1 /** \file
2 * <sodipodi:spiral> implementation
3 */
4 /*
5 * Authors:
6 * Mitsuru Oka <oka326@parkcity.ne.jp>
7 * Lauris Kaplinski <lauris@kaplinski.com>
8 * Abhishek Sharma
9 *
10 * Copyright (C) 1999-2002 Lauris Kaplinski
11 * Copyright (C) 2000-2001 Ximian, Inc.
12 *
13 * Released under GNU GPL, read the file 'COPYING' for more information
14 */
16 #include "config.h"
19 #include "svg/svg.h"
20 #include "attributes.h"
21 #include <2geom/bezier-utils.h>
22 #include <2geom/pathvector.h>
23 #include "display/curve.h"
24 #include <glibmm/i18n.h>
25 #include "xml/repr.h"
26 #include "document.h"
28 #include "sp-spiral.h"
30 static void sp_spiral_class_init (SPSpiralClass *klass);
31 static void sp_spiral_init (SPSpiral *spiral);
33 static void sp_spiral_build (SPObject * object, SPDocument * document, Inkscape::XML::Node * repr);
34 static Inkscape::XML::Node *sp_spiral_write (SPObject *object, Inkscape::XML::Document *doc, Inkscape::XML::Node *repr, guint flags);
35 static void sp_spiral_set (SPObject *object, unsigned int key, const gchar *value);
36 static void sp_spiral_update (SPObject *object, SPCtx *ctx, guint flags);
38 static gchar * sp_spiral_description (SPItem * item);
39 static void sp_spiral_snappoints(SPItem const *item, std::vector<Inkscape::SnapCandidatePoint> &p, Inkscape::SnapPreferences const *snapprefs);
41 static void sp_spiral_set_shape (SPShape *shape);
42 static void sp_spiral_update_patheffect (SPLPEItem *lpeitem, bool write);
44 static Geom::Point sp_spiral_get_tangent (SPSpiral const *spiral, gdouble t);
46 static SPShapeClass *parent_class;
48 /**
49 * Register SPSpiral class and return its type number.
50 */
51 GType
52 sp_spiral_get_type (void)
53 {
54 static GType spiral_type = 0;
56 if (!spiral_type) {
57 GTypeInfo spiral_info = {
58 sizeof (SPSpiralClass),
59 NULL, /* base_init */
60 NULL, /* base_finalize */
61 (GClassInitFunc) sp_spiral_class_init,
62 NULL, /* class_finalize */
63 NULL, /* class_data */
64 sizeof (SPSpiral),
65 16, /* n_preallocs */
66 (GInstanceInitFunc) sp_spiral_init,
67 NULL, /* value_table */
68 };
69 spiral_type = g_type_register_static (SP_TYPE_SHAPE, "SPSpiral", &spiral_info, (GTypeFlags)0);
70 }
71 return spiral_type;
72 }
74 /**
75 * SPSpiral vtable initialization.
76 */
77 static void
78 sp_spiral_class_init (SPSpiralClass *klass)
79 {
80 GObjectClass * gobject_class;
81 SPObjectClass * sp_object_class;
82 SPItemClass * item_class;
83 SPLPEItemClass * lpe_item_class;
84 SPShapeClass *shape_class;
86 gobject_class = (GObjectClass *) klass;
87 sp_object_class = (SPObjectClass *) klass;
88 item_class = (SPItemClass *) klass;
89 lpe_item_class = (SPLPEItemClass *) klass;
90 shape_class = (SPShapeClass *) klass;
92 parent_class = (SPShapeClass *)g_type_class_ref (SP_TYPE_SHAPE);
94 sp_object_class->build = sp_spiral_build;
95 sp_object_class->write = sp_spiral_write;
96 sp_object_class->set = sp_spiral_set;
97 sp_object_class->update = sp_spiral_update;
99 item_class->description = sp_spiral_description;
100 item_class->snappoints = sp_spiral_snappoints;
102 lpe_item_class->update_patheffect = sp_spiral_update_patheffect;
104 shape_class->set_shape = sp_spiral_set_shape;
105 }
107 /**
108 * Callback for SPSpiral object initialization.
109 */
110 static void
111 sp_spiral_init (SPSpiral * spiral)
112 {
113 spiral->cx = 0.0;
114 spiral->cy = 0.0;
115 spiral->exp = 1.0;
116 spiral->revo = 3.0;
117 spiral->rad = 1.0;
118 spiral->arg = 0.0;
119 spiral->t0 = 0.0;
120 }
122 /**
123 * Virtual build: set spiral properties from corresponding repr.
124 */
125 static void
126 sp_spiral_build (SPObject * object, SPDocument * document, Inkscape::XML::Node * repr)
127 {
128 if (((SPObjectClass *) parent_class)->build)
129 ((SPObjectClass *) parent_class)->build (object, document, repr);
131 object->readAttr( "sodipodi:cx" );
132 object->readAttr( "sodipodi:cy" );
133 object->readAttr( "sodipodi:expansion" );
134 object->readAttr( "sodipodi:revolution" );
135 object->readAttr( "sodipodi:radius" );
136 object->readAttr( "sodipodi:argument" );
137 object->readAttr( "sodipodi:t0" );
138 }
140 /**
141 * Virtual write: write spiral attributes to corresponding repr.
142 */
143 static Inkscape::XML::Node *
144 sp_spiral_write (SPObject *object, Inkscape::XML::Document *xml_doc, Inkscape::XML::Node *repr, guint flags)
145 {
146 SPSpiral *spiral = SP_SPIRAL (object);
148 if ((flags & SP_OBJECT_WRITE_BUILD) && !repr) {
149 repr = xml_doc->createElement("svg:path");
150 }
152 if (flags & SP_OBJECT_WRITE_EXT) {
153 /* Fixme: we may replace these attributes by
154 * sodipodi:spiral="cx cy exp revo rad arg t0"
155 */
156 repr->setAttribute("sodipodi:type", "spiral");
157 sp_repr_set_svg_double(repr, "sodipodi:cx", spiral->cx);
158 sp_repr_set_svg_double(repr, "sodipodi:cy", spiral->cy);
159 sp_repr_set_svg_double(repr, "sodipodi:expansion", spiral->exp);
160 sp_repr_set_svg_double(repr, "sodipodi:revolution", spiral->revo);
161 sp_repr_set_svg_double(repr, "sodipodi:radius", spiral->rad);
162 sp_repr_set_svg_double(repr, "sodipodi:argument", spiral->arg);
163 sp_repr_set_svg_double(repr, "sodipodi:t0", spiral->t0);
164 }
166 // make sure the curve is rebuilt with all up-to-date parameters
167 sp_spiral_set_shape ((SPShape *) spiral);
169 //Duplicate the path
170 SPCurve *curve = ((SPShape *) spiral)->curve;
171 //Nulls might be possible if this called iteratively
172 if ( !curve ) {
173 //g_warning("sp_spiral_write(): No path to copy\n");
174 return NULL;
175 }
176 char *d = sp_svg_write_path ( curve->get_pathvector() );
177 repr->setAttribute("d", d);
178 g_free (d);
180 if (((SPObjectClass *) (parent_class))->write)
181 ((SPObjectClass *) (parent_class))->write (object, xml_doc, repr, flags | SP_SHAPE_WRITE_PATH);
183 return repr;
184 }
186 /**
187 * Virtual set: change spiral object attribute.
188 */
189 static void
190 sp_spiral_set (SPObject *object, unsigned int key, const gchar *value)
191 {
192 SPSpiral *spiral;
193 SPShape *shape;
195 spiral = SP_SPIRAL (object);
196 shape = SP_SHAPE (object);
198 /// \todo fixme: we should really collect updates
199 switch (key) {
200 case SP_ATTR_SODIPODI_CX:
201 if (!sp_svg_length_read_computed_absolute (value, &spiral->cx)) {
202 spiral->cx = 0.0;
203 }
204 object->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
205 break;
206 case SP_ATTR_SODIPODI_CY:
207 if (!sp_svg_length_read_computed_absolute (value, &spiral->cy)) {
208 spiral->cy = 0.0;
209 }
210 object->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
211 break;
212 case SP_ATTR_SODIPODI_EXPANSION:
213 if (value) {
214 /** \todo
215 * FIXME: check that value looks like a (finite)
216 * number. Create a routine that uses strtod, and
217 * accepts a default value (if strtod finds an error).
218 * N.B. atof/sscanf/strtod consider "nan" and "inf"
219 * to be valid numbers.
220 */
221 spiral->exp = g_ascii_strtod (value, NULL);
222 spiral->exp = CLAMP (spiral->exp, 0.0, 1000.0);
223 } else {
224 spiral->exp = 1.0;
225 }
226 object->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
227 break;
228 case SP_ATTR_SODIPODI_REVOLUTION:
229 if (value) {
230 spiral->revo = g_ascii_strtod (value, NULL);
231 spiral->revo = CLAMP (spiral->revo, 0.05, 1024.0);
232 } else {
233 spiral->revo = 3.0;
234 }
235 object->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
236 break;
237 case SP_ATTR_SODIPODI_RADIUS:
238 if (!sp_svg_length_read_computed_absolute (value, &spiral->rad)) {
239 spiral->rad = MAX (spiral->rad, 0.001);
240 }
241 object->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
242 break;
243 case SP_ATTR_SODIPODI_ARGUMENT:
244 if (value) {
245 spiral->arg = g_ascii_strtod (value, NULL);
246 /** \todo
247 * FIXME: We still need some bounds on arg, for
248 * numerical reasons. E.g., we don't want inf or NaN,
249 * nor near-infinite numbers. I'm inclined to take
250 * modulo 2*pi. If so, then change the knot editors,
251 * which use atan2 - revo*2*pi, which typically
252 * results in very negative arg.
253 */
254 } else {
255 spiral->arg = 0.0;
256 }
257 object->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
258 break;
259 case SP_ATTR_SODIPODI_T0:
260 if (value) {
261 spiral->t0 = g_ascii_strtod (value, NULL);
262 spiral->t0 = CLAMP (spiral->t0, 0.0, 0.999);
263 /** \todo
264 * Have shared constants for the allowable bounds for
265 * attributes. There was a bug here where we used -1.0
266 * as the minimum (which leads to NaN via, e.g.,
267 * pow(-1.0, 0.5); see sp_spiral_get_xy for
268 * requirements.
269 */
270 } else {
271 spiral->t0 = 0.0;
272 }
273 object->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
274 break;
275 default:
276 if (((SPObjectClass *) parent_class)->set)
277 ((SPObjectClass *) parent_class)->set (object, key, value);
278 break;
279 }
280 }
282 /**
283 * Virtual update callback.
284 */
285 static void
286 sp_spiral_update (SPObject *object, SPCtx *ctx, guint flags)
287 {
288 if (flags & (SP_OBJECT_MODIFIED_FLAG | SP_OBJECT_STYLE_MODIFIED_FLAG | SP_OBJECT_VIEWPORT_MODIFIED_FLAG)) {
289 ((SPShape *) object)->setShape ();
290 }
292 if (((SPObjectClass *) parent_class)->update)
293 ((SPObjectClass *) parent_class)->update (object, ctx, flags);
294 }
296 static void
297 sp_spiral_update_patheffect(SPLPEItem *lpeitem, bool write)
298 {
299 SPShape *shape = (SPShape *) lpeitem;
300 sp_spiral_set_shape(shape);
302 if (write) {
303 Inkscape::XML::Node *repr = SP_OBJECT_REPR(shape);
304 if ( shape->curve != NULL ) {
305 gchar *str = sp_svg_write_path(shape->curve->get_pathvector());
306 repr->setAttribute("d", str);
307 g_free(str);
308 } else {
309 repr->setAttribute("d", NULL);
310 }
311 }
313 ((SPObject *)shape)->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
314 }
316 /**
317 * Return textual description of spiral.
318 */
319 static gchar *
320 sp_spiral_description (SPItem * item)
321 {
322 // TRANSLATORS: since turn count isn't an integer, please adjust the
323 // string as needed to deal with an localized plural forms.
324 return g_strdup_printf (_("<b>Spiral</b> with %3f turns"), SP_SPIRAL(item)->revo);
325 }
328 /**
329 * Fit beziers together to spiral and draw it.
330 *
331 * \pre dstep \> 0.
332 * \pre is_unit_vector(*hat1).
333 * \post is_unit_vector(*hat2).
334 **/
335 static void
336 sp_spiral_fit_and_draw (SPSpiral const *spiral,
337 SPCurve *c,
338 double dstep,
339 Geom::Point darray[],
340 Geom::Point const &hat1,
341 Geom::Point &hat2,
342 double *t)
343 {
344 #define BEZIER_SIZE 4
345 #define FITTING_MAX_BEZIERS 4
346 #define BEZIER_LENGTH (BEZIER_SIZE * FITTING_MAX_BEZIERS)
347 g_assert (dstep > 0);
348 g_assert (is_unit_vector (hat1));
350 Geom::Point bezier[BEZIER_LENGTH];
351 double d;
352 int depth, i;
354 for (d = *t, i = 0; i <= SAMPLE_SIZE; d += dstep, i++) {
355 darray[i] = sp_spiral_get_xy(spiral, d);
357 /* Avoid useless adjacent dups. (Otherwise we can have all of darray filled with
358 the same value, which upsets chord_length_parameterize.) */
359 if ((i != 0)
360 && (darray[i] == darray[i - 1])
361 && (d < 1.0)) {
362 i--;
363 d += dstep;
364 /** We mustn't increase dstep for subsequent values of
365 * i: for large spiral.exp values, rate of growth
366 * increases very rapidly.
367 */
368 /** \todo
369 * Get the function itself to decide what value of d
370 * to use next: ensure that we move at least 0.25 *
371 * stroke width, for example. The derivative (as used
372 * for get_tangent before normalization) would be
373 * useful for estimating the appropriate d value. Or
374 * perhaps just start with a small dstep and scale by
375 * some small number until we move >= 0.25 *
376 * stroke_width. Must revert to the original dstep
377 * value for next iteration to avoid the problem
378 * mentioned above.
379 */
380 }
381 }
383 double const next_t = d - 2 * dstep;
384 /* == t + (SAMPLE_SIZE - 1) * dstep, in absence of dups. */
386 hat2 = -sp_spiral_get_tangent (spiral, next_t);
388 /** \todo
389 * We should use better algorithm to specify maximum error.
390 */
391 depth = Geom::bezier_fit_cubic_full (bezier, NULL, darray, SAMPLE_SIZE,
392 hat1, hat2,
393 SPIRAL_TOLERANCE*SPIRAL_TOLERANCE,
394 FITTING_MAX_BEZIERS);
395 g_assert(depth * BEZIER_SIZE <= gint(G_N_ELEMENTS(bezier)));
396 #ifdef SPIRAL_DEBUG
397 if (*t == spiral->t0 || *t == 1.0)
398 g_print ("[%s] depth=%d, dstep=%g, t0=%g, t=%g, arg=%g\n",
399 debug_state, depth, dstep, spiral->t0, *t, spiral->arg);
400 #endif
401 if (depth != -1) {
402 for (i = 0; i < 4*depth; i += 4) {
403 c->curveto(bezier[i + 1],
404 bezier[i + 2],
405 bezier[i + 3]);
406 }
407 } else {
408 #ifdef SPIRAL_VERBOSE
409 g_print ("cant_fit_cubic: t=%g\n", *t);
410 #endif
411 for (i = 1; i < SAMPLE_SIZE; i++)
412 c->lineto(darray[i]);
413 }
414 *t = next_t;
415 g_assert (is_unit_vector (hat2));
416 }
418 static void
419 sp_spiral_set_shape (SPShape *shape)
420 {
421 SPSpiral *spiral = SP_SPIRAL(shape);
423 if (sp_lpe_item_has_broken_path_effect(SP_LPE_ITEM(shape))) {
424 g_warning ("The spiral shape has unknown LPE on it! Convert to path to make it editable preserving the appearance; editing it as spiral will remove the bad LPE");
425 if (SP_OBJECT_REPR(shape)->attribute("d")) {
426 // unconditionally read the curve from d, if any, to preserve appearance
427 Geom::PathVector pv = sp_svg_read_pathv(SP_OBJECT_REPR(shape)->attribute("d"));
428 SPCurve *cold = new SPCurve(pv);
429 shape->setCurveInsync( cold, TRUE);
430 cold->unref();
431 }
432 return;
433 }
435 Geom::Point darray[SAMPLE_SIZE + 1];
436 double t;
438 SP_OBJECT (spiral)->requestModified(SP_OBJECT_MODIFIED_FLAG);
440 SPCurve *c = new SPCurve ();
442 #ifdef SPIRAL_VERBOSE
443 g_print ("cx=%g, cy=%g, exp=%g, revo=%g, rad=%g, arg=%g, t0=%g\n",
444 spiral->cx,
445 spiral->cy,
446 spiral->exp,
447 spiral->revo,
448 spiral->rad,
449 spiral->arg,
450 spiral->t0);
451 #endif
453 /* Initial moveto. */
454 c->moveto(sp_spiral_get_xy(spiral, spiral->t0));
456 double const tstep = SAMPLE_STEP / spiral->revo;
457 double const dstep = tstep / (SAMPLE_SIZE - 1);
459 Geom::Point hat1 = sp_spiral_get_tangent (spiral, spiral->t0);
460 Geom::Point hat2;
461 for (t = spiral->t0; t < (1.0 - tstep);) {
462 sp_spiral_fit_and_draw (spiral, c, dstep, darray, hat1, hat2, &t);
464 hat1 = -hat2;
465 }
466 if ((1.0 - t) > SP_EPSILON)
467 sp_spiral_fit_and_draw (spiral, c, (1.0 - t)/(SAMPLE_SIZE - 1.0),
468 darray, hat1, hat2, &t);
470 /* Reset the shape'scurve to the "original_curve"
471 * This is very important for LPEs to work properly! (the bbox might be recalculated depending on the curve in shape)*/
472 shape->setCurveInsync( c, TRUE);
473 if (sp_lpe_item_has_path_effect(SP_LPE_ITEM(shape)) && sp_lpe_item_path_effects_enabled(SP_LPE_ITEM(shape))) {
474 SPCurve *c_lpe = c->copy();
475 bool success = sp_lpe_item_perform_path_effect(SP_LPE_ITEM (shape), c_lpe);
476 if (success) {
477 shape->setCurveInsync( c_lpe, TRUE);
478 }
479 c_lpe->unref();
480 }
481 c->unref();
482 }
484 /**
485 * Set spiral properties and update display.
486 */
487 void
488 sp_spiral_position_set (SPSpiral *spiral,
489 gdouble cx,
490 gdouble cy,
491 gdouble exp,
492 gdouble revo,
493 gdouble rad,
494 gdouble arg,
495 gdouble t0)
496 {
497 g_return_if_fail (spiral != NULL);
498 g_return_if_fail (SP_IS_SPIRAL (spiral));
500 /** \todo
501 * Consider applying CLAMP or adding in-bounds assertions for
502 * some of these parameters.
503 */
504 spiral->cx = cx;
505 spiral->cy = cy;
506 spiral->exp = exp;
507 spiral->revo = revo;
508 spiral->rad = MAX (rad, 0.0);
509 spiral->arg = arg;
510 spiral->t0 = CLAMP(t0, 0.0, 0.999);
512 ((SPObject *)spiral)->requestDisplayUpdate(SP_OBJECT_MODIFIED_FLAG);
513 }
515 /**
516 * Virtual snappoints callback.
517 */
518 static void sp_spiral_snappoints(SPItem const *item, std::vector<Inkscape::SnapCandidatePoint> &p, Inkscape::SnapPreferences const *snapprefs)
519 {
520 // We will determine the spiral's midpoint ourselves, instead of trusting on the base class
521 // Therefore setSnapObjectMidpoints() is set to false temporarily
522 Inkscape::SnapPreferences local_snapprefs = *snapprefs;
523 local_snapprefs.setSnapObjectMidpoints(false);
525 if (((SPItemClass *) parent_class)->snappoints) {
526 ((SPItemClass *) parent_class)->snappoints (item, p, &local_snapprefs);
527 }
529 // Help enforcing strict snapping, i.e. only return nodes when we're snapping nodes to nodes or a guide to nodes
530 if (!(snapprefs->getSnapModeNode() || snapprefs->getSnapModeGuide())) {
531 return;
532 }
534 if (snapprefs->getSnapObjectMidpoints()) {
535 Geom::Matrix const i2d (item->i2d_affine ());
536 SPSpiral *spiral = SP_SPIRAL(item);
537 p.push_back(Inkscape::SnapCandidatePoint(Geom::Point(spiral->cx, spiral->cy) * i2d, Inkscape::SNAPSOURCE_OBJECT_MIDPOINT, Inkscape::SNAPTARGET_OBJECT_MIDPOINT));
538 // This point is the start-point of the spiral, which is also returned when _snap_to_itemnode has been set
539 // in the object snapper. In that case we will get a duplicate!
540 }
541 }
543 /**
544 * Return one of the points on the spiral.
545 *
546 * \param t specifies how far along the spiral.
547 * \pre \a t in [0.0, 2.03]. (It doesn't make sense for t to be much more
548 * than 1.0, though some callers go slightly beyond 1.0 for curve-fitting
549 * purposes.)
550 */
551 Geom::Point sp_spiral_get_xy (SPSpiral const *spiral, gdouble t)
552 {
553 g_assert (spiral != NULL);
554 g_assert (SP_IS_SPIRAL(spiral));
555 g_assert (spiral->exp >= 0.0);
556 /* Otherwise we get NaN for t==0. */
557 g_assert (spiral->exp <= 1000.0);
558 /* Anything much more results in infinities. Even allowing 1000 is somewhat overkill. */
559 g_assert (t >= 0.0);
560 /* Any callers passing -ve t will have a bug for non-integral values of exp. */
562 double const rad = spiral->rad * pow(t, (double) spiral->exp);
563 double const arg = 2.0 * M_PI * spiral->revo * t + spiral->arg;
565 return Geom::Point(rad * cos (arg) + spiral->cx,
566 rad * sin (arg) + spiral->cy);
567 }
570 /**
571 * Returns the derivative of sp_spiral_get_xy with respect to t,
572 * scaled to a unit vector.
573 *
574 * \pre spiral != 0.
575 * \pre 0 \<= t.
576 * \pre p != NULL.
577 * \post is_unit_vector(*p).
578 */
579 static Geom::Point
580 sp_spiral_get_tangent (SPSpiral const *spiral, gdouble t)
581 {
582 Geom::Point ret(1.0, 0.0);
583 g_return_val_if_fail (( ( spiral != NULL )
584 && SP_IS_SPIRAL(spiral) ),
585 ret);
586 g_assert (t >= 0.0);
587 g_assert (spiral->exp >= 0.0);
588 /* See above for comments on these assertions. */
590 double const t_scaled = 2.0 * M_PI * spiral->revo * t;
591 double const arg = t_scaled + spiral->arg;
592 double const s = sin (arg);
593 double const c = cos (arg);
595 if (spiral->exp == 0.0) {
596 ret = Geom::Point(-s, c);
597 } else if (t_scaled == 0.0) {
598 ret = Geom::Point(c, s);
599 } else {
600 Geom::Point unrotated(spiral->exp, t_scaled);
601 double const s_len = L2 (unrotated);
602 g_assert (s_len != 0);
603 /** \todo
604 * Check that this isn't being too hopeful of the hypot
605 * function. E.g. test with numbers around 2**-1070
606 * (denormalized numbers), preferably on a few different
607 * platforms. However, njh says that the usual implementation
608 * does handle both very big and very small numbers.
609 */
610 unrotated /= s_len;
612 /* ret = spiral->exp * (c, s) + t_scaled * (-s, c);
613 alternatively ret = (spiral->exp, t_scaled) * (( c, s),
614 (-s, c)).*/
615 ret = Geom::Point(dot(unrotated, Geom::Point(c, -s)),
616 dot(unrotated, Geom::Point(s, c)));
617 /* ret should already be approximately normalized: the
618 matrix ((c, -s), (s, c)) is orthogonal (it just
619 rotates by arg), and unrotated has been normalized,
620 so ret is already of unit length other than numerical
621 error in the above matrix multiplication. */
623 /** \todo
624 * I haven't checked how important it is for ret to be very
625 * near unit length; we could get rid of the below.
626 */
628 ret.normalize();
629 /* Proof that ret length is non-zero: see above. (Should be near 1.) */
630 }
632 g_assert (is_unit_vector (ret));
633 return ret;
634 }
636 /**
637 * Compute rad and/or arg for point on spiral.
638 */
639 void
640 sp_spiral_get_polar (SPSpiral const *spiral, gdouble t, gdouble *rad, gdouble *arg)
641 {
642 g_return_if_fail (spiral != NULL);
643 g_return_if_fail (SP_IS_SPIRAL(spiral));
645 if (rad)
646 *rad = spiral->rad * pow(t, (double) spiral->exp);
647 if (arg)
648 *arg = 2.0 * M_PI * spiral->revo * t + spiral->arg;
649 }
651 /**
652 * Return true if spiral has properties that make it invalid.
653 */
654 bool
655 sp_spiral_is_invalid (SPSpiral const *spiral)
656 {
657 gdouble rad;
659 sp_spiral_get_polar (spiral, 0.0, &rad, NULL);
660 if (rad < 0.0 || rad > SP_HUGE) {
661 g_print ("rad(t=0)=%g\n", rad);
662 return TRUE;
663 }
664 sp_spiral_get_polar (spiral, 1.0, &rad, NULL);
665 if (rad < 0.0 || rad > SP_HUGE) {
666 g_print ("rad(t=1)=%g\n", rad);
667 return TRUE;
668 }
669 return FALSE;
670 }
672 /*
673 Local Variables:
674 mode:c++
675 c-file-style:"stroustrup"
676 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
677 indent-tabs-mode:nil
678 fill-column:99
679 End:
680 */
681 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :