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: 2012-06-02 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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