl<T> Default for PerPseudoElementMap<T> {
fn default() -> Self {
Self {
entries: PseudoElement::pseudo_none_array(),
impl<T> Debug for PerPseudoElementMap<T>
T: Debug,
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let mut first = true;
for entry in self.entries.iter() {
if !first {
f.write_str(", ")?;
first = false;
impl<T> PerPseudoElementMap<T> {
/// Get an entry in the map.
pub fn get(&self, pseudo: &PseudoElement) -> Option<&T> {
/// Clear this enumerated array.
pub fn clear(&mut self) {
*self = Self::default();
/// Set an entry value.
/// Returns an error if the element is not a simple pseudo.
pub fn set(&mut self, pseudo: &PseudoElement, value: T) {
self.entries[pseudo.index()] = Some(value);
/// Get an entry for `pseudo`, or create it with calling `f`.
pub fn get_or_insert_with<F>(&mut self, pseudo: &PseudoElement, f: F) -> &mut T
F: FnOnce() -> T,
let index = pseudo.index();
if self.entries[index].is_none() {
self.entries[index] = Some(f());
/// Get an iterator for the entries.
pub fn iter(&self) -> std::slice::Iter<Option<T>> {
/// Get a mutable iterator for the entries.
pub fn iter_mut(&mut self) -> std::slice::IterMut<Option<T>> {
/// Values for the :dir() pseudo class
/// "ltr" and "rtl" values are normalized to lowercase.
#[derive(Clone, Debug, Eq, MallocSizeOf, PartialEq, ToShmem)]
pub struct Direction(pub Atom);
/// Horizontal values for the :dir() pseudo class
#[derive(Clone, Debug, Eq, PartialEq)]
pub enum HorizontalDirection {
/// :dir(ltr)
/// :dir(rtl)
impl Direction {
/// Parse a direction value.
pub fn parse<'i, 't>(parser: &mut CssParser<'i, 't>) -> Result<Self, ParseError<'i>> {
let ident = parser.expect_ident()?;
Ok(Direction(match_ignore_ascii_case! { &ident,
"rtl" => atom!("rtl"),
"ltr" => atom!("ltr"),
_ => Atom::from(ident.as_ref()),
/// Convert this Direction into a HorizontalDirection, if applicable
pub fn as_horizontal_direction(&self) -> Option<HorizontalDirection> {
if self.0 == atom!("ltr") {
} else if self.0 == atom!("rtl") {
} else {
/// Gets the element state relevant to this :dir() selector.
pub fn element_state(&self) -> ElementState {
match self.as_horizontal_direction() {
Some(HorizontalDirection::Ltr) => ElementState::LTR,
Some(HorizontalDirection::Rtl) => ElementState::RTL,
None => ElementState::empty(),
impl ToCss for Direction {
fn to_css<W>(&self, dest: &mut CssWriter<W>) -> fmt::Result
W: Write,
serialize_atom_identifier(&self.0, dest)