Create HoistedSharedFragment

components/layout_2020/display_list/stacking_context.rs

@@ -916,7 +916,7 @@ impl AbsoluteOrFixedPositionedFragment {
         stacking_context: &mut StackingContext,
     ) {
         let hoisted_fragment = self.hoisted_fragment.borrow();
-        let fragment_ref = match hoisted_fragment.as_ref() {
+        let fragment_ref = match hoisted_fragment.fragment.as_ref() {
             Some(fragment_ref) => fragment_ref,
             None => unreachable!("Found hoisted box with missing fragment."),
         };

components/layout_2020/fragments.rs

@@ -8,6 +8,7 @@ use crate::geom::flow_relative::{Rect, Sides};
 use crate::geom::{PhysicalPoint, PhysicalRect};
 #[cfg(debug_assertions)]
 use crate::layout_debug;
+use crate::positioned::HoistedSharedFragment;
 use gfx::font::FontMetrics as GfxFontMetrics;
 use gfx::text::glyph::GlyphStore;
 use gfx_traits::print_tree::PrintTree;
@@ -74,7 +75,7 @@ pub(crate) enum Fragment {
 #[derive(Serialize)]
 pub(crate) struct AbsoluteOrFixedPositionedFragment {
     pub position: ComputedPosition,
-    pub hoisted_fragment: ArcRefCell<Option<ArcRefCell<Fragment>>>,
+    pub hoisted_fragment: ArcRefCell<HoistedSharedFragment>,
 }
 
 #[derive(Serialize)]

components/layout_2020/positioned.rs

@@ -46,7 +46,21 @@ pub(crate) struct HoistedAbsolutelyPositionedBox {
     /// A reference to a Fragment which is shared between this `HoistedAbsolutelyPositionedBox`
     /// and its placeholder `AbsoluteOrFixedPositionedFragment` in the original tree position.
     /// This will be used later in order to paint this hoisted box in tree order.
-    pub fragment: ArcRefCell<Option<ArcRefCell<Fragment>>>,
+    pub fragment: ArcRefCell<HoistedSharedFragment>,
+}
+
+/// A reference to a Fragment which is shared between `HoistedAbsolutelyPositionedBox`
+/// and its placeholder `AbsoluteOrFixedPositionedFragment` in the original tree position.
+/// This will be used later in order to paint this hoisted box in tree order.
+#[derive(Serialize)]
+pub(crate) struct HoistedSharedFragment {
+    pub fragment: Option<ArcRefCell<Fragment>>,
+}
+
+impl HoistedSharedFragment {
+    pub(crate) fn new() -> Self {
+        HoistedSharedFragment { fragment: None }
+    }
 }
 
 impl HoistedAbsolutelyPositionedBox {
@@ -79,8 +93,8 @@ pub(crate) enum AbsoluteBoxOffsets {
 impl AbsoluteBoxOffsets {
     fn adjust_offset(&mut self, new_offset: Length) {
         match *self {
-            AbsoluteBoxOffsets::StaticStart {ref mut start} => *start = new_offset,
-            _ => ()
+            AbsoluteBoxOffsets::StaticStart { ref mut start } => *start = new_offset,
+            _ => (),
         }
     }
 }
@@ -149,7 +163,7 @@ impl AbsolutelyPositionedBox {
         HoistedAbsolutelyPositionedBox {
             tree_rank,
             box_offsets,
-            fragment: ArcRefCell::new(None),
+            fragment: ArcRefCell::new(HoistedSharedFragment::new()),
             absolutely_positioned_box: self_,
         }
     }
@@ -376,7 +390,7 @@ impl HoistedAbsolutelyPositionedBox {
                         containing_block,
                     )));
 
-                    *box_.fragment.borrow_mut() = Some(new_fragment.clone());
+                    box_.fragment.borrow_mut().fragment = Some(new_fragment.clone());
                     new_fragment
                 },
                 Vec::new,
@@ -389,7 +403,7 @@ impl HoistedAbsolutelyPositionedBox {
                     for_nearest_containing_block_for_all_descendants,
                     containing_block,
                 )));
-                *box_.fragment.borrow_mut() = Some(new_fragment.clone());
+                box_.fragment.borrow_mut().fragment = Some(new_fragment.clone());
                 new_fragment
             }))
         }