1 /* Libart_LGPL - library of basic graphic primitives
2 * Copyright (C) 1999-2000 Raph Levien
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library 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 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 * Boston, MA 02111-1307, USA.
18 */
19
20 /* Apply a dash style to a vector path. */
21
22 #include "config.h"
23 #include "art_vpath_dash.h"
24
25 #include <math.h>
26 #include <stdlib.h>
27
28 #include "art_misc.h"
29
30 #include "art_vpath.h"
31
32
33 /* Return the length of the largest subpath within vpath */
34 static int
art_vpath_dash_max_subpath(const ArtVpath * vpath)35 art_vpath_dash_max_subpath (const ArtVpath *vpath)
36 {
37 int max_subpath;
38 int i;
39 int start;
40
41 max_subpath = 0;
42 start = 0;
43 for (i = 0; vpath[i].code != ART_END; i++)
44 {
45 if (vpath[i].code == ART_MOVETO || vpath[i].code == ART_MOVETO_OPEN)
46 {
47 if (i - start > max_subpath)
48 max_subpath = i - start;
49 start = i;
50 }
51 }
52 if (i - start > max_subpath)
53 max_subpath = i - start;
54
55 return max_subpath;
56 }
57
58 /**
59 * art_vpath_dash: Add dash style to vpath.
60 * @vpath: Original vpath.
61 * @dash: Dash style.
62 *
63 * Creates a new vpath that is the result of applying dash style @dash
64 * to @vpath.
65 *
66 * This implementation has two known flaws:
67 *
68 * First, it adds a spurious break at the beginning of the vpath. The
69 * only way I see to resolve this flaw is to run the state forward one
70 * dash break at the beginning, and fix up by looping back to the
71 * first dash break at the end. This is doable but of course adds some
72 * complexity.
73 *
74 * Second, it does not suppress output points that are within epsilon
75 * of each other.
76 *
77 * Return value: Newly created vpath.
78 **/
79 ArtVpath *
art_vpath_dash(const ArtVpath * vpath,const ArtVpathDash * dash)80 art_vpath_dash (const ArtVpath *vpath, const ArtVpathDash *dash)
81 {
82 int max_subpath;
83 double *dists;
84 ArtVpath *result;
85 int n_result, n_result_max;
86 int start, end;
87 int i;
88 double total_dist;
89
90 /* state while traversing dasharray - offset is offset of current dash
91 value, toggle is 0 for "off" and 1 for "on", and phase is the distance
92 in, >= 0, < dash->dash[offset]. */
93 int offset, toggle;
94 double phase;
95
96 /* initial values */
97 int offset_init, toggle_init;
98 double phase_init;
99
100 max_subpath = art_vpath_dash_max_subpath (vpath);
101 dists = art_new (double, max_subpath);
102
103 n_result = 0;
104 n_result_max = 16;
105 result = art_new (ArtVpath, n_result_max);
106
107 /* determine initial values of dash state */
108 toggle_init = 1;
109 offset_init = 0;
110 phase_init = dash->offset;
111 while (phase_init >= dash->dash[offset_init])
112 {
113 toggle_init = !toggle_init;
114 phase_init -= dash->dash[offset_init];
115 offset_init++;
116 if (offset_init == dash->n_dash)
117 offset_init = 0;
118 }
119
120 for (start = 0; vpath[start].code != ART_END; start = end)
121 {
122 for (end = start + 1; vpath[end].code == ART_LINETO; end++);
123 /* subpath is [start..end) */
124 total_dist = 0;
125 for (i = start; i < end - 1; i++)
126 {
127 double dx, dy;
128
129 dx = vpath[i + 1].x - vpath[i].x;
130 dy = vpath[i + 1].y - vpath[i].y;
131 dists[i - start] = sqrt (dx * dx + dy * dy);
132 total_dist += dists[i - start];
133 }
134 if (total_dist <= dash->dash[offset_init] - phase_init)
135 {
136 /* subpath fits entirely within first dash */
137 if (toggle_init)
138 {
139 for (i = start; i < end; i++)
140 art_vpath_add_point (&result, &n_result, &n_result_max,
141 vpath[i].code, vpath[i].x, vpath[i].y);
142 }
143 }
144 else
145 {
146 /* subpath is composed of at least one dash - thus all
147 generated pieces are open */
148 double dist;
149
150 phase = phase_init;
151 offset = offset_init;
152 toggle = toggle_init;
153 dist = 0;
154 i = start;
155 if (toggle)
156 art_vpath_add_point (&result, &n_result, &n_result_max,
157 ART_MOVETO_OPEN, vpath[i].x, vpath[i].y);
158 while (i != end - 1)
159 {
160 if (dists[i - start] - dist > dash->dash[offset] - phase)
161 {
162 /* dash boundary is next */
163 double a;
164 double x, y;
165
166 dist += dash->dash[offset] - phase;
167 a = dist / dists[i - start];
168 x = vpath[i].x + a * (vpath[i + 1].x - vpath[i].x);
169 y = vpath[i].y + a * (vpath[i + 1].y - vpath[i].y);
170 art_vpath_add_point (&result, &n_result, &n_result_max,
171 toggle ? ART_LINETO : ART_MOVETO_OPEN,
172 x, y);
173 /* advance to next dash */
174 toggle = !toggle;
175 phase = 0;
176 offset++;
177 if (offset == dash->n_dash)
178 offset = 0;
179 }
180 else
181 {
182 /* end of line in vpath is next */
183 phase += dists[i - start] - dist;
184 i++;
185 dist = 0;
186 if (toggle)
187 art_vpath_add_point (&result, &n_result, &n_result_max,
188 ART_LINETO, vpath[i].x, vpath[i].y);
189 }
190 }
191 }
192 }
193
194 art_vpath_add_point (&result, &n_result, &n_result_max,
195 ART_END, 0, 0);
196
197 art_free (dists);
198
199 return result;
200 }
201