Auto merge of #26833 - servo:layout-2020-arcrefcell-abspos, r=SimonSapin

Store abspos boxes in a RefCell too

We want to mutate them when lazily computing their content sizes, but they
are behind an Arc for the hoisting infra, so it also needs its own layer
of inner mutability.

1 files changed, 5 insertions, 3 deletions

diff --git a/components/layout_2020/flow/inline.rs b/components/layout_2020/flow/inline.rs
index f3d0e45e3b7..47d9deacfbf 100644
--- a/components/layout_2020/flow/inline.rs
+++ b/components/layout_2020/flow/inline.rs
@@ -20,6 +20,7 @@ use crate::sizing::ContentSizes;
 use crate::style_ext::{ComputedValuesExt, Display, DisplayGeneratingBox, DisplayOutside};
 use crate::ContainingBlock;
 use app_units::Au;
+use atomic_refcell::AtomicRef;
 use gfx::text::text_run::GlyphRun;
 use servo_arc::Arc;
 use style::properties::ComputedValues;
@@ -39,7 +40,7 @@ pub(crate) struct InlineFormattingContext {
 pub(crate) enum InlineLevelBox {
     InlineBox(InlineBox),
     TextRun(TextRun),
-    OutOfFlowAbsolutelyPositionedBox(Arc<AbsolutelyPositionedBox>),
+    OutOfFlowAbsolutelyPositionedBox(ArcRefCell<AbsolutelyPositionedBox>),
     OutOfFlowFloatBox(FloatBox),
     Atomic(IndependentFormattingContext),
 }
@@ -283,8 +284,9 @@ impl InlineFormattingContext {
                     InlineLevelBox::TextRun(run) => run.layout(layout_context, &mut ifc),
                     InlineLevelBox::Atomic(a) => layout_atomic(layout_context, &mut ifc, a),
                     InlineLevelBox::OutOfFlowAbsolutelyPositionedBox(box_) => {
+                        let style = AtomicRef::map(box_.borrow(), |box_| &box_.contents.style);
                         let initial_start_corner =
-                            match Display::from(box_.contents.style.get_box().original_display) {
+                            match Display::from(style.get_box().original_display) {
                                 Display::GeneratingBox(DisplayGeneratingBox::OutsideInside {
                                     outside,
                                     inside: _,
@@ -313,7 +315,7 @@ impl InlineFormattingContext {
                             Fragment::AbsoluteOrFixedPositioned(
                                 AbsoluteOrFixedPositionedFragment {
                                     hoisted_fragment,
-                                    position: box_.contents.style.clone_position(),
+                                    position: style.clone_position(),
                                 },
                             ),
                         );