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     data->extents.is_defined = FALSE;
 108
 109     trail->data = data;
 110 }
 111
 112 static void
 113 finalize(GObject *object)
 114 {
 115     clear((AdgModel *) object);
 116
 117     if (PARENT_OBJECT_CLASS->finalize)
 118         PARENT_OBJECT_CLASS->finalize(object);
 119 }
 120
 121
 122 /**
 123  * adg_trail_new:
 124  * @callback: the #CpmlPath constructor function
 125  * @user_data: generic pointer to pass to the callback
 126  *
 127  * Creates a new trail model. The #CpmlPath must be constructed by the
 128  * @callback function: #AdgTrail will not cache anything, so you should
 129  * implement any caching mechanism in the callback, if needed.
 130  *
 131  * Returns: a new trail model
 132  **/
 133 AdgTrail *
 134 adg_trail_new(AdgTrailCallback callback, gpointer user_data)
 135 {
 136     AdgTrail *trail;
 137     AdgTrailPrivate *data;
 138
 139     trail = g_object_new(ADG_TYPE_TRAIL, NULL);
 140     data = trail->data;
 141
 142     data->callback = callback;
 143     data->user_data = user_data;
 144
 145     return trail;
 146 }
 147
 148
 149 /**
 150  * adg_trail_get_cairo_path:
 151  * @trail: an #AdgTrail
 152  *
 153  * Gets a pointer to the cairo path of @trail. The return path is
 154  * owned by @trail and must be considered read-only.
 155  *
 156  * This function gets the #CpmlPath of @trail by calling
 157  * adg_trail_get_cpml_path() and converts its %CAIRO_PATH_ARC_TO
 158  * primitives, not recognized by cairo, into approximated Bézier
 159  * curves primitives (%CAIRO_PATH_CURVE_TO). The conversion is
 160  * cached, so any furter request is O(1). This cache is cleared
 161  * only by the adg_model_clear() method.
 162  *
 163  * <important>
 164  * <title>TODO</title>
 165  * <itemizedlist>
 166  * <listitem>Actually, the arcs are approximated to Bézier using the
 167  *           hardcoded max angle of PI/2. This should be customizable
 168  *           by adding, for instance, a property to the #AdgTrail class
 169  *           with a default value of PI/2.</listitem>
 170  * </itemizedlist>
 171  * </important>
 172  *
 173  * Returns: a pointer to the internal cairo path or %NULL on errors
 174  **/
 175 const cairo_path_t *
 176 adg_trail_get_cairo_path(AdgTrail *trail)
 177 {
 178     AdgTrailPrivate *data;
 179     cairo_path_t *cairo_path;
 180     CpmlPath *src;
 181     GArray *dst;
 182     const cairo_path_data_t *p_src;
 183     int i;
 184
 185     g_return_val_if_fail(ADG_IS_TRAIL(trail), NULL);
 186
 187     data = trail->data;
 188     cairo_path = &data->cairo_path;
 189
 190     /* Check for cached result */
 191     if (cairo_path->data != NULL)
 192         return cairo_path;
 193
 194     src = adg_trail_get_cpml_path(trail);
 195     dst = g_array_sized_new(FALSE, FALSE,
 196                             sizeof(cairo_path_data_t), src->num_data);
 197
 198     /* Cycle the CpmlPath and convert arcs to Bézier curves */
 199     for (i = 0; i < src->num_data; i += p_src->header.length) {
 200         p_src = (const cairo_path_data_t *) src->data + i;
 201
 202         if (p_src->header.type == CAIRO_PATH_ARC_TO)
 203             dst = arc_to_curves(dst, p_src);
 204         else
 205             dst = g_array_append_vals(dst, p_src, p_src->header.length);
 206     }
 207
 208     cairo_path->status = CAIRO_STATUS_SUCCESS;
 209     cairo_path->num_data = dst->len;
 210     cairo_path->data = (cairo_path_data_t *) g_array_free(dst, FALSE);
 211
 212     return cairo_path;
 213 }
 214
 215 /**
 216  * adg_trail_get_cpml_path:
 217  * @trail: an #AdgTrail
 218  *
 219  * Gets the CPML path structure defined by @trail. The returned
 220  * value is managed by the #AdgTrail implementation, that is this
 221  * method simply calls the #AdgTrailClass::get_cpml_path() virtual
 222  * function that any trail instance must implement.
 223  *
 224  * Whenever used internally by the ADG project, the returned path
 225  * is (by convention) owned by @trail and so it should not be freed.
 226  * Anyway, it is allowed to modify it as long as its size is
 227  * retained and its data contains a valid path: this is needed to
 228  * let the #AdgMarker infrastructure work properly (the markers
 229  * should be able to modify the trail where they are applied).
 230  *
 231  * Any further call to this method will probably make the pointer
 232  * previously returned useless because the #CpmlPath could be
 233  * relocated and the old #CpmlPath will likely contain rubbish.
 234  *
 235  * Returns: a pointer to the #CpmlPath or %NULL on errors
 236  **/
 237 CpmlPath *
 238 adg_trail_get_cpml_path(AdgTrail *trail)
 239 {
 240     AdgTrailClass *klass;
 241
 242     g_return_val_if_fail(ADG_IS_TRAIL(trail), NULL);
 243
 244     klass = ADG_TRAIL_GET_CLASS(trail);
 245
 246     if (klass->get_cpml_path == NULL)
 247         return NULL;
 248
 249     return klass->get_cpml_path(trail);
 250 }
 251
 252 /**
 253  * adg_trail_get_segment:
 254  * @trail: an #AdgTrail
 255  * @segment: the destination #AdgSegment
 256  * @n: the segment number to retrieve, where %1 is the first segment
 257  *
 258  * Convenient function to get a segment from @trail. The segment is
 259  * got from the CPML path: check out adg_trail_get_cpml_path() for
 260  * further information.
 261  *
 262  * Returns: %TRUE on success or %FALSE on errors
 263  **/
 264 gboolean
 265 adg_trail_get_segment(AdgTrail *trail, AdgSegment *segment, guint n)
 266 {
 267     CpmlPath *cpml_path;
 268     guint cnt;
 269
 270     g_return_val_if_fail(ADG_IS_TRAIL(trail), FALSE);
 271     g_return_val_if_fail(segment != NULL, FALSE);
 272
 273     if (n == 0) {
 274         g_warning("%s: requested undefined segment for type `%s'",
 275                   G_STRLOC, g_type_name(G_OBJECT_TYPE(trail)));
 276         return FALSE;
 277     }
 278
 279     cpml_path = adg_trail_get_cpml_path(trail);
 280
 281     cpml_segment_from_cairo(segment, cpml_path);
 282     for (cnt = 1; cnt < n; ++cnt)
 283         if (!cpml_segment_next(segment)) {
 284             g_warning("%s: segment `%u' out of range for type `%s'",
 285                       G_STRLOC, n, g_type_name(G_OBJECT_TYPE(trail)));
 286             return FALSE;
 287         }
 288
 289     return TRUE;
 290 }
 291
 292 /**
 293  * adg_trail_get_extents:
 294  * @trail: an #AdgTrail
 295  *
 296  * Gets the extents of @trail. The returned pointer is owned by
 297  * @trail and should not be freed nor modified.
 298  *
 299  * Returns: the requested extents or %NULL on errors
 300  **/
 301 const CpmlExtents *
 302 adg_trail_get_extents(AdgTrail *trail)
 303 {
 304     AdgTrailPrivate *data;
 305
 306     g_return_val_if_fail(ADG_IS_TRAIL(trail), NULL);
 307
 308     data = trail->data;
 309
 310     if (!data->extents.is_defined) {
 311         CpmlPath *cpml_path;
 312         CpmlSegment segment;
 313         CpmlExtents extents;
 314
 315         cpml_path = adg_trail_get_cpml_path(trail);
 316
 317         if (cpml_segment_from_cairo(&segment, cpml_path))
 318             do {
 319                 cpml_segment_extents(&segment, &extents);
 320                 cpml_extents_add(&data->extents, &extents);
 321             } while (cpml_segment_next(&segment));
 322     }
 323
 324     return &data->extents;
 325 }
 326
 327 /**
 328  * adg_trail_dump:
 329  * @trail: an #AdgTrail
 330  *
 331  * Dumps the data content of @trail to stdout in a human readable format.
 332  **/
 333 void
 334 adg_trail_dump(AdgTrail *trail)
 335 {
 336     CpmlSegment segment;
 337     cairo_path_t *cairo_path;
 338
 339     g_return_if_fail(ADG_IS_TRAIL(trail));
 340
 341     cairo_path = (cairo_path_t *) adg_trail_get_cairo_path(trail);
 342
 343     g_return_if_fail(cairo_path != NULL);
 344
 345     if (!cpml_segment_from_cairo(&segment, cairo_path)) {
 346         g_warning("Invalid path data to dump!\n");
 347     } else {
 348         do {
 349             cpml_segment_dump(&segment);
 350         } while (cpml_segment_next(&segment));
 351     }
 352 }
 353
 354
 355 static void
 356 clear(AdgModel *model)
 357 {
 358     AdgTrailPrivate *data = ((AdgTrail *) model)->data;
 359
 360     g_free(data->cairo_path.data);
 361
 362     data->cairo_path.status = CAIRO_STATUS_INVALID_PATH_DATA;
 363     data->cairo_path.data = NULL;
 364     data->cairo_path.num_data = 0;
 365     data->extents.is_defined = FALSE;
 366
 367     if (PARENT_MODEL_CLASS->clear)
 368         PARENT_MODEL_CLASS->clear(model);
 369 }
 370
 371 static CpmlPath *
 372 get_cpml_path(AdgTrail *trail)
 373 {
 374     AdgTrailPrivate *data = trail->data;
 375
 376     if (data->callback == NULL) {
 377         g_warning("%s: callback not defined for instance of type `%s'",
 378                   G_STRLOC, g_type_name(G_OBJECT_TYPE(trail)));
 379         return NULL;
 380     }
 381
 382     return data->callback(trail, data->user_data);
 383 }
 384
 385 static GArray *
 386 arc_to_curves(GArray *array, const cairo_path_data_t *src)
 387 {
 388     CpmlPrimitive arc;
 389     double start, end;
 390
 391     /* Build the arc primitive: the arc origin is supposed to be the previous
 392      * point (src-1): this means a primitive must exist before the arc */
 393     arc.segment = NULL;
 394     arc.org = (cairo_path_data_t *) (src-1);
 395     arc.data = (cairo_path_data_t *) src;
 396
 397     if (cpml_arc_info(&arc, NULL, NULL, &start, &end)) {
 398         CpmlSegment segment;
 399         int n_curves;
 400         cairo_path_data_t *curves;
 401
 402         n_curves = ceil(fabs(end-start) / M_PI_2);
 403         curves = g_new(cairo_path_data_t, n_curves * 4);
 404         segment.data = curves;
 405         cpml_arc_to_curves(&arc, &segment, n_curves);
 406
 407         array = g_array_append_vals(array, curves, n_curves * 4);
 408
 409         g_free(curves);
 410     }
 411
 412     return array;
 413 }