lily/beam.cc

   1 /*
   2   beam.cc -- implement Beam
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c)  1997--1999 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7     Jan Nieuwenhuizen <janneke@gnu.org>
   8
   9 */
  10
  11 /*
  12   [TODO]
  13     * less hairy code
  14     * move paper vars to scm
  15
  16 */
  17 #include <math.h>               // tanh.
  18
  19 #include "directional-element-interface.hh"
  20 #include "beaming.hh"
  21 #include "dimensions.hh"
  22 #include "beam.hh"
  23 #include "misc.hh"
  24 #include "debug.hh"
  25 #include "leastsquares.hh"
  26 #include "stem.hh"
  27 #include "paper-def.hh"
  28 #include "lookup.hh"
  29 #include "group-interface.hh"
  30 #include "staff-symbol-referencer.hh"
  31 #include "cross-staff.hh"
  32 #include "lily-guile.icc"
  33
  34 Beam::Beam ()
  35 {
  36   Group_interface g (this, "stems");
  37   g.set_interface ();
  38 }
  39
  40 void
  41 Beam::add_stem (Stem*s)
  42 {
  43   Group_interface gi (this, "stems");
  44   gi.add_element (s);
  45
  46   s->add_dependency (this);
  47
  48   assert (!s->beam_l ());
  49   s->set_elt_property ("beam", self_scm_);
  50
  51   if (!spanned_drul_[LEFT])
  52     set_bounds (LEFT,s);
  53   else
  54     set_bounds (RIGHT,s);
  55 }
  56
  57 int
  58 Beam::get_multiplicity () const
  59 {
  60   int m = 0;
  61   for (SCM s = get_elt_property ("stems"); gh_pair_p (s); s = gh_cdr (s))
  62     {
  63       Score_element * sc = unsmob_element (gh_car (s));
  64
  65       if (Stem * st = dynamic_cast<Stem*> (sc))
  66         m = m >? st->beam_count (LEFT) >? st->beam_count (RIGHT);
  67     }
  68   return m;
  69 }
  70
  71 /*
  72   After pre-processing all directions should be set.
  73   Several post-processing routines (stem, slur, script) need stem/beam
  74   direction.
  75   Currenly, this means that beam has set all stem's directions.
  76   [Alternatively, stems could set its own directions, according to
  77    their beam, during 'final-pre-processing'.]
  78  */
  79 void
  80 Beam::do_pre_processing ()
  81 {
  82   // Why?
  83   if (visible_stem_count () < 2)
  84     {
  85       warning (_ ("beam has less than two stems"));
  86       set_elt_property ("transparent", SCM_BOOL_T);
  87     }
  88
  89   if (!directional_element (this).get ())
  90     directional_element (this).set (get_default_dir ());
  91
  92   auto_knees ();
  93   set_stem_directions ();
  94
  95   set_stem_shorten ();
  96 }
  97
  98 /*
  99  FIXME
 100  */
 101 Direction
 102 Beam::get_default_dir () const
 103 {
 104   Drul_array<int> total;
 105   total[UP]  = total[DOWN] = 0;
 106   Drul_array<int> count;
 107   count[UP]  = count[DOWN] = 0;
 108   Direction d = DOWN;
 109
 110   for (int i=0; i <stem_count (); i++)
 111     do { // HUH -- waar slaat dit op?
 112       Stem *s = stem (i);
 113       Direction sd = directional_element (s).get ();
 114       int current = sd  ? (1 + d * sd)/2
 115         : s->get_center_distance ((Direction)-d);
 116
 117       if (current)
 118         {
 119           total[d] += current;
 120           count[d] ++;
 121         }
 122
 123     } while (flip(&d) != DOWN);
 124
 125
 126   SCM s = scm_eval (gh_list (ly_symbol2scm ("beam-dir-algorithm"),
 127                              ly_quote_scm (gh_cons (gh_int2scm (count[UP]),
 128                                                     gh_int2scm (count[DOWN]))),
 129                              ly_quote_scm (gh_cons (gh_int2scm (total[UP]),
 130                                                     gh_int2scm (total[DOWN]))),
 131                              SCM_UNDEFINED));
 132   if (gh_number_p (s) && gh_scm2int (s))
 133     return to_dir (s);
 134
 135   /*
 136     If dir is not determined: get from paper
 137   */
 138   return (Direction)(int)
 139     paper_l ()->get_var ("stem_default_neutral_direction");
 140 }
 141
 142
 143 /*
 144   Set all stems with non-forced direction to beam direction.
 145   Urg: non-forced should become `without/with unforced' direction,
 146        once stem gets cleaned-up.
 147  */
 148 void
 149 Beam::set_stem_directions ()
 150 {
 151   Direction d = directional_element (this).get ();
 152   for (int i=0; i <stem_count (); i++)
 153     {
 154       Stem *s = stem (i);
 155       SCM force = s->remove_elt_property ("dir-forced");
 156       if (!gh_boolean_p (force) || !gh_scm2bool (force))
 157         directional_element (s).set (d);
 158     }
 159 }
 160
 161 void
 162 Beam::auto_knees ()
 163 {
 164   if (!auto_knee ("auto-interstaff-knee-gap", true))
 165     auto_knee ("auto-knee-gap", false);
 166 }
 167
 168 /*
 169   Simplistic auto-knees; only consider vertical gap between two
 170   adjacent chords.
 171
 172   `Forced' stem directions are ignored.  If you don't want auto-knees,
 173   don't set, or unset autoKneeGap/autoInterstaffKneeGap.
 174  */
 175 bool
 176 Beam::auto_knee (String gap_str, bool interstaff_b)
 177 {
 178   bool knee_b = false;
 179   int knee_y = 0;
 180   SCM gap = get_elt_property (gap_str);
 181   Direction d = directional_element (this).get ();
 182
 183   if (gh_number_p (gap))
 184     {
 185       int auto_gap_i = gh_scm2int (gap);
 186       for (int i=1; i < stem_count (); i++)
 187         {
 188           bool is_b = (bool)(calc_interstaff_dist (stem (i), this)
 189             - calc_interstaff_dist (stem (i-1), this));
 190           int l_y = (int)(stem (i-1)->head_positions()[d])
 191             + (int)calc_interstaff_dist (stem (i-1), this);
 192           int r_y = (int)(stem (i)->head_positions()[d])
 193             + (int)calc_interstaff_dist (stem (i), this);
 194           int gap_i = r_y - l_y;
 195
 196           if ((abs (gap_i) >= auto_gap_i) && (!interstaff_b || is_b))
 197             {
 198               knee_y = (r_y + l_y) / 2;
 199               knee_b = true;
 200               break;
 201             }
 202         }
 203     }
 204   if (knee_b)
 205     {
 206       for (int i=0; i < stem_count (); i++)
 207         {
 208           int y = (int)(stem (i)->head_positions()[d])
 209             + (int)calc_interstaff_dist (stem (i), this);
 210           directional_element (stem (i)).set (y < knee_y ? UP : DOWN);
 211           stem (i)->set_elt_property ("dir-forced", SCM_BOOL_T);
 212         }
 213     }
 214   return knee_b;
 215 }
 216
 217 /*
 218  Set stem's shorten property if unset.
 219  TODO:
 220     take some y-position (chord/beam/nearest?) into account
 221     scmify forced-fraction
 222  */
 223 void
 224 Beam::set_stem_shorten ()
 225 {
 226   if (!visible_stem_count ())
 227     return;
 228
 229   Real forced_fraction = forced_stem_count () / visible_stem_count ();
 230   if (forced_fraction < 0.5)
 231     return;
 232
 233   int multiplicity = get_multiplicity ();
 234   // grace stems?
 235   SCM shorten = ly_eval_str ("beamed-stem-shorten");
 236
 237   Array<Real> a;
 238   scm_to_array (shorten, &a);
 239   if (!a.size ())
 240     return;
 241
 242   Staff_symbol_referencer_interface st (this);
 243   Real staff_space = st.staff_space ();
 244   Real shorten_f = a[multiplicity <? (a.size () - 1)] * staff_space;
 245
 246   /* cute, but who invented this -- how to customise ? */
 247   if (forced_fraction < 1)
 248     shorten_f /= 2;
 249
 250   for (int i=0; i < stem_count (); i++)
 251     {
 252       Stem* s = stem (i);
 253       if (s->invisible_b ())
 254         continue;
 255       if (gh_number_p (s->get_elt_property ("shorten")))
 256         s->set_elt_property ("shorten", gh_double2scm (shorten_f));
 257     }
 258 }
 259
 260 /*
 261   Set elt properties height and y-position if not set.
 262   Adjust stem lengths to reach beam.
 263  */
 264 void
 265 Beam::do_post_processing ()
 266 {
 267   /* first, calculate y, dy */
 268   Real y, dy;
 269   calc_position_and_height (&y, &dy);
 270   if (suspect_slope_b (y, dy))
 271     dy = 0;
 272
 273   Real damped_dy = calc_slope_damping_f (dy);
 274   Real quantised_dy = quantise_dy_f (damped_dy);
 275
 276   y += (dy - quantised_dy) / 2;
 277   dy = quantised_dy;
 278
 279   /*
 280     until here, we used only stem_info, which acts as if dir=up
 281    */
 282   y *= directional_element (this).get ();
 283   dy *= directional_element (this).get ();
 284
 285   /* set or read dy as necessary */
 286   SCM s = get_elt_property ("height");
 287   if (gh_number_p (s))
 288     dy = gh_scm2double (s);
 289   else
 290     set_elt_property ("height", gh_double2scm (dy));
 291
 292   /* set or read y as necessary */
 293   s = get_elt_property ("y-position");
 294   if (gh_number_p (s))
 295     {
 296       y = gh_scm2double (s);
 297       set_stem_length (y, dy);
 298     }
 299   else
 300     {
 301       /* we can modify y, so we should quantise y */
 302       Real y_shift = check_stem_length_f (y, dy);
 303       y += y_shift;
 304       y = quantise_y_f (y, dy, 0);
 305       set_stem_length (y, dy);
 306       y_shift = check_stem_length_f (y, dy);
 307
 308       Staff_symbol_referencer_interface st (this);
 309       Real half_space = st.staff_space () / 2;
 310       if (y_shift > half_space / 4)
 311         {
 312           y += y_shift;
 313
 314           /*
 315             for significantly lengthened or shortened stems,
 316             request quanting the other way.
 317           */
 318           int quant_dir = 0;
 319           if (abs (y_shift) > half_space / 2)
 320             quant_dir = sign (y_shift) * directional_element (this).get ();
 321           y = quantise_y_f (y, dy, quant_dir);
 322           set_stem_length (y, dy);
 323         }
 324
 325       set_elt_property ("y-position", gh_double2scm (y));
 326     }
 327 }
 328
 329 /*
 330   See Documentation/tex/fonts.doc
 331  */
 332 void
 333 Beam::calc_position_and_height (Real* y, Real* dy) const
 334 {
 335   *y = *dy = 0;
 336   if (visible_stem_count () <= 1)
 337     return;
 338
 339   Real first_ideal = first_visible_stem ()->calc_stem_info ().idealy_f_;
 340   if (first_ideal == last_visible_stem ()->calc_stem_info ().idealy_f_)
 341     {
 342       *dy = 0;
 343       *y = first_ideal;
 344       return;
 345     }
 346
 347   Least_squares ls;
 348   Real x0 = first_visible_stem ()->hpos_f ();
 349   for (int i=0; i < stem_count (); i++)
 350     {
 351       Stem* s = stem (i);
 352       if (s->invisible_b ())
 353         continue;
 354       ls.input.push (Offset (s->hpos_f () - x0,
 355         s->calc_stem_info ().idealy_f_));
 356     }
 357   Real dydx;
 358   ls.minimise (dydx, *y); // duh, takes references
 359
 360   Real dx = last_visible_stem ()->hpos_f () - x0;
 361   *dy = dydx * dx;
 362 }
 363
 364 bool
 365 Beam::suspect_slope_b (Real y, Real dy) const
 366 {
 367   /*
 368     steep slope running against lengthened stem is suspect
 369   */
 370   Real first_ideal = first_visible_stem ()->calc_stem_info ().idealy_f_;
 371   Real last_ideal = last_visible_stem ()->calc_stem_info ().idealy_f_;
 372   Real lengthened = paper_l ()->get_var ("beam_lengthened");
 373   Real steep = paper_l ()->get_var ("beam_steep_slope");
 374
 375   Real dx = last_visible_stem ()->hpos_f () - first_visible_stem ()->hpos_f ();
 376   Real dydx = dy && dx ? dy/dx : 0;
 377
 378   if (((y - first_ideal > lengthened) && (dydx > steep))
 379       || ((y + dy - last_ideal > lengthened) && (dydx < -steep)))
 380     {
 381       return true;
 382     }
 383   return false;
 384 }
 385
 386 /*
 387   This neat trick is by Werner Lemberg,
 388   damped = tanh (slope)
 389   corresponds with some tables in [Wanske]
 390 */
 391 Real
 392 Beam::calc_slope_damping_f (Real dy) const
 393 {
 394   SCM damp = get_elt_property ("damping"); // remove?
 395   int damping = 1;              // ugh.
 396   if (gh_number_p (damp))
 397     damping = gh_scm2int (damp);
 398
 399   if (damping)
 400     {
 401       Real dx = last_visible_stem ()->hpos_f ()
 402         - first_visible_stem ()->hpos_f ();
 403       Real dydx = dy && dx ? dy/dx : 0;
 404       dydx = 0.6 * tanh (dydx) / damping;
 405       return dydx * dx;
 406     }
 407   return dy;
 408 }
 409
 410 Real
 411 Beam::calc_stem_y_f (Stem* s, Real y, Real dy) const
 412 {
 413   Real thick = gh_scm2double (get_elt_property ("beam-thickness"));
 414   int beam_multiplicity = get_multiplicity ();
 415   int stem_multiplicity = (s->flag_i () - 2) >? 0;
 416
 417   Real interbeam_f = paper_l ()->interbeam_f (beam_multiplicity);
 418   Real x0 = first_visible_stem ()->hpos_f ();
 419   Real dx = last_visible_stem ()->hpos_f () - x0;
 420   Real stem_y = (dy && dx ? (s->hpos_f () - x0) / dx * dy : 0) + y;
 421
 422   /* knee */
 423    Direction dir  = directional_element(this).get ();
 424    Direction sdir = directional_element (s).get ();
 425
 426     /* knee */
 427    if (dir!= sdir)
 428       {
 429        stem_y -= dir
 430         * (thick / 2 + (beam_multiplicity - 1) * interbeam_f);
 431
 432       Staff_symbol_referencer_interface me (s);
 433       Staff_symbol_referencer_interface last (last_visible_stem ());
 434
 435       // huh, why not for first visible?
 436       if (//(s != first_visible_stem ()) &&
 437           me.staff_symbol_l () != last.staff_symbol_l ())
 438         stem_y += directional_element (this).get ()
 439           * (beam_multiplicity - stem_multiplicity) * interbeam_f;
 440     }
 441   return stem_y;
 442 }
 443
 444 Real
 445 Beam::check_stem_length_f (Real y, Real dy) const
 446 {
 447   Real shorten = 0;
 448   Real lengthen = 0;
 449   Direction dir = directional_element (this).get ();
 450
 451   for (int i=0; i < stem_count (); i++)
 452     {
 453       Stem* s = stem (i);
 454       if (s->invisible_b ())
 455         continue;
 456
 457       Real stem_y = calc_stem_y_f (s, y, dy);
 458
 459       stem_y *= dir;
 460       Stem_info info = s->calc_stem_info ();
 461
 462       // if (0 > info.maxy_f_ - stem_y)
 463       shorten = shorten <? info.maxy_f_ - stem_y;
 464       // if (0 < info.miny_f_ - stem_y)
 465       lengthen = lengthen >? info.miny_f_ - stem_y;
 466     }
 467
 468   if (lengthen && shorten)
 469     warning (_ ("weird beam vertical offset"));
 470
 471   /* when all stems are too short, normal stems win */
 472   return dir * ((shorten) ?  shorten : lengthen);
 473 }
 474
 475 /*
 476   Hmm.  At this time, beam position and slope are determined.  Maybe,
 477   stem directions and length should set to relative to the chord's
 478   position of the beam.  */
 479 void
 480 Beam::set_stem_length (Real y, Real dy)
 481 {
 482   Staff_symbol_referencer_interface st (this);
 483   Real half_space = st.staff_space ()/2;
 484   for (int i=0; i < stem_count (); i++)
 485     {
 486       Stem* s = stem (i);
 487       if (s->invisible_b ())
 488         continue;
 489
 490       Real stem_y = calc_stem_y_f (s, y, dy);
 491
 492       /* caution: stem measures in staff-positions */
 493       s->set_stemend ((stem_y + calc_interstaff_dist (s, this)) / half_space);
 494     }
 495 }
 496
 497 /*
 498   [Ross] (simplification of)
 499   Set dy complying with:
 500     - zero
 501     - thick / 2 + staffline_f / 2
 502     - thick + staffline_f
 503   + n * staff_space
 504 */
 505 Real
 506 Beam::quantise_dy_f (Real dy) const
 507 {
 508   SCM quants = ly_eval_str ("beam-height-quants");
 509
 510   Array<Real> a;
 511   scm_to_array (quants, &a);
 512   if (a.size () <= 1)
 513     return dy;
 514
 515   Staff_symbol_referencer_interface st (this);
 516   Real staff_space = st.staff_space ();
 517
 518   Interval iv = quantise_iv (a, abs (dy)/staff_space) * staff_space;
 519   Real q = (abs (dy) - iv[SMALLER] <= iv[BIGGER] - abs (dy))
 520     ? iv[SMALLER]
 521     : iv[BIGGER];
 522
 523   return q * sign (dy);
 524 }
 525
 526 /*
 527   Prevent interference from stafflines and beams.
 528   See Documentation/tex/fonts.doc
 529
 530   We only need to quantise the (left) y-position of the beam,
 531   since dy is quantised too.
 532   if extend_b then stems must *not* get shorter
 533  */
 534 Real
 535 Beam::quantise_y_f (Real y, Real dy, int quant_dir)
 536 {
 537   int multiplicity = get_multiplicity ();
 538   Staff_symbol_referencer_interface st (this);
 539   Real staff_space = st.staff_space ();
 540   SCM quants = scm_eval (gh_list (
 541                                   ly_symbol2scm ("beam-vertical-position-quants"),
 542                                   gh_int2scm (multiplicity),
 543                                   gh_double2scm (dy/staff_space),
 544                                   SCM_UNDEFINED));
 545   Array<Real> a;
 546   scm_to_array (quants, &a);
 547   if (a.size () <= 1)
 548     return y;
 549
 550   Real up_y = directional_element (this).get () * y;
 551   Interval iv = quantise_iv (a, up_y/staff_space) * staff_space;
 552
 553   Real q = up_y - iv[SMALLER] <= iv[BIGGER] - up_y
 554     ? iv[SMALLER] : iv[BIGGER];
 555   if (quant_dir)
 556     q = iv[(Direction)quant_dir];
 557
 558   return q * directional_element (this).get ();
 559 }
 560
 561 void
 562 Beam::set_beaming (Beaming_info_list *beaming)
 563 {
 564   Direction d = LEFT;
 565   for (int i=0; i  < stem_count (); i++)
 566     {
 567       do
 568         {
 569           if (stem (i)->beam_count (d) == 0)
 570             stem (i)->set_beaming ( beaming->infos_.elem (i).beams_i_drul_[d],d);
 571         }
 572       while (flip (&d) != LEFT);
 573     }
 574 }
 575
 576
 577
 578 /*
 579   beams to go with one stem.
 580
 581   BURP
 582   clean  me up.
 583   */
 584 Molecule
 585 Beam::stem_beams (Stem *here, Stem *next, Stem *prev) const
 586 {
 587   if ((next && !(next->hpos_f () > here->hpos_f ())) ||
 588       (prev && !(prev->hpos_f () < here->hpos_f ())))
 589       programming_error ("Beams are not left-to-right");
 590
 591   Real staffline_f = paper_l ()->get_var ("stafflinethickness");
 592   int   multiplicity = get_multiplicity ();
 593
 594
 595   Real interbeam_f = paper_l ()->interbeam_f (multiplicity);
 596   Real thick = gh_scm2double (get_elt_property ("beam-thickness"));;
 597
 598   Real bdy = interbeam_f;
 599   Real stemdx = staffline_f;
 600
 601   Real dx = last_visible_stem ()->hpos_f () - first_visible_stem ()->hpos_f ();
 602   Real dy = get_real ("height");
 603   Real dydx = dy && dx ? dy/dx : 0;
 604
 605   Molecule leftbeams;
 606   Molecule rightbeams;
 607
 608   // UGH
 609   Real nw_f;
 610   if (!here->first_head ())
 611     nw_f = 0;
 612   else if (here->type_i ()== 1)
 613     nw_f = paper_l ()->get_var ("wholewidth");
 614   else if (here->type_i () == 2)
 615     nw_f = paper_l ()->get_var ("notewidth") * 0.8;
 616   else
 617     nw_f = paper_l ()->get_var ("quartwidth");
 618
 619
 620   Direction dir = directional_element (this).get ();
 621
 622   /* half beams extending to the left. */
 623   if (prev)
 624     {
 625       int lhalfs= lhalfs = here->beam_count (LEFT) - prev->beam_count (RIGHT);
 626       int lwholebeams= here->beam_count (LEFT) <? prev->beam_count (RIGHT) ;
 627       /*
 628        Half beam should be one note-width,
 629        but let's make sure two half-beams never touch
 630        */
 631       Real w = here->hpos_f () - prev->hpos_f ();
 632       w = w/2 <? nw_f;
 633       Molecule a;
 634       if (lhalfs)               // generates warnings if not
 635         a =  lookup_l ()->beam (dydx, w, thick);
 636       a.translate (Offset (-w, -w * dydx));
 637       for (int j = 0; j  < lhalfs; j++)
 638         {
 639           Molecule b (a);
 640           b.translate_axis (-dir * bdy * (lwholebeams+j), Y_AXIS);
 641           leftbeams.add_molecule (b);
 642         }
 643     }
 644
 645   if (next)
 646     {
 647       int rhalfs  = here->beam_count (RIGHT) - next->beam_count (LEFT);
 648       int rwholebeams= here->beam_count (RIGHT) <? next->beam_count (LEFT) ;
 649
 650       Real w = next->hpos_f () - here->hpos_f ();
 651       Molecule a = lookup_l ()->beam (dydx, w + stemdx, thick);
 652       a.translate_axis( - stemdx/2, X_AXIS);
 653       int j = 0;
 654       Real gap_f = 0;
 655
 656       SCM gap = get_elt_property ("beam-gap");
 657       if (gh_number_p (gap))
 658         {
 659           int gap_i = gh_scm2int ( (gap));
 660           int nogap = rwholebeams - gap_i;
 661
 662           for (; j  < nogap; j++)
 663             {
 664               Molecule b (a);
 665               b.translate_axis (-dir  * bdy * j, Y_AXIS);
 666               rightbeams.add_molecule (b);
 667             }
 668           // TODO: notehead widths differ for different types
 669           gap_f = nw_f / 2;
 670           w -= 2 * gap_f;
 671           a = lookup_l ()->beam (dydx, w + stemdx, thick);
 672         }
 673
 674       for (; j  < rwholebeams; j++)
 675         {
 676           Molecule b (a);
 677           b.translate (Offset (here->invisible_b () ? 0 : gap_f, -dir * bdy * j));
 678           rightbeams.add_molecule (b);
 679         }
 680
 681       w = w/2 <? nw_f;
 682       if (rhalfs)
 683         a = lookup_l ()->beam (dydx, w, thick);
 684
 685       for (; j  < rwholebeams + rhalfs; j++)
 686         {
 687           Molecule b (a);
 688           b.translate_axis (- dir * bdy * j, Y_AXIS);
 689           rightbeams.add_molecule (b);
 690         }
 691
 692     }
 693   leftbeams.add_molecule (rightbeams);
 694
 695   /*
 696     Does beam quanting think  of the asymetry of beams?
 697     Refpoint is on bottom of symbol. (FIXTHAT) --hwn.
 698    */
 699   return leftbeams;
 700 }
 701
 702
 703 Molecule*
 704 Beam::do_brew_molecule_p () const
 705 {
 706   Molecule *mol_p = new Molecule;
 707   if (!stem_count ())
 708     return mol_p;
 709
 710   Real x0 = first_visible_stem ()->hpos_f ();
 711   Real dx = last_visible_stem ()->hpos_f () - x0;
 712   Real dy = get_real ("height");
 713   Real dydx = dy && dx ? dy/dx : 0;
 714   Real y = get_real ("y-position");
 715   for (int j=0; j <stem_count (); j++)
 716     {
 717       Stem *i = stem (j);
 718       Stem * prev = (j > 0)? stem (j-1) : 0;
 719       Stem * next = (j < stem_count ()-1) ? stem (j+1) :0;
 720
 721       Molecule sb = stem_beams (i, next, prev);
 722       Real x = i->hpos_f ()-x0;
 723       sb.translate (Offset (x, x * dydx + y));
 724       mol_p->add_molecule (sb);
 725     }
 726   mol_p->translate_axis (x0
 727     - spanned_drul_[LEFT]->relative_coordinate (0, X_AXIS), X_AXIS);
 728
 729   return mol_p;
 730 }
 731
 732 int
 733 Beam::forced_stem_count () const
 734 {
 735   int f = 0;
 736   for (int i=0; i < stem_count (); i++)
 737     {
 738       Stem *s = stem (i);
 739
 740       if (s->invisible_b ())
 741         continue;
 742
 743       if (((int)s->chord_start_f ())
 744         && (s->get_direction () != s->get_default_dir ()))
 745         f++;
 746     }
 747   return f;
 748 }
 749
 750
 751
 752 /*
 753   TODO: Fix this class. This is wildly inefficient.
 754   And it sux.  Yet another array/list 'interface'.
 755  */
 756 Stem *
 757 Beam::stem (int i) const
 758 {
 759   return Group_interface__extract_elements ((Beam*) this, (Stem*) 0, "stems")[i];
 760 }
 761
 762 int
 763 Beam::stem_count () const
 764 {
 765   Group_interface gi (this, "stems");
 766   return gi.count ();
 767 }
 768
 769 Stem*
 770 Beam::stem_top () const
 771 {
 772   SCM s = get_elt_property ("stems");
 773
 774   return gh_pair_p (s) ? dynamic_cast<Stem*> (unsmob_element (gh_car (s))) : 0;
 775
 776   //Group_interface__extract_elements ((Beam*) this, (Stem*) 0, "stems")[stem_count () - 1];
 777 }
 778
 779 /* burp */
 780 int
 781 Beam::visible_stem_count () const
 782 {
 783   int c = 0;
 784   for (int i = 0; i < stem_count (); i++)
 785     {
 786       if (!stem (i)->invisible_b ())
 787         c++;
 788     }
 789   return c;
 790 }
 791
 792 Stem*
 793 Beam::first_visible_stem () const
 794 {
 795   for (int i = 0; i < stem_count (); i++)
 796     {
 797       Stem* s = stem (i);
 798       if (!s->invisible_b ())
 799         return s;
 800     }
 801
 802   assert (0);
 803
 804   return 0;
 805 }
 806
 807 Stem*
 808 Beam::last_visible_stem () const
 809 {
 810   for (int i = stem_count (); i > 0; i--)
 811     {
 812       Stem* s = stem (i - 1);
 813       if (!s->invisible_b ())
 814         return s;
 815     }
 816
 817   assert (0);
 818   // sigh
 819   return 0;
 820 }