adg/adg-trail.c

   1 /* ADG - Automatic Drawing Generation
   2  * Copyright (C) 2007,2008,2009 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 /**
  22  * SECTION:adg-trail
  23  * @short_description: A bare model built around #CpmlPath
  24  *
  25  * The #AdgTrail model is a really basic model built around the #CpmlPath
  26  * struct: for a full fledged path model consider using #AdgPath.
  27  *
  28  * A trail is a path model that demands all the implementation details to
  29  * the caller: this requires a deep knowledge of the ADG details but
  30  * provides a great customization level. It should be used when an
  31  * #AdgPath is not enough, such as when a model is subject to change
  32  * dynamically and the global and local maps do not suffice to express
  33  * this alteration. A typical example is the path used to draw extension
  34  * lines and base line of #AdgLDim: every point is subject to different
  35  * constrains not expressible with a single affine transformation.
  36  **/
  37
  38 /**
  39  * AdgTrail:
  40  *
  41  * All fields are private and should not be used directly.
  42  * Use its public methods instead.
  43  **/
  44
  45 /**
  46  * AdgTrailCallback:
  47  * @trail: an #AdgTrail
  48  * @user_data: the general purpose pointer set by adg_trail_new()
  49  *
  50  * This is the callback used to generate the #CpmlPath and it is
  51  * called directly by adg_trail_cpml_path(). The caller owns
  52  * the returned path, that is the finalization of the returned
  53  * #CpmlPath should be made by the caller when appropriate.
  54  *
  55  * Returns: the #CpmlPath of this trail model
  56  **/
  57
  58
  59 #include "adg-internal.h"
  60 #include "adg-trail.h"
  61 #include "adg-trail-private.h"
  62
  63 #define PARENT_OBJECT_CLASS  ((GObjectClass *) adg_trail_parent_class)
  64 #define PARENT_MODEL_CLASS   ((AdgModelClass *) adg_trail_parent_class)
  65
  66
  67 static void             finalize                (GObject        *object);
  68 static void             clear                   (AdgModel       *model);
  69 static CpmlPath *       get_cpml_path           (AdgTrail       *trail);
  70 static GArray *         arc_to_curves           (GArray         *array,
  71                                                  const cairo_path_data_t
  72                                                                 *src);
  73
  74
  75 G_DEFINE_TYPE(AdgTrail, adg_trail, ADG_TYPE_MODEL);
  76
  77
  78 static void
  79 adg_trail_class_init(AdgTrailClass *klass)
  80 {
  81     GObjectClass *gobject_class;
  82     AdgModelClass *model_class;
  83
  84     gobject_class = (GObjectClass *) klass;
  85     model_class = (AdgModelClass *) klass;
  86
  87     g_type_class_add_private(klass, sizeof(AdgTrailPrivate));
  88
  89     gobject_class->finalize = finalize;
  90
  91     model_class->clear = clear;
  92
  93     klass->get_cpml_path = get_cpml_path;
  94 }
  95
  96 static void
  97 adg_trail_init(AdgTrail *trail)
  98 {
  99     AdgTrailPrivate *data = G_TYPE_INSTANCE_GET_PRIVATE(trail, ADG_TYPE_TRAIL,
 100                                                         AdgTrailPrivate);
 101
 102     data->cairo_path.status = CAIRO_STATUS_INVALID_PATH_DATA;
 103     data->cairo_path.data = NULL;
 104     data->cairo_path.num_data = 0;
 105     data->callback = NULL;
 106     data->user_data = NULL;
 107
 108     data->in_construction = FALSE;
 109     data->extents.is_defined = FALSE;
 110
 111     trail->data = data;
 112 }
 113
 114 static void
 115 finalize(GObject *object)
 116 {
 117     clear((AdgModel *) object);
 118
 119     if (PARENT_OBJECT_CLASS->finalize)
 120         PARENT_OBJECT_CLASS->finalize(object);
 121 }
 122
 123
 124 /**
 125  * adg_trail_new:
 126  * @callback: the #CpmlPath constructor function
 127  * @user_data: generic pointer to pass to the callback
 128  *
 129  * Creates a new trail model. The #CpmlPath must be constructed by the
 130  * @callback function: #AdgTrail will not cache anything, so you should
 131  * implement any caching mechanism in the callback, if needed.
 132  *
 133  * Returns: a new trail model
 134  **/
 135 AdgTrail *
 136 adg_trail_new(AdgTrailCallback callback, gpointer user_data)
 137 {
 138     AdgTrail *trail;
 139     AdgTrailPrivate *data;
 140
 141     trail = g_object_new(ADG_TYPE_TRAIL, NULL);
 142     data = trail->data;
 143
 144     data->callback = callback;
 145     data->user_data = user_data;
 146
 147     return trail;
 148 }
 149
 150
 151 /**
 152  * adg_trail_get_cairo_path:
 153  * @trail: an #AdgTrail
 154  *
 155  * Gets a pointer to the cairo path of @trail. The return path is
 156  * owned by @trail and must be considered read-only.
 157  *
 158  * This function gets the #CpmlPath of @trail by calling
 159  * adg_trail_cpml_path() and converts its %CAIRO_PATH_ARC_TO
 160  * primitives, not recognized by cairo, into approximated Bézier
 161  * curves primitives (%CAIRO_PATH_CURVE_TO). The conversion is
 162  * cached, so any furter request is O(1). This cache is cleared
 163  * only by the adg_model_clear() method.
 164  *
 165  * <important>
 166  * <title>TODO</title>
 167  * <itemizedlist>
 168  * <listitem>Actually, the arcs are approximated with Bézier using the
 169  *           hardcoded max angle of PI/2. This should be customizable
 170  *           by adding, for instance, a property to the #AdgTrail class
 171  *           with a default value of PI/2.</listitem>
 172  * </itemizedlist>
 173  * </important>
 174  *
 175  * Returns: a pointer to the internal cairo path or %NULL on errors
 176  **/
 177 const cairo_path_t *
 178 adg_trail_get_cairo_path(AdgTrail *trail)
 179 {
 180     AdgTrailPrivate *data;
 181     cairo_path_t *cairo_path;
 182     CpmlPath *src;
 183     GArray *dst;
 184     const cairo_path_data_t *p_src;
 185     int i;
 186
 187     g_return_val_if_fail(ADG_IS_TRAIL(trail), NULL);
 188
 189     data = trail->data;
 190     cairo_path = &data->cairo_path;
 191
 192     /* Check for cached result */
 193     if (cairo_path->data != NULL)
 194         return cairo_path;
 195
 196     src = adg_trail_cpml_path(trail);
 197     dst = g_array_sized_new(FALSE, FALSE,
 198                             sizeof(cairo_path_data_t), src->num_data);
 199
 200     /* Cycle the CpmlPath and convert arcs to Bézier curves */
 201     for (i = 0; i < src->num_data; i += p_src->header.length) {
 202         p_src = (const cairo_path_data_t *) src->data + i;
 203
 204         if (p_src->header.type == CAIRO_PATH_ARC_TO)
 205             dst = arc_to_curves(dst, p_src);
 206         else
 207             dst = g_array_append_vals(dst, p_src, p_src->header.length);
 208     }
 209
 210     cairo_path->status = CAIRO_STATUS_SUCCESS;
 211     cairo_path->num_data = dst->len;
 212     cairo_path->data = (cairo_path_data_t *) g_array_free(dst, FALSE);
 213
 214     return cairo_path;
 215 }
 216
 217 /**
 218  * adg_trail_cpml_path:
 219  * @trail: an #AdgTrail
 220  *
 221  * Gets the CPML path structure defined by @trail. The returned
 222  * value is managed by the #AdgTrail implementation, that is this
 223  * function directly calls the #AdgTrailClass::get_cpml_path()
 224  * virtual method that any trail instance must have.
 225  *
 226  * Whenever used internally by the ADG project, the returned path
 227  * is (by convention) owned by @trail and so it should not be freed.
 228  * Anyway, callers are allowed to modify it as long as its size is
 229  * retained and its data contains a valid path: this is needed to
 230  * let the #AdgMarker infrastructure work properly (the markers
 231  * should be able to modify the trail where they are applied).
 232  *
 233  * Any further call to this method will probably make the pointer
 234  * previously returned useless because the #CpmlPath could be
 235  * relocated and the old #CpmlPath will likely contain rubbish.
 236  *
 237  * Returns: a pointer to the #CpmlPath or %NULL on errors
 238  **/
 239 CpmlPath *
 240 adg_trail_cpml_path(AdgTrail *trail)
 241 {
 242     AdgTrailClass *klass;
 243     AdgTrailPrivate *data;
 244     CpmlPath *cpml_path;
 245
 246     g_return_val_if_fail(ADG_IS_TRAIL(trail), NULL);
 247
 248     klass = ADG_TRAIL_GET_CLASS(trail);
 249     if (klass->get_cpml_path == NULL)
 250         return NULL;
 251
 252     data = trail->data;
 253     if (data->in_construction) {
 254         g_warning(_("%s: you cannot access the path from the callback you provided to build it"),
 255                   G_STRLOC);
 256         return NULL;
 257     }
 258
 259     data->in_construction = TRUE;
 260     cpml_path = klass->get_cpml_path(trail);
 261     data->in_construction = FALSE;
 262
 263     return cpml_path;
 264 }
 265
 266 /**
 267  * adg_trail_put_segment:
 268  * @trail: an #AdgTrail
 269  * @n_segment: the segment to retrieve, where %1 is the first segment
 270  * @segment: the destination #AdgSegment
 271  *
 272  * Convenient function to get a segment from @trail. The segment is
 273  * got from the CPML path: check out adg_trail_cpml_path() for
 274  * further information.
 275  *
 276  * Returns: %TRUE on success or %FALSE on errors
 277  **/
 278 gboolean
 279 adg_trail_put_segment(AdgTrail *trail, guint n_segment, AdgSegment *segment)
 280 {
 281     CpmlPath *cpml_path;
 282     guint cnt;
 283
 284     g_return_val_if_fail(ADG_IS_TRAIL(trail), FALSE);
 285     g_return_val_if_fail(segment != NULL, FALSE);
 286
 287     if (n_segment == 0) {
 288         g_warning(_("%s: requested undefined segment for type `%s'"),
 289                   G_STRLOC, g_type_name(G_OBJECT_TYPE(trail)));
 290         return FALSE;
 291     }
 292
 293     cpml_path = adg_trail_cpml_path(trail);
 294
 295     cpml_segment_from_cairo(segment, cpml_path);
 296     for (cnt = 1; cnt < n_segment; ++cnt)
 297         if (!cpml_segment_next(segment)) {
 298             g_warning(_("%s: segment %u is out of range for type `%s'"),
 299                       G_STRLOC, n_segment, g_type_name(G_OBJECT_TYPE(trail)));
 300             return FALSE;
 301         }
 302
 303     return TRUE;
 304 }
 305
 306 /**
 307  * adg_trail_get_extents:
 308  * @trail: an #AdgTrail
 309  *
 310  * Gets the extents of @trail. The returned pointer is owned by
 311  * @trail and should not be freed nor modified.
 312  *
 313  * Returns: the requested extents or %NULL on errors
 314  **/
 315 const CpmlExtents *
 316 adg_trail_get_extents(AdgTrail *trail)
 317 {
 318     AdgTrailPrivate *data;
 319
 320     g_return_val_if_fail(ADG_IS_TRAIL(trail), NULL);
 321
 322     data = trail->data;
 323
 324     if (!data->extents.is_defined) {
 325         CpmlPath *cpml_path;
 326         CpmlSegment segment;
 327         CpmlExtents extents;
 328
 329         cpml_path = adg_trail_cpml_path(trail);
 330
 331         if (cpml_segment_from_cairo(&segment, cpml_path))
 332             do {
 333                 cpml_segment_extents(&segment, &extents);
 334                 cpml_extents_add(&data->extents, &extents);
 335             } while (cpml_segment_next(&segment));
 336     }
 337
 338     return &data->extents;
 339 }
 340
 341 /**
 342  * adg_trail_dump:
 343  * @trail: an #AdgTrail
 344  *
 345  * Dumps the data content of @trail to stdout in a human readable format.
 346  **/
 347 void
 348 adg_trail_dump(AdgTrail *trail)
 349 {
 350     CpmlSegment segment;
 351     cairo_path_t *cairo_path;
 352
 353     g_return_if_fail(ADG_IS_TRAIL(trail));
 354
 355     cairo_path = (cairo_path_t *) adg_trail_get_cairo_path(trail);
 356
 357     g_return_if_fail(cairo_path != NULL);
 358
 359     if (!cpml_segment_from_cairo(&segment, cairo_path)) {
 360         g_warning(_("%s: Invalid path data to dump!"), G_STRLOC);
 361     } else {
 362         do {
 363             cpml_segment_dump(&segment);
 364         } while (cpml_segment_next(&segment));
 365     }
 366 }
 367
 368
 369 static void
 370 clear(AdgModel *model)
 371 {
 372     AdgTrailPrivate *data = ((AdgTrail *) model)->data;
 373
 374     g_free(data->cairo_path.data);
 375
 376     data->cairo_path.status = CAIRO_STATUS_INVALID_PATH_DATA;
 377     data->cairo_path.data = NULL;
 378     data->cairo_path.num_data = 0;
 379     data->extents.is_defined = FALSE;
 380
 381     if (PARENT_MODEL_CLASS->clear)
 382         PARENT_MODEL_CLASS->clear(model);
 383 }
 384
 385 static CpmlPath *
 386 get_cpml_path(AdgTrail *trail)
 387 {
 388     AdgTrailPrivate *data = trail->data;
 389
 390     if (data->callback == NULL) {
 391         g_warning(_("%s: callback not defined for instance of type `%s'"),
 392                   G_STRLOC, g_type_name(G_OBJECT_TYPE(trail)));
 393         return NULL;
 394     }
 395
 396     return data->callback(trail, data->user_data);
 397 }
 398
 399 static GArray *
 400 arc_to_curves(GArray *array, const cairo_path_data_t *src)
 401 {
 402     CpmlPrimitive arc;
 403     double start, end;
 404
 405     /* Build the arc primitive: the arc origin is supposed to be the previous
 406      * point (src-1): this means a primitive must exist before the arc */
 407     arc.segment = NULL;
 408     arc.org = (cairo_path_data_t *) (src-1);
 409     arc.data = (cairo_path_data_t *) src;
 410
 411     if (cpml_arc_info(&arc, NULL, NULL, &start, &end)) {
 412         CpmlSegment segment;
 413         int n_curves;
 414         cairo_path_data_t *curves;
 415
 416         n_curves = ceil(fabs(end-start) / M_PI_2);
 417         curves = g_new(cairo_path_data_t, n_curves * 4);
 418         segment.data = curves;
 419         cpml_arc_to_curves(&arc, &segment, n_curves);
 420
 421         array = g_array_append_vals(array, curves, n_curves * 4);
 422
 423         g_free(curves);
 424     }
 425
 426     return array;
 427 }