src/snap.cpp

   1 #define __SP_DESKTOP_SNAP_C__
   2
   3 /**
   4  * \file snap.cpp
   5  *
   6  * \brief Various snapping methods
   7  *
   8  * Authors:
   9  *   Lauris Kaplinski <lauris@kaplinski.com>
  10  *   Frank Felfe <innerspace@iname.com>
  11  *   Carl Hetherington <inkscape@carlh.net>
  12  *
  13  * Copyright (C) 1999-2002 Authors
  14  *
  15  * Released under GNU GPL, read the file 'COPYING' for more information
  16  */
  17
  18 #include "sp-namedview.h"
  19 #include "snap.h"
  20 #include <libnr/nr-point-fns.h>
  21 #include <libnr/nr-scale-ops.h>
  22 #include <libnr/nr-values.h>
  23
  24 SnapManager::SnapManager(SPNamedView const *v) : grid(v, 0), guide(v, 0), object(v, 0)
  25 {
  26
  27 }
  28
  29 SnapManager::SnapperList SnapManager::getSnappers() const
  30 {
  31     SnapManager::SnapperList s;
  32     s.push_back(&grid);
  33     s.push_back(&guide);
  34     s.push_back(&object);
  35     return s;
  36 }
  37
  38 /**
  39  * \return true if one of the snappers will try to snap something.
  40  */
  41 bool SnapManager::willSnapSomething() const
  42 {
  43     SnapperList const s = getSnappers();
  44     SnapperList::const_iterator i = s.begin();
  45     while (i != s.end() && (*i)->willSnapSomething() == false) {
  46         i++;
  47     }
  48
  49     return (i != s.end());
  50 }
  51
  52 Inkscape::SnappedPoint SnapManager::freeSnap(Inkscape::Snapper::PointType t,
  53                                              NR::Point const &p,
  54                                              SPItem const *it) const
  55
  56 {
  57     std::list<SPItem const *> lit;
  58     lit.push_back(it);
  59     return freeSnap(t, p, lit);
  60 }
  61
  62
  63 Inkscape::SnappedPoint SnapManager::freeSnap(Inkscape::Snapper::PointType t,
  64                                              NR::Point const &p,
  65                                              std::list<SPItem const *> const &it) const
  66 {
  67     Inkscape::SnappedPoint r(p, NR_HUGE);
  68
  69     SnapperList const snappers = getSnappers();
  70     for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); i++) {
  71         Inkscape::SnappedPoint const s = (*i)->freeSnap(t, p, it);
  72         if (s.getDistance() < r.getDistance()) {
  73             r = s;
  74         }
  75     }
  76
  77     return r;
  78 }
  79
  80
  81 Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::Snapper::PointType t,
  82                                                     NR::Point const &p,
  83                                                     Inkscape::Snapper::ConstraintLine const &c,
  84                                                     SPItem const *it) const
  85 {
  86     std::list<SPItem const *> lit;
  87     lit.push_back(it);
  88     return constrainedSnap(t, p, c, lit);
  89 }
  90
  91
  92 Inkscape::SnappedPoint SnapManager::constrainedSnap(Inkscape::Snapper::PointType t,
  93                                                     NR::Point const &p,
  94                                                     Inkscape::Snapper::ConstraintLine const &c,
  95                                                     std::list<SPItem const *> const &it) const
  96 {
  97     Inkscape::SnappedPoint r(p, NR_HUGE);
  98
  99     SnapperList const snappers = getSnappers();
 100     for (SnapperList::const_iterator i = snappers.begin(); i != snappers.end(); i++) {
 101         Inkscape::SnappedPoint const s = (*i)->constrainedSnap(t, p, c, it);
 102         if (s.getDistance() < r.getDistance()) {
 103             r = s;
 104         }
 105     }
 106
 107     return r;
 108 }
 109
 110
 111 std::pair<NR::Point, bool> SnapManager::_snapTransformed(
 112     Inkscape::Snapper::PointType type,
 113     std::vector<NR::Point> const &points,
 114     std::list<SPItem const *> const &ignore,
 115     bool constrained,
 116     Inkscape::Snapper::ConstraintLine const &constraint,
 117     Transformation transformation_type,
 118     NR::Point const &transformation,
 119     NR::Point const &origin,
 120     NR::Dim2 dim,
 121     bool uniform) const
 122 {
 123     /* We have a list of points, which we are proposing to transform in some way.  We need to see
 124     ** if any of these points, when transformed, snap to anything.  If they do, we return the
 125     ** appropriate transformation with `true'; otherwise we return the original scale with `false'.
 126     */
 127
 128     /* Quick check to see if we have any snappers that are enabled */
 129     if (willSnapSomething() == false) {
 130         return std::make_pair(transformation, false);
 131     }
 132
 133     /* The current best transformation */
 134     NR::Point best_transformation = transformation;
 135
 136     /* The current best metric for the best transformation; lower is better, NR_HUGE
 137     ** means that we haven't snapped anything.
 138     */
 139     double best_metric = NR_HUGE;
 140
 141     for (std::vector<NR::Point>::const_iterator i = points.begin(); i != points.end(); i++) {
 142
 143         /* Work out the transformed version of this point */
 144         NR::Point transformed;
 145         switch (transformation_type) {
 146             case TRANSLATION:
 147                 transformed = *i + transformation;
 148                 break;
 149             case SCALE:
 150                 transformed = ((*i - origin) * NR::scale(transformation[NR::X], transformation[NR::Y])) + origin;
 151                 break;
 152             case STRETCH:
 153             {
 154                 NR::scale s(1, 1);
 155                 if (uniform)
 156                     s[NR::X] = s[NR::Y] = transformation[dim];
 157                 else {
 158                     s[dim] = transformation[dim];
 159                     s[1 - dim] = 1;
 160                 }
 161                 transformed = ((*i - origin) * s) + origin;
 162                 break;
 163             }
 164             case SKEW:
 165                 transformed = *i;
 166                 transformed[dim] += transformation[dim] * ((*i)[1 - dim] - origin[1 - dim]);
 167                 break;
 168             default:
 169                 g_assert_not_reached();
 170         }
 171
 172         /* Snap it */
 173         Inkscape::SnappedPoint const snapped = constrained ?
 174             constrainedSnap(type, transformed, constraint, ignore) : freeSnap(type, transformed, ignore);
 175
 176         if (snapped.getDistance() < NR_HUGE) {
 177             /* We snapped.  Find the transformation that describes where the snapped point has
 178             ** ended up, and also the metric for this transformation.
 179             */
 180             NR::Point result;
 181             NR::Coord metric;
 182             switch (transformation_type) {
 183                 case TRANSLATION:
 184                     result = snapped.getPoint() - *i;
 185                     metric = NR::L2(result);
 186                     break;
 187                 case SCALE:
 188                 {
 189                     NR::Point const a = (snapped.getPoint() - origin);
 190                     NR::Point const b = (*i - origin);
 191                     result = NR::Point(a[NR::X] / b[NR::X], a[NR::Y] / b[NR::Y]);
 192                     metric = std::abs(NR::L2(result) - NR::L2(transformation));
 193                     break;
 194                 }
 195                 case STRETCH:
 196                 {
 197                     for (int j = 0; j < 2; j++) {
 198                         if (uniform || j == dim) {
 199                             result[j] = (snapped.getPoint()[dim] - origin[dim]) / ((*i)[dim] - origin[dim]);
 200                         } else {
 201                             result[j] = 1;
 202                         }
 203                     }
 204                     metric = std::abs(result[dim] - transformation[dim]);
 205                     break;
 206                 }
 207                 case SKEW:
 208                     result[dim] = (snapped.getPoint()[dim] - (*i)[dim]) / ((*i)[1 - dim] - origin[1 - dim]);
 209                     metric = std::abs(result[dim] - transformation[dim]);
 210                     break;
 211                 default:
 212                     g_assert_not_reached();
 213             }
 214
 215             /* Note it if it's the best so far */
 216             if (metric < best_metric && metric != 0) {
 217                 best_transformation = result;
 218                 best_metric = metric;
 219             }
 220         }
 221     }
 222
 223     return std::make_pair(best_transformation, best_metric < NR_HUGE);
 224 }
 225
 226
 227 std::pair<NR::Point, bool> SnapManager::freeSnapTranslation(Inkscape::Snapper::PointType t,
 228                                                             std::vector<NR::Point> const &p,
 229                                                             std::list<SPItem const *> const &it,
 230                                                             NR::Point const &tr) const
 231 {
 232     return _snapTransformed(
 233         t, p, it, false, NR::Point(), TRANSLATION, tr, NR::Point(), NR::X, false
 234         );
 235 }
 236
 237
 238
 239 std::pair<NR::Point, bool> SnapManager::constrainedSnapTranslation(Inkscape::Snapper::PointType t,
 240                                                                    std::vector<NR::Point> const &p,
 241                                                                    std::list<SPItem const *> const &it,
 242                                                                    Inkscape::Snapper::ConstraintLine const &c,
 243                                                                    NR::Point const &tr) const
 244 {
 245     return _snapTransformed(
 246         t, p, it, true, c, TRANSLATION, tr, NR::Point(), NR::X, false
 247         );
 248 }
 249
 250 std::pair<NR::scale, bool> SnapManager::freeSnapScale(Inkscape::Snapper::PointType t,
 251                                                       std::vector<NR::Point> const &p,
 252                                                       std::list<SPItem const *> const &it,
 253                                                       NR::scale const &s,
 254                                                       NR::Point const &o) const
 255 {
 256     return _snapTransformed(
 257         t, p, it, false, NR::Point(), SCALE, NR::Point(s[NR::X], s[NR::Y]), o, NR::X, false
 258         );
 259 }
 260
 261
 262 std::pair<NR::scale, bool> SnapManager::constrainedSnapScale(Inkscape::Snapper::PointType t,
 263                                                              std::vector<NR::Point> const &p,
 264                                                              std::list<SPItem const *> const &it,
 265                                                              Inkscape::Snapper::ConstraintLine const &c,
 266                                                              NR::scale const &s,
 267                                                              NR::Point const &o) const
 268 {
 269     return _snapTransformed(
 270         t, p, it, true, c, SCALE, NR::Point(s[NR::X], s[NR::Y]), o, NR::X, false
 271         );
 272 }
 273
 274
 275 std::pair<NR::Coord, bool> SnapManager::freeSnapStretch(Inkscape::Snapper::PointType t,
 276                                                         std::vector<NR::Point> const &p,
 277                                                         std::list<SPItem const *> const &it,
 278                                                         NR::Coord const &s,
 279                                                         NR::Point const &o,
 280                                                         NR::Dim2 d,
 281                                                         bool u) const
 282 {
 283    std::pair<NR::Point, bool> const r = _snapTransformed(
 284         t, p, it, false, NR::Point(), STRETCH, NR::Point(s, s), o, d, u
 285         );
 286
 287    return std::make_pair(r.first[d], r.second);
 288 }
 289
 290
 291 std::pair<NR::Coord, bool> SnapManager::freeSnapSkew(Inkscape::Snapper::PointType t,
 292                                                      std::vector<NR::Point> const &p,
 293                                                      std::list<SPItem const *> const &it,
 294                                                      NR::Coord const &s,
 295                                                      NR::Point const &o,
 296                                                      NR::Dim2 d) const
 297 {
 298    std::pair<NR::Point, bool> const r = _snapTransformed(
 299         t, p, it, false, NR::Point(), SKEW, NR::Point(s, s), o, d, false
 300         );
 301
 302    return std::make_pair(r.first[d], r.second);
 303 }
 304
 305 /*
 306   Local Variables:
 307   mode:c++
 308   c-file-style:"stroustrup"
 309   c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
 310   indent-tabs-mode:nil
 311   fill-column:99
 312   End:
 313 */
 314 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :