xbmc/utils/Observer.h

   1 /*
   2  *  Copyright (C) 2005-2018 Team Kodi
   3  *  This file is part of Kodi - https://kodi.tv
   4  *
   5  *  SPDX-License-Identifier: GPL-2.0-or-later
   6  *  See LICENSES/README.md for more information.
   7  */
   8
   9 #pragma once
  10
  11 #include "threads/CriticalSection.h"
  12
  13 #include <atomic>
  14 #include <vector>
  15
  16 class Observable;
  17 class ObservableMessageJob;
  18
  19 typedef enum
  20 {
  21   ObservableMessageNone,
  22   ObservableMessagePeripheralsChanged,
  23   ObservableMessageSettingsChanged,
  24   ObservableMessageButtonMapsChanged,
  25   // Used for example when the subtitle alignment position change
  26   ObservableMessagePositionChanged,
  27   ObservableMessageGamePortsChanged,
  28   ObservableMessageGameAgentsChanged,
  29 } ObservableMessage;
  30
  31 class Observer
  32 {
  33 public:
  34   Observer() = default;
  35   virtual ~Observer() = default;
  36   /*!
  37    * @brief Process a message from an observable.
  38    * @param obs The observable that sends the message.
  39    * @param msg The message.
  40    */
  41   virtual void Notify(const Observable &obs, const ObservableMessage msg) = 0;
  42 };
  43
  44 class Observable
  45 {
  46   friend class ObservableMessageJob;
  47
  48 public:
  49   Observable() = default;
  50   virtual ~Observable() = default;
  51   virtual Observable &operator=(const Observable &observable);
  52
  53   /*!
  54    * @brief Register an observer.
  55    * @param obs The observer to register.
  56    */
  57   virtual void RegisterObserver(Observer *obs);
  58
  59   /*!
  60    * @brief Unregister an observer.
  61    * @param obs The observer to unregister.
  62    */
  63   virtual void UnregisterObserver(Observer *obs);
  64
  65   /*!
  66    * @brief Send a message to all observers when m_bObservableChanged is true.
  67    * @param message The message to send.
  68    */
  69   virtual void NotifyObservers(const ObservableMessage message = ObservableMessageNone);
  70
  71   /*!
  72    * @brief Mark an observable changed.
  73    * @param bSetTo True to mark the observable changed, false to mark it as unchanged.
  74    */
  75   virtual void SetChanged(bool bSetTo = true);
  76
  77   /*!
  78    * @brief Check whether this observable is being observed by an observer.
  79    * @param obs The observer to check.
  80    * @return True if this observable is being observed by the given observer, false otherwise.
  81    */
  82   virtual bool IsObserving(const Observer &obs) const;
  83
  84 protected:
  85   /*!
  86    * @brief Send a message to all observer when m_bObservableChanged is true.
  87    * @param obs The observer that sends the message.
  88    * @param message The message to send.
  89    */
  90   void SendMessage(const ObservableMessage message);
  91
  92   std::atomic<bool>       m_bObservableChanged{false}; /*!< true when the observable is marked as changed, false otherwise */
  93   std::vector<Observer *> m_observers;                 /*!< all observers */
  94   mutable CCriticalSection m_obsCritSection; /*!< mutex */
  95 };