/*

* Copyright (c) 2006-2009 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description:

*

*/

/**

 @file

 @publishedPartner

 @released

*/

#ifndef MAUDIOGAINCONTROLOBSERVER_H

#define MAUDIOGAINCONTROLOBSERVER_H

#include <e32base.h>

#include <a3f/a3fbase.h>

#include <a3f/maudiogaincontrol.h>

/**

 *  An interface to a set of AudioGainControl callback functions.

 *

 *  this serves as the method of communication between the client and the

 *  AudioGainControl.

 *

 *  The class is a mixin and is intended to be inherited by the client class

 *  that is interested in observing the Gain operations. The functions

 *  encapsulated by this class are called when specific events occur while

 *  processing audio.

 *

 */

class MAudioGainControlObserver

	{

public:

	/**

	* Notifies the observer that the max ramp time supported by the gain

	* control has changed.

	*

	* @param aGain a reference to GainControl whose max ramp time changed.

	*/

	virtual void MaxRampTimeChanged(MAudioGainControl& aGain)=0;

	/**

	* Notifies the observer that the maximum gain value supported by the

	* gain control has changed.

	*

	* @param aGain a reference to GainControl whose max gain changed.

	*/

	virtual void MaxGainChanged(MAudioGainControl& aGain)=0;

	/**

	* Notifies the observer that the gain has changed, 

	* due to request from the client or otherwise.  

	* If gain change by the client cannot be fulfilled, 

	* a gain change with an error code other than KErrNone will be issued.

	* @param aGain	a reference to the gain control whose gain has changed.

	* @return aError		an error code. 

	* KErrNone if the gain change was requested by the client and was completed successfully.

	* KErrNotSupported if the SetGain() call referred to non-existent channels.

	* KErrArgument if aGain of less than 0 or larger than max gain, 

	* the same channel is specified multiple times, 

	* or aRampDuration is less than 0 or greater than max ramp duration.

	* KErrA3fUnsupportedRamp if the ramp operation requested is not supported, 

	* or the Uid value supplies is unknown.

	* Other system-wide errors are also possible. They will indicate that the gain change failed.

	* Note that these errors could alternatively be returned by the associated SetGain() call.

	*/

	virtual void GainChanged(MAudioGainControl& aGain, TInt aError)=0;

	};

#endif // MAUDIOGAINCONTROLOBSERVER_H