mi/mipolycon.c

   1 /***********************************************************
   2
   3 Copyright 1987, 1998  The Open Group
   4
   5 Permission to use, copy, modify, distribute, and sell this software and its
   6 documentation for any purpose is hereby granted without fee, provided that
   7 the above copyright notice appear in all copies and that both that
   8 copyright notice and this permission notice appear in supporting
   9 documentation.
  10
  11 The above copyright notice and this permission notice shall be included in
  12 all copies or substantial portions of the Software.
  13
  14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
  17 OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  18 AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  19 CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  20
  21 Except as contained in this notice, the name of The Open Group shall not be
  22 used in advertising or otherwise to promote the sale, use or other dealings
  23 in this Software without prior written authorization from The Open Group.
  24
  25 Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts.
  26
  27                         All Rights Reserved
  28
  29 Permission to use, copy, modify, and distribute this software and its
  30 documentation for any purpose and without fee is hereby granted,
  31 provided that the above copyright notice appear in all copies and that
  32 both that copyright notice and this permission notice appear in
  33 supporting documentation, and that the name of Digital not be
  34 used in advertising or publicity pertaining to distribution of the
  35 software without specific, written prior permission.
  36
  37 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
  38 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
  39 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
  40 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
  41 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
  42 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  43 SOFTWARE.
  44
  45 ******************************************************************/
  46
  47 #ifdef HAVE_DIX_CONFIG_H
  48 #include <dix-config.h>
  49 #endif
  50
  51 #include "gcstruct.h"
  52 #include "pixmap.h"
  53 #include "mi.h"
  54 #include "miscanfill.h"
  55
  56 static int getPolyYBounds(DDXPointPtr pts, int n, int *by, int *ty);
  57
  58 /*
  59  *     convexpoly.c
  60  *
  61  *     Written by Brian Kelleher; Dec. 1985.
  62  *
  63  *     Fill a convex polygon.  If the given polygon
  64  *     is not convex, then the result is undefined.
  65  *     The algorithm is to order the edges from smallest
  66  *     y to largest by partitioning the array into a left
  67  *     edge list and a right edge list.  The algorithm used
  68  *     to traverse each edge is an extension of Bresenham's
  69  *     line algorithm with y as the major axis.
  70  *     For a derivation of the algorithm, see the author of
  71  *     this code.
  72  */
  73 Bool
  74 miFillConvexPoly(DrawablePtr dst, GCPtr pgc, int count, /* number of points        */
  75                  DDXPointPtr ptsIn      /* the points              */
  76     )
  77 {
  78     int xl = 0, xr = 0;         /* x vals of left and right edges */
  79     int dl = 0, dr = 0;         /* decision variables             */
  80     int ml = 0, m1l = 0;        /* left edge slope and slope+1    */
  81     int mr = 0, m1r = 0;        /* right edge slope and slope+1   */
  82     int incr1l = 0, incr2l = 0; /* left edge error increments     */
  83     int incr1r = 0, incr2r = 0; /* right edge error increments    */
  84     int dy;                     /* delta y                        */
  85     int y;                      /* current scanline               */
  86     int left, right;            /* indices to first endpoints     */
  87     int i;                      /* loop counter                   */
  88     int nextleft, nextright;    /* indices to second endpoints    */
  89     DDXPointPtr ptsOut, FirstPoint;     /* output buffer               */
  90     int *width, *FirstWidth;    /* output buffer                  */
  91     int imin;                   /* index of smallest vertex (in y) */
  92     int ymin;                   /* y-extents of polygon            */
  93     int ymax;
  94
  95     /*
  96      *  find leftx, bottomy, rightx, topy, and the index
  97      *  of bottomy. Also translate the points.
  98      */
  99     imin = getPolyYBounds(ptsIn, count, &ymin, &ymax);
 100
 101     dy = ymax - ymin + 1;
 102     if ((count < 3) || (dy < 0))
 103         return TRUE;
 104     ptsOut = FirstPoint = malloc(sizeof(DDXPointRec) * dy);
 105     width = FirstWidth = malloc(sizeof(int) * dy);
 106     if (!FirstPoint || !FirstWidth) {
 107         free(FirstWidth);
 108         free(FirstPoint);
 109         return FALSE;
 110     }
 111
 112     nextleft = nextright = imin;
 113     y = ptsIn[nextleft].y;
 114
 115     /*
 116      *  loop through all edges of the polygon
 117      */
 118     do {
 119         /*
 120          *  add a left edge if we need to
 121          */
 122         if (ptsIn[nextleft].y == y) {
 123             left = nextleft;
 124
 125             /*
 126              *  find the next edge, considering the end
 127              *  conditions of the array.
 128              */
 129             nextleft++;
 130             if (nextleft >= count)
 131                 nextleft = 0;
 132
 133             /*
 134              *  now compute all of the random information
 135              *  needed to run the iterative algorithm.
 136              */
 137             BRESINITPGON(ptsIn[nextleft].y - ptsIn[left].y,
 138                          ptsIn[left].x, ptsIn[nextleft].x,
 139                          xl, dl, ml, m1l, incr1l, incr2l);
 140         }
 141
 142         /*
 143          *  add a right edge if we need to
 144          */
 145         if (ptsIn[nextright].y == y) {
 146             right = nextright;
 147
 148             /*
 149              *  find the next edge, considering the end
 150              *  conditions of the array.
 151              */
 152             nextright--;
 153             if (nextright < 0)
 154                 nextright = count - 1;
 155
 156             /*
 157              *  now compute all of the random information
 158              *  needed to run the iterative algorithm.
 159              */
 160             BRESINITPGON(ptsIn[nextright].y - ptsIn[right].y,
 161                          ptsIn[right].x, ptsIn[nextright].x,
 162                          xr, dr, mr, m1r, incr1r, incr2r);
 163         }
 164
 165         /*
 166          *  generate scans to fill while we still have
 167          *  a right edge as well as a left edge.
 168          */
 169         i = min(ptsIn[nextleft].y, ptsIn[nextright].y) - y;
 170         /* in case we're called with non-convex polygon */
 171         if (i < 0) {
 172             free(FirstWidth);
 173             free(FirstPoint);
 174             return TRUE;
 175         }
 176         while (i-- > 0) {
 177             ptsOut->y = y;
 178
 179             /*
 180              *  reverse the edges if necessary
 181              */
 182             if (xl < xr) {
 183                 *(width++) = xr - xl;
 184                 (ptsOut++)->x = xl;
 185             }
 186             else {
 187                 *(width++) = xl - xr;
 188                 (ptsOut++)->x = xr;
 189             }
 190             y++;
 191
 192             /* increment down the edges */
 193             BRESINCRPGON(dl, xl, ml, m1l, incr1l, incr2l);
 194             BRESINCRPGON(dr, xr, mr, m1r, incr1r, incr2r);
 195         }
 196     } while (y != ymax);
 197
 198     /*
 199      * Finally, fill the <remaining> spans
 200      */
 201     (*pgc->ops->FillSpans) (dst, pgc,
 202                             ptsOut - FirstPoint, FirstPoint, FirstWidth, 1);
 203     free(FirstWidth);
 204     free(FirstPoint);
 205     return TRUE;
 206 }
 207 \f
 208 /*
 209  *     Find the index of the point with the smallest y.
 210  */
 211 static int
 212 getPolyYBounds(DDXPointPtr pts, int n, int *by, int *ty)
 213 {
 214     DDXPointPtr ptMin;
 215     int ymin, ymax;
 216     DDXPointPtr ptsStart = pts;
 217
 218     ptMin = pts;
 219     ymin = ymax = (pts++)->y;
 220
 221     while (--n > 0) {
 222         if (pts->y < ymin) {
 223             ptMin = pts;
 224             ymin = pts->y;
 225         }
 226         if (pts->y > ymax)
 227             ymax = pts->y;
 228
 229         pts++;
 230     }
 231
 232     *by = ymin;
 233     *ty = ymax;
 234     return ptMin - ptsStart;
 235 }