Optimize collapsed border calculation (step 2)

third_party/WebKit/Source/core/layout/LayoutTableSection.cpp

Index: third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp b/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
index 1f42815aa7b3bca21ac7bc365202cb84c7242579..b2e771c1f5d37eb6a41a72749ff1f63b12d5d905 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
@@ -131,8 +131,9 @@ void LayoutTableSection::StyleDidChange(StyleDifference diff,
   if (!table)
     return;
 
-  LayoutTableBoxComponent::InvalidateCollapsedBordersOnStyleChange(
-      *this, *table, diff, *old_style);
+  if (LayoutTableBoxComponent::NeedsInvalidateCollapsedBordersOnStyleChange(
+          *this, *table, diff, *old_style))
+    InvalidateCollapsedBordersOfAffectedCells();
 
   if (LayoutTableBoxComponent::DoCellsHaveDirtyWidth(*this, *table, diff,
                                                      *old_style))
@@ -2172,4 +2173,77 @@ bool LayoutTableSection::PaintedOutputOfObjectHasNoEffectRegardlessOfSize()
       PaintedOutputOfObjectHasNoEffectRegardlessOfSize();
 }
 
+void LayoutTableSection::InvalidateCellCollapsedBordersIntersectingRow(
+    unsigned row_index) {
+  auto& row_struct = grid_[row_index].row;
+  for (auto& cell_struct : row_struct) {
+    if (cell_struct.in_col_span)
+      continue;
+    if (auto* cell = cell_struct.PrimaryCell())
+      cell->InvalidateCollapsedBorderValues();
+  }
+}
+
+void LayoutTableSection::InvalidateCollapsedBordersOfAffectedCells() {
+  auto* table = this->Table();
+  DCHECK(table->CollapseBorders());
+  if (table->NeedsInvalidateCollapsedBordersForAllCells())
+    return;
+
+  table->RecalcSectionsIfNeeded();
+  table->InvalidateCollapsedBorders();
+
+  if (NumRows()) {
+    // Invalidate cells intersecting the top row.
+    InvalidateCellCollapsedBordersIntersectingRow(0);
+    // Invalidate cells intersecting the bottom row.
+    if (NumRows() > 1)
+      InvalidateCellCollapsedBordersIntersectingRow(NumRows() - 1);
+
+    // Invalidate cell in start and end columns.
+    auto num_effective_columns = this->NumEffectiveColumns();
+    for (unsigned r = 0; r < NumRows(); ++r) {
+      if (auto* cell = PrimaryCellAt(r, 0))
+        cell->InvalidateCollapsedBorderValues();
+      if (auto* cell = PrimaryCellAt(r, num_effective_columns - 1))
+        cell->InvalidateCollapsedBorderValues();
+    }
+  }
+
+  // Invalidate cells in the row above the top row.
+  if (auto* section = table->SectionAbove(this, kSkipEmptySections)) {
+    section->InvalidateCellCollapsedBordersIntersectingRow(section->NumRows() -
+                                                           1);
+  }
+  // Invalidate cells in the row below the bottom row.
+  if (auto* section = table->SectionBelow(this, kSkipEmptySections)) {
+    section->InvalidateCellCollapsedBordersIntersectingRow(0);
+  }
+}
+
+LayoutTableCell* LayoutTableSection::PrimaryCellAboveInTable(
+    unsigned row,
+    unsigned effective_column) {
+  DCHECK(PrimaryCellAt(row, effective_column)->RowIndex() == row);
+  if (row)
+    return PrimaryCellAt(row - 1, effective_column);
+  if (auto* section_above = Table()->SectionAbove(this, kSkipEmptySections)) {
+    return section_above->PrimaryCellAt(section_above->NumRows() - 1,
+                                        effective_column);
+  }
+  return nullptr;
+}
+
+LayoutTableCell* LayoutTableSection::PrimaryCellBelowInTable(
+    unsigned row,
+    unsigned effective_column) {
+  DCHECK(PrimaryCellAt(row, effective_column)->RowIndex() == row);
+  unsigned row_below = row + PrimaryCellAt(row, effective_column)->RowSpan();
+  if (row_below < NumRows())
+    return PrimaryCellAt(row_below, effective_column);
+  if (auto* section_below = Table()->SectionBelow(this, kSkipEmptySections))
+    return section_below->PrimaryCellAt(0, effective_column);
+  return nullptr;
+}
+
 }  // namespace blink