Source/WebCore/page/scrolling/ScrollingStateNode.h - WebKit - Git at Google

 /*
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  * THE POSSIBILITY OF SUCH DAMAGE.
  */

 #pragma once

 #if ENABLE(ASYNC_SCROLLING)

 #include "GraphicsLayer.h"
 #include "ScrollingCoordinator.h"
 #include <stdint.h>
 #include <wtf/ThreadSafeRefCounted.h>
 #include <wtf/TypeCasts.h>
 #include <wtf/Vector.h>

 namespace WTF {
 class TextStream;
 }

 namespace WebCore {

 class GraphicsLayer;
 class ScrollingStateTree;

 // Used to allow ScrollingStateNodes to refer to layers in various contexts:
 // a) Async scrolling, main thread: ScrollingStateNode holds onto a GraphicsLayer, and uses m_layerID
 //    to detect whether that GraphicsLayer's underlying PlatformLayer changed.
 // b) Threaded scrolling, commit to scrolling thread: ScrollingStateNode wraps a PlatformLayer, which
 //    can be passed to the Scrolling Thread
 // c) Remote scrolling UI process, where LayerRepresentation wraps just a PlatformLayerID.
 class LayerRepresentation {
 public:
     enum Type {
         EmptyRepresentation,
         GraphicsLayerRepresentation,
         PlatformLayerRepresentation,
         PlatformLayerIDRepresentation
     };

     LayerRepresentation() = default;

     LayerRepresentation(GraphicsLayer* graphicsLayer)
         : m_graphicsLayer(graphicsLayer)
         , m_layerID(graphicsLayer ? graphicsLayer->primaryLayerID() : 0)
         , m_representation(GraphicsLayerRepresentation)
     { }

     LayerRepresentation(PlatformLayer* platformLayer)
         : m_typelessPlatformLayer(makePlatformLayerTypeless(platformLayer))
         , m_representation(PlatformLayerRepresentation)
     {
         retainPlatformLayer(m_typelessPlatformLayer);
     }

     LayerRepresentation(GraphicsLayer::PlatformLayerID layerID)
         : m_layerID(layerID)
         , m_representation(PlatformLayerIDRepresentation)
     {
     }

     LayerRepresentation(const LayerRepresentation& other)
         : m_typelessPlatformLayer(other.m_typelessPlatformLayer)
         , m_layerID(other.m_layerID)
         , m_representation(other.m_representation)
     {
         if (m_representation == PlatformLayerRepresentation)
             retainPlatformLayer(m_typelessPlatformLayer);
     }

     ~LayerRepresentation()
     {
         if (m_representation == PlatformLayerRepresentation)
             releasePlatformLayer(m_typelessPlatformLayer);
     }

     explicit operator GraphicsLayer*() const
     {
         ASSERT(m_representation == GraphicsLayerRepresentation);
         return m_graphicsLayer.get();
     }

     explicit operator PlatformLayer*() const
     {
         ASSERT(m_representation == PlatformLayerRepresentation);
         return makePlatformLayerTyped(m_typelessPlatformLayer);
     }

     GraphicsLayer::PlatformLayerID layerID() const
     {
         return m_layerID;
     }

     explicit operator GraphicsLayer::PlatformLayerID() const
     {
         ASSERT(m_representation != PlatformLayerRepresentation);
         return m_layerID;
     }

     LayerRepresentation& operator=(const LayerRepresentation& other)
     {
         m_graphicsLayer = other.m_graphicsLayer;
         m_typelessPlatformLayer = other.m_typelessPlatformLayer;
         m_layerID = other.m_layerID;
         m_representation = other.m_representation;

         if (m_representation == PlatformLayerRepresentation)
             retainPlatformLayer(m_typelessPlatformLayer);

         return *this;
     }

     explicit operator bool() const
     {
         switch (m_representation) {
         case EmptyRepresentation:
             return false;
         case GraphicsLayerRepresentation:
             return !!m_graphicsLayer;
         case PlatformLayerRepresentation:
             return !!m_typelessPlatformLayer;
         case PlatformLayerIDRepresentation:
             return !!m_layerID;
         }
         ASSERT_NOT_REACHED();
         return false;
     }

     bool operator==(const LayerRepresentation& other) const
     {
         if (m_representation != other.m_representation)
             return false;
         switch (m_representation) {
         case EmptyRepresentation:
             return true;
         case GraphicsLayerRepresentation:
             return m_graphicsLayer == other.m_graphicsLayer
                 && m_layerID == other.m_layerID;
         case PlatformLayerRepresentation:
             return m_typelessPlatformLayer == other.m_typelessPlatformLayer;
         case PlatformLayerIDRepresentation:
             return m_layerID == other.m_layerID;
         }
         ASSERT_NOT_REACHED();
         return true;
     }

     LayerRepresentation toRepresentation(Type representation) const
     {
         switch (representation) {
         case EmptyRepresentation:
             return LayerRepresentation();
         case GraphicsLayerRepresentation:
             ASSERT(m_representation == GraphicsLayerRepresentation);
             return LayerRepresentation(m_graphicsLayer.get());
         case PlatformLayerRepresentation:
             return m_graphicsLayer ? m_graphicsLayer->platformLayer() : nullptr;
         case PlatformLayerIDRepresentation:
             return LayerRepresentation(m_layerID);
         }
         ASSERT_NOT_REACHED();
         return LayerRepresentation();
     }

     bool representsGraphicsLayer() const { return m_representation == GraphicsLayerRepresentation; }
     bool representsPlatformLayerID() const { return m_representation == PlatformLayerIDRepresentation; }

 private:
     WEBCORE_EXPORT static void retainPlatformLayer(void* typelessPlatformLayer);
     WEBCORE_EXPORT static void releasePlatformLayer(void* typelessPlatformLayer);
     WEBCORE_EXPORT static PlatformLayer* makePlatformLayerTyped(void* typelessPlatformLayer);
     WEBCORE_EXPORT static void* makePlatformLayerTypeless(PlatformLayer*);

     RefPtr<GraphicsLayer> m_graphicsLayer;
     void* m_typelessPlatformLayer { nullptr };
     GraphicsLayer::PlatformLayerID m_layerID { 0 };
     Type m_representation { EmptyRepresentation };
 };

 class ScrollingStateNode : public ThreadSafeRefCounted<ScrollingStateNode> {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     virtual ~ScrollingStateNode();

     ScrollingNodeType nodeType() const { return m_nodeType; }

     bool isFixedNode() const { return m_nodeType == ScrollingNodeType::Fixed; }
     bool isStickyNode() const { return m_nodeType == ScrollingNodeType::Sticky; }
     bool isPositionedNode() const { return m_nodeType == ScrollingNodeType::Positioned; }
     bool isScrollingNode() const { return isFrameScrollingNode() || isOverflowScrollingNode(); }
     bool isFrameScrollingNode() const { return m_nodeType == ScrollingNodeType::MainFrame || m_nodeType == ScrollingNodeType::Subframe; }
     bool isFrameHostingNode() const { return m_nodeType == ScrollingNodeType::FrameHosting; }
     bool isOverflowScrollingNode() const { return m_nodeType == ScrollingNodeType::Overflow; }
     bool isOverflowScrollProxyNode() const { return m_nodeType == ScrollingNodeType::OverflowProxy; }

     virtual Ref<ScrollingStateNode> clone(ScrollingStateTree& adoptiveTree) = 0;
     Ref<ScrollingStateNode> cloneAndReset(ScrollingStateTree& adoptiveTree);
     void cloneAndResetChildren(ScrollingStateNode&, ScrollingStateTree& adoptiveTree);

     // FIXME: using an OptionSet<> for these and derived class bits would simplify code.
     enum {
         Layer = 0,
         ChildNodes,
         NumStateNodeBits // This must remain at the last position.
     };
     typedef uint64_t ChangedProperties;

     bool hasChangedProperties() const { return m_changedProperties; }
     bool hasChangedProperty(unsigned propertyBit) const { return m_changedProperties & (static_cast<ChangedProperties>(1) << propertyBit); }
     void resetChangedProperties() { m_changedProperties = 0; }
     void setPropertyChanged(unsigned propertyBit);
     virtual void setPropertyChangedBitsAfterReattach();

     ChangedProperties changedProperties() const { return m_changedProperties; }
     void setChangedProperties(ChangedProperties changedProperties) { m_changedProperties = changedProperties; }

     virtual void reconcileLayerPositionForViewportRect(const LayoutRect& /*viewportRect*/, ScrollingLayerPositionAction) { }

     const LayerRepresentation& layer() const { return m_layer; }
     WEBCORE_EXPORT void setLayer(const LayerRepresentation&);

     ScrollingStateTree& scrollingStateTree() const { return m_scrollingStateTree; }

     ScrollingNodeID scrollingNodeID() const { return m_nodeID; }

     ScrollingStateNode* parent() const { return m_parent; }
     void setParent(ScrollingStateNode* parent) { m_parent = parent; }
     ScrollingNodeID parentNodeID() const { return m_parent ? m_parent->scrollingNodeID() : 0; }

     Vector<RefPtr<ScrollingStateNode>>* children() const { return m_children.get(); }
     std::unique_ptr<Vector<RefPtr<ScrollingStateNode>>> takeChildren() { return WTFMove(m_children); }

     void appendChild(Ref<ScrollingStateNode>&&);
     void insertChild(Ref<ScrollingStateNode>&&, size_t index);

     // Note that node ownership is via the parent, so these functions can trigger node deletion.
     void removeFromParent();
     void removeChildAtIndex(size_t index);
     void removeChild(ScrollingStateNode&);

     size_t indexOfChild(ScrollingStateNode&) const;

     String scrollingStateTreeAsText(ScrollingStateTreeAsTextBehavior = ScrollingStateTreeAsTextBehaviorNormal) const;

 protected:
     ScrollingStateNode(const ScrollingStateNode&, ScrollingStateTree&);
     ScrollingStateNode(ScrollingNodeType, ScrollingStateTree&, ScrollingNodeID);

     virtual void dumpProperties(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const;

     inline void setPropertyChangedBit(unsigned propertyBit);

 private:
     void dump(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const;

     const ScrollingNodeType m_nodeType;
     const ScrollingNodeID m_nodeID;
     ChangedProperties m_changedProperties { 0 };

     ScrollingStateTree& m_scrollingStateTree;

     ScrollingStateNode* m_parent { nullptr };
     std::unique_ptr<Vector<RefPtr<ScrollingStateNode>>> m_children;

     LayerRepresentation m_layer;
 };

 void ScrollingStateNode::setPropertyChangedBit(unsigned propertyBit)
 {
     m_changedProperties |= (static_cast<ChangedProperties>(1) << propertyBit);
 }

 } // namespace WebCore

 #define SPECIALIZE_TYPE_TRAITS_SCROLLING_STATE_NODE(ToValueTypeName, predicate) \
 SPECIALIZE_TYPE_TRAITS_BEGIN(WebCore::ToValueTypeName) \
     static bool isType(const WebCore::ScrollingStateNode& node) { return node.predicate; } \
 SPECIALIZE_TYPE_TRAITS_END()

 #endif // ENABLE(ASYNC_SCROLLING)
	/*
	* Copyright (C) 2012 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
	* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
	* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
	* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
	* THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#pragma once

	#if ENABLE(ASYNC_SCROLLING)

	#include "GraphicsLayer.h"
	#include "ScrollingCoordinator.h"
	#include <stdint.h>
	#include <wtf/ThreadSafeRefCounted.h>
	#include <wtf/TypeCasts.h>
	#include <wtf/Vector.h>

	namespace WTF {
	class TextStream;
	}

	namespace WebCore {

	class GraphicsLayer;
	class ScrollingStateTree;

	// Used to allow ScrollingStateNodes to refer to layers in various contexts:
	// a) Async scrolling, main thread: ScrollingStateNode holds onto a GraphicsLayer, and uses m_layerID
	// to detect whether that GraphicsLayer's underlying PlatformLayer changed.
	// b) Threaded scrolling, commit to scrolling thread: ScrollingStateNode wraps a PlatformLayer, which
	// can be passed to the Scrolling Thread
	// c) Remote scrolling UI process, where LayerRepresentation wraps just a PlatformLayerID.
	class LayerRepresentation {
	public:
	enum Type {
	EmptyRepresentation,
	GraphicsLayerRepresentation,
	PlatformLayerRepresentation,
	PlatformLayerIDRepresentation
	};

	LayerRepresentation() = default;

	LayerRepresentation(GraphicsLayer* graphicsLayer)
	: m_graphicsLayer(graphicsLayer)
	, m_layerID(graphicsLayer ? graphicsLayer->primaryLayerID() : 0)
	, m_representation(GraphicsLayerRepresentation)
	{ }

	LayerRepresentation(PlatformLayer* platformLayer)
	: m_typelessPlatformLayer(makePlatformLayerTypeless(platformLayer))
	, m_representation(PlatformLayerRepresentation)
	{
	retainPlatformLayer(m_typelessPlatformLayer);
	}

	LayerRepresentation(GraphicsLayer::PlatformLayerID layerID)
	: m_layerID(layerID)
	, m_representation(PlatformLayerIDRepresentation)
	{
	}

	LayerRepresentation(const LayerRepresentation& other)
	: m_typelessPlatformLayer(other.m_typelessPlatformLayer)
	, m_layerID(other.m_layerID)
	, m_representation(other.m_representation)
	{
	if (m_representation == PlatformLayerRepresentation)
	retainPlatformLayer(m_typelessPlatformLayer);
	}

	~LayerRepresentation()
	{
	if (m_representation == PlatformLayerRepresentation)
	releasePlatformLayer(m_typelessPlatformLayer);
	}

	explicit operator GraphicsLayer*() const
	{
	ASSERT(m_representation == GraphicsLayerRepresentation);
	return m_graphicsLayer.get();
	}

	explicit operator PlatformLayer*() const
	{
	ASSERT(m_representation == PlatformLayerRepresentation);
	return makePlatformLayerTyped(m_typelessPlatformLayer);
	}

	GraphicsLayer::PlatformLayerID layerID() const
	{
	return m_layerID;
	}

	explicit operator GraphicsLayer::PlatformLayerID() const
	{
	ASSERT(m_representation != PlatformLayerRepresentation);
	return m_layerID;
	}

	LayerRepresentation& operator=(const LayerRepresentation& other)
	{
	m_graphicsLayer = other.m_graphicsLayer;
	m_typelessPlatformLayer = other.m_typelessPlatformLayer;
	m_layerID = other.m_layerID;
	m_representation = other.m_representation;

	if (m_representation == PlatformLayerRepresentation)
	retainPlatformLayer(m_typelessPlatformLayer);

	return *this;
	}

	explicit operator bool() const
	{
	switch (m_representation) {
	case EmptyRepresentation:
	return false;
	case GraphicsLayerRepresentation:
	return !!m_graphicsLayer;
	case PlatformLayerRepresentation:
	return !!m_typelessPlatformLayer;
	case PlatformLayerIDRepresentation:
	return !!m_layerID;
	}
	ASSERT_NOT_REACHED();
	return false;
	}

	bool operator==(const LayerRepresentation& other) const
	{
	if (m_representation != other.m_representation)
	return false;
	switch (m_representation) {
	case EmptyRepresentation:
	return true;
	case GraphicsLayerRepresentation:
	return m_graphicsLayer == other.m_graphicsLayer
	&& m_layerID == other.m_layerID;
	case PlatformLayerRepresentation:
	return m_typelessPlatformLayer == other.m_typelessPlatformLayer;
	case PlatformLayerIDRepresentation:
	return m_layerID == other.m_layerID;
	}
	ASSERT_NOT_REACHED();
	return true;
	}

	LayerRepresentation toRepresentation(Type representation) const
	{
	switch (representation) {
	case EmptyRepresentation:
	return LayerRepresentation();
	case GraphicsLayerRepresentation:
	ASSERT(m_representation == GraphicsLayerRepresentation);
	return LayerRepresentation(m_graphicsLayer.get());
	case PlatformLayerRepresentation:
	return m_graphicsLayer ? m_graphicsLayer->platformLayer() : nullptr;
	case PlatformLayerIDRepresentation:
	return LayerRepresentation(m_layerID);
	}
	ASSERT_NOT_REACHED();
	return LayerRepresentation();
	}

	bool representsGraphicsLayer() const { return m_representation == GraphicsLayerRepresentation; }
	bool representsPlatformLayerID() const { return m_representation == PlatformLayerIDRepresentation; }

	private:
	WEBCORE_EXPORT static void retainPlatformLayer(void* typelessPlatformLayer);
	WEBCORE_EXPORT static void releasePlatformLayer(void* typelessPlatformLayer);
	WEBCORE_EXPORT static PlatformLayer* makePlatformLayerTyped(void* typelessPlatformLayer);
	WEBCORE_EXPORT static void* makePlatformLayerTypeless(PlatformLayer*);

	RefPtr<GraphicsLayer> m_graphicsLayer;
	void* m_typelessPlatformLayer { nullptr };
	GraphicsLayer::PlatformLayerID m_layerID { 0 };
	Type m_representation { EmptyRepresentation };
	};

	class ScrollingStateNode : public ThreadSafeRefCounted<ScrollingStateNode> {
	WTF_MAKE_FAST_ALLOCATED;
	public:
	virtual ~ScrollingStateNode();

	ScrollingNodeType nodeType() const { return m_nodeType; }

	bool isFixedNode() const { return m_nodeType == ScrollingNodeType::Fixed; }
	bool isStickyNode() const { return m_nodeType == ScrollingNodeType::Sticky; }
	bool isPositionedNode() const { return m_nodeType == ScrollingNodeType::Positioned; }
	bool isScrollingNode() const { return isFrameScrollingNode() \|\| isOverflowScrollingNode(); }
	bool isFrameScrollingNode() const { return m_nodeType == ScrollingNodeType::MainFrame \|\| m_nodeType == ScrollingNodeType::Subframe; }
	bool isFrameHostingNode() const { return m_nodeType == ScrollingNodeType::FrameHosting; }
	bool isOverflowScrollingNode() const { return m_nodeType == ScrollingNodeType::Overflow; }
	bool isOverflowScrollProxyNode() const { return m_nodeType == ScrollingNodeType::OverflowProxy; }

	virtual Ref<ScrollingStateNode> clone(ScrollingStateTree& adoptiveTree) = 0;
	Ref<ScrollingStateNode> cloneAndReset(ScrollingStateTree& adoptiveTree);
	void cloneAndResetChildren(ScrollingStateNode&, ScrollingStateTree& adoptiveTree);

	// FIXME: using an OptionSet<> for these and derived class bits would simplify code.
	enum {
	Layer = 0,
	ChildNodes,
	NumStateNodeBits // This must remain at the last position.
	};
	typedef uint64_t ChangedProperties;

	bool hasChangedProperties() const { return m_changedProperties; }
	bool hasChangedProperty(unsigned propertyBit) const { return m_changedProperties & (static_cast<ChangedProperties>(1) << propertyBit); }
	void resetChangedProperties() { m_changedProperties = 0; }
	void setPropertyChanged(unsigned propertyBit);
	virtual void setPropertyChangedBitsAfterReattach();

	ChangedProperties changedProperties() const { return m_changedProperties; }
	void setChangedProperties(ChangedProperties changedProperties) { m_changedProperties = changedProperties; }

	virtual void reconcileLayerPositionForViewportRect(const LayoutRect& /viewportRect/, ScrollingLayerPositionAction) { }

	const LayerRepresentation& layer() const { return m_layer; }
	WEBCORE_EXPORT void setLayer(const LayerRepresentation&);

	ScrollingStateTree& scrollingStateTree() const { return m_scrollingStateTree; }

	ScrollingNodeID scrollingNodeID() const { return m_nodeID; }

	ScrollingStateNode* parent() const { return m_parent; }
	void setParent(ScrollingStateNode* parent) { m_parent = parent; }
	ScrollingNodeID parentNodeID() const { return m_parent ? m_parent->scrollingNodeID() : 0; }

	Vector<RefPtr<ScrollingStateNode>>* children() const { return m_children.get(); }
	std::unique_ptr<Vector<RefPtr<ScrollingStateNode>>> takeChildren() { return WTFMove(m_children); }

	void appendChild(Ref<ScrollingStateNode>&&);
	void insertChild(Ref<ScrollingStateNode>&&, size_t index);

	// Note that node ownership is via the parent, so these functions can trigger node deletion.
	void removeFromParent();
	void removeChildAtIndex(size_t index);
	void removeChild(ScrollingStateNode&);

	size_t indexOfChild(ScrollingStateNode&) const;

	String scrollingStateTreeAsText(ScrollingStateTreeAsTextBehavior = ScrollingStateTreeAsTextBehaviorNormal) const;

	protected:
	ScrollingStateNode(const ScrollingStateNode&, ScrollingStateTree&);
	ScrollingStateNode(ScrollingNodeType, ScrollingStateTree&, ScrollingNodeID);

	virtual void dumpProperties(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const;

	inline void setPropertyChangedBit(unsigned propertyBit);

	private:
	void dump(WTF::TextStream&, ScrollingStateTreeAsTextBehavior) const;

	const ScrollingNodeType m_nodeType;
	const ScrollingNodeID m_nodeID;
	ChangedProperties m_changedProperties { 0 };

	ScrollingStateTree& m_scrollingStateTree;

	ScrollingStateNode* m_parent { nullptr };
	std::unique_ptr<Vector<RefPtr<ScrollingStateNode>>> m_children;

	LayerRepresentation m_layer;
	};

	void ScrollingStateNode::setPropertyChangedBit(unsigned propertyBit)
	{
	m_changedProperties \|= (static_cast<ChangedProperties>(1) << propertyBit);
	}

	} // namespace WebCore

	#define SPECIALIZE_TYPE_TRAITS_SCROLLING_STATE_NODE(ToValueTypeName, predicate) \
	SPECIALIZE_TYPE_TRAITS_BEGIN(WebCore::ToValueTypeName) \
	static bool isType(const WebCore::ScrollingStateNode& node) { return node.predicate; } \
	SPECIALIZE_TYPE_TRAITS_END()

	#endif // ENABLE(ASYNC_SCROLLING)