style: Avoid generic soup and extra reference count bumps

This makes me a bit happier about the previous patch :)

Differential Revision: https://phabricator.services.mozilla.com/D165236

components/selectors/context.rs

@@ -145,7 +145,7 @@ where
     pub pseudo_element_matching_fn: Option<&'a dyn Fn(&Impl::PseudoElement) -> bool>,
 
     /// Extra implementation-dependent matching data.
-    pub extra_data: Impl::ExtraMatchingData,
+    pub extra_data: Impl::ExtraMatchingData<'a>,
 
     quirks_mode: QuirksMode,
     needs_selector_flags: NeedsSelectorFlags,

components/selectors/parser.rs

@@ -202,7 +202,7 @@ macro_rules! with_all_bounds {
         /// are parameterized on SelectorImpl. See
         /// <https://github.com/rust-lang/rust/issues/26925>
         pub trait SelectorImpl: Clone + Debug + Sized + 'static {
-            type ExtraMatchingData: Sized + Default + 'static;
+            type ExtraMatchingData<'a>: Sized + Default;
             type AttrValue: $($InSelector)*;
             type Identifier: $($InSelector)*;
             type LocalName: $($InSelector)* + Borrow<Self::BorrowedLocalName>;
@@ -2638,7 +2638,7 @@ pub mod tests {
     }
 
     impl SelectorImpl for DummySelectorImpl {
-        type ExtraMatchingData = ();
+        type ExtraMatchingData<'a> = std::marker::PhantomData<&'a ()>;
         type AttrValue = DummyAttrValue;
         type Identifier = DummyAtom;
         type LocalName = DummyAtom;

components/style/gecko/selector_parser.rs

@@ -18,7 +18,6 @@ use cssparser::{CowRcStr, SourceLocation, ToCss, Token};
 use dom::{DocumentState, ElementState};
 use selectors::parser::SelectorParseErrorKind;
 use selectors::SelectorList;
-use servo_arc::Arc;
 use std::fmt;
 use style_traits::{CssWriter, ParseError, StyleParseErrorKind, ToCss as ToCss_};
 
@@ -236,7 +235,7 @@ pub struct SelectorImpl;
 /// A set of extra data to carry along with the matching context, either for
 /// selector-matching or invalidation.
 #[derive(Default)]
-pub struct ExtraMatchingData {
+pub struct ExtraMatchingData<'a> {
     /// The invalidation data to invalidate doc-state pseudo-classes correctly.
     pub invalidation_data: InvalidationMatchingData,
 
@@ -246,11 +245,11 @@ pub struct ExtraMatchingData {
 
     /// The style of the originating element in order to evaluate @container
     /// size queries affecting pseudo-elements.
-    pub originating_element_style: Option<Arc<ComputedValues>>,
+    pub originating_element_style: Option<&'a ComputedValues>,
 }
 
 impl ::selectors::SelectorImpl for SelectorImpl {
-    type ExtraMatchingData = ExtraMatchingData;
+    type ExtraMatchingData<'a> = ExtraMatchingData<'a>;
     type AttrValue = AtomString;
     type Identifier = AtomIdent;
     type LocalName = AtomIdent;

components/style/properties/gecko.mako.rs

@@ -103,6 +103,15 @@ impl ComputedValues {
         ).to_outer(None)
     }
 
+    /// Converts the computed values to an Arc<> from a reference.
+    pub fn to_arc(&self) -> Arc<Self> {
+        // SAFETY: We're guaranteed to be allocated as an Arc<> since the
+        // functions above are the only ones that create ComputedValues
+        // instances in Gecko (and that must be the case since ComputedValues'
+        // member is private).
+        unsafe { Arc::from_raw_addrefed(self) }
+    }
+
     #[inline]
     pub fn is_pseudo_style(&self) -> bool {
         self.0.mPseudoType != PseudoStyleType::NotPseudo
@@ -208,8 +217,8 @@ impl ComputedValuesInner {
                 &self,
                 pseudo_ty,
             );
-            // We're simulating move semantics by having C++ do a memcpy and then forgetting
+            // We're simulating move semantics by having C++ do a memcpy and
-            // it on this end.
+            // then forgetting it on this end.
             forget(self);
             UniqueArc::assume_init(arc).shareable()
         }

components/style/style_resolver.rs

@@ -507,7 +507,7 @@ where
 
     fn match_pseudo(
         &mut self,
-        originating_element_style: &Arc<ComputedValues>,
+        originating_element_style: &ComputedValues,
         pseudo_element: &PseudoElement,
         visited_handling: VisitedHandlingMode,
     ) -> Option<MatchingResults> {
@@ -544,7 +544,7 @@ where
             NeedsSelectorFlags::Yes,
         );
         matching_context.extra_data.originating_element_style =
-            Some(originating_element_style.clone());
+            Some(originating_element_style);
 
         // NB: We handle animation rules for ::before and ::after when
         // traversing them.

components/style/stylesheets/container_rule.rs

@@ -135,14 +135,14 @@ enum TraversalResult<T> {
     Done(T),
 }
 
-fn traverse_container<E, S, F, R>(
+fn traverse_container<E, F, R>(
     mut e: E,
-    originating_element_style: Option<&S>,
+    originating_element_style: Option<&ComputedValues>,
     evaluator: F,
 ) -> Option<(E, R)>
 where
     E: TElement,
-    F: Fn(E, Option<&S>) -> TraversalResult<R>,
+    F: Fn(E, Option<&ComputedValues>) -> TraversalResult<R>,
 {
     if originating_element_style.is_some() {
         match evaluator(e, originating_element_style) {
@@ -185,7 +185,7 @@ impl ContainerCondition {
     fn valid_container_info<E>(
         &self,
         potential_container: E,
-        originating_element_style: Option<&Arc<ComputedValues>>,
+        originating_element_style: Option<&ComputedValues>,
     ) -> TraversalResult<ContainerLookupResult<E>>
     where
         E: TElement,
@@ -198,7 +198,7 @@ impl ContainerCondition {
                     Some(d) => d,
                     None => return TraversalResult::InProgress,
                 };
-                data.styles.primary()
+                &**data.styles.primary()
             },
         };
         let wm = style.writing_mode;
@@ -220,7 +220,7 @@ impl ContainerCondition {
         }
 
         let size = potential_container.query_container_size(&box_style.clone_display());
-        let style = style.clone();
+        let style = style.to_arc();
         TraversalResult::Done(ContainerLookupResult {
             element: potential_container,
             info: ContainerInfo { size, wm },
@@ -232,7 +232,7 @@ impl ContainerCondition {
     pub fn find_container<E>(
         &self,
         e: E,
-        originating_element_style: Option<&Arc<ComputedValues>>,
+        originating_element_style: Option<&ComputedValues>,
     ) -> Option<ContainerLookupResult<E>>
     where
         E: TElement,
@@ -254,7 +254,7 @@ impl ContainerCondition {
         &self,
         device: &Device,
         element: E,
-        originating_element_style: Option<&Arc<ComputedValues>>,
+        originating_element_style: Option<&ComputedValues>,
         invalidation_flags: &mut ComputedValueFlags,
     ) -> KleeneValue
     where

components/style/stylist.rs

@@ -967,7 +967,7 @@ impl Stylist {
         element: E,
         pseudo: &PseudoElement,
         rule_inclusion: RuleInclusion,
-        originating_element_style: &Arc<ComputedValues>,
+        originating_element_style: &ComputedValues,
         parent_style: &Arc<ComputedValues>,
         is_probe: bool,
         matching_fn: Option<&dyn Fn(&PseudoElement) -> bool>,
@@ -1113,7 +1113,7 @@ impl Stylist {
         &self,
         guards: &StylesheetGuards,
         element: E,
-        originating_element_style: &Arc<ComputedValues>,
+        originating_element_style: &ComputedValues,
         parent_style: &Arc<ComputedValues>,
         pseudo: &PseudoElement,
         is_probe: bool,
@@ -1144,7 +1144,7 @@ impl Stylist {
 
         matching_context.pseudo_element_matching_fn = matching_fn;
         matching_context.extra_data.originating_element_style =
-            Some(originating_element_style.clone());
+            Some(originating_element_style);
 
         self.push_applicable_declarations(
             element,
@@ -1176,7 +1176,7 @@ impl Stylist {
             );
             matching_context.pseudo_element_matching_fn = matching_fn;
             matching_context.extra_data.originating_element_style =
-                Some(originating_element_style.clone());
+                Some(originating_element_style);
 
             self.push_applicable_declarations(
                 element,
@@ -2398,7 +2398,7 @@ impl CascadeData {
                 .matches(
                     stylist.device(),
                     element,
-                    context.extra_data.originating_element_style.as_ref(),
+                    context.extra_data.originating_element_style,
                     &mut context.extra_data.cascade_input_flags,
                 )
                 .to_bool(/* unknown = */ false);