/*

 * 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 MAUDIOCONTEXTOBSERVER_H

 #define MAUDIOCONTEXTOBSERVER_H

 #include <a3f/a3fbase.h>

 const TUid KUidA3FContextCommitUpdate		= {0x1028343E};

 const TUid KUidA3FContextPreEmptedCommit	= {0x1028343F};

 const TUid KUidA3FContextPreEmption			= {0x10283440};

 const TUid KUidA3FContextPreEmptionUpdate	= {0x10283441};

 const TUid KUidA3FContextUpdateComplete		= {0x10283442};

 const TUid KUidA3FContextAbort				= {0x10283443};

 /**

  * KUidA3FContextCommitUpdate - Follows a Commit() call. Signals that Commit() has been successfully received by MMRC 

  * and that update callbacks are about to follow.  Note will still be called if MMRC rejects the request for policy reasons 

  * – in which case, the callbacks will show the original value. 

  *if aError is not KErrNone, then the implementation tried to apply the change but this failed 

  * so that the implementation is “rolled-back” to the previous. However, KErrAbort says that this roll-back failed, 

  * and streams have been placed in a Dead state.

  *

  * KUidA3FContextPreEmptedCommit -  Follows a Commit() call, but signals that that MMRC is doing a simultaneous pre-emption. 

  * Update callbacks are about to follow, but these relate to the pre-emption. The original request is lost.

  * An error of KErrAbort says that the change MMRC requested failed, and typically streams are placed in a “Dead” mode.

  *

  * KUidA3FContextPreEmption -  Initial indication to the client that it is to be pre-empted. 

  * The client should treat the Context and its Components as “locked” – see below. 

  *

  * KUidA3FContextPreEmptionUpdate - Will follow a KUidA3FContextPreEmption and indicates that callbacks 

  * are about to start to indicate the update. An error of KErrAbort says that the change MMRC requested failed, 

  * and typically streams are placed in a “Dead” mode.

  * 

  * KUidA3FContextUpdateComplete - Signals that all callbacks are complete – Commit() can be called again, if required.

  *

  * KUidA3FContextAbort - Error occurred due to the commit or pre-emption cycle itself – 

  * that is something to do with the associated message passing mechanism etc. 

  * this terminates the whole cycle, whatever the current state. It should leave the context in a “reasonable state” 

  *– usually the original state.  aError gives the associated reason for this.

  */

 /*

  * Following Commit() or ContextEvent(KUidA3FContextPreEmption), the associated Context should be considered “locked” 

  * until the receipt of events KUidA3FContextCommitUpdate, KUidA3FContextPreEmptedCommit or KUidA3FContextPreEmptionUpdate. 

  * By locked it is meant that no changes shall be requested by the Client from the Context nor its associated Components, 

  * nor Commit() called.

  *

  * Following events KUidA3FContextCommitUpdate, KUidA3FContextPreEmptedCommit or KUidA3FContextPreEmptionUpdate, 

  * the Client can be requested changes to the Context and associated Components, but Commit() cannot be called.

  * 

  * Following event KUidA3FContextUpdateComplete Commit() can be called.

  *

  * Following the receipt of event KUidA3FContextPreEmptedCommit or KUidA3FPreEmptionUpdate, 

  * any pending requested changes to the Context or its Components are lost – there is an implied call to MAudioContext::Reset(). 

  */

 /**

  * Defines the interface for observing context states.

  */

 class MAudioContextObserver

 	{

 public:

 	/**

 	 * Callback to context observer to show progression through Commit() and pre-emption cycles.

 	 *

 	 * @param a Uid giving the specific event.

 	 * @param  an error code. KErrNone if successful, otherwise one of the system wide error codes.

 	*/

 	virtual void ContextEvent(TUid aEvent, TInt aError)=0;

 	};

 #endif // MAUDIOCONTEXTOBSERVER_H