Optimize collapsed border painting

third_party/WebKit/Source/core/layout/LayoutTableCell.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 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 25 matching lines @@
 #include "platform/geometry/FloatQuad.h"
 #include "platform/geometry/TransformState.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 struct SameSizeAsLayoutTableCell : public LayoutBlockFlow {
     unsigned bitfields;
     int paddings[2];
+    void* pointer;
 };
 
 static_assert(sizeof(LayoutTableCell) == sizeof(SameSizeAsLayoutTableCell), "LayoutTableCell should stay small");
 static_assert(sizeof(CollapsedBorderValue) == 8, "CollapsedBorderValue should stay small");
 
 LayoutTableCell::LayoutTableCell(Element* element)
     : LayoutBlockFlow(element)
     , m_absoluteColumnIndex(unsetColumnIndex)
     , m_cellWidthChanged(false)
     , m_intrinsicPaddingBefore(0)
     , m_intrinsicPaddingAfter(0)
 {
     // We only update the flags when notified of DOM changes in colSpanOrRowSpanChanged()
     // so we need to set their initial values here in case something asks for colSpan()/rowSpan() before then.
     updateColAndRowSpanFlags();
 }
 
 void LayoutTableCell::willBeRemovedFromTree()
 {
     LayoutBlockFlow::willBeRemovedFromTree();
 
     section()->setNeedsCellRecalc();
-    section()->removeCachedCollapsedBorders(this);
 }
 
 unsigned LayoutTableCell::parseColSpanFromDOM() const
 {
     ASSERT(node());
     if (isHTMLTableCellElement(*node()))
         return std::min<unsigned>(toHTMLTableCellElement(*node()).colSpan(), maxColumnIndex);
     return 1;
 }
 
@@ skipping 822 matching lines @@
     size_t count = borderValues.size();
     for (size_t i = 0; i < count; ++i) {
         if (borderValues[i].isSameIgnoringColor(borderValue))
             return;
     }
     borderValues.append(borderValue);
 }
 
 void LayoutTableCell::collectBorderValues(LayoutTable::CollapsedBorderValues& borderValues)
 {
-    CollapsedBorderValue startBorder = computeCollapsedStartBorder();
-    CollapsedBorderValue endBorder = computeCollapsedEndBorder();
-    CollapsedBorderValue beforeBorder = computeCollapsedBeforeBorder();
-    CollapsedBorderValue afterBorder = computeCollapsedAfterBorder();
-    LayoutTableSection* section = this->section();
-    bool changed = section->setCachedCollapsedBorder(this, CBSStart, startBorder);
-    changed |= section->setCachedCollapsedBorder(this, CBSEnd, endBorder);
-    changed |= section->setCachedCollapsedBorder(this, CBSBefore, beforeBorder);
-    changed |= section->setCachedCollapsedBorder(this, CBSAfter, afterBorder);
+    CollapsedBorderValues newValues = {
+        computeCollapsedStartBorder(),
+        computeCollapsedEndBorder(),
+        computeCollapsedBeforeBorder(),
+        computeCollapsedAfterBorder()
+    };
 
-    // In slimming paint mode, we need to invalidate all cells with collapsed border changed.

[chrishtr, 2016/05/05 15:31:36]

Still gone?

[Xianzhu, 2016/05/05 17:38:49]

It's now at new line 934-935.

-    // FIXME: Need a way to invalidate/repaint the borders only. crbug.com/451090#c5.
+    bool changed = false;
+    if (!newValues.startBorder.isVisible() && !newValues.endBorder.isVisible() && !newValues.beforeBorder.isVisible() && !newValues.afterBorder.isVisible()) {
+        changed = !!m_collapsedBorderValues;
+        m_collapsedBorderValues = nullptr;
+    } else if (!m_collapsedBorderValues) {
+        changed = true;
+        m_collapsedBorderValues = adoptPtr(new CollapsedBorderValues(newValues));
+    } else {
+        changed = !m_collapsedBorderValues->startBorder.visuallyEquals(newValues.startBorder)

[chrishtr, 2016/05/05 15:31:36]

Add a comment that we check visuallyEquals so that the table cell is invalidated
only if a changed collapsed border
is visible in the first place.

[Xianzhu, 2016/05/05 17:38:49]

Done.

[chrishtr, 2016/05/05 17:42:12]

Don't see the added comment in this patch set?

[Xianzhu, 2016/05/05 17:45:15]

Sorry, didn't press <Enter> after git cl upload.

+            || !m_collapsedBorderValues->endBorder.visuallyEquals(newValues.endBorder)
+            || !m_collapsedBorderValues->beforeBorder.visuallyEquals(newValues.beforeBorder)
+            || !m_collapsedBorderValues->afterBorder.visuallyEquals(newValues.afterBorder);
+        if (changed)
+            *m_collapsedBorderValues = newValues;
+    }
+
+    // If collapsed borders changed, invalidate the cell's display item client on the table's backing.
+    // TODO(crbug.com/451090#c5): Need a way to invalidate/repaint the borders only.
     if (changed)
         table()->invalidateDisplayItemClient(*this);
 
-    addBorderStyle(borderValues, startBorder);
-    addBorderStyle(borderValues, endBorder);
-    addBorderStyle(borderValues, beforeBorder);
-    addBorderStyle(borderValues, afterBorder);
+    addBorderStyle(borderValues, newValues.startBorder);
+    addBorderStyle(borderValues, newValues.endBorder);
+    addBorderStyle(borderValues, newValues.beforeBorder);
+    addBorderStyle(borderValues, newValues.afterBorder);
 }
 
 void LayoutTableCell::sortBorderValues(LayoutTable::CollapsedBorderValues& borderValues)
 {
     std::sort(borderValues.begin(), borderValues.end(), compareBorders);
 }
 
 void LayoutTableCell::paintBoxDecorationBackground(const PaintInfo& paintInfo, const LayoutPoint& paintOffset) const
 {
     TableCellPainter(*this).paintBoxDecorationBackground(paintInfo, paintOffset);
@@ skipping 53 matching lines @@
 bool LayoutTableCell::backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const
 {
     // If this object has layer, the area of collapsed borders should be transparent
     // to expose the collapsed borders painted on the underlying layer.
     if (hasLayer() && table()->collapseBorders())
         return false;
     return LayoutBlockFlow::backgroundIsKnownToBeOpaqueInRect(localRect);
 }
 
 } // namespace blink