style: Document Gecko's selector parser.

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Emilio Cobos Álvarez 2017-01-02 03:45:21 +01:00
parent 2778354455
commit bcac8265c9
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@ -2,6 +2,8 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//! Gecko-specific bits for selector-parsing.
use cssparser::ToCss;
use element_state::ElementState;
use selector_parser::{SelectorParser, PseudoElementCascadeType};
@ -11,11 +13,16 @@ use std::borrow::Cow;
use std::fmt;
use string_cache::{Atom, Namespace, WeakAtom, WeakNamespace};
/// NOTE: The boolean field represents whether this element is an anonymous box.
/// A representation of a CSS pseudo-element.
///
/// This is just for convenience, instead of recomputing it. Also, note that
/// Atom is always a static atom, so if space is a concern, we can use the
/// raw pointer and use the lower bit to represent it without space overhead.
/// In Gecko, we represent pseudo-elements as plain `Atom`s.
///
/// The boolean field represents whether this element is an anonymous box. This
/// is just for convenience, instead of recomputing it.
///
/// Also, note that the `Atom` member is always a static atom, so if space is a
/// concern, we can use the raw pointer and use the lower bit to represent it
/// without space overhead.
///
/// FIXME(emilio): we know all these atoms are static. Patches are starting to
/// pile up, but a further potential optimisation is generating bindings without
@ -32,16 +39,22 @@ use string_cache::{Atom, Namespace, WeakAtom, WeakNamespace};
pub struct PseudoElement(Atom, bool);
impl PseudoElement {
/// Get the pseudo-element as an atom.
#[inline]
pub fn as_atom(&self) -> &Atom {
&self.0
}
/// Whether this pseudo-element is an anonymous box.
#[inline]
fn is_anon_box(&self) -> bool {
self.1
}
/// Construct a pseudo-element from an `Atom`, receiving whether it is also
/// an anonymous box, and don't check it on release builds.
///
/// On debug builds we assert it's the result we expect.
#[inline]
pub fn from_atom_unchecked(atom: Atom, is_anon_box: bool) -> Self {
if cfg!(debug_assertions) {
@ -73,6 +86,13 @@ impl PseudoElement {
None
}
/// Constructs an atom from a string of text, and whether we're in a
/// user-agent stylesheet.
///
/// If we're not in a user-agent stylesheet, we will never parse anonymous
/// box pseudo-elements.
///
/// Returns `None` if the pseudo-element is not recognised.
#[inline]
fn from_slice(s: &str, in_ua_stylesheet: bool) -> Option<Self> {
use std::ascii::AsciiExt;
@ -102,20 +122,36 @@ impl ToCss for PseudoElement {
}
}
/// Our representation of a non tree-structural pseudo-class.
///
/// FIXME(emilio): Find a way to autogenerate this.
#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub enum NonTSPseudoClass {
/// :any-link
AnyLink,
/// :link
Link,
/// :visited
Visited,
/// :active
Active,
/// :focus
Focus,
/// :fullscreen
Fullscreen,
/// :hover
Hover,
/// :enabled
Enabled,
/// :disabled
Disabled,
/// :checked
Checked,
/// :indeterminate
Indeterminate,
/// :read-write
ReadWrite,
/// :read-only
ReadOnly,
}
@ -141,6 +177,7 @@ impl ToCss for NonTSPseudoClass {
}
impl NonTSPseudoClass {
/// Get the state flag associated with a pseudo-class, if any.
pub fn state_flag(&self) -> ElementState {
use element_state::*;
use self::NonTSPseudoClass::*;
@ -162,6 +199,7 @@ impl NonTSPseudoClass {
}
}
/// The dummy struct we use to implement our selector parsing.
#[derive(Clone, Debug, PartialEq)]
pub struct SelectorImpl;
@ -231,6 +269,13 @@ impl<'a> ::selectors::Parser for SelectorParser<'a> {
impl SelectorImpl {
#[inline]
/// Returns the kind of cascade type that a given pseudo is going to use.
///
/// In Gecko we only compute ::before and ::after eagerly. We save the rules
/// for anonymous boxes separately, so we resolve them as precomputed
/// pseudos.
///
/// We resolve the others lazily, see `Servo_ResolvePseudoStyle`.
pub fn pseudo_element_cascade_type(pseudo: &PseudoElement) -> PseudoElementCascadeType {
if Self::pseudo_is_before_or_after(pseudo) {
return PseudoElementCascadeType::Eager
@ -244,8 +289,9 @@ impl SelectorImpl {
}
#[inline]
/// Executes a function for each pseudo-element.
pub fn each_pseudo_element<F>(mut fun: F)
where F: FnMut(PseudoElement)
where F: FnMut(PseudoElement),
{
macro_rules! pseudo_element {
($pseudo_str_with_colon:expr, $atom:expr, $is_anon_box:expr) => {{
@ -257,12 +303,15 @@ impl SelectorImpl {
}
#[inline]
/// Returns whether the given pseudo-element is `::before` or `::after`.
pub fn pseudo_is_before_or_after(pseudo: &PseudoElement) -> bool {
*pseudo.as_atom() == atom!(":before") ||
*pseudo.as_atom() == atom!(":after")
}
#[inline]
/// Returns the relevant state flag for a given non-tree-structural
/// pseudo-class.
pub fn pseudo_class_state_flag(pc: &NonTSPseudoClass) -> ElementState {
pc.state_flag()
}