/*

* Copyright (c) 2008 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:  interface for layout policy

*

*/

#ifndef I_ALFGRIDLAYOUTMANAGER

#define I_ALFGRIDLAYOUTMANAGER

#include <alf/ialfinterfacebase.h>

#include <alf/alftypes.h>

class CAlfLayout;

class CAlfControl;

namespace Alf

    {

class CAlfWidgetControl;

namespace ialfgridlayoutpolicy

    {

     static const IfId Ident =

        {

        0, "gridlayoutpolicy"

        };

    }

using Alf::CAlfWidgetControl;

/**

 * The interface for grid layout policy

 *

 * Provides grid specific layout APIs

 * 

 * @code

 * // Create layout manager interface.

 * IAlfLayoutManager* layoutManager = IAlfInterfaceBase::makeInterface<IAlfLayoutManager>(control);

 *

 * // See if layout policy is supported in the given layout manager.

 * IAlfGridLayoutPolicy* layoutPolicy = IAlfInterfaceBase::makeInterface<IAlfGridLayoutPolicy>(layoutManager);

 *

 * if(layoutPreferences != 0)

 *     {

 *     int rows = layoutPolicy->dimensionCount(EAlfGridDimensionRow);

 *     }

 * @endcode

 *

 * @lib alfwidgetmodel.lib

 * @since S60 ?S60_version

 * @status Draft

 */

class IAlfGridLayoutPolicy : public IAlfInterfaceBase

    {

public:

    static inline const IfId& type()

        {       

        return ialfgridlayoutpolicy::Ident;

        }

    virtual inline ~IAlfGridLayoutPolicy() {}

public:

    /* Each dimension corresponds to a different axis for the grid blocks */

    enum gridLayoutDimension

        {

        EGridDimensionColumn = 0,

        EGridDimensionRow

        };

public:

    /**

     * Sets the number and weights of blocks in this grid layout in the direction of the specified

     * dimension. Each block's weight will be set to equal the supplied value, the result

     * of which is that all blocks will be equally spaced, whatever the units. 

     *

     * @see appendWeight; for more information on how weights are used to calculate layout positions.

     *

     * @note This API could be useful if then subsequent calls to @c replaceWeight are made to 

     * change specific values, depending on how many of the values are different. 

     * @note Calling this with aCount set to 0 will clear all of the existing weights in the direction

     * of the specified dimension.

     * @note this is the same as using metrics with unit type EAlfUnitWeight.

     *

     * @param aDim the dimension along which to fill

     * @param aCount The number of lines of blocks to fill

     * @param aWeight the weights to be used for all blocks

     * @throw AlfVisualException

     */    

    virtual void fillWeights(gridLayoutDimension aDim, int aCount, const TAlfMetric& aWeight) = 0;

    /**

     * Add a new line of blocks to this grid layout at the last position in the direction of the 

     * specified dimension. It will have the supplied weight. Weights can be any metric value, 

     * hence different units can be used for each block. In particular, EAlfUnitWeight can be used 

     * to represent weight values in aribtrary proportional units.

     *

     * In the case of proportional weights, the effect of this will be to cause the other blocks to 

     * resize according to the new total weight.

     *

     * @note If non-relative coordinates are specified (e.g., real pixels), the combined blocks might not 

     *      fill the entire layout area. However, weights will always stretch to fill all available space 

     *      after the fixed units have been determined. Therefore, depending on circumstances it may

     *      be better to use EAlfUnitWeight

     * @note For example [2 weights, 1 weight, 2 weights] in a layout of 100 pixels would result 

     *      in [40 pixels, 20 pixels, 40 pixels]. 

     * @note For example [10 pixels, 1 weight, 15 pixels] in a layout of 100 pixels would result 

     *      in [10 pixels, 75 pixels, 15 pixels]. 

     *

     * @param aDim the dimension to which the weight corresponds

     * @param aWeight the weight to be used for the block in the specified dimension, 

     *          replacing any previously existing weight for that block

     * @throw AlfVisualException

     */

    virtual void appendWeight(gridLayoutDimension aDim, const TAlfMetric& aWeight) = 0;

    /**

     * Add a new line of blocks to this grid layout at the specified position in the direciton of 

     * the specified dimension. It will have the supplied weight. In the case of proportional 

     * weights, the effect of this will be to cause the other blocks to resize according to the new 

     * total weight. It will also mean that many child visuals will now occupy different blocks within

     * the grid according to how the blocks wrap.

     *

     * @note will leave if the specified position is greater than the number of objects currently in the array, 

     * so check first by calling @c preferredDimensionCount

     * @see appendWeight for more information on how weights are used to calculate layout positions.

     *

     * @param aDim the dimension to which the weight corresponds

     * @param aWeight the weight to be used for the block in the specified dimension, 

     *          replacing any previously existing weight for that block

     * @param aPos the index of the block

     * @throw AlfVisualException

     */

    virtual void insertWeight(gridLayoutDimension aDim, const TAlfMetric& aWeight, int aPos) = 0;

    /**

     * Sets the weight of a specific line of blocks in this grid layout, in the direction of the supplied dimension.

     * In the case of proportional weights, the effect of this will be to cause the 

     * other blocks to resize according to the new total weight. 

     *

     * @see appendWeight for more information on how weights are used to calculate layout positions.

     *

     * @param aDim the dimension to which the weight corresponds

     * @param aWeight the weight to be used for the block in the specified dimension, 

     *          replacing any previously existing weight for that cell

     * @param aPos the index of the cell

     * @throw AlfVisualException

     */

    virtual void replaceWeight(gridLayoutDimension aDim, const TAlfMetric& aWeight, int aPos) = 0;

    /**

     * Remove a line of blocks from this grid layout at the specified position in the 

     * specified dimension. In the case of proportional weights, the effect of this will 

     * be to cause the other blocks to resize according to the new total weight. It will also mean 

     * that many child visuals will now occupy different blocks within the grid according to how 

     * the blocks wrap.

     *

     * @see appendWeight for more information on how weights are used to calculate layout positions.

     *

     * @param aDim the dimension to which the weight corresponds

     * @param aPos the index of the cell

     * @throw AlfVisualException

     */

    virtual void removeWeight(gridLayoutDimension aDim, int aPos) = 0;

    /**

     * Returns the weight of a specific line of blocks in this grid layout, in the

     * specified dimension. 

     *

     * @see appendWeight for more information on how weights are used to calculate layout positions.

     *

     * @param aDim the dimension to which the weight corresponds

     * @param aPos the index of the cell

     * @return the weight being used for the cell in the specified dimension, will be 0 magnitude if not set

     * @throw AlfVisualException

     */

    virtual TAlfMetric weight(gridLayoutDimension aDim, int aPos) const = 0;

    /**

     * Return the number of lines of blocks in this grid, along the specified dimension

     *

     * @param aDim the dimension along which to count

     * @return The number of lines of blocks in this grid.

     */        

    virtual int count(gridLayoutDimension aDim) const = 0;

public:

// from base class IAlfInterfaceBase

    /**

     * Interface getter. 

     * @see IAlfInterfaceBase::MakeInterface

     *

     * @param aType The type id of the queried interface.

     * @return The queried interface, or NULL if the interface is not

     *         supported or available.

     */    

    virtual IAlfInterfaceBase* makeInterface( const IfId& aType ) = 0;

    };

    } // namespace Alf

#endif // I_ALFGRIDLAYOUTMANAGER