#define __SP_DESKTOP_SNAP_C__ /** * \file snap.cpp * \brief SnapManager class. * * Authors: * Lauris Kaplinski <lauris@kaplinski.com> * Frank Felfe <innerspace@iname.com> * Nathan Hurst <njh@njhurst.com> * Carl Hetherington <inkscape@carlh.net> * Diederik van Lierop <mail@diedenrezi.nl> * * Copyright (C) 2006-2007 Johan Engelen <johan@shouraizou.nl> * Copyrigth (C) 2004 Nathan Hurst * Copyright (C) 1999-2002 Authors * * Released under GNU GPL, read the file 'COPYING' for more information */ #include <utility> #include "sp-namedview.h" #include "snap.h" #include "snapped-line.h" #include <libnr/nr-point-fns.h> #include <libnr/nr-scale-ops.h> #include <libnr/nr-values.h> #include "display/canvas-grid.h" #include "inkscape.h" #include "desktop.h" #include "sp-guide.h" using std::vector; /** * Construct a SnapManager for a SPNamedView. * * \param v `Owning' SPNamedView. */ 00044 SnapManager::SnapManager(SPNamedView const *v) : guide(v, 0), object(v, 0), _named_view(v), _include_item_center(false), _snap_enabled_globally(true) { } /** * \return List of snappers that we use. */ SnapManager::SnapperList 00058 SnapManager::getSnappers() const { SnapManager::SnapperList s; s.push_back(&guide); s.push_back(&object); SnapManager::SnapperList gs = getGridSnappers(); s.splice(s.begin(), gs); return s; } /** * \return List of gridsnappers that we use. */ SnapManager::SnapperList 00074 SnapManager::getGridSnappers() const { SnapperList s; //FIXME: this code should actually do this: add new grid snappers that are active for this desktop. now it just adds all gridsnappers SPDesktop* desktop = SP_ACTIVE_DESKTOP; if (desktop && desktop->gridsEnabled()) { for ( GSList const *l = _named_view->grids; l != NULL; l = l->next) { Inkscape::CanvasGrid *grid = (Inkscape::CanvasGrid*) l->data; s.push_back(grid->snapper); } } return s; } /** * \return true if one of the snappers will try to snap something. */ 00094 bool SnapManager::SomeSnapperMightSnap() const { if (!_snap_enabled_globally) { return false; } SnapperList const s = getSnappers(); SnapperList::const_iterator i = s.begin(); while (i != s.end() && (*i)->ThisSnapperMightSnap() == false) { i++; } return (i != s.end()); } /* * The snappers have too many parameters to adjust individually. Therefore only * two snapping modes are presented to the user: snapping bounding box corners (to * other bounding boxes, grids or guides), and/or snapping nodes (to other nodes, * paths, grids or guides). To select either of these modes (or both), use the * methods defined below: setSnapModeBBox() and setSnapModeNode(). * * */ void SnapManager::setSnapModeBBox(bool enabled) { //The default values are being set in sp_namedview_set() (in sp-namedview.cpp) guide.setSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX, enabled); for ( GSList const *l = _named_view->grids; l != NULL; l = l->next) { Inkscape::CanvasGrid *grid = (Inkscape::CanvasGrid*) l->data; grid->snapper->setSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX, enabled); } object.setSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX, enabled); //object.setSnapToBBoxNode(enabled); // On second thought, these should be controlled //object.setSnapToBBoxPath(enabled); // separately by the snapping prefs dialog object.setStrictSnapping(true); //don't snap bboxes to nodes/paths and vice versa } bool SnapManager::getSnapModeBBox() const { return guide.getSnapFrom(Inkscape::Snapper::SNAPPOINT_BBOX); } void SnapManager::setSnapModeNode(bool enabled) { guide.setSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE, enabled); for ( GSList const *l = _named_view->grids; l != NULL; l = l->next) { Inkscape::CanvasGrid *grid = (Inkscape::CanvasGrid*) l->data; grid->snapper->setSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE, enabled); } object.setSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE, enabled); //object.setSnapToItemNode(enabled); // On second thought, these should be controlled //object.setSnapToItemPath(enabled); // separately by the snapping prefs dialog object.setStrictSnapping(true); } bool SnapManager::getSnapModeNode() const { return guide.getSnapFrom(Inkscape::Snapper::SNAPPOINT_NODE); } void SnapManager::setSnapModeGuide(bool enabled) { object.setSnapFrom(Inkscape::Snapper::SNAPPOINT_GUIDE, enabled); } bool SnapManager::getSnapModeGuide() const { return object.getSnapFrom(Inkscape::Snapper::SNAPPOINT_GUIDE); } /** * Try to snap a point to any interested snappers. * * \param t Type of point. * \param p Point. * \param it Item to ignore when snapping. * \return Snapped point. */ 00179 Inkscape::SnappedPoint SnapManager::freeSnap(Inkscape::Snapper::PointType t, NR::Point const &p, SPItem const *it) const { std::list<SPItem const *> lit; lit.push_back(it); std::vector<NR::Point> points_to_snap; points_to_snap.push_back(p); return freeSnap(t, p, true, points_to_snap, lit); } /** * Try to snap a point to any of the specified snappers. * * \param t Type of point. * \param p Point. * \param first_point If true then this point is the first one from a whole bunch of points * \param points_to_snap The whole bunch of points, all from the same selection and having the same transformation * \param it List of items to ignore when snapping. * \param snappers List of snappers to try to snap to * \return Snapped point. */ 00205 Inkscape::SnappedPoint SnapManager::freeSnap(Inkscape::Snapper::PointType t, NR::Point const &p, bool const &first_point, std::vector<NR::Point> &points_to_snap, std::list<SPItem const *> const &it) const { if (!SomeSnapperMightSnap()) { return Inkscape::SnappedPoint(p, NR_HUGE, 0, false); } SnappedConstraints sc; SnapperList const snappers = getSnappers(); for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); i++) { (*i)->freeSnap(sc, t, p, first_point, points_to_snap, it); } return findBestSnap(p, sc, false); } /** * Try to snap a point to any interested snappers. A snap will only occur along * a line described by a Inkscape::Snapper::ConstraintLine. * * \param t Type of point. * \param p Point. * \param c Constraint line. * \param it Item to ignore when snapping. * \return Snapped point. */ 00237 Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::Snapper::PointType t, NR::Point const &p, Inkscape::Snapper::ConstraintLine const &c, SPItem const *it) const { std::list<SPItem const *> lit; lit.push_back(it); std::vector<NR::Point> points_to_snap; points_to_snap.push_back(p); return constrainedSnap(t, p, true, points_to_snap, c, lit); } /** * Try to snap a point to any interested snappers. A snap will only occur along * a line described by a Inkscape::Snapper::ConstraintLine. * * \param t Type of point. * \param p Point. * \param first_point If true then this point is the first one from a whole bunch of points * \param points_to_snap The whole bunch of points, all from the same selection and having the same transformation * \param c Constraint line. * \param it List of items to ignore when snapping. * \return Snapped point. */ 00266 Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::Snapper::PointType t, NR::Point const &p, bool const &first_point, std::vector<NR::Point> &points_to_snap, Inkscape::Snapper::ConstraintLine const &c, std::list<SPItem const *> const &it) const { if (!SomeSnapperMightSnap()) { return Inkscape::SnappedPoint(p, NR_HUGE, 0, false); } SnappedConstraints sc; SnapperList const snappers = getSnappers(); for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); i++) { (*i)->constrainedSnap(sc, t, p, first_point, points_to_snap, c, it); } return findBestSnap(p, sc, true); } Inkscape::SnappedPoint SnapManager::guideSnap(NR::Point const &p, NR::Point const &guide_normal) const { // This method is used to snap a guide to nodes, while dragging the guide around if (!(object.GuidesMightSnap() && _snap_enabled_globally)) { return Inkscape::SnappedPoint(p, NR_HUGE, 0, false); } SnappedConstraints sc; object.guideSnap(sc, p, guide_normal); return findBestSnap(p, sc, false); } /** * Main internal snapping method, which is called by the other, friendlier, public * methods. It's a bit hairy as it has lots of parameters, but it saves on a lot * of duplicated code. * * \param type Type of points being snapped. * \param points List of points to snap. * \param ignore List of items to ignore while snapping. * \param constrained true if the snap is constrained. * \param constraint Constraint line to use, if `constrained' is true, otherwise undefined. * \param transformation_type Type of transformation to apply to points before trying to snap them. * \param transformation Description of the transformation; details depend on the type. * \param origin Origin of the transformation, if applicable. * \param dim Dimension of the transformation, if applicable. * \param uniform true if the transformation should be uniform; only applicable for stretching and scaling. */ 00320 std::pair<NR::Point, bool> SnapManager::_snapTransformed( Inkscape::Snapper::PointType type, std::vector<NR::Point> const &points, std::list<SPItem const *> const &ignore, bool constrained, Inkscape::Snapper::ConstraintLine const &constraint, Transformation transformation_type, NR::Point const &transformation, NR::Point const &origin, NR::Dim2 dim, bool uniform) const { /* We have a list of points, which we are proposing to transform in some way. We need to see ** if any of these points, when transformed, snap to anything. If they do, we return the ** appropriate transformation with `true'; otherwise we return the original scale with `false'. */ /* Quick check to see if we have any snappers that are enabled ** Also used to globally disable all snapping */ if (SomeSnapperMightSnap() == false) { return std::make_pair(transformation, false); } std::vector<NR::Point> transformed_points; for (std::vector<NR::Point>::const_iterator i = points.begin(); i != points.end(); i++) { /* Work out the transformed version of this point */ NR::Point transformed; switch (transformation_type) { case TRANSLATION: transformed = *i + transformation; break; case SCALE: transformed = ((*i - origin) * NR::scale(transformation[NR::X], transformation[NR::Y])) + origin; break; case STRETCH: { NR::scale s(1, 1); if (uniform) s[NR::X] = s[NR::Y] = transformation[dim]; else { s[dim] = transformation[dim]; s[1 - dim] = 1; } transformed = ((*i - origin) * s) + origin; break; } case SKEW: transformed = *i; transformed[dim] += transformation[dim] * ((*i)[1 - dim] - origin[1 - dim]); break; default: g_assert_not_reached(); } // add the current transformed point to the box hulling all transformed points transformed_points.push_back(transformed); } /* The current best transformation */ NR::Point best_transformation = transformation; /* The current best metric for the best transformation; lower is better, NR_HUGE ** means that we haven't snapped anything. */ NR::Coord best_metric = NR_HUGE; NR::Coord best_second_metric = NR_HUGE; NR::Point best_scale_metric(NR_HUGE, NR_HUGE); bool best_at_intersection = false; bool best_always_snap = false; std::vector<NR::Point>::const_iterator j = transformed_points.begin(); //std::cout << std::endl; for (std::vector<NR::Point>::const_iterator i = points.begin(); i != points.end(); i++) { /* Snap it */ Inkscape::SnappedPoint snapped; if (constrained) { Inkscape::Snapper::ConstraintLine dedicated_constraint = constraint; if ((transformation_type == SCALE || transformation_type == STRETCH) && uniform) { // When uniformly scaling, each point will have its own unique constraint line, // running from the scaling origin to the original untransformed point. We will // calculate that line here dedicated_constraint = Inkscape::Snapper::ConstraintLine(origin, (*i) - origin); } else if (transformation_type == STRETCH || transformation_type == SKEW) { // when skewing or non-uniform stretching { dedicated_constraint = Inkscape::Snapper::ConstraintLine((*i), component_vectors[dim]); } // else: leave the original constraint, e.g. for constrained translation if (transformation_type == SCALE && !uniform) { g_warning("Non-uniform constrained scaling is not supported!"); } snapped = constrainedSnap(type, *j, i == points.begin(), transformed_points, dedicated_constraint, ignore); } else { snapped = freeSnap(type, *j, i == points.begin(), transformed_points, ignore); } NR::Point result; NR::Coord metric = NR_HUGE; NR::Coord second_metric = NR_HUGE; NR::Point scale_metric(NR_HUGE, NR_HUGE); if (snapped.getDistance() < NR_HUGE) { /* We snapped. Find the transformation that describes where the snapped point has ** ended up, and also the metric for this transformation. */ NR::Point const a = (snapped.getPoint() - origin); // vector to snapped point NR::Point const b = (*i - origin); // vector to original point switch (transformation_type) { case TRANSLATION: result = snapped.getPoint() - *i; /* Consider the case in which a box is almost aligned with a grid in both * horizontal and vertical directions. The distance to the intersection of * the grid lines will always be larger then the distance to a single grid * line. If we prefer snapping to an intersection instead of to a single * grid line, then we cannot use "metric = NR::L2(result)". Therefore the * snapped distance will be used as a metric. Please note that the snapped * distance is defined as the distance to the nearest line of the intersection, * and not to the intersection itself! */ metric = snapped.getDistance(); //used to be: metric = NR::L2(result); second_metric = snapped.getSecondDistance(); break; case SCALE: { result = NR::Point(NR_HUGE, NR_HUGE); // If this point *i is horizontally or vertically aligned with // the origin of the scaling, then it will scale purely in X or Y // We can therefore only calculate the scaling in this direction // and the scaling factor for the other direction should remain // untouched (unless scaling is uniform ofcourse) for (int index = 0; index < 2; index++) { if (fabs(b[index]) > 1e-6) { // if SCALING CAN occur in this direction if (fabs(fabs(a[index]/b[index]) - fabs(transformation[index])) > 1e-12) { // if SNAPPING DID occur in this direction result[index] = a[index] / b[index]; // then calculate it! } // we might leave result[1-index] = NR_HUGE // if scaling didn't occur in the other direction } } // Compare the resulting scaling with the desired scaling scale_metric = result - transformation; // One or both of its components might be NR_HUGE break; } case STRETCH: result = NR::Point(NR_HUGE, NR_HUGE); if (fabs(b[dim]) > 1e-6) { // if STRETCHING will occur for this point result[dim] = a[dim] / b[dim]; result[1-dim] = uniform ? result[dim] : 1; } else { // STRETCHING might occur for this point, but only when the stretching is uniform if (uniform && fabs(b[1-dim]) > 1e-6) { result[1-dim] = a[1-dim] / b[1-dim]; result[dim] = result[1-dim]; } } metric = std::abs(result[dim] - transformation[dim]); break; case SKEW: result[dim] = (snapped.getPoint()[dim] - (*i)[dim]) / ((*i)[1 - dim] - origin[1 - dim]); metric = std::abs(result[dim] - transformation[dim]); break; default: g_assert_not_reached(); } /* Note it if it's the best so far */ if (transformation_type == SCALE) { for (int index = 0; index < 2; index++) { if (fabs(scale_metric[index]) < fabs(best_scale_metric[index])) { best_transformation[index] = result[index]; best_scale_metric[index] = fabs(scale_metric[index]); //std::cout << "SEL "; } //else { std::cout << " ";} } if (uniform) { if (best_scale_metric[0] < best_scale_metric[1]) { best_transformation[1] = best_transformation[0]; best_scale_metric[1] = best_scale_metric[0]; } else { best_transformation[0] = best_transformation[1]; best_scale_metric[0] = best_scale_metric[1]; } } best_metric = std::min(best_scale_metric[0], best_scale_metric[1]); //std::cout << "P_orig = " << (*i) << " | scale_metric = " << scale_metric << " | distance = " << snapped.getDistance() << " | P_snap = " << snapped.getPoint() << std::endl; } else { bool const c1 = metric < best_metric; bool const c2 = metric == best_metric && snapped.getAtIntersection() == true && best_at_intersection == false; bool const c3a = metric == best_metric && snapped.getAtIntersection() == true && best_at_intersection == true; bool const c3b = second_metric < best_second_metric; bool const c4 = snapped.getAlwaysSnap() == true && best_always_snap == false; bool const c4n = snapped.getAlwaysSnap() == false && best_always_snap == true; if ((c1 || c2 || (c3a && c3b) || c4) && !c4n) { best_transformation = result; best_metric = metric; best_second_metric = second_metric; best_at_intersection = snapped.getAtIntersection(); best_always_snap = snapped.getAlwaysSnap(); //std::cout << "SEL "; } //else { std::cout << " ";} //std::cout << "P_orig = " << (*i) << " | metric = " << metric << " | distance = " << snapped.getDistance() << " | second metric = " << second_metric << " | P_snap = " << snapped.getPoint() << std::endl; } } j++; } if (transformation_type == SCALE) { // When scaling, don't ever exit with one of scaling components set to NR_HUGE for (int index = 0; index < 2; index++) { if (best_transformation[index] == NR_HUGE) { if (uniform && best_transformation[1-index] < NR_HUGE) { best_transformation[index] = best_transformation[1-index]; } else { best_transformation[index] = transformation[index]; } } } } // Using " < 1e6" instead of " < NR_HUGE" for catching some rounding errors // These rounding errors might be caused by NRRects, see bug #1584301 return std::make_pair(best_transformation, best_metric < 1e6); } /** * Try to snap a list of points to any interested snappers after they have undergone * a translation. * * \param t Type of points. * \param p Points. * \param it List of items to ignore when snapping. * \param tr Proposed translation. * \return Snapped translation, if a snap occurred, and a flag indicating whether a snap occurred. */ 00562 std::pair<NR::Point, bool> SnapManager::freeSnapTranslation(Inkscape::Snapper::PointType t, std::vector<NR::Point> const &p, std::list<SPItem const *> const &it, NR::Point const &tr) const { return _snapTransformed( t, p, it, false, NR::Point(), TRANSLATION, tr, NR::Point(), NR::X, false ); } /** * Try to snap a list of points to any interested snappers after they have undergone a * translation. A snap will only occur along a line described by a * Inkscape::Snapper::ConstraintLine. * * \param t Type of points. * \param p Points. * \param it List of items to ignore when snapping. * \param c Constraint line. * \param tr Proposed translation. * \return Snapped translation, if a snap occurred, and a flag indicating whether a snap occurred. */ 00586 std::pair<NR::Point, bool> SnapManager::constrainedSnapTranslation(Inkscape::Snapper::PointType t, std::vector<NR::Point> const &p, std::list<SPItem const *> const &it, Inkscape::Snapper::ConstraintLine const &c, NR::Point const &tr) const { return _snapTransformed( t, p, it, true, c, TRANSLATION, tr, NR::Point(), NR::X, false ); } /** * Try to snap a list of points to any interested snappers after they have undergone * a scale. * * \param t Type of points. * \param p Points. * \param it List of items to ignore when snapping. * \param s Proposed scale. * \param o Origin of proposed scale. * \return Snapped scale, if a snap occurred, and a flag indicating whether a snap occurred. */ 00610 std::pair<NR::scale, bool> SnapManager::freeSnapScale(Inkscape::Snapper::PointType t, std::vector<NR::Point> const &p, std::list<SPItem const *> const &it, NR::scale const &s, NR::Point const &o) const { return _snapTransformed( t, p, it, false, NR::Point(), SCALE, NR::Point(s[NR::X], s[NR::Y]), o, NR::X, false ); } /** * Try to snap a list of points to any interested snappers after they have undergone * a scale. A snap will only occur along a line described by a * Inkscape::Snapper::ConstraintLine. * * \param t Type of points. * \param p Points. * \param it List of items to ignore when snapping. * \param s Proposed scale. * \param o Origin of proposed scale. * \return Snapped scale, if a snap occurred, and a flag indicating whether a snap occurred. */ 00635 std::pair<NR::scale, bool> SnapManager::constrainedSnapScale(Inkscape::Snapper::PointType t, std::vector<NR::Point> const &p, std::list<SPItem const *> const &it, NR::scale const &s, NR::Point const &o) const { // When constrained scaling, only uniform scaling is supported. return _snapTransformed( t, p, it, true, NR::Point(), SCALE, NR::Point(s[NR::X], s[NR::Y]), o, NR::X, true ); } /** * Try to snap a list of points to any interested snappers after they have undergone * a stretch. * * \param t Type of points. * \param p Points. * \param it List of items to ignore when snapping. * \param s Proposed stretch. * \param o Origin of proposed stretch. * \param d Dimension in which to apply proposed stretch. * \param u true if the stretch should be uniform (ie to be applied equally in both dimensions) * \return Snapped stretch, if a snap occurred, and a flag indicating whether a snap occurred. */ 00662 std::pair<NR::Coord, bool> SnapManager::constrainedSnapStretch(Inkscape::Snapper::PointType t, std::vector<NR::Point> const &p, std::list<SPItem const *> const &it, NR::Coord const &s, NR::Point const &o, NR::Dim2 d, bool u) const { std::pair<NR::Point, bool> const r = _snapTransformed( t, p, it, true, NR::Point(), STRETCH, NR::Point(s, s), o, d, u ); return std::make_pair(r.first[d], r.second); } /** * Try to snap a list of points to any interested snappers after they have undergone * a skew. * * \param t Type of points. * \param p Points. * \param it List of items to ignore when snapping. * \param s Proposed skew. * \param o Origin of proposed skew. * \param d Dimension in which to apply proposed skew. * \return Snapped skew, if a snap occurred, and a flag indicating whether a snap occurred. */ 00691 std::pair<NR::Coord, bool> SnapManager::freeSnapSkew(Inkscape::Snapper::PointType t, std::vector<NR::Point> const &p, std::list<SPItem const *> const &it, NR::Coord const &s, NR::Point const &o, NR::Dim2 d) const { std::pair<NR::Point, bool> const r = _snapTransformed( t, p, it, false, NR::Point(), SKEW, NR::Point(s, s), o, d, false ); return std::make_pair(r.first[d], r.second); } Inkscape::SnappedPoint SnapManager::findBestSnap(NR::Point const &p, SnappedConstraints &sc, bool constrained) const { // Store all snappoints std::list<Inkscape::SnappedPoint> sp_list; // search for the closest snapped point Inkscape::SnappedPoint closestPoint; if (getClosestSP(sc.points, closestPoint)) { sp_list.push_back(closestPoint); } // search for the closest snapped line segment Inkscape::SnappedLineSegment closestLineSegment; if (getClosestSLS(sc.lines, closestLineSegment)) { sp_list.push_back(Inkscape::SnappedPoint(closestLineSegment)); } if (_intersectionLS) { // search for the closest snapped intersection of line segments Inkscape::SnappedPoint closestLineSegmentIntersection; if (getClosestIntersectionSLS(sc.lines, closestLineSegmentIntersection)) { sp_list.push_back(closestLineSegmentIntersection); } } // search for the closest snapped grid line Inkscape::SnappedLine closestGridLine; if (getClosestSL(sc.grid_lines, closestGridLine)) { sp_list.push_back(Inkscape::SnappedPoint(closestGridLine)); } // search for the closest snapped guide line Inkscape::SnappedLine closestGuideLine; if (getClosestSL(sc.guide_lines, closestGuideLine)) { sp_list.push_back(Inkscape::SnappedPoint(closestGuideLine)); } // When freely snapping to a grid/guide/path, only one degree of freedom is eliminated // Therefore we will try get fully constrained by finding an intersection with another grid/guide/path // When doing a constrained snap however, we're already at an intersection of the constrained line and // the grid/guide/path we're snapping to. This snappoint is therefore fully constrained, so there's // no need to look for additional intersections if (!constrained) { // search for the closest snapped intersection of grid lines Inkscape::SnappedPoint closestGridPoint; if (getClosestIntersectionSL(sc.grid_lines, closestGridPoint)) { sp_list.push_back(closestGridPoint); } // search for the closest snapped intersection of guide lines Inkscape::SnappedPoint closestGuidePoint; if (getClosestIntersectionSL(sc.guide_lines, closestGuidePoint)) { sp_list.push_back(closestGuidePoint); } // search for the closest snapped intersection of grid with guide lines if (_intersectionGG) { Inkscape::SnappedPoint closestGridGuidePoint; if (getClosestIntersectionSL(sc.grid_lines, sc.guide_lines, closestGridGuidePoint)) { sp_list.push_back(closestGridGuidePoint); } } } // now let's see which snapped point gets a thumbs up Inkscape::SnappedPoint bestSnappedPoint = Inkscape::SnappedPoint(p, NR_HUGE, 0, false); for (std::list<Inkscape::SnappedPoint>::const_iterator i = sp_list.begin(); i != sp_list.end(); i++) { // first find out if this snapped point is within snapping range if ((*i).getDistance() <= (*i).getTolerance()) { // if it's the first point bool c1 = (i == sp_list.begin()); // or, if it's closer bool c2 = (*i).getDistance() < bestSnappedPoint.getDistance(); // or, if it's for a snapper with "always snap" turned on, and the previous wasn't bool c3 = (*i).getAlwaysSnap() && !bestSnappedPoint.getAlwaysSnap(); // But in no case fall back from a snapper with "always snap" on to one with "always snap" off bool c3n = !(*i).getAlwaysSnap() && bestSnappedPoint.getAlwaysSnap(); // or, if it's just as close then consider the second distance // (which is only relevant for points at an intersection) bool c4a = ((*i).getDistance() == bestSnappedPoint.getDistance()); bool c4b = (*i).getSecondDistance() < bestSnappedPoint.getSecondDistance(); // then prefer this point over the previous one if ((c1 || c2 || c3 || (c4a && c4b)) && !c3n) { bestSnappedPoint = *i; } } } return bestSnappedPoint; } /* Local Variables: mode:c++ c-file-style:"stroustrup" c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +)) indent-tabs-mode:nil fill-column:99 End: */ // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :