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/* 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 */
use crate::properties::PropertyDeclarationBlock;
use crate::shared_lock::{Locked, SharedRwLockReadGuard};
use crate::stylesheets::StyleRule;
use servo_arc::{Arc, ArcBorrow, ArcUnion, ArcUnionBorrow};
use std::io::Write;
use std::ptr;
/// A style source for the rule node. It can either be a CSS style rule or a
/// declaration block.
/// Note that, even though the declaration block from inside the style rule
/// could be enough to implement the rule tree, keeping the whole rule provides
/// more debuggability, and also the ability of show those selectors to
/// devtools.
#[derive(Clone, Debug)]
pub struct StyleSource(ArcUnion<Locked<StyleRule>, Locked<PropertyDeclarationBlock>>);
impl PartialEq for StyleSource {
fn eq(&self, other: &Self) -> bool {
ArcUnion::ptr_eq(&self.0, &other.0)
impl StyleSource {
/// Creates a StyleSource from a StyleRule.
pub fn from_rule(rule: Arc<Locked<StyleRule>>) -> Self {
pub(super) fn key(&self) -> ptr::NonNull<()> {
/// Creates a StyleSource from a PropertyDeclarationBlock.
pub fn from_declarations(decls: Arc<Locked<PropertyDeclarationBlock>>) -> Self {
pub(super) fn dump<W: Write>(&self, guard: &SharedRwLockReadGuard, writer: &mut W) {
if let Some(ref rule) = self.0.as_first() {
let rule = rule.read_with(guard);
let _ = write!(writer, "{:?}", rule.selectors);
let _ = write!(writer, " -> {:?}",;
/// Read the style source guard, and obtain thus read access to the
/// underlying property declaration block.
pub fn read<'a>(&'a self, guard: &'a SharedRwLockReadGuard) -> &'a PropertyDeclarationBlock {
let block: &Locked<PropertyDeclarationBlock> = match self.0.borrow() {
ArcUnionBorrow::First(ref rule) => &rule.get().read_with(guard).block,
ArcUnionBorrow::Second(ref block) => block.get(),
/// Returns the style rule if applicable, otherwise None.
pub fn as_rule(&self) -> Option<ArcBorrow<Locked<StyleRule>>> {
/// Returns the declaration block if applicable, otherwise None.
pub fn as_declarations(&self) -> Option<ArcBorrow<Locked<PropertyDeclarationBlock>>> {