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 const *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                                                     bool const &/*f*/,
  30                                                     Geom::OptRect const &/*bbox_to_snap*/,
  31                                                     std::vector<SPItem const *> const */*it*/,
  32                                                     std::vector<Geom::Point> */*unselected_nodes*/) const
  33 {
  34         if (_snap_enabled == false || _snapmanager->snapprefs.getSnapFrom(t) == false) {
  35         return;
  36     }
  37
  38     /* Get the lines that we will try to snap to */
  39     const LineList lines = _getSnapLines(p);
  40
  41     // std::cout << "snap point " << p << " to: " << std::endl;
  42
  43     for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
  44         Geom::Point const p1 = i->second; // point at guide/grid line
  45         Geom::Point const p2 = p1 + Geom::rot90(i->first); // 2nd point at guide/grid line
  46         // std::cout << "  line through " << i->second << " with normal " << i->first;
  47         g_assert(i->first != Geom::Point(0,0)); // we cannot project on an linesegment of zero length
  48
  49         Geom::Point const p_proj = project_on_linesegment(p, p1, p2);
  50         Geom::Coord const dist = Geom::L2(p_proj - p);
  51         //Store any line that's within snapping range
  52         if (dist < getSnapperTolerance()) {
  53             _addSnappedLine(sc, p_proj, dist, i->first, i->second);
  54             // std::cout << " -> distance = " << dist;
  55         }
  56         // std::cout << std::endl;
  57     }
  58 }
  59
  60 void Inkscape::LineSnapper::constrainedSnap(SnappedConstraints &sc,
  61                                                Inkscape::SnapPreferences::PointType const &t,
  62                                                Geom::Point const &p,
  63                                                bool const &/*f*/,
  64                                                Geom::OptRect const &/*bbox_to_snap*/,
  65                                                ConstraintLine const &c,
  66                                                std::vector<SPItem const *> const */*it*/) const
  67
  68 {
  69     if (_snap_enabled == false || _snapmanager->snapprefs.getSnapFrom(t) == false) {
  70         return;
  71     }
  72
  73     /* Get the lines that we will try to snap to */
  74     const LineList lines = _getSnapLines(p);
  75
  76     for (LineList::const_iterator i = lines.begin(); i != lines.end(); i++) {
  77         if (Geom::L2(c.getDirection()) > 0) { // Can't do a constrained snap without a constraint
  78             /* Normal to the line we're trying to snap along */
  79             Geom::Point const n(Geom::rot90(Geom::unit_vector(c.getDirection())));
  80
  81             Geom::Point const point_on_line = c.hasPoint() ? c.getPoint() : p;
  82
  83             /* Constant term of the line we're trying to snap along */
  84             Geom::Coord const q0 = dot(n, point_on_line);
  85             /* Constant term of the grid or guide line */
  86             Geom::Coord const q1 = dot(i->first, i->second);
  87
  88             /* Try to intersect this line with the target line */
  89             Geom::Point t_2geom(NR_HUGE, NR_HUGE);
  90             Geom::IntersectorKind const k = Geom::line_intersection(n, q0, i->first, q1, t_2geom);
  91             Geom::Point t(t_2geom);
  92
  93             if (k == Geom::intersects) {
  94                 const Geom::Coord dist = L2(t - p);
  95                 if (dist < getSnapperTolerance()) {
  96                                 // When doing a constrained snap, we're already at an intersection.
  97                     // This snappoint is therefore fully constrained, so there's no need
  98                     // to look for additional intersections; just return the snapped point
  99                     // and forget about the line
 100                     sc.points.push_back(SnappedPoint(t, Inkscape::SNAPTARGET_UNDEFINED, dist, getSnapperTolerance(), getSnapperAlwaysSnap(), true));
 101                     // The type of the snap target is yet undefined, as we cannot tell whether
 102                     // we're snapping to grid or the guide lines; must be set by on a higher level
 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 :