chromeos/accelerometer/accelerometer_reader.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
   6 #define CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_
   7
   8 #include "base/memory/ref_counted.h"
   9 #include "base/memory/weak_ptr.h"
  10 #include "base/observer_list.h"
  11 #include "chromeos/chromeos_export.h"
  12 #include "ui/accelerometer/accelerometer_types.h"
  13
  14 template <typename T>
  15 struct DefaultSingletonTraits;
  16
  17 namespace base {
  18 class TaskRunner;
  19 }
  20
  21 namespace chromeos {
  22
  23 // Reads an accelerometer device and reports data back to an
  24 // AccelerometerDelegate.
  25 class CHROMEOS_EXPORT AccelerometerReader {
  26  public:
  27   // Configuration structure for accelerometer device.
  28   struct ConfigurationData {
  29     ConfigurationData();
  30     ~ConfigurationData();
  31
  32     // Number of accelerometers on device.
  33     size_t count;
  34
  35     // Length of accelerometer updates.
  36     size_t length;
  37
  38     // Which accelerometers are present on device.
  39     bool has[ui::ACCELEROMETER_SOURCE_COUNT];
  40
  41     // Scale of accelerometers (i.e. raw value * scale = m/s^2).
  42     float scale[ui::ACCELEROMETER_SOURCE_COUNT][3];
  43
  44     // Index of each accelerometer axis in data stream.
  45     int index[ui::ACCELEROMETER_SOURCE_COUNT][3];
  46   };
  47   typedef base::RefCountedData<ConfigurationData> Configuration;
  48   typedef base::RefCountedData<char[12]> Reading;
  49
  50   // An interface to receive data from the AccelerometerReader.
  51   class Observer {
  52    public:
  53     virtual void OnAccelerometerUpdated(
  54         const ui::AccelerometerUpdate& update) = 0;
  55
  56    protected:
  57     virtual ~Observer() {}
  58   };
  59
  60   static AccelerometerReader* GetInstance();
  61
  62   void Initialize(scoped_refptr<base::TaskRunner> blocking_task_runner);
  63
  64   // Add/Remove observers.
  65   void AddObserver(Observer* observer);
  66   void RemoveObserver(Observer* observer);
  67
  68   // A reading is considered stable if its deviation from gravity is small. This
  69   // returns false if the deviation is too higher, or if |source| is not present
  70   // in the update.
  71   static bool IsReadingStable(const ui::AccelerometerUpdate& update,
  72                               ui::AccelerometerSource source);
  73
  74  protected:
  75   AccelerometerReader();
  76   virtual ~AccelerometerReader();
  77
  78  private:
  79   friend struct DefaultSingletonTraits<AccelerometerReader>;
  80
  81   // Dispatched when initialization is complete. If |success|, |configuration|
  82   // provides the details of the detected accelerometer.
  83   void OnInitialized(scoped_refptr<Configuration> configuration, bool success);
  84
  85   // Triggers an asynchronous read from the accelerometer, signalling
  86   // OnDataRead with the result.
  87   void TriggerRead();
  88
  89   // If |success|, converts the raw reading to an AccelerometerUpdate
  90   // message and notifies the |delegate_| with the new readings.
  91   // Triggers another read from the accelerometer at the current sampling rate.
  92   void OnDataRead(scoped_refptr<Reading> reading, bool success);
  93
  94   // The task runner to use for blocking tasks.
  95   scoped_refptr<base::TaskRunner> task_runner_;
  96
  97   // The last seen accelerometer data.
  98   ui::AccelerometerUpdate update_;
  99
 100   // The accelerometer configuration.
 101   scoped_refptr<Configuration> configuration_;
 102
 103   ObserverList<Observer, true> observers_;
 104
 105   base::WeakPtrFactory<AccelerometerReader> weak_factory_;
 106
 107   DISALLOW_COPY_AND_ASSIGN(AccelerometerReader);
 108 };
 109
 110 }  // namespace chromeos
 111
 112 #endif  // CHROMEOS_ACCELEROMETER_ACCELEROMETER_READER_H_