demo/cpml-demo.c

   1 /* ADG - Automatic Drawing Generation
   2  * Copyright (C) 2007,2008,2009,2010,2011,2012,2013  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 #include "demo.h"
  21 #include <cpml.h>
  22 #include <math.h>
  23 #include <gtk/gtk.h>
  24
  25
  26 static void     parse_args              (gint           *p_argc,
  27                                          gchar         **p_argv[]);
  28 static cairo_path_t *
  29                 duplicate_and_stroke    (cairo_t        *cr);
  30 static void     stroke_and_destroy      (cairo_t        *cr,
  31                                          cairo_path_t   *path);
  32
  33 static void     browsing                (GtkWidget      *widget,
  34                                          cairo_t        *cr);
  35
  36 static void     browsing_segment        (GtkToggleButton*togglebutton,
  37                                          gpointer        user_data);
  38 static void     browsing_primitive      (GtkToggleButton*togglebutton,
  39                                          gpointer        user_data);
  40 static void     browsing_reset          (GtkButton      *button,
  41                                          gpointer        user_data);
  42 static void     browsing_next           (GtkButton      *button,
  43                                          gpointer        user_data);
  44
  45 static gboolean arcs                    (GtkWidget      *widget,
  46                                          cairo_t        *cr);
  47
  48 static void     arc3p                   (cairo_t        *cr,
  49                                          double          x1,
  50                                          double          y1,
  51                                          double          x2,
  52                                          double          y2,
  53                                          double          x3,
  54                                          double          y3);
  55
  56 static gboolean intersections           (GtkWidget      *widget,
  57                                          cairo_t        *cr);
  58
  59 static void     algorithm_changed       (GtkRadioButton *button,
  60                                          GtkWidget      *area);
  61 static gboolean offset_curves           (GtkWidget      *widget,
  62                                          cairo_t        *cr);
  63
  64 static gboolean offset_segments         (GtkWidget      *widget,
  65                                          cairo_t        *cr);
  66
  67 #ifdef GTK2_ENABLED
  68
  69 static void
  70 browsing_gtk2(GtkWidget *widget, GdkEventExpose *event, gpointer user_data)
  71 {
  72     cairo_t *cr = gdk_cairo_create(widget->window);
  73     browsing(widget, cr);
  74     cairo_destroy(cr);
  75 }
  76
  77 static void
  78 arcs_gtk2(GtkWidget *widget, GdkEventExpose *event, gpointer user_data)
  79 {
  80     cairo_t *cr = gdk_cairo_create(widget->window);
  81     arcs(widget, cr);
  82     cairo_destroy(cr);
  83 }
  84
  85 static void
  86 intersections_gtk2(GtkWidget *widget)
  87 {
  88     cairo_t *cr = gdk_cairo_create(widget->window);
  89     intersections(widget, cr);
  90     cairo_destroy(cr);
  91 }
  92
  93 static void
  94 offset_curves_gtk2(GtkWidget *widget)
  95 {
  96     cairo_t *cr = gdk_cairo_create(widget->window);
  97     offset_curves(widget, cr);
  98     cairo_destroy(cr);
  99 }
 100
 101 static void
 102 offset_segments_gtk2(GtkWidget *widget)
 103 {
 104     cairo_t *cr = gdk_cairo_create(widget->window);
 105     offset_segments(widget, cr);
 106     cairo_destroy(cr);
 107 }
 108
 109 #endif
 110
 111 static void     circle_callback         (cairo_t        *cr);
 112 static void     piston_callback         (cairo_t        *cr);
 113 static void     curve1_callback         (cairo_t        *cr);
 114 static void     line1_callback          (cairo_t        *cr);
 115
 116 static struct {
 117     GtkWidget           *area;
 118     cairo_path_t        *cairo_path;
 119     gboolean             use_segment;
 120     CpmlSegment          segment;
 121     CpmlPrimitive        primitive;
 122 } browsing_data = {
 123     NULL,
 124 };
 125
 126 static CpmlPair bezier_samples[][4] = {
 127     { { 0, 0 }, { 0, 40 }, { 120, 40 }, { 120, 0 } },   /* Simmetric low */
 128     { { 40, 0 }, { 40, 160 }, { 80, 160 }, { 80, 0 } }, /* Simmetric high */
 129     { { 0, 0 }, { 33.1371, 33.1371 }, { 86.8629, 33.1371 }, { 120, 0 } },
 130                                                         /* Arc approximation */
 131     { { 0, 0 }, { 70, 120 }, { 50, 120 }, { 120, 0 } }, /* Twisted controls */
 132
 133     { { 0, 0 }, { 0, 120 }, { 60, 120 }, { 120, 0 } },  /* Vertical p1-p2 */
 134     { { 0, 0 }, { 60, 120 }, { 120, 120 }, { 120, 0 } },/* Vertical p3-p4 */
 135     { { 0, 120 }, { 120, 120 }, { 120, 60 }, { 0, 0 } },/* Horizontal p1-p2 */
 136     { { 0, 120 }, { 120, 60 }, { 120, 0 }, { 0, 0 } },  /* Horizontal p3-p4 */
 137
 138     { { 0, 0 }, { 0, 120 }, { 120, 120 }, { 120, 0 } }, /* Down */
 139     { { 0, 120 }, { 120, 120 }, { 120, 0 }, { 0, 0 } }, /* Right */
 140     { { 0, 120 }, { 0, 0 }, { 120, 0 }, { 120, 120 } }, /* Up */
 141     { { 120, 120 }, { 0, 120 }, { 0, 0 }, { 120, 0 } }, /* Left */
 142
 143     { { 0, 60 }, { 60, 120 }, { 120, 60 }, { 60, 0 } }, /* Down-right */
 144     { { 60, 120 }, { 120, 60 }, { 60, 0 }, { 0, 60 } }, /* Up-right */
 145     { { 120, 60 }, { 60, 0 }, { 0, 60 }, { 60, 120 } }, /* Up-left */
 146     { { 60, 0 }, { 0, 60 }, { 60, 120 }, { 120, 60 } }, /* Down-left*/
 147
 148     { { 0, 0 }, { 60, 0 }, { 60, 120 }, { 120, 120 } }, /* Step left */
 149     { { 120, 0 }, { 60, 0 }, { 60, 120 }, { 0, 120 } }, /* Step right */
 150     { { 0, 0 }, { 60, 90 }, { 90, 120 }, { 120, 90 } }, /* Unbalanced opened */
 151     { { 0, 0 }, { 40, 120 }, { 120, 120 }, { 60, 80 } } /* Unbalanced closed */
 152 };
 153
 154 static void (*path_samples[]) (cairo_t *cr) = {
 155     circle_callback,
 156     piston_callback,
 157     curve1_callback,
 158     line1_callback,
 159 };
 160
 161 static void
 162 switch_page(GtkTreeSelection *selection, GtkNotebook *notebook)
 163 {
 164     GList *list = gtk_tree_selection_get_selected_rows(selection, NULL);
 165     if (list != NULL) {
 166         GtkTreePath *path = g_list_first(list)->data;
 167         gint page = path != NULL ? *gtk_tree_path_get_indices(path) : -1;
 168         g_list_free_full(list, (GDestroyNotify) gtk_tree_path_free);
 169         if (page >= 0)
 170             gtk_notebook_set_current_page(notebook, page);
 171     }
 172 }
 173
 174 int
 175 main(gint argc, gchar **argv)
 176 {
 177     gchar *path;
 178     GtkBuilder *builder;
 179     GError *error;
 180     GtkWidget *window;
 181     gchar *icons_dir;
 182
 183     _demo_init(argc, argv);
 184     parse_args(&argc, &argv);
 185
 186     /* Prepend the package icons path */
 187     if (is_installed) {
 188 #ifdef G_OS_WIN32
 189         icons_dir = g_build_filename(basedir, PKGDATADIR, "icons", NULL);
 190 #else
 191         icons_dir = g_strdup(PKGDATADIR "/icons");
 192 #endif
 193     } else {
 194         icons_dir = g_strdup(SRCDIR "/icons");
 195     }
 196
 197     gtk_icon_theme_append_search_path(gtk_icon_theme_get_default(), icons_dir);
 198     g_free(icons_dir);
 199
 200     path = _demo_file("cpml-demo.ui");
 201     if (path == NULL) {
 202         g_printerr(_("cpml-demo.ui not found!\n"));
 203         return 1;
 204     }
 205
 206     builder = gtk_builder_new();
 207     error = NULL;
 208
 209     gtk_builder_set_translation_domain(builder, GETTEXT_PACKAGE);
 210     gtk_builder_add_from_file(builder, path, &error);
 211     g_free(path);
 212
 213     if (error != NULL) {
 214         g_print("%s\n", error->message);
 215         return 2;
 216     }
 217
 218     window = (GtkWidget *) gtk_builder_get_object(builder, "wndMain");
 219
 220     /* Connect signals */
 221     g_signal_connect(window, "delete-event", G_CALLBACK(gtk_main_quit), NULL);
 222     g_signal_connect(gtk_tree_view_get_selection(GTK_TREE_VIEW(gtk_builder_get_object(builder, "tvPages"))),
 223                      "changed", G_CALLBACK(switch_page),
 224                      gtk_builder_get_object(builder, "nbPages"));
 225     g_signal_connect(gtk_builder_get_object(builder, "optBrowsingSegment"),
 226                      "toggled", G_CALLBACK(browsing_segment), NULL);
 227     g_signal_connect(gtk_builder_get_object(builder, "optBrowsingPrimitive"),
 228                      "toggled", G_CALLBACK(browsing_primitive), NULL);
 229     g_signal_connect(gtk_builder_get_object(builder, "btnBrowsingReset"),
 230                      "clicked", G_CALLBACK(browsing_reset), NULL);
 231     g_signal_connect(gtk_builder_get_object(builder, "btnBrowsingNext"),
 232                      "clicked", G_CALLBACK(browsing_next), NULL);
 233     g_signal_connect(gtk_builder_get_object(builder, "optAlgorithmDefault"),
 234                      "toggled", G_CALLBACK(algorithm_changed),
 235                      gtk_builder_get_object(builder, "areaOffsetCurves"));
 236     g_signal_connect(gtk_builder_get_object(builder, "optAlgorithmBaioca"),
 237                      "toggled", G_CALLBACK(algorithm_changed),
 238                      gtk_builder_get_object(builder, "areaOffsetCurves"));
 239     g_signal_connect(gtk_builder_get_object(builder, "optAlgorithmHandcraft"),
 240                      "toggled", G_CALLBACK(algorithm_changed),
 241                      gtk_builder_get_object(builder, "areaOffsetCurves"));
 242 #ifdef GTK2_ENABLED
 243     g_signal_connect(gtk_builder_get_object(builder, "areaBrowsing"),
 244                      "expose-event", G_CALLBACK(browsing_gtk2), NULL);
 245     g_signal_connect(gtk_builder_get_object(builder, "areaArcs"),
 246                      "expose-event", G_CALLBACK(arcs_gtk2), NULL);
 247     g_signal_connect(gtk_builder_get_object(builder, "areaIntersections"),
 248                      "expose-event", G_CALLBACK(intersections_gtk2), NULL);
 249     g_signal_connect(gtk_builder_get_object(builder, "areaOffsetCurves"),
 250                      "expose-event", G_CALLBACK(offset_curves_gtk2), NULL);
 251     g_signal_connect(gtk_builder_get_object(builder, "areaOffsetSegments"),
 252                      "expose-event", G_CALLBACK(offset_segments_gtk2), NULL);
 253     g_signal_connect(gtk_builder_get_object(builder, "btnQuit"),
 254                      "clicked", G_CALLBACK(gtk_main_quit), NULL);
 255 #else
 256     g_signal_connect(gtk_builder_get_object(builder, "areaBrowsing"),
 257                      "draw", G_CALLBACK(browsing), NULL);
 258     g_signal_connect(gtk_builder_get_object(builder, "areaArcs"),
 259                      "draw", G_CALLBACK(arcs), NULL);
 260     g_signal_connect(gtk_builder_get_object(builder, "areaIntersections"),
 261                      "draw", G_CALLBACK(intersections), NULL);
 262     g_signal_connect(gtk_builder_get_object(builder, "areaOffsetCurves"),
 263                      "draw", G_CALLBACK(offset_curves), NULL);
 264     g_signal_connect(gtk_builder_get_object(builder, "areaOffsetSegments"),
 265                      "draw", G_CALLBACK(offset_segments), NULL);
 266     g_signal_connect(gtk_builder_get_object(builder, "btnQuit"),
 267                      "clicked", G_CALLBACK(gtk_main_quit), NULL);
 268 #endif
 269
 270     g_object_unref(builder);
 271
 272     gtk_widget_show_all(window);
 273     gtk_main();
 274
 275     return 0;
 276 }
 277
 278
 279 /**********************************************
 280  * Command line options parser
 281  **********************************************/
 282
 283 static void
 284 version(void)
 285 {
 286     g_print("cpml-demo " PACKAGE_VERSION "\n");
 287     exit(0);
 288 }
 289
 290 static void
 291 parse_args(gint *p_argc, gchar **p_argv[])
 292 {
 293     GError *error = NULL;
 294     GOptionEntry entries[] = {
 295         {"version", 'V', G_OPTION_FLAG_NO_ARG, G_OPTION_ARG_CALLBACK,
 296          (gpointer) version, _("Display version information"), NULL},
 297         {NULL}
 298     };
 299
 300     gtk_init_with_args(p_argc, p_argv, _("- CPML demonstration program"),
 301                        entries, GETTEXT_PACKAGE, &error);
 302
 303     if (error != NULL) {
 304         gint error_code = error->code;
 305
 306         g_printerr("%s\n", error->message);
 307
 308         g_error_free(error);
 309         exit(error_code);
 310     }
 311 }
 312
 313
 314 static cairo_path_t *
 315 duplicate_and_stroke(cairo_t *cr)
 316 {
 317     cairo_path_t *path = cairo_copy_path(cr);
 318
 319     cairo_set_line_width(cr, 2.);
 320     cairo_stroke(cr);
 321
 322     return path;
 323 }
 324
 325 static void
 326 stroke_and_destroy(cairo_t *cr, cairo_path_t *path)
 327 {
 328     cairo_append_path(cr, path);
 329     cairo_path_destroy(path);
 330
 331     cairo_set_line_width(cr, 1.);
 332     cairo_stroke(cr);
 333 }
 334
 335
 336 static void
 337 browsing(GtkWidget *widget, cairo_t *cr)
 338 {
 339     if (browsing_data.area == NULL) {
 340         int n;
 341
 342         /* Initialize browsing_data */
 343         browsing_data.area = widget;
 344         browsing_data.use_segment = TRUE;
 345
 346         /* Append all the path samples to the cairo context */
 347         cairo_save(cr);
 348         cairo_translate(cr, 270.5, -120.5);
 349         for (n = 0; n < G_N_ELEMENTS(path_samples); ++n) {
 350             if ((n & 1) == 0) {
 351                 cairo_translate(cr, -270., 240.);
 352             } else {
 353                 cairo_translate(cr, 270., 0.);
 354             }
 355
 356             (path_samples[n]) (cr);
 357         }
 358
 359         cairo_restore(cr);
 360         browsing_data.cairo_path = cairo_copy_path(cr);
 361         cpml_segment_from_cairo(&browsing_data.segment,
 362                                 browsing_data.cairo_path);
 363         cpml_primitive_from_segment(&browsing_data.primitive,
 364                                     &browsing_data.segment);
 365     } else {
 366         cairo_append_path(cr, browsing_data.cairo_path);
 367     }
 368
 369     cairo_set_line_width(cr, 2.);
 370     cairo_stroke(cr);
 371
 372     cairo_set_source_rgb(cr, 1., 0.4, 0.);
 373     cairo_set_line_width(cr, 5.);
 374
 375     if (browsing_data.use_segment)
 376         cpml_segment_to_cairo(&browsing_data.segment, cr);
 377     else
 378         cpml_primitive_to_cairo(&browsing_data.primitive, cr);
 379
 380     cairo_stroke(cr);
 381 }
 382
 383 static void
 384 browsing_segment(GtkToggleButton *togglebutton, gpointer user_data)
 385 {
 386     if (!gtk_toggle_button_get_active(togglebutton))
 387         return;
 388
 389     browsing_data.use_segment = TRUE;
 390     gtk_widget_queue_draw(browsing_data.area);
 391 }
 392
 393 static void
 394 browsing_primitive(GtkToggleButton*togglebutton, gpointer user_data)
 395 {
 396     if (!gtk_toggle_button_get_active(togglebutton))
 397         return;
 398
 399     browsing_data.use_segment = FALSE;
 400     gtk_widget_queue_draw(browsing_data.area);
 401 }
 402
 403 static void
 404 browsing_reset(GtkButton *button, gpointer user_data)
 405 {
 406     if (browsing_data.use_segment) {
 407         cpml_segment_reset(&browsing_data.segment);
 408         cpml_primitive_from_segment(&browsing_data.primitive,
 409                                     &browsing_data.segment);
 410     } else {
 411         cpml_primitive_reset(&browsing_data.primitive);
 412     }
 413
 414     gtk_widget_queue_draw(browsing_data.area);
 415 }
 416
 417 static void
 418 browsing_next(GtkButton *button, gpointer user_data)
 419 {
 420     if (browsing_data.use_segment) {
 421         cpml_segment_next(&browsing_data.segment);
 422         cpml_primitive_from_segment(&browsing_data.primitive,
 423                                     &browsing_data.segment);
 424     } else {
 425         cpml_primitive_next(&browsing_data.primitive);
 426     }
 427
 428     gtk_widget_queue_draw(browsing_data.area);
 429 }
 430
 431
 432 static gboolean
 433 arcs(GtkWidget *widget, cairo_t *cr)
 434 {
 435     cairo_translate(cr, 100.5, 100.5);
 436     arc3p(cr, 0, 0, 0, 120, 120, 120);
 437
 438     cairo_translate(cr, 200, 0.);
 439     arc3p(cr, 0, 0, 120, 0, 120, 120);
 440
 441     cairo_translate(cr, 200, 0.);
 442     arc3p(cr, 60, 0, 0, 120, 120, 120);
 443
 444     cairo_translate(cr, -400, 200);
 445     arc3p(cr, 0, 50, -2, 85, 120, 0);
 446
 447     cairo_translate(cr, 200, 0);
 448     arc3p(cr, -2, 85, 0, 50, 120, 0);
 449
 450     return FALSE;
 451 }
 452
 453 static void
 454 arc3p(cairo_t *cr, double x1, double y1,
 455       double x2, double y2, double x3, double y3)
 456 {
 457     CpmlPrimitive arc;
 458     cairo_path_data_t p[4];
 459     CpmlPair center;
 460     double r, start, end;
 461
 462     arc.segment = NULL;
 463     arc.org = &p[0];
 464     arc.data = &p[1];
 465
 466     p[1].header.type = CPML_ARC;
 467     p[1].header.length = 3;
 468
 469     p[0].point.x = x1;
 470     p[0].point.y = y1;
 471     p[2].point.x = x2;
 472     p[2].point.y = y2;
 473     p[3].point.x = x3;
 474     p[3].point.y = y3;
 475
 476     cpml_primitive_to_cairo(&arc, cr);
 477
 478     cairo_set_line_width(cr, 1.);
 479     cairo_stroke(cr);
 480
 481     /* Add an arc generated by cairo, just for reference */
 482     if (!cpml_arc_info(&arc, &center, &r, &start, &end)) {
 483         g_warning(_("Unable to get arc info (%lf, %lf) (%lf, %lf) (%lf, %lf)\n"),
 484                   x1, y1, x2, y2, x3, y3);
 485         return;
 486     }
 487
 488     if (start < end)
 489         cairo_arc(cr, center.x, center.y, r-5., start, end);
 490     else
 491         cairo_arc_negative(cr, center.x, center.y, r-5., start, end);
 492
 493     /* Show the inscribed triangle */
 494     cairo_move_to(cr, x1, y1);
 495     cairo_line_to(cr, x2, y2);
 496     cairo_line_to(cr, x3, y3);
 497
 498     cairo_set_line_width(cr, 0.5);
 499     cairo_stroke(cr);
 500 }
 501
 502
 503 static gboolean
 504 intersections(GtkWidget *widget, cairo_t *cr)
 505 {
 506     cairo_path_t *path;
 507     CpmlSegment segment1, segment2;
 508     CpmlPair intersection;
 509
 510     cairo_translate(cr, 10.5, 120.5);
 511
 512     line1_callback(cr);
 513
 514     path = cairo_copy_path(cr);
 515
 516     cairo_set_line_width(cr, 1.);
 517     cairo_stroke(cr);
 518
 519     cpml_segment_from_cairo(&segment1, path);
 520     cpml_segment_from_cairo(&segment2, path);
 521
 522     while (cpml_segment_next(&segment2)) {
 523         cpml_segment_put_intersections(&segment1, &segment2, 1, &intersection);
 524
 525         cairo_arc(cr, intersection.x, intersection.y, 2.5, 0, 2 * M_PI);
 526         cairo_fill(cr);
 527
 528         cpml_segment_next(&segment1);
 529     }
 530
 531     cairo_path_destroy(path);
 532     return FALSE;
 533 }
 534
 535
 536 static void
 537 algorithm_changed(GtkRadioButton *button, GtkWidget *area)
 538 {
 539     const gchar *button_name;
 540     CpmlCurveOffsetAlgorithm new_algorithm;
 541
 542     if (! gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(button)))
 543         return;
 544
 545
 546     button_name = gtk_widget_get_name(GTK_WIDGET(button));
 547
 548     if (g_strcmp0(button_name, "DEFAULT") == 0) {
 549         new_algorithm = CPML_CURVE_OFFSET_ALGORITHM_DEFAULT;
 550     } else if (g_strcmp0(button_name, "BAIOCA") == 0) {
 551         new_algorithm = CPML_CURVE_OFFSET_ALGORITHM_BAIOCA;
 552     } else if (g_strcmp0(button_name, "HANDCRAFT") == 0) {
 553         new_algorithm = CPML_CURVE_OFFSET_ALGORITHM_HANDCRAFT;
 554     } else {
 555         g_warning("Unknown offset algorithm name (%s)", button_name);
 556         new_algorithm = CPML_CURVE_OFFSET_ALGORITHM_NONE;
 557     }
 558
 559     cpml_curve_offset_algorithm(new_algorithm);
 560     gtk_widget_queue_draw(area);
 561 }
 562
 563 static gboolean
 564 offset_curves(GtkWidget *widget, cairo_t *cr)
 565 {
 566     gint n;
 567     CpmlPair *bezier;
 568     cairo_path_t *path, *path_copy;
 569     CpmlSegment segment;
 570     CpmlPrimitive primitive;
 571     CpmlPair pair;
 572     double t;
 573
 574     /* Add the Bézier curve samples */
 575     for (n = 0; n < G_N_ELEMENTS(bezier_samples); ++n) {
 576         bezier = &bezier_samples[n][0];
 577
 578         /* The samples are arranged in a 4x? matrix of 200x150 cells */
 579         if (n == 0)
 580             cairo_translate(cr, 25., 25.);
 581         else if (n % 4 == 0)
 582             cairo_translate(cr, -600., 150.);
 583         else
 584             cairo_translate(cr, 200., 0.);
 585
 586         /* Draw the Bézier curve */
 587         cairo_move_to(cr, bezier[0].x, bezier[0].y);
 588         cairo_curve_to(cr, bezier[1].x, bezier[1].y,
 589                        bezier[2].x, bezier[2].y, bezier[3].x, bezier[3].y);
 590
 591         /* Create a copy, to be used after */
 592         path_copy = cairo_copy_path(cr);
 593
 594         path = duplicate_and_stroke(cr);
 595         cpml_segment_from_cairo(&segment, path);
 596         cpml_segment_offset(&segment, 20.);
 597         stroke_and_destroy(cr, path);
 598
 599         cpml_segment_from_cairo(&segment, path_copy);
 600         cpml_primitive_from_segment(&primitive, &segment);
 601
 602         /* Draw the rays for visual debugging */
 603         cairo_set_line_width(cr, 1.);
 604         for (t = 0; t < 1; t += 0.1) {
 605             cpml_curve_put_pair_at_time(&primitive, t, &pair);
 606
 607             cairo_new_sub_path(cr);
 608             cairo_arc(cr, pair.x, pair.y, 2.5, 0, M_PI*2);
 609             cairo_fill(cr);
 610
 611             cairo_move_to(cr, pair.x, pair.y);
 612             cpml_curve_put_offset_at_time(&primitive, t, 20., &pair);
 613             cairo_line_to(cr, pair.x, pair.y);
 614             cairo_stroke(cr);
 615         }
 616
 617         cairo_path_destroy(path_copy);
 618     }
 619
 620     return FALSE;
 621 }
 622
 623
 624 static gboolean
 625 offset_segments(GtkWidget *widget, cairo_t *cr)
 626 {
 627     cairo_path_t *path;
 628     CpmlSegment segment;
 629     int n;
 630
 631     cairo_translate(cr, 270.5, -120.5);
 632
 633     /* Offset the path samples */
 634     for (n = 0; n < G_N_ELEMENTS(path_samples); ++n) {
 635         if ((n & 1) == 0) {
 636             cairo_translate(cr, -270., 240.);
 637         } else {
 638             cairo_translate(cr, 270., 0.);
 639         }
 640
 641         /* Call the path callback */
 642         (path_samples[n]) (cr);
 643
 644         path = duplicate_and_stroke(cr);
 645         cpml_segment_from_cairo(&segment, path);
 646         cpml_segment_offset(&segment, 15.);
 647         stroke_and_destroy(cr, path);
 648     }
 649
 650     return FALSE;
 651 }
 652
 653
 654 static void
 655 circle_callback(cairo_t *cr)
 656 {
 657     cairo_new_sub_path(cr);
 658     cairo_arc(cr, 120., 0., 100., 0., M_PI*2);
 659 }
 660
 661 static void
 662 piston_callback(cairo_t *cr)
 663 {
 664     cairo_path_t *old_path, *path;
 665     cairo_matrix_t matrix;
 666     CpmlSegment segment;
 667
 668     /* Save the previous path, if any */
 669     old_path = cairo_copy_path(cr);
 670
 671     cairo_new_path(cr);
 672     cairo_move_to(cr,  0.,   46.5);
 673     cairo_line_to(cr, 210.,   46.5);
 674     cairo_line_to(cr, 222.5,  35.);
 675     cairo_line_to(cr, 270.,   35.);
 676     cairo_line_to(cr, 270.,   56.);
 677     cairo_line_to(cr, 273.,   59.);
 678     cairo_line_to(cr, 302.,   59.);
 679     cairo_line_to(cr, 305.,   56.);
 680     cairo_arc(cr,     325.,   52.5,  20., G_PI, 3. * G_PI_2);
 681     cairo_line_to(cr, 400.,   32.5);
 682     cairo_line_to(cr, 410.,   22.5);
 683     cairo_line_to(cr, 450.,   22.5);
 684     cairo_arc_negative(cr,
 685                       452.,   34.,    2., G_PI,      G_PI_2);
 686     cairo_line_to(cr, 460.,   36.);
 687     cairo_line_to(cr, 470.,   30.);
 688     cairo_line_to(cr, 472.,   12.5);
 689
 690     /* Mirror a reversed copy of the current path on the y = 0 axis */
 691     path = cairo_copy_path(cr);
 692     cpml_segment_from_cairo(&segment, path);
 693
 694     cpml_segment_reverse(&segment);
 695     cairo_matrix_init_scale(&matrix, 1., -1.);
 696     cpml_segment_transform(&segment, &matrix);
 697
 698     /* Join the mirrored path to the old path... */
 699     path->data[0].header.type = CPML_LINE;
 700     cairo_append_path(cr, path);
 701     cairo_path_destroy(path);
 702
 703     /* ...and close the shape */
 704     cairo_close_path(cr);
 705
 706     /* Save the resulting path and clear the path memory */
 707     path = cairo_copy_path(cr);
 708     cairo_new_path(cr);
 709
 710     /* Restore the previous path and reappend the new path */
 711     cairo_append_path(cr, old_path);
 712     cairo_path_destroy(old_path);
 713     cairo_append_path(cr, path);
 714     cairo_path_destroy(path);
 715 }
 716
 717 static void
 718 curve1_callback(cairo_t *cr)
 719 {
 720     cairo_move_to(cr,    30.,   0.);
 721     cairo_curve_to(cr,  120., 120.,  180., 100.,  180.,  20.);
 722     cairo_curve_to(cr,  180., -20.,   50.,  40.,  150.,  40.);
 723     cairo_curve_to(cr,  220.,  40.,  190., -60.,  150., -60.);
 724     cairo_curve_to(cr,  100., -60.,   80., -40.,   60., -60.);
 725 }
 726
 727 static void
 728 line1_callback(cairo_t *cr)
 729 {
 730     cairo_move_to(cr, 0, -50);
 731     cairo_line_to(cr, 100, 50);
 732
 733     cairo_move_to(cr, 100, -50);
 734     cairo_line_to(cr, 0, 50);
 735
 736     cairo_move_to(cr, 120, -50);
 737     cairo_line_to(cr, 200, -10);
 738
 739     cairo_move_to(cr, 120, 50);
 740     cairo_line_to(cr, 200, 10);
 741
 742     cairo_move_to(cr, 220, 0);
 743     cairo_line_to(cr, 280, 0);
 744
 745     cairo_move_to(cr, 270, -40);
 746     cairo_line_to(cr, 270, 20);
 747
 748     cairo_move_to(cr, 320, 60);
 749     cairo_line_to(cr, 380, 60);
 750
 751     cairo_move_to(cr, 300, -40);
 752     cairo_line_to(cr, 340, 0);
 753
 754     cairo_move_to(cr, 480, 10);
 755     cairo_line_to(cr, 400, 40);
 756
 757     cairo_move_to(cr, 400, 40);
 758     cairo_line_to(cr, 450, -40);
 759 }