SnapManager implementation using V8 Extras - {WIP}

third_party/WebKit/Source/core/page/scrolling/SnapCoordinator.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SnapCoordinator_h
 #define SnapCoordinator_h
 
 #include "core/CoreExport.h"
 #include "core/css/CSSPrimitiveValueMappings.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class ComputedStyle;
 class ContainerNode;
 class Element;
 class LayoutBox;
 struct LengthPoint;
+class SnapManager;
+
+struct SnapOffsets {
+    Vector<double> horizontal;
+    Vector<double> vertical;
+};
 
 // Snap Coordinator keeps track of snap containers and all of their associated
 // snap areas. It also contains the logic to generate the list of valid snap
 // positions for a given snap container.
 //
 // Snap container:
 //   An scroll container that has 'scroll-snap-type' value other
 //   than 'none'.
 // Snap area:
 //   A snap container's descendant that contributes snap positions. An element
 //   only contributes snap positions to its nearest ancestor (on the element’s
 //   containing block chain) scroll container.
 //
 // For more information see spec: https://drafts.csswg.org/css-snappoints/
 class CORE_EXPORT SnapCoordinator final : public GarbageCollectedFinalized<SnapCoordinator> {
     WTF_MAKE_NONCOPYABLE(SnapCoordinator);
+public:
+    class Client {
+    public:
+        virtual void didUpdateSnapOffsets(const LayoutBox&, SnapOffsets) = 0;
+    };
 
-public:
-    static SnapCoordinator* create();
+    static SnapCoordinator* create(Client*);
     ~SnapCoordinator();
     DEFINE_INLINE_TRACE() {}
 
     void snapContainerDidChange(LayoutBox&, ScrollSnapType);
     void snapAreaDidChange(LayoutBox&, const Vector<LengthPoint>& snapCoordinates);
 
+    void notifyLayoutUpdated();
+    void clear();
+
 #ifndef NDEBUG
     void showSnapAreaMap();
     void showSnapAreasFor(const LayoutBox*);
 #endif
 
 private:
     friend class SnapCoordinatorTest;
-    explicit SnapCoordinator();
+    explicit SnapCoordinator(Client*);
 
     Vector<double> snapOffsets(const ContainerNode&, ScrollbarOrientation);
 
     HashSet<const LayoutBox*> m_snapContainers;
+    HashMap<const LayoutBox*, SnapOffsets> m_offsetMap;
+    Client* m_client;
+
 };
 
+bool operator==(const SnapOffsets&, const SnapOffsets&);
+
 } // namespace blink
 
 #endif // SnapCoordinator_h