1 files changed, 497 insertions, 0 deletions
diff --git a/components/shared/script_layout/wrapper_traits.rs b/components/shared/script_layout/wrapper_traits.rs
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+++ b/components/shared/script_layout/wrapper_traits.rs
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+/* 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)]
+
+use std::borrow::Cow;
+use std::fmt::Debug;
+use std::sync::Arc as StdArc;
+
+use atomic_refcell::AtomicRef;
+use gfx_traits::{combine_id_with_fragment_type, ByteIndex, FragmentType};
+use html5ever::{local_name, namespace_url, ns, LocalName, Namespace};
+use msg::constellation_msg::{BrowsingContextId, PipelineId};
+use net_traits::image::base::{Image, ImageMetadata};
+use range::Range;
+use servo_arc::Arc;
+use servo_url::ServoUrl;
+use style::attr::AttrValue;
+use style::context::SharedStyleContext;
+use style::data::ElementData;
+use style::dom::{LayoutIterator, NodeInfo, OpaqueNode, TElement, TNode};
+use style::properties::ComputedValues;
+use style::selector_parser::{PseudoElement, PseudoElementCascadeType, SelectorImpl};
+use style::stylist::RuleInclusion;
+use webrender_api::ExternalScrollId;
+
+use crate::{HTMLCanvasData, HTMLMediaData, LayoutNodeType, SVGSVGData, StyleAndOpaqueLayoutData};
+
+pub trait LayoutDataTrait: Default + Send + Sync + 'static {}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum PseudoElementType {
+    Normal,
+    Before,
+    After,
+    DetailsSummary,
+    DetailsContent,
+}
+
+impl PseudoElementType {
+    pub fn fragment_type(&self) -> FragmentType {
+        match *self {
+            PseudoElementType::Normal => FragmentType::FragmentBody,
+            PseudoElementType::Before => FragmentType::BeforePseudoContent,
+            PseudoElementType::After => FragmentType::AfterPseudoContent,
+            PseudoElementType::DetailsSummary => FragmentType::FragmentBody,
+            PseudoElementType::DetailsContent => FragmentType::FragmentBody,
+        }
+    }
+
+    pub fn is_before(&self) -> bool {
+        match *self {
+            PseudoElementType::Before => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_replaced_content(&self) -> bool {
+        match *self {
+            PseudoElementType::Before | PseudoElementType::After => true,
+            _ => false,
+        }
+    }
+
+    pub fn style_pseudo_element(&self) -> PseudoElement {
+        match *self {
+            PseudoElementType::Normal => {
+                unreachable!("style_pseudo_element called with PseudoElementType::Normal")
+            },
+            PseudoElementType::Before => PseudoElement::Before,
+            PseudoElementType::After => PseudoElement::After,
+            PseudoElementType::DetailsSummary => PseudoElement::DetailsSummary,
+            PseudoElementType::DetailsContent => PseudoElement::DetailsContent,
+        }
+    }
+}
+
+/// Trait to abstract access to layout data across various data structures.
+pub trait GetStyleAndOpaqueLayoutData<'dom> {
+    fn get_style_and_opaque_layout_data(self) -> Option<&'dom StyleAndOpaqueLayoutData>;
+}
+
+/// A wrapper so that layout can access only the methods that it should have access to. Layout must
+/// only ever see these and must never see instances of `LayoutDom`.
+/// FIXME(mrobinson): `Send + Sync` is required here for Layout 2020, but eventually it
+/// should stop sending LayoutNodes to other threads and rely on ThreadSafeLayoutNode
+/// or some other mechanism to ensure thread safety.
+pub trait LayoutNode<'dom>:
+    Copy + Debug + GetStyleAndOpaqueLayoutData<'dom> + TNode + Send + Sync
+{
+    type ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<'dom>;
+    fn to_threadsafe(&self) -> Self::ConcreteThreadSafeLayoutNode;
+
+    /// Returns the type ID of this node.
+    fn type_id(&self) -> LayoutNodeType;
+
+    unsafe fn initialize_data(&self);
+    unsafe fn init_style_and_opaque_layout_data(&self, data: Box<StyleAndOpaqueLayoutData>);
+    unsafe fn take_style_and_opaque_layout_data(&self) -> Box<StyleAndOpaqueLayoutData>;
+
+    fn rev_children(self) -> LayoutIterator<ReverseChildrenIterator<Self>> {
+        LayoutIterator(ReverseChildrenIterator {
+            current: self.last_child(),
+        })
+    }
+
+    fn traverse_preorder(self) -> TreeIterator<Self> {
+        TreeIterator::new(self)
+    }
+
+    /// Returns whether the node is connected.
+    fn is_connected(&self) -> bool;
+}
+
+pub struct ReverseChildrenIterator<ConcreteNode> {
+    current: Option<ConcreteNode>,
+}
+
+impl<'dom, ConcreteNode> Iterator for ReverseChildrenIterator<ConcreteNode>
+where
+    ConcreteNode: LayoutNode<'dom>,
+{
+    type Item = ConcreteNode;
+    fn next(&mut self) -> Option<ConcreteNode> {
+        let node = self.current;
+        self.current = node.and_then(|node| node.prev_sibling());
+        node
+    }
+}
+
+pub struct TreeIterator<ConcreteNode> {
+    stack: Vec<ConcreteNode>,
+}
+
+impl<'dom, ConcreteNode> TreeIterator<ConcreteNode>
+where
+    ConcreteNode: LayoutNode<'dom>,
+{
+    fn new(root: ConcreteNode) -> TreeIterator<ConcreteNode> {
+        let mut stack = vec![];
+        stack.push(root);
+        TreeIterator { stack: stack }
+    }
+
+    pub fn next_skipping_children(&mut self) -> Option<ConcreteNode> {
+        self.stack.pop()
+    }
+}
+
+impl<'dom, ConcreteNode> Iterator for TreeIterator<ConcreteNode>
+where
+    ConcreteNode: LayoutNode<'dom>,
+{
+    type Item = ConcreteNode;
+    fn next(&mut self) -> Option<ConcreteNode> {
+        let ret = self.stack.pop();
+        ret.map(|node| self.stack.extend(node.rev_children()));
+        ret
+    }
+}
+
+/// A thread-safe version of `LayoutNode`, used during flow construction. This type of layout
+/// node does not allow any parents or siblings of nodes to be accessed, to avoid races.
+pub trait ThreadSafeLayoutNode<'dom>:
+    Clone + Copy + Debug + GetStyleAndOpaqueLayoutData<'dom> + NodeInfo + PartialEq + Sized
+{
+    type ConcreteNode: LayoutNode<'dom, ConcreteThreadSafeLayoutNode = Self>;
+    type ConcreteElement: TElement;
+
+    type ConcreteThreadSafeLayoutElement: ThreadSafeLayoutElement<'dom, ConcreteThreadSafeLayoutNode = Self>
+        + ::selectors::Element<Impl = SelectorImpl>;
+    type ChildrenIterator: Iterator<Item = Self> + Sized;
+
+    /// Converts self into an `OpaqueNode`.
+    fn opaque(&self) -> OpaqueNode;
+
+    /// Returns the type ID of this node.
+    /// Returns `None` if this is a pseudo-element; otherwise, returns `Some`.
+    fn type_id(&self) -> Option<LayoutNodeType>;
+
+    /// Returns the style for a text node. This is computed on the fly from the
+    /// parent style to avoid traversing text nodes in the style system.
+    ///
+    /// Note that this does require accessing the parent, which this interface
+    /// technically forbids. But accessing the parent is only unsafe insofar as
+    /// it can be used to reach siblings and cousins. A simple immutable borrow
+    /// of the parent data is fine, since the bottom-up traversal will not process
+    /// the parent until all the children have been processed.
+    fn parent_style(&self) -> Arc<ComputedValues>;
+
+    fn get_before_pseudo(&self) -> Option<Self> {
+        self.as_element()
+            .and_then(|el| el.get_before_pseudo())
+            .map(|el| el.as_node())
+    }
+
+    fn get_after_pseudo(&self) -> Option<Self> {
+        self.as_element()
+            .and_then(|el| el.get_after_pseudo())
+            .map(|el| el.as_node())
+    }
+
+    fn get_details_summary_pseudo(&self) -> Option<Self> {
+        self.as_element()
+            .and_then(|el| el.get_details_summary_pseudo())
+            .map(|el| el.as_node())
+    }
+
+    fn get_details_content_pseudo(&self) -> Option<Self> {
+        self.as_element()
+            .and_then(|el| el.get_details_content_pseudo())
+            .map(|el| el.as_node())
+    }
+
+    fn debug_id(self) -> usize;
+
+    /// Returns an iterator over this node's children.
+    fn children(&self) -> LayoutIterator<Self::ChildrenIterator>;
+
+    /// Returns a ThreadSafeLayoutElement if this is an element, None otherwise.
+    fn as_element(&self) -> Option<Self::ConcreteThreadSafeLayoutElement>;
+
+    #[inline]
+    fn get_pseudo_element_type(&self) -> PseudoElementType {
+        self.as_element()
+            .map_or(PseudoElementType::Normal, |el| el.get_pseudo_element_type())
+    }
+
+    fn get_style_and_opaque_layout_data(self) -> Option<&'dom StyleAndOpaqueLayoutData>;
+
+    fn style(&self, context: &SharedStyleContext) -> Arc<ComputedValues> {
+        if let Some(el) = self.as_element() {
+            el.style(context)
+        } else {
+            // Text nodes are not styled during traversal,instead we simply
+            // return parent style here and do cascading during layout.
+            debug_assert!(self.is_text_node());
+            self.parent_style()
+        }
+    }
+
+    fn selected_style(&self) -> Arc<ComputedValues> {
+        if let Some(el) = self.as_element() {
+            el.selected_style()
+        } else {
+            debug_assert!(self.is_text_node());
+            // TODO(stshine): What should the selected style be for text?
+            self.parent_style()
+        }
+    }
+
+    fn is_ignorable_whitespace(&self, context: &SharedStyleContext) -> bool;
+
+    /// Returns true if this node contributes content. This is used in the implementation of
+    /// `empty_cells` per CSS 2.1 § 17.6.1.1.
+    fn is_content(&self) -> bool {
+        self.type_id().is_some()
+    }
+
+    /// Returns access to the underlying LayoutNode. This is breaks the abstraction
+    /// barrier of ThreadSafeLayout wrapper layer, and can lead to races if not used
+    /// carefully.
+    ///
+    /// We need this because the implementation of some methods need to access the layout
+    /// data flags, and we have this annoying trait separation between script and layout :-(
+    unsafe fn unsafe_get(self) -> Self::ConcreteNode;
+
+    fn node_text_content(self) -> Cow<'dom, str>;
+
+    /// If the insertion point is within this node, returns it. Otherwise, returns `None`.
+    fn selection(&self) -> Option<Range<ByteIndex>>;
+
+    /// If this is an image element, returns its URL. If this is not an image element, fails.
+    fn image_url(&self) -> Option<ServoUrl>;
+
+    /// If this is an image element, returns its current-pixel-density. If this is not an image element, fails.
+    fn image_density(&self) -> Option<f64>;
+
+    /// If this is an image element, returns its image data. Otherwise, returns `None`.
+    fn image_data(&self) -> Option<(Option<StdArc<Image>>, Option<ImageMetadata>)>;
+
+    fn canvas_data(&self) -> Option<HTMLCanvasData>;
+
+    fn svg_data(&self) -> Option<SVGSVGData>;
+
+    fn media_data(&self) -> Option<HTMLMediaData>;
+
+    /// If this node is an iframe element, returns its browsing context ID. If this node is
+    /// not an iframe element, fails. Returns None if there is no nested browsing context.
+    fn iframe_browsing_context_id(&self) -> Option<BrowsingContextId>;
+
+    /// If this node is an iframe element, returns its pipeline ID. If this node is
+    /// not an iframe element, fails. Returns None if there is no nested browsing context.
+    fn iframe_pipeline_id(&self) -> Option<PipelineId>;
+
+    fn get_colspan(&self) -> u32;
+
+    fn get_rowspan(&self) -> u32;
+
+    fn fragment_type(&self) -> FragmentType {
+        self.get_pseudo_element_type().fragment_type()
+    }
+
+    fn generate_scroll_id(&self, pipeline_id: PipelineId) -> ExternalScrollId {
+        let id = combine_id_with_fragment_type(self.opaque().id(), self.fragment_type());
+        ExternalScrollId(id as u64, pipeline_id.to_webrender())
+    }
+}
+
+pub trait ThreadSafeLayoutElement<'dom>:
+    Clone
+    + Copy
+    + Sized
+    + Debug
+    + ::selectors::Element<Impl = SelectorImpl>
+    + GetStyleAndOpaqueLayoutData<'dom>
+{
+    type ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode<
+        'dom,
+        ConcreteThreadSafeLayoutElement = Self,
+    >;
+
+    /// This type alias is just a work-around to avoid writing
+    ///
+    ///   <Self::ConcreteThreadSafeLayoutNode as ThreadSafeLayoutNode>::ConcreteElement
+    ///
+    type ConcreteElement: TElement;
+
+    fn as_node(&self) -> Self::ConcreteThreadSafeLayoutNode;
+
+    /// Creates a new `ThreadSafeLayoutElement` for the same `LayoutElement`
+    /// with a different pseudo-element type.
+    fn with_pseudo(&self, pseudo: PseudoElementType) -> Self;
+
+    /// Returns the type ID of this node.
+    /// Returns `None` if this is a pseudo-element; otherwise, returns `Some`.
+    fn type_id(&self) -> Option<LayoutNodeType>;
+
+    /// Returns access to the underlying TElement. This is breaks the abstraction
+    /// barrier of ThreadSafeLayout wrapper layer, and can lead to races if not used
+    /// carefully.
+    ///
+    /// We need this so that the functions defined on this trait can call
+    /// lazily_compute_pseudo_element_style, which operates on TElement.
+    unsafe fn unsafe_get(self) -> Self::ConcreteElement;
+
+    fn get_attr(&self, namespace: &Namespace, name: &LocalName) -> Option<&str>;
+
+    fn get_attr_enum(&self, namespace: &Namespace, name: &LocalName) -> Option<&AttrValue>;
+
+    fn style_data(&self) -> AtomicRef<ElementData>;
+
+    fn get_pseudo_element_type(&self) -> PseudoElementType;
+
+    #[inline]
+    fn get_before_pseudo(&self) -> Option<Self> {
+        if self
+            .style_data()
+            .styles
+            .pseudos
+            .get(&PseudoElement::Before)
+            .is_some()
+        {
+            Some(self.with_pseudo(PseudoElementType::Before))
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    fn get_after_pseudo(&self) -> Option<Self> {
+        if self
+            .style_data()
+            .styles
+            .pseudos
+            .get(&PseudoElement::After)
+            .is_some()
+        {
+            Some(self.with_pseudo(PseudoElementType::After))
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    fn get_details_summary_pseudo(&self) -> Option<Self> {
+        if self.has_local_name(&local_name!("details")) && self.has_namespace(&ns!(html)) {
+            Some(self.with_pseudo(PseudoElementType::DetailsSummary))
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    fn get_details_content_pseudo(&self) -> Option<Self> {
+        if self.has_local_name(&local_name!("details")) &&
+            self.has_namespace(&ns!(html)) &&
+            self.get_attr(&ns!(), &local_name!("open")).is_some()
+        {
+            Some(self.with_pseudo(PseudoElementType::DetailsContent))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the style results for the given node. If CSS selector matching
+    /// has not yet been performed, fails.
+    ///
+    /// Unlike the version on TNode, this handles pseudo-elements.
+    #[inline]
+    fn style(&self, context: &SharedStyleContext) -> Arc<ComputedValues> {
+        let data = self.style_data();
+        match self.get_pseudo_element_type() {
+            PseudoElementType::Normal => data.styles.primary().clone(),
+            other => {
+                // Precompute non-eagerly-cascaded pseudo-element styles if not
+                // cached before.
+                let style_pseudo = other.style_pseudo_element();
+                match style_pseudo.cascade_type() {
+                    // Already computed during the cascade.
+                    PseudoElementCascadeType::Eager => self
+                        .style_data()
+                        .styles
+                        .pseudos
+                        .get(&style_pseudo)
+                        .unwrap()
+                        .clone(),
+                    PseudoElementCascadeType::Precomputed => context
+                        .stylist
+                        .precomputed_values_for_pseudo::<Self::ConcreteElement>(
+                            &context.guards,
+                            &style_pseudo,
+                            Some(data.styles.primary()),
+                        ),
+                    PseudoElementCascadeType::Lazy => {
+                        context
+                            .stylist
+                            .lazily_compute_pseudo_element_style(
+                                &context.guards,
+                                unsafe { self.unsafe_get() },
+                                &style_pseudo,
+                                RuleInclusion::All,
+                                data.styles.primary(),
+                                /* is_probe = */ false,
+                                /* matching_func = */ None,
+                            )
+                            .unwrap()
+                    },
+                }
+            },
+        }
+    }
+
+    #[inline]
+    fn selected_style(&self) -> Arc<ComputedValues> {
+        let data = self.style_data();
+        data.styles
+            .pseudos
+            .get(&PseudoElement::Selection)
+            .unwrap_or(data.styles.primary())
+            .clone()
+    }
+
+    /// Returns the already resolved style of the node.
+    ///
+    /// This differs from `style(ctx)` in that if the pseudo-element has not yet
+    /// been computed it would panic.
+    ///
+    /// This should be used just for querying layout, or when we know the
+    /// element style is precomputed, not from general layout itself.
+    #[inline]
+    fn resolved_style(&self) -> Arc<ComputedValues> {
+        let data = self.style_data();
+        match self.get_pseudo_element_type() {
+            PseudoElementType::Normal => data.styles.primary().clone(),
+            other => data
+                .styles
+                .pseudos
+                .get(&other.style_pseudo_element())
+                .unwrap()
+                .clone(),
+        }
+    }
+
+    fn is_shadow_host(&self) -> bool;
+
+    /// Returns whether this node is a body element of an html element root
+    /// in an HTML element document.
+    ///
+    /// Note that this does require accessing the parent, which this interface
+    /// technically forbids. But accessing the parent is only unsafe insofar as
+    /// it can be used to reach siblings and cousins. A simple immutable borrow
+    /// of the parent data is fine, since the bottom-up traversal will not process
+    /// the parent until all the children have been processed.
+    fn is_body_element_of_html_element_root(&self) -> bool;
+}