Paint offset caching/change-detection for InlineBoxes

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 d2d455598c7e7e8db597f4de936b8c6f1daa6fc2..7660ac4eebeb4bc0cb0c57763af65394c675c45a 100644
--- a/Source/core/paint/LayoutObjectDrawingRecorder.h
+++ b/Source/core/paint/LayoutObjectDrawingRecorder.h
@@ -6,6 +6,7 @@
 #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"
@@ -37,6 +38,19 @@ 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::slimmingPaintV2Enabled() && !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)
     {
         if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
@@ -67,6 +81,30 @@ 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)

[pdr., 2015/09/14 21:27:42]

Can we use "const DisplayItemClientWrapper&" to avoid duplicating this logic?

If not, I really do not like templates, but this is one place where they may be
preferable because the paint offset logic will be getting more complex soon.

[Xianzhu, 2015/09/14 21:43:43]

There is a difference between the LayoutObject version and this version about
PaintInvalidationDelayedFull.

Extracted a private updatePaintOffsetIfNeeded() method.

+    {
+        if (RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+            // TODO(pdr): The paint offset cache should be stored on LayoutObject but is temporarily on the DisplayItemList.
+            if (!context.displayItemList()->paintOffsetIsUnchanged(inlineBox.displayItemClient(), paintOffset)) {
+                context.displayItemList()->recordPaintOffset(inlineBox.displayItemClient(), paintOffset);
+                context.displayItemList()->invalidatePaintOffset(inlineBox.displayItemClient());
+            } else {
+                ASSERT(!context.displayItemList()->paintOffsetWasInvalidated(inlineBox.displayItemClient()) || !context.displayItemList()->clientCacheIsValid(inlineBox.displayItemClient()));
+            }
+        }
+
+        m_drawingRecorder.emplace(context, inlineBox, displayItemType, clip);
+    }
+
+    LayoutObjectDrawingRecorder(GraphicsContext& context, const InlineBox& inlineBox, DisplayItem::Type displayItemType, const LayoutRect& clip, const LayoutPoint& paintOffset)

[pdr., 2015/09/14 21:27:42]

Lets not add these overloaded ctors unless they are used.

[Xianzhu, 2015/09/14 21:43:43]

3 of the 4 constructors are used by painters, and the other 1 is used by the 3.

+        : 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