Changing the bounding box for show press and tap gesture

ui/events/gesture_detection/gesture_detector.h

Index: ui/events/gesture_detection/gesture_detector.h
diff --git a/ui/events/gesture_detection/gesture_detector.h b/ui/events/gesture_detection/gesture_detector.h
index db665f8cbcd84a1b95ceed6b93bba050ecaf16ed..ac077c4067d326fcb63977f21c695380deeaa16a 100644
--- a/ui/events/gesture_detection/gesture_detector.h
+++ b/ui/events/gesture_detection/gesture_detector.h
@@ -72,8 +72,11 @@ class GestureDetector {
    public:
     virtual ~GestureListener() {}
     virtual bool OnDown(const MotionEvent& e) = 0;
-    virtual void OnShowPress(const MotionEvent& e) = 0;
-    virtual bool OnSingleTapUp(const MotionEvent& e) = 0;
+    virtual void OnShowPress(const MotionEvent& e, float max_radius) = 0;
+    virtual bool OnSingleTapUp(const MotionEvent& e,

[jdduke (slow), 2014/09/04 15:01:25]

These callbacks variations are rather unfortunate, and I'm not sure we need to
couple the GestureDetector to our specific interpretation of how a press/tap
should be positioned. What if we instead do the necessary bookkeeping in the
GestureListenerImpl? 

+                               float x,
+                               float y,
+                               float max_radius) = 0;
     virtual void OnLongPress(const MotionEvent& e) = 0;
     virtual bool OnScroll(const MotionEvent& e1,
                           const MotionEvent& e2,
@@ -95,7 +98,10 @@ class GestureDetector {
   class DoubleTapListener {
    public:
     virtual ~DoubleTapListener() {}
-    virtual bool OnSingleTapConfirmed(const MotionEvent& e) = 0;
+    virtual bool OnSingleTapConfirmed(const MotionEvent& e,
+                                      float x,
+                                      float y,
+                                      float max_radius) = 0;
     virtual bool OnDoubleTap(const MotionEvent& e) = 0;
     virtual bool OnDoubleTapEvent(const MotionEvent& e) = 0;
   };
@@ -109,8 +115,11 @@ class GestureDetector {
    public:
     // GestureListener implementation.
     virtual bool OnDown(const MotionEvent& e) OVERRIDE;
-    virtual void OnShowPress(const MotionEvent& e) OVERRIDE;
-    virtual bool OnSingleTapUp(const MotionEvent& e) OVERRIDE;
+    virtual void OnShowPress(const MotionEvent& e, float max_radius) OVERRIDE;
+    virtual bool OnSingleTapUp(const MotionEvent& e,
+                               float x,
+                               float y,
+                               float max_radius) OVERRIDE;
     virtual void OnLongPress(const MotionEvent& e) OVERRIDE;
     virtual bool OnScroll(const MotionEvent& e1,
                           const MotionEvent& e2,
@@ -128,7 +137,10 @@ class GestureDetector {
                                 const MotionEvent& e2) OVERRIDE;
 
     // DoubleTapListener implementation.
-    virtual bool OnSingleTapConfirmed(const MotionEvent& e) OVERRIDE;
+    virtual bool OnSingleTapConfirmed(const MotionEvent& e,
+                                      float x,
+                                      float y,
+                                      float max_radius) OVERRIDE;
     virtual bool OnDoubleTap(const MotionEvent& e) OVERRIDE;
     virtual bool OnDoubleTapEvent(const MotionEvent& e) OVERRIDE;
   };
@@ -190,6 +202,10 @@ class GestureDetector {
   scoped_ptr<MotionEvent> previous_up_event_;
   scoped_ptr<MotionEvent> secondary_pointer_down_event_;
 
+  // The maximum diameter of the finger touches before show press gesture is
+  // sent.

[tdresser, 2014/09/04 13:54:00]

Perhaps:
// The maximum touch diameter before the show press gesture is sent.

[lanwei, 2014/09/05 20:40:36]

Done.

+  float max_touch_diameter_;

[tdresser, 2014/09/04 13:54:00]

Perhaps |max_diameter_before_show_press_|.

It's a little long, but I think it's better to be explicit here.

[lanwei, 2014/09/05 20:40:36]

Done.

+
   // True when the user is still touching for the second tap (down, move, and
   // up events). Can only be true if there is a double tap listener attached.
   bool is_double_tapping_;