Detect change on the intersection of video and viewport.

third_party/WebKit/Source/core/dom/IntersectionObservation.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 IntersectionObservation_h
 #define IntersectionObservation_h
 
 #include "core/dom/DOMHighResTimeStamp.h"
-#include "platform/geometry/LayoutRect.h"
+#include "core/dom/IntersectionGeometry.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class Element;
 class IntersectionObserver;
 
 class IntersectionObservation final
     : public GarbageCollected<IntersectionObservation> {
  public:
-  IntersectionObservation(IntersectionObserver&,
-                          Element&,
-                          bool shouldReportRootBounds);
-
-  struct IntersectionGeometry {
-    LayoutRect targetRect;
-    LayoutRect intersectionRect;
-    LayoutRect rootRect;
-    bool doesIntersect;
-
-    IntersectionGeometry() : doesIntersect(false) {}
-  };
+  IntersectionObservation(
+      IntersectionObserver&,
+      Element&,
+      IntersectionGeometry::ReportRootBounds shouldReportRootBounds);
 
   IntersectionObserver& observer() const { return *m_observer; }
   Element* target() const { return m_target; }
   unsigned lastThresholdIndex() const { return m_lastThresholdIndex; }
   void setLastThresholdIndex(unsigned index) { m_lastThresholdIndex = index; }
-  bool shouldReportRootBounds() const { return m_shouldReportRootBounds; }
   void computeIntersectionObservations(DOMHighResTimeStamp);
   void disconnect();
   void clearRootAndRemoveFromTarget();
 
   DECLARE_TRACE();
 
  private:
-  void applyRootMargin(LayoutRect&) const;
-  void initializeGeometry(IntersectionGeometry&) const;
-  void initializeTargetRect(LayoutRect&) const;
-  void initializeRootRect(LayoutRect&) const;
-  void clipToRoot(IntersectionGeometry&) const;
-  void mapTargetRectToTargetFrameCoordinates(LayoutRect&) const;
-  void mapRootRectToRootFrameCoordinates(LayoutRect&) const;
-  void mapRootRectToTargetFrameCoordinates(LayoutRect&) const;
-  bool computeGeometry(IntersectionGeometry&) const;
-
   Member<IntersectionObserver> m_observer;
-
   WeakMember<Element> m_target;
 
-  unsigned m_shouldReportRootBounds : 1;
-  unsigned m_lastThresholdIndex : 30;
+  IntersectionGeometry::ReportRootBounds m_shouldReportRootBounds;
+  unsigned m_lastThresholdIndex;

[ojan, 2016/11/24 03:06:06]

Please keep the : 1 and the : 30. That should work fine even though you're now
using an enum. Did it not?

As it is, this will take up 64/128 bits where it could instead take up 32/64
(the two numbers are for 32-bit and 64-bit builds).

[xjz, 2016/11/30 01:58:44]

Yes, it still only takes 1 bit. The only reason I removed that is because it
will cause the following pre-submit error:
check-webkit-style failed
  third_party/WebKit/Source/core/dom/IntersectionObservation.h:39:  Member
m_shouldReportRootBounds of class IntersectionObservation defined as a bitfield
of type IntersectionGeometry::ReportRootBounds. Please declare all bitfields as
unsigned.  [runtime/bitfields] [4]

In order to keep this, I added converters to convert between bool and the enum.

[miu, 2016/11/30 03:40:36]

You can make it unsigned. Just initialize it in the ctor as:

  ...,
  m_shouldReportRootBounds(shouldReportRootBounds == kShouldReportRootBounds),
  ...,

and this member should be const, right?

[xjz, 2016/11/30 07:05:54]

Yes, that is what toShouldReportRootBounds() does. And we need to convert it
back to the enum when create IntersectionGeometry. It seems the helpers are not
necessary, since both are only called once. Removed them and instead put codes
where they are called.

Also marked |m_shouldReportRootBounds| as const.

 };
 
 }  // namespace blink
 
 #endif  // IntersectionObservation_h