/* 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/. */
//! A [`@scope`][scope] rule.
//!
//! [scope]:
https://drafts.csswg.org/css-cascade-6/#scoped-styles
use crate::applicable_declarations::ScopeProximity;
use crate::dom::TElement;
use crate::parser::ParserContext;
use crate::selector_parser::{SelectorImpl, SelectorParser};
use crate::shared_lock::{
DeepCloneWithLock, Locked, SharedRwLock, SharedRwLockReadGuard, ToCssWithGuard,
};
use crate::str::CssStringWriter;
use crate::stylesheets::CssRules;
use crate::simple_buckets_map::SimpleBucketsMap;
use cssparser::{Parser, SourceLocation, ToCss};
#[cfg(feature = "gecko")]
use malloc_size_of::{
MallocSizeOfOps, MallocUnconditionalShallowSizeOf, MallocUnconditionalSizeOf,
};
use selectors::context::{MatchingContext, QuirksMode};
use selectors::matching::matches_selector;
use selectors::parser::{Component, ParseRelative, Selector, SelectorList};
use selectors::OpaqueElement;
use servo_arc::Arc;
use std::fmt::{self, Write};
use style_traits::{CssWriter, ParseError};
/// A scoped rule.
#[derive(Debug, ToShmem)]
pub struct ScopeRule {
/// Bounds at which this rule applies.
pub bounds: ScopeBounds,
/// The nested rules inside the block.
pub rules: Arc<Locked<CssRules>>,
/// The source position where this rule was found.
pub source_location: SourceLocation,
}
impl DeepCloneWithLock for ScopeRule {
fn deep_clone_with_lock(
&self,
lock: &SharedRwLock,
guard: &SharedRwLockReadGuard,
) -> Self {
let rules = self.rules.read_with(guard);
Self {
bounds: self.bounds.clone(),
rules: Arc::new(lock.wrap(rules.deep_clone_with_lock(lock, guard))),
source_location: self.source_location.clone(),
}
}
}
impl ToCssWithGuard for ScopeRule {
fn to_css(&self, guard: &SharedRwLockReadGuard, dest: &mut CssStringWriter) -> fmt::Result {
dest.write_str("@scope")?;
{
let mut writer = CssWriter::new(dest);
if let Some(start) = self.bounds.start.as_ref() {
writer.write_str(" (")?;
start.to_css(&mut writer)?;
writer.write_char(')')?;
}
if let Some(end) = self.bounds.end.as_ref() {
writer.write_str(" to (")?;
end.to_css(&mut writer)?;
writer.write_char(')')?;
}
}
self.rules.read_with(guard).to_css_block(guard, dest)
}
}
impl ScopeRule {
/// Measure heap usage.
#[cfg(feature = "gecko")]
pub fn size_of(&self, guard: &SharedRwLockReadGuard, ops: &mut MallocSizeOfOps) -> usize {
self.rules.unconditional_shallow_size_of(ops) +
self.rules.read_with(guard).size_of(guard, ops) +
self.bounds.size_of(ops)
}
}
/// Bounds of the scope.
#[derive(Debug, Clone, ToShmem)]
pub struct ScopeBounds {
/// Start of the scope.
pub start: Option<SelectorList<SelectorImpl>>,
/// End of the scope.
pub end: Option<SelectorList<SelectorImpl>>,
}
impl ScopeBounds {
#[cfg(feature = "gecko")]
fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize {
fn bound_size_of(
bound: &Option<SelectorList<SelectorImpl>>,
ops: &mut MallocSizeOfOps,
) -> usize {
bound
.as_ref()
.map(|list| list.unconditional_size_of(ops))
.unwrap_or(0)
}
bound_size_of(&self.start, ops) + bound_size_of(&self.end, ops)
}
}
fn parse_scope<'a>(
context: &ParserContext,
input: &mut Parser<'a, '_>,
parse_relative: ParseRelative,
for_end: bool,
) -> Result<Option<SelectorList<SelectorImpl>>, ParseError<'a>> {
input
.try_parse(|input| {
if for_end {
// scope-end not existing is valid.
if input.try_parse(|i| i.expect_ident_matching("to")).is_err() {
return Ok(None);
}
}
let parens = input.try_parse(|i| i.expect_parenthesis_block());
if for_end {
// `@scope to {}` is NOT valid.
parens?;
} else if parens.is_err() {
// `@scope {}` is valid.
return Ok(None);
}
input.parse_nested_block(|input| {
if input.is_exhausted() {
// `@scope () {}` is valid.
return Ok(None);
}
let selector_parser = SelectorParser {
stylesheet_origin: context.stylesheet_origin,
namespaces: &context.namespaces,
url_data: context.url_data,
for_supports_rule: false,
};
let parse_relative = if for_end {
ParseRelative::ForScope
} else {
parse_relative
};
Ok(Some(SelectorList::parse_disallow_pseudo(
&selector_parser,
input,
parse_relative,
)?))
})
})
}
impl ScopeBounds {
/// Parse a container condition.
pub fn parse<'a>(
context: &ParserContext,
input: &mut Parser<'a, '_>,
parse_relative: ParseRelative,
) -> Result<Self, ParseError<'a>> {
let start = parse_scope(context, input, parse_relative, false)?;
let end = parse_scope(context, input, parse_relative, true)?;
Ok(Self { start, end })
}
}
/// Types of implicit scope root.
#[derive(Debug, Copy, Clone, MallocSizeOf)]
pub enum ImplicitScopeRoot {
/// This implicit scope root is in the light tree.
InLightTree(OpaqueElement),
/// This implicit scope root is the document element, regardless of which (light|shadow) tree
/// the element being matched is. This is the case for e.g. if you specified an implicit scope
/// within a user stylesheet.
DocumentElement,
/// The implicit scope root is in a constructed stylesheet - the scope root the element
/// under consideration's shadow root (If one exists).
Constructed,
/// This implicit scope root is in the shadow tree.
InShadowTree(OpaqueElement),
/// This implicit scope root is the shadow host of the stylesheet-containing shadow tree.
ShadowHost(OpaqueElement),
}
impl ImplicitScopeRoot {
/// Return true if this matches the shadow host.
pub fn matches_shadow_host(&self) -> bool {
match self {
Self::InLightTree(..) | Self::InShadowTree(..) | Self::DocumentElement => false,
Self::ShadowHost(..) | Self::Constructed => true,
}
}
/// Return the implicit scope root element.
pub fn element(&self, current_host: Option<OpaqueElement>) -> ImplicitScopeTarget {
match self {
Self::InLightTree(e) | Self::InShadowTree(e) | Self::ShadowHost(e) => {
ImplicitScopeTarget::Element(*e)
},
Self::Constructed | Self::DocumentElement => {
if matches!(self, Self::Constructed) {
if let Some(host) = current_host {
return ImplicitScopeTarget::Element(host);
}
}
ImplicitScopeTarget::DocumentElement
},
}
}
}
/// Target of this implicit scope.
pub enum ImplicitScopeTarget {
/// Target matches only the specified element.
Element(OpaqueElement),
/// Implicit scope whose target is the document element.
DocumentElement,
}
impl ImplicitScopeTarget {
/// Check if this element is the implicit scope.
fn check<E: TElement>(&self, element: E) -> bool {
match self {
Self::Element(e) => element.opaque() == *e,
Self::DocumentElement => element.is_root(),
}
}
}
/// Target of this scope.
pub enum ScopeTarget<'a> {
/// Target matches an element matching the specified selector list.
Selector(&'a SelectorList<SelectorImpl>),
/// Target matches an implicit scope target.
Implicit(ImplicitScopeTarget),
}
impl<'a> ScopeTarget<'a> {
/// Check if the given element is the scope.
fn check<E: TElement>(
&self,
element: E,
scope: Option<OpaqueElement>,
scope_subject_map: &ScopeSubjectMap,
context: &mut MatchingContext<E::Impl>,
) -> bool {
match self {
Self::Selector(list) => context.nest_for_scope_condition(scope, |context| {
if scope_subject_map.early_reject(element, context.quirks_mode()) {
return false;
}
for selector in list.slice().iter() {
if matches_selector(selector, 0, None, &element, context) {
return true;
}
}
false
}),
Self::Implicit(t) => t.check(element),
}
}
}
/// A scope root candidate.
#[derive(Clone, Copy, Debug)]
pub struct ScopeRootCandidate {
/// This candidate's scope root.
pub root: OpaqueElement,
/// Ancestor hop from the element under consideration to this scope root.
pub proximity: ScopeProximity,
}
/// Collect potential scope roots for a given element and its scope target.
/// The check may not pass the ceiling, if specified.
pub fn collect_scope_roots<E>(
element: E,
ceiling: Option<OpaqueElement>,
context: &mut MatchingContext<E::Impl>,
target: &ScopeTarget,
matches_shadow_host: bool,
scope_subject_map: &ScopeSubjectMap,
) -> Vec<ScopeRootCandidate>
where
E: TElement,
{
let mut result = vec![];
let mut parent = Some(element);
let mut proximity = 0usize;
while let Some(p) = parent {
if ceiling == Some(p.opaque()) {
break;
}
if target.check(p, ceiling, scope_subject_map, context) {
result.push(ScopeRootCandidate {
root: p.opaque(),
proximity: ScopeProximity::new(proximity),
});
// Note that we can't really break here - we need to consider
// ALL scope roots to figure out whch one didn't end.
}
parent = p.parent_element();
proximity += 1;
// We we got to the top of the shadow tree - keep going
// if we may match the shadow host.
if parent.is_none() && matches_shadow_host {
parent = p.containing_shadow_host();
}
}
result
}
/// Given the scope-end selector, check if the element is outside of the scope.
/// That is, check if any ancestor to the root matches the scope-end selector.
pub fn element_is_outside_of_scope<E>(
selector: &Selector<E::Impl>,
element: E,
root: OpaqueElement,
context: &mut MatchingContext<E::Impl>,
root_may_be_shadow_host: bool,
) -> bool
where
E: TElement,
{
let mut parent = Some(element);
context.nest_for_scope_condition(Some(root), |context| {
while let Some(p) = parent {
if matches_selector(selector, 0, None, &p, context) {
return true;
}
if p.opaque() == root {
// Reached the top, not lying outside of scope.
break;
}
parent = p.parent_element();
if parent.is_none() && root_may_be_shadow_host {
if let Some(host) = p.containing_shadow_host() {
// Pretty much an edge case where user specified scope-start and -end of :host
return host.opaque() == root;
}
}
}
return false;
})
}
/// A map containing simple selectors in subjects of scope selectors.
/// This allows fast-rejecting scopes before running the full match.
#[derive(Clone, Debug, Default, MallocSizeOf)]
pub struct ScopeSubjectMap {
buckets: SimpleBucketsMap<()>,
any: bool,
}
impl ScopeSubjectMap {
/// Add the `<scope-start>` of a scope.
pub fn add_bound_start(&mut self, selectors: &SelectorList<SelectorImpl>, quirks_mode: QuirksMode)
{
if self.add_selector_list(selectors, quirks_mode) {
self.any = true;
}
}
fn add_selector_list(&mut self, selectors: &SelectorList<SelectorImpl>, quirks_mode: QuirksMode) -> bool {
let mut is_any = false;
for selector in selectors.slice().iter() {
is_any = is_any || self.add_selector(selector, quirks_mode);
}
is_any
}
fn add_selector(&mut self, selector: &Selector<SelectorImpl>, quirks_mode: QuirksMode) -> bool {
let mut is_any = true;
let mut iter = selector.iter();
while let Some(c) = iter.next() {
let component_any = match c {
Component::Class(cls) => {
match self.buckets.classes.try_entry(cls.0.clone(), quirks_mode) {
Ok(e) => {
e.or_insert(());
false
},
Err(_) => true,
}
},
Component::ID(id) => {
match self.buckets.ids.try_entry(id.0.clone(), quirks_mode) {
Ok(e) => {
e.or_insert(());
false
},
Err(_) => true,
}
},
Component::LocalName(local_name) => {
self.buckets.local_names.insert(local_name.lower_name.clone(), ());
false
},
Component::Is(ref list) | Component::Where(ref list) => {
self.add_selector_list(list, quirks_mode)
},
_ => true,
};
is_any = is_any && component_any;
}
is_any
}
/// Shrink the map as much as possible.
pub fn shrink_if_needed(&mut self) {
self.buckets.shrink_if_needed();
}
/// Clear the map.
pub fn clear(&mut self) {
self.buckets.clear();
self.any = false;
}
/// Could a given element possibly be a scope root?
fn early_reject<E: TElement>(&self, element: E, quirks_mode: QuirksMode) -> bool {
if self.any {
return false;
}
if let Some(id) = element.id() {
if self.buckets.ids.get(id, quirks_mode).is_some() {
return false;
}
}
let mut found = false;
element.each_class(|cls| {
if self.buckets.classes.get(cls, quirks_mode).is_some() {
found = true;
}
});
if found {
return false;
}
if self.buckets.local_names.get(element.local_name()).is_some() {
return false;
}
true
}
}
/// Determine if this selector list, when used as a scope bound selector, is considered trivial.
pub fn scope_selector_list_is_trivial(list: &SelectorList<SelectorImpl>) -> bool {
fn scope_selector_is_trivial(selector: &Selector<SelectorImpl>) -> bool {
// A selector is trivial if:
// * There is no selector conditional on its siblings and/or descendant to match, and
// * There is no dependency on sibling relations, and
// * There's no ID selector in the selector. A more correct approach may be to ensure that
// scoping roots of the style sharing candidates and targets have matching IDs, but that
// requires re-plumbing what we pass around for scope roots.
let mut iter = selector.iter();
loop {
while let Some(c) = iter.next() {
match c {
Component::ID(_) | Component::Nth(_) | Component::NthOf(_) | Component::Has(_) => return false,
Component::Is(ref list) | Component::Where(ref list) | Component::Negation(ref list) =>
if !scope_selector_list_is_trivial(list) {
return false;
}
_ => (),
}
}
match iter.next_sequence() {
Some(c) => if c.is_sibling() {
return false;
},
None => return true,
}
}
}
list.slice().iter().all(|s| scope_selector_is_trivial(s))
}
