/******************************Module*Header**********************************\
*
*                           *******************
*                           * GDI SAMPLE CODE *
*                           *******************
*
* Module Name: fillpath.c
*
* Content: DrvFillPath support
*
* Copyright (c) 1994-1999 3Dlabs Inc. Ltd. All rights reserved.
* Copyright (c) 1995-2003 Microsoft Corporation.  All rights reserved.
\*****************************************************************************/

//@@BEGIN_DDKSPLIT
// LATER identify convex polygons and special-case?
// LATER identify vertical edges and special-case?
// LATER move pointed-to variables into automatics in search loops
// LATER punt to the engine with segmented framebuffer callbacks
// LATER handle complex clipping
// LATER coalesce rectangles
//@@END_DDKSPLIT

#include "precomp.h"
#include "glint.h"

#define TAKING_ALLOC_STATS  0

#define NUM_BUFFER_POINTS   96      // Maximum number of points in a path
                                    //   for which we'll attempt to join
                                    //   all the path records so that the
                                    //   path may still be drawn by FastFill

#if TAKING_ALLOC_STATS
    ULONG BufferHitInFillpath = 0;
    ULONG BufferMissInFillpath = 0;
#endif

// Describe a single non-horizontal edge of a path to fill.
typedef struct _EDGE {
    PVOID pNext;
    INT iScansLeft;
    INT X;
    INT Y;
    INT iErrorTerm;
    INT iErrorAdjustUp;
    INT iErrorAdjustDown;
    INT iXWhole;
    INT iXDirection;
    INT iWindingDirection;
} EDGE, *PEDGE;

// Maximum number of rects we'll fill per call to
// the fill code
#define MAX_PATH_RECTS  50
#define RECT_BYTES      (MAX_PATH_RECTS * sizeof(RECTL))
#define EDGE_BYTES      (TMP_BUFFER_SIZE - RECT_BYTES)
#define MAX_EDGES       (EDGE_BYTES/sizeof(EDGE))

VOID AdvanceAETEdges(EDGE *pAETHead);
VOID XSortAETEdges(EDGE *pAETHead);
VOID MoveNewEdges(EDGE *pGETHead, EDGE *pAETHead, INT iCurrentY);
EDGE * AddEdgeToGET(EDGE *pGETHead, EDGE *pFreeEdge, POINTFIX *ppfxEdgeStart,
        POINTFIX *ppfxEdgeEnd, RECTL *pClipRect);
BOOL ConstructGET(EDGE *pGETHead, EDGE *pFreeEdges, PATHOBJ *ppo,
        PATHDATA *pd, BOOL bMore, RECTL *pClipRect);
void AdjustErrorTerm(INT *pErrorTerm, INT iErrorAdjustUp, INT iErrorAdjustDown,
        INT yJump, INT *pXStart, INT iXDirection);

/******************************Public*Routine******************************\
* DrvFillPath
*
* Fill the specified path with the specified brush and ROP.
*
\**************************************************************************/

BOOL DrvFillPath(
SURFOBJ*    pso,
PATHOBJ*    ppo,
CLIPOBJ*    pco,
BRUSHOBJ*   pbo,
POINTL*     pptlBrush,
MIX         mix,
FLONG       flOptions)
{
    BYTE jClipping;     // clipping type
    EDGE *pCurrentEdge;
    EDGE AETHead;       // dummy head/tail node & sentinel for Active Edge Table
    EDGE *pAETHead;     // pointer to AETHead
    EDGE GETHead;       // dummy head/tail node & sentinel for Global Edge Table
    EDGE *pGETHead;     // pointer to GETHead
    ULONG ulNumRects;   // # of rectangles to draw currently in rectangle list
    RECTL *prclRects;   // pointer to start of rectangle draw list
    INT iCurrentY;      // scan line for which we're currently scanning out the
                        //  fill
    EDGE *pFreeEdges = NULL;   // pointer to memory free for use to store edges                        

    RBRUSH_COLOR rbc;               // Realized brush or solid color
    ULONG        iSolidColor;       // Copy of pbo->iSolidColor
    GFNFILL     *pfnFill;           // Points to appropriate fill routine

    BOOL         bMore;
    PATHDATA     pd;
    RECTL        ClipRect;
    PDEV        *ppdev = (PDEV*) pso->dhpdev;
    DSURF       *pdsurf;

    BOOL         bRetVal=FALSE;     // FALSE until proven TRUE
    BOOL         bMemAlloced=FALSE; // FALSE until proven TRUE

    FLONG        flFirstRecord;
    POINTFIX*    pptfxTmp;
    ULONG        cptfxTmp;
    POINTFIX     aptfxBuf[NUM_BUFFER_POINTS];
    ULONG        logicop;
    ULONG        bgLogicop;
    GLINT_DECL;

    DISPDBG((DBGLVL, "Entering Fill Path"));

    // Set up the clipping
    if (pco == (CLIPOBJ *) NULL)
    {
        // No CLIPOBJ provided, so we don't have to worry about clipping
        jClipping = DC_TRIVIAL;
    }
    else
    {
        // Use the CLIPOBJ-provided clipping
        jClipping = pco->iDComplexity;
    }

    // There's nothing to do if there are only one or two points
    if (ppo->cCurves <= 2)
    {
        goto ReturnTrue;
    }

    // Pass the surface off to GDI if it's a device bitmap that we've
    // converted to a DIB:

    pdsurf = (DSURF*) pso->dhsurf;

    if (pdsurf->dt & DT_DIB)
    { 
        DISPDBG((DBGLVL, "Passing to GDI"));
        return(EngFillPath(pdsurf->pso, ppo, pco, pbo, pptlBrush, mix,
                           flOptions));
    }

    REMOVE_SWPOINTER(pso);

    VALIDATE_DD_CONTEXT;

    // We'll be drawing to the screen or an off-screen DFB; copy the surface's
    // offset now so that we won't need to refer to the DSURF again:
//@@BEGIN_DDKSPLIT
#if 1
//@@END_DDKSPLIT
    SETUP_PPDEV_OFFSETS(ppdev, pdsurf);
//@@BEGIN_DDKSPLIT
#else
    ppdev->DstPixelOrigin = pdsurf->poh->pixOffset;
    ppdev->xyOffsetDst = MAKEDWORD_XY( pdsurf->poh->x, pdsurf->poh->y );
    ppdev->xOffset = pdsurf->poh->x;
#endif
//@@END_DDKSPLIT

    // It is too difficult to determine interaction between
    // multiple paths, if there is more than one, skip this

    bMore = PATHOBJ_bEnum(ppo, &pd);

    pfnFill = ppdev->pgfnFillSolid;
    logicop = GlintLogicOpsFromR2[mix & 0xFF];
    bgLogicop = GlintLogicOpsFromR2[mix >> 8];
    iSolidColor     = pbo->iSolidColor;
    rbc.iSolidColor = iSolidColor;
    if (rbc.iSolidColor == -1)
    {
        rbc.prb = pbo->pvRbrush;
        if (rbc.prb == NULL)
        {
            DISPDBG((DBGLVL, "Realizing brush"));
            rbc.prb = BRUSHOBJ_pvGetRbrush(pbo);
            if (rbc.prb == NULL)
            {
                return(FALSE);
            }
            
            DISPDBG((DBGLVL, "Realized brush"));
        }
        if (rbc.prb->fl & RBRUSH_2COLOR)
        {
            pfnFill = ppdev->pgfnFillPatMono;
        }
        else
        {
            pfnFill = ppdev->pgfnFillPatColor;
        }
    }

    if (bMore)
    {
        // FastFill only knows how to take a single contiguous buffer
        // of points.  Unfortunately, GDI sometimes hands us paths
        // that are split over multiple path data records.  Convex
        // figures such as Ellipses, Pies and RoundRects are almost
        // always given in multiple records.  Since probably 90% of
        // multiple record paths could still be done by FastFill, for
        // those cases we simply copy the points into a contiguous
        // buffer...

        // First make sure that the entire path would fit in the
        // temporary buffer, and make sure the path isn't comprised
        // of more than one subpath:

        if ((ppo->cCurves >= NUM_BUFFER_POINTS) ||
            (pd.flags & PD_ENDSUBPATH))
        {
            goto SkipFastFill;
        }

        pptfxTmp = &aptfxBuf[0];

        RtlCopyMemory(pptfxTmp, pd.pptfx, sizeof(POINTFIX) * pd.count);

        pptfxTmp     += pd.count;
        cptfxTmp      = pd.count;
        flFirstRecord = pd.flags;       // Remember PD_BEGINSUBPATH flag

        do {
            bMore = PATHOBJ_bEnum(ppo, &pd);

            RtlCopyMemory(pptfxTmp, pd.pptfx, sizeof(POINTFIX) * pd.count);
            cptfxTmp += pd.count;
            pptfxTmp += pd.count;
        } while (!(pd.flags & PD_ENDSUBPATH));

        // Fake up the path data record:
        pd.pptfx  = &aptfxBuf[0];
        pd.count  = cptfxTmp;
        pd.flags |= flFirstRecord;

        // If there's more than one subpath, we can't call FastFill:
        DISPDBG((DBGLVL, "More than one subpath!"));
        if (bMore)
            goto SkipFastFill;
    }

    if ((*ppdev->pgfnFillPolygon)(ppdev, pd.count, pd.pptfx, iSolidColor,
                                logicop, bgLogicop, pco, rbc.prb, pptlBrush))
    {
        DISPDBG((DBGLVL, "Fast Fill Succeeded"));
        return(TRUE);
    }

SkipFastFill:

    DISPDBG((DBGLVL, "Fast Fill Skipped"));

    if (jClipping != DC_TRIVIAL)
    {
        if (jClipping != DC_RECT)
        {
            DISPDBG((DBGLVL, "Complex Clipping"));
            goto ReturnFalse;  // there is complex clipping; let GDI fill the path
        }
        // Clip to the clip rectangle
        ClipRect = pco->rclBounds;
    }
    else
    {
        // So the y-clipping code doesn't do any clipping
        // /16 so we don't blow the values out when we scale up to GIQ
        ClipRect.top = (LONG_MIN + 1) / 16; // +1 to avoid compiler problem
        ClipRect.bottom = LONG_MAX / 16;
    }
    // Set up working storage in the temporary buffer

    prclRects = (RECTL*) ppdev->pvTmpBuffer; // storage for list of rectangles to draw

    if (!bMore)
    {
        RECTL *rectangle;
        INT cPoints = pd.count;

        // The count can't be less than three, because we got all the edges
        // in this subpath, and above we checked that there were at least
        // three edges

        // If the count is four, check to see if the polygon is really a
        // rectangle since we can really speed that up. We'll also check for
        // five with the first and last points the same, because under Win 3.1,
        // it was required to close polygons

        if ((cPoints == 4) ||
           ((cPoints == 5) &&
            (pd.pptfx[0].x == pd.pptfx[4].x) &&
            (pd.pptfx[0].y == pd.pptfx[4].y))) {

            rectangle = prclRects;

        // We have to start somewhere so assume that most
        // applications specify the top left point  first
        //
        // we want to check that the first two points are
        // either vertically or horizontally aligned.  if
        // they are then we check that the last point [3]
        // is either horizontally or  vertically  aligned,
        // and finally that the 3rd point [2] is  aligned
        // with both the first point and the last point.

#define FIX_SHIFT 4L
#define FIX_MASK (- (1 << FIX_SHIFT))

         rectangle->top   = pd.pptfx[0].y - 1 & FIX_MASK;
         rectangle->left  = pd.pptfx[0].x - 1 & FIX_MASK;
         rectangle->right = pd.pptfx[1].x - 1 & FIX_MASK;

         if (rectangle->left ^ rectangle->right)
         {
            if (rectangle->top  ^ (pd.pptfx[1].y - 1 & FIX_MASK))
               goto not_rectangle;

            if (rectangle->left ^ (pd.pptfx[3].x - 1 & FIX_MASK))
               goto not_rectangle;

            if (rectangle->right ^ (pd.pptfx[2].x - 1 & FIX_MASK))
               goto not_rectangle;

            rectangle->bottom = pd.pptfx[2].y - 1 & FIX_MASK;
            if (rectangle->bottom ^ (pd.pptfx[3].y - 1 & FIX_MASK))
               goto not_rectangle;
         }
         else
         {
            if (rectangle->top ^ (pd.pptfx[3].y - 1 & FIX_MASK))
               goto not_rectangle;

            rectangle->bottom = pd.pptfx[1].y - 1 & FIX_MASK;
            if (rectangle->bottom ^ (pd.pptfx[2].y - 1 & FIX_MASK))
               goto not_rectangle;

            rectangle->right = pd.pptfx[2].x - 1 & FIX_MASK;
            if (rectangle->right ^ (pd.pptfx[3].x - 1 & FIX_MASK))
                goto not_rectangle;
         }

         // if the left is greater than the right then
         // swap them so the blt code doesn't wig out

         if (rectangle->left > rectangle->right)
         {
            FIX temp;

            temp = rectangle->left;
            rectangle->left = rectangle->right;
            rectangle->right = temp;
         }
         else
         {
            // if left == right there's nothing to draw

            if (rectangle->left == rectangle->right)
            {
               DISPDBG((DBGLVL, "Nothing to draw"));
               goto ReturnTrue;
            }
         }

         // shift the values to get pixel coordinates

         rectangle->left  = (rectangle->left  >> FIX_SHIFT) + 1;
         rectangle->right = (rectangle->right >> FIX_SHIFT) + 1;

         if (rectangle->top > rectangle->bottom)
         {
            FIX temp;

            temp = rectangle->top;
            rectangle->top = rectangle->bottom;
            rectangle->bottom = temp;
         }
         else
         {
            if (rectangle->top == rectangle->bottom)
            {
               DISPDBG((DBGLVL, "Nothing to draw"));
               goto ReturnTrue;
            }
         }

         // shift the values to get pixel coordinates

         rectangle->top    = (rectangle->top    >> FIX_SHIFT) + 1;
         rectangle->bottom = (rectangle->bottom >> FIX_SHIFT) + 1;

         // Finally, check for clipping

         if (jClipping == DC_RECT)
         {
            // Clip to the clip rectangle
            if (!bIntersect(rectangle, &ClipRect, rectangle))
            {
                // Totally clipped, nothing to do
                DISPDBG((DBGLVL, "Nothing to draw"));
                goto ReturnTrue;
            }
         }

         // if we get here then the polygon is a rectangle,
         // set count to 1 and goto bottom to draw it 

         ulNumRects = 1;
         goto draw_remaining_rectangles;
      }

not_rectangle:

        ;
    }

    // Do we have enough memory for all the edges?
    // LATER does cCurves include closure?
    if (ppo->cCurves > MAX_EDGES)
    {
#if TAKING_ALLOC_STATS
        BufferMissInFillpath++;
#endif
        //
        // try to allocate enough memory
        //
        pFreeEdges = (EDGE *) ENGALLOCMEM(FL_ZERO_MEMORY, 
                                          (ppo->cCurves * sizeof(EDGE)), 
                                          ALLOC_TAG_GDI(6));
        if (pFreeEdges == NULL)
        {
            DISPDBG((DBGLVL, "Too many edges"));
            goto ReturnFalse;  // too many edges; let GDI fill the path
        }
        else
        {
            bMemAlloced = TRUE;
        }
    }
    else
    {
#if TAKING_ALLOC_STATS
        BufferHitInFillpath++;
#endif
        pFreeEdges = (EDGE*) ((BYTE*) ppdev->pvTmpBuffer + RECT_BYTES);
        // use our handy temporary buffer (it's big enough)
    }

    // Initialize an empty list of rectangles to fill
    ulNumRects = 0;

    // Enumerate the path edges and build a Global Edge Table (GET) from them
    // in YX-sorted order.
    pGETHead = &GETHead;
    if (!ConstructGET(pGETHead, pFreeEdges, ppo, &pd, bMore, &ClipRect))
    {
        DISPDBG((DBGLVL, "Outside Range"));
        goto ReturnFalse;  // outside GDI's 2**27 range
    }

    // Create an empty AET with the head node also a tail sentinel
    pAETHead = &AETHead;
    AETHead.pNext = pAETHead;  // mark that the AET is empty
    AETHead.X = 0x7FFFFFFF;    // this is greater than any valid X value, so
                               //  searches will always terminate

    // Top scan of polygon is the top of the first edge we come to
    iCurrentY = ((EDGE *)GETHead.pNext)->Y;

    // Loop through all the scans in the polygon, adding edges from the GET to
    // the Active Edge Table (AET) as we come to their starts, and scanning out
    // the AET at each scan into a rectangle list. Each time it fills up, the
    // rectangle list is passed to the filling routine, and then once again at
    // the end if any rectangles remain undrawn. We continue so long as there
    // are edges to be scanned out
    while (1) {

        // Advance the edges in the AET one scan, discarding any that have
        // reached the end (if there are any edges in the AET)
        if (AETHead.pNext != pAETHead)
        {
            AdvanceAETEdges(pAETHead);
        }

        // If the AET is empty, done if the GET is empty, else jump ahead to
        // the next edge in the GET; if the AET isn't empty, re-sort the AET
        if (AETHead.pNext == pAETHead)
        {
            if (GETHead.pNext == pGETHead)
            {
                // Done if there are no edges in either the AET or the GET
                break;
            }
            // There are no edges in the AET, so jump ahead to the next edge in
            // the GET
            iCurrentY = ((EDGE *)GETHead.pNext)->Y;
        }
        else
        {
            // Re-sort the edges in the AET by X coordinate, if there are at
            // least two edges in the AET (there could be one edge if the
            // balancing edge hasn't yet been added from the GET)
            if (((EDGE *)AETHead.pNext)->pNext != pAETHead)
            {
                XSortAETEdges(pAETHead);
            }
        }

        // Move any new edges that start on this scan from the GET to the AET;
        // bother calling only if there's at least one edge to add
        if (((EDGE *)GETHead.pNext)->Y == iCurrentY)
        {
            MoveNewEdges(pGETHead, pAETHead, iCurrentY);
        }

        // Scan the AET into rectangles to fill (there's always at least one
        // edge pair in the AET)
        pCurrentEdge = AETHead.pNext;   // point to the first edge
        do {
            INT iLeftEdge;

            // The left edge of any given edge pair is easy to find; it's just
            // wherever we happen to be currently
            iLeftEdge = pCurrentEdge->X;

            // Find the matching right edge according to the current fill rule
            if ((flOptions & FP_WINDINGMODE) != 0)
            {
                INT iWindingCount;

                // Do winding fill; scan across until we've found equal numbers
                // of up and down edges
                iWindingCount = pCurrentEdge->iWindingDirection;
                do {
                    pCurrentEdge = pCurrentEdge->pNext;
                    iWindingCount += pCurrentEdge->iWindingDirection;
                } while (iWindingCount != 0);
            }
            else
            {
                // Odd-even fill; the next edge is the matching right edge
                pCurrentEdge = pCurrentEdge->pNext;
            }

            // See if the resulting span encompasses at least one pixel, and
            // add it to the list of rectangles to draw if so
            if (iLeftEdge < pCurrentEdge->X)
            {
                // We've got an edge pair to add to the list to be filled; see
                // if there's room for one more rectangle
                if (ulNumRects >= MAX_PATH_RECTS)
                {
                    // No more room; draw the rectangles in the list and reset
                    // it to empty
                   (*pfnFill)(ppdev, ulNumRects, prclRects, logicop, bgLogicop,
                               rbc, pptlBrush);

                    // Reset the list to empty
                    ulNumRects = 0;
                }

                // Add the rectangle representing the current edge pair
                if (jClipping == DC_RECT)
                {
                    // Clipped
                    // Clip to left
                    prclRects[ulNumRects].left = max(iLeftEdge, ClipRect.left);
                    // Clip to right
                    prclRects[ulNumRects].right =
                            min(pCurrentEdge->X, ClipRect.right);
                    // Draw only if not fully clipped
                    if (prclRects[ulNumRects].left <
                            prclRects[ulNumRects].right)
                    {
                        prclRects[ulNumRects].top = iCurrentY;
                        prclRects[ulNumRects].bottom = iCurrentY+1;
                        ulNumRects++;
                    }
                }
                else
                {
                    // Unclipped
                    prclRects[ulNumRects].top = iCurrentY;
                    prclRects[ulNumRects].bottom = iCurrentY+1;
                    prclRects[ulNumRects].left = iLeftEdge;
                    prclRects[ulNumRects].right = pCurrentEdge->X;
                    ulNumRects++;
                }
            }
        } while ((pCurrentEdge = pCurrentEdge->pNext) != pAETHead);

        iCurrentY++;    // next scan
    }

// Draw the remaining rectangles, if there are any.

draw_remaining_rectangles:

    if (ulNumRects > 0)
    {
        (*pfnFill)(ppdev, ulNumRects, prclRects, logicop, bgLogicop,
                   rbc, pptlBrush);
    }

ReturnTrue:
    DISPDBG((DBGLVL, "Drawn"));
    bRetVal = TRUE; // done successfully

ReturnFalse:

    // bRetVal is originally false.  If you jumped to ReturnFalse from somewhere,
    // then it will remain false, and be returned.

    if (bMemAlloced)
    {
        //
        // we did allocate memory, so release it
        //
        ENGFREEMEM(pFreeEdges);
    }

    DISPDBG((DBGLVL, "Returning %s", bRetVal ? "True" : "False"));
    return(bRetVal);
}

// Advance the edges in the AET to the next scan, dropping any for which we've
// done all scans. Assumes there is at least one edge in the AET.

VOID AdvanceAETEdges(EDGE *pAETHead)
{
    EDGE *pLastEdge, *pCurrentEdge;

    pLastEdge = pAETHead;
    pCurrentEdge = pLastEdge->pNext;
    do {

        // Count down this edge's remaining scans
        if (--pCurrentEdge->iScansLeft == 0)
        {
            // We've done all scans for this edge; drop this edge from the AET
            pLastEdge->pNext = pCurrentEdge->pNext;
        }
        else
        {
            // Advance the edge's X coordinate for a 1-scan Y advance
            // Advance by the minimum amount
            pCurrentEdge->X += pCurrentEdge->iXWhole;
            // Advance the error term and see if we got one extra pixel this
            // time
            pCurrentEdge->iErrorTerm += pCurrentEdge->iErrorAdjustUp;
            if (pCurrentEdge->iErrorTerm >= 0)
            {
                // The error term turned over, so adjust the error term and
                // advance the extra pixel
                pCurrentEdge->iErrorTerm -= pCurrentEdge->iErrorAdjustDown;
                pCurrentEdge->X += pCurrentEdge->iXDirection;
            }

            pLastEdge = pCurrentEdge;
        }
    } while ((pCurrentEdge = pLastEdge->pNext) != pAETHead);
}

// X-sort the AET, because the edges may have moved around relative to
// one another when we advanced them. We'll use a multipass bubble
// sort, which is actually okay for this application because edges
// rarely move relative to one another, so we usually do just one pass.
// Also, this makes it easy to keep just a singly-linked list. Assumes there
// are at least two edges in the AET.

VOID XSortAETEdges(EDGE *pAETHead)
{
    BOOL bEdgesSwapped;
    EDGE *pLastEdge, *pCurrentEdge, *pNextEdge;

    do {

        bEdgesSwapped = FALSE;
        pLastEdge = pAETHead;
        pCurrentEdge = pLastEdge->pNext;
        pNextEdge = pCurrentEdge->pNext;

        do {
            if (pNextEdge->X < pCurrentEdge->X)
            {
                // Next edge is to the left of the current edge; swap them
                pLastEdge->pNext = pNextEdge;
                pCurrentEdge->pNext = pNextEdge->pNext;
                pNextEdge->pNext = pCurrentEdge;
                bEdgesSwapped = TRUE;
                pCurrentEdge = pNextEdge;   // continue sorting before the edge
                                            //  we just swapped; it might move
                                            //  farther yet
            }
            pLastEdge = pCurrentEdge;
            pCurrentEdge = pLastEdge->pNext;
        } while ((pNextEdge = pCurrentEdge->pNext) != pAETHead);
    } while (bEdgesSwapped);
}

// Moves all edges that start on the current scan from the GET to the AET in
// X-sorted order. Parameters are pointer to head of GET and pointer to dummy
// edge at head of AET, plus current scan line. Assumes there's at least one
// edge to be moved.

VOID MoveNewEdges(EDGE *pGETHead, EDGE *pAETHead, INT iCurrentY)
{
    EDGE *pCurrentEdge = pAETHead;
    EDGE *pGETNext = pGETHead->pNext;

    do {

        // Scan through the AET until the X-sorted insertion point for this
        // edge is found. We can continue from where the last search left
        // off because the edges in the GET are in X sorted order, as is
        // the AET. The search always terminates because the AET sentinel
        // is greater than any valid X
        while (pGETNext->X > ((EDGE *)pCurrentEdge->pNext)->X) 
        {
            pCurrentEdge = pCurrentEdge->pNext;
        }

        // We've found the insertion point; add the GET edge to the AET, and
        // remove it from the GET
        pGETHead->pNext = pGETNext->pNext;
        pGETNext->pNext = pCurrentEdge->pNext;
        pCurrentEdge->pNext = pGETNext;
        pCurrentEdge = pGETNext;    // continue insertion search for the next
                                    //  GET edge after the edge we just added
        pGETNext = pGETHead->pNext;

    } while (pGETNext->Y == iCurrentY);
}

// Build the Global Edge Table from the path. There must be enough memory in
// the free edge area to hold all edges. The GET is constructed in Y-X order,
// and has a head/tail/sentinel node at pGETHead.

BOOL ConstructGET(
    EDGE     *pGETHead,
    EDGE     *pFreeEdges,
    PATHOBJ  *ppo,
    PATHDATA *pd,
    BOOL      bMore,
    RECTL    *pClipRect)
{
    POINTFIX pfxPathStart;    // point that started the current subpath
    POINTFIX pfxPathPrevious; // point before the current point in a subpath;
                              //  starts the current edge

    // Create an empty GET with the head node also a tail sentinel

    pGETHead->pNext = pGETHead; // mark that the GET is empty
    pGETHead->Y = 0x7FFFFFFF;   // this is greater than any valid Y value, so
                                //  searches will always terminate

    // PATHOBJ_vEnumStart is implicitly performed by engine
    // already and first path is enumerated by the caller.

next_subpath:

    // Make sure the PATHDATA is not empty (is this necessary)

    if (pd->count != 0)
    {
       // If first point starts a subpath, remember it as such
       // and go on to the next point, so we can get an edge

       if (pd->flags & PD_BEGINSUBPATH)
       {
           // the first point starts the subpath; remember it
  
           pfxPathStart    = *pd->pptfx; // the subpath starts here
           pfxPathPrevious = *pd->pptfx; // this points starts the next edge
           pd->pptfx++;                  // advance to the next point
           pd->count--;                  // count off this point
       }

       // Add edges in PATHDATA to GET, in Y-X sorted order 

       while (pd->count--)
       {
           if ((pFreeEdges =
                 AddEdgeToGET(pGETHead, pFreeEdges, &pfxPathPrevious, pd->pptfx,
                              pClipRect)) == NULL)
           {
               goto ReturnFalse;
           }

           pfxPathPrevious = *pd->pptfx; // current point becomes previous
           pd->pptfx++;                  // advance to the next point
       }

       // If last point ends the subpath, insert the edge that
       // connects to first point (is this built in already?)

       if (pd->flags & PD_ENDSUBPATH)
       {
           if ((pFreeEdges = AddEdgeToGET(pGETHead, pFreeEdges, &pfxPathPrevious,
                                          &pfxPathStart, pClipRect)) == NULL)
           {
               goto ReturnFalse;
           }
       }
   }

   // The initial loop conditions preclude a do, while or for

   if (bMore)
   {
       bMore = PATHOBJ_bEnum(ppo, pd);
       goto next_subpath;
   }

    return(TRUE);   // done successfully

ReturnFalse:

    return(FALSE);  // failed
}

// Adds the edge described by the two passed-in points to the Global Edge
// Table, if the edge spans at least one pixel vertically.

EDGE * AddEdgeToGET(EDGE *pGETHead, EDGE *pFreeEdge,
        POINTFIX *ppfxEdgeStart, POINTFIX *ppfxEdgeEnd, RECTL *pClipRect)
{
    INT iYStart, iYEnd, iXStart, iXEnd, iYHeight, iXWidth;
    INT yJump, yTop;

    // Set the winding-rule direction of the edge, and put the endpoints in
    // top-to-bottom order

    iYHeight = ppfxEdgeEnd->y - ppfxEdgeStart->y;
    if (iYHeight == 0)
    {
        return(pFreeEdge);  // zero height; ignore this edge
    }
    else if (iYHeight >= 0)
    {
        iXStart = ppfxEdgeStart->x;
        iYStart = ppfxEdgeStart->y;
        iXEnd = ppfxEdgeEnd->x;
        iYEnd = ppfxEdgeEnd->y;
        pFreeEdge->iWindingDirection = 1;
    }
    else
    {
        iYHeight = -iYHeight;
        iXEnd = ppfxEdgeStart->x;
        iYEnd = ppfxEdgeStart->y;
        iXStart = ppfxEdgeEnd->x;
        iYStart = ppfxEdgeEnd->y;
        pFreeEdge->iWindingDirection = -1;
    }

    if (iYHeight & 0x80000000)
    {
        return(NULL);       // too large; outside 2**27 GDI range
    }

    // Set the error term and adjustment factors, all in GIQ coordinates for
    // now

    iXWidth = iXEnd - iXStart;
    if (iXWidth >= 0)
    {
        // Left to right, so we change X as soon as we move at all
        pFreeEdge->iXDirection = 1;
        pFreeEdge->iErrorTerm = -1;
    }
    else
    {
        // Right to left, so we don't change X until we've moved a full GIQ
        // coordinate
        iXWidth = -iXWidth;
        pFreeEdge->iXDirection = -1;
        pFreeEdge->iErrorTerm = -iYHeight;
    }

    if (iXWidth & 0x80000000)
    {
        return(NULL);       // too large; outside 2**27 GDI range
    }

    if (iXWidth >= iYHeight)
    {
        // Calculate base run length (minimum distance advanced in X for a 1-
        // scan advance in Y)
        pFreeEdge->iXWhole = iXWidth / iYHeight;
        // Add sign back into base run length if going right to left
        if (pFreeEdge->iXDirection == -1)
        {
            pFreeEdge->iXWhole = -pFreeEdge->iXWhole;
        }
        pFreeEdge->iErrorAdjustUp = iXWidth % iYHeight;
    }
    else
    {
        // Base run length is 0, because line is closer to vertical than
        // horizontal
        pFreeEdge->iXWhole = 0;
        pFreeEdge->iErrorAdjustUp = iXWidth;
    }
    pFreeEdge->iErrorAdjustDown = iYHeight;

    // Calculate the number of pixels spanned by this edge, accounting for
    // clipping

    // Top true pixel scan in GIQ coordinates
    // Shifting to divide and multiply by 16 is okay because the clip rect
    // always contains positive numbers
    yTop = max(pClipRect->top << 4, (iYStart + 15) & ~0x0F);
    pFreeEdge->Y = yTop >> 4;    // initial scan line on which to fill edge

    // Calculate # of scans to actually fill, accounting for clipping
    if ((pFreeEdge->iScansLeft = min(pClipRect->bottom, ((iYEnd + 15) >> 4))
            - pFreeEdge->Y) <= 0)
    {
        return(pFreeEdge);  // no pixels at all are spanned, so we can
                            // ignore this edge
    }

    // If the edge doesn't start on a pixel scan (that is, it starts at a
    // fractional GIQ coordinate), advance it to the first pixel scan it
    // intersects. Ditto if there's top clipping. Also clip to the bottom if
    // needed

    if (iYStart != yTop)
    {
        // Jump ahead by the Y distance in GIQ coordinates to the first pixel
        // to draw
        yJump = yTop - iYStart;

        // Advance x the minimum amount for the number of scans traversed
        iXStart += pFreeEdge->iXWhole * yJump;

        AdjustErrorTerm(&pFreeEdge->iErrorTerm, pFreeEdge->iErrorAdjustUp,
                        pFreeEdge->iErrorAdjustDown, yJump, &iXStart,
                        pFreeEdge->iXDirection);
    }

    // Turn the calculations into pixel rather than GIQ calculations

    // Move the X coordinate to the nearest pixel, and adjust the error term
    // accordingly
    // Dividing by 16 with a shift is okay because X is always positive

    pFreeEdge->X = (iXStart + 15) >> 4; // convert from GIQ to pixel coordinates

//@@BEGIN_DDKSPLIT
    // LATER adjust only if needed (if prestepped above)?
//@@END_DDKSPLIT
    if (pFreeEdge->iXDirection == 1)
    {
        // Left to right
        pFreeEdge->iErrorTerm -= pFreeEdge->iErrorAdjustDown *
                (((iXStart + 15) & ~0x0F) - iXStart);
    }
    else
    {
        // Right to left
        pFreeEdge->iErrorTerm -= pFreeEdge->iErrorAdjustDown *
                ((iXStart - 1) & 0x0F);
    }

    // Scale the error term down 16 times to switch from GIQ to pixels.
    // Shifts work to do the multiplying because these values are always
    // non-negative
    pFreeEdge->iErrorTerm >>= 4;

    // Insert the edge into the GET in YX-sorted order. The search always ends
    // because the GET has a sentinel with a greater-than-possible Y value
    while ((pFreeEdge->Y > ((EDGE *)pGETHead->pNext)->Y) ||
            ((pFreeEdge->Y == ((EDGE *)pGETHead->pNext)->Y) &&
            (pFreeEdge->X > ((EDGE *)pGETHead->pNext)->X)))
    {
        pGETHead = pGETHead->pNext;
    }

    pFreeEdge->pNext = pGETHead->pNext; // link the edge into the GET
    pGETHead->pNext = pFreeEdge;

    return(++pFreeEdge);    // point to the next edge storage location for next
                            //  time
}

// Adjust the error term for a skip ahead in y. This is in ASM because there's
// a multiply/divide that may involve a larger than 32-bit value.

void AdjustErrorTerm(INT *pErrorTerm, INT iErrorAdjustUp, INT iErrorAdjustDown,
        INT yJump, INT *pXStart, INT iXDirection)
{
#if defined(_X86_) || defined(i386)
    // Adjust the error term up by the number of y coordinates we'll skip
    //*pErrorTerm += iErrorAdjustUp * yJump;
    _asm    mov ebx,pErrorTerm
    _asm    mov eax,iErrorAdjustUp
    _asm    mul yJump
    _asm    add eax,[ebx]
    _asm    adc edx,-1      // the error term starts out negative

    // See if the error term turned over even once while skipping
    // if (*pErrorTerm >= 0) {
    _asm    js  short NoErrorTurnover

        // # of times we'll turn over the error term and step an extra x
        // coordinate while skipping
        // NumAdjustDowns = (*pErrorTerm / iErrorAdjustDown) + 1;
        _asm    div iErrorAdjustDown
        _asm    inc eax
        // Note that EDX is the remainder; (EDX - iErrorAdjustDown) is where
        // the error term ends up ultimately

        // Advance x appropriately for the # of times the error term
        // turned over
        // if (iXDirection == 1) {
        //     *pXStart += NumAdjustDowns;
        // } else {
        //     *pXStart -= NumAdjustDowns;
        // }
        _asm    mov ecx,pXStart
        _asm    cmp iXDirection,1
        _asm    jz  short GoingRight
        _asm    neg eax
GoingRight:
        _asm    add [ecx],eax

        // Adjust the error term down to its proper post-skip value
        // *pErrorTerm -= iErrorAdjustDown * NumAdjustDowns;
        _asm    sub edx,iErrorAdjustDown
        _asm    mov eax,edx     // put into EAX for storing to pErrorTerm next
        // }
NoErrorTurnover:
        _asm    mov [ebx],eax
#else

    // LONGLONGS are 64 bit integers (We hope!) as the multiply could
    // overflow 32 bit integers. If 64 bit ints are unsupported, the
    // LONGLONG will end up as a double. Hopefully there will be no
    // noticable difference in accuracy.
    LONGLONG NumAdjustDowns;
    LONGLONG tmpError = *pErrorTerm;

    // Adjust the error term up by the number of y coordinates we'll skip
    tmpError += (LONGLONG)iErrorAdjustUp * (LONGLONG)yJump;

    // See if the error term turned over even once while skipping
    if (tmpError >= 0)
    {
        // # of times we'll turn over the error term and step an extra x
        // coordinate while skipping
        NumAdjustDowns = (tmpError / (LONGLONG)iErrorAdjustDown) + 1;

        // Advance x appropriately for the # of times the error term
        // turned over
        if (iXDirection == 1)
        {
            *pXStart += (LONG) NumAdjustDowns;
        }
        else
        {
            *pXStart -= (LONG) NumAdjustDowns;
        }

        // Adjust the error term down to its proper post-skip value
        tmpError -= (LONGLONG)iErrorAdjustDown * NumAdjustDowns;
    }

    *pErrorTerm = (LONG)tmpError;

#endif  // X86
}