content/renderer/device_orientation/device_sensor_event_pump.h

   1 // Copyright 2013 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_RENDERER_DEVICE_SENSOR_EVENT_PUMP_H_
   6 #define CONTENT_RENDERER_DEVICE_SENSOR_EVENT_PUMP_H_
   7
   8 #include "base/memory/shared_memory.h"
   9 #include "base/timer/timer.h"
  10 #include "content/public/renderer/render_process_observer.h"
  11
  12 namespace content {
  13 class RenderThread;
  14
  15 class CONTENT_EXPORT DeviceSensorEventPump : public RenderProcessObserver {
  16  public:
  17   // Default delay between subsequent firing of events.
  18   static const int kDefaultPumpDelayMillis;
  19
  20   int GetDelayMillis() const;
  21
  22   void Attach(RenderThread* thread);
  23   virtual bool OnControlMessageReceived(const IPC::Message& message) = 0;
  24
  25  protected:
  26   // Constructor for a pump with default delay.
  27   DeviceSensorEventPump();
  28
  29   // Constructor for a pump with a given delay.
  30   explicit DeviceSensorEventPump(int pump_delay_millis);
  31   virtual ~DeviceSensorEventPump();
  32
  33   // The pump is a tri-state automaton with allowed transitions as follows:
  34   // STOPPED -> PENDING_START
  35   // PENDING_START -> RUNNING
  36   // PENDING_START -> STOPPED
  37   // RUNNING -> STOPPED
  38   enum PumpState {
  39       STOPPED,
  40       RUNNING,
  41       PENDING_START
  42   };
  43
  44   bool RequestStart();
  45   void OnDidStart(base::SharedMemoryHandle handle);
  46   bool Stop();
  47
  48   virtual void FireEvent() = 0;
  49   virtual bool InitializeReader(base::SharedMemoryHandle handle) = 0;
  50   virtual bool SendStartMessage() = 0;
  51   virtual bool SendStopMessage() = 0;
  52
  53   int pump_delay_millis_;
  54   PumpState state_;
  55   base::RepeatingTimer<DeviceSensorEventPump> timer_;
  56 };
  57
  58 }  // namespace content
  59
  60 #endif  // CONTENT_RENDERER_DEVICE_SENSOR_EVENT_PUMP_H_