src/line-snapper.cpp

   1 /**
   2  * \file line-snapper.cpp
   3  * \brief LineSnapper class.
   4  *
   5  * Authors:
   6  *   Diederik van Lierop <mail@diedenrezi.nl>
   7  *   And others...
   8  *
   9  * Copyright (C) 1999-2008 Authors
  10  *
  11  * Released under GNU GPL, read the file 'COPYING' for more information
  12  */
  13
  14 #include "libnr/nr-values.h"
  15 #include "libnr/nr-point-fns.h"
  16 #include <2geom/geom.h>
  17 #include "line-snapper.h"
  18 #include "snapped-line.h"
  19 #include <gtk/gtk.h>
  20 #include "snap.h"
  21
  22 Inkscape::LineSnapper::LineSnapper(SnapManager *sm, Geom::Coord const d) : Snapper(sm, d)
  23 {
  24 }
  25
  26 void Inkscape::LineSnapper::freeSnap(SnappedConstraints &sc,
  27                                                     Inkscape::SnapPreferences::PointType const &t,
  28                                                     Geom::Point const &p,
  29                                                     SnapSourceType const &source_type,
  30                                                     bool const &/*f*/,
  31                                                     Geom::OptRect const &/*bbox_to_snap*/,
  32                                                     std::vector<SPItem const *> const */*it*/,
  33                                                     std::vector<std::pair<Geom::Point, int> > */*unselected_nodes*/) const
  34 {
  35         if (!(_snap_enabled && _snapmanager->snapprefs.getSnapFrom(t)) ) {
  36         return;
  37     }
  38
  39     /* Get the lines that we will try to snap to */
  40     const LineList lines = _getSnapLines(p);
  41
  42     // std::cout << "snap point " << p << " to: " << std::endl;
  43
  44     for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
  45         Geom::Point const p1 = i->second; // point at guide/grid line
  46         Geom::Point const p2 = p1 + Geom::rot90(i->first); // 2nd point at guide/grid line
  47         // std::cout << "  line through " << i->second << " with normal " << i->first;
  48         g_assert(i->first != Geom::Point(0,0)); // we cannot project on an linesegment of zero length
  49
  50         Geom::Point const p_proj = Geom::projection(p, Geom::Line(p1, p2));
  51         Geom::Coord const dist = Geom::L2(p_proj - p);
  52         //Store any line that's within snapping range
  53         if (dist < getSnapperTolerance()) {
  54             _addSnappedLine(sc, p_proj, dist, source_type, i->first, i->second);
  55             // std::cout << " -> distance = " << dist;
  56         }
  57         // std::cout << std::endl;
  58     }
  59 }
  60
  61 void Inkscape::LineSnapper::constrainedSnap(SnappedConstraints &sc,
  62                                                Inkscape::SnapPreferences::PointType const &t,
  63                                                Geom::Point const &p,
  64                                                SnapSourceType const &source_type,
  65                                                bool const &/*f*/,
  66                                                Geom::OptRect const &/*bbox_to_snap*/,
  67                                                ConstraintLine const &c,
  68                                                std::vector<SPItem const *> const */*it*/) const
  69
  70 {
  71     if (_snap_enabled == false || _snapmanager->snapprefs.getSnapFrom(t) == false) {
  72         return;
  73     }
  74
  75     /* Get the lines that we will try to snap to */
  76     const LineList lines = _getSnapLines(p);
  77
  78     for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
  79         if (Geom::L2(c.getDirection()) > 0) { // Can't do a constrained snap without a constraint
  80             /* Normal to the line we're trying to snap along */
  81             Geom::Point const n(Geom::rot90(Geom::unit_vector(c.getDirection())));
  82
  83             Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : p;
  84
  85             /* Constant term of the line we're trying to snap along */
  86             Geom::Coord const q0 = dot(n, point_on_line);
  87             /* Constant term of the grid or guide line */
  88             Geom::Coord const q1 = dot(i->first, i->second);
  89
  90             /* Try to intersect this line with the target line */
  91             Geom::Point t_2geom(NR_HUGE, NR_HUGE);
  92             Geom::IntersectorKind const k = Geom::line_intersection(n, q0, i->first, q1, t_2geom);
  93             Geom::Point t(t_2geom);
  94
  95             if (k == Geom::intersects) {
  96                 const Geom::Coord dist = L2(t - p);
  97                 if (dist < getSnapperTolerance()) {
  98                                 // When doing a constrained snap, we're already at an intersection.
  99                     // This snappoint is therefore fully constrained, so there's no need
 100                     // to look for additional intersections; just return the snapped point
 101                     // and forget about the line
 102                     _addSnappedPoint(sc, t, dist, source_type);
 103                 }
 104             }
 105         }
 106     }
 107 }
 108
 109 /*
 110   Local Variables:
 111   mode:c++
 112   c-file-style:"stroustrup"
 113   c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
 114   indent-tabs-mode:nil
 115   fill-column:99
 116   End:
 117 */
 118 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :