[SPv2] Adds pre-computed paint property context to PaintLayer.

third_party/WebKit/Source/core/paint/PaintLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 39 matching lines @@
 #include "core/layout/LayoutBox.h"
 #include "core/paint/PaintLayerClipper.h"
 #include "core/paint/PaintLayerFilterInfo.h"
 #include "core/paint/PaintLayerFragment.h"
 #include "core/paint/PaintLayerPainter.h"
 #include "core/paint/PaintLayerReflectionInfo.h"
 #include "core/paint/PaintLayerScrollableArea.h"
 #include "core/paint/PaintLayerStackingNode.h"
 #include "core/paint/PaintLayerStackingNodeIterator.h"
 #include "platform/graphics/CompositingReasons.h"
+#include "platform/graphics/paint/PaintChunkProperties.h"
 #include "public/platform/WebBlendMode.h"
 #include "wtf/Allocator.h"
 #include "wtf/OwnPtr.h"
 
 namespace blink {
 
 class CompositedLayerMapping;
 class ComputedStyle;
 class FilterEffectBuilder;
 class FilterOperations;
@@ skipping 53 matching lines @@
 
     // If the layer paints into grouped backing (i.e. squashed), this points to the
     // grouped CompositedLayerMapping. It's null if the layer is not composited or
     // paints into its own backing.
     CompositedLayerMapping* groupedMapping;
 
     OwnPtr<PaintLayerReflectionInfo> reflectionInfo;
 
     // The accumulated subpixel offset of a composited layer's composited bounds compared to absolute coordinates.
     LayoutSize subpixelAccumulation;
+
+    struct CachedSPv2PaintParameters {
+        LayoutPoint paintOffset;
+        PaintChunkProperties properties;
+    } cachedSPv2PaintParameters;

[pdr., 2016/02/02 06:18:20]

Is this data actually rare or is it just on raredata temporarily?

Can you add a short comment above CachedSPv2PaintParameters explaining what it's
for?

We can name this something better than CachedSPv2PaintParameters, but I don't
understand this patch well enough to make a suggestion. If this is just for
overflow clip, maybe something like CachedSPv2OverflowClipPaintState?

[trchen, 2016/02/02 21:48:53]

It will be no longer rare once SPv2 ships. :)
Acknowledged.
Yea... The variable name is too generic. Having the code name SPv2 in there
isn't good either. However it is not exclusive for overflow either, as I'm
planning to include paint context for fixed-pos descendants in the future (for
background-attachment:fixed). Does CachedLayerPaintPropertyContext sound better?

 };
 
 // PaintLayer is an old object that handles lots of unrelated operations.
 //
 // We want it to die at some point and be replaced by more focused objects,
 // which would remove (or at least compartimentalize) a lot of complexity.
 // See the STATUS OF PAINTLAYER section below.
 //
 // The class is central to painting and hit-testing. That's because it handles
 // a lot of tasks (we included ones done by associated satellite objects for
@@ skipping 529 matching lines @@
 
     ClipRectsCache* clipRectsCache() const { return m_clipRectsCache.get(); }
     ClipRectsCache& ensureClipRectsCache() const
     {
         if (!m_clipRectsCache)
             m_clipRectsCache = adoptPtr(new ClipRectsCache);
         return *m_clipRectsCache;
     }
     void clearClipRectsCache() const { m_clipRectsCache.clear(); }
 
+    const PaintLayerRareData::CachedSPv2PaintParameters& cachedSPv2PaintParameters() const { ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled()); ASSERT(m_rareData); return m_rareData->cachedSPv2PaintParameters; }

[pdr., 2016/02/02 06:18:20]

WDYT about some lifecycle asserts here?

For the accessor, something like ASSERT(DocumentLifecycle::InPaint)?

For the setter, something like
ASSERT(DocumentLifecycle::InUpdatePaintProperties)?

[trchen, 2016/02/02 21:48:53]

Acknowledged. Hey, fantastic idea!

+    PaintLayerRareData::CachedSPv2PaintParameters& accessCachedSPv2PaintParameters() { ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled()); return ensureRareData().cachedSPv2PaintParameters; }
+
 private:
     // Bounding box in the coordinates of this layer.
     LayoutRect logicalBoundingBox() const;
 
     bool hasOverflowControls() const;
 
     void dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
 
     // Returns true if the position changed.
     bool updateLayerPosition();
@@ skipping 170 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const blink::PaintLayer*);
 void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif // Layer_h