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Reuse StylesheetContent for inline style sheets with identical content (#38540)

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For duplicate style sheets with identical content, `StylesheetContents`
can be reused to avoid redundant parsing of the inline style sheets.
Since duplicate stylesheets is a common case with web components, this
change will significantly improve performance. Additionally, the cache
hit rate of stylo's `CascadeDataCache` can now be significantly
improved.

When shared `StylesheetContents` is modified, copy-on-write will occur
to avoid affecting other sharers. And then updates the references to
`CssRule` or `PropertyDeclarationBlock` stored in the CSSOMs to ensure
that modifications are made only on the new copy.

Signed-off-by: sharpshooter_pt <ibluegalaxy_taoj@163.com>
This commit is contained in:
JoeDow 2025-08-20 20:31:49 +08:00 • committed by GitHub
parent f6b77f94e2
commit 6e6ef513a9
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25 changed files with 711 additions and 125 deletions
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13
components/script/dom/cssimportrule.rs
View file

@ -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 https://mozilla.org/MPL/2.0/. */
use std::cell::RefCell;
use dom_struct::dom_struct;
use servo_arc::Arc;
use style::shared_lock::{Locked, ToCssWithGuard};
@ -23,7 +25,7 @@ pub(crate) struct CSSImportRule {
cssrule: CSSRule,
#[ignore_malloc_size_of = "Arc"]
#[no_trace]
import_rule: Arc<Locked<ImportRule>>,
import_rule: RefCell<Arc<Locked<ImportRule>>>,
}
impl CSSImportRule {
@ -33,7 +35,7 @@ impl CSSImportRule {
) -> Self {
CSSImportRule {
cssrule: CSSRule::new_inherited(parent_stylesheet),
import_rule,
import_rule: RefCell::new(import_rule),
}
}
@ -50,6 +52,10 @@ impl CSSImportRule {
can_gc,
)
}
pub(crate) fn update_rule(&self, import_rule: Arc<Locked<ImportRule>>) {
*self.import_rule.borrow_mut() = import_rule;
}
}
impl SpecificCSSRule for CSSImportRule {
@ -60,6 +66,7 @@ impl SpecificCSSRule for CSSImportRule {
fn get_css(&self) -> DOMString {
let guard = self.cssrule.shared_lock().read();
self.import_rule
.borrow()
.read_with(&guard)
.to_css_string(&guard)
.into()
@ -70,7 +77,7 @@ impl CSSImportRuleMethods<crate::DomTypeHolder> for CSSImportRule {
/// <https://drafts.csswg.org/cssom-1/#dom-cssimportrule-layername>
fn GetLayerName(&self) -> Option<DOMString> {
let guard = self.cssrule.shared_lock().read();
match &self.import_rule.read_with(&guard).layer {
match &self.import_rule.borrow().read_with(&guard).layer {
ImportLayer::None => None,
ImportLayer::Anonymous => Some(DOMString::new()),
ImportLayer::Named(name) => Some(DOMString::from_string(name.to_css_string())),