Monitor the intersection of video and viewport.

third_party/WebKit/Source/core/dom/IntersectionObserver.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 IntersectionObserver_h
 #define IntersectionObserver_h
 
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/dom/IntersectionObservation.h"
 #include "core/dom/IntersectionObserverEntry.h"
 #include "platform/Length.h"
 #include "platform/heap/Handle.h"
 #include "wtf/HashSet.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class Document;
 class Element;
 class ExceptionState;
 class LayoutObject;
 class IntersectionObserverCallback;
 class IntersectionObserverInit;
 
-class CORE_EXPORT IntersectionObserver final
+class CORE_EXPORT IntersectionObserver
     : public GarbageCollectedFinalized<IntersectionObserver>,
       public ScriptWrappable {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
+  virtual ~IntersectionObserver();
+
   using EventCallback =
       Function<void(const HeapVector<Member<IntersectionObserverEntry>>&),
                WTF::SameThreadAffinity>;
 
   // Defines the assumed initial state of the observed element. If the actual
   // state is the same as the initial state, then no observation will be
   // delivered. kAuto means the initial observation will always get sent.
   enum class InitialState {
     // TODO(skyostil): Add support for kVisible.
     kAuto,
     kHidden,
   };
 
   static IntersectionObserver* create(const IntersectionObserverInit&,
                                       IntersectionObserverCallback&,
                                       ExceptionState&);
+  // Observes any changes on intersection rect when |thresholds| is empty.
   static IntersectionObserver* create(const Vector<Length>& rootMargin,
                                       const Vector<float>& thresholds,
                                       Document*,
                                       std::unique_ptr<EventCallback>,
                                       ExceptionState& = ASSERT_NO_EXCEPTION);
   static void resumeSuspendedObservers();
 
   // API methods.
   void observe(Element*, ExceptionState& = ASSERT_NO_EXCEPTION);
   void unobserve(Element*, ExceptionState& = ASSERT_NO_EXCEPTION);
@@ skipping 24 matching lines @@
   }
 
   // Set the assumed initial state of the observed element. Note that this can
   // only be set before calling observe().
   // TODO(skyostil): Move this setting to IntersectionObserverInit once the API
   // is finalized.
   void setInitialState(InitialState);
 
   DECLARE_TRACE();
 
+ protected:
+  virtual IntersectionObservation* createObservation(Element&, bool);
+
+  IntersectionObserver(IntersectionObserverCallback&,
+                       Node&,
+                       const Vector<Length>& rootMargin,
+                       const Vector<float>& thresholds);
+
  private:
-  explicit IntersectionObserver(IntersectionObserverCallback&,
-                                Node&,
-                                const Vector<Length>& rootMargin,
-                                const Vector<float>& thresholds);
   void clearWeakMembers(Visitor*);
 
   Member<IntersectionObserverCallback> m_callback;
   WeakMember<Node> m_root;
   HeapLinkedHashSet<WeakMember<IntersectionObservation>> m_observations;
   HeapVector<Member<IntersectionObserverEntry>> m_entries;
   Vector<float> m_thresholds;
   Length m_topMargin;
   Length m_rightMargin;
   Length m_bottomMargin;
   Length m_leftMargin;
   InitialState m_initialState;
 };
 
+class ViewportIntersectionObserver final : public IntersectionObserver {
+  WTF_MAKE_NONCOPYABLE(ViewportIntersectionObserver);
+
+ public:
+  ViewportIntersectionObserver(IntersectionObserverCallback&,
+                               Node&,
+                               const Vector<Length>&);
+  ~ViewportIntersectionObserver() final;
+
+ protected:
+  IntersectionObservation* createObservation(Element&, bool) final;
+};
+
 }  // namespace blink
 
 #endif  // IntersectionObserver_h