layout: Box block_margins_collapsed_with_children member of BoxFragment (#36474)

This reduces the size of `BoxFragment` by around 20 bytes.

Testing: This just changes the layout of a data structure, so is
covered by existing WPT tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/layout_2020/flexbox/layout.rs

@@ -256,8 +256,6 @@ impl FlexLineItem<'_> {
                 size: item_used_size,
             },
         );
-        let margin = flex_context.sides_to_flow_relative(item_margin);
-        let collapsed_margin = CollapsedBlockMargins::from_margin(&margin);
 
         if let Some(item_baseline) = self.layout_result.baseline_relative_to_margin_box.as_ref() {
             let item_baseline = *item_baseline + item_content_cross_start_position -
@@ -294,9 +292,10 @@ impl FlexLineItem<'_> {
             flex_context
                 .sides_to_flow_relative(self.item.border)
                 .to_physical(container_writing_mode),
-            margin.to_physical(container_writing_mode),
+            flex_context
+                .sides_to_flow_relative(item_margin)
+                .to_physical(container_writing_mode),
             None, /* clearance */
-            collapsed_margin,
         );
 
         // If this flex item establishes a containing block for absolutely-positioned

components/layout_2020/flow/inline/line.rs

@@ -23,9 +23,7 @@ use webrender_api::FontInstanceKey;
 use super::inline_box::{InlineBoxContainerState, InlineBoxIdentifier, InlineBoxTreePathToken};
 use super::{InlineFormattingContextLayout, LineBlockSizes};
 use crate::cell::ArcRefCell;
-use crate::fragment_tree::{
+use crate::fragment_tree::{BaseFragmentInfo, BoxFragment, Fragment, TextFragment};
-    BaseFragmentInfo, BoxFragment, CollapsedBlockMargins, Fragment, TextFragment,
-};
 use crate::geom::{LogicalRect, LogicalVec2, PhysicalRect, ToLogical};
 use crate::positioned::{
     AbsolutelyPositionedBox, PositioningContext, PositioningContextLength, relative_adjustement,
@@ -465,7 +463,6 @@ impl LineItemLayout<'_, '_> {
             border.to_physical(ifc_writing_mode),
             margin.to_physical(ifc_writing_mode),
             None, /* clearance */
-            CollapsedBlockMargins::zero(),
         );
 
         let offset_from_parent_ifc = LogicalVec2 {

components/layout_2020/flow/mod.rs

@@ -355,7 +355,6 @@ impl OutsideMarker {
             PhysicalSides::zero(),
             PhysicalSides::zero(),
             None,
-            CollapsedBlockMargins::zero(),
         )))
     }
 }
@@ -1105,9 +1104,9 @@ fn layout_in_flow_non_replaced_block_level_same_formatting_context(
         pbm.border.to_physical(containing_block_writing_mode),
         margin.to_physical(containing_block_writing_mode),
         clearance,
-        block_margins_collapsed_with_children,
     )
     .with_baselines(flow_layout.baselines)
+    .with_block_margins_collapsed_with_children(block_margins_collapsed_with_children)
 }
 
 impl IndependentNonReplacedContents {
@@ -1211,10 +1210,10 @@ impl IndependentNonReplacedContents {
             pbm.border.to_physical(containing_block_writing_mode),
             margin.to_physical(containing_block_writing_mode),
             None, /* clearance */
-            block_margins_collapsed_with_children,
         )
         .with_baselines(layout.baselines)
         .with_specific_layout_info(layout.specific_layout_info)
+        .with_block_margins_collapsed_with_children(block_margins_collapsed_with_children)
     }
 
     /// Lay out a normal in flow non-replaced block that establishes an independent
@@ -1516,10 +1515,10 @@ impl IndependentNonReplacedContents {
             pbm.border.to_physical(containing_block_writing_mode),
             margin.to_physical(containing_block_writing_mode),
             clearance,
-            CollapsedBlockMargins::from_margin(&margin),
         )
         .with_baselines(layout.baselines)
         .with_specific_layout_info(layout.specific_layout_info)
+        .with_block_margins_collapsed_with_children(CollapsedBlockMargins::from_margin(&margin))
     }
 }
 
@@ -1653,8 +1652,8 @@ impl ReplacedContents {
             pbm.border.to_physical(containing_block_writing_mode),
             margin.to_physical(containing_block_writing_mode),
             clearance,
-            CollapsedBlockMargins::from_margin(&margin),
         )
+        .with_block_margins_collapsed_with_children(CollapsedBlockMargins::from_margin(&margin))
     }
 }
 
@@ -2038,7 +2037,7 @@ impl<'container> PlacementState<'container> {
                     return;
                 }
 
-                let fragment_block_margins = &fragment.block_margins_collapsed_with_children;
+                let fragment_block_margins = fragment.block_margins_collapsed_with_children();
                 let mut fragment_block_size = fragment
                     .border_rect()
                     .size
@@ -2352,7 +2351,6 @@ impl IndependentFormattingContext {
             // so there's no need to store it explicitly in the fragment.
             // And atomic inlines don't have clearance.
             None, /* clearance */
-            CollapsedBlockMargins::zero(),
         );
 
         IndependentFloatOrAtomicLayoutResult {

components/layout_2020/fragment_tree/box_fragment.rs

@@ -76,7 +76,7 @@ pub(crate) struct BoxFragment {
     /// to things such as tables and inline formatting contexts.
     baselines: Baselines,
 
-    pub block_margins_collapsed_with_children: CollapsedBlockMargins,
+    block_margins_collapsed_with_children: Option<Box<CollapsedBlockMargins>>,
 
     /// The scrollable overflow of this box fragment.
     pub scrollable_overflow_from_children: PhysicalRect<Au>,
@@ -103,7 +103,6 @@ impl BoxFragment {
         border: PhysicalSides<Au>,
         margin: PhysicalSides<Au>,
         clearance: Option<Au>,
-        block_margins_collapsed_with_children: CollapsedBlockMargins,
     ) -> BoxFragment {
         let scrollable_overflow_from_children =
             children.iter().fold(PhysicalRect::zero(), |acc, child| {
@@ -120,7 +119,7 @@ impl BoxFragment {
             margin,
             clearance,
             baselines: Baselines::default(),
-            block_margins_collapsed_with_children,
+            block_margins_collapsed_with_children: None,
             scrollable_overflow_from_children,
             resolved_sticky_insets: AtomicRefCell::default(),
             background_mode: BackgroundMode::Normal,
@@ -182,6 +181,14 @@ impl BoxFragment {
         self
     }
 
+    pub fn with_block_margins_collapsed_with_children(
+        mut self,
+        collapsed_margins: CollapsedBlockMargins,
+    ) -> Self {
+        self.block_margins_collapsed_with_children = Some(collapsed_margins.into());
+        self
+    }
+
     pub fn scrollable_overflow(&self) -> PhysicalRect<Au> {
         let physical_padding_rect = self.padding_rect();
         let content_origin = self.content_rect.origin.to_vector();
@@ -374,4 +381,11 @@ impl BoxFragment {
             _ => false,
         }
     }
+
+    pub(crate) fn block_margins_collapsed_with_children(&self) -> CollapsedBlockMargins {
+        match self.block_margins_collapsed_with_children.as_ref() {
+            Some(collapsed_block_margins) => *(collapsed_block_margins).clone(),
+            _ => CollapsedBlockMargins::zero(),
+        }
+    }
 }

components/layout_2020/positioned.rs

@@ -21,8 +21,7 @@ use crate::formatting_contexts::{
     IndependentFormattingContext, IndependentFormattingContextContents,
 };
 use crate::fragment_tree::{
-    BoxFragment, CollapsedBlockMargins, Fragment, FragmentFlags, HoistedSharedFragment,
+    BoxFragment, Fragment, FragmentFlags, HoistedSharedFragment, SpecificLayoutInfo,
-    SpecificLayoutInfo,
 };
 use crate::geom::{
     AuOrAuto, LengthPercentageOrAuto, LogicalRect, LogicalSides, LogicalSides1D, LogicalVec2,
@@ -697,9 +696,6 @@ impl HoistedAbsolutelyPositionedBox {
                 pbm.border.to_physical(containing_block_writing_mode),
                 margin.to_physical(containing_block_writing_mode),
                 None, /* clearance */
-                // We do not set the baseline offset, because absolutely positioned
-                // elements are not inflow.
-                CollapsedBlockMargins::zero(),
             )
             .with_specific_layout_info(specific_layout_info)
         };

components/layout_2020/table/layout.rs

@@ -1785,7 +1785,6 @@ impl<'a> TableLayout<'a> {
                 self.pbm.border.to_physical(table_writing_mode),
                 PhysicalSides::zero(),
                 None, /* clearance */
-                CollapsedBlockMargins::zero(),
             )
             .with_specific_layout_info(self.specific_layout_info_for_grid());
         }
@@ -1911,7 +1910,6 @@ impl<'a> TableLayout<'a> {
             self.pbm.border.to_physical(table_writing_mode),
             PhysicalSides::zero(),
             None, /* clearance */
-            CollapsedBlockMargins::zero(),
         )
         .with_baselines(baselines)
         .with_specific_layout_info(self.specific_layout_info_for_grid())
@@ -2338,7 +2336,6 @@ impl<'a> RowFragmentLayout<'a> {
             PhysicalSides::zero(), /* border */
             PhysicalSides::zero(), /* margin */
             None,                  /* clearance */
-            CollapsedBlockMargins::zero(),
         );
         row_fragment.set_does_not_paint_background();
 
@@ -2404,7 +2401,6 @@ impl RowGroupFragmentLayout {
             PhysicalSides::zero(), /* border */
             PhysicalSides::zero(), /* margin */
             None,                  /* clearance */
-            CollapsedBlockMargins::zero(),
         );
         row_group_fragment.set_does_not_paint_background();
 
@@ -2887,7 +2883,6 @@ impl TableSlotCell {
             layout.border.to_physical(table_style.writing_mode),
             PhysicalSides::zero(), /* margin */
             None,                  /* clearance */
-            CollapsedBlockMargins::zero(),
         )
         .with_baselines(layout.layout.baselines)
         .with_specific_layout_info(specific_layout_info)

components/layout_2020/taffy/layout.rs

@@ -23,8 +23,8 @@ use crate::fragment_tree::{
     BoxFragment, CollapsedBlockMargins, Fragment, FragmentFlags, SpecificLayoutInfo,
 };
 use crate::geom::{
-    LogicalSides, LogicalVec2, PhysicalPoint, PhysicalRect, PhysicalSides, PhysicalSize, Size,
+    LogicalVec2, PhysicalPoint, PhysicalRect, PhysicalSides, PhysicalSize, Size, SizeConstraint,
-    SizeConstraint, Sizes,
+    Sizes,
 };
 use crate::layout_box_base::CacheableLayoutResult;
 use crate::positioned::{AbsolutelyPositionedBox, PositioningContext, PositioningContextLength};
@@ -486,15 +486,6 @@ impl TaffyContainer {
             .map(|child| (**child).borrow_mut())
             .enumerate()
             .map(|(child_id, mut child)| {
-                fn rect_to_logical_sides<T>(rect: taffy::Rect<T>) -> LogicalSides<T> {
-                    LogicalSides {
-                        inline_start: rect.left,
-                        inline_end: rect.right,
-                        block_start: rect.top,
-                        block_end: rect.bottom,
-                    }
-                }
-
                 fn rect_to_physical_sides<T>(rect: taffy::Rect<T>) -> PhysicalSides<T> {
                     PhysicalSides::new(rect.top, rect.right, rect.bottom, rect.left)
                 }
@@ -514,8 +505,6 @@ impl TaffyContainer {
                 let padding = rect_to_physical_sides(layout.padding.map(Au::from_f32_px));
                 let border = rect_to_physical_sides(layout.border.map(Au::from_f32_px));
                 let margin = rect_to_physical_sides(layout.margin.map(Au::from_f32_px));
-                let logical_margin = rect_to_logical_sides(layout.margin.map(Au::from_f32_px));
-                let collapsed_margin = CollapsedBlockMargins::from_margin(&logical_margin);
 
                 // Compute content box size and position.
                 //
@@ -576,7 +565,6 @@ impl TaffyContainer {
                             border,
                             margin,
                             None, /* clearance */
-                            collapsed_margin,
                         )
                         .with_baselines(Baselines {
                             first: output.first_baselines.y.map(Au::from_f32_px),