Pass MotionEvent tilt angles to Blink on Android.

ui/events/gesture_detection/motion_event.h

 // Copyright 2014 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 UI_EVENTS_GESTURE_DETECTION_MOTION_EVENT_H_
 #define UI_EVENTS_GESTURE_DETECTION_MOTION_EVENT_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "ui/events/gesture_detection/gesture_detection_export.h"
@@ skipping 44 matching lines @@
   virtual size_t GetPointerCount() const = 0;
   virtual int GetPointerId(size_t pointer_index) const = 0;
   virtual float GetX(size_t pointer_index) const = 0;
   virtual float GetY(size_t pointer_index) const = 0;
   virtual float GetRawX(size_t pointer_index) const = 0;
   virtual float GetRawY(size_t pointer_index) const = 0;
   virtual float GetTouchMajor(size_t pointer_index) const = 0;
   virtual float GetTouchMinor(size_t pointer_index) const = 0;
   virtual float GetOrientation(size_t pointer_index) const = 0;
   virtual float GetPressure(size_t pointer_index) const = 0;
+  // TODO(e_hakkinen): Remove either GetTilt and GetTiltOrientation or GetTiltX
+  //                   and GetTiltY.
+  virtual float GetTilt(size_t pointer_index) const = 0;

[mustaq, 2015/06/17 20:01:27]

Since the discussion in crrev.com/1147083005 showed a strong support to keep the
MotionEvent interface as close to the Android spec as possible, I would add only
GetTilt() here, and untangle the overloaded orientation angle while converting
to other types, as I commented in blink_event_util.cc.

Sorry for my changed position in this regard.

Do you know if blink_event_util.cc is the only place to convert from MotionEvent
to other point-types? 

[USE eero AT chromium.org, 2015/06/18 11:34:07]

Done.

Initially I thought that WebTouchPoint to MotionEventWeb conversion very
complex,
but that conversion is actually used only for touch events and even if it would
be extended to all pointer events, conversion would not be that complex.
It would be enough to check signs of tiltX and tiltY. Trigonometry would not be
needed.
Seems to be so.

+  virtual float GetTiltOrientation(size_t pointer_index) const = 0;
+  virtual float GetTiltX(size_t pointer_index) const = 0;
+  virtual float GetTiltY(size_t pointer_index) const = 0;
   virtual ToolType GetToolType(size_t pointer_index) const = 0;
   virtual int GetButtonState() const = 0;
   virtual int GetFlags() const = 0;
   virtual base::TimeTicks GetEventTime() const = 0;
 
   // Optional historical data, default implementation provides an empty history.
   virtual size_t GetHistorySize() const;
   virtual base::TimeTicks GetHistoricalEventTime(size_t historical_index) const;
   virtual float GetHistoricalTouchMajor(size_t pointer_index,
                                         size_t historical_index) const;
@@ skipping 18 matching lines @@
   float GetTouchMinor() const { return GetTouchMinor(0); }
 
   // Returns the orientation in radians. The meaning is overloaded:
   // * For a touch screen or pad, it's the orientation of the major axis
   //   clockwise from vertical. The return value lies in [-PI/2, PI/2].
   // * For a stylus, it indicates the direction in which the stylus is pointing.
   //   The return value lies in [-PI, PI].
   float GetOrientation() const { return GetOrientation(0); }
 
   float GetPressure() const { return GetPressure(0); }
+
+  // TODO(e_hakkinen): Remove either GetTilt and GetTiltOrientation or GetTiltX
+  //                   and GetTiltY.
+  float GetTilt() const { return GetTilt(0); }
+  float GetTiltOrientation() const { return GetTiltOrientation(0); }
+  float GetTiltY() const { return GetTiltX(0); }
+  float GetTiltX() const { return GetTiltY(0); }
+
   ToolType GetToolType() const { return GetToolType(0); }
 
   // O(N) search of pointers (use sparingly!). Returns -1 if |id| nonexistent.
   int FindPointerIndexOfId(int id) const;
 
   // Note that these methods perform shallow copies of the originating events.
   // They guarantee only that the returned type will reflect the same
   // data exposed by the MotionEvent interface; no guarantees are made that the
   // underlying implementation is identical to the source implementation.
   scoped_ptr<MotionEvent> Clone() const;
   scoped_ptr<MotionEvent> Cancel() const;
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_MOTION_EVENT_H_