Canvas2d: Implement rerouting event by hit region's control.

third_party/WebKit/Source/platform/PlatformMouseEvent.h

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  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
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@@ skipping 11 matching lines @@
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  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef PlatformMouseEvent_h
 #define PlatformMouseEvent_h
 
 #include "platform/PlatformEvent.h"
 #include "platform/geometry/IntPoint.h"
 #include "public/platform/WebPointerProperties.h"
+#include "wtf/text/WTFString.h"
 
 namespace blink {
 
 // These button numbers match the ones used in the DOM API, 0 through 2, except for NoButton which is specified in PointerEvent
 // spec but not in MouseEvent spec.
 enum MouseButton { NoButton = -1, LeftButton, MiddleButton, RightButton };
 
 class PlatformMouseEvent : public PlatformEvent {
 public:
     enum SyntheticEventType {
@@ skipping 38 matching lines @@
     const WebPointerProperties& pointerProperties() const { return m_pointerProperties; }
     const IntPoint& position() const { return m_position; }
     const IntPoint& globalPosition() const { return m_globalPosition; }
     const IntPoint& movementDelta() const { return m_movementDelta; }
 
     MouseButton button() const { return m_button; }
     int clickCount() const { return m_clickCount; }
     bool fromTouch() const { return m_synthesized == FromTouch; }
     SyntheticEventType syntheticEventType() const { return m_synthesized; }
 
+    const String& region() const { return m_region; }
+    void setRegion(const String& region) { m_region = region; }
+
 protected:
     WebPointerProperties m_pointerProperties;
 
     // In local root frame coordinates. (Except possibly if the Widget under
     // the mouse is a popup, see FIXME in PlatformMouseEventBuilder).
     IntPoint m_position;
 
     // In screen coordinates.
     IntPoint m_globalPosition;
 
     IntPoint m_movementDelta;
     MouseButton m_button;
     int m_clickCount;
     SyntheticEventType m_synthesized;
+
+    // For canvas hit region.
+    String m_region;

[Rick Byers, 2016/02/23 20:26:08]

Conceptually this would probably make more sense to store in HitTestResults
(which is the other half of MouseEventWithHitTestResults).  But after spending
some time looking into the details of implementing that it seems like it's
probably more work than just stuffing it here (there are still a lot of places
we pass a PlatformMouseEvent instead of a MouseEventWithHitTestResults).

So I'm OK with taking a bit of a short-cut here to make this CL more tractable. 
I think it's worth tracking with a comment here though, maybe something like:
"This might make more sense to put in HitTestResults or some other part of
MouseEventWithHitTestResults, but for now it's most convenient to stash it
here.".

[zino, 2016/03/08 12:33:48]

Done.

I agree with you. I'll move the region data to HitTestResults or some other
parts in follow-up CL.
I left a comment and filed a bug for now.

[Rick Byers, 2016/03/08 15:57:34]

Thanks.  Note that I'm not convinced it's worth the effort / code churn to make
that change.  It would be nice to look into / experiment with, see if it's
practical to do cleanly without a TON of work.  But I don't consider it required
- storing it in PlatformMouseEvent isn't THAT bad, just a little bit of a hack.

 };
 
 } // namespace blink
 
 #endif // PlatformMouseEvent_h