style: Make style sharing look at XBL / Shadow DOM rules.

Bug: 1412251
Reviewed-by: bz
MozReview-Commit-ID: II6lk6OmSZU

5 files changed, 148 insertions, 47 deletions

diff --git a/components/style/dom.rs b/components/style/dom.rs
index c58433fe377..4f2ef48b1ae 100644
--- a/components/style/dom.rs
+++ b/components/style/dom.rs
@@ -388,6 +388,15 @@ pub trait TElement
         depth
     }
 
+    /// The style scope of this element is a node that represents which rules
+    /// apply to the element.
+    ///
+    /// In Servo, where we don't know about Shadow DOM or XBL, the style scope
+    /// is always the document.
+    fn style_scope(&self) -> Self::ConcreteNode {
+        self.as_node().owner_doc().as_node()
+    }
+
     /// Get this node's parent element from the perspective of a restyle
     /// traversal.
     fn traversal_parent(&self) -> Option<Self> {
@@ -738,14 +747,16 @@ pub trait TElement
         None
     }
 
-    /// Returns the rule hash target given an element.
+    /// Return the element which we can use to look up rules in the selector
+    /// maps.
+    ///
+    /// This is always the element itself, except in the case where we are an
+    /// element-backed pseudo-element, in which case we return the originating
+    /// element.
     fn rule_hash_target(&self) -> Self {
         let is_implemented_pseudo =
             self.implemented_pseudo_element().is_some();
 
-        // NB: This causes use to rule has pseudo selectors based on the
-        // properties of the originating element (which is fine, given the
-        // find_first_from_right usage).
         if is_implemented_pseudo {
             self.closest_non_native_anonymous_ancestor().unwrap()
         } else {
diff --git a/components/style/gecko/wrapper.rs b/components/style/gecko/wrapper.rs
index c10cb3875b9..7b76a355a71 100644
--- a/components/style/gecko/wrapper.rs
+++ b/components/style/gecko/wrapper.rs
@@ -519,8 +519,13 @@ impl<'le> GeckoElement<'le> {
     }
 
     #[inline]
+    fn may_be_in_binding_manager(&self) -> bool {
+        self.flags() & (structs::NODE_MAY_BE_IN_BINDING_MNGR as u32) != 0
+    }
+
+    #[inline]
     fn get_xbl_binding(&self) -> Option<GeckoXBLBinding<'le>> {
-        if self.flags() & (structs::NODE_MAY_BE_IN_BINDING_MNGR as u32) == 0 {
+        if !self.may_be_in_binding_manager() {
             return None;
         }
 
@@ -553,9 +558,11 @@ impl<'le> GeckoElement<'le> {
         } else {
             let binding_parent = unsafe {
                 self.get_non_xul_xbl_binding_parent_raw_content().as_ref()
-            }.map(GeckoNode::from_content)
-                .and_then(|n| n.as_element());
-            debug_assert!(binding_parent == unsafe { bindings::Gecko_GetBindingParent(self.0).map(GeckoElement) });
+            }.map(GeckoNode::from_content).and_then(|n| n.as_element());
+
+            debug_assert!(binding_parent == unsafe {
+                bindings::Gecko_GetBindingParent(self.0).map(GeckoElement)
+            });
             binding_parent
         }
     }
@@ -925,6 +932,28 @@ impl<'le> TElement for GeckoElement<'le> {
         self.get_before_or_after_pseudo(/* is_before = */ false)
     }
 
+    /// Ensure this accurately represents the rules that an element may ever
+    /// match, even in the native anonymous content case.
+    fn style_scope(&self) -> Self::ConcreteNode {
+        if self.implemented_pseudo_element().is_some() {
+            return self.closest_non_native_anonymous_ancestor().unwrap().style_scope();
+        }
+
+        if self.is_in_native_anonymous_subtree() {
+            return self.as_node().owner_doc().as_node();
+        }
+
+        if self.get_xbl_binding().is_some() {
+            return self.as_node();
+        }
+
+        if let Some(parent) = self.get_xbl_binding_parent() {
+            return parent.as_node();
+        }
+
+        self.as_node().owner_doc().as_node()
+    }
+
     /// Execute `f` for each anonymous content child element (apart from
     /// ::before and ::after) whose originating element is `self`.
     fn each_anonymous_content_child<F>(&self, mut f: F)
diff --git a/components/style/sharing/checks.rs b/components/style/sharing/checks.rs
index 20020b9497b..9cba67ca0f3 100644
--- a/components/style/sharing/checks.rs
+++ b/components/style/sharing/checks.rs
@@ -6,7 +6,6 @@
 //! quickly whether it's worth to share style, and whether two different
 //! elements can indeed share the same style.
 
-use Atom;
 use bloom::StyleBloom;
 use context::{SelectorFlagsMap, SharedStyleContext};
 use dom::TElement;
@@ -96,14 +95,16 @@ pub fn have_same_class<E>(target: &mut StyleSharingTarget<E>,
 /// :first-child, etc, or on attributes that we don't check off-hand (pretty
 /// much every attribute selector except `id` and `class`.
 #[inline]
-pub fn revalidate<E>(target: &mut StyleSharingTarget<E>,
-                     candidate: &mut StyleSharingCandidate<E>,
-                     shared_context: &SharedStyleContext,
-                     bloom: &StyleBloom<E>,
-                     nth_index_cache: &mut NthIndexCache,
-                     selector_flags_map: &mut SelectorFlagsMap<E>)
-                     -> bool
-    where E: TElement,
+pub fn revalidate<E>(
+    target: &mut StyleSharingTarget<E>,
+    candidate: &mut StyleSharingCandidate<E>,
+    shared_context: &SharedStyleContext,
+    bloom: &StyleBloom<E>,
+    nth_index_cache: &mut NthIndexCache,
+    selector_flags_map: &mut SelectorFlagsMap<E>,
+) -> bool
+where
+    E: TElement,
 {
     let stylist = &shared_context.stylist;
 
@@ -130,16 +131,25 @@ pub fn revalidate<E>(target: &mut StyleSharingTarget<E>,
 
 /// Checks whether we might have rules for either of the two ids.
 #[inline]
-pub fn may_have_rules_for_ids(shared_context: &SharedStyleContext,
-                              element_id: Option<&Atom>,
-                              candidate_id: Option<&Atom>) -> bool
+pub fn may_match_different_id_rules<E>(
+    shared_context: &SharedStyleContext,
+    element: E,
+    candidate: E,
+) -> bool
+where
+    E: TElement,
 {
-    // We shouldn't be called unless the ids are different.
-    debug_assert!(element_id.is_some() || candidate_id.is_some());
+    let element_id = element.get_id();
+    let candidate_id = candidate.get_id();
+
+    if element_id == candidate_id {
+        return false;
+    }
+
     let stylist = &shared_context.stylist;
 
     let may_have_rules_for_element = match element_id {
-        Some(id) => stylist.may_have_rules_for_id(id),
+        Some(ref id) => stylist.may_have_rules_for_id(id, element),
         None => false
     };
 
@@ -148,7 +158,7 @@ pub fn may_have_rules_for_ids(shared_context: &SharedStyleContext,
     }
 
     match candidate_id {
-        Some(id) => stylist.may_have_rules_for_id(id),
+        Some(ref id) => stylist.may_have_rules_for_id(id, candidate),
         None => false
     }
 }
diff --git a/components/style/sharing/mod.rs b/components/style/sharing/mod.rs
index e99da60f4b9..d48ddc94017 100644
--- a/components/style/sharing/mod.rs
+++ b/components/style/sharing/mod.rs
@@ -206,10 +206,11 @@ impl ValidationData {
         bloom: &StyleBloom<E>,
         nth_index_cache: &mut NthIndexCache,
         bloom_known_valid: bool,
-        flags_setter: &mut F
+        flags_setter: &mut F,
     ) -> &SmallBitVec
-        where E: TElement,
-              F: FnMut(&E, ElementSelectorFlags),
+    where
+        E: TElement,
+        F: FnMut(&E, ElementSelectorFlags),
     {
         if self.revalidation_match_results.is_none() {
             // The bloom filter may already be set up for our element.
@@ -230,10 +231,12 @@ impl ValidationData {
                 }
             };
             self.revalidation_match_results =
-                Some(stylist.match_revalidation_selectors(&element,
-                                                          bloom_to_use,
-                                                          nth_index_cache,
-                                                          flags_setter));
+                Some(stylist.match_revalidation_selectors(
+                    element,
+                    bloom_to_use,
+                    nth_index_cache,
+                    flags_setter,
+                ));
         }
 
         self.revalidation_match_results.as_ref().unwrap()
@@ -661,6 +664,15 @@ impl<E: TElement> StyleSharingCache<E> {
             return None;
         }
 
+        // Note that in the XBL case, we should be able to assert that the
+        // scopes are different, since two elements with different XBL bindings
+        // need to necessarily have different style (and thus children of them
+        // would never pass the parent check).
+        if target.element.style_scope() != candidate.element.style_scope() {
+            trace!("Miss: Different style scopes");
+            return None;
+        }
+
         if *target.get_local_name() != *candidate.element.get_local_name() {
             trace!("Miss: Local Name");
             return None;
@@ -690,15 +702,17 @@ impl<E: TElement> StyleSharingCache<E> {
             return None;
         }
 
-        let element_id = target.element.get_id();
-        let candidate_id = candidate.element.get_id();
-        if element_id != candidate_id {
-            // It's possible that there are no styles for either id.
-            if checks::may_have_rules_for_ids(shared, element_id.as_ref(),
-                                              candidate_id.as_ref()) {
-                trace!("Miss: ID Attr");
-                return None;
-            }
+        // It's possible that there are no styles for either id.
+        let may_match_different_id_rules =
+            checks::may_match_different_id_rules(
+                shared,
+                target.element,
+                candidate.element,
+            );
+
+        if may_match_different_id_rules {
+            trace!("Miss: ID Attr");
+            return None;
         }
 
         if !checks::have_same_style_attribute(target, candidate) {
diff --git a/components/style/stylist.rs b/components/style/stylist.rs
index f819d7f7da1..acdb19da98b 100644
--- a/components/style/stylist.rs
+++ b/components/style/stylist.rs
@@ -1409,10 +1409,29 @@ impl Stylist {
     /// Given an id, returns whether there might be any rules for that id in any
     /// of our rule maps.
     #[inline]
-    pub fn may_have_rules_for_id(&self, id: &Atom) -> bool {
-        self.cascade_data
-            .iter_origins()
-            .any(|(d, _)| d.mapped_ids.might_contain_hash(id.get_hash()))
+    pub fn may_have_rules_for_id<E>(
+        &self,
+        id: &Atom,
+        element: E,
+    ) -> bool
+    where
+        E: TElement,
+    {
+        let hash = id.get_hash();
+        for (data, _) in self.cascade_data.iter_origins() {
+            if data.mapped_ids.might_contain_hash(hash) {
+                return true;
+            }
+        }
+
+        let mut xbl_rules_may_contain = false;
+
+        element.each_xbl_stylist(|stylist| {
+            xbl_rules_may_contain = xbl_rules_may_contain ||
+                stylist.cascade_data.author.mapped_ids.might_contain_hash(hash)
+        });
+
+        xbl_rules_may_contain
     }
 
     /// Returns the registered `@keyframes` animation for the specified name.
@@ -1428,7 +1447,7 @@ impl Stylist {
     /// revalidation selectors.
     pub fn match_revalidation_selectors<E, F>(
         &self,
-        element: &E,
+        element: E,
         bloom: Option<&BloomFilter>,
         nth_index_cache: &mut NthIndexCache,
         flags_setter: &mut F
@@ -1454,14 +1473,14 @@ impl Stylist {
         let mut results = SmallBitVec::new();
         for (data, _) in self.cascade_data.iter_origins() {
             data.selectors_for_cache_revalidation.lookup(
-                *element,
+                element,
                 self.quirks_mode,
                 &mut |selector_and_hashes| {
                     results.push(matches_selector(
                         &selector_and_hashes.selector,
                         selector_and_hashes.selector_offset,
                         Some(&selector_and_hashes.hashes),
-                        element,
+                        &element,
                         &mut matching_context,
                         flags_setter
                     ));
@@ -1470,6 +1489,24 @@ impl Stylist {
             );
         }
 
+        element.each_xbl_stylist(|stylist| {
+            stylist.cascade_data.author.selectors_for_cache_revalidation.lookup(
+                element,
+                stylist.quirks_mode,
+                &mut |selector_and_hashes| {
+                    results.push(matches_selector(
+                        &selector_and_hashes.selector,
+                        selector_and_hashes.selector_offset,
+                        Some(&selector_and_hashes.hashes),
+                        &element,
+                        &mut matching_context,
+                        flags_setter
+                    ));
+                    true
+                }
+            );
+        });
+
         results
     }