/******************************Module*Header*******************************\
* Module Name: fastfill.c
*
* Fills solid-coloured, unclipped, non-complex rectangles.
*
* Copyright (c) 1993-1994 Microsoft Corporation
\**************************************************************************/

#include "precomp.h"

#define RIGHT 0
#define LEFT  1
#define SWAP(a, b, tmp) { tmp = a; a = b; b = tmp; }

typedef struct _EDGEDATA {
LONG      x;                // Current x position
LONG      dx;               // # pixels to advance x on each scan
LONG      lError;           // Current DDA error
LONG      lErrorUp;         // DDA error increment on each scan
LONG      lErrorDown;       // DDA error adjustment
POINTFIX* pptfx;            // Points to start of current edge
LONG      dptfx;            // Delta (in bytes) from pptfx to next point
LONG      cy;               // Number of scans to go for this edge
} EDGEDATA;                         /* ed, ped */

/******************************Public*Routine******************************\
* bFastFill
*
* Draws a non-complex, unclipped polygon.
*
* Returns TRUE if the polygon was drawn; FALSE if the polygon was complex.
*
\**************************************************************************/

BOOL bFastFill(
PPDEV     ppdev,
LONG      cEdges,           // Includes close figure edge
POINTFIX* pptfxFirst,
ULONG     ulHwMix,
ULONG     iSolidColor)
{
    LONG      yTrapezoid;   // Top scan for next trapezoid
    LONG      cyTrapezoid;  // Number of scans in current trapezoid
    LONG      yStart;       // y-position of start point in current edge
    LONG      dM;           // Edge delta in FIX units in x direction
    LONG      dN;           // Edge delta in FIX units in y direction
    LONG      i;
    POINTFIX* pptfxLast;    // Points to the last point in the polygon array
    POINTFIX* pptfxTop;     // Points to the top-most point in the polygon
    POINTFIX* pptfxOld;     // Start point in current edge
    POINTFIX* pptfxScan;    // Current edge pointer for finding pptfxTop
    LONG      cScanEdges;   // Number of edges scanned to find pptfxTop
                            //  (doesn't include the closefigure edge)
    LONG      iEdge;
    LONG      lQuotient;
    LONG      lRemainder;

    EDGEDATA  aed[2];       // DDA terms and stuff
    EDGEDATA* ped;

    pptfxScan = pptfxFirst;
    pptfxTop  = pptfxFirst;                 // Assume for now that the first
                                            //  point in path is the topmost
    pptfxLast = pptfxFirst + cEdges - 1;

    // 'pptfxScan' will always point to the first point in the current
    // edge, and 'cScanEdges' will the number of edges remaining, including
    // the current one:

    cScanEdges = cEdges - 1;     // The number of edges, not counting close figure

    if ((pptfxScan + 1)->y > pptfxScan->y)
    {
        // Collect all downs:

        do {
            if (--cScanEdges == 0)
                goto SetUpForFilling;
            pptfxScan++;
        } while ((pptfxScan + 1)->y >= pptfxScan->y);

        // Collect all ups:

        do {
            if (--cScanEdges == 0)
                goto SetUpForFillingCheck;
            pptfxScan++;
        } while ((pptfxScan + 1)->y <= pptfxScan->y);

        // Collect all downs:

        pptfxTop = pptfxScan;

        do {
            if ((pptfxScan + 1)->y > pptfxFirst->y)
                break;

            if (--cScanEdges == 0)
                goto SetUpForFilling;
            pptfxScan++;
        } while ((pptfxScan + 1)->y >= pptfxScan->y);

        return(FALSE);
    }
    else
    {
        // Collect all ups:

        do {
            pptfxTop++;                 // We increment this now because we
                                        //  want it to point to the very last
                                        //  point if we early out in the next
                                        //  statement...
            if (--cScanEdges == 0)
                goto SetUpForFilling;
        } while ((pptfxTop + 1)->y <= pptfxTop->y);

        // Collect all downs:

        pptfxScan = pptfxTop;
        do {
            if (--cScanEdges == 0)
                goto SetUpForFilling;
            pptfxScan++;
        } while ((pptfxScan + 1)->y >= pptfxScan->y);

        // Collect all ups:

        do {
            if ((pptfxScan + 1)->y < pptfxFirst->y)
                break;

            if (--cScanEdges == 0)
                goto SetUpForFilling;
            pptfxScan++;
        } while ((pptfxScan + 1)->y <= pptfxScan->y);

        return(FALSE);
    }

SetUpForFillingCheck:

    // We check to see if the end of the current edge is higher
    // than the top edge we've found so far:

    if ((pptfxScan + 1)->y < pptfxTop->y)
        pptfxTop = pptfxScan + 1;

SetUpForFilling:

    yTrapezoid = (pptfxTop->y + 15) >> 4;

    // We initialize the hardware for the colour, mix, pixel operation,
    // rectangle height of one, and the y position for the first scan:

    IO_FIFO_WAIT(ppdev, 5);
    IO_CUR_Y(ppdev, yTrapezoid);
    IO_FRGD_COLOR(ppdev, (INT) iSolidColor);
    IO_FRGD_MIX(ppdev, FOREGROUND_COLOR | (WORD) ulHwMix);
    IO_PIX_CNTL(ppdev, ALL_ONES);
    IO_MIN_AXIS_PCNT(ppdev, 0);

    // Make sure we initialize the DDAs appropriately:

    aed[LEFT].cy  = 0;
    aed[RIGHT].cy = 0;

    // For now, guess as to which is the left and which is the right edge:

    aed[LEFT].dptfx  = -(LONG) sizeof(POINTFIX);
    aed[RIGHT].dptfx = sizeof(POINTFIX);
    aed[LEFT].pptfx  = pptfxTop;
    aed[RIGHT].pptfx = pptfxTop;

NextEdge:

    // We loop through this routine on a per-trapezoid basis.

    for (iEdge = 1; iEdge >= 0; iEdge--)
    {
        ped = &aed[iEdge];
        if (ped->cy == 0)
        {
            // Need a new DDA:

            do {
                cEdges--;
                if (cEdges < 0)
                    return(TRUE);

                // Find the next left edge, accounting for wrapping:

                pptfxOld = ped->pptfx;
                ped->pptfx = (POINTFIX*) ((BYTE*) ped->pptfx + ped->dptfx);

                if (ped->pptfx < pptfxFirst)
                    ped->pptfx = pptfxLast;
                else if (ped->pptfx > pptfxLast)
                    ped->pptfx = pptfxFirst;

                // Have to find the edge that spans yTrapezoid:

                ped->cy = ((ped->pptfx->y + 15) >> 4) - yTrapezoid;

                // With fractional coordinate end points, we may get edges
                // that don't cross any scans, in which case we try the
                // next one:

            } while (ped->cy <= 0);

            // 'pptfx' now points to the end point of the edge spanning
            // the scan 'yTrapezoid'.

            dN = ped->pptfx->y - pptfxOld->y;
            dM = ped->pptfx->x - pptfxOld->x;

            ASSERTDD(dN > 0, "Should be going down only");

            // Compute the DDA increment terms:

            if (dM < 0)
            {
                dM = -dM;
                if (dM < dN)                // Can't be '<='
                {
                    ped->dx       = -1;
                    ped->lErrorUp = dN - dM;
                }
                else
                {
                    QUOTIENT_REMAINDER(dM, dN, lQuotient, lRemainder);

                    ped->dx       = -lQuotient;     // - dM / dN
                    ped->lErrorUp = lRemainder;     // dM % dN
                    if (ped->lErrorUp > 0)
                    {
                        ped->dx--;
                        ped->lErrorUp = dN - ped->lErrorUp;
                    }
                }
            }
            else
            {
                if (dM < dN)                // Can't be '<='
                {
                    ped->dx       = 0;
                    ped->lErrorUp = dM;
                }
                else
                {
                    QUOTIENT_REMAINDER(dM, dN, lQuotient, lRemainder);

                    ped->dx       = lQuotient;      // dM / dN
                    ped->lErrorUp = lRemainder;     // dM % dN
                }
            }

            ped->lErrorDown = dN; // DDA limit
            ped->lError     = -1; // Error is initially zero (add dN - 1 for
                                  //  the ceiling, but subtract off dN so that
                                  //  we can check the sign instead of comparing
                                  //  to dN)

            ped->x = pptfxOld->x;
            yStart = pptfxOld->y;

            if ((yStart & 15) != 0)
            {
                // Advance to the next integer y coordinate

                for (i = 16 - (yStart & 15); i != 0; i--)
                {
                    ped->x      += ped->dx;
                    ped->lError += ped->lErrorUp;
                    if (ped->lError >= 0)
                    {
                        ped->lError -= ped->lErrorDown;
                        ped->x++;
                    }
                }
            }

            if ((ped->x & 15) != 0)
            {
                ped->lError -= ped->lErrorDown * (16 - (ped->x & 15));
                ped->x += 15;       // We'll want the ceiling in just a bit...
            }

            // Chop off those fractional bits:

            ped->x      >>= 4;
            ped->lError >>= 4;
        }
    }

    cyTrapezoid = min(aed[LEFT].cy, aed[RIGHT].cy); // # of scans in this trap
    aed[LEFT].cy  -= cyTrapezoid;
    aed[RIGHT].cy -= cyTrapezoid;
    yTrapezoid    += cyTrapezoid;                   // Top scan in next trap

    // If the left and right edges are vertical, simply output as
    // a rectangle:

    if (((aed[LEFT].lErrorUp | aed[RIGHT].lErrorUp) == 0) &&
        ((aed[LEFT].dx       | aed[RIGHT].dx) == 0) &&
        (cyTrapezoid > 1))
    {
        LONG lWidth;

    ContinueVertical:

        lWidth = aed[RIGHT].x - aed[LEFT].x - 1;
        if (lWidth >= 0)
        {
            IO_FIFO_WAIT(ppdev, 5);

            IO_MAJ_AXIS_PCNT(ppdev, lWidth);
            IO_MIN_AXIS_PCNT(ppdev, cyTrapezoid - 1);
            IO_CUR_X(ppdev, aed[LEFT].x);
            IO_CMD(ppdev, RECTANGLE_FILL | DRAWING_DIR_TBLRXM |
                          DRAW           | DIR_TYPE_XY        |
                          LAST_PIXEL_ON  | MULTIPLE_PIXELS    |
                          WRITE);
            IO_MIN_AXIS_PCNT(ppdev, 0);
        }
        else if (lWidth == -1)
        {
            // If the rectangle was too thin to light any pels, we still
            // have to advance the y current position:

            IO_FIFO_WAIT(ppdev, 1);
            IO_CUR_Y(ppdev, yTrapezoid - cyTrapezoid + 1);
        }
        else
        {
            LONG      lTmp;
            POINTFIX* pptfxTmp;

            SWAP(aed[LEFT].x,          aed[RIGHT].x,          lTmp);
            SWAP(aed[LEFT].cy,         aed[RIGHT].cy,         lTmp);
            SWAP(aed[LEFT].dptfx,      aed[RIGHT].dptfx,      lTmp);
            SWAP(aed[LEFT].pptfx,      aed[RIGHT].pptfx,      pptfxTmp);
            goto ContinueVertical;
        }

        goto NextEdge;
    }

    while (TRUE)
    {
        LONG lWidth;

        // The very first time through, make sure we set x:

        lWidth = aed[RIGHT].x - aed[LEFT].x - 1;
        if (lWidth >= 0)
        {
            IO_FIFO_WAIT(ppdev, 3);
            IO_MAJ_AXIS_PCNT(ppdev, lWidth);
            IO_CUR_X(ppdev, aed[LEFT].x);
            IO_CMD(ppdev, RECTANGLE_FILL | DRAWING_DIR_TBLRXM |
                          DRAW           | DIR_TYPE_XY        |
                          LAST_PIXEL_ON  | MULTIPLE_PIXELS    |
                          WRITE);

    ContinueAfterZero:

            // Advance the right wall:

            aed[RIGHT].x      += aed[RIGHT].dx;
            aed[RIGHT].lError += aed[RIGHT].lErrorUp;

            if (aed[RIGHT].lError >= 0)
            {
                aed[RIGHT].lError -= aed[RIGHT].lErrorDown;
                aed[RIGHT].x++;
            }

            // Advance the left wall:

            aed[LEFT].x      += aed[LEFT].dx;
            aed[LEFT].lError += aed[LEFT].lErrorUp;

            if (aed[LEFT].lError >= 0)
            {
                aed[LEFT].lError -= aed[LEFT].lErrorDown;
                aed[LEFT].x++;
            }

            cyTrapezoid--;
            if (cyTrapezoid == 0)
                goto NextEdge;
        }
        else if (lWidth == -1)
        {
            IO_FIFO_WAIT(ppdev, 1);
            IO_CUR_Y(ppdev, yTrapezoid - cyTrapezoid + 1);
            goto ContinueAfterZero;
        }
        else
        {
            // We certainly don't want to optimize for this case because we
            // should rarely get self-intersecting polygons (if we're slow,
            // the app gets what it deserves):

            LONG      lTmp;
            POINTFIX* pptfxTmp;

            SWAP(aed[LEFT].x,          aed[RIGHT].x,          lTmp);
            SWAP(aed[LEFT].dx,         aed[RIGHT].dx,         lTmp);
            SWAP(aed[LEFT].lError,     aed[RIGHT].lError,     lTmp);
            SWAP(aed[LEFT].lErrorUp,   aed[RIGHT].lErrorUp,   lTmp);
            SWAP(aed[LEFT].lErrorDown, aed[RIGHT].lErrorDown, lTmp);
            SWAP(aed[LEFT].cy,         aed[RIGHT].cy,         lTmp);
            SWAP(aed[LEFT].dptfx,      aed[RIGHT].dptfx,      lTmp);
            SWAP(aed[LEFT].pptfx,      aed[RIGHT].pptfx,      pptfxTmp);

            continue;
        }
    }
}