cpml/cpml-segment.c

   1 /* CPML - Cairo Path Manipulation Library
   2  * Copyright (C) 2008, 2009  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 /**
  21  * SECTION:segment
  22  * @title: CpmlSegment
  23  * @short_description: Contiguous lines
  24  *
  25  * A segment is a single contiguous line got from a cairo path.
  26  *
  27  * Every #cairo_path_t struct can contain more than one segment:
  28  * the CPML library provides iteration APIs to browse these segments.
  29  * The <structname>CpmlSegment</structname> struct internally keeps
  30  * a reference to the source #cairo_path_t so it can be used both
  31  * for getting segment data and browsing the segments (that is,
  32  * it is used also as an iterator).
  33  *
  34  * Use cpml_segment_reset() to reset the iterator at the start of the
  35  * cairo path (will point the first segment) and cpml_segment_next()
  36  * to get the next segment. When initialized,
  37  * <structname>CpmlSegment</structname> yet refers to the first
  38  * segment, so the initial reset is useless.
  39  *
  40  * Getting the previous segment is not provided, as the underlying
  41  * cairo struct is not accessible in reverse order.
  42  **/
  43
  44 /**
  45  * CpmlSegment:
  46  * @cairo_path: the source #cairo_path_t struct
  47  * @data: the segment data
  48  * @num_data: size of @data
  49  *
  50  * This is an unobtrusive struct to identify a segment inside a
  51  * cairo path. Unobtrusive means that the real coordinates are
  52  * still stored in @source: CpmlSegment only provides a way to
  53  * access the underlying cairo path.
  54  **/
  55
  56 #include "cpml-segment.h"
  57 #include "cpml-primitive.h"
  58 #include "cpml-line.h"
  59 #include "cpml-curve.h"
  60 #include "cpml-pair.h"
  61 #include "cpml-alloca.h"
  62
  63 #include <stdio.h>
  64 #include <string.h>
  65
  66 static cairo_bool_t     normalize               (CpmlSegment       *segment);
  67 static cairo_bool_t     ensure_one_move_to      (CpmlSegment       *segment);
  68 static void             reshape                 (CpmlSegment       *segment);
  69
  70
  71 /**
  72  * cpml_segment_from_cairo:
  73  * @segment: a #CpmlSegment
  74  * @cairo_path: the source #cairo_path_t
  75  *
  76  * Builds a CpmlSegment from a cairo_path_t structure. This operation
  77  * involves stripping the leading %CAIRO_PATH_MOVE_TO primitives and
  78  * setting the internal segment structure accordling. A pointer to the
  79  * source cairo path is kept.
  80  *
  81  * This function will fail if @cairo_path is null, empty or if its
  82  * <structfield>status</structfield> member is not %CAIRO_STATUS_SUCCESS.
  83  * Also, the first primitive must be a %CAIRO_PATH_MOVE_TO, so no
  84  * dependency on the cairo context is needed.
  85  *
  86  * Return value: 1 on success, 0 on errors
  87  **/
  88 cairo_bool_t
  89 cpml_segment_from_cairo(CpmlSegment *segment, cairo_path_t *cairo_path)
  90 {
  91     /* The cairo path should be defined and in perfect state */
  92     if (cairo_path == NULL || cairo_path->num_data == 0 ||
  93         cairo_path->status != CAIRO_STATUS_SUCCESS)
  94         return 0;
  95
  96     segment->cairo_path = cairo_path;
  97     segment->data = cairo_path->data;
  98     segment->num_data = cairo_path->num_data;
  99
 100     return normalize(segment);
 101 }
 102
 103 /**
 104  * cpml_segment_copy:
 105  * @segment: a #CpmlSegment
 106  * @src: the source segment to copy
 107  *
 108  * Makes a shallow copy of @src into @segment.
 109  *
 110  * Return value: @segment or %NULL on errors
 111  **/
 112 CpmlSegment *
 113 cpml_segment_copy(CpmlSegment *segment, const CpmlSegment *src)
 114 {
 115     if (segment == NULL || src == NULL)
 116         return NULL;
 117
 118     return memcpy(segment, src, sizeof(CpmlSegment));
 119 }
 120
 121
 122 /**
 123  * cpml_segment_reset:
 124  * @segment: a #CpmlSegment
 125  *
 126  * Modifies @segment to point to the first segment of the source cairo path.
 127  **/
 128 void
 129 cpml_segment_reset(CpmlSegment *segment)
 130 {
 131     segment->data = segment->cairo_path->data;
 132     segment->num_data = segment->cairo_path->num_data;
 133     normalize(segment);
 134 }
 135
 136 /**
 137  * cpml_segment_next:
 138  * @segment: a #CpmlSegment
 139  *
 140  * Modifies @segment to point to the next segment of the source cairo path.
 141  *
 142  * Return value: 1 on success, 0 if no next segment found or errors
 143  **/
 144 cairo_bool_t
 145 cpml_segment_next(CpmlSegment *segment)
 146 {
 147     int rest = segment->cairo_path->num_data - segment->num_data +
 148         segment->cairo_path->data - segment->data;
 149
 150     if (rest <= 0)
 151         return 0;
 152
 153     segment->data += segment->num_data;
 154     segment->num_data = rest;
 155
 156     return normalize(segment);
 157 }
 158
 159
 160 /**
 161  * cpml_segment_to_cairo:
 162  * @segment: a #CpmlSegment
 163  * @cr: the destination cairo context
 164  *
 165  * Appends the path of @segment to @cr using cairo_append_path().
 166  **/
 167 void
 168 cpml_segment_to_cairo(const CpmlSegment *segment, cairo_t *cr)
 169 {
 170     cairo_path_t path;
 171
 172     path.status = CAIRO_STATUS_SUCCESS;
 173     path.data = segment->data;
 174     path.num_data = segment->num_data;
 175
 176     cairo_append_path(cr, &path);
 177 }
 178
 179 /**
 180  * cpml_segment_dump:
 181  * @segment: a #CpmlSegment
 182  *
 183  * Dumps the specified @segment to stdout. Useful for debugging purposes.
 184  **/
 185 void
 186 cpml_segment_dump(const CpmlSegment *segment)
 187 {
 188     CpmlPrimitive primitive;
 189     cairo_bool_t first_call = 1;
 190
 191     cpml_primitive_from_segment(&primitive, (CpmlSegment *) segment);
 192
 193     do {
 194         cpml_primitive_dump(&primitive, first_call);
 195         first_call = 0;
 196     } while (cpml_primitive_next(&primitive));
 197 }
 198
 199
 200 /**
 201  * cpml_segment_reverse:
 202  * @segment: a #CpmlSegment
 203  *
 204  * Reverses @segment in-place. The resulting rendering will be the same,
 205  * but with the primitives generated in reverse order.
 206  **/
 207 void
 208 cpml_segment_reverse(CpmlSegment *segment)
 209 {
 210     cairo_path_data_t *data, *dst_data;
 211     size_t data_size;
 212     double end_x, end_y;
 213     int n, num_points, n_point;
 214     const cairo_path_data_t *src_data;
 215
 216     data_size = sizeof(cairo_path_data_t) * segment->num_data;
 217     data = cpml_alloca(data_size);
 218     end_x = segment->data[1].point.x;
 219     end_y = segment->data[1].point.y;
 220
 221     for (n = 2; n < segment->num_data; ++n) {
 222         src_data = segment->data + n;
 223         num_points = src_data->header.length;
 224
 225         dst_data = data + segment->num_data - n - num_points + 2;
 226         dst_data->header.type = src_data->header.type;
 227         dst_data->header.length = num_points;
 228
 229         for (n_point = 1; n_point < num_points; ++n_point) {
 230             dst_data[num_points - n_point].point.x = end_x;
 231             dst_data[num_points - n_point].point.y = end_y;
 232             end_x = src_data[n_point].point.x;
 233             end_y = src_data[n_point].point.y;
 234         }
 235
 236         n += n_point - 1;
 237     }
 238
 239     data[0].header.type = CAIRO_PATH_MOVE_TO;
 240     data[0].header.length = 2;
 241     data[1].point.x = end_x;
 242     data[1].point.y = end_y;
 243     memcpy(segment->data, data, data_size);
 244 }
 245
 246 /**
 247  * cpml_segment_transform:
 248  * @segment: a #CpmlSegment
 249  * @matrix: the matrix to be applied
 250  *
 251  * Applies @matrix on all the points of @segment.
 252  **/
 253 void
 254 cpml_segment_transform(CpmlSegment *segment, const cairo_matrix_t *matrix)
 255 {
 256     cairo_path_data_t *data;
 257     int n, n_point, num_points;
 258
 259     data = segment->data;
 260
 261     for (n = 0; n < segment->num_data; n += num_points) {
 262         num_points = data->header.length;
 263         ++data;
 264         for (n_point = 1; n_point < num_points; ++n_point) {
 265             cairo_matrix_transform_point(matrix, &data->point.x, &data->point.y);
 266             ++data;
 267         }
 268     }
 269 }
 270
 271 /**
 272  * cpml_segment_intersection:
 273  * @segment:  the first #CpmlSegment
 274  * @segment2: the second #CpmlSegment
 275  * @dest:     the destination vector of #CpmlPair
 276  * @max:      maximum number of intersections to return
 277  *
 278  * Computes the intersections between @segment and @segment2 and
 279  * returns the found points in @dest. If the intersections are more
 280  * than @max, only the first @max pairs are stored in @dest.
 281  *
 282  * To get the job done, the primitives of @segment are sequentially
 283  * scanned for intersections with any primitive in @segment2. This
 284  * means @segment has a higher precedence over @segment2.
 285  *
 286  * Return value: the number of intersections found
 287  **/
 288 int
 289 cpml_segment_intersection(const CpmlSegment *segment,
 290                           const CpmlSegment *segment2,
 291                           CpmlPair *dest, int max)
 292 {
 293     CpmlPrimitive portion;
 294     int partial, total;
 295
 296     cpml_primitive_from_segment(&portion, (CpmlSegment *) segment);
 297     total = 0;
 298
 299     do {
 300         partial = cpml_primitive_intersection_with_segment(&portion,
 301                                                            segment2,
 302                                                            dest + total,
 303                                                            max - total);
 304         total += partial;
 305     } while (total < max && cpml_primitive_next(&portion));
 306
 307     return total;
 308 }
 309
 310 /**
 311  * cpml_segment_offset:
 312  * @segment: a #CpmlSegment
 313  * @offset: the offset distance
 314  *
 315  * Offsets a segment of the specified amount, that is builds a "parallel"
 316  * segment at the @offset distance from the original one and returns the
 317  * result by replacing the original @segment.
 318  *
 319  * <important>
 320  * <title>TODO</title>
 321  * <itemizedlist>
 322  * <listitem>Closed path are not yet managed: an elegant solution is not
 323  *           so obvious: use cpml_close_offset() when available.</listitem>
 324  * <listitem>Degenerated primitives, such as lines of length 0, are not
 325  *           managed properly.</listitem>
 326  * </itemizedlist>
 327  * </important>
 328  **/
 329 void
 330 cpml_segment_offset(CpmlSegment *segment, double offset)
 331 {
 332     CpmlPrimitive primitive;
 333     CpmlPrimitive last_primitive;
 334     cairo_path_data_t org, old_end;
 335     cairo_bool_t first_cycle;
 336
 337     cpml_primitive_from_segment(&primitive, segment);
 338     first_cycle = 1;
 339
 340     do {
 341         if (!first_cycle) {
 342             org = old_end;
 343             primitive.org = &org;
 344         }
 345
 346         old_end = *cpml_primitive_get_point(&primitive, -1);
 347         cpml_primitive_offset(&primitive, offset);
 348
 349         if (!first_cycle) {
 350             cpml_primitive_join(&last_primitive, &primitive);
 351             primitive.org = cpml_primitive_get_point(&last_primitive, -1);
 352         }
 353
 354         cpml_primitive_copy(&last_primitive, &primitive);
 355         first_cycle = 0;
 356     } while (cpml_primitive_next(&primitive));
 357 }
 358
 359 /**
 360  * normalize:
 361  * @segment: a #CpmlSegment
 362  *
 363  * Strips the leading %CAIRO_PATH_MOVE_TO primitives, updating
 364  * the CpmlSegment structure accordling. One, and only one,
 365  * %CAIRO_PATH_MOVE_TO primitive is left.
 366  *
 367  * Return value: 1 on success, 0 on no leading MOVE_TOs or on errors
 368  **/
 369 static cairo_bool_t
 370 normalize(CpmlSegment *segment)
 371 {
 372     if (!ensure_one_move_to(segment))
 373         return 0;
 374
 375     reshape(segment);
 376     return 1;
 377 }
 378
 379 /**
 380  * ensure_one_move_to:
 381  * @segment: a #CpmlSegment
 382  *
 383  * Strips the leading %CAIRO_PATH_MOVE_TO primitives, updating
 384  * the <structname>CpmlSegment</structname> structure accordling.
 385  * One, and only one, %CAIRO_PATH_MOVE_TO primitive is left.
 386  *
 387  * Return value: 1 on success, 0 on no leading MOVE_TOs or on empty path
 388  **/
 389 static cairo_bool_t
 390 ensure_one_move_to(CpmlSegment *segment)
 391 {
 392     cairo_path_data_t *new_data;
 393     int new_num_data, length;
 394
 395     new_data = segment->data;
 396
 397     /* Check for at least one move to */
 398     if (new_data->header.type != CAIRO_PATH_MOVE_TO)
 399         return 0;
 400
 401     new_num_data = segment->num_data;
 402     length = 0;
 403
 404     /* Strip the leading CAIRO_PATH_MOVE_TO, leaving only the last one */
 405     do {
 406         new_data += length;
 407         new_num_data -= length;
 408         length = new_data->header.length;
 409
 410         /* Check for end of cairo path data */
 411         if (length >= new_num_data)
 412             return 0;
 413     } while (new_data[length].header.type == CAIRO_PATH_MOVE_TO);
 414
 415     segment->data = new_data;
 416     segment->num_data = new_num_data;
 417
 418     return 1;
 419 }
 420
 421 /**
 422  * reshape:
 423  * @segment: a #CpmlSegment
 424  *
 425  * Looks for the segment termination and modify the
 426  * <structfield>num_data</structfield> field of @segment accordling.
 427  * @segment must have only one leading %CAIRO_PATH_MOVE_TO and
 428  * it is supposed to be non-empty, conditions yet imposed by the
 429  * ensure_one_move_to() function.
 430  **/
 431 static void
 432 reshape(CpmlSegment *segment)
 433 {
 434     cairo_path_data_t *data;
 435     int num_data, new_num_data, length;
 436
 437     /* Skip the leading move to */
 438     new_num_data = 2;
 439     data = segment->data + new_num_data;
 440
 441     /* Calculate the remaining data in the cairo path */
 442     num_data = segment->cairo_path->num_data -
 443                (segment->data - segment->cairo_path->data);
 444
 445     while (new_num_data < num_data) {
 446         /* A primitive is considered valid if it has implemented
 447          * its own type_get_npoints() */
 448         if (cpml_primitive_type_get_npoints(data->header.type) < 0)
 449             break;
 450
 451         length = data->header.length;
 452         data += length;
 453         new_num_data += length;
 454     }
 455
 456     segment->num_data = new_num_data;
 457 }