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