Pass the document instead of the documentElement to reflow.

components/layout/layout_task.rs

@@ -52,6 +52,7 @@ use query::{LayoutRPCImpl, process_content_box_request, process_content_boxes_re
 use query::{MarginPadding, MarginRetrievingFragmentBorderBoxIterator, PositionProperty};
 use query::{PositionRetrievingFragmentBorderBoxIterator, Side};
 use script::dom::bindings::js::LayoutJS;
+use script::dom::document::Document;
 use script::dom::node::{LayoutData, Node};
 use script::layout_interface::Animation;
 use script::layout_interface::{LayoutChan, LayoutRPC, OffsetParentResponse};
@@ -89,8 +90,7 @@ use util::opts;
 use util::task::spawn_named_with_send_on_failure;
 use util::task_state;
 use util::workqueue::WorkQueue;
-use wrapper::LayoutNode;
-use wrapper::ThreadSafeLayoutNode;
+use wrapper::{LayoutDocument, LayoutNode, ThreadSafeLayoutNode};
 
 /// The number of screens of data we're allowed to generate display lists for in each direction.
 pub const DISPLAY_PORT_SIZE_FACTOR: i32 = 8;
@@ -1137,13 +1137,16 @@ impl LayoutTask {
         let _ajst = AutoJoinScriptTask { data: data };
 
         // FIXME: Isolate this transmutation into a "bridge" module.
-        // FIXME(rust#16366): The following line had to be moved because of a
-        // rustc bug. It should be in the next unsafe block.
-        let mut node: LayoutJS<Node> = unsafe {
-            LayoutJS::from_trusted_node_address(data.document_root)
+        let mut doc: LayoutJS<Document> = unsafe {
+            LayoutJS::from_trusted_node_address(data.document).downcast::<Document>().unwrap()
         };
-        let node: &mut LayoutNode = unsafe {
-            transmute(&mut node)
+        let doc: &mut LayoutDocument = unsafe {
+            transmute(&mut doc)
+        };
+
+        let mut node: LayoutNode = match doc.root_node() {
+            None => return,
+            Some(x) => x,
         };
 
         debug!("layout: received layout request for: {}", self.url.serialize());
@@ -1187,11 +1190,11 @@ impl LayoutTask {
         let needs_reflow = screen_size_changed && !needs_dirtying;
         unsafe {
             if needs_dirtying {
-                LayoutTask::dirty_all_nodes(node);
+                LayoutTask::dirty_all_nodes(&mut node);
             }
         }
         if needs_reflow {
-            if let Some(mut flow) = self.try_get_layout_root(*node) {
+            if let Some(mut flow) = self.try_get_layout_root(node) {
                 LayoutTask::reflow_all_nodes(flow_ref::deref_mut(&mut flow));
             }
         }
@@ -1213,16 +1216,16 @@ impl LayoutTask {
                 let rw_data = &mut *rw_data;
                 match rw_data.parallel_traversal {
                     None => {
-                        sequential::traverse_dom_preorder(*node, &shared_layout_context);
+                        sequential::traverse_dom_preorder(node, &shared_layout_context);
                     }
                     Some(ref mut traversal) => {
-                        parallel::traverse_dom_preorder(*node, &shared_layout_context, traversal);
+                        parallel::traverse_dom_preorder(node, &shared_layout_context, traversal);
                     }
                 }
             });
 
             // Retrieve the (possibly rebuilt) root flow.
-            rw_data.root_flow = self.try_get_layout_root((*node).clone());
+            rw_data.root_flow = self.try_get_layout_root(node.clone());
         }
 
         // Send new canvas renderers to the paint task

components/layout/wrapper.rs

@@ -43,6 +43,7 @@ use script::dom::bindings::codegen::InheritTypes::{HTMLElementTypeId, NodeTypeId
 use script::dom::bindings::conversions::Castable;
 use script::dom::bindings::js::LayoutJS;
 use script::dom::characterdata::LayoutCharacterDataHelpers;
+use script::dom::document::{Document, LayoutDocumentHelpers};
 use script::dom::element;
 use script::dom::element::{Element, LayoutElementHelpers, RawLayoutElementHelpers};
 use script::dom::htmlcanvaselement::{LayoutHTMLCanvasElementHelpers, HTMLCanvasData};
@@ -105,6 +106,12 @@ impl<'ln> LayoutNode<'ln> {
         }
     }
 
+    pub fn is_element(&self) -> bool {
+        unsafe {
+            self.node.is_element_for_layout()
+        }
+    }
+
     pub fn dump(self) {
         self.dump_indent(0);
     }
@@ -336,6 +343,30 @@ impl<'a> Iterator for LayoutTreeIterator<'a> {
     }
 }
 
+// A wrapper around documents that ensures ayout can only ever access safe properties.
+#[derive(Copy, Clone)]
+pub struct LayoutDocument<'le> {
+    document: LayoutJS<Document>,
+    chain: PhantomData<&'le ()>,
+}
+
+impl<'le> LayoutDocument<'le> {
+    pub fn as_node(&self) -> LayoutNode<'le> {
+        LayoutNode {
+            node: self.document.upcast(),
+            chain: PhantomData,
+        }
+    }
+
+    pub fn root_node(&self) -> Option<LayoutNode<'le>> {
+        let mut node = self.as_node().first_child();
+        while node.is_some() && !node.unwrap().is_element() {
+            node = node.unwrap().next_sibling();
+        }
+        node
+    }
+}
+
 /// A wrapper around elements that ensures layout can only ever access safe properties.
 #[derive(Copy, Clone)]
 pub struct LayoutElement<'le> {

components/script/dom/document.rs

@@ -1175,15 +1175,14 @@ pub enum DocumentSource {
     NotFromParser,
 }
 
+#[allow(unsafe_code)]
 pub trait LayoutDocumentHelpers {
-    #[allow(unsafe_code)]
     unsafe fn is_html_document_for_layout(&self) -> bool;
 }
 
+#[allow(unsafe_code)]
 impl LayoutDocumentHelpers for LayoutJS<Document> {
-    #[allow(unrooted_must_root)]
     #[inline]
-    #[allow(unsafe_code)]
     unsafe fn is_html_document_for_layout(&self) -> bool {
         (*self.unsafe_get()).is_html_document
     }

components/script/dom/window.rs

@@ -885,14 +885,6 @@ impl Window {
     ///
     /// TODO(pcwalton): Only wait for style recalc, since we have off-main-thread layout.
     pub fn force_reflow(&self, goal: ReflowGoal, query_type: ReflowQueryType, reason: ReflowReason) {
-        let document = self.Document();
-        let root = document.r().GetDocumentElement();
-        let root = match root.r() {
-            Some(root) => root,
-            None => return,
-        };
-        let root = root.upcast::<Node>();
-
         let window_size = match self.window_size.get() {
             Some(window_size) => window_size,
             None => return,
@@ -923,7 +915,7 @@ impl Window {
                 goal: goal,
                 page_clip_rect: self.page_clip_rect.get(),
             },
-            document_root: root.to_trusted_node_address(),
+            document: self.Document().r().upcast::<Node>().to_trusted_node_address(),
             window_size: window_size,
             script_chan: self.control_chan.clone(),
             script_join_chan: join_chan,

components/script/layout_interface.rs

@@ -174,7 +174,7 @@ pub struct ScriptReflow {
     /// General reflow data.
     pub reflow_info: Reflow,
     /// The document node.
-    pub document_root: TrustedNodeAddress,
+    pub document: TrustedNodeAddress,
     /// The channel through which messages can be sent back to the script task.
     pub script_chan: Sender<ConstellationControlMsg>,
     /// The current window size.