Save previous paint offset in LayoutObject

Source/core/paint/LayoutObjectDrawingRecorder.h

Index: Source/core/paint/LayoutObjectDrawingRecorder.h
diff --git a/Source/core/paint/LayoutObjectDrawingRecorder.h b/Source/core/paint/LayoutObjectDrawingRecorder.h
index b0da6bb6a3d838da9605d842919c131470ba19d6..2fe4597df4339e362c3aa5645d913c7a725b36f2 100644
--- a/Source/core/paint/LayoutObjectDrawingRecorder.h
+++ b/Source/core/paint/LayoutObjectDrawingRecorder.h
@@ -6,7 +6,6 @@
 #define LayoutObjectDrawingRecorder_h
 
 #include "core/layout/LayoutObject.h"
-#include "core/layout/line/InlineBox.h"
 #include "core/paint/PaintPhase.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/geometry/LayoutRect.h"
@@ -25,8 +24,7 @@ class LayoutObjectDrawingRecorder final {
 public:
     static bool useCachedDrawingIfPossible(GraphicsContext& context, const LayoutObject& layoutObject, DisplayItem::Type displayItemType, const LayoutPoint& paintOffset)
     {
-        // TODO(pdr): The paint offset cache should be stored on LayoutObject but is temporarily on the DisplayItemList.
-        if (RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled() && !context.displayItemList()->paintOffsetIsUnchanged(layoutObject.displayItemClient(), paintOffset))
+        if (RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled() && !layoutObject.paintOffsetChanged(paintOffset))
             return false;
         if (layoutObject.fullPaintInvalidationReason() == PaintInvalidationDelayedFull)
             return false;
@@ -38,19 +36,6 @@ public:
         return useCachedDrawingIfPossible(context, layoutObject, DisplayItem::paintPhaseToDrawingType(phase), paintOffset);
     }
 
-    static bool useCachedDrawingIfPossible(GraphicsContext& context, const InlineBox& inlineBox, DisplayItem::Type displayItemType, const LayoutPoint& paintOffset)
-    {
-        // TODO(pdr): The paint offset cache should be stored on LayoutObject but is temporarily on the DisplayItemList.
-        if (RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled() && !context.displayItemList()->paintOffsetIsUnchanged(inlineBox.displayItemClient(), paintOffset))
-            return false;
-        return DrawingRecorder::useCachedDrawingIfPossible(context, inlineBox, displayItemType);
-    }
-
-    static bool useCachedDrawingIfPossible(GraphicsContext& context, const InlineBox& inlineBox, PaintPhase phase, const LayoutPoint& paintOffset)
-    {
-        return useCachedDrawingIfPossible(context, inlineBox, DisplayItem::paintPhaseToDrawingType(phase), paintOffset);
-    }
-
     LayoutObjectDrawingRecorder(GraphicsContext& context, const LayoutObject& layoutObject, DisplayItem::Type displayItemType, const FloatRect& clip, const LayoutPoint& paintOffset)
     {
         updatePaintOffsetIfNeeded(context.displayItemList(), layoutObject, paintOffset);
@@ -72,38 +57,22 @@ public:
     LayoutObjectDrawingRecorder(GraphicsContext& context, const LayoutObject& layoutObject, PaintPhase phase, const IntRect& clip, const LayoutPoint& paintOffset)
         : LayoutObjectDrawingRecorder(context, layoutObject, DisplayItem::paintPhaseToDrawingType(phase), FloatRect(clip), paintOffset) { }
 
-    LayoutObjectDrawingRecorder(GraphicsContext& context, const InlineBox& inlineBox, DisplayItem::Type displayItemType, const FloatRect& clip, const LayoutPoint& paintOffset)
-    {
-        updatePaintOffsetIfNeeded(context.displayItemList(), inlineBox, paintOffset);
-        m_drawingRecorder.emplace(context, inlineBox, displayItemType, clip);
-    }
-
-    LayoutObjectDrawingRecorder(GraphicsContext& context, const InlineBox& inlineBox, DisplayItem::Type displayItemType, const LayoutRect& clip, const LayoutPoint& paintOffset)
-        : LayoutObjectDrawingRecorder(context, inlineBox, displayItemType, FloatRect(clip), paintOffset) { }
-
-    LayoutObjectDrawingRecorder(GraphicsContext& context, const InlineBox& inlineBox, PaintPhase phase, const LayoutRect& clip, const LayoutPoint& paintOffset)
-        : LayoutObjectDrawingRecorder(context, inlineBox, DisplayItem::paintPhaseToDrawingType(phase), FloatRect(clip), paintOffset) { }
-
-    LayoutObjectDrawingRecorder(GraphicsContext& context, const InlineBox& inlineBox, PaintPhase phase, const IntRect& clip, const LayoutPoint& paintOffset)
-        : LayoutObjectDrawingRecorder(context, inlineBox, DisplayItem::paintPhaseToDrawingType(phase), FloatRect(clip), paintOffset) { }
-
 #if ENABLE(ASSERT)
     void setUnderInvalidationCheckingMode(DrawingDisplayItem::UnderInvalidationCheckingMode mode) { m_drawingRecorder->setUnderInvalidationCheckingMode(mode); }
 #endif
 
 private:
-    static void updatePaintOffsetIfNeeded(DisplayItemList* displayItemList, const DisplayItemClientWrapper& client, const LayoutPoint& paintOffset)
+    static void updatePaintOffsetIfNeeded(DisplayItemList* displayItemList, const LayoutObject& layoutObject, const LayoutPoint& paintOffset)

[pdr., 2015/09/23 19:55:47]

WDYT about changing this LayoutObject to be non-const so we can remove the
mutable on previous paint offset?

[Xianzhu, 2015/09/23 21:39:44]

I think making LayoutObject const for painters can avoid unexpected mutation
during painting.

I would leave the following discussion for later CLs:

Perhaps we can make the mutable part of LayoutObject more explicit for painting,
e.g.:

In LayoutObject:
  class MutableForPainting {
  public:
      void setPreviousPaintOffset() { m_layoutObject.setPreviousPaintOffset(); }
      ...
  private:
      friend class LayoutObject;
      MutableForPainting(const LayoutObject& layoutObject)
          : m_layoutObject(const_cast<LayoutObject&>(layoutObject) {}
      LayoutObject& m_layoutObject;
  };

  MutableForPainting mutableForPainting() const {
      ASSERT(lifecycle is in painting);
      return MutableForPainting(this);
  }

In Painter:
  layoutObject.mutableForPainting().setPreviousPaintOffset();

wdyt?

     {
         if (!RuntimeEnabledFeatures::slimmingPaintOffsetCachingEnabled())
             return;
 
-        // TODO(pdr): The paint offset cache should be stored on LayoutObject but is temporarily on the DisplayItemList.
-        if (!displayItemList->paintOffsetIsUnchanged(client.displayItemClient(), paintOffset)) {
-            displayItemList->recordPaintOffset(client.displayItemClient(), paintOffset);
-            displayItemList->invalidatePaintOffset(client);
-        } else {
-            ASSERT(!displayItemList->paintOffsetWasInvalidated(client.displayItemClient()) || !displayItemList->clientCacheIsValid(client.displayItemClient()));
-        }
+        if (layoutObject.paintOffsetChanged(paintOffset))
+            displayItemList->invalidatePaintOffset(layoutObject);
+        else
+            ASSERT(!displayItemList->paintOffsetWasInvalidated(layoutObject.displayItemClient()) || !displayItemList->clientCacheIsValid(layoutObject.displayItemClient()));
+
+        layoutObject.setPreviousPaintOffset(paintOffset);
     }
 
     Optional<DisplayItemCacheSkipper> m_cacheSkipper;