LibWeb: Store table cell indices and spans in PaintableBox

The adjacency information is required to position borders correctly
between columns and rows.

Userland/Libraries/LibWeb/Layout/LayoutState.cpp

@@ -125,6 +125,9 @@ void LayoutState::commit()
             if (used_values.override_borders_data().has_value()) {
                 paintable_box.set_override_borders_data(used_values.override_borders_data().value());
             }
+            if (used_values.table_cell_coordinates().has_value()) {
+                paintable_box.set_table_cell_coordinates(used_values.table_cell_coordinates().value());
+            }
 
             if (is<Layout::BlockContainer>(box)) {
                 for (auto& line_box : used_values.line_boxes) {

Userland/Libraries/LibWeb/Layout/LayoutState.h

@@ -122,6 +122,9 @@ struct LayoutState {
         void set_override_borders_data(Painting::BordersData const& override_borders_data) { m_override_borders_data = override_borders_data; };
         auto const& override_borders_data() const { return m_override_borders_data; }
 
+        void set_table_cell_coordinates(Painting::PaintableBox::TableCellCoordinates const& table_cell_coordinates) { m_table_cell_coordinates = table_cell_coordinates; }
+        auto const& table_cell_coordinates() const { return m_table_cell_coordinates; }
+
     private:
         AvailableSize available_width_inside() const;
         AvailableSize available_height_inside() const;
@@ -137,6 +140,7 @@ struct LayoutState {
         HashTable<JS::GCPtr<Box const>> m_floating_descendants;
 
         Optional<Painting::BordersData> m_override_borders_data;
+        Optional<Painting::PaintableBox::TableCellCoordinates> m_table_cell_coordinates;
     };
 
     void commit();

Userland/Libraries/LibWeb/Layout/TableFormattingContext.cpp

@@ -931,13 +931,19 @@ void TableFormattingContext::border_conflict_resolution()
     // https://www.w3.org/TR/CSS22/tables.html#border-conflict-resolution
     BorderConflictFinder finder(this);
     for (auto& cell : m_cells) {
+        auto& cell_state = m_state.get_mutable(cell.box);
+        cell_state.set_table_cell_coordinates(
+            Painting::PaintableBox::TableCellCoordinates {
+                .row_index = cell.row_index,
+                .column_index = cell.column_index,
+                .row_span = cell.row_span,
+                .column_span = cell.column_span });
         if (cell.box->computed_values().border_collapse() == CSS::BorderCollapse::Separate) {
             continue;
         }
         // Execute steps 1, 2 and 3 of the algorithm for each edge.
         Painting::BordersData override_borders_data;
         auto const& cell_style = cell.box->computed_values();
-        auto& cell_state = m_state.get_mutable(cell.box);
         auto winning_border_left = cell_style.border_left();
         for (auto const conflicting_edge : finder.conflicting_edges(cell, ConflictingSide::Left)) {
             winning_border_left = winning_border_style(winning_border_left, border_data_conflicting_edge(conflicting_edge));

Userland/Libraries/LibWeb/Painting/PaintableBox.h

@@ -126,6 +126,16 @@ public:
     void set_override_borders_data(BordersData const& override_borders_data) { m_override_borders_data = override_borders_data; };
     auto const& override_borders_data() const { return m_override_borders_data; }
 
+    struct TableCellCoordinates {
+        size_t row_index;
+        size_t column_index;
+        size_t row_span;
+        size_t column_span;
+    };
+
+    void set_table_cell_coordinates(TableCellCoordinates const& table_cell_coordinates) { m_table_cell_coordinates = table_cell_coordinates; }
+    auto const& table_cell_coordinates() const { return m_table_cell_coordinates; }
+
     enum class ShrinkRadiiForBorders {
         Yes,
         No
@@ -166,6 +176,7 @@ private:
     Optional<BorderRadiusCornerClipper> mutable m_overflow_corner_radius_clipper;
 
     Optional<BordersData> m_override_borders_data;
+    Optional<TableCellCoordinates> m_table_cell_coordinates;
 };
 
 class PaintableWithLines final : public PaintableBox {