1 files changed, 91 insertions, 0 deletions

diff --git a/xbmc/utils/Observer.h b/xbmc/utils/Observer.h
new file mode 100644
index 0000000..feb201a
--- /dev/null
+++ b/xbmc/utils/Observer.h
@@ -0,0 +1,91 @@
+/*
+ *  Copyright (C) 2005-2018 Team Kodi
+ *  This file is part of Kodi - https://kodi.tv
+ *
+ *  SPDX-License-Identifier: GPL-2.0-or-later
+ *  See LICENSES/README.md for more information.
+ */
+
+#pragma once
+
+#include "threads/CriticalSection.h"
+
+#include <atomic>
+#include <vector>
+
+class Observable;
+class ObservableMessageJob;
+
+typedef enum
+{
+  ObservableMessageNone,
+  ObservableMessagePeripheralsChanged,
+  ObservableMessageSettingsChanged,
+  ObservableMessageButtonMapsChanged,
+} ObservableMessage;
+
+class Observer
+{
+public:
+  Observer() = default;
+  virtual ~Observer() = default;
+  /*!
+   * @brief Process a message from an observable.
+   * @param obs The observable that sends the message.
+   * @param msg The message.
+   */
+  virtual void Notify(const Observable &obs, const ObservableMessage msg) = 0;
+};
+
+class Observable
+{
+  friend class ObservableMessageJob;
+
+public:
+  Observable() = default;
+  virtual ~Observable() = default;
+  virtual Observable &operator=(const Observable &observable);
+
+  /*!
+   * @brief Register an observer.
+   * @param obs The observer to register.
+   */
+  virtual void RegisterObserver(Observer *obs);
+
+  /*!
+   * @brief Unregister an observer.
+   * @param obs The observer to unregister.
+   */
+  virtual void UnregisterObserver(Observer *obs);
+
+  /*!
+   * @brief Send a message to all observers when m_bObservableChanged is true.
+   * @param message The message to send.
+   */
+  virtual void NotifyObservers(const ObservableMessage message = ObservableMessageNone);
+
+  /*!
+   * @brief Mark an observable changed.
+   * @param bSetTo True to mark the observable changed, false to mark it as unchanged.
+   */
+  virtual void SetChanged(bool bSetTo = true);
+
+  /*!
+   * @brief Check whether this observable is being observed by an observer.
+   * @param obs The observer to check.
+   * @return True if this observable is being observed by the given observer, false otherwise.
+   */
+  virtual bool IsObserving(const Observer &obs) const;
+
+protected:
+  /*!
+   * @brief Send a message to all observer when m_bObservableChanged is true.
+   * @param obs The observer that sends the message.
+   * @param message The message to send.
+   */
+  void SendMessage(const ObservableMessage message);
+
+  std::atomic<bool>       m_bObservableChanged{false}; /*!< true when the observable is marked as changed, false otherwise */
+  std::vector<Observer *> m_observers;                 /*!< all observers */
+  mutable CCriticalSection m_obsCritSection; /*!< mutex */
+};