style: Distinguish between the tree structures used for traversal and selector matching.

This patch renames TNode::parent_element to traversal_parent, since it returns
the parent from the perspective of traversal (which in Gecko uses the
flattened tree).  It also renames TNode::children to traversal_children
for the saem reason.

We keep parent_element and children functions on TNode to use for selector
matching, which must be done on the real DOM tree structure.

components/script/layout_wrapper.rs

@@ -165,12 +165,26 @@ impl<'ln> TNode for ServoLayoutNode<'ln> {
         transmute(node)
     }
 
-    fn children(self) -> LayoutIterator<ServoChildrenIterator<'ln>> {
+    fn parent_node(&self) -> Option<Self> {
+        unsafe {
+            self.node.parent_node_ref().map(|node| self.new_with_this_lifetime(&node))
+        }
+    }
+
+    fn children(&self) -> LayoutIterator<ServoChildrenIterator<'ln>> {
         LayoutIterator(ServoChildrenIterator {
             current: self.first_child(),
         })
     }
 
+    fn traversal_parent(&self) -> Option<ServoLayoutElement<'ln>> {
+        self.parent_element()
+    }
+
+    fn traversal_children(&self) -> LayoutIterator<ServoChildrenIterator<'ln>> {
+        self.children()
+    }
+
     fn opaque(&self) -> OpaqueNode {
         unsafe { self.get_jsmanaged().opaque() }
     }
@@ -199,12 +213,6 @@ impl<'ln> TNode for ServoLayoutNode<'ln> {
         self.node.set_flag(CAN_BE_FRAGMENTED, value)
     }
 
-    fn parent_node(&self) -> Option<ServoLayoutNode<'ln>> {
-        unsafe {
-            self.node.parent_node_ref().map(|node| self.new_with_this_lifetime(&node))
-        }
-    }
-
     fn is_in_doc(&self) -> bool {
         unsafe { (*self.node.unsafe_get()).is_in_doc() }
     }

components/style/bloom.rs

@@ -89,7 +89,7 @@ impl<E: TElement> StyleBloom<E> {
     pub fn push(&mut self, element: E) {
         if cfg!(debug_assertions) {
             if self.elements.is_empty() {
-                assert!(element.parent_element().is_none());
+                assert!(element.traversal_parent().is_none());
             }
         }
         self.push_internal(element);
@@ -139,7 +139,7 @@ impl<E: TElement> StyleBloom<E> {
     pub fn rebuild(&mut self, mut element: E) {
         self.clear();
 
-        while let Some(parent) = element.parent_element() {
+        while let Some(parent) = element.traversal_parent() {
             self.push_internal(parent);
             element = parent;
         }
@@ -155,7 +155,7 @@ impl<E: TElement> StyleBloom<E> {
     pub fn assert_complete(&self, mut element: E) {
         if cfg!(debug_assertions) {
             let mut checked = 0;
-            while let Some(parent) = element.parent_element() {
+            while let Some(parent) = element.traversal_parent() {
                 assert_eq!(parent, *self.elements[self.elements.len() - 1 - checked]);
                 element = parent;
                 checked += 1;
@@ -190,7 +190,7 @@ impl<E: TElement> StyleBloom<E> {
             return;
         }
 
-        let parent_element = match element.parent_element() {
+        let traversal_parent = match element.traversal_parent() {
             Some(parent) => parent,
             None => {
                 // Yay, another easy case.
@@ -199,7 +199,7 @@ impl<E: TElement> StyleBloom<E> {
             }
         };
 
-        if self.current_parent() == Some(parent_element) {
+        if self.current_parent() == Some(traversal_parent) {
             // Ta da, cache hit, we're all done.
             return;
         }
@@ -232,8 +232,8 @@ impl<E: TElement> StyleBloom<E> {
         }
 
         // Now let's try to find a common parent in the bloom filter chain,
-        // starting with parent_element.
+        // starting with traversal_parent.
-        let mut common_parent = parent_element;
+        let mut common_parent = traversal_parent;
         let mut common_parent_depth = element_depth - 1;
 
         // Let's collect the parents we are going to need to insert once we've
@@ -247,7 +247,7 @@ impl<E: TElement> StyleBloom<E> {
             // reverse the slice.
             parents_to_insert.push(common_parent);
             common_parent =
-                common_parent.parent_element().expect("We were lied");
+                common_parent.traversal_parent().expect("We were lied to");
             common_parent_depth -= 1;
         }
 
@@ -269,7 +269,7 @@ impl<E: TElement> StyleBloom<E> {
         while **self.elements.last().unwrap() != common_parent {
             parents_to_insert.push(common_parent);
             self.pop().unwrap();
-            common_parent = match common_parent.parent_element() {
+            common_parent = match common_parent.traversal_parent() {
                 Some(parent) => parent,
                 None => {
                     debug_assert!(self.elements.is_empty());

components/style/dom.rs

@@ -108,17 +108,27 @@ pub trait TNode : Sized + Copy + Clone + Debug + NodeInfo {
     /// Get a node back from an `UnsafeNode`.
     unsafe fn from_unsafe(n: &UnsafeNode) -> Self;
 
-    /// Returns an iterator over this node's children.
+    /// Get this node's parent node.
-    fn children(self) -> LayoutIterator<Self::ConcreteChildrenIterator>;
+    fn parent_node(&self) -> Option<Self>;
-
-    /// Converts self into an `OpaqueNode`.
-    fn opaque(&self) -> OpaqueNode;
 
     /// Get this node's parent element if present.
     fn parent_element(&self) -> Option<Self::ConcreteElement> {
         self.parent_node().and_then(|n| n.as_element())
     }
 
+    /// Returns an iterator over this node's children.
+    fn children(&self) -> LayoutIterator<Self::ConcreteChildrenIterator>;
+
+    /// Get this node's parent element from the perspective of a restyle
+    /// traversal.
+    fn traversal_parent(&self) -> Option<Self::ConcreteElement>;
+
+    /// Get this node's children from the perspective of a restyle traversal.
+    fn traversal_children(&self) -> LayoutIterator<Self::ConcreteChildrenIterator>;
+
+    /// Converts self into an `OpaqueNode`.
+    fn opaque(&self) -> OpaqueNode;
+
     /// A debug id, only useful, mm... for debugging.
     fn debug_id(self) -> usize;
 
@@ -138,9 +148,6 @@ pub trait TNode : Sized + Copy + Clone + Debug + NodeInfo {
     /// Set whether this node can be fragmented.
     unsafe fn set_can_be_fragmented(&self, value: bool);
 
-    /// Get this node's parent node.
-    fn parent_node(&self) -> Option<Self>;
-
     /// Whether this node is in the document right now needed to clear the
     /// restyle data appropriately on some forced restyles.
     fn is_in_doc(&self) -> bool;
@@ -222,7 +229,7 @@ fn fmt_subtree<F, N: TNode>(f: &mut fmt::Formatter, stringify: &F, n: N, indent:
         try!(write!(f, "  "));
     }
     try!(stringify(f, n));
-    for kid in n.children() {
+    for kid in n.traversal_children() {
         try!(writeln!(f, ""));
         try!(fmt_subtree(f, stringify, kid, indent + 1));
     }
@@ -256,7 +263,7 @@ pub unsafe fn raw_note_descendants<E, B>(element: E) -> bool
             break;
         }
         B::set(el);
-        curr = el.parent_element();
+        curr = el.traversal_parent();
     }
 
     // Note: We disable this assertion on servo because of bugs. See the
@@ -297,7 +304,7 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
     fn depth(&self) -> usize {
         let mut depth = 0;
         let mut curr = *self;
-        while let Some(parent) = curr.parent_element() {
+        while let Some(parent) = curr.traversal_parent() {
             depth += 1;
             curr = parent;
         }
@@ -315,11 +322,18 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
         }
     }
 
+    /// Get this node's parent element from the perspective of a restyle
+    /// traversal.
+    fn traversal_parent(&self) -> Option<Self> {
+        self.as_node().traversal_parent()
+    }
+
     /// Returns the parent element we should inherit from.
     ///
     /// This is pretty much always the parent element itself, except in the case
-    /// of Gecko's Native Anonymous Content, which may need to find the closest
+    /// of Gecko's Native Anonymous Content, which uses the traversal parent
-    /// non-NAC ancestor.
+    /// (i.e. the flattened tree parent) and which also may need to find the
+    /// closest non-NAC ancestor.
     fn inheritance_parent(&self) -> Option<Self> {
         self.parent_element()
     }
@@ -442,7 +456,7 @@ pub trait TElement : Eq + PartialEq + Debug + Hash + Sized + Copy + Clone +
         let mut current = Some(*self);
         while let Some(el) = current {
             if !B::has(el) { return false; }
-            current = el.parent_element();
+            current = el.traversal_parent();
         }
 
         true

components/style/gecko/wrapper.rs

@@ -204,6 +204,16 @@ impl<'ln> GeckoNode<'ln> {
         true
     }
 
+    fn flattened_tree_parent(&self) -> Option<Self> {
+        let fast_path = self.flattened_tree_parent_is_parent();
+        debug_assert!(fast_path == unsafe { bindings::Gecko_FlattenedTreeParentIsParent(self.0) });
+        if fast_path {
+            unsafe { self.0.mParent.as_ref().map(GeckoNode) }
+        } else {
+            unsafe { bindings::Gecko_GetFlattenedTreeParentNode(self.0).map(GeckoNode) }
+        }
+    }
+
     /// This logic is duplicated in Gecko's nsIContent::IsRootOfNativeAnonymousSubtree.
     fn is_root_of_native_anonymous_subtree(&self) -> bool {
         use gecko_bindings::structs::NODE_IS_NATIVE_ANONYMOUS_ROOT;
@@ -240,12 +250,24 @@ impl<'ln> TNode for GeckoNode<'ln> {
         GeckoNode(&*(n.0 as *mut RawGeckoNode))
     }
 
-    fn children(self) -> LayoutIterator<GeckoChildrenIterator<'ln>> {
+    fn parent_node(&self) -> Option<Self> {
+        unsafe { self.0.mParent.as_ref().map(GeckoNode) }
+    }
+
+    fn children(&self) -> LayoutIterator<GeckoChildrenIterator<'ln>> {
+        LayoutIterator(self.dom_children())
+    }
+
+    fn traversal_parent(&self) -> Option<GeckoElement<'ln>> {
+        self.flattened_tree_parent().and_then(|n| n.as_element())
+    }
+
+    fn traversal_children(&self) -> LayoutIterator<GeckoChildrenIterator<'ln>> {
         let maybe_iter = unsafe { Gecko_MaybeCreateStyleChildrenIterator(self.0) };
         if let Some(iter) = maybe_iter.into_owned_opt() {
             LayoutIterator(GeckoChildrenIterator::GeckoIterator(iter))
         } else {
-            LayoutIterator(GeckoChildrenIterator::Current(self.first_child()))
+            LayoutIterator(self.dom_children())
         }
     }
 
@@ -277,16 +299,6 @@ impl<'ln> TNode for GeckoNode<'ln> {
         // Maybe this isn’t useful for Gecko?
     }
 
-    fn parent_node(&self) -> Option<Self> {
-        let fast_path = self.flattened_tree_parent_is_parent();
-        debug_assert!(fast_path == unsafe { bindings::Gecko_FlattenedTreeParentIsParent(self.0) });
-        if fast_path {
-            unsafe { self.0.mParent.as_ref().map(GeckoNode) }
-        } else {
-            unsafe { bindings::Gecko_GetFlattenedTreeParentNode(self.0).map(GeckoNode) }
-        }
-    }
-
     fn is_in_doc(&self) -> bool {
         unsafe { bindings::Gecko_IsInDocument(self.0) }
     }
@@ -644,9 +656,10 @@ impl<'le> TElement for GeckoElement<'le> {
 
     fn inheritance_parent(&self) -> Option<Self> {
         if self.is_native_anonymous() {
-            return self.closest_non_native_anonymous_ancestor();
+            self.closest_non_native_anonymous_ancestor()
+        } else {
+            self.as_node().flattened_tree_parent().and_then(|n| n.as_element())
         }
-        return self.parent_element();
     }
 
     fn closest_non_native_anonymous_ancestor(&self) -> Option<Self> {

components/style/invalidation/stylesheets.rs

@@ -166,7 +166,7 @@ impl StylesheetInvalidationSet {
 
         let mut any_children_invalid = false;
 
-        for child in element.as_node().children() {
+        for child in element.as_node().traversal_children() {
             let child = match child.as_element() {
                 Some(e) => e,
                 None => continue,

components/style/matching.rs

@@ -230,7 +230,7 @@ trait PrivateMatchMethods: TElement {
     fn layout_parent(&self) -> Self {
         let mut current = self.clone();
         loop {
-            current = match current.parent_element() {
+            current = match current.traversal_parent() {
                 Some(el) => el,
                 None => return current,
             };

components/style/parallel.rs

@@ -64,7 +64,7 @@ pub fn traverse_dom<E, D>(traversal: &D,
     // it on the context to make it available to the bottom-up phase.
     let depth = if token.traverse_unstyled_children_only() {
         debug_assert!(!D::needs_postorder_traversal());
-        for kid in root.as_node().children() {
+        for kid in root.as_node().traversal_children() {
             if kid.as_element().map_or(false, |el| el.get_data().is_none()) {
                 nodes.push(unsafe { SendNode::new(kid) });
             }

components/style/sequential.rs

@@ -32,7 +32,7 @@ pub fn traverse_dom<E, D>(traversal: &D,
     let root_depth = root.depth();
 
     if token.traverse_unstyled_children_only() {
-        for kid in root.as_node().children() {
+        for kid in root.as_node().traversal_children() {
             if kid.as_element().map_or(false, |el| el.get_data().is_none()) {
                 discovered.push_back(WorkItem(kid, root_depth + 1));
             }

components/style/sharing/mod.rs

@@ -185,10 +185,10 @@ impl ValidationData {
             // filter, to avoid thrashing the filter.
             let bloom_to_use = if bloom_known_valid {
                 debug_assert_eq!(bloom.current_parent(),
-                                 element.parent_element());
+                                 element.traversal_parent());
                 Some(bloom.filter())
             } else {
-                if bloom.current_parent() == element.parent_element() {
+                if bloom.current_parent() == element.traversal_parent() {
                     Some(bloom.filter())
                 } else {
                     None
@@ -344,7 +344,7 @@ impl<E: TElement> StyleSharingTarget<E> {
             return StyleSharingResult::CannotShare;
         }
         debug_assert_eq!(bloom_filter.current_parent(),
-                         self.element.parent_element());
+                         self.element.traversal_parent());
 
         let result = cache
             .share_style_if_possible(shared_context,
@@ -500,7 +500,7 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
                               dom_depth: usize) {
         use selectors::matching::AFFECTED_BY_PRESENTATIONAL_HINTS;
 
-        let parent = match element.parent_element() {
+        let parent = match element.traversal_parent() {
             Some(element) => element,
             None => {
                 debug!("Failing to insert to the cache: no parent element");
@@ -572,7 +572,7 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
             return StyleSharingResult::CannotShare
         }
 
-        if target.parent_element().is_none() {
+        if target.traversal_parent().is_none() {
             debug!("{:?} Cannot share style: element has no parent",
                    target.element);
             return StyleSharingResult::CannotShare
@@ -644,8 +644,8 @@ impl<E: TElement> StyleSharingCandidateCache<E> {
         // Check that we have the same parent, or at least the same pointer
         // identity for parent computed style. The latter check allows us to
         // share style between cousins if the parents shared style.
-        let parent = target.parent_element();
+        let parent = target.traversal_parent();
-        let candidate_parent = candidate.element.parent_element();
+        let candidate_parent = candidate.element.traversal_parent();
         if parent != candidate_parent &&
            !checks::same_computed_values(parent, candidate_parent) {
             miss!(Parent)

components/style/traversal.rs

@@ -192,7 +192,7 @@ pub trait DomTraversal<E: TElement> : Sync {
                 if node.opaque() == root {
                     break;
                 }
-                let parent = node.parent_element().unwrap();
+                let parent = node.traversal_parent().unwrap();
                 let remaining = parent.did_process_child();
                 if remaining != 0 {
                     // The parent has other unprocessed descendants. We only
@@ -308,7 +308,7 @@ pub trait DomTraversal<E: TElement> : Sync {
         // But it may be that we no longer match, so detect that case
         // and act appropriately here.
         if el.is_native_anonymous() {
-            if let Some(parent) = el.parent_element() {
+            if let Some(parent) = el.traversal_parent() {
                 let parent_data = parent.borrow_data().unwrap();
                 let going_to_reframe = parent_data.get_restyle().map_or(false, |r| {
                     (r.damage | r.damage_handled())
@@ -467,7 +467,7 @@ pub trait DomTraversal<E: TElement> : Sync {
             return;
         }
 
-        for kid in parent.as_node().children() {
+        for kid in parent.as_node().traversal_children() {
             if Self::node_needs_traversal(kid, self.shared_context().traversal_flags) {
                 // If we are in a restyle for reconstruction, there is no need to
                 // perform a post-traversal, so we don't need to set the dirty
@@ -527,7 +527,7 @@ fn resolve_style_internal<E, F>(context: &mut StyleContext<E>,
     // If the Element isn't styled, we need to compute its style.
     if data.get_styles().is_none() {
         // Compute the parent style if necessary.
-        let parent = element.parent_element();
+        let parent = element.traversal_parent();
         if let Some(p) = parent {
             display_none_root = resolve_style_internal(context, p, ensure_data);
         }
@@ -604,7 +604,7 @@ pub fn resolve_style<E, F, G, H>(context: &mut StyleContext<E>, element: E,
                 break;
             }
             clear_data(curr);
-            curr = match curr.parent_element() {
+            curr = match curr.traversal_parent() {
                 Some(parent) => parent,
                 None => break,
             };
@@ -632,7 +632,7 @@ pub fn resolve_default_style<E, F, G, H>(context: &mut StyleContext<E>,
         let mut e = element;
         loop {
             old_data.push((e, set_data(e, None)));
-            match e.parent_element() {
+            match e.traversal_parent() {
                 Some(parent) => e = parent,
                 None => break,
             }
@@ -862,8 +862,8 @@ fn preprocess_children<E, D>(context: &mut StyleContext<E>,
 {
     trace!("preprocess_children: {:?}", element);
 
-    // Loop over all the children.
+    // Loop over all the traversal children.
-    for child in element.as_node().children() {
+    for child in element.as_node().traversal_children() {
         // FIXME(bholley): Add TElement::element_children instead of this.
         let child = match child.as_element() {
             Some(el) => el,
@@ -919,7 +919,7 @@ fn preprocess_children<E, D>(context: &mut StyleContext<E>,
 
 /// Clear style data for all the subtree under `el`.
 pub fn clear_descendant_data<E: TElement, F: Fn(E)>(el: E, clear_data: &F) {
-    for kid in el.as_node().children() {
+    for kid in el.as_node().traversal_children() {
         if let Some(kid) = kid.as_element() {
             // We maintain an invariant that, if an element has data, all its ancestors
             // have data as well. By consequence, any element without data has no

ports/geckolib/glue.rs

@@ -198,7 +198,7 @@ fn traverse_subtree(element: GeckoElement,
                     snapshots: &ServoElementSnapshotTable) {
     // When new content is inserted in a display:none subtree, we will call into
     // servo to try to style it. Detect that here and bail out.
-    if let Some(parent) = element.parent_element() {
+    if let Some(parent) = element.traversal_parent() {
         if parent.borrow_data().map_or(true, |d| d.styles().is_display_none()) {
             debug!("{:?} has unstyled parent {:?} - ignoring call to traverse_subtree", element, parent);
             return;
@@ -2398,7 +2398,7 @@ unsafe fn maybe_restyle<'a>(data: &'a mut AtomicRefMut<ElementData>,
     }
 
     // Propagate the bit up the chain.
-    if let Some(p) = element.parent_element() {
+    if let Some(p) = element.traversal_parent() {
         if animation_only {
             p.note_descendants::<AnimationOnlyDirtyDescendants>();
         } else {
@@ -2735,7 +2735,7 @@ pub extern "C" fn Servo_AssertTreeIsClean(root: RawGeckoElementBorrowed) {
     let root = GeckoElement(root);
     fn assert_subtree_is_clean<'le>(el: GeckoElement<'le>) {
         debug_assert!(!el.has_dirty_descendants() && !el.has_animation_only_dirty_descendants());
-        for child in el.as_node().children() {
+        for child in el.as_node().traversal_children() {
             if let Some(child) = child.as_element() {
                 assert_subtree_is_clean(child);
             }