Pass MotionEvent tilt angles to Blink on Android.

ui/events/blink/blink_event_util.cc

 // Copyright 2015 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.
 
 // MSVC++ requires this to be set before any other includes to get M_PI.
 #define _USE_MATH_DEFINES
 
 #include "ui/events/blink/blink_event_util.h"
 
 #include <cmath>
@@ skipping 107 matching lines @@
   // using two radii along x- & y-axes and a positive acute rotation angle in
   // degrees. See:
   // http://dvcs.w3.org/hg/webevents/raw-file/default/touchevents.html
 
   float major_radius = event.GetTouchMajor(pointer_index) / 2.f;
   float minor_radius = event.GetTouchMinor(pointer_index) / 2.f;
 
   DCHECK_LE(minor_radius, major_radius);
   DCHECK_IMPLIES(major_radius, minor_radius);
 
-  float orientation_deg = event.GetOrientation(pointer_index) * 180.f / M_PI;
+  float orientation_rad = event.GetOrientation(pointer_index);
+  float orientation_deg = orientation_rad * 180.f / M_PI;
   DCHECK_GE(major_radius, 0);
   DCHECK_GE(minor_radius, 0);
   DCHECK_GE(major_radius, minor_radius);
   // Orientation lies in [-180, 180] for a stylus, and [-90, 90] for other
   // touchscreen inputs. There are exceptions on Android when a device is
   // rotated, yielding touch orientations in the range of [-180, 180].
   // Regardless, normalise to [-90, 90), allowing a small tolerance to account
   // for floating point conversion.
   // TODO(e_hakkinen): Also pass unaltered stylus orientation, avoiding loss of
   // quadrant information, see crbug.com/493728.
@@ skipping 12 matching lines @@
     touch.radiusY = major_radius;
     touch.rotationAngle = orientation_deg;
   } else {
     touch.radiusX = major_radius;
     touch.radiusY = minor_radius;
     touch.rotationAngle = orientation_deg + 90;
   }
 
   touch.force = event.GetPressure(pointer_index);
 
+  if (event.GetToolType(pointer_index) == MotionEvent::TOOL_TYPE_STYLUS) {
+    // A stylus points to a direction specified by orientation and tilts to
+    // the opposite direction. Coordinate system is left-handed.
+    float tilt_rad = event.GetTilt(pointer_index);
+    float r = sin(tilt_rad);
+    float z = cos(tilt_rad);
+    touch.tiltX = lround(atan2(sin(-orientation_rad) * r, z) * 180.f / M_PI);
+    touch.tiltY = lround(atan2(cos(-orientation_rad) * r, z) * 180.f / M_PI);
+  } else {
+    touch.tiltX = touch.tiltY = 0;
+  }
+
   return touch;
 }
 
 }  // namespace
 
 blink::WebTouchEvent CreateWebTouchEventFromMotionEvent(
     const MotionEvent& event,
     bool may_cause_scrolling) {
   static_assert(static_cast<int>(MotionEvent::MAX_TOUCH_POINT_COUNT) ==
                     static_cast<int>(blink::WebTouchEvent::touchesLengthCap),
@@ skipping 161 matching lines @@
 }
 
 WebGestureEvent CreateWebGestureEventFromGestureEventData(
     const GestureEventData& data) {
   return CreateWebGestureEvent(data.details, data.time - base::TimeTicks(),
                                gfx::PointF(data.x, data.y),
                                gfx::PointF(data.raw_x, data.raw_y), data.flags);
 }
 
 }  // namespace ui