/*

* Copyright (c) 2006 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:  Triangle filler.

*

*/

//  Include Files

#include <e32std.h>

#include "TMIDTriangleFiller.h"

//  LOCAL CONSTANTS AND MACROS

//  LOCAL FUNCTIONS

void TMIDTriangleFiller::Construct(TInt aX1, TInt aY1,

                                   TInt aX2, TInt aY2,

                                   TInt aX3, TInt aY3)

{

    iX1 = aX1 << KShift;

    iY1 = aY1 << KShift;

    iX2 = aX2 << KShift;

    iY2 = aY2 << KShift;

    iX3 = aX3 << KShift;

    iY3 = aY3 << KShift;

    if (iY1 > iY2)

    {

        // Swap P1 and P2

        SwapPoints(iX1, iY1, iX2, iY2);

    }

    if (iY2 > iY3)

    {

        // Swap P2 and P3

        SwapPoints(iX2, iY2, iX3, iY3);

    }

    if (iY1 > iY2)

    {

        // Swap P1 and P2

        SwapPoints(iX1, iY1, iX2, iY2);

    }

    iNormalCase = EFalse;

    if (iY1 == iY2)

    {

        if (iY2 == iY3)

        {

            ConstructSingleLine();

        }

        else

        {

            ConstructSpecialCaseOne();

        }

    }

    else if (iY2 == iY3)

    {

        ConstructSpecialCaseTwo();

    }

    else

    {

        ConstructNormalCase();

    }

    iY1 = iY1 >> KShift;

}

void TMIDTriangleFiller::SecondHalf()

{

    if (iLeftDelta == iDx13)

    {

        iRightDelta = iDx23;

    }

    else

    {

        iLeftDelta = iDx23;

    }

    iScanlines = (iY3 - iY2) >> KShift;

    iNormalCase = EFalse;

}

void TMIDTriangleFiller::ConstructNormalCase()

{

    // The normal case:

    //      1

    //     /|

    //    / |    first half

    //   /  |                 dx12 < dx13

    // 2/___|____

    //  \_  |

    //    \_|    second half

    //      3

    // Calculate step values for edges

    iNormalCase = ETrue;

    iDx12 = (FPDIV((iX2 - iX1), (iY2 - iY1)));

    iDx23 = (FPDIV((iX3 - iX2), (iY3 - iY2)));

    iDx13 = (FPDIV((iX3 - iX1), (iY3 - iY1)));

    // Check which edge (13 or 12) is the left side edge

    if (iDx12 < iDx13)

    {

        iLeftDelta = iDx12;

        iRightDelta = iDx13;

    }

    else

    {

        iLeftDelta = iDx13;

        iRightDelta = iDx12;

    }

    // Initialize the span

    iSpanStart = iX1;

    iSpanStop = iX1;

    // Do the first half of the polygon ( 1-2 )

    iScanlines = (iY2 - iY1) >> KShift;

}

void TMIDTriangleFiller::ConstructSingleLine()

{

    iScanlines = 1;

    iSpanStart = Min(iX1, iX2);

    iSpanStart = Min(iSpanStart, iX3);

    iSpanStop = Max(iX1, iX2);

    iSpanStop = Max(iSpanStop, iX3);

}

void TMIDTriangleFiller::ConstructSpecialCaseOne()

{

    // Special case:

    //    1________2

    //     \      /

    //      \    /

    //       \  /

    //        \/

    //         3

    if (iX1 > iX2)

    {

        SwapPoints(iX1, iY1, iX2, iY2);

    }

    iDx13 = (FPDIV((iX3 - iX1), (iY3 - iY1)));

    iDx23 = (FPDIV((iX3 - iX2), (iY3 - iY2)));

    // check which edge is left edge

    if (iDx13 < iDx23)

    {

        iLeftDelta = iDx23;

        iRightDelta = iDx13;

    }

    else

    {

        iLeftDelta = iDx13;

        iRightDelta = iDx23;

    }

    // initialize span

    iSpanStart = iX1;

    iSpanStop = iX2;

    iScanlines = (iY3 - iY1) >> KShift;

}

void TMIDTriangleFiller::ConstructSpecialCaseTwo()

{

    /*

    // Special case:

    //     1

    //    /\

    //   /  \

    //  /    \

    // /      \

    //2--------3

    */

    // calculate slopes

    iDx12 = (FPDIV((iX2 - iX1), (iY2 - iY1)));

    iDx13 = (FPDIV((iX3 - iX1), (iY3 - iY1)));

    // check which edge is left edge

    if (iDx12 < iDx13)

    {

        iLeftDelta = iDx12;

        iRightDelta = iDx13;

    }

    else

    {

        iLeftDelta = iDx13;

        iRightDelta = iDx12;

    }

    // Initialize the span

    iSpanStart = iX1;// + iLeftDelta;

    iSpanStop = iX1;// + iRightDelta;

    iScanlines = (iY2 - iY1) >> KShift;

}

void TMIDTriangleFiller::GetNextPixelRun(TBool& aExists, TInt& aScanLine,

        TInt& aStart, TInt& aEnd)

{

    aScanLine = iY1++;

    aStart = (iSpanStart >> KShift) + 1;

    aEnd = iSpanStop >> KShift;

    iSpanStart += iLeftDelta;

    iSpanStop += iRightDelta;

    aExists = ETrue;

    if (--iScanlines < 1)

    {

        if (iNormalCase)

        {

            SecondHalf();

        }

        else

        {

            aExists = EFalse;

        }

    }

}

//  End of File