gwinding.cpp

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// $Id: gwinding.cpp 751 2006-03-31 15:43:49Z alex $
/* @@tag:xara-cn@@ DO NOT MODIFY THIS LINE
================================XARAHEADERSTART===========================
 
               Xara LX, a vector drawing and manipulation program.
                    Copyright (C) 1993-2006 Xara Group Ltd.
       Copyright on certain contributions may be held in joint with their
              respective authors. See AUTHORS file for details.

LICENSE TO USE AND MODIFY SOFTWARE
----------------------------------

This file is part of Xara LX.

Xara LX is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License version 2 as published
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-----------------

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=================================XARAHEADEREND============================
 */
// Gavin's path winding code

/*
*/

#include "camtypes.h"

//
// GWinding.cpp
//

#include <math.h>
#include "gwinding.h"


INT32 GWSgnMulSubMul( INT32 A, INT32 B, INT32 C, INT32 D )
{
#if defined(__WXMSW__)
    UINT32 temp ;
    __asm {
        mov     eax,A
        imul    B
        mov     ebx,eax
        mov     ecx,edx
        mov     eax,C
        imul    D
        sub     ebx,eax
        sbb     ecx,edx
        jne     returnecx
        or      ecx,ebx
        jns     returnecx
            not     ecx
returnecx:
        mov     temp,ecx
    }
    return temp;
#else
    XLONG X = (XLONG)A*B-(XLONG)C*D;
    return X>0 ? 1 : X<0 ? -1 : 0 ;
#endif
}


PPOINT Points ;
PPOINT StartPoint ;

POINT BottomLeft ;
POINT PrevPoint ;
POINT LastPoint ;
POINT OldPoint ;

POINT Prev_Point ;
POINT Next_Point ;

INT32 Flags ;

UINT32 Flatness ;
UINT32 BottomLeftOffset ;


void DoLine( POINT P )
{
    if ( (Flags & 04) && ( OldPoint.x!=LastPoint.x || OldPoint.y!=LastPoint.y ) )
    {
        PrevPoint = LastPoint ;
        Flags &= ~04 ;
    }
    if (  P.x+P.y >  BottomLeft.x+BottomLeft.y ||
         (P.x+P.y == BottomLeft.x+BottomLeft.y &&
              P.y >=              BottomLeft.y) )
    {
        if ( (Flags & 02) && ( P.x!=BottomLeft.x ||
                               P.y!=BottomLeft.y ) )
        {
            Next_Point = P ;
            Flags &= ~02 ;
        }
        Flags |= 04 ;
    }
    else
    {
        Prev_Point = PrevPoint ;
        BottomLeft = P ;
        BottomLeftOffset = Points-StartPoint ; /* Save curve offset */
        Flags = 02 ;
        PrevPoint = P ;
    }
    OldPoint = LastPoint ;
    LastPoint = P ;
}


void FlattenSplit( POINT P0, POINT P1, POINT P2, POINT P3 ) ;

void FlattenCurve( POINT P0, POINT P1, POINT P2, POINT P3 )
{
    UINT32 dx,dy ;
    dx = abs(P1.x*3 - P0.x*2 - P3.x) ;
    dy = abs(P1.y*3 - P0.y*2 - P3.y) ;
    if ( (dx>=dy ? 3*dx+dy : dx+3*dy) > Flatness )
        FlattenSplit(P0,P1,P2,P3) ;
    else
    {
        dx = abs(P2.x*3 - P0.x - P3.x*2) ;
        dy = abs(P2.y*3 - P0.y - P3.y*2) ;
        if ( (dx>=dy ? 3*dx+dy : dx+3*dy) > Flatness )
            FlattenSplit(P0,P1,P2,P3) ;
        else
            DoLine(P3) ;
    }
}


void FlattenSplit( POINT P0, POINT P1, POINT P2, POINT P3 )
{
    POINT L1, L2, M, R1, R2 ;
    L1.x = (P0.x + P1.x)/2;
    L1.y = (P0.y + P1.y)/2;
    L2.x = (P0.x + 2*P1.x + P2.x)/4;
    L2.y = (P0.y + 2*P1.y + P2.y)/4;
     M.x = (P0.x + 3*P1.x + 3*P2.x + P3.x)/8;
     M.y = (P0.y + 3*P1.y + 3*P2.y + P3.y)/8;
    R1.x = (P1.x + 2*P2.x + P3.x)/4;
    R1.y = (P1.y + 2*P2.y + P3.y)/4;
    R2.x = (P2.x + P3.x)/2;
    R2.y = (P2.y + P3.y)/2;
    FlattenCurve(P0, L1, L2, M) ;
    FlattenCurve(M, R1, R2, P3) ;
}


BOOL GWinding(
        PPOINT  pPoints,
        PBYTE   Types,
        INT32   Length,
        UINT32  pFlatness,
        UINT32  &pBottomLeftOffset,
        POINT   &pBottomLeft
    )
{
    Flatness = pFlatness*27/2 ;
    StartPoint = Points = pPoints ;
    BottomLeft = PrevPoint = LastPoint = *Points++ ; Types++ ; --Length ;
    BottomLeftOffset = 0 ;
    Flags = 03 ;
    while ( Length>0 )
    {
        if ( (*Types & PT_MOVETO)==PT_LINETO )
        {
            DoLine( Points[0] ) ;
            Points++ ; Types++ ; --Length ;
        }
        else /* Curve */
        {
            FlattenCurve( Points[-1],Points[0],Points[1],Points[2] ) ;
            Points+=3 ; Types+=3 ; Length-=3 ;
        }
    }
    if ( BottomLeft.x!=LastPoint.x || BottomLeft.y!=LastPoint.y )
        PrevPoint = LastPoint ;
    if ( Flags & 01 )
        Prev_Point = PrevPoint ;
    else if ( Flags & 02 )
        Next_Point = *StartPoint ;
    pBottomLeftOffset = BottomLeftOffset ;
    pBottomLeft = BottomLeft ;
    INT32 Sgn = GWSgnMulSubMul( Next_Point.x-BottomLeft.x, Prev_Point.y-BottomLeft.y,
                             Prev_Point.x-BottomLeft.x, Next_Point.y-BottomLeft.y ) ;
    if ( Sgn )
        return Sgn<0 ;
    Sgn = Next_Point.x-Prev_Point.x ;
    if ( Sgn )
        return Sgn<0 ;
    Sgn = Prev_Point.y-Next_Point.y ;
    return Sgn<0 ;
}

---