Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2199 insertions, 0 deletions

diff --git a/servo/components/style/gecko/wrapper.rs b/servo/components/style/gecko/wrapper.rs
new file mode 100644
index 0000000000..8c9ba40f93
--- /dev/null
+++ b/servo/components/style/gecko/wrapper.rs
@@ -0,0 +1,2199 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+#![allow(unsafe_code)]
+
+//! Wrapper definitions on top of Gecko types in order to be used in the style
+//! system.
+//!
+//! This really follows the Servo pattern in
+//! `components/script/layout_wrapper.rs`.
+//!
+//! This theoretically should live in its own crate, but now it lives in the
+//! style system it's kind of pointless in the Stylo case, and only Servo forces
+//! the separation between the style system implementation and everything else.
+
+use crate::applicable_declarations::ApplicableDeclarationBlock;
+use crate::context::{PostAnimationTasks, QuirksMode, SharedStyleContext, UpdateAnimationsTasks};
+use crate::data::ElementData;
+use crate::dom::{LayoutIterator, NodeInfo, OpaqueNode, TDocument, TElement, TNode, TShadowRoot};
+use crate::gecko::selector_parser::{NonTSPseudoClass, PseudoElement, SelectorImpl};
+use crate::gecko::snapshot_helpers;
+use crate::gecko_bindings::bindings;
+use crate::gecko_bindings::bindings::Gecko_ElementHasAnimations;
+use crate::gecko_bindings::bindings::Gecko_ElementHasCSSAnimations;
+use crate::gecko_bindings::bindings::Gecko_ElementHasCSSTransitions;
+use crate::gecko_bindings::bindings::Gecko_ElementState;
+use crate::gecko_bindings::bindings::Gecko_GetActiveLinkAttrDeclarationBlock;
+use crate::gecko_bindings::bindings::Gecko_GetAnimationEffectCount;
+use crate::gecko_bindings::bindings::Gecko_GetAnimationRule;
+use crate::gecko_bindings::bindings::Gecko_GetExtraContentStyleDeclarations;
+use crate::gecko_bindings::bindings::Gecko_GetHTMLPresentationAttrDeclarationBlock;
+use crate::gecko_bindings::bindings::Gecko_GetStyleAttrDeclarationBlock;
+use crate::gecko_bindings::bindings::Gecko_GetUnvisitedLinkAttrDeclarationBlock;
+use crate::gecko_bindings::bindings::Gecko_GetVisitedLinkAttrDeclarationBlock;
+use crate::gecko_bindings::bindings::Gecko_IsSignificantChild;
+use crate::gecko_bindings::bindings::Gecko_MatchLang;
+use crate::gecko_bindings::bindings::Gecko_UnsetDirtyStyleAttr;
+use crate::gecko_bindings::bindings::Gecko_UpdateAnimations;
+use crate::gecko_bindings::structs;
+use crate::gecko_bindings::structs::nsChangeHint;
+use crate::gecko_bindings::structs::EffectCompositor_CascadeLevel as CascadeLevel;
+use crate::gecko_bindings::structs::ELEMENT_HANDLED_SNAPSHOT;
+use crate::gecko_bindings::structs::ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO;
+use crate::gecko_bindings::structs::ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO;
+use crate::gecko_bindings::structs::ELEMENT_HAS_SNAPSHOT;
+use crate::gecko_bindings::structs::NODE_DESCENDANTS_NEED_FRAMES;
+use crate::gecko_bindings::structs::NODE_NEEDS_FRAME;
+use crate::gecko_bindings::structs::{nsAtom, nsIContent, nsINode_BooleanFlag};
+use crate::gecko_bindings::structs::{nsINode as RawGeckoNode, Element as RawGeckoElement};
+use crate::global_style_data::GLOBAL_STYLE_DATA;
+use crate::invalidation::element::restyle_hints::RestyleHint;
+use crate::media_queries::Device;
+use crate::properties::animated_properties::{AnimationValue, AnimationValueMap};
+use crate::properties::{ComputedValues, LonghandId};
+use crate::properties::{Importance, PropertyDeclaration, PropertyDeclarationBlock};
+use crate::rule_tree::CascadeLevel as ServoCascadeLevel;
+use crate::selector_parser::{AttrValue, Lang};
+use crate::shared_lock::{Locked, SharedRwLock};
+use crate::string_cache::{Atom, Namespace, WeakAtom, WeakNamespace};
+use crate::stylist::CascadeData;
+use crate::values::computed::Display;
+use crate::values::{AtomIdent, AtomString};
+use crate::CaseSensitivityExt;
+use crate::LocalName;
+use app_units::Au;
+use atomic_refcell::{AtomicRef, AtomicRefCell, AtomicRefMut};
+use dom::{DocumentState, ElementState};
+use euclid::default::Size2D;
+use fxhash::FxHashMap;
+use selectors::attr::{AttrSelectorOperation, AttrSelectorOperator};
+use selectors::attr::{CaseSensitivity, NamespaceConstraint};
+use selectors::matching::VisitedHandlingMode;
+use selectors::matching::{ElementSelectorFlags, MatchingContext};
+use selectors::sink::Push;
+use selectors::{Element, OpaqueElement};
+use servo_arc::{Arc, ArcBorrow};
+use std::fmt;
+use std::hash::{Hash, Hasher};
+use std::mem;
+use std::ptr;
+use std::sync::atomic::{AtomicU32, Ordering};
+
+#[inline]
+fn elements_with_id<'a, 'le>(
+    array: *const structs::nsTArray<*mut RawGeckoElement>,
+) -> &'a [GeckoElement<'le>] {
+    unsafe {
+        if array.is_null() {
+            return &[];
+        }
+
+        let elements: &[*mut RawGeckoElement] = &**array;
+
+        // NOTE(emilio): We rely on the in-memory representation of
+        // GeckoElement<'ld> and *mut RawGeckoElement being the same.
+        #[allow(dead_code)]
+        unsafe fn static_assert() {
+            mem::transmute::<*mut RawGeckoElement, GeckoElement<'static>>(0xbadc0de as *mut _);
+        }
+
+        mem::transmute(elements)
+    }
+}
+
+/// A simple wrapper over `Document`.
+#[derive(Clone, Copy)]
+pub struct GeckoDocument<'ld>(pub &'ld structs::Document);
+
+impl<'ld> TDocument for GeckoDocument<'ld> {
+    type ConcreteNode = GeckoNode<'ld>;
+
+    #[inline]
+    fn as_node(&self) -> Self::ConcreteNode {
+        GeckoNode(&self.0._base)
+    }
+
+    #[inline]
+    fn is_html_document(&self) -> bool {
+        self.0.mType == structs::Document_Type::eHTML
+    }
+
+    #[inline]
+    fn quirks_mode(&self) -> QuirksMode {
+        self.0.mCompatMode.into()
+    }
+
+    #[inline]
+    fn elements_with_id<'a>(&self, id: &AtomIdent) -> Result<&'a [GeckoElement<'ld>], ()>
+    where
+        Self: 'a,
+    {
+        Ok(elements_with_id(unsafe {
+            bindings::Gecko_Document_GetElementsWithId(self.0, id.as_ptr())
+        }))
+    }
+
+    fn shared_lock(&self) -> &SharedRwLock {
+        &GLOBAL_STYLE_DATA.shared_lock
+    }
+}
+
+/// A simple wrapper over `ShadowRoot`.
+#[derive(Clone, Copy)]
+pub struct GeckoShadowRoot<'lr>(pub &'lr structs::ShadowRoot);
+
+impl<'ln> fmt::Debug for GeckoShadowRoot<'ln> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        // TODO(emilio): Maybe print the host or something?
+        write!(f, "<shadow-root> ({:#x})", self.as_node().opaque().0)
+    }
+}
+
+impl<'lr> PartialEq for GeckoShadowRoot<'lr> {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.0 as *const _ == other.0 as *const _
+    }
+}
+
+impl<'lr> TShadowRoot for GeckoShadowRoot<'lr> {
+    type ConcreteNode = GeckoNode<'lr>;
+
+    #[inline]
+    fn as_node(&self) -> Self::ConcreteNode {
+        GeckoNode(&self.0._base._base._base._base)
+    }
+
+    #[inline]
+    fn host(&self) -> GeckoElement<'lr> {
+        GeckoElement(unsafe { &*self.0._base.mHost.mRawPtr })
+    }
+
+    #[inline]
+    fn style_data<'a>(&self) -> Option<&'a CascadeData>
+    where
+        Self: 'a,
+    {
+        let author_styles = unsafe { self.0.mServoStyles.mPtr.as_ref()? };
+        Some(&author_styles.data)
+    }
+
+    #[inline]
+    fn elements_with_id<'a>(&self, id: &AtomIdent) -> Result<&'a [GeckoElement<'lr>], ()>
+    where
+        Self: 'a,
+    {
+        Ok(elements_with_id(unsafe {
+            bindings::Gecko_ShadowRoot_GetElementsWithId(self.0, id.as_ptr())
+        }))
+    }
+
+    #[inline]
+    fn parts<'a>(&self) -> &[<Self::ConcreteNode as TNode>::ConcreteElement]
+    where
+        Self: 'a,
+    {
+        let slice: &[*const RawGeckoElement] = &*self.0.mParts;
+
+        #[allow(dead_code)]
+        unsafe fn static_assert() {
+            mem::transmute::<*const RawGeckoElement, GeckoElement<'static>>(0xbadc0de as *const _);
+        }
+
+        unsafe { mem::transmute(slice) }
+    }
+}
+
+/// A simple wrapper over a non-null Gecko node (`nsINode`) pointer.
+///
+/// Important: We don't currently refcount the DOM, because the wrapper lifetime
+/// magic guarantees that our LayoutFoo references won't outlive the root, and
+/// we don't mutate any of the references on the Gecko side during restyle.
+///
+/// We could implement refcounting if need be (at a potentially non-trivial
+/// performance cost) by implementing Drop and making LayoutFoo non-Copy.
+#[derive(Clone, Copy)]
+pub struct GeckoNode<'ln>(pub &'ln RawGeckoNode);
+
+impl<'ln> PartialEq for GeckoNode<'ln> {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.0 as *const _ == other.0 as *const _
+    }
+}
+
+impl<'ln> fmt::Debug for GeckoNode<'ln> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if let Some(el) = self.as_element() {
+            return el.fmt(f);
+        }
+
+        if self.is_text_node() {
+            return write!(f, "<text node> ({:#x})", self.opaque().0);
+        }
+
+        if self.is_document() {
+            return write!(f, "<document> ({:#x})", self.opaque().0);
+        }
+
+        if let Some(sr) = self.as_shadow_root() {
+            return sr.fmt(f);
+        }
+
+        write!(f, "<non-text node> ({:#x})", self.opaque().0)
+    }
+}
+
+impl<'ln> GeckoNode<'ln> {
+    #[inline]
+    fn is_document(&self) -> bool {
+        // This is a DOM constant that isn't going to change.
+        const DOCUMENT_NODE: u16 = 9;
+        self.node_info().mInner.mNodeType == DOCUMENT_NODE
+    }
+
+    #[inline]
+    fn is_shadow_root(&self) -> bool {
+        self.is_in_shadow_tree() && self.parent_node().is_none()
+    }
+
+    #[inline]
+    fn from_content(content: &'ln nsIContent) -> Self {
+        GeckoNode(&content._base)
+    }
+
+    #[inline]
+    fn set_flags(&self, flags: u32) {
+        self.flags_atomic().fetch_or(flags, Ordering::Relaxed);
+    }
+
+    #[inline]
+    fn flags_atomic(&self) -> &AtomicU32 {
+        use std::cell::Cell;
+        let flags: &Cell<u32> = &(self.0)._base._base_1.mFlags;
+
+        #[allow(dead_code)]
+        fn static_assert() {
+            let _: [u8; std::mem::size_of::<Cell<u32>>()] = [0u8; std::mem::size_of::<AtomicU32>()];
+            let _: [u8; std::mem::align_of::<Cell<u32>>()] =
+                [0u8; std::mem::align_of::<AtomicU32>()];
+        }
+
+        // Rust doesn't provide standalone atomic functions like GCC/clang do
+        // (via the atomic intrinsics) or via std::atomic_ref, but it guarantees
+        // that the memory representation of u32 and AtomicU32 matches:
+        // https://doc.rust-lang.org/std/sync/atomic/struct.AtomicU32.html
+        unsafe { std::mem::transmute::<&Cell<u32>, &AtomicU32>(flags) }
+    }
+
+    #[inline]
+    fn flags(&self) -> u32 {
+        self.flags_atomic().load(Ordering::Relaxed)
+    }
+
+    #[inline]
+    fn node_info(&self) -> &structs::NodeInfo {
+        debug_assert!(!self.0.mNodeInfo.mRawPtr.is_null());
+        unsafe { &*self.0.mNodeInfo.mRawPtr }
+    }
+
+    // These live in different locations depending on processor architecture.
+    #[cfg(target_pointer_width = "64")]
+    #[inline]
+    fn bool_flags(&self) -> u32 {
+        (self.0)._base._base_1.mBoolFlags
+    }
+
+    #[cfg(target_pointer_width = "32")]
+    #[inline]
+    fn bool_flags(&self) -> u32 {
+        (self.0).mBoolFlags
+    }
+
+    #[inline]
+    fn get_bool_flag(&self, flag: nsINode_BooleanFlag) -> bool {
+        self.bool_flags() & (1u32 << flag as u32) != 0
+    }
+
+    /// This logic is duplicate in Gecko's nsINode::IsInShadowTree().
+    #[inline]
+    fn is_in_shadow_tree(&self) -> bool {
+        use crate::gecko_bindings::structs::NODE_IS_IN_SHADOW_TREE;
+        self.flags() & NODE_IS_IN_SHADOW_TREE != 0
+    }
+
+    /// Returns true if we know for sure that `flattened_tree_parent` and `parent_node` return the
+    /// same thing.
+    ///
+    /// TODO(emilio): Measure and consider not doing this fast-path, it's only a function call and
+    /// from profiles it seems that keeping this fast path makes the compiler not inline
+    /// `flattened_tree_parent` as a whole, so we're not gaining much either.
+    #[inline]
+    fn flattened_tree_parent_is_parent(&self) -> bool {
+        use crate::gecko_bindings::structs::*;
+        let flags = self.flags();
+
+        let parent = match self.parent_node() {
+            Some(p) => p,
+            None => return true,
+        };
+
+        if parent.is_shadow_root() {
+            return false;
+        }
+
+        if let Some(parent) = parent.as_element() {
+            if flags & NODE_IS_NATIVE_ANONYMOUS_ROOT != 0 && parent.is_root() {
+                return false;
+            }
+            if parent.shadow_root().is_some() || parent.is_html_slot_element() {
+                return false;
+            }
+        }
+
+        true
+    }
+
+    #[inline]
+    fn flattened_tree_parent(&self) -> Option<Self> {
+        if self.flattened_tree_parent_is_parent() {
+            debug_assert_eq!(
+                unsafe {
+                    bindings::Gecko_GetFlattenedTreeParentNode(self.0)
+                        .as_ref()
+                        .map(GeckoNode)
+                },
+                self.parent_node(),
+                "Fast path stopped holding!"
+            );
+            return self.parent_node();
+        }
+
+        // NOTE(emilio): If this call is too expensive, we could manually inline more aggressively.
+        unsafe {
+            bindings::Gecko_GetFlattenedTreeParentNode(self.0)
+                .as_ref()
+                .map(GeckoNode)
+        }
+    }
+
+    #[inline]
+    fn contains_non_whitespace_content(&self) -> bool {
+        unsafe { Gecko_IsSignificantChild(self.0, false) }
+    }
+}
+
+impl<'ln> NodeInfo for GeckoNode<'ln> {
+    #[inline]
+    fn is_element(&self) -> bool {
+        self.get_bool_flag(nsINode_BooleanFlag::NodeIsElement)
+    }
+
+    fn is_text_node(&self) -> bool {
+        // This is a DOM constant that isn't going to change.
+        const TEXT_NODE: u16 = 3;
+        self.node_info().mInner.mNodeType == TEXT_NODE
+    }
+}
+
+impl<'ln> TNode for GeckoNode<'ln> {
+    type ConcreteDocument = GeckoDocument<'ln>;
+    type ConcreteShadowRoot = GeckoShadowRoot<'ln>;
+    type ConcreteElement = GeckoElement<'ln>;
+
+    #[inline]
+    fn parent_node(&self) -> Option<Self> {
+        unsafe { self.0.mParent.as_ref().map(GeckoNode) }
+    }
+
+    #[inline]
+    fn first_child(&self) -> Option<Self> {
+        unsafe {
+            self.0
+                .mFirstChild
+                .raw()
+                .as_ref()
+                .map(GeckoNode::from_content)
+        }
+    }
+
+    #[inline]
+    fn last_child(&self) -> Option<Self> {
+        unsafe { bindings::Gecko_GetLastChild(self.0).as_ref().map(GeckoNode) }
+    }
+
+    #[inline]
+    fn prev_sibling(&self) -> Option<Self> {
+        unsafe {
+            let prev_or_last = GeckoNode::from_content(self.0.mPreviousOrLastSibling.as_ref()?);
+            if prev_or_last.0.mNextSibling.raw().is_null() {
+                return None;
+            }
+            Some(prev_or_last)
+        }
+    }
+
+    #[inline]
+    fn next_sibling(&self) -> Option<Self> {
+        unsafe {
+            self.0
+                .mNextSibling
+                .raw()
+                .as_ref()
+                .map(GeckoNode::from_content)
+        }
+    }
+
+    #[inline]
+    fn owner_doc(&self) -> Self::ConcreteDocument {
+        debug_assert!(!self.node_info().mDocument.is_null());
+        GeckoDocument(unsafe { &*self.node_info().mDocument })
+    }
+
+    #[inline]
+    fn is_in_document(&self) -> bool {
+        self.get_bool_flag(nsINode_BooleanFlag::IsInDocument)
+    }
+
+    fn traversal_parent(&self) -> Option<GeckoElement<'ln>> {
+        self.flattened_tree_parent().and_then(|n| n.as_element())
+    }
+
+    #[inline]
+    fn opaque(&self) -> OpaqueNode {
+        let ptr: usize = self.0 as *const _ as usize;
+        OpaqueNode(ptr)
+    }
+
+    fn debug_id(self) -> usize {
+        unimplemented!()
+    }
+
+    #[inline]
+    fn as_element(&self) -> Option<GeckoElement<'ln>> {
+        if !self.is_element() {
+            return None;
+        }
+
+        Some(GeckoElement(unsafe {
+            &*(self.0 as *const _ as *const RawGeckoElement)
+        }))
+    }
+
+    #[inline]
+    fn as_document(&self) -> Option<Self::ConcreteDocument> {
+        if !self.is_document() {
+            return None;
+        }
+
+        debug_assert_eq!(self.owner_doc().as_node(), *self, "How?");
+        Some(self.owner_doc())
+    }
+
+    #[inline]
+    fn as_shadow_root(&self) -> Option<Self::ConcreteShadowRoot> {
+        if !self.is_shadow_root() {
+            return None;
+        }
+
+        Some(GeckoShadowRoot(unsafe {
+            &*(self.0 as *const _ as *const structs::ShadowRoot)
+        }))
+    }
+}
+
+/// A wrapper on top of two kind of iterators, depending on the parent being
+/// iterated.
+///
+/// We generally iterate children by traversing the light-tree siblings of the
+/// first child like Servo does.
+///
+/// However, for nodes with anonymous children, we use a custom (heavier-weight)
+/// Gecko-implemented iterator.
+///
+/// FIXME(emilio): If we take into account shadow DOM, we're going to need the
+/// flat tree pretty much always. We can try to optimize the case where there's
+/// no shadow root sibling, probably.
+pub enum GeckoChildrenIterator<'a> {
+    /// A simple iterator that tracks the current node being iterated and
+    /// replaces it with the next sibling when requested.
+    Current(Option<GeckoNode<'a>>),
+    /// A Gecko-implemented iterator we need to drop appropriately.
+    GeckoIterator(structs::StyleChildrenIterator),
+}
+
+impl<'a> Drop for GeckoChildrenIterator<'a> {
+    fn drop(&mut self) {
+        if let GeckoChildrenIterator::GeckoIterator(ref mut it) = *self {
+            unsafe {
+                bindings::Gecko_DestroyStyleChildrenIterator(it);
+            }
+        }
+    }
+}
+
+impl<'a> Iterator for GeckoChildrenIterator<'a> {
+    type Item = GeckoNode<'a>;
+    fn next(&mut self) -> Option<GeckoNode<'a>> {
+        match *self {
+            GeckoChildrenIterator::Current(curr) => {
+                let next = curr.and_then(|node| node.next_sibling());
+                *self = GeckoChildrenIterator::Current(next);
+                curr
+            },
+            GeckoChildrenIterator::GeckoIterator(ref mut it) => unsafe {
+                // We do this unsafe lengthening of the lifetime here because
+                // structs::StyleChildrenIterator is actually StyleChildrenIterator<'a>,
+                // however we can't express this easily with bindgen, and it would
+                // introduce functions with two input lifetimes into bindgen,
+                // which would be out of scope for elision.
+                bindings::Gecko_GetNextStyleChild(&mut *(it as *mut _))
+                    .as_ref()
+                    .map(GeckoNode)
+            },
+        }
+    }
+}
+
+/// A simple wrapper over a non-null Gecko `Element` pointer.
+#[derive(Clone, Copy)]
+pub struct GeckoElement<'le>(pub &'le RawGeckoElement);
+
+impl<'le> fmt::Debug for GeckoElement<'le> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use nsstring::nsCString;
+
+        write!(f, "<{}", self.local_name())?;
+
+        let mut attrs = nsCString::new();
+        unsafe {
+            bindings::Gecko_Element_DebugListAttributes(self.0, &mut attrs);
+        }
+        write!(f, "{}", attrs)?;
+        write!(f, "> ({:#x})", self.as_node().opaque().0)
+    }
+}
+
+impl<'le> GeckoElement<'le> {
+    /// Gets the raw `ElementData` refcell for the element.
+    #[inline(always)]
+    pub fn get_data(&self) -> Option<&AtomicRefCell<ElementData>> {
+        unsafe { self.0.mServoData.get().as_ref() }
+    }
+
+    /// Returns whether any animation applies to this element.
+    #[inline]
+    pub fn has_any_animation(&self) -> bool {
+        self.may_have_animations() && unsafe { Gecko_ElementHasAnimations(self.0) }
+    }
+
+    #[inline(always)]
+    fn non_mapped_attrs(&self) -> &[structs::AttrArray_InternalAttr] {
+        unsafe {
+            let attrs = match self.0.mAttrs.mImpl.mPtr.as_ref() {
+                Some(attrs) => attrs,
+                None => return &[],
+            };
+
+            attrs.mBuffer.as_slice(attrs.mAttrCount as usize)
+        }
+    }
+
+    #[inline(always)]
+    fn mapped_attrs(&self) -> &[structs::AttrArray_InternalAttr] {
+        unsafe {
+            let attrs = match self.0.mAttrs.mImpl.mPtr.as_ref() {
+                Some(attrs) => attrs,
+                None => return &[],
+            };
+
+            let attrs = match attrs.mMappedAttrs.as_ref() {
+                Some(attrs) => attrs,
+                None => return &[],
+            };
+
+            attrs.mBuffer.as_slice(attrs.mAttrCount as usize)
+        }
+    }
+
+    #[inline(always)]
+    fn get_part_attr(&self) -> Option<&structs::nsAttrValue> {
+        if !self.has_part_attr() {
+            return None;
+        }
+        snapshot_helpers::find_attr(self.non_mapped_attrs(), &atom!("part"))
+    }
+
+    #[inline(always)]
+    fn get_class_attr(&self) -> Option<&structs::nsAttrValue> {
+        if !self.may_have_class() {
+            return None;
+        }
+
+        if self.is_svg_element() {
+            let svg_class = unsafe { bindings::Gecko_GetSVGAnimatedClass(self.0).as_ref() };
+            if let Some(c) = svg_class {
+                return Some(c);
+            }
+        }
+
+        snapshot_helpers::find_attr(self.non_mapped_attrs(), &atom!("class"))
+    }
+
+    #[inline]
+    fn may_have_anonymous_children(&self) -> bool {
+        self.as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ElementMayHaveAnonymousChildren)
+    }
+
+    #[inline]
+    fn flags(&self) -> u32 {
+        self.as_node().flags()
+    }
+
+    #[inline]
+    fn set_flags(&self, flags: u32) {
+        self.as_node().set_flags(flags);
+    }
+
+    #[inline]
+    unsafe fn unset_flags(&self, flags: u32) {
+        self.as_node()
+            .flags_atomic()
+            .fetch_and(!flags, Ordering::Relaxed);
+    }
+
+    /// Returns true if this element has descendants for lazy frame construction.
+    #[inline]
+    pub fn descendants_need_frames(&self) -> bool {
+        self.flags() & NODE_DESCENDANTS_NEED_FRAMES != 0
+    }
+
+    /// Returns true if this element needs lazy frame construction.
+    #[inline]
+    pub fn needs_frame(&self) -> bool {
+        self.flags() & NODE_NEEDS_FRAME != 0
+    }
+
+    /// Returns a reference to the DOM slots for this Element, if they exist.
+    #[inline]
+    fn dom_slots(&self) -> Option<&structs::FragmentOrElement_nsDOMSlots> {
+        let slots = self.as_node().0.mSlots as *const structs::FragmentOrElement_nsDOMSlots;
+        unsafe { slots.as_ref() }
+    }
+
+    /// Returns a reference to the extended DOM slots for this Element.
+    #[inline]
+    fn extended_slots(&self) -> Option<&structs::FragmentOrElement_nsExtendedDOMSlots> {
+        self.dom_slots().and_then(|s| unsafe {
+            // For the bit usage, see nsContentSlots::GetExtendedSlots.
+            let e_slots = s._base.mExtendedSlots &
+                !structs::nsIContent_nsContentSlots_sNonOwningExtendedSlotsFlag;
+            (e_slots as *const structs::FragmentOrElement_nsExtendedDOMSlots).as_ref()
+        })
+    }
+
+    #[inline]
+    fn namespace_id(&self) -> i32 {
+        self.as_node().node_info().mInner.mNamespaceID
+    }
+
+    #[inline]
+    fn has_id(&self) -> bool {
+        self.as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ElementHasID)
+    }
+
+    #[inline]
+    fn state_internal(&self) -> u64 {
+        if !self
+            .as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ElementHasLockedStyleStates)
+        {
+            return self.0.mState.bits;
+        }
+        unsafe { Gecko_ElementState(self.0) }
+    }
+
+    #[inline]
+    fn document_state(&self) -> DocumentState {
+        DocumentState::from_bits_retain(self.as_node().owner_doc().0.mDocumentState.bits)
+    }
+
+    #[inline]
+    fn may_have_class(&self) -> bool {
+        self.as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ElementMayHaveClass)
+    }
+
+    #[inline]
+    fn has_properties(&self) -> bool {
+        use crate::gecko_bindings::structs::NODE_HAS_PROPERTIES;
+
+        self.flags() & NODE_HAS_PROPERTIES != 0
+    }
+
+    #[inline]
+    fn before_or_after_pseudo(&self, is_before: bool) -> Option<Self> {
+        if !self.has_properties() {
+            return None;
+        }
+
+        unsafe {
+            bindings::Gecko_GetBeforeOrAfterPseudo(self.0, is_before)
+                .as_ref()
+                .map(GeckoElement)
+        }
+    }
+
+    #[inline]
+    fn may_have_style_attribute(&self) -> bool {
+        self.as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ElementMayHaveStyle)
+    }
+
+    /// Only safe to call on the main thread, with exclusive access to the
+    /// element and its ancestors.
+    ///
+    /// This function is also called after display property changed for SMIL
+    /// animation.
+    ///
+    /// Also this function schedules style flush.
+    pub unsafe fn note_explicit_hints(&self, restyle_hint: RestyleHint, change_hint: nsChangeHint) {
+        use crate::gecko::restyle_damage::GeckoRestyleDamage;
+
+        let damage = GeckoRestyleDamage::new(change_hint);
+        debug!(
+            "note_explicit_hints: {:?}, restyle_hint={:?}, change_hint={:?}",
+            self, restyle_hint, change_hint
+        );
+
+        debug_assert!(
+            !(restyle_hint.has_animation_hint() && restyle_hint.has_non_animation_hint()),
+            "Animation restyle hints should not appear with non-animation restyle hints"
+        );
+
+        let mut data = match self.mutate_data() {
+            Some(d) => d,
+            None => {
+                debug!("(Element not styled, discarding hints)");
+                return;
+            },
+        };
+
+        debug_assert!(data.has_styles(), "how?");
+
+        // Propagate the bit up the chain.
+        if restyle_hint.has_animation_hint() {
+            bindings::Gecko_NoteAnimationOnlyDirtyElement(self.0);
+        } else {
+            bindings::Gecko_NoteDirtyElement(self.0);
+        }
+
+        data.hint.insert(restyle_hint);
+        data.damage |= damage;
+    }
+
+    /// This logic is duplicated in Gecko's nsIContent::IsRootOfNativeAnonymousSubtree.
+    #[inline]
+    fn is_root_of_native_anonymous_subtree(&self) -> bool {
+        use crate::gecko_bindings::structs::NODE_IS_NATIVE_ANONYMOUS_ROOT;
+        return self.flags() & NODE_IS_NATIVE_ANONYMOUS_ROOT != 0;
+    }
+
+    /// Returns true if this node is the shadow root of an use-element shadow tree.
+    #[inline]
+    fn is_root_of_use_element_shadow_tree(&self) -> bool {
+        if !self.as_node().is_in_shadow_tree() {
+            return false;
+        }
+        if !self.parent_node_is_shadow_root() {
+            return false;
+        }
+        let host = self.containing_shadow_host().unwrap();
+        host.is_svg_element() && host.local_name() == &**local_name!("use")
+    }
+
+    fn css_transitions_info(&self) -> FxHashMap<LonghandId, Arc<AnimationValue>> {
+        use crate::gecko_bindings::bindings::Gecko_ElementTransitions_EndValueAt;
+        use crate::gecko_bindings::bindings::Gecko_ElementTransitions_Length;
+
+        let collection_length = unsafe { Gecko_ElementTransitions_Length(self.0) } as usize;
+        let mut map = FxHashMap::with_capacity_and_hasher(collection_length, Default::default());
+
+        for i in 0..collection_length {
+            let end_value =
+                unsafe { Arc::from_raw_addrefed(Gecko_ElementTransitions_EndValueAt(self.0, i)) };
+            let property = end_value.id();
+            debug_assert!(!property.is_logical());
+            map.insert(property, end_value);
+        }
+        map
+    }
+
+    fn needs_transitions_update_per_property(
+        &self,
+        longhand_id: LonghandId,
+        combined_duration_seconds: f32,
+        before_change_style: &ComputedValues,
+        after_change_style: &ComputedValues,
+        existing_transitions: &FxHashMap<LonghandId, Arc<AnimationValue>>,
+    ) -> bool {
+        use crate::values::animated::{Animate, Procedure};
+        debug_assert!(!longhand_id.is_logical());
+
+        // If there is an existing transition, update only if the end value
+        // differs.
+        //
+        // If the end value has not changed, we should leave the currently
+        // running transition as-is since we don't want to interrupt its timing
+        // function.
+        if let Some(ref existing) = existing_transitions.get(&longhand_id) {
+            let after_value =
+                AnimationValue::from_computed_values(longhand_id, after_change_style).unwrap();
+
+            return ***existing != after_value;
+        }
+
+        let from = AnimationValue::from_computed_values(longhand_id, before_change_style);
+        let to = AnimationValue::from_computed_values(longhand_id, after_change_style);
+
+        debug_assert_eq!(to.is_some(), from.is_some());
+
+        combined_duration_seconds > 0.0f32 &&
+            from != to &&
+            from.unwrap()
+                .animate(
+                    to.as_ref().unwrap(),
+                    Procedure::Interpolate { progress: 0.5 },
+                )
+                .is_ok()
+    }
+}
+
+/// Converts flags from the layout used by rust-selectors to the layout used
+/// by Gecko. We could align these and then do this without conditionals, but
+/// it's probably not worth the trouble.
+fn selector_flags_to_node_flags(flags: ElementSelectorFlags) -> u32 {
+    use crate::gecko_bindings::structs::*;
+    let mut gecko_flags = 0u32;
+    if flags.contains(ElementSelectorFlags::HAS_SLOW_SELECTOR) {
+        gecko_flags |= NODE_HAS_SLOW_SELECTOR;
+    }
+    if flags.contains(ElementSelectorFlags::HAS_SLOW_SELECTOR_LATER_SIBLINGS) {
+        gecko_flags |= NODE_HAS_SLOW_SELECTOR_LATER_SIBLINGS;
+    }
+    if flags.contains(ElementSelectorFlags::HAS_SLOW_SELECTOR_NTH_OF) {
+        gecko_flags |= NODE_HAS_SLOW_SELECTOR_NTH_OF;
+    }
+    if flags.contains(ElementSelectorFlags::HAS_EDGE_CHILD_SELECTOR) {
+        gecko_flags |= NODE_HAS_EDGE_CHILD_SELECTOR;
+    }
+    if flags.contains(ElementSelectorFlags::HAS_EMPTY_SELECTOR) {
+        gecko_flags |= NODE_HAS_EMPTY_SELECTOR;
+    }
+    if flags.contains(ElementSelectorFlags::ANCHORS_RELATIVE_SELECTOR) {
+        gecko_flags |= NODE_ANCHORS_RELATIVE_SELECTOR;
+    }
+
+    gecko_flags
+}
+
+fn get_animation_rule(
+    element: &GeckoElement,
+    cascade_level: CascadeLevel,
+) -> Option<Arc<Locked<PropertyDeclarationBlock>>> {
+    use crate::properties::longhands::ANIMATABLE_PROPERTY_COUNT;
+
+    // There's a very rough correlation between the number of effects
+    // (animations) on an element and the number of properties it is likely to
+    // animate, so we use that as an initial guess for the size of the
+    // AnimationValueMap in order to reduce the number of re-allocations needed.
+    let effect_count = unsafe { Gecko_GetAnimationEffectCount(element.0) };
+    // Also, we should try to reuse the PDB, to avoid creating extra rule nodes.
+    let mut animation_values = AnimationValueMap::with_capacity_and_hasher(
+        effect_count.min(ANIMATABLE_PROPERTY_COUNT),
+        Default::default(),
+    );
+    if unsafe { Gecko_GetAnimationRule(element.0, cascade_level, &mut animation_values) } {
+        let shared_lock = &GLOBAL_STYLE_DATA.shared_lock;
+        Some(Arc::new(shared_lock.wrap(
+            PropertyDeclarationBlock::from_animation_value_map(&animation_values),
+        )))
+    } else {
+        None
+    }
+}
+
+impl<'le> TElement for GeckoElement<'le> {
+    type ConcreteNode = GeckoNode<'le>;
+    type TraversalChildrenIterator = GeckoChildrenIterator<'le>;
+
+    fn inheritance_parent(&self) -> Option<Self> {
+        if self.is_pseudo_element() {
+            return self.pseudo_element_originating_element();
+        }
+
+        self.as_node()
+            .flattened_tree_parent()
+            .and_then(|n| n.as_element())
+    }
+
+    fn traversal_children(&self) -> LayoutIterator<GeckoChildrenIterator<'le>> {
+        // This condition is similar to the check that
+        // StyleChildrenIterator::IsNeeded does, except that it might return
+        // true if we used to (but no longer) have anonymous content from
+        // ::before/::after, or nsIAnonymousContentCreators.
+        if self.is_html_slot_element() ||
+            self.shadow_root().is_some() ||
+            self.may_have_anonymous_children()
+        {
+            unsafe {
+                let mut iter: structs::StyleChildrenIterator = ::std::mem::zeroed();
+                bindings::Gecko_ConstructStyleChildrenIterator(self.0, &mut iter);
+                return LayoutIterator(GeckoChildrenIterator::GeckoIterator(iter));
+            }
+        }
+
+        LayoutIterator(GeckoChildrenIterator::Current(self.as_node().first_child()))
+    }
+
+    fn before_pseudo_element(&self) -> Option<Self> {
+        self.before_or_after_pseudo(/* is_before = */ true)
+    }
+
+    fn after_pseudo_element(&self) -> Option<Self> {
+        self.before_or_after_pseudo(/* is_before = */ false)
+    }
+
+    fn marker_pseudo_element(&self) -> Option<Self> {
+        if !self.has_properties() {
+            return None;
+        }
+
+        unsafe {
+            bindings::Gecko_GetMarkerPseudo(self.0)
+                .as_ref()
+                .map(GeckoElement)
+        }
+    }
+
+    #[inline]
+    fn is_html_element(&self) -> bool {
+        self.namespace_id() == structs::kNameSpaceID_XHTML as i32
+    }
+
+    #[inline]
+    fn is_mathml_element(&self) -> bool {
+        self.namespace_id() == structs::kNameSpaceID_MathML as i32
+    }
+
+    #[inline]
+    fn is_svg_element(&self) -> bool {
+        self.namespace_id() == structs::kNameSpaceID_SVG as i32
+    }
+
+    #[inline]
+    fn is_xul_element(&self) -> bool {
+        self.namespace_id() == structs::root::kNameSpaceID_XUL as i32
+    }
+
+    #[inline]
+    fn local_name(&self) -> &WeakAtom {
+        unsafe { WeakAtom::new(self.as_node().node_info().mInner.mName) }
+    }
+
+    #[inline]
+    fn namespace(&self) -> &WeakNamespace {
+        unsafe {
+            let namespace_manager = structs::nsNameSpaceManager_sInstance.mRawPtr;
+            WeakNamespace::new((*namespace_manager).mURIArray[self.namespace_id() as usize].mRawPtr)
+        }
+    }
+
+    #[inline]
+    fn query_container_size(&self, display: &Display) -> Size2D<Option<Au>> {
+        // If an element gets 'display: contents' and its nsIFrame has not been removed yet,
+        // Gecko_GetQueryContainerSize will not notice that it can't have size containment.
+        // Other cases like 'display: inline' will be handled once the new nsIFrame is created.
+        if display.is_contents() {
+            return Size2D::new(None, None);
+        }
+
+        let mut width = -1;
+        let mut height = -1;
+        unsafe {
+            bindings::Gecko_GetQueryContainerSize(self.0, &mut width, &mut height);
+        }
+        Size2D::new(
+            if width >= 0 { Some(Au(width)) } else { None },
+            if height >= 0 { Some(Au(height)) } else { None },
+        )
+    }
+
+    /// Return the list of slotted nodes of this node.
+    #[inline]
+    fn slotted_nodes(&self) -> &[Self::ConcreteNode] {
+        if !self.is_html_slot_element() || !self.as_node().is_in_shadow_tree() {
+            return &[];
+        }
+
+        let slot: &structs::HTMLSlotElement = unsafe { mem::transmute(self.0) };
+
+        if cfg!(debug_assertions) {
+            let base: &RawGeckoElement = &slot._base._base._base._base;
+            assert_eq!(base as *const _, self.0 as *const _, "Bad cast");
+        }
+
+        // FIXME(emilio): Workaround a bindgen bug on Android that causes
+        // mAssignedNodes to be at the wrong offset. See bug 1466406.
+        //
+        // Bug 1466580 tracks running the Android layout tests on automation.
+        //
+        // The actual bindgen bug still needs reduction.
+        let assigned_nodes: &[structs::RefPtr<structs::nsINode>] = if !cfg!(target_os = "android") {
+            debug_assert_eq!(
+                unsafe { bindings::Gecko_GetAssignedNodes(self.0) },
+                &slot.mAssignedNodes as *const _,
+            );
+
+            &*slot.mAssignedNodes
+        } else {
+            unsafe { &**bindings::Gecko_GetAssignedNodes(self.0) }
+        };
+
+        debug_assert_eq!(
+            mem::size_of::<structs::RefPtr<structs::nsINode>>(),
+            mem::size_of::<Self::ConcreteNode>(),
+            "Bad cast!"
+        );
+
+        unsafe { mem::transmute(assigned_nodes) }
+    }
+
+    #[inline]
+    fn shadow_root(&self) -> Option<GeckoShadowRoot<'le>> {
+        let slots = self.extended_slots()?;
+        unsafe { slots.mShadowRoot.mRawPtr.as_ref().map(GeckoShadowRoot) }
+    }
+
+    #[inline]
+    fn containing_shadow(&self) -> Option<GeckoShadowRoot<'le>> {
+        let slots = self.extended_slots()?;
+        unsafe {
+            slots
+                ._base
+                .mContainingShadow
+                .mRawPtr
+                .as_ref()
+                .map(GeckoShadowRoot)
+        }
+    }
+
+    fn each_anonymous_content_child<F>(&self, mut f: F)
+    where
+        F: FnMut(Self),
+    {
+        if !self.may_have_anonymous_children() {
+            return;
+        }
+
+        let array: *mut structs::nsTArray<*mut nsIContent> =
+            unsafe { bindings::Gecko_GetAnonymousContentForElement(self.0) };
+
+        if array.is_null() {
+            return;
+        }
+
+        for content in unsafe { &**array } {
+            let node = GeckoNode::from_content(unsafe { &**content });
+            let element = match node.as_element() {
+                Some(e) => e,
+                None => continue,
+            };
+
+            f(element);
+        }
+
+        unsafe { bindings::Gecko_DestroyAnonymousContentList(array) };
+    }
+
+    #[inline]
+    fn as_node(&self) -> Self::ConcreteNode {
+        unsafe { GeckoNode(&*(self.0 as *const _ as *const RawGeckoNode)) }
+    }
+
+    fn owner_doc_matches_for_testing(&self, device: &Device) -> bool {
+        self.as_node().owner_doc().0 as *const structs::Document == device.document() as *const _
+    }
+
+    fn style_attribute(&self) -> Option<ArcBorrow<Locked<PropertyDeclarationBlock>>> {
+        if !self.may_have_style_attribute() {
+            return None;
+        }
+
+        unsafe {
+            let declarations = Gecko_GetStyleAttrDeclarationBlock(self.0).as_ref()?;
+            Some(ArcBorrow::from_ref(declarations))
+        }
+    }
+
+    fn unset_dirty_style_attribute(&self) {
+        if !self.may_have_style_attribute() {
+            return;
+        }
+
+        unsafe { Gecko_UnsetDirtyStyleAttr(self.0) };
+    }
+
+    fn smil_override(&self) -> Option<ArcBorrow<Locked<PropertyDeclarationBlock>>> {
+        unsafe {
+            let slots = self.extended_slots()?;
+
+            let declaration: &structs::DeclarationBlock =
+                slots.mSMILOverrideStyleDeclaration.mRawPtr.as_ref()?;
+
+            let raw: &structs::StyleLockedDeclarationBlock = declaration.mRaw.mRawPtr.as_ref()?;
+            Some(ArcBorrow::from_ref(raw))
+        }
+    }
+
+    fn animation_rule(
+        &self,
+        _: &SharedStyleContext,
+    ) -> Option<Arc<Locked<PropertyDeclarationBlock>>> {
+        get_animation_rule(self, CascadeLevel::Animations)
+    }
+
+    fn transition_rule(
+        &self,
+        _: &SharedStyleContext,
+    ) -> Option<Arc<Locked<PropertyDeclarationBlock>>> {
+        get_animation_rule(self, CascadeLevel::Transitions)
+    }
+
+    #[inline]
+    fn state(&self) -> ElementState {
+        ElementState::from_bits_retain(self.state_internal())
+    }
+
+    #[inline]
+    fn has_attr(&self, namespace: &Namespace, attr: &AtomIdent) -> bool {
+        unsafe { bindings::Gecko_HasAttr(self.0, namespace.0.as_ptr(), attr.as_ptr()) }
+    }
+
+    #[inline]
+    fn has_part_attr(&self) -> bool {
+        self.as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ElementHasPart)
+    }
+
+    #[inline]
+    fn exports_any_part(&self) -> bool {
+        snapshot_helpers::find_attr(self.non_mapped_attrs(), &atom!("exportparts")).is_some()
+    }
+
+    // FIXME(emilio): we should probably just return a reference to the Atom.
+    #[inline]
+    fn id(&self) -> Option<&WeakAtom> {
+        if !self.has_id() {
+            return None;
+        }
+
+        snapshot_helpers::get_id(self.non_mapped_attrs())
+    }
+
+    fn each_attr_name<F>(&self, mut callback: F)
+    where
+        F: FnMut(&AtomIdent),
+    {
+        for attr in self
+            .non_mapped_attrs()
+            .iter()
+            .chain(self.mapped_attrs().iter())
+        {
+            let is_nodeinfo = attr.mName.mBits & 1 != 0;
+            unsafe {
+                let atom = if is_nodeinfo {
+                    let node_info = &*((attr.mName.mBits & !1) as *const structs::NodeInfo);
+                    node_info.mInner.mName
+                } else {
+                    attr.mName.mBits as *const nsAtom
+                };
+                AtomIdent::with(atom, |a| callback(a))
+            }
+        }
+    }
+
+    fn each_class<F>(&self, callback: F)
+    where
+        F: FnMut(&AtomIdent),
+    {
+        let attr = match self.get_class_attr() {
+            Some(c) => c,
+            None => return,
+        };
+
+        snapshot_helpers::each_class_or_part(attr, callback)
+    }
+
+    #[inline]
+    fn each_exported_part<F>(&self, name: &AtomIdent, callback: F)
+    where
+        F: FnMut(&AtomIdent),
+    {
+        snapshot_helpers::each_exported_part(self.non_mapped_attrs(), name, callback)
+    }
+
+    fn each_part<F>(&self, callback: F)
+    where
+        F: FnMut(&AtomIdent),
+    {
+        let attr = match self.get_part_attr() {
+            Some(c) => c,
+            None => return,
+        };
+
+        snapshot_helpers::each_class_or_part(attr, callback)
+    }
+
+    #[inline]
+    fn has_snapshot(&self) -> bool {
+        self.flags() & ELEMENT_HAS_SNAPSHOT != 0
+    }
+
+    #[inline]
+    fn handled_snapshot(&self) -> bool {
+        self.flags() & ELEMENT_HANDLED_SNAPSHOT != 0
+    }
+
+    unsafe fn set_handled_snapshot(&self) {
+        debug_assert!(self.has_data());
+        self.set_flags(ELEMENT_HANDLED_SNAPSHOT)
+    }
+
+    #[inline]
+    fn has_dirty_descendants(&self) -> bool {
+        self.flags() & ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO != 0
+    }
+
+    unsafe fn set_dirty_descendants(&self) {
+        debug_assert!(self.has_data());
+        debug!("Setting dirty descendants: {:?}", self);
+        self.set_flags(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO)
+    }
+
+    unsafe fn unset_dirty_descendants(&self) {
+        self.unset_flags(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO)
+    }
+
+    #[inline]
+    fn has_animation_only_dirty_descendants(&self) -> bool {
+        self.flags() & ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO != 0
+    }
+
+    unsafe fn set_animation_only_dirty_descendants(&self) {
+        self.set_flags(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO)
+    }
+
+    unsafe fn unset_animation_only_dirty_descendants(&self) {
+        self.unset_flags(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO)
+    }
+
+    unsafe fn clear_descendant_bits(&self) {
+        self.unset_flags(
+            ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO |
+                ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO |
+                NODE_DESCENDANTS_NEED_FRAMES,
+        )
+    }
+
+    fn is_visited_link(&self) -> bool {
+        self.state().intersects(ElementState::VISITED)
+    }
+
+    /// We want to match rules from the same tree in all cases, except for native anonymous content
+    /// that _isn't_ part directly of a UA widget (e.g., such generated by form controls, or
+    /// pseudo-elements).
+    #[inline]
+    fn matches_user_and_content_rules(&self) -> bool {
+        use crate::gecko_bindings::structs::{
+            NODE_HAS_BEEN_IN_UA_WIDGET, NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE,
+        };
+        let flags = self.flags();
+        (flags & NODE_IS_IN_NATIVE_ANONYMOUS_SUBTREE) == 0 ||
+            (flags & NODE_HAS_BEEN_IN_UA_WIDGET) != 0
+    }
+
+    #[inline]
+    fn implemented_pseudo_element(&self) -> Option<PseudoElement> {
+        if self.matches_user_and_content_rules() {
+            return None;
+        }
+
+        if !self.has_properties() {
+            return None;
+        }
+
+        PseudoElement::from_pseudo_type(unsafe { bindings::Gecko_GetImplementedPseudo(self.0) })
+    }
+
+    #[inline]
+    fn store_children_to_process(&self, _: isize) {
+        // This is only used for bottom-up traversal, and is thus a no-op for Gecko.
+    }
+
+    fn did_process_child(&self) -> isize {
+        panic!("Atomic child count not implemented in Gecko");
+    }
+
+    unsafe fn ensure_data(&self) -> AtomicRefMut<ElementData> {
+        if !self.has_data() {
+            debug!("Creating ElementData for {:?}", self);
+            let ptr = Box::into_raw(Box::new(AtomicRefCell::new(ElementData::default())));
+            self.0.mServoData.set(ptr);
+        }
+        self.mutate_data().unwrap()
+    }
+
+    unsafe fn clear_data(&self) {
+        let ptr = self.0.mServoData.get();
+        self.unset_flags(
+            ELEMENT_HAS_SNAPSHOT |
+                ELEMENT_HANDLED_SNAPSHOT |
+                structs::Element_kAllServoDescendantBits |
+                NODE_NEEDS_FRAME,
+        );
+        if !ptr.is_null() {
+            debug!("Dropping ElementData for {:?}", self);
+            let data = Box::from_raw(self.0.mServoData.get());
+            self.0.mServoData.set(ptr::null_mut());
+
+            // Perform a mutable borrow of the data in debug builds. This
+            // serves as an assertion that there are no outstanding borrows
+            // when we destroy the data.
+            debug_assert!({
+                let _ = data.borrow_mut();
+                true
+            });
+        }
+    }
+
+    #[inline]
+    fn skip_item_display_fixup(&self) -> bool {
+        debug_assert!(
+            !self.is_pseudo_element(),
+            "Just don't call me if I'm a pseudo, you should know the answer already"
+        );
+        self.is_root_of_native_anonymous_subtree()
+    }
+
+    #[inline]
+    fn may_have_animations(&self) -> bool {
+        if let Some(pseudo) = self.implemented_pseudo_element() {
+            if pseudo.animations_stored_in_parent() {
+                // FIXME(emilio): When would the parent of a ::before / ::after
+                // pseudo-element be null?
+                return self.parent_element().map_or(false, |p| {
+                    p.as_node()
+                        .get_bool_flag(nsINode_BooleanFlag::ElementHasAnimations)
+                });
+            }
+        }
+        self.as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ElementHasAnimations)
+    }
+
+    /// Process various tasks that are a result of animation-only restyle.
+    fn process_post_animation(&self, tasks: PostAnimationTasks) {
+        debug_assert!(!tasks.is_empty(), "Should be involved a task");
+
+        // If display style was changed from none to other, we need to resolve
+        // the descendants in the display:none subtree. Instead of resolving
+        // those styles in animation-only restyle, we defer it to a subsequent
+        // normal restyle.
+        if tasks.intersects(PostAnimationTasks::DISPLAY_CHANGED_FROM_NONE_FOR_SMIL) {
+            debug_assert!(
+                self.implemented_pseudo_element()
+                    .map_or(true, |p| !p.is_before_or_after()),
+                "display property animation shouldn't run on pseudo elements \
+                 since it's only for SMIL"
+            );
+            unsafe {
+                self.note_explicit_hints(
+                    RestyleHint::restyle_subtree(),
+                    nsChangeHint::nsChangeHint_Empty,
+                );
+            }
+        }
+    }
+
+    /// Update various animation-related state on a given (pseudo-)element as
+    /// results of normal restyle.
+    fn update_animations(
+        &self,
+        before_change_style: Option<Arc<ComputedValues>>,
+        tasks: UpdateAnimationsTasks,
+    ) {
+        // We have to update animations even if the element has no computed
+        // style since it means the element is in a display:none subtree, we
+        // should destroy all CSS animations in display:none subtree.
+        let computed_data = self.borrow_data();
+        let computed_values = computed_data.as_ref().map(|d| d.styles.primary());
+        let before_change_values = before_change_style
+            .as_ref()
+            .map_or(ptr::null(), |x| x.as_gecko_computed_style());
+        let computed_values_opt = computed_values
+            .as_ref()
+            .map_or(ptr::null(), |x| x.as_gecko_computed_style());
+        unsafe {
+            Gecko_UpdateAnimations(
+                self.0,
+                before_change_values,
+                computed_values_opt,
+                tasks.bits(),
+            );
+        }
+    }
+
+    #[inline]
+    fn has_animations(&self, _: &SharedStyleContext) -> bool {
+        self.has_any_animation()
+    }
+
+    fn has_css_animations(&self, _: &SharedStyleContext, _: Option<PseudoElement>) -> bool {
+        self.may_have_animations() && unsafe { Gecko_ElementHasCSSAnimations(self.0) }
+    }
+
+    fn has_css_transitions(&self, _: &SharedStyleContext, _: Option<PseudoElement>) -> bool {
+        self.may_have_animations() && unsafe { Gecko_ElementHasCSSTransitions(self.0) }
+    }
+
+    // Detect if there are any changes that require us to update transitions.
+    //
+    // This is used as a more thoroughgoing check than the cheaper
+    // might_need_transitions_update check.
+    //
+    // The following logic shadows the logic used on the Gecko side
+    // (nsTransitionManager::DoUpdateTransitions) where we actually perform the
+    // update.
+    //
+    // https://drafts.csswg.org/css-transitions/#starting
+    fn needs_transitions_update(
+        &self,
+        before_change_style: &ComputedValues,
+        after_change_style: &ComputedValues,
+    ) -> bool {
+        use crate::properties::LonghandIdSet;
+
+        let after_change_ui_style = after_change_style.get_ui();
+        let existing_transitions = self.css_transitions_info();
+
+        if after_change_style.get_box().clone_display().is_none() {
+            // We need to cancel existing transitions.
+            return !existing_transitions.is_empty();
+        }
+
+        let mut transitions_to_keep = LonghandIdSet::new();
+        for transition_property in after_change_style.transition_properties() {
+            let physical_longhand = transition_property
+                .longhand_id
+                .to_physical(after_change_style.writing_mode);
+            transitions_to_keep.insert(physical_longhand);
+            if self.needs_transitions_update_per_property(
+                physical_longhand,
+                after_change_ui_style
+                    .transition_combined_duration_at(transition_property.index)
+                    .seconds(),
+                before_change_style,
+                after_change_style,
+                &existing_transitions,
+            ) {
+                return true;
+            }
+        }
+
+        // Check if we have to cancel the running transition because this is not
+        // a matching transition-property value.
+        existing_transitions
+            .keys()
+            .any(|property| !transitions_to_keep.contains(*property))
+    }
+
+    /// Whether there is an ElementData container.
+    #[inline]
+    fn has_data(&self) -> bool {
+        self.get_data().is_some()
+    }
+
+    /// Immutably borrows the ElementData.
+    fn borrow_data(&self) -> Option<AtomicRef<ElementData>> {
+        self.get_data().map(|x| x.borrow())
+    }
+
+    /// Mutably borrows the ElementData.
+    fn mutate_data(&self) -> Option<AtomicRefMut<ElementData>> {
+        self.get_data().map(|x| x.borrow_mut())
+    }
+
+    #[inline]
+    fn lang_attr(&self) -> Option<AttrValue> {
+        let ptr = unsafe { bindings::Gecko_LangValue(self.0) };
+        if ptr.is_null() {
+            None
+        } else {
+            Some(AtomString(unsafe { Atom::from_addrefed(ptr) }))
+        }
+    }
+
+    fn match_element_lang(&self, override_lang: Option<Option<AttrValue>>, value: &Lang) -> bool {
+        // Gecko supports :lang() from CSS Selectors 4, which accepts a list
+        // of language tags, and does BCP47-style range matching.
+        let override_lang_ptr = match override_lang {
+            Some(Some(ref atom)) => atom.as_ptr(),
+            _ => ptr::null_mut(),
+        };
+        value.0.iter().any(|lang| unsafe {
+            Gecko_MatchLang(
+                self.0,
+                override_lang_ptr,
+                override_lang.is_some(),
+                lang.as_slice().as_ptr(),
+            )
+        })
+    }
+
+    fn is_html_document_body_element(&self) -> bool {
+        if self.local_name() != &**local_name!("body") {
+            return false;
+        }
+
+        if !self.is_html_element() {
+            return false;
+        }
+
+        unsafe { bindings::Gecko_IsDocumentBody(self.0) }
+    }
+
+    fn synthesize_presentational_hints_for_legacy_attributes<V>(
+        &self,
+        visited_handling: VisitedHandlingMode,
+        hints: &mut V,
+    ) where
+        V: Push<ApplicableDeclarationBlock>,
+    {
+        use crate::properties::longhands::_x_lang::SpecifiedValue as SpecifiedLang;
+        use crate::properties::longhands::color::SpecifiedValue as SpecifiedColor;
+        use crate::stylesheets::layer_rule::LayerOrder;
+        use crate::values::specified::{color::Color, font::XTextScale};
+        lazy_static! {
+            static ref TABLE_COLOR_RULE: ApplicableDeclarationBlock = {
+                let global_style_data = &*GLOBAL_STYLE_DATA;
+                let pdb = PropertyDeclarationBlock::with_one(
+                    PropertyDeclaration::Color(SpecifiedColor(Color::InheritFromBodyQuirk.into())),
+                    Importance::Normal,
+                );
+                let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
+                ApplicableDeclarationBlock::from_declarations(
+                    arc,
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                )
+            };
+            static ref MATHML_LANG_RULE: ApplicableDeclarationBlock = {
+                let global_style_data = &*GLOBAL_STYLE_DATA;
+                let pdb = PropertyDeclarationBlock::with_one(
+                    PropertyDeclaration::XLang(SpecifiedLang(atom!("x-math"))),
+                    Importance::Normal,
+                );
+                let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
+                ApplicableDeclarationBlock::from_declarations(
+                    arc,
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                )
+            };
+            static ref SVG_TEXT_DISABLE_SCALE_RULE: ApplicableDeclarationBlock = {
+                let global_style_data = &*GLOBAL_STYLE_DATA;
+                let pdb = PropertyDeclarationBlock::with_one(
+                    PropertyDeclaration::XTextScale(XTextScale::None),
+                    Importance::Normal,
+                );
+                let arc = Arc::new_leaked(global_style_data.shared_lock.wrap(pdb));
+                ApplicableDeclarationBlock::from_declarations(
+                    arc,
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                )
+            };
+        };
+
+        let ns = self.namespace_id();
+        // <th> elements get a default MozCenterOrInherit which may get overridden
+        if ns == structs::kNameSpaceID_XHTML as i32 {
+            if self.local_name().as_ptr() == atom!("table").as_ptr() &&
+                self.as_node().owner_doc().quirks_mode() == QuirksMode::Quirks
+            {
+                hints.push(TABLE_COLOR_RULE.clone());
+            }
+        }
+        if ns == structs::kNameSpaceID_SVG as i32 {
+            if self.local_name().as_ptr() == atom!("text").as_ptr() {
+                hints.push(SVG_TEXT_DISABLE_SCALE_RULE.clone());
+            }
+        }
+        let declarations =
+            unsafe { Gecko_GetHTMLPresentationAttrDeclarationBlock(self.0).as_ref() };
+        if let Some(decl) = declarations {
+            hints.push(ApplicableDeclarationBlock::from_declarations(
+                unsafe { Arc::from_raw_addrefed(decl) },
+                ServoCascadeLevel::PresHints,
+                LayerOrder::root(),
+            ));
+        }
+        let declarations = unsafe { Gecko_GetExtraContentStyleDeclarations(self.0).as_ref() };
+        if let Some(decl) = declarations {
+            hints.push(ApplicableDeclarationBlock::from_declarations(
+                unsafe { Arc::from_raw_addrefed(decl) },
+                ServoCascadeLevel::PresHints,
+                LayerOrder::root(),
+            ));
+        }
+
+        // Support for link, vlink, and alink presentation hints on <body>
+        if self.is_link() {
+            // Unvisited vs. visited styles are computed up-front based on the
+            // visited mode (not the element's actual state).
+            let declarations = match visited_handling {
+                VisitedHandlingMode::AllLinksVisitedAndUnvisited => {
+                    unreachable!(
+                        "We should never try to selector match with \
+                         AllLinksVisitedAndUnvisited"
+                    );
+                },
+                VisitedHandlingMode::AllLinksUnvisited => unsafe {
+                    Gecko_GetUnvisitedLinkAttrDeclarationBlock(self.0).as_ref()
+                },
+                VisitedHandlingMode::RelevantLinkVisited => unsafe {
+                    Gecko_GetVisitedLinkAttrDeclarationBlock(self.0).as_ref()
+                },
+            };
+            if let Some(decl) = declarations {
+                hints.push(ApplicableDeclarationBlock::from_declarations(
+                    unsafe { Arc::from_raw_addrefed(decl) },
+                    ServoCascadeLevel::PresHints,
+                    LayerOrder::root(),
+                ));
+            }
+
+            let active = self
+                .state()
+                .intersects(NonTSPseudoClass::Active.state_flag());
+            if active {
+                let declarations =
+                    unsafe { Gecko_GetActiveLinkAttrDeclarationBlock(self.0).as_ref() };
+                if let Some(decl) = declarations {
+                    hints.push(ApplicableDeclarationBlock::from_declarations(
+                        unsafe { Arc::from_raw_addrefed(decl) },
+                        ServoCascadeLevel::PresHints,
+                        LayerOrder::root(),
+                    ));
+                }
+            }
+        }
+
+        // xml:lang has precedence over lang, which can be
+        // set by Gecko_GetHTMLPresentationAttrDeclarationBlock
+        //
+        // http://www.whatwg.org/specs/web-apps/current-work/multipage/elements.html#language
+        let ptr = unsafe { bindings::Gecko_GetXMLLangValue(self.0) };
+        if !ptr.is_null() {
+            let global_style_data = &*GLOBAL_STYLE_DATA;
+
+            let pdb = PropertyDeclarationBlock::with_one(
+                PropertyDeclaration::XLang(SpecifiedLang(unsafe { Atom::from_addrefed(ptr) })),
+                Importance::Normal,
+            );
+            let arc = Arc::new(global_style_data.shared_lock.wrap(pdb));
+            hints.push(ApplicableDeclarationBlock::from_declarations(
+                arc,
+                ServoCascadeLevel::PresHints,
+                LayerOrder::root(),
+            ))
+        }
+        // MathML's default lang has precedence over both `lang` and `xml:lang`
+        if ns == structs::kNameSpaceID_MathML as i32 {
+            if self.local_name().as_ptr() == atom!("math").as_ptr() {
+                hints.push(MATHML_LANG_RULE.clone());
+            }
+        }
+    }
+
+    fn anchors_relative_selector(&self) -> bool {
+        use crate::gecko_bindings::structs::NODE_ANCHORS_RELATIVE_SELECTOR;
+        self.flags() & NODE_ANCHORS_RELATIVE_SELECTOR != 0
+    }
+}
+
+impl<'le> PartialEq for GeckoElement<'le> {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.0 as *const _ == other.0 as *const _
+    }
+}
+
+impl<'le> Eq for GeckoElement<'le> {}
+
+impl<'le> Hash for GeckoElement<'le> {
+    #[inline]
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        (self.0 as *const RawGeckoElement).hash(state);
+    }
+}
+
+impl<'le> ::selectors::Element for GeckoElement<'le> {
+    type Impl = SelectorImpl;
+
+    #[inline]
+    fn opaque(&self) -> OpaqueElement {
+        OpaqueElement::new(self.0)
+    }
+
+    #[inline]
+    fn parent_element(&self) -> Option<Self> {
+        let parent_node = self.as_node().parent_node();
+        parent_node.and_then(|n| n.as_element())
+    }
+
+    #[inline]
+    fn parent_node_is_shadow_root(&self) -> bool {
+        self.as_node()
+            .parent_node()
+            .map_or(false, |p| p.is_shadow_root())
+    }
+
+    #[inline]
+    fn containing_shadow_host(&self) -> Option<Self> {
+        let shadow = self.containing_shadow()?;
+        Some(shadow.host())
+    }
+
+    #[inline]
+    fn is_pseudo_element(&self) -> bool {
+        self.implemented_pseudo_element().is_some()
+    }
+
+    #[inline]
+    fn pseudo_element_originating_element(&self) -> Option<Self> {
+        debug_assert!(self.is_pseudo_element());
+        debug_assert!(!self.matches_user_and_content_rules());
+        let mut current = *self;
+        loop {
+            if current.is_root_of_native_anonymous_subtree() {
+                return current.traversal_parent();
+            }
+
+            current = current.traversal_parent()?;
+        }
+    }
+
+    #[inline]
+    fn assigned_slot(&self) -> Option<Self> {
+        let slot = self.extended_slots()?._base.mAssignedSlot.mRawPtr;
+
+        unsafe { Some(GeckoElement(&slot.as_ref()?._base._base._base._base)) }
+    }
+
+    #[inline]
+    fn prev_sibling_element(&self) -> Option<Self> {
+        let mut sibling = self.as_node().prev_sibling();
+        while let Some(sibling_node) = sibling {
+            if let Some(el) = sibling_node.as_element() {
+                return Some(el);
+            }
+            sibling = sibling_node.prev_sibling();
+        }
+        None
+    }
+
+    #[inline]
+    fn next_sibling_element(&self) -> Option<Self> {
+        let mut sibling = self.as_node().next_sibling();
+        while let Some(sibling_node) = sibling {
+            if let Some(el) = sibling_node.as_element() {
+                return Some(el);
+            }
+            sibling = sibling_node.next_sibling();
+        }
+        None
+    }
+
+    #[inline]
+    fn first_element_child(&self) -> Option<Self> {
+        let mut child = self.as_node().first_child();
+        while let Some(child_node) = child {
+            if let Some(el) = child_node.as_element() {
+                return Some(el);
+            }
+            child = child_node.next_sibling();
+        }
+        None
+    }
+
+    fn apply_selector_flags(&self, flags: ElementSelectorFlags) {
+        // Handle flags that apply to the element.
+        let self_flags = flags.for_self();
+        if !self_flags.is_empty() {
+            self.set_flags(selector_flags_to_node_flags(flags))
+        }
+
+        // Handle flags that apply to the parent.
+        let parent_flags = flags.for_parent();
+        if !parent_flags.is_empty() {
+            if let Some(p) = self.as_node().parent_node() {
+                if p.is_element() || p.is_shadow_root() {
+                    p.set_flags(selector_flags_to_node_flags(parent_flags));
+                }
+            }
+        }
+    }
+
+    fn attr_matches(
+        &self,
+        ns: &NamespaceConstraint<&Namespace>,
+        local_name: &LocalName,
+        operation: &AttrSelectorOperation<&AttrValue>,
+    ) -> bool {
+        unsafe {
+            match *operation {
+                AttrSelectorOperation::Exists => {
+                    bindings::Gecko_HasAttr(self.0, ns.atom_or_null(), local_name.as_ptr())
+                },
+                AttrSelectorOperation::WithValue {
+                    operator,
+                    case_sensitivity,
+                    expected_value,
+                } => {
+                    let ignore_case = match case_sensitivity {
+                        CaseSensitivity::CaseSensitive => false,
+                        CaseSensitivity::AsciiCaseInsensitive => true,
+                    };
+                    // FIXME: case sensitivity for operators other than Equal
+                    match operator {
+                        AttrSelectorOperator::Equal => bindings::Gecko_AttrEquals(
+                            self.0,
+                            ns.atom_or_null(),
+                            local_name.as_ptr(),
+                            expected_value.as_ptr(),
+                            ignore_case,
+                        ),
+                        AttrSelectorOperator::Includes => bindings::Gecko_AttrIncludes(
+                            self.0,
+                            ns.atom_or_null(),
+                            local_name.as_ptr(),
+                            expected_value.as_ptr(),
+                            ignore_case,
+                        ),
+                        AttrSelectorOperator::DashMatch => bindings::Gecko_AttrDashEquals(
+                            self.0,
+                            ns.atom_or_null(),
+                            local_name.as_ptr(),
+                            expected_value.as_ptr(),
+                            ignore_case,
+                        ),
+                        AttrSelectorOperator::Prefix => bindings::Gecko_AttrHasPrefix(
+                            self.0,
+                            ns.atom_or_null(),
+                            local_name.as_ptr(),
+                            expected_value.as_ptr(),
+                            ignore_case,
+                        ),
+                        AttrSelectorOperator::Suffix => bindings::Gecko_AttrHasSuffix(
+                            self.0,
+                            ns.atom_or_null(),
+                            local_name.as_ptr(),
+                            expected_value.as_ptr(),
+                            ignore_case,
+                        ),
+                        AttrSelectorOperator::Substring => bindings::Gecko_AttrHasSubstring(
+                            self.0,
+                            ns.atom_or_null(),
+                            local_name.as_ptr(),
+                            expected_value.as_ptr(),
+                            ignore_case,
+                        ),
+                    }
+                },
+            }
+        }
+    }
+
+    #[inline]
+    fn is_root(&self) -> bool {
+        if self
+            .as_node()
+            .get_bool_flag(nsINode_BooleanFlag::ParentIsContent)
+        {
+            return false;
+        }
+
+        if !self.as_node().is_in_document() {
+            return false;
+        }
+
+        debug_assert!(self
+            .as_node()
+            .parent_node()
+            .map_or(false, |p| p.is_document()));
+        // XXX this should always return true at this point, shouldn't it?
+        unsafe { bindings::Gecko_IsRootElement(self.0) }
+    }
+
+    fn is_empty(&self) -> bool {
+        !self
+            .as_node()
+            .dom_children()
+            .any(|child| unsafe { Gecko_IsSignificantChild(child.0, true) })
+    }
+
+    #[inline]
+    fn has_local_name(&self, name: &WeakAtom) -> bool {
+        self.local_name() == name
+    }
+
+    #[inline]
+    fn has_namespace(&self, ns: &WeakNamespace) -> bool {
+        self.namespace() == ns
+    }
+
+    #[inline]
+    fn is_same_type(&self, other: &Self) -> bool {
+        self.local_name() == other.local_name() && self.namespace() == other.namespace()
+    }
+
+    fn match_non_ts_pseudo_class(
+        &self,
+        pseudo_class: &NonTSPseudoClass,
+        context: &mut MatchingContext<Self::Impl>,
+    ) -> bool {
+        use selectors::matching::*;
+        match *pseudo_class {
+            NonTSPseudoClass::Autofill |
+            NonTSPseudoClass::Defined |
+            NonTSPseudoClass::Focus |
+            NonTSPseudoClass::Enabled |
+            NonTSPseudoClass::Disabled |
+            NonTSPseudoClass::Checked |
+            NonTSPseudoClass::Fullscreen |
+            NonTSPseudoClass::Indeterminate |
+            NonTSPseudoClass::MozInert |
+            NonTSPseudoClass::PopoverOpen |
+            NonTSPseudoClass::PlaceholderShown |
+            NonTSPseudoClass::Target |
+            NonTSPseudoClass::Valid |
+            NonTSPseudoClass::Invalid |
+            NonTSPseudoClass::MozBroken |
+            NonTSPseudoClass::MozLoading |
+            NonTSPseudoClass::Required |
+            NonTSPseudoClass::Optional |
+            NonTSPseudoClass::ReadOnly |
+            NonTSPseudoClass::ReadWrite |
+            NonTSPseudoClass::FocusWithin |
+            NonTSPseudoClass::FocusVisible |
+            NonTSPseudoClass::MozDragOver |
+            NonTSPseudoClass::MozDevtoolsHighlighted |
+            NonTSPseudoClass::MozStyleeditorTransitioning |
+            NonTSPseudoClass::MozMathIncrementScriptLevel |
+            NonTSPseudoClass::InRange |
+            NonTSPseudoClass::OutOfRange |
+            NonTSPseudoClass::Default |
+            NonTSPseudoClass::UserValid |
+            NonTSPseudoClass::UserInvalid |
+            NonTSPseudoClass::MozMeterOptimum |
+            NonTSPseudoClass::MozMeterSubOptimum |
+            NonTSPseudoClass::MozMeterSubSubOptimum |
+            NonTSPseudoClass::MozHasDirAttr |
+            NonTSPseudoClass::MozDirAttrLTR |
+            NonTSPseudoClass::MozDirAttrRTL |
+            NonTSPseudoClass::MozDirAttrLikeAuto |
+            NonTSPseudoClass::Modal |
+            NonTSPseudoClass::MozTopmostModal |
+            NonTSPseudoClass::Active |
+            NonTSPseudoClass::Hover |
+            NonTSPseudoClass::MozAutofillPreview |
+            NonTSPseudoClass::MozRevealed |
+            NonTSPseudoClass::MozValueEmpty |
+            NonTSPseudoClass::Dir(..) => self.state().intersects(pseudo_class.state_flag()),
+            NonTSPseudoClass::AnyLink => self.is_link(),
+            NonTSPseudoClass::Link => {
+                self.is_link() && context.visited_handling().matches_unvisited()
+            },
+            NonTSPseudoClass::Visited => {
+                self.is_link() && context.visited_handling().matches_visited()
+            },
+            NonTSPseudoClass::MozFirstNode => {
+                if context.needs_selector_flags() {
+                    self.apply_selector_flags(ElementSelectorFlags::HAS_EDGE_CHILD_SELECTOR);
+                }
+                let mut elem = self.as_node();
+                while let Some(prev) = elem.prev_sibling() {
+                    if prev.contains_non_whitespace_content() {
+                        return false;
+                    }
+                    elem = prev;
+                }
+                true
+            },
+            NonTSPseudoClass::MozLastNode => {
+                if context.needs_selector_flags() {
+                    self.apply_selector_flags(ElementSelectorFlags::HAS_EDGE_CHILD_SELECTOR);
+                }
+                let mut elem = self.as_node();
+                while let Some(next) = elem.next_sibling() {
+                    if next.contains_non_whitespace_content() {
+                        return false;
+                    }
+                    elem = next;
+                }
+                true
+            },
+            NonTSPseudoClass::MozOnlyWhitespace => {
+                if context.needs_selector_flags() {
+                    self.apply_selector_flags(ElementSelectorFlags::HAS_EMPTY_SELECTOR);
+                }
+                if self
+                    .as_node()
+                    .dom_children()
+                    .any(|c| c.contains_non_whitespace_content())
+                {
+                    return false;
+                }
+                true
+            },
+            NonTSPseudoClass::MozNativeAnonymous => !self.matches_user_and_content_rules(),
+            NonTSPseudoClass::MozUseShadowTreeRoot => self.is_root_of_use_element_shadow_tree(),
+            NonTSPseudoClass::MozTableBorderNonzero => unsafe {
+                bindings::Gecko_IsTableBorderNonzero(self.0)
+            },
+            NonTSPseudoClass::MozBrowserFrame => unsafe { bindings::Gecko_IsBrowserFrame(self.0) },
+            NonTSPseudoClass::MozSelectListBox => unsafe {
+                bindings::Gecko_IsSelectListBox(self.0)
+            },
+            NonTSPseudoClass::MozIsHTML => self.is_html_element_in_html_document(),
+
+            NonTSPseudoClass::MozLWTheme |
+            NonTSPseudoClass::MozLocaleDir(..) |
+            NonTSPseudoClass::MozWindowInactive => {
+                let state_bit = pseudo_class.document_state_flag();
+                if state_bit.is_empty() {
+                    debug_assert!(
+                        matches!(pseudo_class, NonTSPseudoClass::MozLocaleDir(..)),
+                        "Only moz-locale-dir should ever return an empty state"
+                    );
+                    return false;
+                }
+                if context
+                    .extra_data
+                    .invalidation_data
+                    .document_state
+                    .intersects(state_bit)
+                {
+                    return !context.in_negation();
+                }
+                self.document_state().contains(state_bit)
+            },
+            NonTSPseudoClass::MozPlaceholder => false,
+            NonTSPseudoClass::Lang(ref lang_arg) => self.match_element_lang(None, lang_arg),
+        }
+    }
+
+    fn match_pseudo_element(
+        &self,
+        pseudo_element: &PseudoElement,
+        _context: &mut MatchingContext<Self::Impl>,
+    ) -> bool {
+        // TODO(emilio): I believe we could assert we are a pseudo-element and
+        // match the proper pseudo-element, given how we rulehash the stuff
+        // based on the pseudo.
+        match self.implemented_pseudo_element() {
+            Some(ref pseudo) => *pseudo == *pseudo_element,
+            None => false,
+        }
+    }
+
+    #[inline]
+    fn is_link(&self) -> bool {
+        self.state().intersects(ElementState::VISITED_OR_UNVISITED)
+    }
+
+    #[inline]
+    fn has_id(&self, id: &AtomIdent, case_sensitivity: CaseSensitivity) -> bool {
+        if !self.has_id() {
+            return false;
+        }
+
+        let element_id = match snapshot_helpers::get_id(self.non_mapped_attrs()) {
+            Some(id) => id,
+            None => return false,
+        };
+
+        case_sensitivity.eq_atom(element_id, id)
+    }
+
+    #[inline]
+    fn is_part(&self, name: &AtomIdent) -> bool {
+        let attr = match self.get_part_attr() {
+            Some(c) => c,
+            None => return false,
+        };
+
+        snapshot_helpers::has_class_or_part(name, CaseSensitivity::CaseSensitive, attr)
+    }
+
+    #[inline]
+    fn imported_part(&self, name: &AtomIdent) -> Option<AtomIdent> {
+        snapshot_helpers::imported_part(self.non_mapped_attrs(), name)
+    }
+
+    #[inline(always)]
+    fn has_class(&self, name: &AtomIdent, case_sensitivity: CaseSensitivity) -> bool {
+        let attr = match self.get_class_attr() {
+            Some(c) => c,
+            None => return false,
+        };
+
+        snapshot_helpers::has_class_or_part(name, case_sensitivity, attr)
+    }
+
+    #[inline]
+    fn is_html_element_in_html_document(&self) -> bool {
+        self.is_html_element() && self.as_node().owner_doc().is_html_document()
+    }
+
+    #[inline]
+    fn is_html_slot_element(&self) -> bool {
+        self.is_html_element() && self.local_name().as_ptr() == local_name!("slot").as_ptr()
+    }
+
+    #[inline]
+    fn ignores_nth_child_selectors(&self) -> bool {
+        self.is_root_of_native_anonymous_subtree()
+    }
+}
+
+/// A few helpers to help with attribute selectors and snapshotting.
+pub trait NamespaceConstraintHelpers {
+    /// Returns the namespace of the selector, or null otherwise.
+    fn atom_or_null(&self) -> *mut nsAtom;
+}
+
+impl<'a> NamespaceConstraintHelpers for NamespaceConstraint<&'a Namespace> {
+    fn atom_or_null(&self) -> *mut nsAtom {
+        match *self {
+            NamespaceConstraint::Any => ptr::null_mut(),
+            NamespaceConstraint::Specific(ref ns) => ns.0.as_ptr(),
+        }
+    }
+}