Implement device_orientation::Provider.

chrome/browser/device_orientation/provider_impl.h

+// Copyright (c) 2010 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 CHROME_BROWSER_DEVICE_ORIENTATION_PROVIDER_IMPL_H_
+#define CHROME_BROWSER_DEVICE_ORIENTATION_PROVIDER_IMPL_H_
+
+#include <set>
+#include <vector>
+
+#include "base/scoped_ptr.h"
+#include "base/task.h"
+#include "chrome/browser/device_orientation/data_fetcher.h"
+#include "chrome/browser/device_orientation/orientation.h"
+#include "chrome/browser/device_orientation/provider.h"
+
+class MessageLoop;
+
+namespace base {
+class Thread;
+}
+
+namespace device_orientation {
+
+class ProviderImpl : public Provider {
+ public:
+  typedef DataFetcher* (*DataFetcherFactory)();
+
+  // Create a ProviderImpl that expects calls to AddObserver and RemoveObserver
+  // on message_loop, sends notifications to observers on message_loop,
+  // and uses the NULL-terminated factories array to find a DataFetcher
+  // that can provide orientation data.
+  ProviderImpl(MessageLoop* message_loop, const DataFetcherFactory factories[]);
+
+  // From Provider.
+  virtual void AddObserver(Observer* observer);
+  virtual void RemoveObserver(Observer* observer);
+
+ private:
+  virtual ~ProviderImpl();
+
+  // Starts or Stops the provider. Called from creator_loop_.
+  void Start();
+  void Stop();
+
+  // Method for finding a suitable DataFetcher and starting the polling.
+  // Runs on the polling_thread_.
+  void DoInitializePollingThread(std::vector<DataFetcherFactory> factories);
+  void ScheduleInitializePollingThread();
+
+  // Method for polling a DataFetcher. Runs on the polling_thread_.
+  void DoPoll();
+  void ScheduleDoPoll();
+
+  // Method for notifying observers of an orientation update.
+  // Runs on the creator_thread_.
+  void DoNotify(Orientation orientation);
+  void ScheduleDoNotify(Orientation orientation);
+
+  static bool SignificantlyDifferent(const Orientation& orientation1,
+                                     const Orientation& orientation2);
+
+  enum { kDesiredSamplingIntervalMs = 100 };
+  int SamplingIntervalMs() const;
+
+  // The Message Loop on which this object was created.
+  // Typically the I/O loop, but may be something else during testing.
+  MessageLoop* creator_loop_;
+
+  // Members below are only to be used from the creator_loop_.
+  std::vector<DataFetcherFactory> factories_;
+  std::set<Observer*> observers_;
+  Orientation last_notification_;
+
+  // When polling_thread_ is running, members below are only to be used
+  // from that thread.
+  scoped_ptr<DataFetcher> data_fetcher_;
+  Orientation last_orientation_;
+  ScopedRunnableMethodFactory<ProviderImpl> do_poll_method_factory_;
+
+  // Polling is done on this background thread.
+  scoped_ptr<base::Thread> polling_thread_;
+};
+
+}  // namespace device_orientation
+
+#endif  // CHROME_BROWSER_DEVICE_ORIENTATION_PROVIDER_IMPL_H_