Fix Border collapsing with colpsan / rowspan cells

third_party/WebKit/Source/core/paint/TableSectionPainter.cpp

Index: third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
diff --git a/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp b/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
index f66cc741d5c26522ae8ff130d27ed3a1c890c050..43866261da363c5231d0decbb9091690951f2de9 100644
--- a/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
+++ b/third_party/WebKit/Source/core/paint/TableSectionPainter.cpp
@@ -4,6 +4,7 @@
 
 #include "core/paint/TableSectionPainter.h"
 
+#include <algorithm>
 #include "core/layout/LayoutTableCell.h"
 #include "core/layout/LayoutTableCol.h"
 #include "core/layout/LayoutTableRow.h"
@@ -13,15 +14,15 @@
 #include "core/paint/ObjectPainter.h"
 #include "core/paint/PaintInfo.h"
 #include "core/paint/TableCellPainter.h"
+#include "core/paint/TableCollapsedBorderPainter.h"
 #include "core/paint/TableRowPainter.h"
-#include <algorithm>
 
 namespace blink {
 
 void TableSectionPainter::PaintRepeatingHeaderGroup(
     const PaintInfo& paint_info,
     const LayoutPoint& paint_offset,
-    const CollapsedBorderValue& current_border_value,
+    TableCollapsedBorderPainter& previous_painter,
     ItemToPaint item_to_paint) {
   if (!layout_table_section_.IsRepeatingHeaderGroup())
     return;
@@ -61,7 +62,7 @@ void TableSectionPainter::PaintRepeatingHeaderGroup(
   while (pagination_offset.Y() < bottom_bound) {
     if (item_to_paint == kPaintCollapsedBorders) {
       PaintCollapsedSectionBorders(paint_info, pagination_offset,
-                                   current_border_value);
+                                   previous_painter);
     } else {
       PaintSection(paint_info, pagination_offset);
     }
@@ -75,9 +76,11 @@ void TableSectionPainter::Paint(const PaintInfo& paint_info,
       .CheckPaintOffset(paint_info, paint_offset);
   PaintSection(paint_info, paint_offset);
   LayoutTable* table = layout_table_section_.Table();
-  if (table->Header() == layout_table_section_)
-    PaintRepeatingHeaderGroup(paint_info, paint_offset, CollapsedBorderValue(),
+  if (table->Header() == layout_table_section_) {
+    TableCollapsedBorderPainter old_painter;
+    PaintRepeatingHeaderGroup(paint_info, paint_offset, old_painter,
                               kPaintSection);
+  }
 }
 
 void TableSectionPainter::PaintSection(const PaintInfo& paint_info,
@@ -129,59 +132,39 @@ static inline bool CompareCellPositionsWithOverflowingCells(
 void TableSectionPainter::PaintCollapsedBorders(
     const PaintInfo& paint_info,
     const LayoutPoint& paint_offset,
-    const CollapsedBorderValue& current_border_value) {
-  PaintCollapsedSectionBorders(paint_info, paint_offset, current_border_value);
+    TableCollapsedBorderPainter& previous_painter) {
+  PaintCollapsedSectionBorders(paint_info, paint_offset, previous_painter);
   LayoutTable* table = layout_table_section_.Table();
   if (table->Header() == layout_table_section_)
-    PaintRepeatingHeaderGroup(paint_info, paint_offset, current_border_value,
+    PaintRepeatingHeaderGroup(paint_info, paint_offset, previous_painter,
                               kPaintCollapsedBorders);
 }
 
 void TableSectionPainter::PaintCollapsedSectionBorders(
     const PaintInfo& paint_info,
     const LayoutPoint& paint_offset,
-    const CollapsedBorderValue& current_border_value) {
+    TableCollapsedBorderPainter& previous_painter) {
   if (!layout_table_section_.NumRows() ||
       !layout_table_section_.Table()->EffectiveColumns().size())
     return;
-
   LayoutPoint adjusted_paint_offset =
       paint_offset + layout_table_section_.Location();
-  BoxClipper box_clipper(layout_table_section_, paint_info,
-                         adjusted_paint_offset, kForceContentsClip);
-
-  LayoutRect local_visual_rect = LayoutRect(paint_info.GetCullRect().rect_);
-  local_visual_rect.MoveBy(-adjusted_paint_offset);
-
+  BoxClipper boxClipper(layout_table_section_, paint_info,
+                        adjusted_paint_offset, kForceContentsClip);
+  LayoutRect local_paint_invalidation_rect =
+      LayoutRect(paint_info.GetCullRect().rect_);
+  local_paint_invalidation_rect.MoveBy(-adjusted_paint_offset);
   LayoutRect table_aligned_rect =
       layout_table_section_.LogicalRectForWritingModeAndDirection(
-          local_visual_rect);
-
+          local_paint_invalidation_rect);
   CellSpan dirtied_rows = layout_table_section_.DirtiedRows(table_aligned_rect);
-  CellSpan dirtied_columns =
+  CellSpan dirtied_eff_columns =
       layout_table_section_.DirtiedEffectiveColumns(table_aligned_rect);
 
-  if (dirtied_columns.Start() >= dirtied_columns.end())
-    return;
-
-  // Collapsed borders are painted from the bottom right to the top left so that
-  // precedence due to cell position is respected.
-  for (unsigned r = dirtied_rows.end(); r > dirtied_rows.Start(); r--) {
-    unsigned row = r - 1;
-    unsigned n_cols = layout_table_section_.NumCols(row);
-    for (unsigned c = std::min(dirtied_columns.end(), n_cols);
-         c > dirtied_columns.Start(); c--) {
-      unsigned col = c - 1;
-      if (const LayoutTableCell* cell =
-              layout_table_section_.OriginatingCellAt(row, col)) {
-        LayoutPoint cell_point =
-            layout_table_section_.FlipForWritingModeForChild(
-                cell, adjusted_paint_offset);
-        TableCellPainter(*cell).PaintCollapsedBorders(paint_info, cell_point,
-                                                      current_border_value);
-      }
-    }
-  }
+  TableCollapsedBorderPainter painter(&layout_table_section_);
+  painter.PaintBorders(paint_info, paint_offset, dirtied_rows,
+                       dirtied_eff_columns, previous_painter);
+  previous_painter = painter;
 }
 
 void TableSectionPainter::PaintObject(const PaintInfo& paint_info,