layout: Stop ignoring containing block padding for the static position (#36051)

The static position rect is calculated assuming that the containing
block would be established by the content box of some ancestor, but the
actual containing block is established by the padding box.
So we need to add the padding of that ancestor.

Signed-off-by: Oriol Brufau <obrufau@igalia.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/components/layout_2020/positioned.rs b/components/layout_2020/positioned.rs
index e13ad412652..8b10a79b59c 100644
--- a/components/layout_2020/positioned.rs
+++ b/components/layout_2020/positioned.rs
@@ -26,7 +26,8 @@ use crate::fragment_tree::{
 };
 use crate::geom::{
     AuOrAuto, LengthPercentageOrAuto, LogicalRect, LogicalSides, LogicalSides1D, LogicalVec2,
-    PhysicalPoint, PhysicalRect, PhysicalVec, Size, Sizes, ToLogical, ToLogicalWithContainingBlock,
+    PhysicalPoint, PhysicalRect, PhysicalSides, PhysicalSize, PhysicalVec, Size, Sizes, ToLogical,
+    ToLogicalWithContainingBlock,
 };
 use crate::sizing::ContentSizes;
 use crate::style_ext::{Clamp, ComputedValuesExt, ContentBoxSizesAndPBM, DisplayInside};
@@ -272,6 +273,7 @@ impl PositioningContext {
                 &mut laid_out_child_fragments,
                 &mut self.for_nearest_containing_block_for_all_descendants,
                 &containing_block,
+                new_fragment.padding,
             );
             hoisted_boxes = take_hoisted_boxes_pending_layout(self);
         }
@@ -354,6 +356,7 @@ impl PositioningContext {
                 fragments,
                 &mut self.for_nearest_containing_block_for_all_descendants,
                 initial_containing_block,
+                Default::default(),
             )
         }
     }
@@ -415,6 +418,7 @@ impl HoistedAbsolutelyPositionedBox {
         fragments: &mut Vec<Fragment>,
         for_nearest_containing_block_for_all_descendants: &mut Vec<HoistedAbsolutelyPositionedBox>,
         containing_block: &DefiniteContainingBlock,
+        containing_block_padding: PhysicalSides<Au>,
     ) {
         if layout_context.use_rayon {
             let mut new_fragments = Vec::new();
@@ -428,6 +432,7 @@ impl HoistedAbsolutelyPositionedBox {
                         layout_context,
                         &mut new_hoisted_boxes,
                         containing_block,
+                        containing_block_padding,
                     );
 
                     hoisted_box.fragment.borrow_mut().fragment =
@@ -445,6 +450,7 @@ impl HoistedAbsolutelyPositionedBox {
                     layout_context,
                     for_nearest_containing_block_for_all_descendants,
                     containing_block,
+                    containing_block_padding,
                 );
 
                 box_.fragment.borrow_mut().fragment = Some(Fragment::Box(new_fragment.clone()));
@@ -458,6 +464,7 @@ impl HoistedAbsolutelyPositionedBox {
         layout_context: &LayoutContext,
         for_nearest_containing_block_for_all_descendants: &mut Vec<HoistedAbsolutelyPositionedBox>,
         containing_block: &DefiniteContainingBlock,
+        containing_block_padding: PhysicalSides<Au>,
     ) -> ArcRefCell<BoxFragment> {
         let cbis = containing_block.size.inline;
         let cbbs = containing_block.size.block;
@@ -473,11 +480,16 @@ impl HoistedAbsolutelyPositionedBox {
         } = layout_style.content_box_sizes_and_padding_border_margin(&containing_block.into());
         let containing_block = &containing_block.into();
         let is_table = layout_style.is_table();
-
         let shared_fragment = self.fragment.borrow();
-        let static_position_rect = shared_fragment
+
+        // The static position rect was calculated assuming that the containing block would be
+        // established by the content box of some ancestor, but the actual containing block is
+        // established by the padding box. So we need to add the padding of that ancestor.
+        let mut static_position_rect = shared_fragment
             .static_position_rect
-            .to_logical(containing_block);
+            .outer_rect(-containing_block_padding);
+        static_position_rect.size = static_position_rect.size.max(PhysicalSize::zero());
+        let static_position_rect = static_position_rect.to_logical(containing_block);
 
         let box_offset = style.box_offsets(containing_block.style.writing_mode);