1 /* CPML - Cairo Path Manipulation Library
2 * Copyright (C) 2008,2009,2010 Nicola Fontana <ntd at entidi.it>
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.
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.
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.
22 * SECTION:cpml-segment
23 * @Section_Id:CpmlSegment
25 * @short_description: Contiguous segment that can be a fragment
26 * or a whole cairo path
28 * A segment is a single contiguous line got from a cairo path. The
29 * CPML library relies on one assumption to let the data be independent
30 * from the current point (and thus from the cairo context): any segment
31 * MUST be preceded by at least one #CPML_MOVE primitive.
32 * This means a valid segment in cairo could be rejected by CPML.
34 * #CpmlSegment provides an unobtrusive way to access a cairo path.
35 * This means #CpmlSegment itsself does not hold any coordinates but
36 * instead a bunch of pointers to the original #cairo_path_t struct:
37 * modifying data throught this struct also changes the original path.
39 * Every #CpmlPath struct can contain more than one segment: the CPML
40 * library provides iteration APIs to browse the segments of a path.
41 * Use cpml_segment_reset() to reset the iterator at the start of the
42 * cairo path (will point the first segment) and cpml_segment_next()
43 * to get the next segment. Getting the previous segment is not provided
44 * as the underlying cairo struct is not accessible in reverse order.
46 * When initialized, #CpmlSegment yet refers to the first segment so
47 * the initial reset is not required.
53 * This is another name for the #cairo_path_t type. Although phisically
54 * they are the same struct, #CpmlPath conceptually embodies an important
55 * difference: it is a cairo path that can embed #CPML_ARC primitives.
56 * This is not a native cairo primitive and having two different data
57 * types is a good way to make clear when a function expect or not
58 * embedded arc-to primitives.
63 * @path: the source #CpmlPath struct
64 * @data: the data points of the segment; the first primitive
65 * will always be a #CPML_MOVE
66 * @num_data: size of @data
68 * This is an unobtrusive struct to identify a segment inside a
69 * cairo path. Unobtrusive means that the real coordinates are
70 * still stored in @path: CpmlSegment only provides a way to
75 #include "cpml-internal.h"
76 #include "cpml-extents.h"
77 #include "cpml-segment.h"
78 #include "cpml-primitive.h"
79 #include "cpml-line.h"
80 #include "cpml-curve.h"
83 static cairo_bool_t
normalize (CpmlSegment
*segment
);
84 static cairo_bool_t
ensure_one_leading_move (CpmlSegment
*segment
);
85 static cairo_bool_t
reshape (CpmlSegment
*segment
);
89 * cpml_segment_from_cairo:
90 * @segment: a #CpmlSegment
91 * @path: the source #CpmlPath
93 * Builds a CpmlSegment from a #CpmlPath structure. This operation
94 * involves stripping the duplicate #CPML_MOVE primitives at the
95 * start of the path and setting <structfield>num_data</structfield>
96 * field to the end of the contiguous line, that is when another
97 * #CPML_MOVE primitive is found or at the end of the path.
98 * A pointer to the source cairo path is kept though.
100 * This function will fail if @path is null, empty or if its
101 * <structfield>status</structfield> member is not %CAIRO_STATUS_SUCCESS.
102 * Also, the first primitive must be a #CPML_MOVE, so no
103 * dependency on the cairo context is needed.
105 * Returns: 1 on success, 0 on errors
108 cpml_segment_from_cairo(CpmlSegment
*segment
, CpmlPath
*path
)
110 /* The cairo path should be defined and in a perfect state */
111 if (path
== NULL
|| path
->num_data
== 0 ||
112 path
->status
!= CAIRO_STATUS_SUCCESS
)
115 segment
->path
= path
;
116 segment
->data
= path
->data
;
117 segment
->num_data
= path
->num_data
;
119 return normalize(segment
);
124 * @segment: a #CpmlSegment
125 * @src: the source segment to copy
127 * Makes a shallow copy of @src into @segment.
130 cpml_segment_copy(CpmlSegment
*segment
, const CpmlSegment
*src
)
132 memcpy(segment
, src
, sizeof(CpmlSegment
));
136 * cpml_path_is_empty:
137 * @cpml_path: a #CpmlPath (or a #cairo_path_t) pointer
139 * Checks if @cpml_path is empty. An invalid path is considered empty.
141 * Returns: %1 if the path is empty or invalid, %0 otherwise
145 * cpml_segment_reset:
146 * @segment: a #CpmlSegment
148 * Modifies @segment to point to the first segment of the source cairo path.
151 cpml_segment_reset(CpmlSegment
*segment
)
153 segment
->data
= segment
->path
->data
;
154 segment
->num_data
= segment
->path
->num_data
;
160 * @segment: a #CpmlSegment
162 * Modifies @segment to point to the next segment of the source cairo path.
164 * Returns: 1 on success, 0 if no next segment found or errors
167 cpml_segment_next(CpmlSegment
*segment
)
169 cairo_path_data_t
*new_data
;
170 const cairo_path_data_t
*end_data
;
172 new_data
= segment
->data
+ segment
->num_data
;
173 end_data
= segment
->path
->data
+ segment
->path
->num_data
;
175 if (new_data
>= end_data
)
178 segment
->data
= new_data
;
179 segment
->num_data
= end_data
- new_data
;
181 return normalize(segment
);
185 * cpml_segment_get_length:
186 * @segment: a #CpmlSegment
188 * Gets the whole length of @segment.
190 * Returns: the requested length
193 cpml_segment_get_length(const CpmlSegment
*segment
)
195 CpmlPrimitive primitive
;
198 cpml_primitive_from_segment(&primitive
, (CpmlSegment
*) segment
);
202 length
+= cpml_primitive_get_length(&primitive
);
203 } while (cpml_primitive_next(&primitive
));
209 * cpml_segment_put_extents:
210 * @segment: a #CpmlSegment
211 * @extents: where to store the extents
213 * Gets the whole extents of @segment.
216 cpml_segment_put_extents(const CpmlSegment
*segment
, CpmlExtents
*extents
)
218 CpmlPrimitive primitive
;
219 CpmlExtents primitive_extents
;
221 extents
->is_defined
= 0;
223 cpml_primitive_from_segment(&primitive
, (CpmlSegment
*) segment
);
226 cpml_primitive_put_extents(&primitive
, &primitive_extents
);
227 cpml_extents_add(extents
, &primitive_extents
);
228 } while (cpml_primitive_next(&primitive
));
232 * cpml_segment_put_pair_at:
233 * @segment: a #CpmlSegment
234 * @pos: the position value
235 * @pair: the destination #CpmlPair
237 * Gets the coordinates of the point lying on @segment at position
238 * @pos. @pos is an homogeneous factor where %0 is the start point,
239 * %1 the end point, %0.5 the mid point and so on.
240 * The relation %0 < @pos < %1 should be satisfied, although some
241 * cases accept value outside this range.
244 * <title>TODO</title>
246 * <listitem>The actual implementation returns only the start and end points,
247 * that is only when @pos is %0 or %1.</listitem>
252 cpml_segment_put_pair_at(const CpmlSegment
*segment
, double pos
,
255 CpmlPrimitive primitive
;
257 cpml_primitive_from_segment(&primitive
, (CpmlSegment
*) segment
);
259 /* Handle the common cases: start and end points */
261 return cpml_primitive_put_pair_at(&primitive
, 0, pair
);
264 while (cpml_primitive_next(&primitive
))
266 return cpml_primitive_put_pair_at(&primitive
, 1, pair
);
271 * cpml_segment_put_vector_at:
272 * @segment: a #CpmlSegment
273 * @pos: the position value
274 * @vector: the destination #CpmlVector
276 * Gets the steepness of the point lying on @segment at position
277 * @pos. @pos is an homogeneous factor where %0 is the start point,
278 * %1 the end point, %0.5 the mid point and so on.
279 * The relation %0 < @pos < %1 should be satisfied, although some
280 * cases accept value outside this range.
283 * <title>TODO</title>
285 * <listitem>The actual implementation returns only the start and end
286 * steepness, that is only when @pos is %0 or %1.</listitem>
291 cpml_segment_put_vector_at(const CpmlSegment
*segment
, double pos
,
294 CpmlPrimitive primitive
;
296 cpml_primitive_from_segment(&primitive
, (CpmlSegment
*) segment
);
298 /* Handle the common cases: start and end points */
300 cpml_primitive_put_vector_at(&primitive
, 0, vector
);
305 while (cpml_primitive_next(&primitive
))
307 cpml_primitive_put_vector_at(&primitive
, 1, vector
);
313 * cpml_segment_put_intersections:
314 * @segment: the first #CpmlSegment
315 * @segment2: the second #CpmlSegment
316 * @n_dest: maximum number of intersections to return
317 * @dest: the destination vector of #CpmlPair
319 * Computes the intersections between @segment and @segment2 and
320 * returns the found points in @dest. If the intersections are more
321 * than @n_dest, only the first @n_dest pairs are stored in @dest.
323 * To get the job done, the primitives of @segment are sequentially
324 * scanned for intersections with any primitive in @segment2. This
325 * means @segment has a higher precedence over @segment2.
327 * Returns: the number of intersections found
330 cpml_segment_put_intersections(const CpmlSegment
*segment
,
331 const CpmlSegment
*segment2
,
332 size_t n_dest
, CpmlPair
*dest
)
334 CpmlPrimitive portion
;
335 size_t partial
, total
;
337 cpml_primitive_from_segment(&portion
, (CpmlSegment
*) segment
);
341 partial
= cpml_primitive_put_intersections_with_segment(&portion
,
346 } while (total
< n_dest
&& cpml_primitive_next(&portion
));
352 * cpml_segment_offset:
353 * @segment: a #CpmlSegment
354 * @offset: the offset distance
356 * Offsets a segment of the specified amount, that is builds a "parallel"
357 * segment at the @offset distance from the original one and returns the
358 * result by replacing the original @segment.
361 * <title>TODO</title>
363 * <listitem>Closed path are not yet managed: an elegant solution is not
364 * so obvious: use cpml_close_offset() when available.</listitem>
365 * <listitem>Degenerated primitives, such as lines of length 0, are not
366 * managed properly.</listitem>
371 cpml_segment_offset(CpmlSegment
*segment
, double offset
)
373 CpmlPrimitive primitive
;
374 CpmlPrimitive last_primitive
;
375 cairo_path_data_t org
, old_end
;
376 cairo_bool_t first_cycle
;
378 cpml_primitive_from_segment(&primitive
, segment
);
384 primitive
.org
= &org
;
387 old_end
= *cpml_primitive_get_point(&primitive
, -1);
388 cpml_primitive_offset(&primitive
, offset
);
391 cpml_primitive_join(&last_primitive
, &primitive
);
392 primitive
.org
= cpml_primitive_get_point(&last_primitive
, -1);
395 cpml_primitive_copy(&last_primitive
, &primitive
);
397 } while (cpml_primitive_next(&primitive
));
401 * cpml_segment_transform:
402 * @segment: a #CpmlSegment
403 * @matrix: the matrix to be applied
405 * Applies @matrix on all the points of @segment.
408 cpml_segment_transform(CpmlSegment
*segment
, const cairo_matrix_t
*matrix
)
410 cairo_path_data_t
*data
;
411 int n
, n_point
, num_points
;
413 data
= segment
->data
;
415 for (n
= 0; n
< segment
->num_data
; n
+= num_points
) {
416 num_points
= data
->header
.length
;
418 for (n_point
= 1; n_point
< num_points
; ++n_point
) {
419 cairo_matrix_transform_point(matrix
, &data
->point
.x
, &data
->point
.y
);
426 * cpml_segment_reverse:
427 * @segment: a #CpmlSegment
429 * Reverses @segment in-place. The resulting rendering will be the same,
430 * but with the primitives generated in reverse order.
432 * It is assumed that @segment has yet been sanitized, that is returned
433 * by some CPML API function or it is a path yet conforming to the
434 * segment rules described by the cpml_segment_from_cairo() function.
437 cpml_segment_reverse(CpmlSegment
*segment
)
439 cairo_path_data_t
*data
, *dst_data
;
443 size_t n_points
, n_point
;
444 const cairo_path_data_t
*src_data
;
446 data_size
= sizeof(cairo_path_data_t
) * segment
->num_data
;
447 data
= malloc(data_size
);
448 end_x
= segment
->data
[1].point
.x
;
449 end_y
= segment
->data
[1].point
.y
;
451 n
= segment
->data
->header
.length
;
452 data
->header
.type
= CPML_MOVE
;
453 data
->header
.length
= n
;
455 while (n
< segment
->num_data
) {
456 src_data
= segment
->data
+ n
;
457 n_points
= cpml_primitive_type_get_n_points(src_data
->header
.type
);
458 length
= src_data
->header
.length
;
460 dst_data
= data
+ segment
->num_data
- n
+ data
->header
.length
;
461 dst_data
->header
.type
= src_data
->header
.type
;
462 dst_data
->header
.length
= length
;
464 for (n_point
= 1; n_point
< n_points
; ++n_point
) {
465 dst_data
[n_points
- n_point
].point
.x
= end_x
;
466 dst_data
[n_points
- n_point
].point
.y
= end_y
;
467 end_x
= src_data
[n_point
].point
.x
;
468 end_y
= src_data
[n_point
].point
.y
;
471 /* Copy also the embedded data, if any */
472 if (n_points
< length
) {
473 size_t size
= (length
- n_points
) * sizeof(cairo_path_data_t
);
474 memcpy(dst_data
+ n_points
, src_data
+ n_points
, size
);
478 data
[1].point
.x
= end_x
;
479 data
[1].point
.y
= end_y
;
480 memcpy(segment
->data
, data
, data_size
);
486 * cpml_segment_to_cairo:
487 * @segment: a #CpmlSegment
488 * @cr: the destination cairo context
490 * Appends the path of @segment to @cr. The segment is "flattened",
491 * that is #CPML_ARC primitives are approximated by one or more
492 * #CPML_CURVE using cpml_arc_to_cairo(). Check its documentation
493 * for further details.
496 cpml_segment_to_cairo(const CpmlSegment
*segment
, cairo_t
*cr
)
498 CpmlPrimitive primitive
;
500 cpml_primitive_from_segment(&primitive
, (CpmlSegment
*) segment
);
503 cpml_primitive_to_cairo(&primitive
, cr
);
504 } while (cpml_primitive_next(&primitive
));
509 * @segment: a #CpmlSegment
511 * Dumps the specified @segment to stdout. Useful for debugging purposes.
514 cpml_segment_dump(const CpmlSegment
*segment
)
516 CpmlPrimitive primitive
;
517 cairo_bool_t first_call
= 1;
519 cpml_primitive_from_segment(&primitive
, (CpmlSegment
*) segment
);
522 cpml_primitive_dump(&primitive
, first_call
);
524 } while (cpml_primitive_next(&primitive
));
530 * @segment: a #CpmlSegment
532 * Sanitizes @segment by calling ensure_one_leading_move() and reshape().
534 * Returns: 1 on success, 0 on no leading MOVE_TOs or on errors
537 normalize(CpmlSegment
*segment
)
539 if (!ensure_one_leading_move(segment
))
542 return reshape(segment
);
546 * ensure_one_leading_move:
547 * @segment: a #CpmlSegment
549 * Strips the leading #CPML_MOVE primitives, updating the
550 * <structname>CpmlSegment</structname> structure accordingly.
551 * One, and only one, #CPML_MOVE primitive is left.
553 * Returns: 1 on success, 0 on no leading MOVE_TOs or on empty path
556 ensure_one_leading_move(CpmlSegment
*segment
)
558 cairo_path_data_t
*new_data
;
559 int new_num_data
, move_length
;
561 /* Check for at least one move to */
562 if (segment
->data
->header
.type
!= CPML_MOVE
)
565 new_data
= segment
->data
;
566 new_num_data
= segment
->num_data
;
569 move_length
= new_data
->header
.length
;
571 /* Check for the end of cairo path data, that is when
572 * @segment is composed by only CPML_MOVE */
573 if (new_num_data
<= move_length
)
576 /* Check if this is the last CPML_MOVE */
577 if (new_data
[move_length
].header
.type
!= CPML_MOVE
)
580 new_data
+= move_length
;
581 new_num_data
-= move_length
;
584 segment
->data
= new_data
;
585 segment
->num_data
= new_num_data
;
592 * @segment: a #CpmlSegment
594 * Looks for the segment termination, that is the end of the underlying
595 * cairo path or a #CPML_MOVE operation. <structfield>num_data</structfield>
596 * field is modified to properly point to the end of @segment.
597 * @segment must have only one leading #CPML_MOVE and it is supposed
598 * to be non-empty, conditions yet imposed by the ensure_one_leading_move().
600 * This function also checks that all the components of @segment
601 * are valid primitives.
603 * Returns: 1 on success, 0 on invalid primitive found
606 reshape(CpmlSegment
*segment
)
608 const cairo_path_data_t
*data
;
609 int trailing_data
, new_num_data
, length
;
611 data
= segment
->data
;
613 trailing_data
= segment
->num_data
;
616 length
= data
->header
.length
;
617 new_num_data
+= length
;
618 trailing_data
-= length
;
621 /* Check for invalid data size */
622 if (trailing_data
< 0)
625 if (trailing_data
== 0 || data
->header
.type
== CPML_MOVE
)
628 /* Ensure that all the components are valid primitives */
629 if (cpml_primitive_type_get_n_points(data
->header
.type
) == 0)
633 segment
->num_data
= new_num_data
;