content/browser/device_orientation/provider.h

   1 // Copyright (c) 2012 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 CONTENT_BROWSER_DEVICE_ORIENTATION_PROVIDER_H_
   6 #define CONTENT_BROWSER_DEVICE_ORIENTATION_PROVIDER_H_
   7
   8 #include "base/memory/ref_counted.h"
   9 #include "content/browser/device_orientation/device_data.h"
  10 #include "content/common/content_export.h"
  11
  12 namespace content {
  13
  14 class CONTENT_EXPORT Provider : public base::RefCountedThreadSafe<Provider> {
  15  public:
  16   class Observer {
  17    public:
  18     // Called when device data changes.
  19     // An Observer must not synchronously call Provider::RemoveObserver
  20     // or Provider::AddObserver when this is called.
  21     virtual void OnDeviceDataUpdate(const DeviceData* device_data,
  22                                     DeviceData::Type device_data_type) = 0;
  23     DeviceData::Type device_data_type() { return device_data_type_; }
  24
  25    protected:
  26     Observer(DeviceData::Type device_data_type)
  27         : device_data_type_(device_data_type) {
  28     }
  29     virtual ~Observer() {}
  30
  31    private:
  32     // Each Observer observes exactly one type of DeviceData.
  33     DeviceData::Type device_data_type_;
  34   };
  35
  36   // Returns a pointer to the singleton instance of this class.
  37   // The caller should store the returned pointer in a scoped_refptr.
  38   // The Provider instance is lazily constructed when GetInstance() is called,
  39   // and destructed when the last scoped_refptr referring to it is destructed.
  40   static Provider* GetInstance();
  41
  42   // Inject a mock Provider for testing. Only a weak pointer to the injected
  43   // object will be held by Provider, i.e. it does not itself contribute to the
  44   // injected object's reference count.
  45   static void SetInstanceForTests(Provider* provider);
  46
  47   // Get the current instance. Used for testing.
  48   static Provider* GetInstanceForTests();
  49
  50   // Note: AddObserver may call back synchronously to the observer with data.
  51   virtual void AddObserver(Observer* observer) = 0;
  52   virtual void RemoveObserver(Observer* observer) = 0;
  53
  54  protected:
  55   Provider();
  56   virtual ~Provider();
  57
  58  private:
  59   friend class base::RefCountedThreadSafe<Provider>;
  60   static Provider* instance_;
  61
  62   DISALLOW_COPY_AND_ASSIGN(Provider);
  63 };
  64
  65 }  // namespace content
  66
  67 #endif  // CONTENT_BROWSER_DEVICE_ORIENTATION_PROVIDER_H_