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diff --git a/kmix/mixer_backend.h b/kmix/mixer_backend.h
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+++ b/kmix/mixer_backend.h
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+//-*-C++-*-
+/*
+ * KMix -- KDE's full featured mini mixer
+ *
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this program; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ */
+
+#ifndef MIXER_BACKEND_H
+#define MIXER_BACKEND_H
+
+#include "mixer.h"
+
+class Mixer_Backend
+{
+// The Mixer Backend's may only be accessed from the Mixer class.
+friend class Mixer;
+
+protected:
+  Mixer_Backend(int devnum);
+  virtual ~Mixer_Backend();
+
+  /// Derived classes MUST implement this to open the mixer. Returns a KMix error code (O=OK).
+  virtual int open() = 0;
+  virtual int close() = 0;
+
+  /** Returns, whether this Mixer object contains a valid Mixer. You should return "false", when
+   * the Mixer with the devnum given in the constructor is not supported by the Backend. The two
+   * typical cases are:
+   * (1) No such hardware installed
+   * (2) The hardware exists, but has no mixer support (e.g. external soundcard with only mechanical volume knobs)
+   * The default implementation calls open(), checks the return code and whether the number of
+   * supported channels is > 0. Then it calls close().
+   * You should reimplement this method in your backend, when there is a less time-consuming method than
+   * calling open() and close() for checking the existance of a Mixer.
+   */
+  virtual bool isValid();
+
+  /** @return true, if the Mixer is open (and thus can be operated) */
+  bool isOpen();
+
+  virtual bool prepareUpdateFromHW();
+
+  /// Volume Read
+  virtual int readVolumeFromHW( int devnum, Volume &vol ) = 0;
+  /// Volume Write
+  virtual int writeVolumeToHW( int devnum, Volume &volume ) = 0;
+
+  /// Enums
+  virtual void setEnumIdHW(int mixerIdx, unsigned int);
+  virtual unsigned int enumIdHW(int mixerIdx);
+
+  /// Recording Switches
+  virtual bool setRecsrcHW( int devnum, bool on) = 0;
+  virtual bool isRecsrcHW( int devnum ) = 0;
+
+  /// Overwrite in the backend if the backend can see changes without polling
+  virtual bool needsPolling() { return true; }
+
+  /** overwrite this if you need to connect to slots in the mixer (e.g. readSetFromHW)
+      this called in the very beginning and only if !needsPolling
+  */
+  virtual void prepareSignalling( Mixer * ) {}
+
+  MixDevice* recommendedMaster();
+
+  /** Return a translated error text for the given error number.
+   * Subclasses can override this method to produce platform
+   * specific error descriptions.
+   */
+  virtual QString errorText(int mixer_error);
+  /// Prints out a translated error text for the given error number on stderr
+  void errormsg(int mixer_error);
+
+
+  int m_devnum;
+  /// User friendly name of the Mixer (e.g. "IRIX Audio Mixer"). If your mixer API
+  /// gives you a usable name, use that name.
+  QString m_mixerName;
+  // All mix devices of this phyisical device.
+  MixSet m_mixDevices;
+
+  /******************************************************************************************
+   * Please don't access the next vars from the Mixer class (even though Mixer is a friend).
+   * There are proper accesor methods for them.
+   ******************************************************************************************/
+  bool m_isOpen;
+  // The MixDevice that would qualify best as MasterDevice (according to the taste of the Backend developer)
+  MixDevice* m_recommendedMaster;
+};
+
+#endif