Make OpaqueLayoutAndStyleData just a bit less opaque

It now stores a NonNull<dyn Any>.

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
+    /// The style data associated with a node.
-    /// casting between StyleAndLayoutData and StyleData.
     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;
@@ -1037,8 +1037,13 @@ fn inner_text_collection_steps<'dom>(
         };
 
         let element_data = unsafe {
-            node.get_style_and_layout_data()
+            &node.get_style_and_layout_data().as_ref().map(|opaque| {
-                .map(|d| &(*(d.ptr.as_ptr() as *mut StyleData)).element_data)
+                &opaque
+                    .downcast_ref::<StyleAndLayoutData>()
+                    .unwrap()
+                    .style_data
+                    .element_data
+            })
         };
 
         if element_data.is_none() {

components/layout/traversal.rs

@@ -73,7 +73,7 @@ where
         // flow construction:
         // (1) They child doesn't yet have layout data (preorder traversal initializes it).
         // (2) The parent element has restyle damage (so the text flow also needs fixup).
-        node.get_raw_data().is_none() || !parent_data.damage.is_empty()
+        (unsafe { node.get_raw_data().is_none() }) || !parent_data.damage.is_empty()
     }
 
     fn shared_context(&self) -> &SharedStyleContext {

components/layout/wrapper.rs

@@ -52,11 +52,11 @@ where
     T: GetLayoutData<'dom>,
 {
     fn borrow_layout_data(&self) -> Option<AtomicRef<LayoutData>> {
-        self.get_raw_data().map(|d| d.layout_data.borrow())
+        unsafe { self.get_raw_data().map(|d| d.layout_data.borrow()) }
     }
 
     fn mutate_layout_data(&self) -> Option<AtomicRefMut<LayoutData>> {
-        self.get_raw_data().map(|d| d.layout_data.borrow_mut())
+        unsafe { self.get_raw_data().map(|d| d.layout_data.borrow_mut()) }
     }
 
     fn flow_debug_id(self) -> usize {
@@ -66,18 +66,16 @@ where
 }
 
 pub trait GetRawData {
-    fn get_raw_data(&self) -> Option<&StyleAndLayoutData>;
+    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData>;
 }
 
 impl<'dom, T> GetRawData for T
 where
     T: GetLayoutData<'dom>,
 {
-    fn get_raw_data(&self) -> Option<&StyleAndLayoutData> {
+    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData> {
-        self.get_style_and_layout_data().map(|opaque| {
+        self.get_style_and_layout_data()
-            let container = opaque.ptr.as_ptr() as *mut StyleAndLayoutData;
+            .map(|opaque| opaque.downcast_ref().unwrap())
-            unsafe { &*container }
-        })
     }
 }
 
@@ -146,7 +144,7 @@ where
             debug_assert!(node.is_element());
         }
 
-        let damage = {
+        let damage = unsafe {
             let data = node.get_raw_data().unwrap();
 
             if !data

components/layout_2020/dom_traversal.rs

@@ -446,10 +446,13 @@ where
         self.opaque()
     }
 
+    #[allow(unsafe_code)]
     fn layout_data_mut(&self) -> AtomicRefMut<LayoutDataForElement> {
-        self.get_raw_data()
+        unsafe {
-            .map(|d| d.layout_data.borrow_mut())
+            self.get_raw_data()
-            .unwrap()
+                .map(|d| d.layout_data.borrow_mut())
+                .unwrap()
+        }
     }
 
     fn element_box_slot(&self) -> BoxSlot<'dom> {

components/layout_2020/traversal.rs

@@ -63,7 +63,7 @@ where
     }
 
     fn text_node_needs_traversal(node: E::ConcreteNode, parent_data: &ElementData) -> bool {
-        node.get_raw_data().is_none() || !parent_data.damage.is_empty()
+        (unsafe { node.get_raw_data().is_none() }) || !parent_data.damage.is_empty()
     }
 
     fn shared_context(&self) -> &SharedStyleContext {

components/layout_2020/wrapper.rs

@@ -8,17 +8,15 @@ use crate::data::StyleAndLayoutData;
 use script_layout_interface::wrapper_traits::GetLayoutData;
 
 pub trait GetRawData {
-    fn get_raw_data(&self) -> Option<&StyleAndLayoutData>;
+    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData>;
 }
 
 impl<'dom, T> GetRawData for T
 where
     T: GetLayoutData<'dom>,
 {
-    fn get_raw_data(&self) -> Option<&StyleAndLayoutData> {
+    unsafe fn get_raw_data(&self) -> Option<&StyleAndLayoutData> {
-        self.get_style_and_layout_data().map(|opaque| {
+        self.get_style_and_layout_data()
-            let container = opaque.ptr.as_ptr() as *mut StyleAndLayoutData;
+            .map(|opaque| opaque.downcast_ref().unwrap())
-            unsafe { &*container }
-        })
     }
 }

components/layout_thread/dom_wrapper.rs

@@ -70,7 +70,6 @@ use std::borrow::Cow;
 use std::fmt;
 use std::fmt::Debug;
 use std::hash::{Hash, Hasher};
-use std::ptr::NonNull;
 use std::sync::atomic::Ordering;
 use std::sync::Arc as StdArc;
 use style::applicable_declarations::ApplicableDeclarationBlock;
@@ -93,9 +92,7 @@ use style::stylist::CascadeData;
 use style::CaseSensitivityExt;
 
 pub unsafe fn drop_style_and_layout_data(data: OpaqueStyleAndLayoutData) {
-    let ptr = data.ptr.as_ptr() as *mut StyleData;
+    drop(Box::from_raw(data.as_ptr()));
-    let non_opaque: *mut StyleAndLayoutData = ptr as *mut _;
-    let _ = Box::from_raw(non_opaque);
 }
 
 #[derive(Clone, Copy)]
@@ -276,10 +273,7 @@ impl<'ln> LayoutNode<'ln> for ServoLayoutNode<'ln> {
 
     unsafe fn initialize_data(&self) {
         if self.get_raw_data().is_none() {
-            let ptr: *mut StyleAndLayoutData = Box::into_raw(Box::new(StyleAndLayoutData::new()));
+            let opaque = OpaqueStyleAndLayoutData::new(StyleAndLayoutData::new());
-            let opaque = OpaqueStyleAndLayoutData {
-                ptr: NonNull::new_unchecked(ptr as *mut StyleData),
-            };
             self.init_style_and_layout_data(opaque);
         };
     }
@@ -558,10 +552,7 @@ impl<'le> TElement for ServoLayoutElement<'le> {
     }
 
     fn get_data(&self) -> Option<&AtomicRefCell<ElementData>> {
-        unsafe {
+        self.get_style_data().map(|data| &data.element_data)
-            self.get_style_and_layout_data()
-                .map(|d| &(*(d.ptr.as_ptr() as *mut StyleData)).element_data)
-        }
     }
 
     fn skip_item_display_fixup(&self) -> bool {
@@ -697,10 +688,12 @@ impl<'le> ServoLayoutElement<'le> {
     }
 
     fn get_style_data(&self) -> Option<&StyleData> {
-        unsafe {
+        self.get_style_and_layout_data().map(|opaque| {
-            self.get_style_and_layout_data()
+            &opaque
-                .map(|d| &*(d.ptr.as_ptr() as *mut StyleData))
+                .downcast_ref::<StyleAndLayoutData>()
-        }
+                .unwrap()
+                .style_data
+        })
     }
 
     pub unsafe fn unset_snapshot_flags(&self) {

components/layout_thread_2020/dom_wrapper.rs

@@ -70,7 +70,6 @@ use std::borrow::Cow;
 use std::fmt;
 use std::fmt::Debug;
 use std::hash::{Hash, Hasher};
-use std::ptr::NonNull;
 use std::sync::atomic::Ordering;
 use std::sync::Arc as StdArc;
 use style::applicable_declarations::ApplicableDeclarationBlock;
@@ -93,9 +92,7 @@ use style::stylist::CascadeData;
 use style::CaseSensitivityExt;
 
 pub unsafe fn drop_style_and_layout_data(data: OpaqueStyleAndLayoutData) {
-    let ptr = data.ptr.as_ptr() as *mut StyleData;
+    drop(Box::from_raw(data.as_ptr()));
-    let non_opaque: *mut StyleAndLayoutData = ptr as *mut _;
-    let _ = Box::from_raw(non_opaque);
 }
 
 #[derive(Clone, Copy)]
@@ -283,10 +280,7 @@ impl<'ln> LayoutNode<'ln> for ServoLayoutNode<'ln> {
 
     unsafe fn initialize_data(&self) {
         if self.get_raw_data().is_none() {
-            let ptr: *mut StyleAndLayoutData = Box::into_raw(Box::new(StyleAndLayoutData::new()));
+            let opaque = OpaqueStyleAndLayoutData::new(StyleAndLayoutData::new());
-            let opaque = OpaqueStyleAndLayoutData {
-                ptr: NonNull::new_unchecked(ptr as *mut StyleData),
-            };
             self.init_style_and_layout_data(opaque);
         };
     }
@@ -565,10 +559,7 @@ impl<'le> TElement for ServoLayoutElement<'le> {
     }
 
     fn get_data(&self) -> Option<&AtomicRefCell<ElementData>> {
-        unsafe {
+        self.get_style_data().map(|data| &data.element_data)
-            self.get_style_and_layout_data()
-                .map(|d| &(*(d.ptr.as_ptr() as *mut StyleData)).element_data)
-        }
     }
 
     fn skip_item_display_fixup(&self) -> bool {
@@ -704,10 +695,12 @@ impl<'le> ServoLayoutElement<'le> {
     }
 
     fn get_style_data(&self) -> Option<&StyleData> {
-        unsafe {
+        self.get_style_and_layout_data().map(|opaque| {
-            self.get_style_and_layout_data()
+            &opaque
-                .map(|d| &*(d.ptr.as_ptr() as *mut StyleData))
+                .downcast_ref::<StyleAndLayoutData>()
-        }
+                .unwrap()
+                .style_data
+        })
     }
 
     pub unsafe fn unset_snapshot_flags(&self) {

components/script_layout_interface/lib.rs

@@ -7,6 +7,7 @@
 //! to depend on script.
 
 #![deny(unsafe_code)]
+#![feature(box_into_raw_non_null)]
 
 #[macro_use]
 extern crate html5ever;
@@ -24,6 +25,7 @@ use libc::c_void;
 use net_traits::image_cache::PendingImageId;
 use script_traits::UntrustedNodeAddress;
 use servo_url::{ImmutableOrigin, ServoUrl};
+use std::any::Any;
 use std::ptr::NonNull;
 use std::sync::atomic::AtomicIsize;
 use style::data::ElementData;
@@ -54,7 +56,34 @@ pub struct OpaqueStyleAndLayoutData {
     // NB: We really store a `StyleAndLayoutData` here, so be careful!
     #[ignore_malloc_size_of = "TODO(#6910) Box value that should be counted but \
                                the type lives in layout"]
-    pub ptr: NonNull<StyleData>,
+    ptr: NonNull<dyn Any + Send + Sync>,
+}
+
+impl OpaqueStyleAndLayoutData {
+    #[inline]
+    pub fn new<T>(value: T) -> Self
+    where
+        T: Any + Send + Sync,
+    {
+        Self {
+            ptr: Box::into_raw_non_null(Box::new(value) as Box<dyn Any + Send + Sync>),
+        }
+    }
+
+    #[inline]
+    pub fn as_ptr(&self) -> *mut (dyn Any + Send + Sync) {
+        self.ptr.as_ptr()
+    }
+
+    /// Extremely cursed.
+    #[allow(unsafe_code)]
+    #[inline]
+    pub unsafe fn downcast_ref<'extended, T>(&self) -> Option<&'extended T>
+    where
+        T: Any + Send + Sync,
+    {
+        (*self.ptr.as_ptr()).downcast_ref()
+    }
 }
 
 #[allow(unsafe_code)]

tests/unit/script/size_of.rs

@@ -30,10 +30,10 @@ macro_rules! sizeof_checker (
 
 // Update the sizes here
 sizeof_checker!(size_event_target, EventTarget, 56);
-sizeof_checker!(size_node, Node, 176);
+sizeof_checker!(size_node, Node, 184);
-sizeof_checker!(size_element, Element, 352);
+sizeof_checker!(size_element, Element, 360);
-sizeof_checker!(size_htmlelement, HTMLElement, 368);
+sizeof_checker!(size_htmlelement, HTMLElement, 376);
-sizeof_checker!(size_div, HTMLDivElement, 368);
+sizeof_checker!(size_div, HTMLDivElement, 376);
-sizeof_checker!(size_span, HTMLSpanElement, 368);
+sizeof_checker!(size_span, HTMLSpanElement, 376);
-sizeof_checker!(size_text, Text, 208);
+sizeof_checker!(size_text, Text, 216);
-sizeof_checker!(size_characterdata, CharacterData, 208);
+sizeof_checker!(size_characterdata, CharacterData, 216);