1 /* -*- Mode: c; tab-width: 8; c-basic-offset: 4; indent-tabs-mode: t; -*- */
2 /* cairo - a vector graphics library with display and print output
3 *
4 * Copyright © 2002 University of Southern California
5 * Copyright © 2013 Intel Corporation
6 *
7 * This library is free software; you can redistribute it and/or
8 * modify it either under the terms of the GNU Lesser General Public
9 * License version 2.1 as published by the Free Software Foundation
10 * (the "LGPL") or, at your option, under the terms of the Mozilla
11 * Public License Version 1.1 (the "MPL"). If you do not alter this
12 * notice, a recipient may use your version of this file under either
13 * the MPL or the LGPL.
14 *
15 * You should have received a copy of the LGPL along with this library
16 * in the file COPYING-LGPL-2.1; if not, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 * You should have received a copy of the MPL along with this library
19 * in the file COPYING-MPL-1.1
20 *
21 * The contents of this file are subject to the Mozilla Public License
22 * Version 1.1 (the "License"); you may not use this file except in
23 * compliance with the License. You may obtain a copy of the License at
24 * http://www.mozilla.org/MPL/
25 *
26 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
27 * OF ANY KIND, either express or implied. See the LGPL or the MPL for
28 * the specific language governing rights and limitations.
29 *
30 * The Original Code is the cairo graphics library.
31 *
32 * The Initial Developer of the Original Code is University of Southern
33 * California.
34 *
35 * Contributor(s):
36 * Carl D. Worth <cworth@cworth.org>
37 * Chris Wilson <chris@chris-wilson.co.uk>
38 */
39
40 #include "cairoint.h"
41
42 #include "cairo-box-inline.h"
43 #include "cairo-path-fixed-private.h"
44 #include "cairo-slope-private.h"
45 #include "cairo-stroke-dash-private.h"
46 #include "cairo-traps-private.h"
47
48 #include <float.h>
49
50 struct stroker {
51 const cairo_stroke_style_t *style;
52
53 const cairo_matrix_t *ctm;
54 const cairo_matrix_t *ctm_inverse;
55 double spline_cusp_tolerance;
56 double half_line_width;
57 double tolerance;
58 double ctm_determinant;
59 cairo_bool_t ctm_det_positive;
60 cairo_line_join_t line_join;
61
62 cairo_traps_t *traps;
63
64 cairo_pen_t pen;
65
66 cairo_point_t first_point;
67
68 cairo_bool_t has_initial_sub_path;
69
70 cairo_bool_t has_current_face;
71 cairo_stroke_face_t current_face;
72
73 cairo_bool_t has_first_face;
74 cairo_stroke_face_t first_face;
75
76 cairo_stroker_dash_t dash;
77
78 cairo_bool_t has_bounds;
79 cairo_box_t tight_bounds;
80 cairo_box_t line_bounds;
81 cairo_box_t join_bounds;
82 };
83
84 static cairo_status_t
stroker_init(struct stroker * stroker,const cairo_path_fixed_t * path,const cairo_stroke_style_t * style,const cairo_matrix_t * ctm,const cairo_matrix_t * ctm_inverse,double tolerance,cairo_traps_t * traps)85 stroker_init (struct stroker *stroker,
86 const cairo_path_fixed_t *path,
87 const cairo_stroke_style_t *style,
88 const cairo_matrix_t *ctm,
89 const cairo_matrix_t *ctm_inverse,
90 double tolerance,
91 cairo_traps_t *traps)
92 {
93 cairo_status_t status;
94
95 stroker->style = style;
96 stroker->ctm = ctm;
97 stroker->ctm_inverse = NULL;
98 if (! _cairo_matrix_is_identity (ctm_inverse))
99 stroker->ctm_inverse = ctm_inverse;
100 stroker->line_join = style->line_join;
101 stroker->half_line_width = style->line_width / 2.0;
102 stroker->tolerance = tolerance;
103 stroker->traps = traps;
104
105 /* To test whether we need to join two segments of a spline using
106 * a round-join or a bevel-join, we can inspect the angle between the
107 * two segments. If the difference between the chord distance
108 * (half-line-width times the cosine of the bisection angle) and the
109 * half-line-width itself is greater than tolerance then we need to
110 * inject a point.
111 */
112 stroker->spline_cusp_tolerance = 1 - tolerance / stroker->half_line_width;
113 stroker->spline_cusp_tolerance *= stroker->spline_cusp_tolerance;
114 stroker->spline_cusp_tolerance *= 2;
115 stroker->spline_cusp_tolerance -= 1;
116
117 stroker->ctm_determinant = _cairo_matrix_compute_determinant (stroker->ctm);
118 stroker->ctm_det_positive = stroker->ctm_determinant >= 0.0;
119
120 status = _cairo_pen_init (&stroker->pen,
121 stroker->half_line_width,
122 tolerance, ctm);
123 if (unlikely (status))
124 return status;
125
126 stroker->has_current_face = FALSE;
127 stroker->has_first_face = FALSE;
128 stroker->has_initial_sub_path = FALSE;
129
130 _cairo_stroker_dash_init (&stroker->dash, style);
131
132 stroker->has_bounds = traps->num_limits;
133 if (stroker->has_bounds) {
134 /* Extend the bounds in each direction to account for the maximum area
135 * we might generate trapezoids, to capture line segments that are outside
136 * of the bounds but which might generate rendering that's within bounds.
137 */
138 double dx, dy;
139 cairo_fixed_t fdx, fdy;
140
141 stroker->tight_bounds = traps->bounds;
142
143 _cairo_stroke_style_max_distance_from_path (stroker->style, path,
144 stroker->ctm, &dx, &dy);
145
146 _cairo_stroke_style_max_line_distance_from_path (stroker->style, path,
147 stroker->ctm, &dx, &dy);
148
149 fdx = _cairo_fixed_from_double (dx);
150 fdy = _cairo_fixed_from_double (dy);
151
152 stroker->line_bounds = stroker->tight_bounds;
153 stroker->line_bounds.p1.x -= fdx;
154 stroker->line_bounds.p2.x += fdx;
155 stroker->line_bounds.p1.y -= fdy;
156 stroker->line_bounds.p2.y += fdy;
157
158 _cairo_stroke_style_max_join_distance_from_path (stroker->style, path,
159 stroker->ctm, &dx, &dy);
160
161 fdx = _cairo_fixed_from_double (dx);
162 fdy = _cairo_fixed_from_double (dy);
163
164 stroker->join_bounds = stroker->tight_bounds;
165 stroker->join_bounds.p1.x -= fdx;
166 stroker->join_bounds.p2.x += fdx;
167 stroker->join_bounds.p1.y -= fdy;
168 stroker->join_bounds.p2.y += fdy;
169 }
170
171 return CAIRO_STATUS_SUCCESS;
172 }
173
174 static void
stroker_fini(struct stroker * stroker)175 stroker_fini (struct stroker *stroker)
176 {
177 _cairo_pen_fini (&stroker->pen);
178 }
179
180 static void
translate_point(cairo_point_t * point,cairo_point_t * offset)181 translate_point (cairo_point_t *point, cairo_point_t *offset)
182 {
183 point->x += offset->x;
184 point->y += offset->y;
185 }
186
187 static int
join_is_clockwise(const cairo_stroke_face_t * in,const cairo_stroke_face_t * out)188 join_is_clockwise (const cairo_stroke_face_t *in,
189 const cairo_stroke_face_t *out)
190 {
191 return _cairo_slope_compare (&in->dev_vector, &out->dev_vector) < 0;
192 }
193
194 static int
slope_compare_sgn(double dx1,double dy1,double dx2,double dy2)195 slope_compare_sgn (double dx1, double dy1, double dx2, double dy2)
196 {
197 double c = dx1 * dy2 - dx2 * dy1;
198 if (c > 0) return 1;
199 if (c < 0) return -1;
200 return 0;
201 }
202
203 static cairo_bool_t
stroker_intersects_join(const struct stroker * stroker,const cairo_point_t * in,const cairo_point_t * out)204 stroker_intersects_join (const struct stroker *stroker,
205 const cairo_point_t *in,
206 const cairo_point_t *out)
207 {
208 cairo_line_t segment;
209
210 if (! stroker->has_bounds)
211 return TRUE;
212
213 segment.p1 = *in;
214 segment.p2 = *out;
215 return _cairo_box_intersects_line_segment (&stroker->join_bounds, &segment);
216 }
217
218 static void
join(struct stroker * stroker,cairo_stroke_face_t * in,cairo_stroke_face_t * out)219 join (struct stroker *stroker,
220 cairo_stroke_face_t *in,
221 cairo_stroke_face_t *out)
222 {
223 int clockwise = join_is_clockwise (out, in);
224 cairo_point_t *inpt, *outpt;
225
226 if (in->cw.x == out->cw.x &&
227 in->cw.y == out->cw.y &&
228 in->ccw.x == out->ccw.x &&
229 in->ccw.y == out->ccw.y)
230 {
231 return;
232 }
233
234 if (clockwise) {
235 inpt = &in->ccw;
236 outpt = &out->ccw;
237 } else {
238 inpt = &in->cw;
239 outpt = &out->cw;
240 }
241
242 if (! stroker_intersects_join (stroker, inpt, outpt))
243 return;
244
245 switch (stroker->line_join) {
246 case CAIRO_LINE_JOIN_ROUND:
247 /* construct a fan around the common midpoint */
248 if ((in->dev_slope.x * out->dev_slope.x +
249 in->dev_slope.y * out->dev_slope.y) < stroker->spline_cusp_tolerance)
250 {
251 int start, stop;
252 cairo_point_t tri[3], edges[4];
253 cairo_pen_t *pen = &stroker->pen;
254
255 edges[0] = in->cw;
256 edges[1] = in->ccw;
257 tri[0] = in->point;
258 tri[1] = *inpt;
259 if (clockwise) {
260 _cairo_pen_find_active_ccw_vertices (pen,
261 &in->dev_vector, &out->dev_vector,
262 &start, &stop);
263 while (start != stop) {
264 tri[2] = in->point;
265 translate_point (&tri[2], &pen->vertices[start].point);
266 edges[2] = in->point;
267 edges[3] = tri[2];
268 _cairo_traps_tessellate_triangle_with_edges (stroker->traps,
269 tri, edges);
270 tri[1] = tri[2];
271 edges[0] = edges[2];
272 edges[1] = edges[3];
273
274 if (start-- == 0)
275 start += pen->num_vertices;
276 }
277 } else {
278 _cairo_pen_find_active_cw_vertices (pen,
279 &in->dev_vector, &out->dev_vector,
280 &start, &stop);
281 while (start != stop) {
282 tri[2] = in->point;
283 translate_point (&tri[2], &pen->vertices[start].point);
284 edges[2] = in->point;
285 edges[3] = tri[2];
286 _cairo_traps_tessellate_triangle_with_edges (stroker->traps,
287 tri, edges);
288 tri[1] = tri[2];
289 edges[0] = edges[2];
290 edges[1] = edges[3];
291
292 if (++start == pen->num_vertices)
293 start = 0;
294 }
295 }
296 tri[2] = *outpt;
297 edges[2] = out->cw;
298 edges[3] = out->ccw;
299 _cairo_traps_tessellate_triangle_with_edges (stroker->traps,
300 tri, edges);
301 } else {
302 cairo_point_t t[] = { { in->point.x, in->point.y}, { inpt->x, inpt->y }, { outpt->x, outpt->y } };
303 cairo_point_t e[] = { { in->cw.x, in->cw.y}, { in->ccw.x, in->ccw.y },
304 { out->cw.x, out->cw.y}, { out->ccw.x, out->ccw.y } };
305 _cairo_traps_tessellate_triangle_with_edges (stroker->traps, t, e);
306 }
307 break;
308
309 case CAIRO_LINE_JOIN_MITER:
310 default: {
311 /* dot product of incoming slope vector with outgoing slope vector */
312 double in_dot_out = (-in->usr_vector.x * out->usr_vector.x +
313 -in->usr_vector.y * out->usr_vector.y);
314 double ml = stroker->style->miter_limit;
315
316 /* Check the miter limit -- lines meeting at an acute angle
317 * can generate long miters, the limit converts them to bevel
318 *
319 * Consider the miter join formed when two line segments
320 * meet at an angle psi:
321 *
322 * /.\
323 * /. .\
324 * /./ \.\
325 * /./psi\.\
326 *
327 * We can zoom in on the right half of that to see:
328 *
329 * |\
330 * | \ psi/2
331 * | \
332 * | \
333 * | \
334 * | \
335 * miter \
336 * length \
337 * | \
338 * | .\
339 * | . \
340 * |. line \
341 * \ width \
342 * \ \
343 *
344 *
345 * The right triangle in that figure, (the line-width side is
346 * shown faintly with three '.' characters), gives us the
347 * following expression relating miter length, angle and line
348 * width:
349 *
350 * 1 /sin (psi/2) = miter_length / line_width
351 *
352 * The right-hand side of this relationship is the same ratio
353 * in which the miter limit (ml) is expressed. We want to know
354 * when the miter length is within the miter limit. That is
355 * when the following condition holds:
356 *
357 * 1/sin(psi/2) <= ml
358 * 1 <= ml sin(psi/2)
359 * 1 <= ml² sin²(psi/2)
360 * 2 <= ml² 2 sin²(psi/2)
361 * 2·sin²(psi/2) = 1-cos(psi)
362 * 2 <= ml² (1-cos(psi))
363 *
364 * in · out = |in| |out| cos (psi)
365 *
366 * in and out are both unit vectors, so:
367 *
368 * in · out = cos (psi)
369 *
370 * 2 <= ml² (1 - in · out)
371 *
372 */
373 if (2 <= ml * ml * (1 - in_dot_out)) {
374 double x1, y1, x2, y2;
375 double mx, my;
376 double dx1, dx2, dy1, dy2;
377 cairo_point_t outer;
378 cairo_point_t quad[4];
379 double ix, iy;
380 double fdx1, fdy1, fdx2, fdy2;
381 double mdx, mdy;
382
383 /*
384 * we've got the points already transformed to device
385 * space, but need to do some computation with them and
386 * also need to transform the slope from user space to
387 * device space
388 */
389 /* outer point of incoming line face */
390 x1 = _cairo_fixed_to_double (inpt->x);
391 y1 = _cairo_fixed_to_double (inpt->y);
392 dx1 = in->usr_vector.x;
393 dy1 = in->usr_vector.y;
394 cairo_matrix_transform_distance (stroker->ctm, &dx1, &dy1);
395
396 /* outer point of outgoing line face */
397 x2 = _cairo_fixed_to_double (outpt->x);
398 y2 = _cairo_fixed_to_double (outpt->y);
399 dx2 = out->usr_vector.x;
400 dy2 = out->usr_vector.y;
401 cairo_matrix_transform_distance (stroker->ctm, &dx2, &dy2);
402
403 /*
404 * Compute the location of the outer corner of the miter.
405 * That's pretty easy -- just the intersection of the two
406 * outer edges. We've got slopes and points on each
407 * of those edges. Compute my directly, then compute
408 * mx by using the edge with the larger dy; that avoids
409 * dividing by values close to zero.
410 */
411 my = (((x2 - x1) * dy1 * dy2 - y2 * dx2 * dy1 + y1 * dx1 * dy2) /
412 (dx1 * dy2 - dx2 * dy1));
413 if (fabs (dy1) >= fabs (dy2))
414 mx = (my - y1) * dx1 / dy1 + x1;
415 else
416 mx = (my - y2) * dx2 / dy2 + x2;
417
418 /*
419 * When the two outer edges are nearly parallel, slight
420 * perturbations in the position of the outer points of the lines
421 * caused by representing them in fixed point form can cause the
422 * intersection point of the miter to move a large amount. If
423 * that moves the miter intersection from between the two faces,
424 * then draw a bevel instead.
425 */
426
427 ix = _cairo_fixed_to_double (in->point.x);
428 iy = _cairo_fixed_to_double (in->point.y);
429
430 /* slope of one face */
431 fdx1 = x1 - ix; fdy1 = y1 - iy;
432
433 /* slope of the other face */
434 fdx2 = x2 - ix; fdy2 = y2 - iy;
435
436 /* slope from the intersection to the miter point */
437 mdx = mx - ix; mdy = my - iy;
438
439 /*
440 * Make sure the miter point line lies between the two
441 * faces by comparing the slopes
442 */
443 if (slope_compare_sgn (fdx1, fdy1, mdx, mdy) !=
444 slope_compare_sgn (fdx2, fdy2, mdx, mdy))
445 {
446 /*
447 * Draw the quadrilateral
448 */
449 outer.x = _cairo_fixed_from_double (mx);
450 outer.y = _cairo_fixed_from_double (my);
451
452 quad[0] = in->point;
453 quad[1] = *inpt;
454 quad[2] = outer;
455 quad[3] = *outpt;
456
457 _cairo_traps_tessellate_convex_quad (stroker->traps, quad);
458 break;
459 }
460 }
461 }
462 /* fall through ... */
463 case CAIRO_LINE_JOIN_BEVEL: {
464 cairo_point_t t[] = { { in->point.x, in->point.y }, { inpt->x, inpt->y }, { outpt->x, outpt->y } };
465 cairo_point_t e[] = { { in->cw.x, in->cw.y }, { in->ccw.x, in->ccw.y },
466 { out->cw.x, out->cw.y }, { out->ccw.x, out->ccw.y } };
467 _cairo_traps_tessellate_triangle_with_edges (stroker->traps, t, e);
468 break;
469 }
470 }
471 }
472
473 static void
add_cap(struct stroker * stroker,cairo_stroke_face_t * f)474 add_cap (struct stroker *stroker, cairo_stroke_face_t *f)
475 {
476 switch (stroker->style->line_cap) {
477 case CAIRO_LINE_CAP_ROUND: {
478 int start, stop;
479 cairo_slope_t in_slope, out_slope;
480 cairo_point_t tri[3], edges[4];
481 cairo_pen_t *pen = &stroker->pen;
482
483 in_slope = f->dev_vector;
484 out_slope.dx = -in_slope.dx;
485 out_slope.dy = -in_slope.dy;
486 _cairo_pen_find_active_cw_vertices (pen, &in_slope, &out_slope,
487 &start, &stop);
488 edges[0] = f->cw;
489 edges[1] = f->ccw;
490 tri[0] = f->point;
491 tri[1] = f->cw;
492 while (start != stop) {
493 tri[2] = f->point;
494 translate_point (&tri[2], &pen->vertices[start].point);
495 edges[2] = f->point;
496 edges[3] = tri[2];
497 _cairo_traps_tessellate_triangle_with_edges (stroker->traps,
498 tri, edges);
499
500 tri[1] = tri[2];
501 edges[0] = edges[2];
502 edges[1] = edges[3];
503 if (++start == pen->num_vertices)
504 start = 0;
505 }
506 tri[2] = f->ccw;
507 edges[2] = f->cw;
508 edges[3] = f->ccw;
509 _cairo_traps_tessellate_triangle_with_edges (stroker->traps,
510 tri, edges);
511 break;
512 }
513
514 case CAIRO_LINE_CAP_SQUARE: {
515 double dx, dy;
516 cairo_slope_t fvector;
517 cairo_point_t quad[4];
518
519 dx = f->usr_vector.x;
520 dy = f->usr_vector.y;
521 dx *= stroker->half_line_width;
522 dy *= stroker->half_line_width;
523 cairo_matrix_transform_distance (stroker->ctm, &dx, &dy);
524 fvector.dx = _cairo_fixed_from_double (dx);
525 fvector.dy = _cairo_fixed_from_double (dy);
526
527 quad[0] = f->cw;
528 quad[1].x = f->cw.x + fvector.dx;
529 quad[1].y = f->cw.y + fvector.dy;
530 quad[2].x = f->ccw.x + fvector.dx;
531 quad[2].y = f->ccw.y + fvector.dy;
532 quad[3] = f->ccw;
533
534 _cairo_traps_tessellate_convex_quad (stroker->traps, quad);
535 break;
536 }
537
538 case CAIRO_LINE_CAP_BUTT:
539 default:
540 break;
541 }
542 }
543
544 static void
add_leading_cap(struct stroker * stroker,cairo_stroke_face_t * face)545 add_leading_cap (struct stroker *stroker,
546 cairo_stroke_face_t *face)
547 {
548 cairo_stroke_face_t reversed;
549 cairo_point_t t;
550
551 reversed = *face;
552
553 /* The initial cap needs an outward facing vector. Reverse everything */
554 reversed.usr_vector.x = -reversed.usr_vector.x;
555 reversed.usr_vector.y = -reversed.usr_vector.y;
556 reversed.dev_vector.dx = -reversed.dev_vector.dx;
557 reversed.dev_vector.dy = -reversed.dev_vector.dy;
558 t = reversed.cw;
559 reversed.cw = reversed.ccw;
560 reversed.ccw = t;
561
562 add_cap (stroker, &reversed);
563 }
564
565 static void
add_trailing_cap(struct stroker * stroker,cairo_stroke_face_t * face)566 add_trailing_cap (struct stroker *stroker, cairo_stroke_face_t *face)
567 {
568 add_cap (stroker, face);
569 }
570
571 static inline double
normalize_slope(double * dx,double * dy)572 normalize_slope (double *dx, double *dy)
573 {
574 double dx0 = *dx, dy0 = *dy;
575
576 if (dx0 == 0.0 && dy0 == 0.0)
577 return 0;
578
579 if (dx0 == 0.0) {
580 *dx = 0.0;
581 if (dy0 > 0.0) {
582 *dy = 1.0;
583 return dy0;
584 } else {
585 *dy = -1.0;
586 return -dy0;
587 }
588 } else if (dy0 == 0.0) {
589 *dy = 0.0;
590 if (dx0 > 0.0) {
591 *dx = 1.0;
592 return dx0;
593 } else {
594 *dx = -1.0;
595 return -dx0;
596 }
597 } else {
598 double mag = hypot (dx0, dy0);
599 *dx = dx0 / mag;
600 *dy = dy0 / mag;
601 return mag;
602 }
603 }
604
605 static void
compute_face(const cairo_point_t * point,const cairo_slope_t * dev_slope,struct stroker * stroker,cairo_stroke_face_t * face)606 compute_face (const cairo_point_t *point,
607 const cairo_slope_t *dev_slope,
608 struct stroker *stroker,
609 cairo_stroke_face_t *face)
610 {
611 double face_dx, face_dy;
612 cairo_point_t offset_ccw, offset_cw;
613 double slope_dx, slope_dy;
614
615 slope_dx = _cairo_fixed_to_double (dev_slope->dx);
616 slope_dy = _cairo_fixed_to_double (dev_slope->dy);
617 face->length = normalize_slope (&slope_dx, &slope_dy);
618 face->dev_slope.x = slope_dx;
619 face->dev_slope.y = slope_dy;
620
621 /*
622 * rotate to get a line_width/2 vector along the face, note that
623 * the vector must be rotated the right direction in device space,
624 * but by 90° in user space. So, the rotation depends on
625 * whether the ctm reflects or not, and that can be determined
626 * by looking at the determinant of the matrix.
627 */
628 if (stroker->ctm_inverse) {
629 cairo_matrix_transform_distance (stroker->ctm_inverse, &slope_dx, &slope_dy);
630 normalize_slope (&slope_dx, &slope_dy);
631
632 if (stroker->ctm_det_positive) {
633 face_dx = - slope_dy * stroker->half_line_width;
634 face_dy = slope_dx * stroker->half_line_width;
635 } else {
636 face_dx = slope_dy * stroker->half_line_width;
637 face_dy = - slope_dx * stroker->half_line_width;
638 }
639
640 /* back to device space */
641 cairo_matrix_transform_distance (stroker->ctm, &face_dx, &face_dy);
642 } else {
643 face_dx = - slope_dy * stroker->half_line_width;
644 face_dy = slope_dx * stroker->half_line_width;
645 }
646
647 offset_ccw.x = _cairo_fixed_from_double (face_dx);
648 offset_ccw.y = _cairo_fixed_from_double (face_dy);
649 offset_cw.x = -offset_ccw.x;
650 offset_cw.y = -offset_ccw.y;
651
652 face->ccw = *point;
653 translate_point (&face->ccw, &offset_ccw);
654
655 face->point = *point;
656
657 face->cw = *point;
658 translate_point (&face->cw, &offset_cw);
659
660 face->usr_vector.x = slope_dx;
661 face->usr_vector.y = slope_dy;
662
663 face->dev_vector = *dev_slope;
664 }
665
666 static void
add_caps(struct stroker * stroker)667 add_caps (struct stroker *stroker)
668 {
669 /* check for a degenerative sub_path */
670 if (stroker->has_initial_sub_path &&
671 !stroker->has_first_face &&
672 !stroker->has_current_face &&
673 stroker->style->line_cap == CAIRO_LINE_CAP_ROUND)
674 {
675 /* pick an arbitrary slope to use */
676 cairo_slope_t slope = { CAIRO_FIXED_ONE, 0 };
677 cairo_stroke_face_t face;
678
679 /* arbitrarily choose first_point
680 * first_point and current_point should be the same */
681 compute_face (&stroker->first_point, &slope, stroker, &face);
682
683 add_leading_cap (stroker, &face);
684 add_trailing_cap (stroker, &face);
685 }
686
687 if (stroker->has_first_face)
688 add_leading_cap (stroker, &stroker->first_face);
689
690 if (stroker->has_current_face)
691 add_trailing_cap (stroker, &stroker->current_face);
692 }
693
694 static cairo_bool_t
stroker_intersects_edge(const struct stroker * stroker,const cairo_stroke_face_t * start,const cairo_stroke_face_t * end)695 stroker_intersects_edge (const struct stroker *stroker,
696 const cairo_stroke_face_t *start,
697 const cairo_stroke_face_t *end)
698 {
699 cairo_box_t box;
700
701 if (! stroker->has_bounds)
702 return TRUE;
703
704 if (_cairo_box_contains_point (&stroker->tight_bounds, &start->cw))
705 return TRUE;
706 box.p2 = box.p1 = start->cw;
707
708 if (_cairo_box_contains_point (&stroker->tight_bounds, &start->ccw))
709 return TRUE;
710 _cairo_box_add_point (&box, &start->ccw);
711
712 if (_cairo_box_contains_point (&stroker->tight_bounds, &end->cw))
713 return TRUE;
714 _cairo_box_add_point (&box, &end->cw);
715
716 if (_cairo_box_contains_point (&stroker->tight_bounds, &end->ccw))
717 return TRUE;
718 _cairo_box_add_point (&box, &end->ccw);
719
720 return (box.p2.x > stroker->tight_bounds.p1.x &&
721 box.p1.x < stroker->tight_bounds.p2.x &&
722 box.p2.y > stroker->tight_bounds.p1.y &&
723 box.p1.y < stroker->tight_bounds.p2.y);
724 }
725
726 static void
add_sub_edge(struct stroker * stroker,const cairo_point_t * p1,const cairo_point_t * p2,const cairo_slope_t * dev_slope,cairo_stroke_face_t * start,cairo_stroke_face_t * end)727 add_sub_edge (struct stroker *stroker,
728 const cairo_point_t *p1, const cairo_point_t *p2,
729 const cairo_slope_t *dev_slope,
730 cairo_stroke_face_t *start, cairo_stroke_face_t *end)
731 {
732 cairo_point_t rectangle[4];
733
734 compute_face (p1, dev_slope, stroker, start);
735
736 *end = *start;
737 end->point = *p2;
738 rectangle[0].x = p2->x - p1->x;
739 rectangle[0].y = p2->y - p1->y;
740 translate_point (&end->ccw, &rectangle[0]);
741 translate_point (&end->cw, &rectangle[0]);
742
743 if (p1->x == p2->x && p1->y == p2->y)
744 return;
745
746 if (! stroker_intersects_edge (stroker, start, end))
747 return;
748
749 rectangle[0] = start->cw;
750 rectangle[1] = start->ccw;
751 rectangle[2] = end->ccw;
752 rectangle[3] = end->cw;
753
754 _cairo_traps_tessellate_convex_quad (stroker->traps, rectangle);
755 }
756
757 static cairo_status_t
move_to(void * closure,const cairo_point_t * point)758 move_to (void *closure, const cairo_point_t *point)
759 {
760 struct stroker *stroker = closure;
761
762 /* Cap the start and end of the previous sub path as needed */
763 add_caps (stroker);
764
765 stroker->first_point = *point;
766 stroker->current_face.point = *point;
767
768 stroker->has_first_face = FALSE;
769 stroker->has_current_face = FALSE;
770 stroker->has_initial_sub_path = FALSE;
771
772 return CAIRO_STATUS_SUCCESS;
773 }
774
775 static cairo_status_t
move_to_dashed(void * closure,const cairo_point_t * point)776 move_to_dashed (void *closure, const cairo_point_t *point)
777 {
778 /* reset the dash pattern for new sub paths */
779 struct stroker *stroker = closure;
780
781 _cairo_stroker_dash_start (&stroker->dash);
782 return move_to (closure, point);
783 }
784
785 static cairo_status_t
line_to(void * closure,const cairo_point_t * point)786 line_to (void *closure, const cairo_point_t *point)
787 {
788 struct stroker *stroker = closure;
789 cairo_stroke_face_t start, end;
790 const cairo_point_t *p1 = &stroker->current_face.point;
791 const cairo_point_t *p2 = point;
792 cairo_slope_t dev_slope;
793
794 stroker->has_initial_sub_path = TRUE;
795
796 if (p1->x == p2->x && p1->y == p2->y)
797 return CAIRO_STATUS_SUCCESS;
798
799 _cairo_slope_init (&dev_slope, p1, p2);
800 add_sub_edge (stroker, p1, p2, &dev_slope, &start, &end);
801
802 if (stroker->has_current_face) {
803 /* Join with final face from previous segment */
804 join (stroker, &stroker->current_face, &start);
805 } else if (!stroker->has_first_face) {
806 /* Save sub path's first face in case needed for closing join */
807 stroker->first_face = start;
808 stroker->has_first_face = TRUE;
809 }
810 stroker->current_face = end;
811 stroker->has_current_face = TRUE;
812
813 return CAIRO_STATUS_SUCCESS;
814 }
815
816 /*
817 * Dashed lines. Cap each dash end, join around turns when on
818 */
819 static cairo_status_t
line_to_dashed(void * closure,const cairo_point_t * point)820 line_to_dashed (void *closure, const cairo_point_t *point)
821 {
822 struct stroker *stroker = closure;
823 double mag, remain, step_length = 0;
824 double slope_dx, slope_dy;
825 double dx2, dy2;
826 cairo_stroke_face_t sub_start, sub_end;
827 const cairo_point_t *p1 = &stroker->current_face.point;
828 const cairo_point_t *p2 = point;
829 cairo_slope_t dev_slope;
830 cairo_line_t segment;
831 cairo_bool_t fully_in_bounds;
832
833 stroker->has_initial_sub_path = stroker->dash.dash_starts_on;
834
835 if (p1->x == p2->x && p1->y == p2->y)
836 return CAIRO_STATUS_SUCCESS;
837
838 fully_in_bounds = TRUE;
839 if (stroker->has_bounds &&
840 (! _cairo_box_contains_point (&stroker->join_bounds, p1) ||
841 ! _cairo_box_contains_point (&stroker->join_bounds, p2)))
842 {
843 fully_in_bounds = FALSE;
844 }
845
846 _cairo_slope_init (&dev_slope, p1, p2);
847
848 slope_dx = _cairo_fixed_to_double (p2->x - p1->x);
849 slope_dy = _cairo_fixed_to_double (p2->y - p1->y);
850
851 if (stroker->ctm_inverse)
852 cairo_matrix_transform_distance (stroker->ctm_inverse, &slope_dx, &slope_dy);
853 mag = normalize_slope (&slope_dx, &slope_dy);
854 if (mag <= DBL_EPSILON)
855 return CAIRO_STATUS_SUCCESS;
856
857 remain = mag;
858 segment.p1 = *p1;
859 while (remain) {
860 step_length = MIN (stroker->dash.dash_remain, remain);
861 remain -= step_length;
862 dx2 = slope_dx * (mag - remain);
863 dy2 = slope_dy * (mag - remain);
864 cairo_matrix_transform_distance (stroker->ctm, &dx2, &dy2);
865 segment.p2.x = _cairo_fixed_from_double (dx2) + p1->x;
866 segment.p2.y = _cairo_fixed_from_double (dy2) + p1->y;
867
868 if (stroker->dash.dash_on &&
869 (fully_in_bounds ||
870 (! stroker->has_first_face && stroker->dash.dash_starts_on) ||
871 _cairo_box_intersects_line_segment (&stroker->join_bounds, &segment)))
872 {
873 add_sub_edge (stroker,
874 &segment.p1, &segment.p2,
875 &dev_slope,
876 &sub_start, &sub_end);
877
878 if (stroker->has_current_face) {
879 /* Join with final face from previous segment */
880 join (stroker, &stroker->current_face, &sub_start);
881
882 stroker->has_current_face = FALSE;
883 } else if (! stroker->has_first_face && stroker->dash.dash_starts_on) {
884 /* Save sub path's first face in case needed for closing join */
885 stroker->first_face = sub_start;
886 stroker->has_first_face = TRUE;
887 } else {
888 /* Cap dash start if not connecting to a previous segment */
889 add_leading_cap (stroker, &sub_start);
890 }
891
892 if (remain) {
893 /* Cap dash end if not at end of segment */
894 add_trailing_cap (stroker, &sub_end);
895 } else {
896 stroker->current_face = sub_end;
897 stroker->has_current_face = TRUE;
898 }
899 } else {
900 if (stroker->has_current_face) {
901 /* Cap final face from previous segment */
902 add_trailing_cap (stroker, &stroker->current_face);
903
904 stroker->has_current_face = FALSE;
905 }
906 }
907
908 _cairo_stroker_dash_step (&stroker->dash, step_length);
909 segment.p1 = segment.p2;
910 }
911
912 if (stroker->dash.dash_on && ! stroker->has_current_face) {
913 /* This segment ends on a transition to dash_on, compute a new face
914 * and add cap for the beginning of the next dash_on step.
915 *
916 * Note: this will create a degenerate cap if this is not the last line
917 * in the path. Whether this behaviour is desirable or not is debatable.
918 * On one side these degenerate caps can not be reproduced with regular
919 * path stroking.
920 * On the other hand, Acroread 7 also produces the degenerate caps.
921 */
922 compute_face (point, &dev_slope, stroker, &stroker->current_face);
923
924 add_leading_cap (stroker, &stroker->current_face);
925
926 stroker->has_current_face = TRUE;
927 } else
928 stroker->current_face.point = *point;
929
930 return CAIRO_STATUS_SUCCESS;
931 }
932
933 static cairo_status_t
spline_to(void * closure,const cairo_point_t * point,const cairo_slope_t * tangent)934 spline_to (void *closure,
935 const cairo_point_t *point,
936 const cairo_slope_t *tangent)
937 {
938 struct stroker *stroker = closure;
939 cairo_stroke_face_t face;
940
941 if ((tangent->dx | tangent->dy) == 0) {
942 cairo_point_t t;
943
944 face = stroker->current_face;
945
946 face.usr_vector.x = -face.usr_vector.x;
947 face.usr_vector.y = -face.usr_vector.y;
948 face.dev_slope.x = -face.dev_slope.x;
949 face.dev_slope.y = -face.dev_slope.y;
950 face.dev_vector.dx = -face.dev_vector.dx;
951 face.dev_vector.dy = -face.dev_vector.dy;
952
953 t = face.cw;
954 face.cw = face.ccw;
955 face.ccw = t;
956
957 join (stroker, &stroker->current_face, &face);
958 } else {
959 cairo_point_t rectangle[4];
960
961 compute_face (&stroker->current_face.point, tangent, stroker, &face);
962 join (stroker, &stroker->current_face, &face);
963
964 rectangle[0] = face.cw;
965 rectangle[1] = face.ccw;
966
967 rectangle[2].x = point->x - face.point.x;
968 rectangle[2].y = point->y - face.point.y;
969 face.point = *point;
970 translate_point (&face.ccw, &rectangle[2]);
971 translate_point (&face.cw, &rectangle[2]);
972
973 rectangle[2] = face.ccw;
974 rectangle[3] = face.cw;
975
976 _cairo_traps_tessellate_convex_quad (stroker->traps, rectangle);
977 }
978
979 stroker->current_face = face;
980
981 return CAIRO_STATUS_SUCCESS;
982 }
983
984 static cairo_status_t
curve_to(void * closure,const cairo_point_t * b,const cairo_point_t * c,const cairo_point_t * d)985 curve_to (void *closure,
986 const cairo_point_t *b,
987 const cairo_point_t *c,
988 const cairo_point_t *d)
989 {
990 struct stroker *stroker = closure;
991 cairo_line_join_t line_join_save;
992 cairo_spline_t spline;
993 cairo_stroke_face_t face;
994 cairo_status_t status;
995
996 if (stroker->has_bounds &&
997 ! _cairo_spline_intersects (&stroker->current_face.point, b, c, d,
998 &stroker->line_bounds))
999 return line_to (closure, d);
1000
1001 if (! _cairo_spline_init (&spline, spline_to, stroker,
1002 &stroker->current_face.point, b, c, d))
1003 return line_to (closure, d);
1004
1005 compute_face (&stroker->current_face.point, &spline.initial_slope,
1006 stroker, &face);
1007
1008 if (stroker->has_current_face) {
1009 /* Join with final face from previous segment */
1010 join (stroker, &stroker->current_face, &face);
1011 } else {
1012 if (! stroker->has_first_face) {
1013 /* Save sub path's first face in case needed for closing join */
1014 stroker->first_face = face;
1015 stroker->has_first_face = TRUE;
1016 }
1017 stroker->has_current_face = TRUE;
1018 }
1019 stroker->current_face = face;
1020
1021 /* Temporarily modify the stroker to use round joins to guarantee
1022 * smooth stroked curves. */
1023 line_join_save = stroker->line_join;
1024 stroker->line_join = CAIRO_LINE_JOIN_ROUND;
1025
1026 status = _cairo_spline_decompose (&spline, stroker->tolerance);
1027
1028 stroker->line_join = line_join_save;
1029
1030 return status;
1031 }
1032
1033 static cairo_status_t
curve_to_dashed(void * closure,const cairo_point_t * b,const cairo_point_t * c,const cairo_point_t * d)1034 curve_to_dashed (void *closure,
1035 const cairo_point_t *b,
1036 const cairo_point_t *c,
1037 const cairo_point_t *d)
1038 {
1039 struct stroker *stroker = closure;
1040 cairo_spline_t spline;
1041 cairo_line_join_t line_join_save;
1042 cairo_spline_add_point_func_t func;
1043 cairo_status_t status;
1044
1045 func = (cairo_spline_add_point_func_t)line_to_dashed;
1046
1047 if (stroker->has_bounds &&
1048 ! _cairo_spline_intersects (&stroker->current_face.point, b, c, d,
1049 &stroker->line_bounds))
1050 return func (closure, d, NULL);
1051
1052 if (! _cairo_spline_init (&spline, func, stroker,
1053 &stroker->current_face.point, b, c, d))
1054 return func (closure, d, NULL);
1055
1056 /* Temporarily modify the stroker to use round joins to guarantee
1057 * smooth stroked curves. */
1058 line_join_save = stroker->line_join;
1059 stroker->line_join = CAIRO_LINE_JOIN_ROUND;
1060
1061 status = _cairo_spline_decompose (&spline, stroker->tolerance);
1062
1063 stroker->line_join = line_join_save;
1064
1065 return status;
1066 }
1067
1068 static cairo_status_t
_close_path(struct stroker * stroker)1069 _close_path (struct stroker *stroker)
1070 {
1071 if (stroker->has_first_face && stroker->has_current_face) {
1072 /* Join first and final faces of sub path */
1073 join (stroker, &stroker->current_face, &stroker->first_face);
1074 } else {
1075 /* Cap the start and end of the sub path as needed */
1076 add_caps (stroker);
1077 }
1078
1079 stroker->has_initial_sub_path = FALSE;
1080 stroker->has_first_face = FALSE;
1081 stroker->has_current_face = FALSE;
1082 return CAIRO_STATUS_SUCCESS;
1083 }
1084
1085 static cairo_status_t
close_path(void * closure)1086 close_path (void *closure)
1087 {
1088 struct stroker *stroker = closure;
1089 cairo_status_t status;
1090
1091 status = line_to (stroker, &stroker->first_point);
1092 if (unlikely (status))
1093 return status;
1094
1095 return _close_path (stroker);
1096 }
1097
1098 static cairo_status_t
close_path_dashed(void * closure)1099 close_path_dashed (void *closure)
1100 {
1101 struct stroker *stroker = closure;
1102 cairo_status_t status;
1103
1104 status = line_to_dashed (stroker, &stroker->first_point);
1105 if (unlikely (status))
1106 return status;
1107
1108 return _close_path (stroker);
1109 }
1110
1111 cairo_int_status_t
_cairo_path_fixed_stroke_to_traps(const cairo_path_fixed_t * path,const cairo_stroke_style_t * style,const cairo_matrix_t * ctm,const cairo_matrix_t * ctm_inverse,double tolerance,cairo_traps_t * traps)1112 _cairo_path_fixed_stroke_to_traps (const cairo_path_fixed_t *path,
1113 const cairo_stroke_style_t *style,
1114 const cairo_matrix_t *ctm,
1115 const cairo_matrix_t *ctm_inverse,
1116 double tolerance,
1117 cairo_traps_t *traps)
1118 {
1119 struct stroker stroker;
1120 cairo_status_t status;
1121
1122 status = stroker_init (&stroker, path, style,
1123 ctm, ctm_inverse, tolerance,
1124 traps);
1125 if (unlikely (status))
1126 return status;
1127
1128 if (stroker.dash.dashed)
1129 status = _cairo_path_fixed_interpret (path,
1130 move_to_dashed,
1131 line_to_dashed,
1132 curve_to_dashed,
1133 close_path_dashed,
1134 &stroker);
1135 else
1136 status = _cairo_path_fixed_interpret (path,
1137 move_to,
1138 line_to,
1139 curve_to,
1140 close_path,
1141 &stroker);
1142 assert(status == CAIRO_STATUS_SUCCESS);
1143 add_caps (&stroker);
1144
1145 stroker_fini (&stroker);
1146
1147 return traps->status;
1148 }
1149