Paint backgrounds of a table section/row in one display item

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

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2013
 *                Apple Inc.
  *               All rights reserved.
  *
@@ skipping 287 matching lines @@
   if (cell->rowSpan() == 1)
     return;
 
   // Cells only generates visual overflow.
   LayoutRect cellVisualOverflowRect =
       cell->visualOverflowRectForPropagation(styleRef());
 
   // The cell and the row share the section's coordinate system. However
   // the visual overflow should be determined in the coordinate system of
   // the row, that's why we shift it below.
-  LayoutUnit cellOffsetLogicalTopDifference =
-      cell->location().y() - location().y();
-  cellVisualOverflowRect.move(LayoutUnit(), cellOffsetLogicalTopDifference);
+  cellVisualOverflowRect.moveBy(-location());

[chrishtr, 2017/03/31 22:59:06]

Why this change?

[Xianzhu, 2017/03/31 23:26:30]

The original code happens to be correct for horizontal layout (when
location().x() is zero), but is incorrect for vertical layout. The changed code
is consistent with other places where we adjust cell location in row.

Found the issue when adding line 311-317 which needs the similar logic.

+  addContentsVisualOverflow(cellVisualOverflowRect);
 
-  addContentsVisualOverflow(cellVisualOverflowRect);
+  // Table row paints its background behind cells. If the cell spans multiple
+  // rows, the row's visual rect should be expanded to cover the cell.
+  if (styleRef().hasBackground()) {
+    LayoutRect cellBackgroundRect = cell->frameRect();
+    cellBackgroundRect.moveBy(-location());
+    addSelfVisualOverflow(cellBackgroundRect);
+  }
 }
 
 bool LayoutTableRow::isFirstRowInSectionAfterHeader() const {
   // If there isn't room on the page for at least one content row after the
   // header group, then we won't repeat the header on each page.
   // https://drafts.csswg.org/css-tables-3/#repeated-headers reads like
   // it wants us to drop headers on only the pages that a single row
   // won't fit but we avoid the complexity of that reading until it
   // is clarified. Tracked by crbug.com/675904
   if (rowIndex())
     return false;
   LayoutTableSection* header = table()->header();
   return header && table()->sectionAbove(section()) == header &&
          header->getPaginationBreakability() != AllowAnyBreaks;
 }
 
 }  // namespace blink