layout: Flatten inline box storage in InlineFormattingContexts (#32539)

This accomplishes two things:

1. Makes it easier to iterate through all inline formatting context
   items.
2. Will make it possible to easily move back and forth through the tree
   of inline boxes, in order to enable reordering and splitting inline
   boxes on lines -- necessary for BiDi.

Co-authored-by: Rakhi Sharma <atbrakhi@igalia.com>

1 files changed, 14 insertions, 9 deletions

diff --git a/components/layout_2020/flow/construct.rs b/components/layout_2020/flow/construct.rs
index bba6e2eec1f..3e9cb63b224 100644
--- a/components/layout_2020/flow/construct.rs
+++ b/components/layout_2020/flow/construct.rs
@@ -14,6 +14,7 @@ use style::str::char_is_whitespace;
 use style::values::specified::text::TextDecorationLine;
 
 use super::inline::construct::InlineFormattingContextBuilder;
+use super::inline::{InlineBox, InlineFormattingContext};
 use super::OutsideMarker;
 use crate::cell::ArcRefCell;
 use crate::context::LayoutContext;
@@ -22,7 +23,6 @@ use crate::dom_traversal::{
     Contents, NodeAndStyleInfo, NonReplacedContents, PseudoElementContentItem, TraversalHandler,
 };
 use crate::flow::float::FloatBox;
-use crate::flow::inline::{InlineFormattingContext, InlineLevelBox};
 use crate::flow::{BlockContainer, BlockFormattingContext, BlockLevelBox};
 use crate::formatting_contexts::IndependentFormattingContext;
 use crate::positioned::AbsolutelyPositionedBox;
@@ -325,9 +325,9 @@ where
                 self.finish_anonymous_table_if_needed();
 
                 match outside {
-                    DisplayOutside::Inline => box_slot.set(LayoutBox::InlineLevel(
-                        self.handle_inline_level_element(info, inside, contents),
-                    )),
+                    DisplayOutside::Inline => {
+                        self.handle_inline_level_element(info, inside, contents, box_slot)
+                    },
                     DisplayOutside::Block => {
                         let box_style = info.style.get_box();
                         // Floats and abspos cause blockification, so they only happen in this case.
@@ -400,6 +400,7 @@ where
                 is_list_item: false,
             },
             Contents::OfPseudoElement(contents),
+            BoxSlot::dummy(),
         );
     }
 
@@ -420,12 +421,13 @@ where
         info: &NodeAndStyleInfo<Node>,
         display_inside: DisplayInside,
         contents: Contents,
-    ) -> ArcRefCell<InlineLevelBox> {
+        box_slot: BoxSlot<'dom>,
+    ) {
         let (DisplayInside::Flow { is_list_item }, false) =
             (display_inside, contents.is_replaced())
         else {
             // If this inline element is an atomic, handle it and return.
-            return self.inline_formatting_context_builder.push_atomic(
+            let atomic = self.inline_formatting_context_builder.push_atomic(
                 IndependentFormattingContext::construct(
                     self.context,
                     info,
@@ -435,12 +437,14 @@ where
                     TextDecorationLine::NONE,
                 ),
             );
+            box_slot.set(LayoutBox::InlineLevel(atomic));
+            return;
         };
 
         // Otherwise, this is just a normal inline box. Whatever happened before, all we need to do
         // before recurring is to remember this ongoing inline level box.
         self.inline_formatting_context_builder
-            .start_inline_box(info);
+            .start_inline_box(InlineBox::new(info));
 
         if is_list_item {
             if let Some(marker_contents) = crate::lists::make_marker(self.context, info) {
@@ -458,8 +462,9 @@ where
 
         self.finish_anonymous_table_if_needed();
 
-        // Finish the inline box in our IFC builder and return it for `display: contents`.
-        self.inline_formatting_context_builder.end_inline_box()
+        box_slot.set(LayoutBox::InlineBox(
+            self.inline_formatting_context_builder.end_inline_box(),
+        ));
     }
 
     fn handle_block_level_element(