2 beam.cc -- implement Beam
4 source file of the GNU LilyPond music typesetter
6 (c) 1997--2000 Han-Wen Nienhuys <hanwen@cs.uu.nl>
7 Jan Nieuwenhuizen <janneke@gnu.org>
13 * shorter! (now +- 1000 lines)
15 * move paper vars to scm
17 remove *-hs variables, and do all y-position stuff in staff-space.
21 #include <math.h> // tanh.
23 #include "molecule.hh"
24 #include "directional-element-interface.hh"
28 #include "least-squares.hh"
30 #include "paper-def.hh"
32 #include "group-interface.hh"
33 #include "staff-symbol-referencer.hh"
39 Beam::add_stem (Grob*me, Grob*s)
41 Pointer_group_interface:: add_element(me, "stems", s);
43 s->add_dependency (me);
45 assert (!Stem::beam_l (s));
46 s->set_grob_property ("beam", me->self_scm ());
48 add_bound_item (dynamic_cast<Spanner*> (me), dynamic_cast<Item*> (s));
52 Beam::get_multiplicity (Grob*me)
55 for (SCM s = me->get_grob_property ("stems"); gh_pair_p (s); s = gh_cdr (s))
57 Grob * sc = unsmob_grob (gh_car (s));
59 if (Stem::has_interface (sc))
60 m = m >? Stem::beam_count (sc,LEFT) >? Stem::beam_count (sc,RIGHT);
66 After pre-processing all directions should be set.
67 Several post-processing routines (stem, slur, script) need stem/beam
69 Currenly, this means that beam has set all stem's directions.
70 [Alternatively, stems could set its own directions, according to
71 their beam, during 'final-pre-processing'.]
73 MAKE_SCHEME_CALLBACK(Beam,before_line_breaking,1);
75 Beam::before_line_breaking (SCM smob)
77 Grob * me = unsmob_grob (smob);
80 if (visible_stem_count (me) < 2)
82 warning (_ ("beam has less than two stems"));
85 if (!Directional_element_interface::get (me))
86 Directional_element_interface::set (me, get_default_dir (me));
88 consider_auto_knees (me);
89 set_stem_directions (me);
90 set_stem_shorten (me);
96 Beam::get_default_dir (Grob*me)
98 Drul_array<int> total;
99 total[UP] = total[DOWN] = 0;
100 Drul_array<int> count;
101 count[UP] = count[DOWN] = 0;
104 Link_array<Item> stems=
105 Pointer_group_interface__extract_elements (me, (Item*)0, "stems");
107 for (int i=0; i <stems.size (); i++)
108 do { // HUH -- waar slaat dit op?
110 Direction sd = Directional_element_interface::get (s);
111 int current = sd ? (1 + d * sd)/2
112 : Stem::get_center_distance (s, (Direction)-d);
120 } while (flip(&d) != DOWN);
122 SCM func = me->get_grob_property ("dir-function");
123 SCM s = gh_call2 (func,
124 gh_cons (gh_int2scm (count[UP]),
125 gh_int2scm (count[DOWN])),
126 gh_cons (gh_int2scm (total[UP]),
127 gh_int2scm (total[DOWN])));
129 if (gh_number_p (s) && gh_scm2int (s))
133 If dir is not determined: get default
135 return to_dir (me->get_grob_property ("default-neutral-direction"));
140 Set all stems with non-forced direction to beam direction.
141 Urg: non-forced should become `without/with unforced' direction,
142 once stem gets cleaned-up.
145 Beam::set_stem_directions (Grob*me)
147 Link_array<Item> stems
148 =Pointer_group_interface__extract_elements (me, (Item*) 0, "stems");
149 Direction d = Directional_element_interface::get (me);
151 for (int i=0; i <stems.size (); i++)
154 SCM force = s->remove_grob_property ("dir-forced");
155 if (!gh_boolean_p (force) || !gh_scm2bool (force))
156 Directional_element_interface ::set (s,d);
161 Simplistic auto-knees; only consider vertical gap between two
164 `Forced' stem directions are ignored. If you don't want auto-knees,
165 don't set, or unset auto-knee-gap.
168 Beam::consider_auto_knees (Grob *me)
170 SCM scm = me->get_grob_property ("auto-knee-gap");
172 if (gh_number_p (scm))
176 Real staff_space = Staff_symbol_referencer::staff_space (me);
177 Real gap = gh_scm2double (scm) / staff_space;
179 Direction d = Directional_element_interface::get (me);
180 Link_array<Item> stems=
181 Pointer_group_interface__extract_elements (me, (Item*)0, "stems");
183 Grob *common = me->common_refpoint (stems[0], Y_AXIS);
184 for (int i=1; i < stems.size (); i++)
185 common = common->common_refpoint (stems[i], Y_AXIS);
187 for (int i=1; i < stems.size (); i++)
189 Real left = Stem::extremal_heads (stems[i-1])[d]
190 ->relative_coordinate (common, Y_AXIS);
191 Real right = Stem::extremal_heads (stems[i])[d]
192 ->relative_coordinate (common, Y_AXIS);
194 Real dy = right - left;
198 knee_y = (right + left) / 2;
206 for (int i=0; i < stems.size (); i++)
209 Real y = Stem::extremal_heads (stems[i])[d]
210 ->relative_coordinate (common, Y_AXIS);
212 Directional_element_interface::set (s, y < knee_y ? UP : DOWN);
213 s->set_grob_property ("dir-forced", SCM_BOOL_T);
220 Set stem's shorten property if unset.
222 take some y-position (chord/beam/nearest?) into account
223 scmify forced-fraction
226 Beam::set_stem_shorten (Grob*m)
228 Spanner*me = dynamic_cast<Spanner*> (m);
229 if (!visible_stem_count (me))
232 Real forced_fraction = forced_stem_count (me) / visible_stem_count (me);
233 if (forced_fraction < 0.5)
236 int multiplicity = get_multiplicity (me);
238 SCM shorten = me->get_grob_property ("beamed-stem-shorten");
239 if (shorten == SCM_EOL)
242 int sz = scm_ilength (shorten);
244 Real staff_space = Staff_symbol_referencer::staff_space (me);
245 SCM shorten_elt = scm_list_ref (shorten, gh_int2scm (multiplicity <? (sz - 1)));
246 Real shorten_f = gh_scm2double (shorten_elt) * staff_space;
248 /* cute, but who invented me -- how to customise ? */
249 if (forced_fraction < 1)
252 Link_array<Item> stems=
253 Pointer_group_interface__extract_elements (me, (Item*)0, "stems");
255 for (int i=0; i < stems.size (); i++)
258 if (Stem::invisible_b (s))
260 if (gh_number_p (s->get_grob_property ("shorten")))
261 s->set_grob_property ("shorten", gh_double2scm (shorten_f));
266 Set elt properties height and y-position if not set.
267 Adjust stem lengths to reach beam.
269 MAKE_SCHEME_CALLBACK(Beam,after_line_breaking,1);
271 Beam::after_line_breaking (SCM smob)
273 Grob * me = unsmob_grob (smob);
275 /* first, calculate y, dy */
277 calc_default_position_and_height (me, &y, &dy);
278 if (visible_stem_count (me))
280 if (suspect_slope_b (me, y, dy))
283 Real damped_dy = calc_slope_damping_f (me, dy);
284 Real quantised_dy = quantise_dy_f (me, damped_dy);
286 y += (dy - quantised_dy) / 2;
290 until here, we used only stem_info, which acts as if dir=up
292 y *= Directional_element_interface::get (me);
293 dy *= Directional_element_interface::get (me);
296 Real half_space = Staff_symbol_referencer::staff_space (me) / 2;
298 /* weird: why do we do calc_position_and_height () ? regardless of
302 /* check for user-override of dy */
303 SCM s = me->remove_grob_property ("height-hs");
306 dy = gh_scm2double (s) * half_space;
308 me->set_grob_property ("height", gh_double2scm (dy));
310 /* check for user-override of y */
311 s = me->remove_grob_property ("y-position-hs");
314 y = gh_scm2double (s) * half_space;
318 /* we can modify y, so we should quantise y */
319 Real y_shift = check_stem_length_f (me, y, dy);
321 y = quantise_y_f (me,y, dy, 0);
322 set_stem_length (me, y, dy);
323 y_shift = check_stem_length_f (me, y, dy);
325 if (y_shift > half_space / 4)
330 for significantly lengthened or shortened stems,
331 request quanting the other way.
334 if (abs (y_shift) > half_space / 2)
335 quant_dir = sign (y_shift) * Directional_element_interface::get (me);
336 y = quantise_y_f (me, y, dy, quant_dir);
339 // UGH. Y is not in staff position unit?
340 // Ik dacht datwe daar juist van weg wilden?
341 set_stem_length (me, y, dy);
342 me->set_grob_property ("y-position", gh_double2scm (y));
344 return SCM_UNSPECIFIED;
348 See Documentation/tex/fonts.doc
351 Beam::calc_default_position_and_height (Grob*me,Real* y, Real* dy)
355 if (visible_stem_count (me) <= 1)
358 Real first_ideal = Stem::calc_stem_info (first_visible_stem (me)).idealy_f_;
359 if (first_ideal == Stem::calc_stem_info (last_visible_stem (me)).idealy_f_)
366 Array<Offset> ideals;
368 // ugh -> use commonx
369 Real x0 = first_visible_stem (me)->relative_coordinate (0, X_AXIS);
370 Link_array<Item> stems=
371 Pointer_group_interface__extract_elements (me, (Item*)0, "stems");
373 for (int i=0; i < stems.size (); i++)
376 if (Stem::invisible_b (s))
378 ideals.push (Offset (s->relative_coordinate (0, X_AXIS) - x0,
379 Stem::calc_stem_info (s).idealy_f_));
382 minimise_least_squares (&dydx, y, ideals); // duh, takes references
384 Real dx = last_visible_stem (me)->relative_coordinate (0, X_AXIS) - x0;
389 Beam::suspect_slope_b (Grob*me, Real y, Real dy)
391 /* first, calculate y, dy */
393 steep slope running against lengthened stem is suspect
395 Real first_ideal = Stem::calc_stem_info (first_visible_stem (me)).idealy_f_;
396 Real last_ideal = Stem::calc_stem_info (last_visible_stem (me)).idealy_f_;
397 Real lengthened = gh_scm2double (me->get_grob_property ("outer-stem-length-limit"));
398 Real steep = gh_scm2double (me->get_grob_property ("slope-limit"));
400 // ugh -> use commonx
401 Real dx = last_visible_stem (me)->relative_coordinate (0, X_AXIS) - first_visible_stem (me)->relative_coordinate (0, X_AXIS);
402 Real dydx = dy && dx ? dy/dx : 0;
404 if (((y - first_ideal > lengthened) && (dydx > steep))
405 || ((y + dy - last_ideal > lengthened) && (dydx < -steep)))
413 This neat trick is by Werner Lemberg,
414 damped = tanh (slope)
415 corresponds with some tables in [Wanske]
418 Beam::calc_slope_damping_f (Grob*me,Real dy)
420 SCM damp = me->get_grob_property ("damping");
421 int damping = gh_scm2int (damp);
425 // ugh -> use commonx
426 Real dx = last_visible_stem (me)->relative_coordinate (0, X_AXIS)
427 - first_visible_stem (me)->relative_coordinate (0, X_AXIS);
428 Real dydx = dy && dx ? dy/dx : 0;
429 dydx = 0.6 * tanh (dydx) / damping;
436 Beam::calc_stem_y_f (Grob*me,Item* s, Real y, Real dy)
438 int beam_multiplicity = get_multiplicity (me);
439 int stem_multiplicity = (Stem::flag_i (s) - 2) >? 0;
441 SCM space_proc = me->get_grob_property ("space-function");
442 SCM space = gh_call1 (space_proc, gh_int2scm (beam_multiplicity));
444 Real thick = gh_scm2double (me->get_grob_property ("thickness")) ;
445 Real interbeam_f = gh_scm2double (space) ;
447 // ugh -> use commonx
448 Real x0 = first_visible_stem (me)->relative_coordinate (0, X_AXIS);
449 Real dx = last_visible_stem (me)->relative_coordinate (0, X_AXIS) - x0;
450 Real stem_y = (dy && dx ? (s->relative_coordinate (0, X_AXIS) - x0) / dx * dy : 0) + y;
453 Direction dir = Directional_element_interface::get (me);
454 Direction sdir = Directional_element_interface::get (s);
460 * (thick / 2 + (beam_multiplicity - 1) * interbeam_f);
464 // huh, why not for first visible?
465 if (Staff_symbol_referencer::staff_symbol_l (s)
466 != Staff_symbol_referencer::staff_symbol_l (last_visible_stem (me)))
467 stem_y += Directional_element_interface::get (me)
468 * (beam_multiplicity - stem_multiplicity) * interbeam_f;
475 Beam::check_stem_length_f (Grob*me,Real y, Real dy)
479 Direction dir = Directional_element_interface::get (me);
481 Link_array<Item> stems=
482 Pointer_group_interface__extract_elements (me, (Item*)0, "stems");
484 for (int i=0; i < stems.size(); i++)
487 if (Stem::invisible_b (s))
490 Real stem_y = calc_stem_y_f (me, s, y, dy);
493 Stem_info info = Stem::calc_stem_info (s);
495 // if (0 > info.maxy_f_ - stem_y)
496 shorten = shorten <? info.maxy_f_ - stem_y;
497 // if (0 < info.miny_f_ - stem_y)
498 lengthen = lengthen >? info.miny_f_ - stem_y;
501 if (lengthen && shorten)
502 warning (_ ("weird beam vertical offset"));
504 /* when all stems are too short, normal stems win */
505 return dir * ((shorten) ? shorten : lengthen);
509 Hmm. At this time, beam position and slope are determined. Maybe,
510 stem directions and length should set to relative to the chord's
511 position of the beam. */
513 Beam::set_stem_length (Grob*me,Real y, Real dy)
515 Real half_space = Staff_symbol_referencer::staff_space (me)/2;
516 Link_array<Item> stems=
517 Pointer_group_interface__extract_elements (me, (Item*)0, "stems");
519 Grob *common = me->common_refpoint (stems[0], Y_AXIS);
520 for (int i=1; i < stems.size (); i++)
521 common = common->common_refpoint (stems[i], Y_AXIS);
523 for (int i=0; i < stems.size (); i++)
526 if (Stem::invisible_b (s))
529 Real stem_y = calc_stem_y_f (me, s, y, dy);
531 /* caution: stem measures in staff-positions */
532 Real id = me->relative_coordinate (common, Y_AXIS)
533 - stems[i]->relative_coordinate (common, Y_AXIS);
534 Stem::set_stemend (s, (stem_y + id) / half_space);
539 [Ross] (simplification of)
540 Set dy complying with:
542 - thick / 2 + staffline_f / 2
543 - thick + staffline_f
547 Beam::quantise_dy_f (Grob*me,Real dy)
551 SCM proc = me->get_grob_property ("height-quants");
552 SCM quants = gh_call2 (proc, me->self_scm (),
553 gh_double2scm (me->paper_l ()->get_var ("stafflinethickness")
557 for (SCM s = quants; gh_pair_p (s); s = gh_cdr (s))
558 a.push (gh_scm2double (gh_car (s)));
563 Real staff_space = Staff_symbol_referencer::staff_space (me);
565 Interval iv = quantise_iv (a, abs (dy)/staff_space) * staff_space;
566 Real q = (abs (dy) - iv[SMALLER] <= iv[BIGGER] - abs (dy))
570 return q * sign (dy);
574 Prevent interference from stafflines and beams.
575 See Documentation/tex/fonts.doc
577 We only need to quantise the (left) y-position of the beam,
578 since dy is quantised too.
579 if extend_b then stems must *not* get shorter
582 Beam::quantise_y_f (Grob*me,Real y, Real dy, int quant_dir)
584 int multiplicity = get_multiplicity (me);
586 Real staff_space = Staff_symbol_referencer::staff_space (me);
587 Real thick = me->paper_l ()->get_var ("stafflinethickness");
590 SCM proc = me->get_grob_property ("vertical-position-quant-function");
591 SCM quants = scm_apply (proc,
593 gh_list (gh_int2scm (multiplicity),
594 gh_double2scm (dy/staff_space),
595 gh_double2scm (thick/staff_space),
596 SCM_EOL, SCM_UNDEFINED));
600 for (; gh_pair_p (quants); quants = gh_cdr (quants))
601 a.push (gh_scm2double (gh_car (quants)));
606 Real up_y = Directional_element_interface::get (me) * y;
607 Interval iv = quantise_iv (a, up_y/staff_space) * staff_space;
609 Real q = up_y - iv[SMALLER] <= iv[BIGGER] - up_y
610 ? iv[SMALLER] : iv[BIGGER];
612 q = iv[(Direction)quant_dir];
614 return q * Directional_element_interface::get (me);
618 Beam::set_beaming (Grob*me,Beaming_info_list *beaming)
620 Link_array<Grob> stems=
621 Pointer_group_interface__extract_elements (me, (Grob*)0, "stems");
624 for (int i=0; i < stems.size(); i++)
628 /* Don't overwrite user override (?) */
629 if (Stem::beam_count (stems[i], d) == 0
630 /* Don't set beaming for outside of outer stems */
631 && ! (d == LEFT && i == 0)
632 && ! (d == RIGHT && i == stems.size () -1))
634 int b = beaming->infos_.elem (i).beams_i_drul_[d];
635 Stem::set_beaming (stems[i], b, d);
638 while (flip (&d) != LEFT);
645 beams to go with one stem.
650 Beam::stem_beams (Grob*me,Item *here, Item *next, Item *prev)
652 // ugh -> use commonx
653 if ((next && !(next->relative_coordinate (0, X_AXIS) > here->relative_coordinate (0, X_AXIS))) ||
654 (prev && !(prev->relative_coordinate (0, X_AXIS) < here->relative_coordinate (0, X_AXIS))))
655 programming_error ("Beams are not left-to-right");
657 Real staffline_f = me->paper_l ()->get_var ("stafflinethickness");
658 int multiplicity = get_multiplicity (me);
660 SCM space_proc = me->get_grob_property ("space-function");
661 SCM space = gh_call1 (space_proc, gh_int2scm (multiplicity));
663 Real thick = gh_scm2double (me->get_grob_property ("thickness")) ;
664 Real interbeam_f = gh_scm2double (space) ;
666 Real bdy = interbeam_f;
667 Real stemdx = staffline_f;
669 // ugh -> use commonx
670 Real dx = visible_stem_count (me) ?
671 last_visible_stem (me)->relative_coordinate (0, X_AXIS) - first_visible_stem (me)->relative_coordinate (0, X_AXIS)
673 Real dy = gh_scm2double (me->get_grob_property ("height"));
674 Real dydx = dy && dx ? dy/dx : 0;
680 if (!Stem::first_head (here))
683 int t = Stem::type_i (here);
685 SCM proc = me->get_grob_property ("flag-width-function");
686 SCM result = gh_call1 (proc, gh_int2scm (t));
687 nw_f = gh_scm2double (result);
691 Direction dir = Directional_element_interface::get (me);
693 /* half beams extending to the left. */
696 int lhalfs= lhalfs = Stem::beam_count (here,LEFT) - Stem::beam_count (prev,RIGHT);
697 int lwholebeams= Stem::beam_count (here,LEFT) <? Stem::beam_count (prev,RIGHT) ;
699 Half beam should be one note-width,
700 but let's make sure two half-beams never touch
702 Real w = here->relative_coordinate (0, X_AXIS) - prev->relative_coordinate (0, X_AXIS);
705 if (lhalfs) // generates warnings if not
706 a = Lookup::beam (dydx, w, thick);
707 a.translate (Offset (-w, -w * dydx));
708 for (int j = 0; j < lhalfs; j++)
711 b.translate_axis (-dir * bdy * (lwholebeams+j), Y_AXIS);
712 leftbeams.add_molecule (b);
718 int rhalfs = Stem::beam_count (here,RIGHT) - Stem::beam_count (next,LEFT);
719 int rwholebeams= Stem::beam_count (here,RIGHT) <? Stem::beam_count (next,LEFT) ;
721 Real w = next->relative_coordinate (0, X_AXIS) - here->relative_coordinate (0, X_AXIS);
722 Molecule a = Lookup::beam (dydx, w + stemdx, thick);
723 a.translate_axis( - stemdx/2, X_AXIS);
727 SCM gap = me->get_grob_property ("gap");
728 if (gh_number_p (gap))
730 int gap_i = gh_scm2int ( (gap));
731 int nogap = rwholebeams - gap_i;
733 for (; j < nogap; j++)
736 b.translate_axis (-dir * bdy * j, Y_AXIS);
737 rightbeams.add_molecule (b);
739 // TODO: notehead widths differ for different types
742 a = Lookup::beam (dydx, w + stemdx, thick);
745 for (; j < rwholebeams; j++)
748 b.translate (Offset (Stem::invisible_b (here) ? 0 : gap_f, -dir * bdy * j));
749 rightbeams.add_molecule (b);
754 a = Lookup::beam (dydx, w, thick);
756 for (; j < rwholebeams + rhalfs; j++)
759 b.translate_axis (- dir * bdy * j, Y_AXIS);
760 rightbeams.add_molecule (b);
764 leftbeams.add_molecule (rightbeams);
767 Does beam quanting think of the asymetry of beams?
768 Refpoint is on bottom of symbol. (FIXTHAT) --hwn.
774 TODO: it would be nice to introduce y-position via callbacks.
777 MAKE_SCHEME_CALLBACK(Beam,brew_molecule,1);
779 Beam::brew_molecule (SCM smob)
781 Grob * me =unsmob_grob (smob);
784 if (!gh_pair_p (me->get_grob_property ("stems")))
787 Link_array<Item>stems =
788 Pointer_group_interface__extract_elements (me, (Item*) 0, "stems");
789 if (visible_stem_count (me))
791 // ugh -> use commonx
792 x0 = first_visible_stem (me)->relative_coordinate (0, X_AXIS);
793 dx = last_visible_stem (me)->relative_coordinate (0, X_AXIS) - x0;
797 x0 = stems[0]->relative_coordinate (0, X_AXIS);
798 dx = stems.top()->relative_coordinate (0, X_AXIS) - x0;
802 Real dy = gh_scm2double (me->get_grob_property ("height"));
803 Real dydx = dy && dx ? dy/dx : 0;
804 Real y = gh_scm2double (me->get_grob_property ("y-position"));
807 for (int j=0; j <stems.size (); j++)
810 Item * prev = (j > 0)? stems[j-1] : 0;
811 Item * next = (j < stems.size()-1) ? stems[j+1] :0;
813 Molecule sb = stem_beams (me, i, next, prev);
814 Real x = i->relative_coordinate (0, X_AXIS)-x0;
815 sb.translate (Offset (x, x * dydx + y));
816 mol.add_molecule (sb);
818 mol.translate_axis (x0
819 - dynamic_cast<Spanner*> (me)->get_bound (LEFT)->relative_coordinate (0, X_AXIS), X_AXIS);
821 return mol.smobbed_copy ();
825 Beam::forced_stem_count (Grob*me)
827 Link_array<Item>stems =
828 Pointer_group_interface__extract_elements ( me, (Item*) 0, "stems");
830 for (int i=0; i < stems.size (); i++)
834 if (Stem::invisible_b (s))
837 if (((int)Stem::chord_start_f (s))
838 && (Stem::get_direction (s ) != Stem::get_default_dir (s )))
848 use filter and standard list functions.
851 Beam::visible_stem_count (Grob*me)
853 Link_array<Item>stems =
854 Pointer_group_interface__extract_elements (me, (Item*) 0, "stems");
856 for (int i = stems.size (); i--;)
858 if (!Stem::invisible_b (stems[i]))
865 Beam::first_visible_stem(Grob*me)
867 Link_array<Item>stems =
868 Pointer_group_interface__extract_elements ( me, (Item*) 0, "stems");
870 for (int i = 0; i < stems.size (); i++)
872 if (!Stem::invisible_b (stems[i]))
879 Beam::last_visible_stem(Grob*me)
881 Link_array<Item>stems =
882 Pointer_group_interface__extract_elements ( me, (Item*) 0, "stems");
883 for (int i = stems.size (); i--;)
885 if (!Stem::invisible_b (stems[i]))
894 handle rest under beam (do_post: beams are calculated now)
895 what about combination of collisions and rest under beam.
899 rest -> stem -> beam -> interpolate_y_position ()
901 MAKE_SCHEME_CALLBACK(Beam,rest_collision_callback,2);
903 Beam::rest_collision_callback (SCM element_smob, SCM axis)
905 Grob *rest = unsmob_grob (element_smob);
906 Axis a = (Axis) gh_scm2int (axis);
908 assert (a == Y_AXIS);
910 Grob * st = unsmob_grob (rest->get_grob_property ("stem"));
913 return gh_double2scm (0.0);
914 Grob * beam = unsmob_grob (stem->get_grob_property ("beam"));
915 if (!beam || !Beam::has_interface (beam) || !Beam::visible_stem_count (beam))
916 return gh_double2scm (0.0);
918 // make callback for rest from this.
923 // todo: make sure this calced already.
924 SCM s = beam->get_grob_property ("height");
926 beam_dy = gh_scm2double (s);
928 s = beam->get_grob_property ("y-position");
930 beam_y = gh_scm2double (s);
932 // ugh -> use commonx
933 Real x0 = first_visible_stem(beam)->relative_coordinate (0, X_AXIS);
934 Real dx = last_visible_stem(beam)->relative_coordinate (0, X_AXIS) - x0;
935 Real dydx = beam_dy && dx ? beam_dy/dx : 0;
937 Direction d = Stem::get_direction (stem);
938 Real beamy = (stem->relative_coordinate (0, X_AXIS) - x0) * dydx + beam_y;
940 Real staff_space = Staff_symbol_referencer::staff_space (rest);
943 Real rest_dim = rest->extent (rest, Y_AXIS)[d]*2.0 / staff_space ; // refp??
946 = gh_scm2double (rest->get_grob_property ("minimum-beam-collision-distance"));
948 minimum_dist + -d * (beamy - rest_dim) >? 0;
950 int stafflines = Staff_symbol_referencer::line_count (rest);
952 // move discretely by half spaces.
953 int discrete_dist = int (ceil (dist));
955 // move by whole spaces inside the staff.
956 if (discrete_dist < stafflines+1)
957 discrete_dist = int (ceil (discrete_dist / 2.0)* 2.0);
959 return gh_double2scm (-d * discrete_dist);
964 Beam::has_interface (Grob*me)
966 return me->has_interface (ly_symbol2scm ("beam-interface"));
970 Beam::set_interface (Grob*me)
973 why the init? No way to tell difference between default and user
975 me->set_grob_property ("height", gh_int2scm (0)); // ugh.
976 me->set_grob_property ("y-position" ,gh_int2scm (0));
977 me->set_interface (ly_symbol2scm("beam-interface"));