2020: run layout after box construction

components/layout_2020/flow/mod.rs

@@ -27,7 +27,7 @@ mod float;
 pub mod inline;
 mod root;
 
-pub use root::BoxTreeRoot;
+pub use root::{BoxTreeRoot, FragmentTreeRoot};
 
 #[derive(Debug)]
 pub(crate) struct BlockFormattingContext {

components/layout_2020/flow/root.rs

@@ -23,6 +23,7 @@ use style::values::computed::{Length, LengthOrAuto};
 use style_traits::CSSPixel;
 
 pub struct BoxTreeRoot(BlockFormattingContext);
+pub struct FragmentTreeRoot(Vec<Fragment>);
 
 impl BoxTreeRoot {
     pub fn construct<'dom>(
@@ -95,7 +96,7 @@ fn construct_for_root_element<'dom>(
 }
 
 impl BoxTreeRoot {
-    fn layout(&self, viewport: geom::Size<CSSPixel>) -> Vec<Fragment> {
+    pub fn layout(&self, viewport: geom::Size<CSSPixel>) -> FragmentTreeRoot {
         let initial_containing_block_size = Vec2 {
             inline: Length::new(viewport.width),
             block: Length::new(viewport.height),
@@ -125,6 +126,6 @@ impl BoxTreeRoot {
                 .par_iter()
                 .map(|a| a.layout(&initial_containing_block)),
         );
-        flow_children.fragments
+        FragmentTreeRoot(flow_children.fragments)
     }
 }

components/layout_2020/lib.rs

@@ -30,7 +30,7 @@ mod style_ext;
 pub mod traversal;
 pub mod wrapper;
 
-pub use flow::BoxTreeRoot;
+pub use flow::{BoxTreeRoot, FragmentTreeRoot};
 
 use crate::dom_traversal::{Contents, NodeExt};
 use crate::flow::{BlockFormattingContext, FlowChildren};

components/layout_thread_2020/lib.rs

@@ -167,8 +167,11 @@ pub struct LayoutThread {
     /// The number of Web fonts that have been requested but not yet loaded.
     outstanding_web_fonts: Arc<AtomicUsize>,
 
-    /// The root box tree.
-    box_tree_root: RefCell<Option<BoxTreeRoot>>,
+    /// The root of the box tree.
+    box_tree_root: RefCell<Option<layout::BoxTreeRoot>>,
+
+    /// The root of the fragment tree.
+    fragment_tree_root: RefCell<Option<layout::FragmentTreeRoot>>,
 
     /// The document-specific shared lock used for author-origin stylesheets
     document_shared_lock: Option<SharedRwLock>,
@@ -497,6 +500,7 @@ impl LayoutThread {
             _new_animations_receiver: new_animations_receiver,
             outstanding_web_fonts: Arc::new(AtomicUsize::new(0)),
             box_tree_root: Default::default(),
+            fragment_tree_root: Default::default(),
             document_shared_lock: None,
             epoch: Cell::new(Epoch(0)),
             viewport_size: Size2D::new(Au(0), Au(0)),
@@ -1084,7 +1088,12 @@ impl LayoutThread {
             let shared = DomTraversal::<ServoLayoutElement>::shared_context(&traversal);
             let box_tree =
                 BoxTreeRoot::construct(shared, document.root_element().unwrap().as_node());
+            let fragment_tree = box_tree.layout(Size2D::new(
+                self.viewport_size.width.to_f32_px(),
+                self.viewport_size.height.to_f32_px(),
+            ));
             *self.box_tree_root.borrow_mut() = Some(box_tree);
+            *self.fragment_tree_root.borrow_mut() = Some(fragment_tree);
         }
 
         for element in elements_with_snapshot {