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 

    21 #ifndef __HUIINTERACTIONINTERVAL_H__

    22 #define __HUIINTERACTIONINTERVAL_H__

    23 

    24 

    25 #include <e32base.h>

    26 

    27 

    28 /**

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

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

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

    32  *

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

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

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

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

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

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

    39  */

    40 class THuiInteractionInterval 

    41     {

    42 public:

    43 

    44     /* Constructors and destructor. */

    45 

    46     /**

    47      * Initializes the interaction interval.

    48      *

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

    50      *

    51      * @see SetScalar()

    52      */

    53     IMPORT_C THuiInteractionInterval(TReal32 aScalar = 2.0f) __SOFTFP;

    54 

    55 

    56     /* Methods. */

    57 

    58     /**

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

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

    61      *

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

    63      * time elapsed between the current evaluation and the

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

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

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

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

    68      * ongoing animation sequence would always be finished halfway 

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

    70      * end result.

    71      *

    72      * @param aScalar  New adaptation scalar.

    73      */

    74     IMPORT_C void SetScalar(TReal32 aScalar) __SOFTFP;

    75     

    76     /**

    77      * Returns the current adapation scalar.

    78      *

    79      * @return Adaptation scalar.

    80      */

    81     IMPORT_C TReal32 Scalar() const __SOFTFP;

    82 

    83     /**

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

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

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

    87      *

    88      * @param aIntervalTime  The requested normal interval time.

    89      *

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

    91      *

    92      * @see SetScalar()

    93      */

    94     IMPORT_C TInt Interval(TInt aIntervalTime);

    95     

    96     

    97 private:

    98 

    99     /** Interval scalar. */

   100     TReal32 iScalar;

   101     

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

   103     TUint32 iLastTimeMs;

   104 

   105     };

   106 

   107 

   108 #endif  // __HUIINTERACTIONINTERVAL_H__