X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=lily%2Fbeam.cc;h=027a08d70f0499b37ee6b50296c2fe31d8260470;hb=41e82f1eed38b69f60f74221c52ce14692318d6d;hp=ebda7c1ccd0eafb4c00d1291289aeb7ec88c38c7;hpb=c24b8835be7d548804a94f6caceadcf914bb8198;p=lilypond.git

diff --git a/lily/beam.cc b/lily/beam.cc
index ebda7c1ccd..027a08d70f 100644
--- a/lily/beam.cc
+++ b/lily/beam.cc
@@ -3,590 +3,836 @@
 
   source file of the GNU LilyPond music typesetter
 
-  (c) 1997 Han-Wen Nienhuys <hanwen@stack.nl>
+  (c)  1997--2000 Han-Wen Nienhuys <hanwen@cs.uu.nl>
+    Jan Nieuwenhuizen <janneke@gnu.org>
 
-  TODO
+*/
+
+/*
+  [TODO]
+    * less hairy code
+    * move paper vars to scm
 
-  Less hairy code.  knee: ([\stem 1; c8 \stem -1; c8]
 
+    remove *-hs variables.
+    
 */
 
-#include <math.h>
 
-#include "p-col.hh"
-#include "varray.hh"
-#include "proto.hh"
-#include "dimen.hh"
+#include <math.h>		// tanh.
+#include "directional-element-interface.hh"
+#include "beaming.hh"
+#include "dimensions.hh"
 #include "beam.hh"
-#include "abbreviation-beam.hh"
 #include "misc.hh"
 #include "debug.hh"
-#include "atom.hh"
-#include "molecule.hh"
-#include "leastsquares.hh"
+#include "least-squares.hh"
 #include "stem.hh"
 #include "paper-def.hh"
 #include "lookup.hh"
-#include "grouping.hh"
-#include "stem-info.hh"
-#include "main.hh"  // experimental features
-
-
-IMPLEMENT_IS_TYPE_B1 (Beam, Spanner);
-
-// ugh, hardcoded
-const int MINIMUM_STEMLEN[] = {
-  0, // just in case
-  5, 
-  4,
-  3,
-  2,
-  2,
-};
+#include "group-interface.hh"
+#include "staff-symbol-referencer.hh"
+#include "cross-staff.hh"
 
 Beam::Beam ()
 {
-  slope_f_ = 0;
-  left_y_ = 0.0;
-  damping_i_ = 1;
-  quantisation_ = NORMAL;
-  multiple_i_ = 0;
+  Group_interface g (this, "stems");
+  g.set_interface ();
+
+  set_elt_property ("height", gh_int2scm (0)); // ugh.
+  set_elt_property ("y-position" ,gh_int2scm (0));
 }
 
 void
-Beam::add (Stem*s)
+Beam::add_stem (Stem*s)
 {
-  stems_.push (s);
+  Group_interface gi (this, "stems");
+  gi.add_element (s);
+  
   s->add_dependency (this);
-  s->beam_l_ = this;
 
-  if (!spanned_drul_[LEFT])
-    set_bounds (LEFT,s);
+  assert (!s->beam_l ());
+  s->set_elt_property ("beam", self_scm_);
+
+  if (!get_bound (LEFT))
+    set_bound (LEFT,s);
   else
-    set_bounds (RIGHT,s);
+    set_bound (RIGHT,s);
 }
 
-Molecule*
-Beam::brew_molecule_p () const
+int
+Beam::get_multiplicity () const
 {
-  Molecule *mol_p = new Molecule;
-  Real inter_f = paper ()->internote_f ();
-  Real x0 = stems_[0]->hpos_f ();
-  for (int j=0; j <stems_.size (); j++)
+  int m = 0;
+  for (SCM s = get_elt_property ("stems"); gh_pair_p (s); s = gh_cdr (s))
     {
-      Stem *i = stems_[j];
-      Stem * prev = (j > 0)? stems_[j-1] : 0;
-      Stem * next = (j < stems_.size ()-1) ? stems_[j+1] :0;
+      Score_element * sc = unsmob_element (gh_car (s));
 
-      Molecule sb = stem_beams (i, next, prev);
-      Real  x = i->hpos_f ()-x0;
-      sb.translate (Offset (x, (x * slope_f_  + left_y_)* inter_f));
-      mol_p->add (sb);
+      if (Stem * st = dynamic_cast<Stem*> (sc))
+	m = m >? st->beam_count (LEFT) >? st->beam_count (RIGHT);
     }
-  mol_p->translate_axis (x0 - spanned_drul_[LEFT]->absolute_coordinate (X_AXIS), X_AXIS);
-  return mol_p;
-}
-
-Offset
-Beam::center () const
-{
-  Real w= (paper ()->note_width () + width ().length ())/2.0;
-  return Offset (w, (left_y_ + w* slope_f_)*paper ()->internote_f ());
+  return m;
 }
 
+/*
+  After pre-processing all directions should be set.
+  Several post-processing routines (stem, slur, script) need stem/beam
+  direction.
+  Currenly, this means that beam has set all stem's directions.
+  [Alternatively, stems could set its own directions, according to
+   their beam, during 'final-pre-processing'.]
+ */
 void
-Beam::do_pre_processing ()
+Beam::before_line_breaking ()
 {
-  if (!dir_)
-    set_default_dir ();
+  // Why?
+  if (visible_stem_count () < 2)
+    {
+      warning (_ ("beam has less than two stems"));
+      //      set_elt_property ("transparent", SCM_BOOL_T);
+    }
+
+  if (!directional_element (this).get ())
+    directional_element (this).set (get_default_dir ());
+
+  auto_knees ();
+  set_stem_directions ();
+  set_stem_shorten (); 
 }
 
-void
-Beam::do_print () const
+/*
+ FIXME
+ */
+Direction
+Beam::get_default_dir () const
 {
-#ifndef NPRINT
-  DOUT << "slope_f_ " <<slope_f_ << "left ypos " << left_y_;
-  Spanner::do_print ();
-#endif
+  Drul_array<int> total;
+  total[UP]  = total[DOWN] = 0;
+  Drul_array<int> count; 
+  count[UP]  = count[DOWN] = 0;
+  Direction d = DOWN;
+
+  for (int i=0; i <stem_count (); i++)
+    do { // HUH -- waar slaat dit op?
+      Stem *s = stem (i);
+      Direction sd = directional_element (s).get ();
+      int current = sd	? (1 + d * sd)/2
+	: s->get_center_distance ((Direction)-d);
+
+      if (current)
+	{
+	  total[d] += current;
+	  count[d] ++;
+	}
+
+    } while (flip(&d) != DOWN);
+  
+
+  SCM s = scm_eval (gh_list (ly_symbol2scm ("beam-dir-algorithm"),
+			     ly_quote_scm (gh_cons (gh_int2scm (count[UP]),
+						    gh_int2scm (count[DOWN]))),
+			     ly_quote_scm (gh_cons (gh_int2scm (total[UP]),
+						    gh_int2scm (total[DOWN]))),
+			     SCM_UNDEFINED));
+  if (gh_number_p (s) && gh_scm2int (s))
+    return to_dir (s);
+  
+  /*
+    If dir is not determined: get from paper
+  */
+  return (Direction)(int)
+    paper_l ()->get_var ("stem_default_neutral_direction");
 }
 
+
+/*
+  Set all stems with non-forced direction to beam direction.
+  Urg: non-forced should become `without/with unforced' direction,
+       once stem gets cleaned-up.
+ */
 void
-Beam::do_post_processing ()
+Beam::set_stem_directions ()
 {
-  if (stems_.size () < 2)
+  Direction d = directional_element (this).get ();
+  for (int i=0; i <stem_count (); i++)
     {
-      warning (_ ("Beam with less than 2 stems"));
-      transparent_b_ = true;
-      return ;
+      Stem *s = stem (i);
+      SCM force = s->remove_elt_property ("dir-forced");
+      if (!gh_boolean_p (force) || !gh_scm2bool (force))
+	directional_element (s).set (d);
     }
-  solve_slope ();
-  set_stemlens ();
-}
+} 
 
 void
-Beam::do_substitute_dependent (Score_elem*o,Score_elem*n)
+Beam::auto_knees ()
 {
-  if (o->is_type_b (Stem::static_name ()))
-      stems_.substitute ((Stem*)o->item (),  n? (Stem*) n->item ():0);
+  if (!auto_knee ("auto-interstaff-knee-gap", true))
+    auto_knee ("auto-knee-gap", false);
 }
 
-Interval
-Beam::do_width () const
+/*
+  Simplistic auto-knees; only consider vertical gap between two
+  adjacent chords.
+
+  `Forced' stem directions are ignored.  If you don't want auto-knees,
+  don't set, or unset autoKneeGap/autoInterstaffKneeGap.
+ */
+bool
+Beam::auto_knee (String gap_str, bool interstaff_b)
 {
-  return Interval (stems_[0]->hpos_f (),
-		   stems_.top ()->hpos_f ());
+  bool knee_b = false;
+  int knee_y = 0;
+  SCM gap = get_elt_property (gap_str);
+  Direction d = directional_element (this).get ();
+  
+  if (gh_number_p (gap))
+    {
+      int auto_gap_i = gh_scm2int (gap);
+      for (int i=1; i < stem_count (); i++)
+        {
+	  bool is_b = (bool)(calc_interstaff_dist (stem (i), this) 
+	    - calc_interstaff_dist (stem (i-1), this));
+	  int l_y = (int)(stem (i-1)->head_positions()[d])
+	    + (int)calc_interstaff_dist (stem (i-1), this);
+	  int r_y = (int)(stem (i)->head_positions()[d])
+	    + (int)calc_interstaff_dist (stem (i), this);
+	  int gap_i = r_y - l_y;
+
+	  if ((abs (gap_i) >= auto_gap_i) && (!interstaff_b || is_b))
+	    {
+	      knee_y = (r_y + l_y) / 2;
+	      knee_b = true;
+	      break;
+	    }
+	}
+    }
+  if (knee_b)
+    {
+      for (int i=0; i < stem_count (); i++)
+        {
+	  int y = (int)(stem (i)->head_positions()[d])
+	    + (int)calc_interstaff_dist (stem (i), this);
+	  directional_element (stem (i)).set (y < knee_y ? UP : DOWN);
+	  stem (i)->set_elt_property ("dir-forced", SCM_BOOL_T);
+	}
+    }
+  return knee_b;
 }
 
+/*
+ Set stem's shorten property if unset.
+ TODO:
+    take some y-position (chord/beam/nearest?) into account
+    scmify forced-fraction
+ */
 void
-Beam::set_default_dir ()
+Beam::set_stem_shorten ()
 {
-  Drul_array<int> total;
-  total[UP]  = total[DOWN] = 0;
-  Drul_array<int> count; 
-  count[UP]  = count[DOWN] = 0;
-  Direction d = DOWN;
-  
-  for (int i=0; i <stems_.size (); i++)
-    do {
-      Stem *s = stems_[i];
-      int current = s->dir_ 
-	? (1 + d * s->dir_)/2
-	: s->get_center_distance (Direction (-d));
+  if (!visible_stem_count ())
+    return;
 
-      if (current)
-	{
-	  total[d] += current;
-	  count[d] ++;
-	}
+  Real forced_fraction = forced_stem_count () / visible_stem_count ();
+  if (forced_fraction < 0.5)
+    return;
 
-    } while ((d *= -1) != DOWN);
-  
-   do {
-    if (!total[d])
-      count[d] = 1;
-  } while ((d *= -1) != DOWN);
+  int multiplicity = get_multiplicity ();
+
+  // grace stems?
+  SCM shorten = scm_eval (ly_symbol2scm ("beamed-stem-shorten"));
+
+  if (shorten == SCM_EOL)
+    return;
+
+  int sz = scm_ilength (shorten);
   
-  /* 
+  Staff_symbol_referencer_interface st (this);
+  Real staff_space = st.staff_space ();
+  SCM shorten_elt = scm_list_ref (shorten, gh_int2scm (multiplicity <? (sz - 1)));
+  Real shorten_f = gh_scm2double (shorten_elt) * staff_space;
 
-     [Ross] states that the majority of the notes dictates the
-     direction (and not the mean of "center distance")
-  */
-  dir_ = (total[UP] > total[DOWN]) ? UP : DOWN;
+  /* cute, but who invented this -- how to customise ? */
+  if (forced_fraction < 1)
+    shorten_f /= 2;
 
-  for (int i=0; i <stems_.size (); i++)
+  for (int i=0; i < stem_count (); i++)
     {
-      Stem *sl = stems_[i];
-      sl->dir_ = dir_;
+      Stem* s = stem (i);
+      if (s->invisible_b ())
+        continue;
+      if (gh_number_p (s->get_elt_property ("shorten")))
+	s->set_elt_property ("shorten", gh_double2scm (shorten_f));
     }
 }
 
 /*
-  should use minimum energy formulation (cf linespacing)
-*/
+  Set elt properties height and y-position if not set.
+  Adjust stem lengths to reach beam.
+ */
 void
-Beam::solve_slope ()
+Beam::after_line_breaking ()
 {
-  Array<Stem_info> sinfo;
-  for (int j=0; j <stems_.size (); j++)
+  /* first, calculate y, dy */
+  Real y, dy;
+  calc_default_position_and_height (&y, &dy);
+  if (visible_stem_count ())
     {
-      Stem *i = stems_[j];
+      if (suspect_slope_b (y, dy))
+	dy = 0;
 
-      i->set_default_extents ();
-      if (i->invisible_b ())
-	continue;
+      Real damped_dy = calc_slope_damping_f (dy);
+      Real quantised_dy = quantise_dy_f (damped_dy);
 
-      Stem_info info (i);
-      sinfo.push (info);
+      y += (dy - quantised_dy) / 2;
+      dy = quantised_dy;
     }
-  if (! sinfo.size ())
-    slope_f_ = left_y_ = 0;
-  else if (sinfo.size () == 1)
+  /*
+    until here, we used only stem_info, which acts as if dir=up
+   */
+  y *= directional_element (this).get ();
+  dy *= directional_element (this).get ();
+
+  Staff_symbol_referencer_interface st (this);
+  Real half_space = st.staff_space () / 2;
+
+  /* check for user-override of dy */
+  SCM s = remove_elt_property ("height-hs");
+  if (gh_number_p (s))
     {
-      slope_f_ = 0;
-      left_y_ = sinfo[0].idealy_f_;
+      dy = gh_scm2double (s) * half_space;
     }
-  else
-    {
+  set_elt_property ("height", gh_double2scm (dy));
 
-      Real leftx = sinfo[0].x;
-      Least_squares l;
-      for (int i=0; i < sinfo.size (); i++)
+  /* check for user-override of y */
+  s = remove_elt_property ("y-position-hs");
+  if (gh_number_p (s))
+    {
+      y = gh_scm2double (s) * half_space;
+    }
+  else
+    { 
+      /* we can modify y, so we should quantise y */
+      Real y_shift = check_stem_length_f (y, dy);
+      y += y_shift;
+      y = quantise_y_f (y, dy, 0);
+      set_stem_length (y, dy);
+      y_shift = check_stem_length_f (y, dy);
+
+      if (y_shift > half_space / 4)
 	{
-	  sinfo[i].x -= leftx;
-	  l.input.push (Offset (sinfo[i].x, sinfo[i].idealy_f_));
+	  y += y_shift;
+
+	  /*
+	    for significantly lengthened or shortened stems,
+	    request quanting the other way.
+	  */
+	  int quant_dir = 0;
+	  if (abs (y_shift) > half_space / 2)
+	    quant_dir = sign (y_shift) * directional_element (this).get ();
+	  y = quantise_y_f (y, dy, quant_dir);
 	}
-
-      l.minimise (slope_f_, left_y_);
     }
+  // UGH. Y is not in staff position unit?
+  // Ik dacht datwe daar juist van weg wilden?
+  set_stem_length (y, dy);
+  set_elt_property ("y-position", gh_double2scm (y)); 
+}
 
-  Real dy = 0.0;
-  for (int i=0; i < sinfo.size (); i++)
-    {
-      Real y = sinfo[i].x * slope_f_ + left_y_;
-      Real my = sinfo[i].miny_f_;
+/*
+  See Documentation/tex/fonts.doc
+ */
+void
+Beam::calc_default_position_and_height (Real* y, Real* dy) const
+{
+  *y = 0;
+  *dy = 0;  
+  if (visible_stem_count () <= 1)
+    return;
 
-      if (my - y > dy)
-	dy = my -y;
+  Real first_ideal = first_visible_stem ()->calc_stem_info ().idealy_f_;
+  if (first_ideal == last_visible_stem ()->calc_stem_info ().idealy_f_)
+    {
+      *dy = 0;
+      *y = first_ideal;
+      return;
     }
-  left_y_ += dy;
-  left_y_ *= dir_;
 
-  slope_f_ *= dir_;
+  Array<Offset> ideals;
+  Real x0 = first_visible_stem ()->relative_coordinate (0, X_AXIS);
+  for (int i=0; i < stem_count (); i++)
+    {
+      Stem* s = stem (i);
+      if (s->invisible_b ())
+        continue;
+      ideals.push (Offset (s->relative_coordinate (0, X_AXIS) - x0, 
+			   s->calc_stem_info ().idealy_f_));
+    }
+  Real dydx;
+  minimise_least_squares (&dydx, y, ideals); // duh, takes references
 
-  /*
-    This neat trick is by Werner Lemberg, damped = tanh (slope_f_) corresponds
-    with some tables in [Wanske]
-    */
-  if (damping_i_)
-    slope_f_ = 0.6 * tanh (slope_f_) / damping_i_;
-
-  quantise_yspan ();
-
-  // y-values traditionally use internote dimension: therefore slope = (y/in)/x
-  // but mf and beam-lookup use PT dimension for y (as used for x-values)
-  // ugh --- there goes our simplified but careful quantisation
-  Real sl = slope_f_ * paper ()->internote_f ();
-  paper ()->lookup_l ()->beam (sl, 20 PT, 1 PT);
-  slope_f_ = sl / paper ()->internote_f ();
+  Real dx = last_visible_stem ()->relative_coordinate (0, X_AXIS) - x0;
+  *dy = dydx * dx;
 }
 
-void
-Beam::quantise_yspan ()
+bool
+Beam::suspect_slope_b (Real y, Real dy) const
 {
+  /* first, calculate y, dy */
   /*
-    [Ross] (simplification of)
-    Try to set slope_f_ complying with y-span of:
-      - zero
-      - beam_thickness / 2 + staffline_thickness / 2
-      - beam_thickness + staffline_thickness
-    + n * interline
-    */
-
-  if (!quantisation_)
-    return;
+    steep slope running against lengthened stem is suspect
+  */
+  Real first_ideal = first_visible_stem ()->calc_stem_info ().idealy_f_;
+  Real last_ideal = last_visible_stem ()->calc_stem_info ().idealy_f_;
+  Real lengthened = paper_l ()->get_var ("beam_lengthened");
+  Real steep = paper_l ()->get_var ("beam_steep_slope");
 
-  Real interline_f = paper ()->interline_f ();
-  Real internote_f = interline_f / 2;
-  Real staffline_thickness = paper ()->rule_thickness ();
-  Real beam_thickness = 0.48 * (interline_f - staffline_thickness);
-
-  const int QUANTS = 3;
-  Real qdy[QUANTS] = {
-    0,
-    beam_thickness / 2 + staffline_thickness / 2,
-    beam_thickness + staffline_thickness
-  };
-
-  Real xspan_f = stems_.top ()->hpos_f () - stems_[0]->hpos_f ();
-  // y-values traditionally use internote dimension: therefore slope = (y/in)/x
-  Real yspan_f = xspan_f * abs (slope_f_ * internote_f);
-  int yspan_i = (int)(yspan_f / interline_f);
-  Real q = (yspan_f / interline_f - yspan_i) * interline_f;
-  int i = 0;
-  for (; i < QUANTS - 1; i++)
-    if ((q >= qdy[i]) && (q <= qdy[i + 1]))
-      {
-	if (q - qdy[i] < qdy[i + 1] - q)
-	  break;
-	else
-	{ 
-	  i++;
-	  break;
-	}
-      }
-  q = qdy[i];
+  Real dx = last_visible_stem ()->relative_coordinate (0, X_AXIS) - first_visible_stem ()->relative_coordinate (0, X_AXIS);
+  Real dydx = dy && dx ? dy/dx : 0;
 
-  yspan_f = (Real)yspan_i * interline_f + q;
-  // y-values traditionally use internote dimension: therefore slope = (y/in)/x
-  slope_f_ = yspan_f / xspan_f / internote_f * sign (slope_f_);
+  if (((y - first_ideal > lengthened) && (dydx > steep))
+      || ((y + dy - last_ideal > lengthened) && (dydx < -steep)))
+    {
+      return true;
+    }
+  return false;
 }
 
-void
-Beam::quantise_left_y (Beam::Pos pos, bool extend_b)
+/*
+  This neat trick is by Werner Lemberg,
+  damped = tanh (slope)
+  corresponds with some tables in [Wanske]
+*/
+Real
+Beam::calc_slope_damping_f (Real dy) const
 {
-  /*
-   quantising left y should suffice, as slope is quantised too
-   if extend then stems must not get shorter
-   */
+  SCM damp = get_elt_property ("damping"); // remove?
+  int damping = 1;		// ugh.
+  if (gh_number_p (damp))
+    damping = gh_scm2int (damp);
 
-  if (!quantisation_)
-    return;
+  if (damping)
+    {
+      Real dx = last_visible_stem ()->relative_coordinate (0, X_AXIS)
+	- first_visible_stem ()->relative_coordinate (0, X_AXIS);
+      Real dydx = dy && dx ? dy/dx : 0;
+      dydx = 0.6 * tanh (dydx) / damping;
+      return dydx * dx;
+    }
+  return dy;
+}
 
-  Real interline_f = paper ()->interline_f ();
-  Real internote_f = interline_f / 2;
-  Real staffline_thickness = paper ()->rule_thickness ();
-  Real beam_thickness = 0.48 * (interline_f - staffline_thickness);
-
-  const int QUANTS = 7;
-  Real qy[QUANTS] = 
-  {
-    0,
-    beam_thickness / 2,
-    beam_thickness,
-    interline_f / 2 + beam_thickness / 2 + staffline_thickness / 2,
-    interline_f,
-    interline_f + beam_thickness / 2,
-    interline_f + beam_thickness
-  };
-  /* 
-   ugh, using i triggers gcc 2.7.2.1 internal compiler error (far down):
-   for (int i = 0; i < QUANTS; i++)
-   */
+Real
+Beam::calc_stem_y_f (Stem* s, Real y, Real dy) const
+{
+  Real thick = gh_scm2double (get_elt_property ("beam-thickness"));
+  int beam_multiplicity = get_multiplicity ();
+  int stem_multiplicity = (s->flag_i () - 2) >? 0;
+
+  Real interbeam_f = paper_l ()->interbeam_f (beam_multiplicity);
+  Real x0 = first_visible_stem ()->relative_coordinate (0, X_AXIS);
+  Real dx = last_visible_stem ()->relative_coordinate (0, X_AXIS) - x0;
+  Real stem_y = (dy && dx ? (s->relative_coordinate (0, X_AXIS) - x0) / dx * dy : 0) + y;
+
+  /* knee */
+   Direction dir  = directional_element(this).get ();
+   Direction sdir = directional_element (s).get ();
+   
+    /* knee */
+   if (dir!= sdir)
+      {
+       stem_y -= dir 
+	* (thick / 2 + (beam_multiplicity - 1) * interbeam_f);
+
+      Staff_symbol_referencer_interface me (s);
+      Staff_symbol_referencer_interface last (last_visible_stem ());
+      
+      // huh, why not for first visible?
+      if (//(s != first_visible_stem ()) &&
+	  me.staff_symbol_l () != last.staff_symbol_l ())
+	stem_y += directional_element (this).get ()
+	  * (beam_multiplicity - stem_multiplicity) * interbeam_f;
+    }
+  return stem_y;
+}
+
+Real
+Beam::check_stem_length_f (Real y, Real dy) const
+{
+  Real shorten = 0;
+  Real lengthen = 0;
+  Direction dir = directional_element (this).get ();
   
-  // fixme!
-  for (int ii = 0; ii < QUANTS; ii++)
-    qy[ii] -= 0.5 *beam_thickness;
-  Pos qpos[QUANTS] = 
-  {
-    HANG,
-    STRADDLE,
-    SIT,
-    INTER,
-    HANG,
-    STRADDLE,
-    SIT
-  };
-
-  // y-values traditionally use internote dimension
-  Real y = left_y_ * internote_f;
-  int y_i = (int)floor(y / interline_f);
-  y = (y / interline_f - y_i) * interline_f;
-
-  if (y < 0)
-    for (int ii = 0; ii < QUANTS; ii++)
-      qy[ii] -= interline_f;
-
-  int lower_i = 0;
-  int i = 0;
-  for (; i < QUANTS; i++)
+  for (int i=0; i < stem_count (); i++)
     {
-      if (qy[i] > y)
-	break;
-      // found if lower_i is allowed, and nearer (from below) y than new pos
-      if ((pos & qpos[lower_i]) && (y - qy[lower_i] < y - qy[i]))
-        break;
-      // if new pos is allowed or old pos isn't: assign new pos
-      if ((pos & qpos[i]) || !(pos & qpos[lower_i]))
-	lower_i = i;
+      Stem* s = stem (i);
+      if (s->invisible_b ())
+	continue;
+
+      Real stem_y = calc_stem_y_f (s, y, dy);
+	
+      stem_y *= dir;
+      Stem_info info = s->calc_stem_info ();
+
+      // if (0 > info.maxy_f_ - stem_y)
+      shorten = shorten <? info.maxy_f_ - stem_y;
+      // if (0 < info.miny_f_ - stem_y)
+      lengthen = lengthen >? info.miny_f_ - stem_y; 
     }
 
-  int upper_i = QUANTS - 1;
-  for (i = QUANTS - 1; i >= 0; i--)
+  if (lengthen && shorten)
+    warning (_ ("weird beam vertical offset"));
+
+  /* when all stems are too short, normal stems win */
+  return dir * ((shorten) ?  shorten : lengthen);
+}
+
+/*
+  Hmm.  At this time, beam position and slope are determined.  Maybe,
+  stem directions and length should set to relative to the chord's
+  position of the beam.  */
+void
+Beam::set_stem_length (Real y, Real dy)
+{
+  Staff_symbol_referencer_interface st (this);
+  Real half_space = st.staff_space ()/2;
+  for (int i=0; i < stem_count (); i++)
     {
-      if (qy[i] < y)
-	break;
-      // found if upper_i is allowed, and nearer (from above) y than new pos
-      if ((pos & qpos[upper_i]) && (qy[upper_i] - y < qy[i] - y))
-        break;
-      // if new pos is allowed or old pos isn't: assign new pos
-      if ((pos & qpos[i]) || !(pos & qpos[upper_i]))
-	upper_i = i;
+      Stem* s = stem (i);
+      if (s->invisible_b ())
+	continue;
+
+      Real stem_y = calc_stem_y_f (s, y, dy);
+
+      /* caution: stem measures in staff-positions */
+      s->set_stemend ((stem_y + calc_interstaff_dist (s, this)) / half_space);
     }
+}
 
-  // y-values traditionally use internote dimension
-  Real upper_y = (qy[upper_i] + interline_f * y_i) / internote_f;
-  Real lower_y = (qy[lower_i] + interline_f * y_i) / internote_f;
+/*
+  [Ross] (simplification of)
+  Set dy complying with:
+    - zero
+    - thick / 2 + staffline_f / 2
+    - thick + staffline_f
+  + n * staff_space
+*/
+Real
+Beam::quantise_dy_f (Real dy) const
+{
+  Array<Real> a;
+  for (SCM s = scm_eval (ly_symbol2scm ("beam-height-quants")); s !=SCM_EOL; s = gh_cdr (s))
+    a.push (gh_scm2double (gh_car (s)));
+  
+  if (a.size () <= 1)
+    return dy;
 
-  if (extend_b)
-    left_y_ = (dir_ > 0 ? upper_y : lower_y);
-  else
-    left_y_ = (upper_y - y < y - lower_y ? upper_y : lower_y);
+  Staff_symbol_referencer_interface st (this);
+  Real staff_space = st.staff_space ();
+  
+  Interval iv = quantise_iv (a, abs (dy)/staff_space) * staff_space;
+  Real q = (abs (dy) - iv[SMALLER] <= iv[BIGGER] - abs (dy))
+    ? iv[SMALLER]
+    : iv[BIGGER];
+  
+  return q * sign (dy);
 }
 
-void
-Beam::set_stemlens ()
+/*
+  Prevent interference from stafflines and beams.
+  See Documentation/tex/fonts.doc
+
+  We only need to quantise the (left) y-position of the beam,
+  since dy is quantised too.
+  if extend_b then stems must *not* get shorter
+ */
+Real
+Beam::quantise_y_f (Real y, Real dy, int quant_dir)
 {
-  Real x0 = stems_[0]->hpos_f ();
-  Real dy = 0;
-
-  Real interline_f = paper ()->interline_f ();
-  Real internote_f = interline_f / 2;
-  Real staffline_thickness = paper ()->rule_thickness ();
-  Real beam_thickness = 0.48 * (interline_f - staffline_thickness);
-  Real interbeam_f = paper ()->interbeam_f ();
-  if (multiple_i_ > 3)
-    interbeam_f += 2.0 * staffline_thickness / 4;
-  Real xspan_f = stems_.top ()->hpos_f () - stems_[0]->hpos_f ();
-  /*
-   ugh, y values are in "internote" dimension
-   */
-  Real yspan_f = xspan_f * abs (slope_f_ * internote_f);
-  int yspan_i = (int)(yspan_f / interline_f);
+  int multiplicity = get_multiplicity ();
+  Staff_symbol_referencer_interface st (this);
+  Real staff_space = st.staff_space ();
+  SCM quants = scm_eval (gh_list (ly_symbol2scm ("beam-vertical-position-quants"),
+				  gh_int2scm (multiplicity),
+				  gh_double2scm (dy/staff_space),
+				  SCM_UNDEFINED));
 
-  Pos left_pos = NONE;
+  Array<Real> a;
 
-  if ((yspan_f < staffline_thickness / 2) || (quantisation_ == NORMAL))
-    left_pos = (Pos)(STRADDLE | SIT | HANG);
-  else
-    left_pos = (Pos) (sign (slope_f_) > 0 ? STRADDLE | HANG 
-      : SIT | STRADDLE);
+  for (; quants != SCM_EOL; quants = gh_cdr (quants))
+    a.push (gh_scm2double (gh_car (quants)));
 
-  /* 
-   ugh, slope currently mangled by availability mf chars...
-   be more generous regarding beam position between stafflines
-   */
-  Real q = (yspan_f / interline_f - yspan_i) * interline_f;
-  if (q < interline_f / 3 - beam_thickness / 2)
-    left_pos = (Pos) (left_pos | INTER);
+  if (a.size () <= 1)
+    return y;
 
-  if (multiple_i_ > 1)
-    left_pos = (Pos) (dir_ > 0 ? HANG : SIT);
+  Real up_y = directional_element (this).get () * y;
+  Interval iv = quantise_iv (a, up_y/staff_space) * staff_space;
 
-  // ugh, rounding problems!
-  const Real EPSILON = interline_f / 10;
-  do
-    { 
-      left_y_ += dy * dir_;
-      quantise_left_y (left_pos, dy);
-      dy = 0;
-      for (int j=0; j < stems_.size (); j++)
-	{
-	  Stem *s = stems_[j];
-	  if (s->transparent_b_)
-	    continue;
-
-	  Real x = s->hpos_f () - x0;
-	  s->set_stemend (left_y_ + slope_f_ * x);
-	  Real y = s->stem_length_f ();
-	  int mult = max (stems_[j]->beams_left_i_, stems_[j]->beams_right_i_);
-	  if (mult > 1)
-	      // dim(y) = internote
-	      y -= (mult - 1) * interbeam_f / internote_f;
-	  if (y < MINIMUM_STEMLEN[mult])
-	    dy = dy >? (MINIMUM_STEMLEN[mult] - y);
-	}
-    } while (abs (dy) > EPSILON);
+  Real q = up_y - iv[SMALLER] <= iv[BIGGER] - up_y 
+    ? iv[SMALLER] : iv[BIGGER];
+  if (quant_dir)
+    q = iv[(Direction)quant_dir];
+
+  return q * directional_element (this).get ();
 }
 
 void
-Beam::set_grouping (Rhythmic_grouping def, Rhythmic_grouping cur)
+Beam::set_beaming (Beaming_info_list *beaming)
 {
-  def.OK ();
-  cur.OK ();
-  assert (cur.children.size () == stems_.size ());
-
-  cur.split (def);
-
-  Array<int> b;
-  {
-    Array<int> flags;
-    for (int j=0; j <stems_.size (); j++)
-      {
-	Stem *s = stems_[j];
-
-	int f = s->flag_i_ - 2;
-	assert (f>0);
-	flags.push (f);
-      }
-    int fi =0;
-    b= cur.generate_beams (flags, fi);
-    b.insert (0,0);
-    b.push (0);
-    assert (stems_.size () == b.size ()/2);
-  }
-
-  for (int j=0, i=0; i < b.size () && j <stems_.size (); i+= 2, j++)
+  Direction d = LEFT;
+  for (int i=0; i  < stem_count (); i++)
     {
-      Stem *s = stems_[j];
-      s->beams_left_i_ = b[i];
-      s->beams_right_i_ = b[i+1];
-      multiple_i_ = multiple_i_ >? (b[i] >? b[i+1]);
+      do
+	{
+	  if (stem (i)->beam_count (d) == 0)
+	    stem (i)->set_beaming ( beaming->infos_.elem (i).beams_i_drul_[d],d);
+	}
+      while (flip (&d) != LEFT);
     }
 }
 
+
+
 /*
   beams to go with one stem.
+
+  BURP
+  clean  me up.
   */
 Molecule
 Beam::stem_beams (Stem *here, Stem *next, Stem *prev) const
 {
-  assert (!next || next->hpos_f () > here->hpos_f ());
-  assert (!prev || prev->hpos_f () < here->hpos_f ());
-
-  Real staffline_thickness = paper ()->rule_thickness ();
-  Real interbeam_f = paper ()->interbeam_f ();
-  Real internote_f =paper ()->internote_f (); 
-  Real interline_f = 2 * internote_f;
-  Real beamheight_f = 0.48 * (interline_f - staffline_thickness);
-  if (multiple_i_ > 3)
-    interbeam_f += 2.0 * staffline_thickness / 4;
-  Real dy = interbeam_f;
-  Real stemdx = staffline_thickness;
-  Real sl = slope_f_* internote_f;
-  paper ()->lookup_l ()->beam (sl, 20 PT, 1 PT);
+  if ((next && !(next->relative_coordinate (0, X_AXIS) > here->relative_coordinate (0, X_AXIS))) ||
+      (prev && !(prev->relative_coordinate (0, X_AXIS) < here->relative_coordinate (0, X_AXIS))))
+      programming_error ("Beams are not left-to-right");
+
+  Real staffline_f = paper_l ()->get_var ("stafflinethickness");
+  int   multiplicity = get_multiplicity ();
+
+
+  Real interbeam_f = paper_l ()->interbeam_f (multiplicity);
+  Real thick = gh_scm2double (get_elt_property ("beam-thickness"));
+
+  Real bdy = interbeam_f;
+  Real stemdx = staffline_f;
+
+  Real dx = visible_stem_count () ?
+    last_visible_stem ()->relative_coordinate (0, X_AXIS) - first_visible_stem ()->relative_coordinate (0, X_AXIS)
+    : 0.0;
+  Real dy = gh_scm2double (get_elt_property ("height"));
+  Real dydx = dy && dx ? dy/dx : 0;
 
   Molecule leftbeams;
   Molecule rightbeams;
 
+  // UGH
+  Real nw_f;
+  if (!here->first_head ())
+    nw_f = 0;
+  else if (here->type_i ()== 1)
+    nw_f = paper_l ()->get_var ("wholewidth");
+  else if (here->type_i () == 2)
+    nw_f = paper_l ()->get_var ("notewidth") * 0.8;
+  else
+    nw_f = paper_l ()->get_var ("quartwidth");
+
+
+  Direction dir = directional_element (this).get ();
+  
   /* half beams extending to the left. */
   if (prev)
     {
-      int lhalfs= lhalfs = here->beams_left_i_ - prev->beams_right_i_ ;
-      int lwholebeams= here->beams_left_i_ <? prev->beams_right_i_ ;
-      Real w = (here->hpos_f () - prev->hpos_f ())/4 <? paper ()->note_width ();;
-      Atom a;
+      int lhalfs= lhalfs = here->beam_count (LEFT) - prev->beam_count (RIGHT);
+      int lwholebeams= here->beam_count (LEFT) <? prev->beam_count (RIGHT) ;
+      /*
+       Half beam should be one note-width, 
+       but let's make sure two half-beams never touch
+       */
+      Real w = here->relative_coordinate (0, X_AXIS) - prev->relative_coordinate (0, X_AXIS);
+      w = w/2 <? nw_f;
+      Molecule a;
       if (lhalfs)		// generates warnings if not
-	a =  paper ()->lookup_l ()->beam (sl, w, beamheight_f);
-      a.translate (Offset (-w, -w * sl));
+	a =  lookup_l ()->beam (dydx, w, thick);
+      a.translate (Offset (-w, -w * dydx));
       for (int j = 0; j  < lhalfs; j++)
 	{
-	  Atom b (a);
-	  b.translate_axis (-dir_ * dy * (lwholebeams+j), Y_AXIS);
-	  leftbeams.add (b);
+	  Molecule b (a);
+	  b.translate_axis (-dir * bdy * (lwholebeams+j), Y_AXIS);
+	  leftbeams.add_molecule (b);
 	}
     }
 
   if (next)
     {
-      int rhalfs = here->beams_right_i_ - next->beams_left_i_;
-      int rwholebeams = here->beams_right_i_ <? next->beams_left_i_;
+      int rhalfs  = here->beam_count (RIGHT) - next->beam_count (LEFT);
+      int rwholebeams= here->beam_count (RIGHT) <? next->beam_count (LEFT) ;
 
-      Real w = next->hpos_f () - here->hpos_f ();
-      Atom a = paper ()->lookup_l ()->beam (sl, w + stemdx, beamheight_f);
+      Real w = next->relative_coordinate (0, X_AXIS) - here->relative_coordinate (0, X_AXIS);
+      Molecule a = lookup_l ()->beam (dydx, w + stemdx, thick);
       a.translate_axis( - stemdx/2, X_AXIS);
       int j = 0;
       Real gap_f = 0;
-      if (here->beam_gap_i_)
+
+      SCM gap = get_elt_property ("beam-gap");
+      if (gh_number_p (gap))
 	{
-	  int nogap = rwholebeams - here->beam_gap_i_;
+	  int gap_i = gh_scm2int ( (gap));
+	  int nogap = rwholebeams - gap_i;
+	  
 	  for (; j  < nogap; j++)
 	    {
-	      Atom b (a);
-	      b.translate_axis (-dir_ * dy * j, Y_AXIS);
-	      rightbeams.add (b);
+	      Molecule b (a);
+	      b.translate_axis (-dir  * bdy * j, Y_AXIS);
+	      rightbeams.add_molecule (b);
 	    }
 	  // TODO: notehead widths differ for different types
-	  gap_f = paper ()->note_width () / 2;
+	  gap_f = nw_f / 2;
 	  w -= 2 * gap_f;
-	  a = paper ()->lookup_l ()->beam (sl, w + stemdx, beamheight_f);
+	  a = lookup_l ()->beam (dydx, w + stemdx, thick);
 	}
 
       for (; j  < rwholebeams; j++)
 	{
-	  Atom b (a);
-	  b.translate (Offset (gap_f, -dir_ * dy * j));
-	  rightbeams.add (b);
+	  Molecule b (a);
+	  b.translate (Offset (here->invisible_b () ? 0 : gap_f, -dir * bdy * j));
+	  rightbeams.add_molecule (b);
 	}
 
-      w = w/4 <? paper ()->note_width ();
+      w = w/2 <? nw_f;
       if (rhalfs)
-	a = paper ()->lookup_l ()->beam (sl, w, beamheight_f);
+	a = lookup_l ()->beam (dydx, w, thick);
 
       for (; j  < rwholebeams + rhalfs; j++)
 	{
-	  Atom b (a);
-	  b.translate_axis (-dir_ * dy * j, Y_AXIS);
-	  rightbeams.add (b);
+	  Molecule b (a);
+	  b.translate_axis (- dir * bdy * j, Y_AXIS);
+	  rightbeams.add_molecule (b);
 	}
 
     }
-  leftbeams.add (rightbeams);
+  leftbeams.add_molecule (rightbeams);
 
   /*
     Does beam quanting think  of the asymetry of beams? 
     Refpoint is on bottom of symbol. (FIXTHAT) --hwn.
    */
-  if (experimental_features_global_b && dir_ < 0)
-    leftbeams.translate_axis (-beamheight_f, Y_AXIS);
   return leftbeams;
 }
+
+
+Molecule 
+Beam::do_brew_molecule () const
+{
+  Molecule mol;
+  if (!stem_count ())
+    return mol;
+  Real x0,dx;
+  if (visible_stem_count ())
+    {
+      x0 = first_visible_stem ()->relative_coordinate (0, X_AXIS);
+      dx = last_visible_stem ()->relative_coordinate (0, X_AXIS) - x0;
+    }
+  else
+    {
+      x0 = stem (0)->relative_coordinate (0, X_AXIS);
+      dx = stem_top ()->relative_coordinate (0, X_AXIS) - x0;
+    }
+  
+  
+  Real dy = gh_scm2double (get_elt_property ("height"));
+  Real dydx = dy && dx ? dy/dx : 0;
+  Real y = gh_scm2double (get_elt_property ("y-position"));
+  for (int j=0; j <stem_count (); j++)
+    {
+      Stem *i = stem (j);
+      Stem * prev = (j > 0)? stem (j-1) : 0;
+      Stem * next = (j < stem_count ()-1) ? stem (j+1) :0;
+
+      Molecule sb = stem_beams (i, next, prev);
+      Real x = i->relative_coordinate (0, X_AXIS)-x0;
+      sb.translate (Offset (x, x * dydx + y));
+      mol.add_molecule (sb);
+    }
+  mol.translate_axis (x0 
+    - get_bound (LEFT)->relative_coordinate (0, X_AXIS), X_AXIS);
+
+  return mol;
+}
+
+int
+Beam::forced_stem_count () const
+{
+  int f = 0;
+  for (int i=0; i < stem_count (); i++)
+    {
+      Stem *s = stem (i);
+
+      if (s->invisible_b ())
+	continue;
+
+      if (((int)s->chord_start_f ()) 
+        && (s->get_direction () != s->get_default_dir ()))
+        f++;
+    }
+  return f;
+}
+
+/*
+  TODO: Fix this class. This is wildly inefficient.
+  And it sux.  Yet another array/list 'interface'.
+ */
+Stem *
+Beam::stem (int i) const
+{
+  return Group_interface__extract_elements ((Beam*) this, (Stem*) 0, "stems")[i];
+}
+
+int
+Beam::stem_count () const
+{
+  Group_interface gi (this, "stems");
+  return gi.count ();
+}
+
+Stem*
+Beam::stem_top () const
+{
+  SCM s = get_elt_property ("stems");
+  
+  return gh_pair_p (s) ? dynamic_cast<Stem*> (unsmob_element (gh_car (s))) : 0;
+}
+
+/* burp */
+int
+Beam::visible_stem_count () const
+{
+  int c = 0;
+  for (int i = 0; i < stem_count (); i++)
+    {
+      if (!stem (i)->invisible_b ())
+        c++;
+    }
+  return c;
+}
+
+Stem*
+Beam::first_visible_stem () const
+{
+  for (int i = 0; i < stem_count (); i++)
+    {
+      Stem* s = stem (i);
+      if (!s->invisible_b ())
+        return s;
+    }
+  return 0;
+}
+
+Stem*
+Beam::last_visible_stem () const
+{
+  for (int i = stem_count (); i > 0; i--)
+    {
+      Stem* s = stem (i - 1);
+      if (!s->invisible_b ())
+        return s;
+    }
+  return 0;
+}