lily/beam-concave.cc

   1 /*
   2   Determine whether a beam is concave.
   3 */
   4
   5 #include "pointer-group-interface.hh"
   6 #include "std-vector.hh"
   7 #include "stem.hh"
   8 #include "beam.hh"
   9 #include "staff-symbol-referencer.hh"
  10 #include "directional-element-interface.hh"
  11
  12 bool
  13 is_concave_single_notes (vector<int> const &positions, Direction beam_dir)
  14 {
  15   Interval covering;
  16   covering.add_point (positions[0]);
  17   covering.add_point (positions.back ());
  18
  19   bool above = false;
  20   bool below = false;
  21   bool concave = false;
  22
  23   /*
  24     notes above and below the interval covered by 1st and last note.
  25   */
  26   for (vsize i = 1; i < positions.size () - 1; i++)
  27     {
  28       above = above || (positions[i] > covering[UP]);
  29       below = below || (positions[i] < covering[DOWN]);
  30     }
  31
  32   concave = concave || (above && below);
  33   /*
  34     A note as close or closer to the beam than begin and end, but the
  35     note is reached in the opposite direction as the last-first dy
  36   */
  37   int dy = positions.back () - positions[0];
  38   int closest = max (beam_dir * positions.back (), beam_dir * positions[0]);
  39   for (vsize i = 2; !concave && i < positions.size () - 1; i++)
  40     {
  41       int inner_dy = positions[i] - positions[i - 1];
  42       if (sign (inner_dy) != sign (dy)
  43           && (beam_dir * positions[i] >= closest
  44               || beam_dir * positions[i - 1] >= closest))
  45         concave = true;
  46     }
  47
  48   bool all_closer = true;
  49   for (vsize i = 1; all_closer && i < positions.size () - 1; i++)
  50     {
  51       all_closer = all_closer
  52         && (beam_dir * positions[i] > closest);
  53     }
  54
  55   concave = concave || all_closer;
  56   return concave;
  57 }
  58
  59 Real
  60 calc_positions_concaveness (vector<int> const &positions, Direction beam_dir)
  61 {
  62   Real dy = positions.back () - positions[0];
  63   Real slope = dy / Real (positions.size () - 1);
  64   Real concaveness = 0.0;
  65   for (vsize i = 1; i < positions.size () - 1; i++)
  66     {
  67       Real line_y = slope * i + positions[0];
  68
  69       concaveness += max (beam_dir * (positions[i] - line_y), 0.0);
  70     }
  71
  72   concaveness /= positions.size ();
  73
  74   /*
  75     Normalize. For dy = 0, the slope ends up as 0 anyway, so the
  76     scaling of concaveness doesn't matter much.
  77   */
  78   if (dy)
  79     concaveness /= fabs (dy);
  80   return concaveness;
  81 }
  82
  83
  84 MAKE_SCHEME_CALLBACK (Beam, calc_concaveness, 1);
  85 SCM
  86 Beam::calc_concaveness (SCM smob)
  87 {
  88   Grob *me = unsmob_grob (smob);
  89
  90   vector<Grob*> stems
  91     = extract_grob_array (me, "stems");
  92
  93   if (is_knee (me))
  94     return scm_from_double (0.0);
  95
  96   Direction beam_dir = CENTER;
  97   for (vsize i = stems.size (); i--;)
  98     {
  99       if (Stem::is_invisible (stems[i]))
 100         stems.erase (stems.begin () + i);
 101       else
 102         {
 103           if (Direction dir = get_grob_direction (stems[i]))
 104             beam_dir = dir;
 105         }
 106     }
 107
 108   if (stems.size () <= 2)
 109     return SCM_UNSPECIFIED;
 110
 111   vector<int> close_positions;
 112   vector<int> far_positions;
 113   for (vsize i = 0; i < stems.size (); i++)
 114     {
 115       /*
 116         For chords, we take the note head that is closest to the beam.
 117
 118         Hmmm.. wait, for the beams in the last measure of morgenlied,
 119         this doesn't look so good. Let's try the heads farthest from
 120         the beam.
 121
 122       */
 123       Interval posns = Stem::head_positions (stems[i]);
 124
 125       close_positions.push_back ((int) rint (posns[beam_dir]));
 126       far_positions.push_back ((int) rint (posns[-beam_dir]));
 127     }
 128
 129   Real concaveness = 0.0;
 130
 131   if (is_concave_single_notes (far_positions, beam_dir))
 132     {
 133       concaveness = 10000;
 134     }
 135   else
 136     {
 137       concaveness = (calc_positions_concaveness (far_positions, beam_dir)
 138                      + calc_positions_concaveness (close_positions, beam_dir)) / 2;
 139     }
 140
 141   return scm_from_double (concaveness);
 142 }
 143
 144
 145