style: Share user agent cascade data across documents.

MozReview-Commit-ID: KcyuTHD0bt9
Signed-off-by: Emilio Cobos Álvarez <emilio@crisal.io>

components/servo_arc/lib.rs

@@ -337,7 +337,7 @@ impl<T: ?Sized> Arc<T> {
     }
 
     #[inline]
-    fn is_unique(&self) -> bool {
+    pub fn is_unique(&self) -> bool {
         // We can use Relaxed here, but the justification is a bit subtle.
         //
         // The reason to use Acquire would be to synchronize with other threads

components/style/invalidation/media_queries.rs

@@ -53,7 +53,7 @@ impl ToMediaListKey for MediaRule {}
 
 /// A struct that holds the result of a media query evaluation pass for the
 /// media queries that evaluated successfully.
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 #[cfg_attr(feature = "gecko", derive(MallocSizeOf))]
 #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
 pub struct EffectiveMediaQueryResults {

components/style/stylesheet_set.rs

@@ -31,11 +31,20 @@ where
 }
 
 /// A iterator over the stylesheets of a list of entries in the StylesheetSet.
-#[derive(Clone)]
 pub struct StylesheetCollectionIterator<'a, S>(slice::Iter<'a, StylesheetSetEntry<S>>)
 where
     S: StylesheetInDocument + PartialEq + 'static;
 
+impl<'a, S> Clone for StylesheetCollectionIterator<'a, S>
+where
+    S: StylesheetInDocument + PartialEq + 'static,
+{
+    fn clone(&self) -> Self {
+        StylesheetCollectionIterator(self.0.clone())
+    }
+}
+
+
 impl<'a, S> Iterator for StylesheetCollectionIterator<'a, S>
 where
     S: StylesheetInDocument + PartialEq + 'static,
@@ -119,11 +128,8 @@ pub struct StylesheetFlusher<'a, S>
 where
     S: StylesheetInDocument + PartialEq + 'static,
 {
-    origins_dirty: OriginSetIterator,
+    origins_dirty: OriginSet,
-    // NB: Bound to the StylesheetSet lifetime when constructed, see
+    collections: &'a mut PerOrigin<SheetCollection<S>>,
-    // StylesheetSet::flush.
-    collections: *mut PerOrigin<SheetCollection<S>>,
-    current: Option<(Origin, slice::IterMut<'a, StylesheetSetEntry<S>>)>,
     origin_data_validity: PerOrigin<OriginValidity>,
     author_style_disabled: bool,
     had_invalidations: bool,
@@ -153,9 +159,56 @@ where
         *self.origin_data_validity.borrow_for_origin(&origin)
     }
 
+    /// Whether the origin data is dirty in any way.
+    pub fn origin_dirty(&self, origin: Origin) -> bool {
+        self.origins_dirty.contains(origin.into())
+    }
+
+    /// Returns an iterator over the stylesheets of a given origin, assuming all
+    /// of them will be flushed.
+    pub fn manual_origin_sheets<'b>(&'b mut self, origin: Origin) -> StylesheetCollectionIterator<'b, S>
+    where
+        'a: 'b
+    {
+        debug_assert_eq!(origin, Origin::UserAgent);
+
+        // We could iterate over `origin_sheets(origin)` to ensure state is
+        // consistent (that the `dirty` member of the Entry is reset to
+        // `false`).
+        //
+        // In practice it doesn't matter for correctness given our use of it
+        // (that this is UA only).
+        self.collections.borrow_for_origin(&origin).iter()
+    }
+
+    /// Returns a flusher for the dirty origin `origin`.
+    pub fn origin_sheets<'b>(&'b mut self, origin: Origin) -> PerOriginFlusher<'b, S>
+    where
+        'a: 'b
+    {
+        let validity = self.origin_validity(origin);
+        let origin_dirty = self.origins_dirty.contains(origin.into());
+
+        debug_assert!(
+            origin_dirty || validity == OriginValidity::Valid,
+            "origin_data_validity should be a subset of origins_dirty!"
+        );
+
+        if self.author_style_disabled && origin == Origin::Author {
+            return PerOriginFlusher {
+                iter: [].iter_mut(),
+                validity,
+            }
+        }
+        PerOriginFlusher {
+            iter: self.collections.borrow_mut_for_origin(&origin).entries.iter_mut(),
+            validity,
+        }
+    }
+
     /// Returns whether running the whole flushing process would be a no-op.
     pub fn nothing_to_do(&self) -> bool {
-        self.origins_dirty.clone().next().is_none()
+        self.origins_dirty.is_empty()
     }
 
     /// Returns whether any DOM invalidations were processed as a result of the
@@ -165,81 +218,44 @@ where
     }
 }
 
-#[cfg(debug_assertions)]
+/// A flusher struct for a given origin, that takes care of returning the
-impl<'a, S> Drop for StylesheetFlusher<'a, S>
+/// appropriate stylesheets that need work.
+pub struct PerOriginFlusher<'a, S>
 where
-    S: StylesheetInDocument + PartialEq + 'static,
+    S: StylesheetInDocument + PartialEq + 'static
 {
-    fn drop(&mut self) {
+    iter: slice::IterMut<'a, StylesheetSetEntry<S>>,
-        debug_assert!(
+    validity: OriginValidity,
-            self.origins_dirty.next().is_none(),
-            "You're supposed to fully consume the flusher"
-        );
-    }
 }
 
-impl<'a, S> Iterator for StylesheetFlusher<'a, S>
+impl<'a, S> Iterator for PerOriginFlusher<'a, S>
 where
     S: StylesheetInDocument + PartialEq + 'static,
 {
-    type Item = (&'a S, Origin, SheetRebuildKind);
+    type Item = (&'a S, SheetRebuildKind);
 
     fn next(&mut self) -> Option<Self::Item> {
         use std::mem;
 
         loop {
-            if self.current.is_none() {
+            let potential_sheet = match self.iter.next() {
-                let next_origin = match self.origins_dirty.next() {
-                    Some(o) => o,
-                    None => return None,
-                };
-
-                // Should've been cleared already.
-                debug_assert_eq!(
-                    unsafe { &*self.collections }
-                        .borrow_for_origin(&next_origin)
-                        .data_validity,
-                    OriginValidity::Valid
-                );
-
-                self.current =
-                    Some((
-                        next_origin,
-                        unsafe { &mut *self.collections }
-                            .borrow_mut_for_origin(&next_origin)
-                            .entries
-                            .iter_mut()
-                    ));
-            }
-
-            let potential_sheet = match self.current.as_mut().unwrap().1.next() {
                 Some(s) => s,
-                None => {
+                None => return None,
-                    self.current = None;
-                    continue;
-                }
             };
 
-            let origin = self.current.as_ref().unwrap().0;
-
             let dirty = mem::replace(&mut potential_sheet.dirty, false);
-
             if dirty {
                 // If the sheet was dirty, we need to do a full rebuild anyway.
-                return Some((&potential_sheet.sheet, origin, SheetRebuildKind::Full))
+                return Some((&potential_sheet.sheet, SheetRebuildKind::Full))
             }
 
-            if self.author_style_disabled && matches!(origin, Origin::Author) {
+            let rebuild_kind = match self.validity {
-                continue;
-            }
-
-            let rebuild_kind = match self.origin_validity(origin) {
                 OriginValidity::Valid => continue,
                 OriginValidity::CascadeInvalid => SheetRebuildKind::CascadeOnly,
                 OriginValidity::FullyInvalid => SheetRebuildKind::Full,
             };
 
-            return Some((&potential_sheet.sheet, origin, rebuild_kind));
+            return Some((&potential_sheet.sheet, rebuild_kind));
         }
     }
 }
@@ -501,10 +517,10 @@ where
 
         let had_invalidations = self.invalidations.flush(document_element);
         let origins_dirty =
-            mem::replace(&mut self.origins_dirty, OriginSet::empty()).iter();
+            mem::replace(&mut self.origins_dirty, OriginSet::empty());
 
         let mut origin_data_validity = PerOrigin::<OriginValidity>::default();
-        for origin in origins_dirty.clone() {
+        for origin in origins_dirty.iter() {
             let collection = self.collections.borrow_mut_for_origin(&origin);
             *origin_data_validity.borrow_mut_for_origin(&origin) =
                 mem::replace(&mut collection.data_validity, OriginValidity::Valid);
@@ -516,7 +532,6 @@ where
             had_invalidations,
             origins_dirty,
             origin_data_validity,
-            current: None,
         }
     }
 

components/style/stylist.rs

@@ -40,6 +40,7 @@ use smallbitvec::SmallBitVec;
 use smallvec::VecLike;
 use std::fmt::Debug;
 use std::ops;
+use std::sync::Mutex;
 use style_traits::viewport::ViewportConstraints;
 use stylesheet_set::{OriginValidity, SheetRebuildKind, StylesheetSet, StylesheetFlusher};
 #[cfg(feature = "gecko")]
@@ -61,15 +62,83 @@ pub type StylistSheet = ::stylesheets::DocumentStyleSheet;
 #[cfg(feature = "gecko")]
 pub type StylistSheet = ::gecko::data::GeckoStyleSheet;
 
+/// A cache of computed user-agent data, to be shared across documents.
+lazy_static! {
+    static ref UA_CASCADE_DATA_CACHE: Mutex<UserAgentCascadeDataCache> =
+        Mutex::new(UserAgentCascadeDataCache::new());
+}
+
+struct UserAgentCascadeDataCache {
+    entries: Vec<Arc<UserAgentCascadeData>>,
+}
+
+impl UserAgentCascadeDataCache {
+    fn new() -> Self {
+        Self {
+            entries: vec![],
+        }
+    }
+
+    fn lookup<'a, I, S>(
+        &'a mut self,
+        sheets: I,
+        device: &Device,
+        quirks_mode: QuirksMode,
+        guard: &SharedRwLockReadGuard,
+    ) -> Result<Arc<UserAgentCascadeData>, FailedAllocationError>
+    where
+        I: Iterator<Item = &'a S> + Clone,
+        S: StylesheetInDocument + ToMediaListKey + PartialEq + 'static,
+    {
+        let mut key = EffectiveMediaQueryResults::new();
+        for sheet in sheets.clone() {
+            CascadeData::collect_applicable_media_query_results_into(
+                device,
+                sheet,
+                guard,
+                &mut key,
+            )
+        }
+
+        for entry in &self.entries {
+            if entry.cascade_data.effective_media_query_results == key {
+                return Ok(entry.clone());
+            }
+        }
+
+        let mut new_data = UserAgentCascadeData {
+            cascade_data: CascadeData::new(),
+            precomputed_pseudo_element_decls: PrecomputedPseudoElementDeclarations::default(),
+        };
+
+        for sheet in sheets {
+            new_data.cascade_data.add_stylesheet(
+                device,
+                quirks_mode,
+                sheet,
+                guard,
+                SheetRebuildKind::Full,
+                Some(&mut new_data.precomputed_pseudo_element_decls),
+            )?;
+        }
+
+        let new_data = Arc::new(new_data);
+
+        self.entries.push(new_data.clone());
+        Ok(new_data)
+    }
+
+    fn expire_unused(&mut self) {
+        self.entries.retain(|e| !e.is_unique())
+    }
+}
+
 type PrecomputedPseudoElementDeclarations =
     PerPseudoElementMap<Vec<ApplicableDeclarationBlock>>;
 
-/// All the computed information for a stylesheet.
 #[derive(Default)]
-#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+struct UserAgentCascadeData {
-struct DocumentCascadeData {
+    cascade_data: CascadeData,
-    /// Common data for all the origins.
-    per_origin: PerOrigin<CascadeData>,
 
     /// Applicable declarations for a given non-eagerly cascaded pseudo-element.
     ///
@@ -77,18 +146,98 @@ struct DocumentCascadeData {
     /// computed values on the fly on layout.
     ///
     /// These are only filled from UA stylesheets.
-    ///
-    /// FIXME(emilio): Use the rule tree!
     precomputed_pseudo_element_decls: PrecomputedPseudoElementDeclarations,
 }
 
+/// All the computed information for a stylesheet.
+#[derive(Default)]
+#[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+struct DocumentCascadeData {
+    #[cfg_attr(
+        feature = "servo",
+        ignore_heap_size_of = "Arc, owned by UserAgentCascadeDataCache"
+    )]
+    user_agent: Arc<UserAgentCascadeData>,
+    user: CascadeData,
+    author: CascadeData,
+    per_origin: PerOrigin<()>,
+}
+
+struct DocumentCascadeDataIter<'a> {
+    iter: PerOriginIter<'a, ()>,
+    cascade_data: &'a DocumentCascadeData,
+}
+
+impl<'a> Iterator for DocumentCascadeDataIter<'a> {
+    type Item = (&'a CascadeData, Origin);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let (_, origin) = match self.iter.next() {
+            Some(o) => o,
+            None => return None,
+        };
+
+        Some((self.cascade_data.borrow_for_origin(origin), origin))
+    }
+}
+
 impl DocumentCascadeData {
-    fn iter_origins(&self) -> PerOriginIter<CascadeData> {
+    fn borrow_for_origin(&self, origin: Origin) -> &CascadeData {
-        self.per_origin.iter_origins()
+        match origin {
+            Origin::UserAgent => &self.user_agent.cascade_data,
+            Origin::Author => &self.author,
+            Origin::User => &self.user,
+        }
     }
 
-    fn iter_origins_rev(&self) -> PerOriginIter<CascadeData> {
+    fn iter_origins(&self) -> DocumentCascadeDataIter {
-        self.per_origin.iter_origins_rev()
+        DocumentCascadeDataIter {
+            iter: self.per_origin.iter_origins(),
+            cascade_data: self,
+        }
+    }
+
+    fn iter_origins_rev(&self) -> DocumentCascadeDataIter {
+        DocumentCascadeDataIter {
+            iter: self.per_origin.iter_origins_rev(),
+            cascade_data: self,
+        }
+    }
+
+    fn rebuild_origin<'a, S>(
+        device: &Device,
+        quirks_mode: QuirksMode,
+        flusher: &mut StylesheetFlusher<'a, S>,
+        guards: &StylesheetGuards,
+        origin: Origin,
+        cascade_data: &mut CascadeData,
+    ) -> Result<(), FailedAllocationError>
+    where
+        S: StylesheetInDocument + ToMediaListKey + PartialEq + 'static,
+    {
+        debug_assert_ne!(origin, Origin::UserAgent);
+
+        let validity = flusher.origin_validity(origin);
+
+        match validity {
+            OriginValidity::Valid => {},
+            OriginValidity::CascadeInvalid => cascade_data.clear_cascade_data(),
+            OriginValidity::FullyInvalid => cascade_data.clear(),
+        }
+
+        let guard = guards.for_origin(origin);
+        for (stylesheet, rebuild_kind) in flusher.origin_sheets(origin) {
+            cascade_data.add_stylesheet(
+                device,
+                quirks_mode,
+                stylesheet,
+                guard,
+                rebuild_kind,
+                /* precomputed_pseudo_element_decls = */ None,
+            )?;
+        }
+
+        Ok(())
     }
 
     /// Rebuild the cascade data for the given document stylesheets, and
@@ -98,7 +247,7 @@ impl DocumentCascadeData {
         &mut self,
         device: &Device,
         quirks_mode: QuirksMode,
-        flusher: StylesheetFlusher<'a, S>,
+        mut flusher: StylesheetFlusher<'a, S>,
         guards: &StylesheetGuards,
     ) -> Result<(), FailedAllocationError>
     where
@@ -106,55 +255,56 @@ impl DocumentCascadeData {
     {
         debug_assert!(!flusher.nothing_to_do());
 
-        for (cascade_data, origin) in self.per_origin.iter_mut_origins() {
+        // First do UA sheets.
-            let validity = flusher.origin_validity(origin);
+        {
+            if flusher.origin_dirty(Origin::UserAgent) {
+                let mut ua_cache = UA_CASCADE_DATA_CACHE.lock().unwrap();
+                let origin_sheets =
+                    flusher.manual_origin_sheets(Origin::UserAgent);
 
-            if validity == OriginValidity::Valid {
+                let ua_cascade_data = ua_cache.lookup(
-                continue;
+                    origin_sheets,
-            }
-
-            if origin == Origin::UserAgent {
-                self.precomputed_pseudo_element_decls.clear();
-            }
-
-            if validity == OriginValidity::CascadeInvalid {
-                cascade_data.clear_cascade_data()
-            } else {
-                debug_assert_eq!(validity, OriginValidity::FullyInvalid);
-                cascade_data.clear();
-            }
-        }
-
-        for (stylesheet, origin, rebuild_kind) in flusher {
-            let guard = guards.for_origin(origin);
-            let origin = stylesheet.origin(guard);
-            self.per_origin
-                .borrow_mut_for_origin(&origin)
-                .add_stylesheet(
                     device,
                     quirks_mode,
-                    stylesheet,
+                    guards.ua_or_user
-                    guard,
-                    rebuild_kind,
-                    &mut self.precomputed_pseudo_element_decls,
                 )?;
+
+                ua_cache.expire_unused();
+                self.user_agent = ua_cascade_data;
+            }
         }
 
+        // Now do the user sheets.
+        Self::rebuild_origin(
+            device,
+            quirks_mode,
+            &mut flusher,
+            guards,
+            Origin::User,
+            &mut self.user,
+        )?;
+
+        // And now the author sheets.
+        Self::rebuild_origin(
+            device,
+            quirks_mode,
+            &mut flusher,
+            guards,
+            Origin::Author,
+            &mut self.author,
+        )?;
+
         Ok(())
     }
 
     /// Measures heap usage.
     #[cfg(feature = "gecko")]
     pub fn add_size_of_children(&self, ops: &mut MallocSizeOfOps, sizes: &mut ServoStyleSetSizes) {
-        self.per_origin.user_agent.add_size_of_children(ops, sizes);
+        self.user.add_size_of_children(ops, sizes);
-        self.per_origin.user.add_size_of_children(ops, sizes);
+        self.author.add_size_of_children(ops, sizes);
-        self.per_origin.author.add_size_of_children(ops, sizes);
 
-        for elem in self.precomputed_pseudo_element_decls.iter() {
+        // FIXME(emilio): UA_CASCADE_DATA_CACHE is shared, we should do whatever
-            if let Some(ref elem) = *elem {
+        // we do for RuleProcessorCache in Gecko.
-                sizes.mStylistPrecomputedPseudos += elem.shallow_size_of(ops);
-            }
-        }
     }
 }
 
@@ -556,7 +706,7 @@ impl Stylist {
         extra_declarations: Option<Vec<ApplicableDeclarationBlock>>,
     ) -> StrongRuleNode {
         let mut decl;
-        let declarations = match self.cascade_data.precomputed_pseudo_element_decls.get(pseudo) {
+        let declarations = match self.cascade_data.user_agent.precomputed_pseudo_element_decls.get(pseudo) {
             Some(declarations) => {
                 match extra_declarations {
                     Some(mut extra_decls) => {
@@ -975,7 +1125,7 @@ impl Stylist {
 
             let guard = guards.for_origin(origin);
             let origin_cascade_data =
-                self.cascade_data.per_origin.borrow_for_origin(&origin);
+                self.cascade_data.borrow_for_origin(origin);
 
             let affected_changed = !origin_cascade_data.media_feature_affected_matches(
                 stylesheet,
@@ -1034,7 +1184,7 @@ impl Stylist {
 
         // nsXBLPrototypeResources::LoadResources() loads Chrome XBL style
         // sheets under eAuthorSheetFeatures level.
-        if let Some(map) = self.cascade_data.per_origin.author.borrow_for_pseudo(pseudo_element) {
+        if let Some(map) = self.cascade_data.author.borrow_for_pseudo(pseudo_element) {
             map.get_all_matching_rules(
                 element,
                 &rule_hash_target,
@@ -1082,7 +1232,7 @@ impl Stylist {
         let only_default_rules = rule_inclusion == RuleInclusion::DefaultOnly;
 
         // Step 1: Normal user-agent rules.
-        if let Some(map) = self.cascade_data.per_origin.user_agent.borrow_for_pseudo(pseudo_element) {
+        if let Some(map) = self.cascade_data.user_agent.cascade_data.borrow_for_pseudo(pseudo_element) {
             map.get_all_matching_rules(
                 element,
                 &rule_hash_target,
@@ -1120,7 +1270,7 @@ impl Stylist {
         // Which may be more what you would probably expect.
         if rule_hash_target.matches_user_and_author_rules() {
             // Step 3a: User normal rules.
-            if let Some(map) = self.cascade_data.per_origin.user.borrow_for_pseudo(pseudo_element) {
+            if let Some(map) = self.cascade_data.user.borrow_for_pseudo(pseudo_element) {
                 map.get_all_matching_rules(
                     element,
                     &rule_hash_target,
@@ -1147,7 +1297,7 @@ impl Stylist {
             // See nsStyleSet::FileRules().
             if !cut_off_inheritance {
                 // Step 3c: Author normal rules.
-                if let Some(map) = self.cascade_data.per_origin.author.borrow_for_pseudo(pseudo_element) {
+                if let Some(map) = self.cascade_data.author.borrow_for_pseudo(pseudo_element) {
                     map.get_all_matching_rules(
                         element,
                         &rule_hash_target,
@@ -1380,6 +1530,8 @@ pub struct ExtraStyleData {
 // nsCSSFontFaceRules or nsCSSCounterStyleRules OMT (which we don't).
 #[cfg(feature = "gecko")]
 unsafe impl Sync for ExtraStyleData {}
+#[cfg(feature = "gecko")]
+unsafe impl Send for ExtraStyleData {}
 
 #[cfg(feature = "gecko")]
 impl ExtraStyleData {
@@ -1422,7 +1574,7 @@ impl ExtraStyleData {
 }
 
 /// An iterator over the different ExtraStyleData.
-pub struct ExtraStyleDataIterator<'a>(PerOriginIter<'a, CascadeData>);
+pub struct ExtraStyleDataIterator<'a>(DocumentCascadeDataIter<'a>);
 
 impl<'a> Iterator for ExtraStyleDataIterator<'a> {
     type Item = (&'a ExtraStyleData, Origin);
@@ -1712,6 +1864,45 @@ impl CascadeData {
         }
     }
 
+    /// Collects all the applicable media query results into `results`.
+    ///
+    /// This duplicates part of the logic in `add_stylesheet`, which is
+    /// a bit unfortunate.
+    ///
+    /// FIXME(emilio): With a bit of smartness in
+    /// `media_feature_affected_matches`, we could convert
+    /// `EffectiveMediaQueryResults` into a vector without too much effort.
+    fn collect_applicable_media_query_results_into<S>(
+        device: &Device,
+        stylesheet: &S,
+        guard: &SharedRwLockReadGuard,
+        results: &mut EffectiveMediaQueryResults,
+    )
+    where
+        S: StylesheetInDocument + ToMediaListKey + 'static,
+    {
+        if !stylesheet.enabled() ||
+           !stylesheet.is_effective_for_device(device, guard) {
+           return;
+        }
+
+        results.saw_effective(stylesheet);
+
+        for rule in stylesheet.effective_rules(device, guard) {
+            match *rule {
+                CssRule::Import(ref lock) => {
+                    let import_rule = lock.read_with(guard);
+                    results.saw_effective(import_rule);
+                }
+                CssRule::Media(ref lock) => {
+                    let media_rule = lock.read_with(guard);
+                    results.saw_effective(media_rule);
+                }
+                _ => {},
+            }
+        }
+    }
+
     // Returns Err(..) to signify OOM
     fn add_stylesheet<S>(
         &mut self,
@@ -1720,7 +1911,7 @@ impl CascadeData {
         stylesheet: &S,
         guard: &SharedRwLockReadGuard,
         rebuild_kind: SheetRebuildKind,
-        precomputed_pseudo_element_decls: &mut PrecomputedPseudoElementDeclarations,
+        mut precomputed_pseudo_element_decls: Option<&mut PrecomputedPseudoElementDeclarations>,
     ) -> Result<(), FailedAllocationError>
     where
         S: StylesheetInDocument + ToMediaListKey + 'static,
@@ -1756,6 +1947,8 @@ impl CascadeData {
                                 }
 
                                 precomputed_pseudo_element_decls
+                                    .as_mut()
+                                    .expect("Expected precomputed declarations for the UA level")
                                     .get_or_insert_with(&pseudo.canonical(), Vec::new)
                                     .expect("Unexpected tree pseudo-element?")
                                     .push(ApplicableDeclarationBlock::new(