Auto merge of #26105 - servo:layout-2020-less-opaque, r=emilio

Make DOM own the style and layout data, in an UnsafeCell

components/layout/data.rs

@@ -8,8 +8,7 @@ use script_layout_interface::StyleData;
 
 #[repr(C)]
 pub struct StyleAndLayoutData {
-    /// Data accessed by script_layout_interface. This must be first to allow
-    /// casting between StyleAndLayoutData and StyleData.
+    /// The style data associated with a node.
     pub style_data: StyleData,
     /// The layout data associated with a node.
     pub layout_data: AtomicRefCell<LayoutData>,

components/layout/query.rs

@@ -6,6 +6,7 @@
 
 use crate::construct::ConstructionResult;
 use crate::context::LayoutContext;
+use crate::data::StyleAndLayoutData;
 use crate::display_list::items::{DisplayList, OpaqueNode, ScrollOffsetMap};
 use crate::display_list::IndexableText;
 use crate::flow::{Flow, GetBaseFlow};
@@ -26,7 +27,6 @@ use script_layout_interface::rpc::{OffsetParentResponse, ResolvedStyleResponse,
 use script_layout_interface::wrapper_traits::{
     LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode,
 };
-use script_layout_interface::StyleData;
 use script_layout_interface::{LayoutElementType, LayoutNodeType};
 use script_traits::LayoutMsg as ConstellationMsg;
 use script_traits::UntrustedNodeAddress;
@@ -761,7 +761,7 @@ pub fn process_resolved_style_request<'dom>(
 
     // We call process_resolved_style_request after performing a whole-document
     // traversal, so in the common case, the element is styled.
-    if element.get_data().is_some() {
+    if element.has_data() {
         return process_resolved_style_request_internal(node, pseudo, property, layout_root);
     }
 
@@ -1036,9 +1036,14 @@ fn inner_text_collection_steps<'dom>(
             _ => child,
         };
 
-        let element_data = unsafe {
-            node.get_style_and_layout_data()
-                .map(|d| &(*(d.ptr.as_ptr() as *mut StyleData)).element_data)
+        let element_data = {
+            &node.get_style_and_layout_data().as_ref().map(|opaque| {
+                &opaque
+                    .downcast_ref::<StyleAndLayoutData>()
+                    .unwrap()
+                    .style_data
+                    .element_data
+            })
         };
 
         if element_data.is_none() {

components/layout/wrapper.rs

@@ -39,23 +39,21 @@ use style::selector_parser::RestyleDamage;
 use style::values::computed::counters::ContentItem;
 use style::values::generics::counters::Content;
 
-pub trait LayoutNodeLayoutData {
-    /// Similar to borrow_data*, but returns the full PersistentLayoutData rather
-    /// than only the style::data::ElementData.
-    fn borrow_layout_data(&self) -> Option<AtomicRef<LayoutData>>;
-    fn mutate_layout_data(&self) -> Option<AtomicRefMut<LayoutData>>;
+pub trait LayoutNodeLayoutData<'dom> {
+    fn borrow_layout_data(self) -> Option<AtomicRef<'dom, LayoutData>>;
+    fn mutate_layout_data(self) -> Option<AtomicRefMut<'dom, LayoutData>>;
     fn flow_debug_id(self) -> usize;
 }
 
-impl<'dom, T> LayoutNodeLayoutData for T
+impl<'dom, T> LayoutNodeLayoutData<'dom> for T
 where
     T: GetLayoutData<'dom>,
 {
-    fn borrow_layout_data(&self) -> Option<AtomicRef<LayoutData>> {
+    fn borrow_layout_data(self) -> Option<AtomicRef<'dom, LayoutData>> {
         self.get_raw_data().map(|d| d.layout_data.borrow())
     }
 
-    fn mutate_layout_data(&self) -> Option<AtomicRefMut<LayoutData>> {
+    fn mutate_layout_data(self) -> Option<AtomicRefMut<'dom, LayoutData>> {
         self.get_raw_data().map(|d| d.layout_data.borrow_mut())
     }
 
@@ -65,19 +63,17 @@ where
     }
 }
 
-pub trait GetRawData {
-    fn get_raw_data(&self) -> Option<&StyleAndLayoutData>;
+pub trait GetRawData<'dom> {
+    fn get_raw_data(self) -> Option<&'dom StyleAndLayoutData>;
 }
 
-impl<'dom, T> GetRawData for T
+impl<'dom, T> GetRawData<'dom> for T
 where
     T: GetLayoutData<'dom>,
 {
-    fn get_raw_data(&self) -> Option<&StyleAndLayoutData> {
-        self.get_style_and_layout_data().map(|opaque| {
-            let container = opaque.ptr.as_ptr() as *mut StyleAndLayoutData;
-            unsafe { &*container }
-        })
+    fn get_raw_data(self) -> Option<&'dom StyleAndLayoutData> {
+        self.get_style_and_layout_data()
+            .map(|opaque| opaque.downcast_ref().unwrap())
     }
 }