Paint collapsed borders of a table as one display item

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

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/TablePainter.h"
 
 #include "core/layout/LayoutTable.h"
 #include "core/layout/LayoutTableSection.h"
 #include "core/style/CollapsedBorderValue.h"
 #include "core/paint/BoxClipper.h"
@@ skipping 26 matching lines @@
     for (LayoutObject* child = m_layoutTable.firstChild(); child;
          child = child->nextSibling()) {
       if (child->isBox() && !toLayoutBox(child)->hasSelfPaintingLayer() &&
           (child->isTableSection() || child->isTableCaption())) {
         LayoutPoint childPoint = m_layoutTable.flipForWritingModeForChild(
             toLayoutBox(child), paintOffset);
         child->paint(paintInfoForDescendants, childPoint);
       }
     }
 
-    if (m_layoutTable.collapseBorders() &&
-        shouldPaintDescendantBlockBackgrounds(paintPhase) &&
-        m_layoutTable.style()->visibility() == EVisibility::Visible) {
-      // Using our cached sorted styles, we then do individual passes,
-      // painting each style of border from lowest precedence to highest
-      // precedence.
-      LayoutTable::CollapsedBorderValues collapsedBorders =
-          m_layoutTable.collapsedBorders();
-      size_t count = collapsedBorders.size();
-      for (size_t i = 0; i < count; ++i) {
-        for (LayoutTableSection* section = m_layoutTable.bottomSection();
-             section; section = m_layoutTable.sectionAbove(section)) {
-          LayoutPoint childPoint =
-              m_layoutTable.flipForWritingModeForChild(section, paintOffset);
-          TableSectionPainter(*section).paintCollapsedBorders(
-              paintInfoForDescendants, childPoint, collapsedBorders[i]);
-        }
-      }
-    }
+    if (shouldPaintDescendantBlockBackgrounds(paintPhase))
+      paintCollapsedBorders(paintInfoForDescendants, paintOffset);
   }
 
   if (shouldPaintSelfOutline(paintPhase))
     ObjectPainter(m_layoutTable).paintOutline(paintInfo, paintOffset);
 }
 
+void TablePainter::paintCollapsedBorders(const PaintInfo& paintInfo,
+                                         const LayoutPoint& paintOffset) {
+  if (!m_layoutTable.hasCollapsedBorders() ||
+      m_layoutTable.style()->visibility() != EVisibility::Visible)
+    return;
+
+  LayoutTable::CollapsedBordersInfo& collapsedBorders =
+      m_layoutTable.getCollapsedBordersInfo();
+
+  // Normally we don't clip individual display items by paint dirty rect

[chrishtr, 2016/11/03 21:16:29]

Is such an optimization already implemented in the old code?

[Xianzhu, 2016/11/03 21:26:55]

Yes, in TableSectionPainter, to skip painting collapsed borders for cells out of
the interest rect. Actually the new code here is to adapt to the old
optimization, because the display item may change when interest rect changes.

+  // (aka interest rect), to keep display items independent with paint dirty
+  // rect so we can just depend on paint invalidation status to repaint them.
+  // However, the collapsed border display item may be too big to contain all
+  // collapsed borders in a huge table, so we clip it to paint dirty rect.
+  // We need to invalidate the display item if the previous paint is clipped
+  // and the paint dirty rect changed.
+  if (collapsedBorders.lastPaintResult != FullyPainted &&
+      collapsedBorders.lastPaintRect != paintInfo.cullRect())
+    m_layoutTable.setDisplayItemsUncached();
+
+  if (!DrawingRecorder::useCachedDrawingIfPossible(

[chrishtr, 2016/11/03 21:16:29]

if (DrawingRecorder::useCachedDrawingIfPossible(...))
  return;

[Xianzhu, 2016/11/03 21:26:55]

Done.

+          paintInfo.context, m_layoutTable,
+          DisplayItem::kTableCollapsedBorders)) {
+    DrawingRecorder recorder(
+        paintInfo.context, m_layoutTable, DisplayItem::kTableCollapsedBorders,
+        FloatRect(LayoutRect(paintOffset, m_layoutTable.size())));
+
+    // Using our cached sorted styles, we then do individual passes, painting
+    // each style of border from lowest precedence to highest precedence.
+    PaintResult paintResult = FullyPainted;
+    for (const auto& borderValue : collapsedBorders.values) {
+      for (LayoutTableSection* section = m_layoutTable.bottomSection(); section;
+           section = m_layoutTable.sectionAbove(section)) {
+        LayoutPoint childPoint =
+            m_layoutTable.flipForWritingModeForChild(section, paintOffset);
+        if (TableSectionPainter(*section).paintCollapsedBorders(
+                paintInfo, childPoint, borderValue) ==
+            MayBeClippedByPaintDirtyRect)
+          paintResult = MayBeClippedByPaintDirtyRect;
+      }
+    }
+    collapsedBorders.lastPaintResult = paintResult;
+    collapsedBorders.lastPaintRect = paintInfo.cullRect();
+  }
+}
+
 void TablePainter::paintBoxDecorationBackground(
     const PaintInfo& paintInfo,
     const LayoutPoint& paintOffset) {
   if (!m_layoutTable.hasBoxDecorationBackground() ||
       m_layoutTable.style()->visibility() != EVisibility::Visible)
     return;
 
   LayoutRect rect(paintOffset, m_layoutTable.size());
   m_layoutTable.subtractCaptionRect(rect);
   BoxPainter(m_layoutTable)
@@ skipping 12 matching lines @@
 
   LayoutRect rect(paintOffset, m_layoutTable.size());
   m_layoutTable.subtractCaptionRect(rect);
 
   LayoutObjectDrawingRecorder recorder(paintInfo.context, m_layoutTable,
                                        paintInfo.phase, rect);
   BoxPainter(m_layoutTable).paintMaskImages(paintInfo, rect);
 }
 
 }  // namespace blink