1 #define __SP_DESKTOP_SNAP_C__
3 /**
4 * \file snap.cpp
5 * \brief SnapManager class.
6 *
7 * Authors:
8 * Lauris Kaplinski <lauris@kaplinski.com>
9 * Frank Felfe <innerspace@iname.com>
10 * Nathan Hurst <njh@njhurst.com>
11 * Carl Hetherington <inkscape@carlh.net>
12 *
13 * Copyright (C) 2006-2007 Johan Engelen <johan@shouraizou.nl>
14 * Copyrigth (C) 2004 Nathan Hurst
15 * Copyright (C) 1999-2002 Authors
16 *
17 * Released under GNU GPL, read the file 'COPYING' for more information
18 */
20 #include <utility>
22 #include "sp-namedview.h"
23 #include "snap.h"
24 #include "snapped-line.h"
26 #include <libnr/nr-point-fns.h>
27 #include <libnr/nr-scale-ops.h>
28 #include <libnr/nr-values.h>
30 #include "display/canvas-grid.h"
32 #include "inkscape.h"
33 #include "desktop.h"
34 #include "sp-guide.h"
35 using std::vector;
37 /**
38 * Construct a SnapManager for a SPNamedView.
39 *
40 * \param v `Owning' SPNamedView.
41 */
43 SnapManager::SnapManager(SPNamedView const *v) :
44 guide(v, 0),
45 object(v, 0),
46 _named_view(v),
47 _include_item_center(false),
48 _snap_enabled_globally(true)
49 {
50 }
53 /**
54 * \return List of snappers that we use.
55 */
56 SnapManager::SnapperList
57 SnapManager::getSnappers() const
58 {
59 SnapManager::SnapperList s;
60 s.push_back(&guide);
61 s.push_back(&object);
63 SnapManager::SnapperList gs = getGridSnappers();
64 s.splice(s.begin(), gs);
66 return s;
67 }
69 /**
70 * \return List of gridsnappers that we use.
71 */
72 SnapManager::SnapperList
73 SnapManager::getGridSnappers() const
74 {
75 SnapperList s;
77 //FIXME: this code should actually do this: add new grid snappers that are active for this desktop. now it just adds all gridsnappers
78 SPDesktop* desktop = SP_ACTIVE_DESKTOP;
79 if (desktop && desktop->gridsEnabled()) {
80 for ( GSList const *l = _named_view->grids; l != NULL; l = l->next) {
81 Inkscape::CanvasGrid *grid = (Inkscape::CanvasGrid*) l->data;
82 s.push_back(grid->snapper);
83 }
84 }
86 return s;
87 }
89 /**
90 * \return true if one of the snappers will try to snap something.
91 */
93 bool SnapManager::SomeSnapperMightSnap() const
94 {
95 if (!_snap_enabled_globally) {
96 return false;
97 }
99 SnapperList const s = getSnappers();
100 SnapperList::const_iterator i = s.begin();
101 while (i != s.end() && (*i)->ThisSnapperMightSnap() == false) {
102 i++;
103 }
105 return (i != s.end());
106 }
108 /*
109 * The snappers have too many parameters to adjust individually. Therefore only
110 * two snapping modes are presented to the user: snapping bounding box corners (to
111 * other bounding boxes, grids or guides), and/or snapping nodes (to other nodes,
112 * paths, grids or guides). To select either of these modes (or both), use the
113 * methods defined below: setSnapModeBBox() and setSnapModeNode().
114 *
115 * */
118 void SnapManager::setSnapModeBBox(bool enabled)
119 {
120 //The default values are being set in sp_namedview_set() (in sp-namedview.cpp)
121 guide.setSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX, enabled);
123 for ( GSList const *l = _named_view->grids; l != NULL; l = l->next) {
124 Inkscape::CanvasGrid *grid = (Inkscape::CanvasGrid*) l->data;
125 grid->snapper->setSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX, enabled);
126 }
128 object.setSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX, enabled);
129 //object.setSnapToBBoxNode(enabled); // On second thought, these should be controlled
130 //object.setSnapToBBoxPath(enabled); // separately by the snapping prefs dialog
131 object.setStrictSnapping(true); //don't snap bboxes to nodes/paths and vice versa
132 }
134 bool SnapManager::getSnapModeBBox() const
135 {
136 return guide.getSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX);
137 }
139 void SnapManager::setSnapModeNode(bool enabled)
140 {
141 guide.setSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE, enabled);
143 for ( GSList const *l = _named_view->grids; l != NULL; l = l->next) {
144 Inkscape::CanvasGrid *grid = (Inkscape::CanvasGrid*) l->data;
145 grid->snapper->setSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE, enabled);
146 }
148 object.setSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE, enabled);
149 //object.setSnapToItemNode(enabled); // On second thought, these should be controlled
150 //object.setSnapToItemPath(enabled); // separately by the snapping prefs dialog
151 object.setStrictSnapping(true);
152 }
154 bool SnapManager::getSnapModeNode() const
155 {
156 return guide.getSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE);
157 }
159 void SnapManager::setSnapModeGuide(bool enabled)
160 {
161 object.setSnapFrom(Inkscape::Snapper::SNAPPOINT_GUIDE, enabled);
162 }
164 bool SnapManager::getSnapModeGuide() const
165 {
166 return object.getSnapFrom(Inkscape::Snapper::SNAPPOINT_GUIDE);
167 }
169 /**
170 * Try to snap a point to any interested snappers.
171 *
172 * \param t Type of point.
173 * \param p Point.
174 * \param it Item to ignore when snapping.
175 * \return Snapped point.
176 */
178 Inkscape::SnappedPoint SnapManager::freeSnap(Inkscape::Snapper::PointType t,
179 NR::Point const &p,
180 SPItem const *it) const
182 {
183 std::list<SPItem const *> lit;
184 lit.push_back(it);
186 std::vector<NR::Point> points_to_snap;
187 points_to_snap.push_back(p);
189 return freeSnap(t, p, true, points_to_snap, lit);
190 }
192 /**
193 * Try to snap a point to any of the specified snappers.
194 *
195 * \param t Type of point.
196 * \param p Point.
197 * \param first_point If true then this point is the first one from a whole bunch of points
198 * \param points_to_snap The whole bunch of points, all from the same selection and having the same transformation
199 * \param it List of items to ignore when snapping.
200 * \param snappers List of snappers to try to snap to
201 * \return Snapped point.
202 */
204 Inkscape::SnappedPoint SnapManager::freeSnap(Inkscape::Snapper::PointType t,
205 NR::Point const &p,
206 bool const &first_point,
207 std::vector<NR::Point> &points_to_snap,
208 std::list<SPItem const *> const &it) const
209 {
211 SnappedConstraints sc;
213 SnapperList const snappers = getSnappers();
215 for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); i++) {
216 (*i)->freeSnap(sc, t, p, first_point, points_to_snap, it);
217 }
219 return findBestSnap(p, sc, false);
220 }
222 /**
223 * Try to snap a point to any interested snappers. A snap will only occur along
224 * a line described by a Inkscape::Snapper::ConstraintLine.
225 *
226 * \param t Type of point.
227 * \param p Point.
228 * \param c Constraint line.
229 * \param it Item to ignore when snapping.
230 * \return Snapped point.
231 */
233 Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::Snapper::PointType t,
234 NR::Point const &p,
235 Inkscape::Snapper::ConstraintLine const &c,
236 SPItem const *it) const
237 {
238 std::list<SPItem const *> lit;
239 lit.push_back(it);
241 std::vector<NR::Point> points_to_snap;
242 points_to_snap.push_back(p);
244 return constrainedSnap(t, p, true, points_to_snap, c, lit);
245 }
249 /**
250 * Try to snap a point to any interested snappers. A snap will only occur along
251 * a line described by a Inkscape::Snapper::ConstraintLine.
252 *
253 * \param t Type of point.
254 * \param p Point.
255 * \param first_point If true then this point is the first one from a whole bunch of points
256 * \param points_to_snap The whole bunch of points, all from the same selection and having the same transformation
257 * \param c Constraint line.
258 * \param it List of items to ignore when snapping.
259 * \return Snapped point.
260 */
262 Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::Snapper::PointType t,
263 NR::Point const &p,
264 bool const &first_point,
265 std::vector<NR::Point> &points_to_snap,
266 Inkscape::Snapper::ConstraintLine const &c,
267 std::list<SPItem const *> const &it) const
268 {
270 SnappedConstraints sc;
272 SnapperList const snappers = getSnappers();
273 for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); i++) {
274 (*i)->constrainedSnap(sc, t, p, first_point, points_to_snap, c, it);
275 }
277 return findBestSnap(p, sc, true);
278 }
280 Inkscape::SnappedPoint SnapManager::guideSnap(NR::Point const &p,
281 NR::Point const &guide_normal) const
282 {
284 // This method is used to snap a guide to nodes, while dragging the guide around
285 Inkscape::ObjectSnapper::DimensionToSnap snap_dim;
286 if (guide_normal == component_vectors[NR::Y]) {
287 snap_dim = Inkscape::ObjectSnapper::SNAP_Y;
288 } else if (guide_normal == component_vectors[NR::X]) {
289 snap_dim = Inkscape::ObjectSnapper::SNAP_X;
290 } else {
291 g_warning("WARNING: snapping of angled guides is not supported yet!");
292 // this is because _snapnodes, called in object.guideSnap, cannot only handle
293 // vertical or horizontal lines for now....
294 // Rotating an agled guide will require some additional code, as it would be great to
295 // have it rotate around a snapped point
296 snap_dim = Inkscape::ObjectSnapper::SNAP_XY;
297 }
299 SnappedConstraints sc;
300 object.guideSnap(sc, p, snap_dim);
302 return findBestSnap(p, sc, false);
303 }
306 /**
307 * Main internal snapping method, which is called by the other, friendlier, public
308 * methods. It's a bit hairy as it has lots of parameters, but it saves on a lot
309 * of duplicated code.
310 *
311 * \param type Type of points being snapped.
312 * \param points List of points to snap.
313 * \param ignore List of items to ignore while snapping.
314 * \param constrained true if the snap is constrained.
315 * \param constraint Constraint line to use, if `constrained' is true, otherwise undefined.
316 * \param transformation_type Type of transformation to apply to points before trying to snap them.
317 * \param transformation Description of the transformation; details depend on the type.
318 * \param origin Origin of the transformation, if applicable.
319 * \param dim Dimension of the transformation, if applicable.
320 * \param uniform true if the transformation should be uniform, if applicable.
321 */
323 std::pair<NR::Point, bool> SnapManager::_snapTransformed(
324 Inkscape::Snapper::PointType type,
325 std::vector<NR::Point> const &points,
326 std::list<SPItem const *> const &ignore,
327 bool constrained,
328 Inkscape::Snapper::ConstraintLine const &constraint,
329 Transformation transformation_type,
330 NR::Point const &transformation,
331 NR::Point const &origin,
332 NR::Dim2 dim,
333 bool uniform) const
334 {
335 /* We have a list of points, which we are proposing to transform in some way. We need to see
336 ** if any of these points, when transformed, snap to anything. If they do, we return the
337 ** appropriate transformation with `true'; otherwise we return the original scale with `false'.
338 */
340 /* Quick check to see if we have any snappers that are enabled
341 ** Also used to globally disable all snapping
342 */
343 if (SomeSnapperMightSnap() == false) {
344 return std::make_pair(transformation, false);
345 }
347 std::vector<NR::Point> transformed_points;
349 for (std::vector<NR::Point>::const_iterator i = points.begin(); i != points.end(); i++) {
351 /* Work out the transformed version of this point */
352 NR::Point transformed;
353 switch (transformation_type) {
354 case TRANSLATION:
355 transformed = *i + transformation;
356 break;
357 case SCALE:
358 transformed = ((*i - origin) * NR::scale(transformation[NR::X], transformation[NR::Y])) + origin;
359 break;
360 case STRETCH:
361 {
362 NR::scale s(1, 1);
363 if (uniform)
364 s[NR::X] = s[NR::Y] = transformation[dim];
365 else {
366 s[dim] = transformation[dim];
367 s[1 - dim] = 1;
368 }
369 transformed = ((*i - origin) * s) + origin;
370 break;
371 }
372 case SKEW:
373 transformed = *i;
374 transformed[dim] += transformation[dim] * ((*i)[1 - dim] - origin[1 - dim]);
375 break;
376 default:
377 g_assert_not_reached();
378 }
380 // add the current transformed point to the box hulling all transformed points
381 transformed_points.push_back(transformed);
382 }
384 /* The current best transformation */
385 NR::Point best_transformation = transformation;
387 /* The current best metric for the best transformation; lower is better, NR_HUGE
388 ** means that we haven't snapped anything.
389 */
390 NR::Coord best_metric = NR_HUGE;
391 NR::Coord best_second_metric = NR_HUGE;
392 bool best_at_intersection = false;
394 std::vector<NR::Point>::const_iterator j = transformed_points.begin();
396 //std::cout << std::endl;
398 for (std::vector<NR::Point>::const_iterator i = points.begin(); i != points.end(); i++) {
400 /* Snap it */
401 Inkscape::SnappedPoint const snapped = constrained ?
402 constrainedSnap(type, *j, i == points.begin(), transformed_points, constraint, ignore) : freeSnap(type, *j, i == points.begin(), transformed_points, ignore);
404 NR::Point result;
405 NR::Coord metric = NR_HUGE;
406 NR::Coord second_metric = NR_HUGE;
408 if (snapped.getDistance() < NR_HUGE) {
409 /* We snapped. Find the transformation that describes where the snapped point has
410 ** ended up, and also the metric for this transformation.
411 */
412 switch (transformation_type) {
413 case TRANSLATION:
414 result = snapped.getPoint() - *i;
415 /* Consider the case in which a box is almost aligned with a grid in both
416 * horizontal and vertical directions. The distance to the intersection of
417 * the grid lines will always be larger then the distance to a single grid
418 * line. If we prefer snapping to an intersection instead of to a single
419 * grid line, then we cannot use "metric = NR::L2(result)". Therefore the
420 * snapped distance will be used as a metric. Please note that the snapped
421 * distance is defined as the distance to the nearest line of the intersection,
422 * and not to the intersection itself!
423 */
424 metric = snapped.getDistance(); //used to be: metric = NR::L2(result);
425 second_metric = snapped.getSecondDistance();
426 break;
427 case SCALE:
428 {
429 NR::Point const a = (snapped.getPoint() - origin);
430 NR::Point const b = (*i - origin);
431 result = NR::Point(a[NR::X] / b[NR::X], a[NR::Y] / b[NR::Y]);
432 metric = std::abs(NR::L2(result) - NR::L2(transformation));
433 break;
434 }
435 case STRETCH:
436 {
437 for (int a = 0; a < 2; a++) {
438 if (uniform || a == dim) {
439 result[a] = (snapped.getPoint()[dim] - origin[dim]) / ((*i)[dim] - origin[dim]);
440 } else {
441 result[a] = 1;
442 }
443 }
444 metric = std::abs(result[dim] - transformation[dim]);
445 break;
446 }
447 case SKEW:
448 result[dim] = (snapped.getPoint()[dim] - (*i)[dim]) / ((*i)[1 - dim] - origin[1 - dim]);
449 metric = std::abs(result[dim] - transformation[dim]);
450 break;
451 default:
452 g_assert_not_reached();
453 }
455 /* Note it if it's the best so far */
456 bool const c1 = metric < best_metric;
457 bool const c2 = metric == best_metric && snapped.getAtIntersection() == true && best_at_intersection == false;
458 bool const c3a = metric == best_metric && snapped.getAtIntersection() == true && best_at_intersection == true;
459 bool const c3b = second_metric < best_second_metric;
461 if (c1 || c2 || c3a && c3b) {
462 best_transformation = result;
463 best_metric = metric;
464 best_second_metric = second_metric;
465 best_at_intersection = snapped.getAtIntersection();
466 //std::cout << "SEL ";
467 } //else { std::cout << " ";}
468 }
470 //std::cout << "P_orig = " << (*i) << " | metric = " << metric << " | distance = " << snapped.getDistance() << " | second metric = " << second_metric << " | P_snap = " << snapped.getPoint() << std::endl;
471 j++;
472 }
474 // Using " < 1e6" instead of " < NR_HUGE" for catching some rounding errors
475 // These rounding errors might be caused by NRRects, see bug #1584301
476 return std::make_pair(best_transformation, best_metric < 1e6);
477 }
480 /**
481 * Try to snap a list of points to any interested snappers after they have undergone
482 * a translation.
483 *
484 * \param t Type of points.
485 * \param p Points.
486 * \param it List of items to ignore when snapping.
487 * \param tr Proposed translation.
488 * \return Snapped translation, if a snap occurred, and a flag indicating whether a snap occurred.
489 */
491 std::pair<NR::Point, bool> SnapManager::freeSnapTranslation(Inkscape::Snapper::PointType t,
492 std::vector<NR::Point> const &p,
493 std::list<SPItem const *> const &it,
494 NR::Point const &tr) const
495 {
496 return _snapTransformed(
497 t, p, it, false, NR::Point(), TRANSLATION, tr, NR::Point(), NR::X, false
498 );
499 }
502 /**
503 * Try to snap a list of points to any interested snappers after they have undergone a
504 * translation. A snap will only occur along a line described by a
505 * Inkscape::Snapper::ConstraintLine.
506 *
507 * \param t Type of points.
508 * \param p Points.
509 * \param it List of items to ignore when snapping.
510 * \param c Constraint line.
511 * \param tr Proposed translation.
512 * \return Snapped translation, if a snap occurred, and a flag indicating whether a snap occurred.
513 */
515 std::pair<NR::Point, bool> SnapManager::constrainedSnapTranslation(Inkscape::Snapper::PointType t,
516 std::vector<NR::Point> const &p,
517 std::list<SPItem const *> const &it,
518 Inkscape::Snapper::ConstraintLine const &c,
519 NR::Point const &tr) const
520 {
521 return _snapTransformed(
522 t, p, it, true, c, TRANSLATION, tr, NR::Point(), NR::X, false
523 );
524 }
527 /**
528 * Try to snap a list of points to any interested snappers after they have undergone
529 * a scale.
530 *
531 * \param t Type of points.
532 * \param p Points.
533 * \param it List of items to ignore when snapping.
534 * \param s Proposed scale.
535 * \param o Origin of proposed scale.
536 * \return Snapped scale, if a snap occurred, and a flag indicating whether a snap occurred.
537 */
539 std::pair<NR::scale, bool> SnapManager::freeSnapScale(Inkscape::Snapper::PointType t,
540 std::vector<NR::Point> const &p,
541 std::list<SPItem const *> const &it,
542 NR::scale const &s,
543 NR::Point const &o) const
544 {
545 return _snapTransformed(
546 t, p, it, false, NR::Point(), SCALE, NR::Point(s[NR::X], s[NR::Y]), o, NR::X, false
547 );
548 }
551 /**
552 * Try to snap a list of points to any interested snappers after they have undergone
553 * a scale. A snap will only occur along a line described by a
554 * Inkscape::Snapper::ConstraintLine.
555 *
556 * \param t Type of points.
557 * \param p Points.
558 * \param it List of items to ignore when snapping.
559 * \param s Proposed scale.
560 * \param o Origin of proposed scale.
561 * \return Snapped scale, if a snap occurred, and a flag indicating whether a snap occurred.
562 */
564 std::pair<NR::scale, bool> SnapManager::constrainedSnapScale(Inkscape::Snapper::PointType t,
565 std::vector<NR::Point> const &p,
566 std::list<SPItem const *> const &it,
567 Inkscape::Snapper::ConstraintLine const &c,
568 NR::scale const &s,
569 NR::Point const &o) const
570 {
571 return _snapTransformed(
572 t, p, it, true, c, SCALE, NR::Point(s[NR::X], s[NR::Y]), o, NR::X, false
573 );
574 }
577 /**
578 * Try to snap a list of points to any interested snappers after they have undergone
579 * a stretch.
580 *
581 * \param t Type of points.
582 * \param p Points.
583 * \param it List of items to ignore when snapping.
584 * \param s Proposed stretch.
585 * \param o Origin of proposed stretch.
586 * \param d Dimension in which to apply proposed stretch.
587 * \param u true if the stretch should be uniform (ie to be applied equally in both dimensions)
588 * \return Snapped stretch, if a snap occurred, and a flag indicating whether a snap occurred.
589 */
591 std::pair<NR::Coord, bool> SnapManager::freeSnapStretch(Inkscape::Snapper::PointType t,
592 std::vector<NR::Point> const &p,
593 std::list<SPItem const *> const &it,
594 NR::Coord const &s,
595 NR::Point const &o,
596 NR::Dim2 d,
597 bool u) const
598 {
599 std::pair<NR::Point, bool> const r = _snapTransformed(
600 t, p, it, false, NR::Point(), STRETCH, NR::Point(s, s), o, d, u
601 );
603 return std::make_pair(r.first[d], r.second);
604 }
607 /**
608 * Try to snap a list of points to any interested snappers after they have undergone
609 * a skew.
610 *
611 * \param t Type of points.
612 * \param p Points.
613 * \param it List of items to ignore when snapping.
614 * \param s Proposed skew.
615 * \param o Origin of proposed skew.
616 * \param d Dimension in which to apply proposed skew.
617 * \return Snapped skew, if a snap occurred, and a flag indicating whether a snap occurred.
618 */
620 std::pair<NR::Coord, bool> SnapManager::freeSnapSkew(Inkscape::Snapper::PointType t,
621 std::vector<NR::Point> const &p,
622 std::list<SPItem const *> const &it,
623 NR::Coord const &s,
624 NR::Point const &o,
625 NR::Dim2 d) const
626 {
627 std::pair<NR::Point, bool> const r = _snapTransformed(
628 t, p, it, false, NR::Point(), SKEW, NR::Point(s, s), o, d, false
629 );
631 return std::make_pair(r.first[d], r.second);
632 }
634 Inkscape::SnappedPoint SnapManager::findBestSnap(NR::Point const &p, SnappedConstraints &sc, bool constrained) const
635 {
636 NR::Coord const guide_sens = guide.getDistance();
637 NR::Coord grid_sens = 0;
639 SnapManager::SnapperList const gs = getGridSnappers();
640 SnapperList::const_iterator i = gs.begin();
641 if (i != gs.end()) {
642 grid_sens = (*i)->getDistance();
643 }
645 // Store all snappoints, optionally together with their specific snapping range
646 std::list<std::pair<Inkscape::SnappedPoint, NR::Coord> > sp_list;
647 // Most of these snapped points are already within the snapping range, because
648 // they have already been filtered by their respective snappers. In that case
649 // we can set the snapping range to NR_HUGE here. If however we're looking at
650 // intersections of e.g. a grid and guide line, then we'll have to determine
651 // once again whether we're within snapping range. In this case we will set
652 // the snapping range to e.g. min(guide_sens, grid_sens)
654 // search for the closest snapped point
655 Inkscape::SnappedPoint closestPoint;
656 if (getClosestSP(sc.points, closestPoint)) {
657 sp_list.push_back(std::make_pair(closestPoint, NR_HUGE));
658 }
660 // search for the closest snapped line segment
661 Inkscape::SnappedLineSegment closestLineSegment;
662 if (getClosestSLS(sc.lines, closestLineSegment)) {
663 sp_list.push_back(std::make_pair(Inkscape::SnappedPoint(closestLineSegment), NR_HUGE));
664 }
666 if (_intersectionLS) {
667 // search for the closest snapped intersection of line segments
668 Inkscape::SnappedPoint closestLineSegmentIntersection;
669 if (getClosestIntersectionSLS(sc.lines, closestLineSegmentIntersection)) {
670 sp_list.push_back(std::make_pair(closestLineSegmentIntersection, NR_HUGE));
671 }
672 }
674 // search for the closest snapped grid line
675 Inkscape::SnappedLine closestGridLine;
676 if (getClosestSL(sc.grid_lines, closestGridLine)) {
677 sp_list.push_back(std::make_pair(Inkscape::SnappedPoint(closestGridLine), NR_HUGE));
678 }
680 // search for the closest snapped guide line
681 Inkscape::SnappedLine closestGuideLine;
682 if (getClosestSL(sc.guide_lines, closestGuideLine)) {
683 sp_list.push_back(std::make_pair(Inkscape::SnappedPoint(closestGuideLine), NR_HUGE));
684 }
686 // When freely snapping to a grid/guide/path, only one degree of freedom is eliminated
687 // Therefore we will try get fully constrained by finding an intersection with another grid/guide/path
689 // When doing a constrained snap however, we're already at an intersection of the constrained line and
690 // the grid/guide/path we're snapping to. This snappoint is therefore fully constrained, so there's
691 // no need to look for additional intersections
692 if (!constrained) {
693 // search for the closest snapped intersection of grid lines
694 Inkscape::SnappedPoint closestGridPoint;
695 if (getClosestIntersectionSL(sc.grid_lines, closestGridPoint)) {
696 sp_list.push_back(std::make_pair(closestGridPoint, NR_HUGE));
697 }
699 // search for the closest snapped intersection of guide lines
700 Inkscape::SnappedPoint closestGuidePoint;
701 if (getClosestIntersectionSL(sc.guide_lines, closestGuidePoint)) {
702 sp_list.push_back(std::make_pair(closestGuidePoint, NR_HUGE));
703 }
705 // search for the closest snapped intersection of grid with guide lines
706 if (_intersectionGG) {
707 Inkscape::SnappedPoint closestGridGuidePoint;
708 if (getClosestIntersectionSL(sc.grid_lines, sc.guide_lines, closestGridGuidePoint)) {
709 sp_list.push_back(std::make_pair(closestGridGuidePoint, std::min(guide_sens, grid_sens)));
710 }
711 }
712 }
714 // now let's see which snapped point gets a thumbs up
715 Inkscape::SnappedPoint bestPoint(p, NR_HUGE);
716 for (std::list<std::pair<Inkscape::SnappedPoint, NR::Coord> >::const_iterator i = sp_list.begin(); i != sp_list.end(); i++) {
717 // first find out if this snapped point is within snapping range
718 if ((*i).first.getDistance() <= (*i).second) {
719 // if it's the first point
720 bool c1 = (i == sp_list.begin());
721 // or, if it's closer
722 bool c2 = (*i).first.getDistance() < bestPoint.getDistance();
723 // or, if it's just as close then consider the second distance
724 // (which is only relevant for points at an intersection)
725 bool c3a = ((*i).first.getDistance() == bestPoint.getDistance());
726 bool c3b = (*i).first.getSecondDistance() < bestPoint.getSecondDistance();
727 // then prefer this point over the previous one
728 if (c1 || c2 || c3a && c3b) {
729 bestPoint = (*i).first;
730 }
731 }
732 }
733 return bestPoint;
734 }
736 /*
737 Local Variables:
738 mode:c++
739 c-file-style:"stroustrup"
740 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
741 indent-tabs-mode:nil
742 fill-column:99
743 End:
744 */
745 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :