Refactors DeviceOrientation to make it more extensible

content/browser/device_orientation/accelerometer_mac.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/device_orientation/accelerometer_mac.h"
 
 #include <math.h>
 
 #include "base/logging.h"
 #include "content/browser/device_orientation/orientation.h"
 #include "third_party/sudden_motion_sensor/sudden_motion_sensor_mac.h"
 
 namespace device_orientation {
 
 // Create a AccelerometerMac object and return NULL if no valid sensor found.
 DataFetcher* AccelerometerMac::Create() {
   scoped_ptr<AccelerometerMac> accelerometer(new AccelerometerMac);
   return accelerometer->Init() ? accelerometer.release() : NULL;
 }
 
 AccelerometerMac::~AccelerometerMac() {
 }
 
 AccelerometerMac::AccelerometerMac() {
 }
 
+const DeviceData* AccelerometerMac::GetDeviceData(DeviceData::Type type) {
+  if (type != DeviceData::kTypeOrientation)
+    return NULL;
+  return GetOrientation();
+}
+
 //  Retrieve per-axis orientation values.
 //
 //  Axes and angles are defined according to the W3C DeviceOrientation Draft.
 //  See here: http://dev.w3.org/geo/api/spec-source-orientation.html
 //
 //  Note: only beta and gamma angles are provided. Alpha is set to zero.
 //
 //  Returns false in case of error.
 //
-bool AccelerometerMac::GetOrientation(Orientation* orientation) {
+const Orientation* AccelerometerMac::GetOrientation() {
   DCHECK(sudden_motion_sensor_.get());
 
   // Retrieve per-axis calibrated values.
   float axis_value[3];
   if (!sudden_motion_sensor_->ReadSensorValues(axis_value))
-    return false;
+    return NULL;
 
   // Transform the accelerometer values to W3C draft angles.
   //
   // Accelerometer values are just dot products of the sensor axes
   // by the gravity vector 'g' with the result for the z axis inverted.
   //
   // To understand this transformation calculate the 3rd row of the z-x-y
   // Euler angles rotation matrix (because of the 'g' vector, only 3rd row
   // affects to the result). Note that z-x-y matrix means R = Ry * Rx * Rz.
   // Then, assume alpha = 0 and you get this:
   //
   // x_acc = sin(gamma)
   // y_acc = - cos(gamma) * sin(beta)
   // z_acc = cos(beta) * cos(gamma)
   //
   // After that the rest is just a bit of trigonometry.
   //
   // Also note that alpha can't be provided but it's assumed to be always zero.
   // This is necessary in order to provide enough information to solve
   // the equations.
   //
   const double kRad2deg = 180.0 / M_PI;
 
+  scoped_refptr<Orientation> orientation(new Orientation());
+
   orientation->set_beta(kRad2deg * atan2(-axis_value[1], axis_value[2]));
   orientation->set_gamma(kRad2deg * asin(axis_value[0]));
   // TODO(aousterh): should absolute_ be set to false here?
   // See crbug.com/136010.
 
   // Make sure that the interval boundaries comply with the specification. At
   // this point, beta is [-180, 180] and gamma is [-90, 90], but the spec has
   // the upper bound open on both.
   if (orientation->beta() == 180.0) {
     orientation->set_beta(-180.0);  // -180 == 180 (upside-down)
   }
   if (orientation->gamma() == 90.0) {
     static double just_less_than_90 = nextafter(90, 0);
     orientation->set_gamma(just_less_than_90);
   }
 
   // At this point, DCHECKing is paranoia. Never hurts.
   DCHECK_GE(orientation->beta(), -180.0);
   DCHECK_LT(orientation->beta(),  180.0);
   DCHECK_GE(orientation->gamma(), -90.0);
   DCHECK_LT(orientation->gamma(),  90.0);
 
-  return true;
+  return orientation;
 }
 
 bool AccelerometerMac::Init() {
   sudden_motion_sensor_.reset(SuddenMotionSensor::Create());
   return sudden_motion_sensor_.get() != NULL;
 }
 
 }  // namespace device_orientation