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diff --git a/juk/playlistinterface.h b/juk/playlistinterface.h
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+/***************************************************************************
+    copyright            : (C) 2004 by Scott Wheeler
+    email                : wheeler@kde.org
+***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef PLAYLISTINTERFACE_H
+#define PLAYLISTINTERFACE_H
+
+#include "filehandle.h"
+
+
+class PlaylistObserver;
+
+/**
+ * An interface implemented by PlaylistInterface to make it possible to watch
+ * for changes in the PlaylistInterface.  This is a semi-standard observer
+ * pattern from i.e. Design Patterns.
+ */
+
+class Watched
+{
+public:
+    void addObserver(PlaylistObserver *observer);
+    void removeObserver(PlaylistObserver *observer);
+
+    /**
+     * This is triggered when the currently playing item has been changed.
+     */
+    virtual void currentChanged();
+
+    /**
+     * This is triggered when the data in the playlist -- i.e. the tag content
+     * changes.
+     */
+    virtual void dataChanged();
+
+protected:
+    virtual ~Watched();
+
+private:
+    QValueList<PlaylistObserver *> m_observers;
+};
+
+/**
+ * This is a simple interface that should be used by things that implement a
+ * playlist-like API.
+ */
+
+class PlaylistInterface : public Watched
+{
+public:
+    virtual QString name() const = 0;
+    virtual FileHandle currentFile() const = 0;
+    virtual int time() const = 0;
+    virtual int count() const = 0;
+
+    virtual void playNext() = 0;
+    virtual void playPrevious() = 0;
+    virtual void stop() = 0;
+
+    virtual bool playing() const = 0;
+};
+
+class PlaylistObserver
+{
+public:
+    virtual ~PlaylistObserver();
+
+    /**
+     * This method must be implemented in concrete implementations; it should
+     * define what action should be taken in the observer when the currently
+     * playing item changes.
+     */
+    virtual void updateCurrent() = 0;
+
+    /**
+     * This method must be implemented in concrete implementations; it should
+     * define what action should be taken when the data of the PlaylistItems in
+     * the playlist changes.
+     */
+    virtual void updateData() = 0;
+
+    void clearWatched() { m_playlist = 0; }
+
+protected:
+    PlaylistObserver(PlaylistInterface *playlist);
+    const PlaylistInterface *playlist() const;
+
+private:
+    PlaylistInterface *m_playlist;
+};
+
+#endif