Let cull rect of collapsed border contain all painted area

Source/core/paint/TableCellPainter.cpp

Index: Source/core/paint/TableCellPainter.cpp
diff --git a/Source/core/paint/TableCellPainter.cpp b/Source/core/paint/TableCellPainter.cpp
index b642ddae56c94a065d7a6dbc6768a3ba21aa41af..98ddaa79237fe6b7ff46da230481b656e5a09dda 100644
--- a/Source/core/paint/TableCellPainter.cpp
+++ b/Source/core/paint/TableCellPainter.cpp
@@ -72,17 +72,6 @@ void TableCellPainter::paintCollapsedBorders(const PaintInfo& paintInfo, const L
     if (!paintInfo.shouldPaintWithinRoot(&m_layoutTableCell) || m_layoutTableCell.style()->visibility() != VISIBLE)
         return;
 
-    LayoutRect paintRect = paintBounds(paintOffset, AddOffsetFromParent);
-
-    LayoutRect drawingCullRect(paintRect);
-    drawingCullRect.expandEdges(m_layoutTableCell.table()->outerBorderTop(), m_layoutTableCell.table()->outerBorderRight(),
-        m_layoutTableCell.table()->outerBorderBottom(), m_layoutTableCell.table()->outerBorderLeft());
-    if (drawingCullRect.y() >= paintInfo.rect.maxY())

[chrishtr, 2015/06/04 22:21:06]

You're removing a non-SP culling optimization. Was it previously broken?

[Xianzhu, 2015/06/05 00:02:14]

The cullrect was incorrect (which doesn't cover all collapsed border if the used
collapsed border is wider than the table's border). We should use borderRect
instead.

New line 105 is the new culling optimization.

-        return;
-
-    if (drawingCullRect.maxY() <= paintInfo.rect.y())
-        return;
-
     const CollapsedBorderValue* tableCurrentBorderValue = m_layoutTableCell.table()->currentBorderValue();
     if (!tableCurrentBorderValue)
         return;
@@ -101,25 +90,28 @@ void TableCellPainter::paintCollapsedBorders(const PaintInfo& paintInfo, const L
     if (!shouldPaintTop && !shouldPaintBottom && !shouldPaintLeft && !shouldPaintRight)
         return;
 
-    GraphicsContext* graphicsContext = paintInfo.context;
-    LayoutObjectDrawingRecorder recorder(*graphicsContext, m_layoutTableCell, paintInfo.phase, drawingCullRect);
-    if (recorder.canUseCachedDrawing())
-        return;
-
-    bool antialias = BoxPainter::shouldAntialiasLines(graphicsContext);
-
     // Adjust our x/y/width/height so that we paint the collapsed borders at the correct location.
     int topWidth = topBorderValue.width();
     int bottomWidth = bottomBorderValue.width();
     int leftWidth = leftBorderValue.width();
     int rightWidth = rightBorderValue.width();
 
+    LayoutRect paintRect = paintBounds(paintOffset, AddOffsetFromParent);

[chrishtr, 2015/06/05 00:31:06]

This is not used?

Why not fix paintBounds?

[Xianzhu, 2015/06/05 00:40:58]

Here paintRect is used to calculate borderRect below. The result of
paintBounds() is for other paintings, not including collapsed borders.

[chrishtr, 2015/06/05 04:55:28]

Oh right, sorry. My comment was too hasty.

     IntRect borderRect = pixelSnappedIntRect(paintRect.x() - leftWidth / 2,
         paintRect.y() - topWidth / 2,
         paintRect.width() + leftWidth / 2 + (rightWidth + 1) / 2,
         paintRect.height() + topWidth / 2 + (bottomWidth + 1) / 2);
 
+    if (!borderRect.intersects(paintInfo.rect))
+        return;
+
+    GraphicsContext* graphicsContext = paintInfo.context;
+    LayoutObjectDrawingRecorder recorder(*graphicsContext, m_layoutTableCell, paintInfo.phase, borderRect);
+    if (recorder.canUseCachedDrawing())
+        return;
+
     Color cellColor = m_layoutTableCell.resolveColor(CSSPropertyColor);
+    bool antialias = BoxPainter::shouldAntialiasLines(graphicsContext);
 
     // We never paint diagonals at the joins.  We simply let the border with the highest
     // precedence paint on top of borders with lower precedence.