text: /***********************************************************
  
  Copyright 1987, 1998  The Open Group
  
  Permission to use, copy, modify, distribute, and sell this software and its
  documentation for any purpose is hereby granted without fee, provided that
  the above copyright notice appear in all copies and that both that
  copyright notice and this permission notice appear in supporting
  documentation.
  
  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  Except as contained in this notice, the name of The Open Group shall not be
  used in advertising or otherwise to promote the sale, use or other dealings
  in this Software without prior written authorization from The Open Group.
  
  
  Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts.
  
                          All Rights Reserved
  
  Permission to use, copy, modify, and distribute this software and its 
  documentation for any purpose and without fee is hereby granted, 
  provided that the above copyright notice appear in all copies and that
  both that copyright notice and this permission notice appear in 
  supporting documentation, and that the name of Digital not be
  used in advertising or publicity pertaining to distribution of the
  software without specific, written prior permission.  
  
  DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
  ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
  DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
  ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
  WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
  ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  SOFTWARE.
  
  ******************************************************************/
  #ifdef HAVE_DIX_CONFIG_H
  #include <dix-config.h>
  #endif
  
  #include <math.h>
  #include <X11/X.h>
  #include "gcstruct.h"
  #include "windowstr.h"
  #include "pixmapstr.h"
  #include "mifpoly.h"
  
  static int GetFPolyYBounds(SppPointPtr pts, int n, double yFtrans,
  			   int *by, int *ty);
  
  /*
   *	Written by Todd Newman; April. 1987.
   *
   *	Fill a convex polygon.  If the given polygon
   *	is not convex, then the result is undefined.
   *	The algorithm is to order the edges from smallest
   *	y to largest by partitioning the array into a left
   *	edge list and a right edge list.  The algorithm used
   *	to traverse each edge is digital differencing analyzer
   *	line algorithm with y as the major axis. There's some funny linear
   *	interpolation involved because of the subpixel postioning.
   */
  void
  miFillSppPoly(dst, pgc, count, ptsIn, xTrans, yTrans, xFtrans, yFtrans)
      DrawablePtr 	dst;
      GCPtr		pgc;
      int			count;          /* number of points */
      SppPointPtr 	ptsIn;          /* the points */
      int			xTrans, yTrans;	/* Translate each point by this */
      double		xFtrans, yFtrans;	/* translate before conversion
      						   by this amount.  This provides
  						   a mechanism to match rounding
  						   errors with any shape that must
  						   meet the polygon exactly.
  						 */
  {
      double		xl = 0.0, xr = 0.0,	/* x vals of left and right edges */
            		ml = 0.0,      	/* left edge slope */
            		mr = 0.0,       /* right edge slope */
            		dy,             /* delta y */
      			i;              /* loop counter */
      int			y,              /* current scanline */
      			j,
      			imin,           /* index of vertex with smallest y */
      			ymin,           /* y-extents of polygon */
      			ymax,
      			*width,
      			*FirstWidth,    /* output buffer */
      	 		*Marked;	/* set if this vertex has been used */
      int			left, right,	/* indices to first endpoints */
      			nextleft,
                   	nextright;	/* indices to second endpoints */
      DDXPointPtr 	ptsOut,
      			FirstPoint;	/* output buffer */
  
      if (pgc->miTranslate)
      {
  	xTrans += dst->x;
  	yTrans += dst->y;
      }
  
      imin = GetFPolyYBounds(ptsIn, count, yFtrans, &ymin, &ymax);
  
      y = ymax - ymin + 1;
      if ((count < 3) || (y <= 0))
  	return;
      ptsOut = FirstPoint = (DDXPointPtr)xalloc(sizeof(DDXPointRec) * y);
      width = FirstWidth = (int *) xalloc(sizeof(int) * y);
      Marked = (int *) xalloc(sizeof(int) * count);
  
      if(!ptsOut || !width || !Marked)
      {
  	if (Marked) xfree(Marked);
  	if (width) xfree(width);
  	if (ptsOut) xfree(ptsOut);
  	return;
      }
  
      for(j = 0; j < count; j++)
  	Marked[j] = 0;
      nextleft = nextright = imin;
      Marked[imin] = -1;
      y = ICEIL(ptsIn[nextleft].y + yFtrans);
  
      /*
       *  loop through all edges of the polygon
       */
      do
      {
          /* add a left edge if we need to */
          if ((y > (ptsIn[nextleft].y + yFtrans) ||
   	     ISEQUAL(y, ptsIn[nextleft].y + yFtrans)) &&
  	     Marked[nextleft] != 1)
  	{
  	    Marked[nextleft]++;
              left = nextleft++;
  
              /* find the next edge, considering the end conditions */
              if (nextleft >= count)
                  nextleft = 0;
  
              /* now compute the starting point and slope */
  	    dy = ptsIn[nextleft].y - ptsIn[left].y;
  	    if (dy != 0.0)
  	    { 
  		ml = (ptsIn[nextleft].x - ptsIn[left].x) / dy;
  		dy = y - (ptsIn[left].y + yFtrans);
  		xl = (ptsIn[left].x + xFtrans) + ml * max(dy, 0); 
  	    }
          }
  
          /* add a right edge if we need to */
          if ((y > ptsIn[nextright].y + yFtrans) ||
   	     (ISEQUAL(y, ptsIn[nextright].y + yFtrans)
  	     && Marked[nextright] != 1))
  	{
  	    Marked[nextright]++;
              right = nextright--;
  
              /* find the next edge, considering the end conditions */
              if (nextright < 0)
                  nextright = count - 1;
  
              /* now compute the starting point and slope */
  	    dy = ptsIn[nextright].y - ptsIn[right].y;
  	    if (dy != 0.0) 
  	    { 
  		mr = (ptsIn[nextright].x - ptsIn[right].x) / dy;
  		dy = y - (ptsIn[right].y + yFtrans); 
  		xr = (ptsIn[right].x + xFtrans) + mr * max(dy, 0);
  	    }
          }
  
  
          /*
           *  generate scans to fill while we still have
           *  a right edge as well as a left edge.
           */
          i = (min(ptsIn[nextleft].y, ptsIn[nextright].y) + yFtrans) - y;
  
  	if (i < EPSILON)
  	{
  	    if(Marked[nextleft] && Marked[nextright])
  	    {
  	        /* Arrgh, we're trapped! (no more points) 
  	         * Out, we've got to get out of here before this decadence saps
  	         * our will completely! */
  	        break;
  	    }
  	    continue;
  	}
  	else
  	{
  		j = (int) i;
  		if(!j)
  		    j++;
  	}
          while (j > 0) 
          {
  	    int cxl, cxr;
  
              ptsOut->y = (y) + yTrans;
  
  	    cxl = ICEIL(xl);
  	    cxr = ICEIL(xr);
              /* reverse the edges if necessary */
              if (xl < xr) 
              {
                  *(width++) = cxr - cxl;
                  (ptsOut++)->x = cxl + xTrans;
              }
              else 
              {
                  *(width++) = cxl - cxr;
                  (ptsOut++)->x = cxr + xTrans;
              }
              y++;
  
              /* increment down the edges */
  	    xl += ml;
  	    xr += mr;
  	    j--;
          }
      }  while (y <= ymax);
  
      /* Finally, fill the spans we've collected */
      (*pgc->ops->FillSpans)(dst, pgc, 
  		      ptsOut-FirstPoint, FirstPoint, FirstWidth, 1);
      xfree(Marked);
      xfree(FirstWidth);
      xfree(FirstPoint);
  }
  
  
  /* Find the index of the point with the smallest y.also return the
   * smallest and largest y */
  static
  int
  GetFPolyYBounds(
      SppPointPtr			pts,
      int 			n,
      double			yFtrans,
      int 			*by,
      int				*ty)
  {
      SppPointPtr			ptMin;
      double 			ymin, ymax;
      SppPointPtr			ptsStart = pts;
  
      ptMin = pts;
      ymin = ymax = (pts++)->y;
  
      while (--n > 0) {
          if (pts->y < ymin)
  	{
              ptMin = pts;
              ymin = pts->y;
          }
  	if(pts->y > ymax)
              ymax = pts->y;
  
          pts++;
      }
  
      *by = ICEIL(ymin + yFtrans);
      *ty = ICEIL(ymax + yFtrans - 1);
      return(ptMin-ptsStart);
  }
  