1 /*

     2 * Copyright (c) 2006-2007 Nokia Corporation and/or its subsidiary(-ies). 

     3 * All rights reserved.

     4 * This component and the accompanying materials are made available

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

     6 * which accompanies this distribution, and is available

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

     8 *

     9 * Initial Contributors:

    10 * Nokia Corporation - initial contribution.

    11 *

    12 * Contributors:

    13 *

    14 * Description:  THuiInteractionInterval is a utility class that can be used 

    15 *                as specify intervals that adapt to user input.

    16 *

    17 */

    18  

    19 

    20 #ifndef __FSINTERACTIONINTERVAL_H__

    21 #define __FSINTERACTIONINTERVAL_H__

    22 

    23 

    24 #include <e32base.h>

    25 

    26 /**

    27  * THuiInteractionInterval is a utility class that can be used to determine

    28  * the correct animation interval time, while taking into account how much time has

    29  * elapsed since the last time the interval was determined. 

    30  *

    31  * An interaction interval is useful for example when animating a list selector. By default,

    32  * the time interval for moving between two items could be 500 ms, but if

    33  * the user moves faster than this, the selector's animation may be 

    34  * unnecessarily delayed. In this situation, the interaction interval would

    35  * shorten the time interval for the moving animation, if necessary, to keep

    36  * better in sync with how quickly the user is moving in the list.

    37  */

    38 class CFsInteractionInterval: public CBase 

    39     {

    40 public:

    41 

    42     /* Constructors and destructor. */

    43 

    44     /**

    45      * Initializes the interaction interval.

    46      *

    47      * @param aScalar  Determines how strongly the interval adapts. 

    48      *

    49      * @see SetScalar()

    50      */

    51     CFsInteractionInterval(TReal32 aScalar = 2.0f);

    52 

    53 

    54     /* Methods. */

    55 

    56     /**

    57      * Sets the adaptation scalar. Determines how strongly the interval

    58      * will adapt to the elapsed time since the last evaluation.

    59      *

    60      * For example, 1.0 would mean that the maximum interval time is the 

    61      * time elapsed between the current evaluation and the

    62      * previous one. In this case, when the animation frequency 

    63      * stays the same, each sequence would have time to complete

    64      * before the next sequence begins. When the scalar is 2.0, the

    65      * maximum is twice the elapsed time, meaning that the 

    66      * ongoing animation sequence would always be finished halfway 

    67      * when the next sequence begins. This produces a smoother

    68      * end result.

    69      *

    70      * @param aScalar  New adaptation scalar.

    71      */

    72      void SetScalar(TReal32 aScalar);

    73     

    74     /**

    75      * Returns the current adapation scalar.

    76      *

    77      * @return Adaptation scalar.

    78      */

    79      TReal32 Scalar() const;

    80 

    81     /**

    82      * Evaluates the current interval. The evaluated interval will always 

    83      * be at least as large as the elapsed time since the last evaluation, 

    84      * but at most <code>aIntervalTime</code>. 

    85      *

    86      * @param aIntervalTime  The requested normal interval time.

    87      *

    88      * @return  The evaluated interval, effective during the current frame.

    89      *

    90      * @see SetScalar()

    91      */

    92      TInt Interval(TInt aIntervalTime);

    93     

    94     

    95 private:

    96 

    97     TTime iLastTime;

    98     

    99     /** Interval scalar. */

   100     TReal32 iScalar;

   101     

   102     /** Last time interaction interval was determined. */

   103     TUint32 iLastTimeMs;

   104 

   105     };

   106 

   107 

   108 #endif  // __FSINTERACTIONINTERVAL_H__