Refactor style to be completely backend-independent

This commit refactors the style crate to be completely independent of
the actual implementation and pseudo-elements supported.

This also adds a gecko backend which introduces parsing for the
anonymous box pseudo-elements[1], although there's still no way of
querying them.

https://mxr.mozilla.org/mozilla-central/source/layout/style/nsCSSAnonBoxList.h

components/layout/Cargo.toml

@@ -64,7 +64,7 @@ heapsize_plugin = "0.1.2"
 libc = "0.2"
 log = "0.3"
 rustc-serialize = "0.3"
-selectors = {version = "0.4.2", features = ["heap_size"]}
+selectors = {version = "0.5", features = ["heap_size"]}
 serde = "0.6"
 serde_json = "0.5"
 serde_macros = "0.6"

components/layout/context.rs

@@ -25,8 +25,10 @@ use std::hash::BuildHasherDefault;
 use std::rc::Rc;
 use std::sync::mpsc::Sender;
 use std::sync::{Arc, Mutex};
-use style::context::{LocalStyleContext, SharedStyleContext, StyleContext};
+use style::context::{LocalStyleContext, StyleContext};
 use style::matching::{ApplicableDeclarationsCache, StyleSharingCandidateCache};
+use style::selector_impl::ServoSelectorImpl;
+use style::servo::SharedStyleContext;
 use url::Url;
 use util::opts;
 
@@ -104,7 +106,7 @@ pub struct LayoutContext<'a> {
     cached_local_layout_context: Rc<LocalLayoutContext>,
 }
 
-impl<'a> StyleContext<'a> for LayoutContext<'a> {
+impl<'a> StyleContext<'a, ServoSelectorImpl> for LayoutContext<'a> {
     fn shared_context(&self) -> &'a SharedStyleContext {
         &self.shared.style_context
     }

components/layout/data.rs

@@ -4,7 +4,7 @@
 
 use construct::ConstructionResult;
 use incremental::RestyleDamage;
-use style::data::PrivateStyleData;
+use style::servo::PrivateStyleData;
 
 /// Data that layout associates with a node.
 pub struct PrivateLayoutData {

components/layout/layout_thread.rs

@@ -62,13 +62,15 @@ use std::sync::mpsc::{channel, Sender, Receiver};
 use std::sync::{Arc, Mutex, MutexGuard, RwLock};
 use style::animation::Animation;
 use style::computed_values::{filter, mix_blend_mode};
-use style::context::{SharedStyleContext, StylistWrapper, ReflowGoal};
+use style::context::{ReflowGoal, StylistWrapper};
 use style::dom::{TDocument, TElement, TNode};
 use style::error_reporting::ParseErrorReporter;
 use style::media_queries::{Device, MediaType};
 use style::parallel::WorkQueueData;
-use style::selector_matching::{Stylist, USER_OR_USER_AGENT_STYLESHEETS};
-use style::stylesheets::{CSSRuleIteratorExt, Stylesheet};
+use style::selector_impl::ServoSelectorImpl;
+use style::selector_matching::USER_OR_USER_AGENT_STYLESHEETS;
+use style::servo::{SharedStyleContext, Stylesheet, Stylist};
+use style::stylesheets::CSSRuleIteratorExt;
 use traversal::RecalcStyleAndConstructFlows;
 use url::Url;
 use util::geometry::MAX_RECT;
@@ -477,7 +479,7 @@ impl LayoutThread {
             style_context: SharedStyleContext {
                 viewport_size: self.viewport_size.clone(),
                 screen_size_changed: screen_size_changed,
-                stylist: StylistWrapper(&*rw_data.stylist),
+                stylist: StylistWrapper::<ServoSelectorImpl>(&*rw_data.stylist),
                 generation: self.generation,
                 goal: goal,
                 new_animations_sender: Mutex::new(self.new_animations_sender.clone()),

components/layout/traversal.rs

@@ -16,6 +16,7 @@ use incremental::{BUBBLE_ISIZES, REFLOW, REFLOW_OUT_OF_FLOW, REPAINT, RestyleDam
 use std::mem;
 use style::context::{StyleContext, ReflowGoal};
 use style::matching::MatchMethods;
+use style::selector_impl::ServoSelectorImpl;
 use style::traversal::{DomTraversalContext, STYLE_BLOOM};
 use style::traversal::{put_thread_local_bloom_filter, recalc_style_at};
 use util::opts;
@@ -27,7 +28,8 @@ pub struct RecalcStyleAndConstructFlows<'lc> {
     root: OpaqueNode,
 }
 
-impl<'lc, 'ln, N: LayoutNode<'ln>> DomTraversalContext<'ln, N> for RecalcStyleAndConstructFlows<'lc> {
+impl<'lc, 'ln, N: LayoutNode<'ln>> DomTraversalContext<'ln, N> for RecalcStyleAndConstructFlows<'lc>
+    where N::ConcreteElement: ::selectors::Element<Impl=ServoSelectorImpl> {
     type SharedContext = SharedLayoutContext;
     #[allow(unsafe_code)]
     fn new<'a>(shared: &'a Self::SharedContext, root: OpaqueNode) -> Self {

components/layout/wrapper.rs

@@ -64,13 +64,13 @@ use std::sync::Arc;
 use string_cache::{Atom, Namespace};
 use style::computed_values::content::ContentItem;
 use style::computed_values::{content, display};
-use style::data::PrivateStyleData;
 use style::dom::{TDocument, TElement, TNode, UnsafeNode};
 use style::element_state::*;
 use style::properties::ComputedValues;
 use style::properties::{PropertyDeclaration, PropertyDeclarationBlock};
 use style::restyle_hints::ElementSnapshot;
-use style::selector_impl::{NonTSPseudoClass, ServoSelectorImpl};
+use style::selector_impl::{NonTSPseudoClass, PseudoElement, ServoSelectorImpl};
+use style::servo::PrivateStyleData;
 use url::Url;
 use util::str::{is_whitespace, search_index};
 
@@ -664,16 +664,20 @@ pub trait ThreadSafeLayoutNode<'ln> : Clone + Copy + Sized {
 
     #[inline]
     fn get_before_pseudo(&self) -> Option<Self> {
-        self.borrow_layout_data().unwrap().style_data.before_style.as_ref().map(|style| {
-            self.with_pseudo(PseudoElementType::Before(style.get_box().display))
-        })
+        self.borrow_layout_data().unwrap()
+            .style_data.per_pseudo
+            .get(&PseudoElement::Before).unwrap_or(&None).as_ref().map(|style| {
+                self.with_pseudo(PseudoElementType::Before(style.get_box().display))
+            })
     }
 
     #[inline]
     fn get_after_pseudo(&self) -> Option<Self> {
-        self.borrow_layout_data().unwrap().style_data.after_style.as_ref().map(|style| {
-            self.with_pseudo(PseudoElementType::After(style.get_box().display))
-        })
+        self.borrow_layout_data().unwrap()
+            .style_data.per_pseudo
+            .get(&PseudoElement::After).unwrap_or(&None).as_ref().map(|style| {
+                self.with_pseudo(PseudoElementType::After(style.get_box().display))
+            })
     }
 
     /// Borrows the layout data immutably. Fails on a conflicting borrow.
@@ -696,8 +700,8 @@ pub trait ThreadSafeLayoutNode<'ln> : Clone + Copy + Sized {
     fn style(&self) -> Ref<Arc<ComputedValues>> {
         Ref::map(self.borrow_layout_data().unwrap(), |data| {
             let style = match self.get_pseudo_element_type() {
-                PseudoElementType::Before(_) => &data.style_data.before_style,
-                PseudoElementType::After(_) => &data.style_data.after_style,
+                PseudoElementType::Before(_) => data.style_data.per_pseudo.get(&PseudoElement::Before).unwrap(),
+                PseudoElementType::After(_) => data.style_data.per_pseudo.get(&PseudoElement::After).unwrap(),
                 PseudoElementType::Normal => &data.style_data.style,
             };
             style.as_ref().unwrap()
@@ -711,9 +715,19 @@ pub trait ThreadSafeLayoutNode<'ln> : Clone + Copy + Sized {
         let mut data = self.mutate_layout_data().unwrap();
         let style =
             match self.get_pseudo_element_type() {
-                PseudoElementType::Before(_) => &mut data.style_data.before_style,
-                PseudoElementType::After (_) => &mut data.style_data.after_style,
-                PseudoElementType::Normal    => &mut data.style_data.style,
+                PseudoElementType::Before(_) => {
+                    match data.style_data.per_pseudo.get_mut(&PseudoElement::Before) {
+                        None => return,
+                        Some(style) => style,
+                    }
+                }
+                PseudoElementType::After(_) => {
+                    match data.style_data.per_pseudo.get_mut(&PseudoElement::After) {
+                        None => return,
+                        Some(style) => style,
+                    }
+                }
+                PseudoElementType::Normal => &mut data.style_data.style,
             };
 
         *style = None;
@@ -934,10 +948,11 @@ impl<'ln> ThreadSafeLayoutNode<'ln> for ServoThreadSafeLayoutNode<'ln> {
             let data = &self.borrow_layout_data().unwrap().style_data;
 
             let style = if self.pseudo.is_before() {
-                &data.before_style
+                data.per_pseudo.get(&PseudoElement::Before).unwrap()
             } else {
-                &data.after_style
+                data.per_pseudo.get(&PseudoElement::After).unwrap()
             };
+
             return match style.as_ref().unwrap().get_box().content {
                 content::T::Content(ref value) if !value.is_empty() => {
                     TextContent::GeneratedContent((*value).clone())