LCOV - app.info - gfx/cairo/cairo/src/cairo-hull.c

LCOV - code coverage report
| Current view: | directory - gfx/cairo/cairo/src - cairo-hull.c (source / functions) |  | Found | Hit | Coverage |
| Test: | app.info | Lines: | 81 | 0 | 0.0 %
| Date: | 2012-07-07 | Functions: | 8 | 0 | 0.0 %

           1                 : /* cairo - a vector graphics library with display and print output
           2                 :  *
           3                 :  * Copyright © 2003 University of Southern California
           4                 :  *
           5                 :  * This library is free software; you can redistribute it and/or
           6                 :  * modify it either under the terms of the GNU Lesser General Public
           7                 :  * License version 2.1 as published by the Free Software Foundation
           8                 :  * (the "LGPL") or, at your option, under the terms of the Mozilla
           9                 :  * Public License Version 1.1 (the "MPL"). If you do not alter this
          10                 :  * notice, a recipient may use your version of this file under either
          11                 :  * the MPL or the LGPL.
          12                 :  *
          13                 :  * You should have received a copy of the LGPL along with this library
          14                 :  * in the file COPYING-LGPL-2.1; if not, write to the Free Software
          15                 :  * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA
          16                 :  * You should have received a copy of the MPL along with this library
          17                 :  * in the file COPYING-MPL-1.1
          18                 :  *
          19                 :  * The contents of this file are subject to the Mozilla Public License
          20                 :  * Version 1.1 (the "License"); you may not use this file except in
          21                 :  * compliance with the License. You may obtain a copy of the License at
          22                 :  * http://www.mozilla.org/MPL/
          23                 :  *
          24                 :  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
          25                 :  * OF ANY KIND, either express or implied. See the LGPL or the MPL for
          26                 :  * the specific language governing rights and limitations.
          27                 :  *
          28                 :  * The Original Code is the cairo graphics library.
          29                 :  *
          30                 :  * The Initial Developer of the Original Code is University of Southern
          31                 :  * California.
          32                 :  *
          33                 :  * Contributor(s):
          34                 :  *      Carl D. Worth <cworth@cworth.org>
          35                 :  */
          36                 :
          37                 : #include "cairoint.h"
          38                 :
          39                 : #include "cairo-error-private.h"
          40                 : #include "cairo-slope-private.h"
          41                 :
          42                 : typedef struct cairo_hull {
          43                 :     cairo_point_t point;
          44                 :     cairo_slope_t slope;
          45                 :     int discard;
          46                 :     int id;
          47                 : } cairo_hull_t;
          48                 :
          49                 : static void
          50               0 : _cairo_hull_init (cairo_hull_t                  *hull,
          51                 :                   cairo_pen_vertex_t            *vertices,
          52                 :                   int                            num_vertices)
          53                 : {
          54                 :     cairo_point_t *p, *extremum, tmp;
          55                 :     int i;
          56                 :
          57               0 :     extremum = &vertices[0].point;
          58               0 :     for (i = 1; i < num_vertices; i++) {
          59               0 :         p = &vertices[i].point;
          60               0 :         if (p->y < extremum->y || (p->y == extremum->y && p->x < extremum->x))
          61               0 :             extremum = p;
          62                 :     }
          63                 :     /* Put the extremal point at the beginning of the array */
          64               0 :     tmp = *extremum;
          65               0 :     *extremum = vertices[0].point;
          66               0 :     vertices[0].point = tmp;
          67                 :
          68               0 :     for (i = 0; i < num_vertices; i++) {
          69               0 :         hull[i].point = vertices[i].point;
          70               0 :         _cairo_slope_init (&hull[i].slope, &hull[0].point, &hull[i].point);
          71                 :
          72                 :         /* give each point a unique id for later comparison */
          73               0 :         hull[i].id = i;
          74                 :
          75                 :         /* Don't discard by default */
          76               0 :         hull[i].discard = 0;
          77                 :
          78                 :         /* Discard all points coincident with the extremal point */
          79               0 :         if (i != 0 && hull[i].slope.dx == 0 && hull[i].slope.dy == 0)
          80               0 :             hull[i].discard = 1;
          81                 :     }
          82               0 : }
          83                 :
          84                 : static inline cairo_int64_t
          85               0 : _slope_length (cairo_slope_t *slope)
          86                 : {
          87               0 :     return _cairo_int64_add (_cairo_int32x32_64_mul (slope->dx, slope->dx),
          88                 :                              _cairo_int32x32_64_mul (slope->dy, slope->dy));
          89                 : }
          90                 :
          91                 : static int
          92               0 : _cairo_hull_vertex_compare (const void *av, const void *bv)
          93                 : {
          94               0 :     cairo_hull_t *a = (cairo_hull_t *) av;
          95               0 :     cairo_hull_t *b = (cairo_hull_t *) bv;
          96                 :     int ret;
          97                 :
          98                 :     /* Some libraries are reported to actually compare identical
          99                 :      * pointers and require the result to be 0. This is the crazy world we
         100                 :      * have to live in.
         101                 :      */
         102               0 :     if (a == b)
         103               0 :         return 0;
         104                 :
         105               0 :     ret = _cairo_slope_compare (&a->slope, &b->slope);
         106                 :
         107                 :     /*
         108                 :      * In the case of two vertices with identical slope from the
         109                 :      * extremal point discard the nearer point.
         110                 :      */
         111               0 :     if (ret == 0) {
         112                 :         int cmp;
         113                 :
         114               0 :         cmp = _cairo_int64_cmp (_slope_length (&a->slope),
         115                 :                                 _slope_length (&b->slope));
         116                 :
         117                 :         /*
         118                 :          * Use the points' ids to ensure a well-defined ordering,
         119                 :          * and avoid setting discard on both points.
         120                 :          */
         121               0 :         if (cmp < 0 || (cmp == 0 && a->id < b->id)) {
         122               0 :             a->discard = 1;
         123               0 :             ret = -1;
         124                 :         } else {
         125               0 :             b->discard = 1;
         126               0 :             ret = 1;
         127                 :         }
         128                 :     }
         129                 :
         130               0 :     return ret;
         131                 : }
         132                 :
         133                 : static int
         134               0 : _cairo_hull_prev_valid (cairo_hull_t *hull, int num_hull, int index)
         135                 : {
         136                 :     /* hull[0] is always valid, and we never need to wraparound, (if
         137                 :      * we are passed an index of 0 here, then the calling loop is just
         138                 :      * about to terminate). */
         139               0 :     if (index == 0)
         140               0 :         return 0;
         141                 :
         142                 :     do {
         143               0 :         index--;
         144               0 :     } while (hull[index].discard);
         145                 :
         146               0 :     return index;
         147                 : }
         148                 :
         149                 : static int
         150               0 : _cairo_hull_next_valid (cairo_hull_t *hull, int num_hull, int index)
         151                 : {
         152                 :     do {
         153               0 :         index = (index + 1) % num_hull;
         154               0 :     } while (hull[index].discard);
         155                 :
         156               0 :     return index;
         157                 : }
         158                 :
         159                 : static void
         160               0 : _cairo_hull_eliminate_concave (cairo_hull_t *hull, int num_hull)
         161                 : {
         162                 :     int i, j, k;
         163                 :     cairo_slope_t slope_ij, slope_jk;
         164                 :
         165               0 :     i = 0;
         166               0 :     j = _cairo_hull_next_valid (hull, num_hull, i);
         167               0 :     k = _cairo_hull_next_valid (hull, num_hull, j);
         168                 :
         169                 :     do {
         170               0 :         _cairo_slope_init (&slope_ij, &hull[i].point, &hull[j].point);
         171               0 :         _cairo_slope_init (&slope_jk, &hull[j].point, &hull[k].point);
         172                 :
         173                 :         /* Is the angle formed by ij and jk concave? */
         174               0 :         if (_cairo_slope_compare (&slope_ij, &slope_jk) >= 0) {
         175               0 :             if (i == k)
         176               0 :                 return;
         177               0 :             hull[j].discard = 1;
         178               0 :             j = i;
         179               0 :             i = _cairo_hull_prev_valid (hull, num_hull, j);
         180                 :         } else {
         181               0 :             i = j;
         182               0 :             j = k;
         183               0 :             k = _cairo_hull_next_valid (hull, num_hull, j);
         184                 :         }
         185               0 :     } while (j != 0);
         186                 : }
         187                 :
         188                 : static void
         189               0 : _cairo_hull_to_pen (cairo_hull_t *hull, cairo_pen_vertex_t *vertices, int *num_vertices)
         190                 : {
         191               0 :     int i, j = 0;
         192                 :
         193               0 :     for (i = 0; i < *num_vertices; i++) {
         194               0 :         if (hull[i].discard)
         195               0 :             continue;
         196               0 :         vertices[j++].point = hull[i].point;
         197                 :     }
         198                 :
         199               0 :     *num_vertices = j;
         200               0 : }
         201                 :
         202                 : /* Given a set of vertices, compute the convex hull using the Graham
         203                 :    scan algorithm. */
         204                 : cairo_status_t
         205               0 : _cairo_hull_compute (cairo_pen_vertex_t *vertices, int *num_vertices)
         206                 : {
         207                 :     cairo_hull_t hull_stack[CAIRO_STACK_ARRAY_LENGTH (cairo_hull_t)];
         208                 :     cairo_hull_t *hull;
         209               0 :     int num_hull = *num_vertices;
         210                 :
         211                 :     if (CAIRO_INJECT_FAULT ())
         212                 :         return _cairo_error (CAIRO_STATUS_NO_MEMORY);
         213                 :
         214               0 :     if (num_hull > ARRAY_LENGTH (hull_stack)) {
         215               0 :         hull = _cairo_malloc_ab (num_hull, sizeof (cairo_hull_t));
         216               0 :         if (unlikely (hull == NULL))
         217               0 :             return _cairo_error (CAIRO_STATUS_NO_MEMORY);
         218                 :     } else {
         219               0 :         hull = hull_stack;
         220                 :     }
         221                 :
         222               0 :     _cairo_hull_init (hull, vertices, num_hull);
         223                 :
         224               0 :     qsort (hull + 1, num_hull - 1,
         225                 :            sizeof (cairo_hull_t), _cairo_hull_vertex_compare);
         226                 :
         227               0 :     _cairo_hull_eliminate_concave (hull, num_hull);
         228                 :
         229               0 :     _cairo_hull_to_pen (hull, vertices, num_vertices);
         230                 :
         231               0 :     if (hull != hull_stack)
         232               0 :         free (hull);
         233                 :
         234               0 :     return CAIRO_STATUS_SUCCESS;
         235                 : }

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