src/cpml/cpml-line.c

   1 /* CPML - Cairo Path Manipulation Library
   2  * Copyright (C) 2008,2009,2010,2011  Nicola Fontana <ntd at entidi.it>
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the
  16  * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17  * Boston, MA  02110-1301, USA.
  18  */
  19
  20 #include "cpml-internal.h"
  21 #include "cpml-extents.h"
  22 #include "cpml-segment.h"
  23 #include "cpml-primitive.h"
  24 #include "cpml-primitive-private.h"
  25
  26
  27 static double   get_length              (const CpmlPrimitive    *line);
  28 static void     put_extents             (const CpmlPrimitive    *line,
  29                                          CpmlExtents            *extents);
  30 static void     put_pair_at             (const CpmlPrimitive    *line,
  31                                          double                  pos,
  32                                          CpmlPair               *pair);
  33 static void     put_vector_at           (const CpmlPrimitive    *line,
  34                                          double                  pos,
  35                                          CpmlVector             *vector);
  36 static double   get_closest_pos         (const CpmlPrimitive    *line,
  37                                          const CpmlPair         *pair);
  38 static size_t   put_intersections       (const CpmlPrimitive    *line,
  39                                          const CpmlPrimitive    *primitive,
  40                                          size_t                  n_dest,
  41                                          CpmlPair               *dest);
  42 static void     offset                  (CpmlPrimitive          *line,
  43                                          double                  offset);
  44 static cairo_bool_t
  45                 intersection            (const CpmlPair         *p1_4,
  46                                          CpmlPair               *dest,
  47                                          double                 *get_factor);
  48
  49
  50 const _CpmlPrimitiveClass *
  51 _cpml_line_get_class(void)
  52 {
  53     static _CpmlPrimitiveClass *p_class = NULL;
  54
  55     if (p_class == NULL) {
  56         static _CpmlPrimitiveClass class_data = {
  57             "line to", 2,
  58             get_length,
  59             put_extents,
  60             put_pair_at,
  61             put_vector_at,
  62             get_closest_pos,
  63             put_intersections,
  64             offset,
  65             NULL
  66         };
  67         p_class = &class_data;
  68     }
  69
  70     return p_class;
  71 }
  72
  73 const _CpmlPrimitiveClass *
  74 _cpml_close_get_class(void)
  75 {
  76     static _CpmlPrimitiveClass *p_class = NULL;
  77
  78     if (p_class == NULL) {
  79         static _CpmlPrimitiveClass class_data = {
  80             "close", 2,
  81             get_length,
  82             put_extents,
  83             put_pair_at,
  84             put_vector_at,
  85             get_closest_pos,
  86             put_intersections,
  87             offset,
  88             NULL
  89         };
  90         p_class = &class_data;
  91     }
  92
  93     return p_class;
  94 }
  95
  96
  97 static double
  98 get_length(const CpmlPrimitive *line)
  99 {
 100     CpmlPair p1, p2;
 101
 102     cpml_pair_from_cairo(&p1, cpml_primitive_get_point(line, 0));
 103     cpml_pair_from_cairo(&p2, cpml_primitive_get_point(line, -1));
 104
 105     return cpml_pair_distance(&p1, &p2);
 106 }
 107
 108 static void
 109 put_extents(const CpmlPrimitive *line, CpmlExtents *extents)
 110 {
 111     CpmlPair p1, p2;
 112
 113     extents->is_defined = 0;
 114
 115     cpml_pair_from_cairo(&p1, cpml_primitive_get_point(line, 0));
 116     cpml_pair_from_cairo(&p2, cpml_primitive_get_point(line, -1));
 117
 118     cpml_extents_pair_add(extents, &p1);
 119     cpml_extents_pair_add(extents, &p2);
 120 }
 121
 122 static void
 123 put_pair_at(const CpmlPrimitive *line, double pos, CpmlPair *pair)
 124 {
 125     cairo_path_data_t *p1, *p2;
 126
 127     p1 = cpml_primitive_get_point(line, 0);
 128     p2 = cpml_primitive_get_point(line, -1);
 129
 130     pair->x = p1->point.x + (p2->point.x - p1->point.x) * pos;
 131     pair->y = p1->point.y + (p2->point.y - p1->point.y) * pos;
 132 }
 133
 134 static void
 135 put_vector_at(const CpmlPrimitive *line, double pos, CpmlVector *vector)
 136 {
 137     cairo_path_data_t *p1, *p2;
 138
 139     p1 = cpml_primitive_get_point(line, 0);
 140     p2 = cpml_primitive_get_point(line, -1);
 141
 142     vector->x = p2->point.x - p1->point.x;
 143     vector->y = p2->point.y - p1->point.y;
 144 }
 145
 146 static double
 147 get_closest_pos(const CpmlPrimitive *line, const CpmlPair *pair)
 148 {
 149     CpmlPair p1_4[4];
 150     CpmlVector normal;
 151     double pos;
 152
 153     cpml_pair_from_cairo(&p1_4[0], cpml_primitive_get_point(line, 0));
 154     cpml_pair_from_cairo(&p1_4[1], cpml_primitive_get_point(line, -1));
 155
 156     normal.x = p1_4[1].x - p1_4[2].x;
 157     normal.y = p1_4[1].y - p1_4[2].y;
 158     cpml_vector_normal(&normal);
 159
 160     cpml_pair_copy(&p1_4[2], pair);
 161
 162     p1_4[3].x = pair->x + normal.x;
 163     p1_4[3].y = pair->y + normal.y;
 164
 165     /* Ensure to return 0 if intersection() fails */
 166     pos = 0;
 167     intersection(p1_4, NULL, &pos);
 168
 169     /* Clamp the result to 0..1 */
 170     if (pos < 0)
 171         pos = 0;
 172     else if (pos > 1.)
 173         pos = 1.;
 174
 175     return pos;
 176 }
 177
 178 static size_t
 179 put_intersections(const CpmlPrimitive *line, const CpmlPrimitive *primitive,
 180                   size_t n_dest, CpmlPair *dest)
 181 {
 182     CpmlPair p1_4[4];
 183
 184     if (n_dest == 0)
 185         return 0;
 186
 187     cpml_pair_from_cairo(&p1_4[0], cpml_primitive_get_point(line, 0));
 188     cpml_pair_from_cairo(&p1_4[1], cpml_primitive_get_point(line, -1));
 189     cpml_pair_from_cairo(&p1_4[2], cpml_primitive_get_point(primitive, 0));
 190     cpml_pair_from_cairo(&p1_4[3], cpml_primitive_get_point(primitive, -1));
 191
 192     return intersection(p1_4, dest, NULL) ? 1 : 0;
 193 }
 194
 195 static void
 196 offset(CpmlPrimitive *line, double offset)
 197 {
 198     cairo_path_data_t *p1, *p2;
 199     CpmlVector normal;
 200
 201     p1 = cpml_primitive_get_point(line, 0);
 202     p2 = cpml_primitive_get_point(line, -1);
 203
 204     put_vector_at(line, 0, &normal);
 205     cpml_vector_normal(&normal);
 206     cpml_vector_set_length(&normal, offset);
 207
 208     p1->point.x += normal.x;
 209     p1->point.y += normal.y;
 210     p2->point.x += normal.x;
 211     p2->point.y += normal.y;
 212 }
 213
 214 static cairo_bool_t
 215 intersection(const CpmlPair *p1_4, CpmlPair *dest, double *get_factor)
 216 {
 217     CpmlVector v[2];
 218     double factor;
 219
 220     v[0].x = p1_4[1].x - p1_4[0].x;
 221     v[0].y = p1_4[1].y - p1_4[0].y;
 222     v[1].x = p1_4[3].x - p1_4[2].x;
 223     v[1].y = p1_4[3].y - p1_4[2].y;
 224     factor = v[0].x * v[1].y - v[0].y * v[1].x;
 225
 226     /* Check for equal slopes (the lines are parallel) */
 227     if (factor == 0)
 228         return 0;
 229
 230     factor = ((p1_4[0].y - p1_4[2].y) * v[1].x -
 231               (p1_4[0].x - p1_4[2].x) * v[1].y) / factor;
 232
 233     if (dest != NULL) {
 234         dest->x = p1_4[0].x + v[0].x * factor;
 235         dest->y = p1_4[0].y + v[0].y * factor;
 236     }
 237
 238     if (get_factor != NULL)
 239         *get_factor = factor;
 240
 241     return 1;
 242 }