lily/grob.cc

   1 /*
   2   grob.cc -- implement Grob
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c)  1997--2003 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7 */
   8
   9
  10 #include <string.h>
  11 #include <math.h>
  12
  13 #include "main.hh"
  14 #include "input-smob.hh"
  15 #include "warn.hh"
  16 #include "group-interface.hh"
  17 #include "misc.hh"
  18 #include "paper-score.hh"
  19 #include "molecule.hh"
  20 #include "grob.hh"
  21 #include "warn.hh"
  22 #include "spanner.hh"
  23 #include "system.hh"
  24 #include "item.hh"
  25 #include "molecule.hh"
  26 #include "misc.hh"
  27 #include "music.hh"
  28 #include "item.hh"
  29
  30 #include "ly-smobs.icc"
  31
  32 /*
  33 TODO:
  34
  35 remove dynamic_cast<Spanner,Item> and put this code into respective
  36   subclass.
  37 */
  38
  39 //#define HASHING_FOR_MUTABLE_PROPS
  40 #define HASH_SIZE 3
  41 #define INFINITY_MSG "Infinity or NaN encountered"
  42
  43 Grob::Grob (SCM basicprops)
  44 {
  45   /*
  46     fixme: default should be no callback.
  47    */
  48   self_scm_ = SCM_EOL;
  49   pscore_=0;
  50   status_ = 0;
  51   original_ = 0;
  52   immutable_property_alist_ =  basicprops;
  53   mutable_property_alist_ = SCM_EOL;
  54
  55   /*
  56     We do smobify_self() as the first step. Since the object lives on
  57     the heap, none of its SCM variables are protected from GC. After
  58     smobify_self(), they are.
  59    */
  60   smobify_self ();
  61
  62
  63 #ifdef HASHING_FOR_MUTABLE_PROPS
  64   mutable_property_alist_ = scm_c_make_hash_table (HASH_SIZE);
  65 #endif
  66
  67   SCM meta = get_grob_property ("meta");
  68   if (gh_pair_p (meta))
  69     {
  70       SCM ifs = scm_assoc (ly_symbol2scm ("interfaces"), meta);
  71
  72       /*
  73         Switch off interface checks for the moment.
  74        */
  75       bool itc = internal_type_checking_global_b;
  76       internal_type_checking_global_b = false;
  77       internal_set_grob_property (ly_symbol2scm ("interfaces"), gh_cdr(ifs));
  78       internal_type_checking_global_b = itc;
  79     }
  80
  81   /*
  82     TODO:
  83
  84     destill this into a function, so we can re-init the immutable
  85     properties with a new BASICPROPS value after creation. Convenient
  86     eg. when using \override with StaffSymbol.  */
  87
  88   char const*onames[] = {"X-offset-callbacks", "Y-offset-callbacks"};
  89   char const*enames[] = {"X-extent-callback", "Y-extent-callback"};
  90
  91   for (int a = X_AXIS; a <= Y_AXIS; a++)
  92     {
  93       SCM l = get_grob_property (onames[a]);
  94
  95       if (scm_ilength (l) >=0)
  96         {
  97           dim_cache_[a].offset_callbacks_ = l;
  98           dim_cache_[a].offsets_left_ = scm_ilength (l);
  99         }
 100       else
 101         {
 102           programming_error ("[XY]-offset-callbacks must be a list");
 103         }
 104
 105       SCM cb = get_grob_property (enames[a]);
 106
 107       /*
 108         Should change default to be empty?
 109       */
 110       if (cb != SCM_BOOL_F
 111           && !gh_procedure_p (cb) && !gh_pair_p (cb)
 112           && gh_procedure_p (get_grob_property ("molecule-callback"))
 113           )
 114         cb = molecule_extent_proc;
 115
 116       dim_cache_[a].dimension_ = cb;
 117     }
 118
 119 }
 120
 121 Grob::Grob (Grob const&s)
 122    : dim_cache_ (s.dim_cache_)
 123 {
 124   original_ = (Grob*) &s;
 125   self_scm_ = SCM_EOL;
 126
 127   immutable_property_alist_ = s.immutable_property_alist_;
 128
 129   mutable_property_alist_ = SCM_EOL;
 130
 131   /*
 132     No properties are copied. That is the job of handle_broken_dependencies.
 133    */
 134
 135   status_ = s.status_;
 136   pscore_ = s.pscore_;
 137
 138   smobify_self ();
 139
 140 #ifdef HASHING_FOR_MUTABLE_PROPS
 141   mutable_property_alist_ = scm_c_make_hash_table (HASH_SIZE);
 142 #endif
 143 }
 144
 145 Grob::~Grob ()
 146 {
 147   /*
 148     do nothing scm-ish and no unprotecting here.
 149    */
 150 }
 151
 152
 153
 154
 155
 156 MAKE_SCHEME_CALLBACK (Grob,molecule_extent,2);
 157 SCM
 158 Grob::molecule_extent (SCM element_smob, SCM scm_axis)
 159 {
 160   Grob *s = unsmob_grob (element_smob);
 161   Axis a = (Axis) gh_scm2int (scm_axis);
 162
 163   Molecule *m = s->get_molecule ();
 164   Interval e ;
 165   if (m)
 166     e = m->extent (a);
 167   return ly_interval2scm (e);
 168 }
 169
 170 MAKE_SCHEME_CALLBACK (Grob,preset_extent,2);
 171 SCM
 172 Grob::preset_extent (SCM element_smob, SCM scm_axis)
 173 {
 174   Grob *s = unsmob_grob (element_smob);
 175   Axis a = (Axis) gh_scm2int (scm_axis);
 176
 177   SCM ext = s->get_grob_property ((a == X_AXIS)
 178                                  ? "X-extent"
 179                                  : "Y-extent");
 180
 181   if (gh_pair_p (ext))
 182     {
 183       Real l = gh_scm2double (ly_car (ext));
 184       Real r = gh_scm2double (ly_cdr (ext));
 185       return ly_interval2scm (Interval (l, r));
 186     }
 187
 188   return ly_interval2scm (Interval ());
 189 }
 190
 191
 192
 193 Paper_def*
 194 Grob::get_paper ()  const
 195 {
 196  return pscore_ ? pscore_->paper_ : 0;
 197 }
 198
 199 void
 200 Grob::calculate_dependencies (int final, int busy, SCM funcname)
 201 {
 202   if (status_ >= final)
 203     return;
 204
 205   if (status_== busy)
 206     {
 207       programming_error ("Element is busy, come back later");
 208       return;
 209     }
 210
 211   status_= busy;
 212
 213   for (SCM d = get_grob_property ("dependencies"); gh_pair_p (d);
 214        d = ly_cdr (d))
 215     {
 216       unsmob_grob (ly_car (d))
 217         ->calculate_dependencies (final, busy, funcname);
 218     }
 219
 220
 221   SCM proc = internal_get_grob_property (funcname);
 222   if (gh_procedure_p (proc))
 223     gh_call1 (proc, this->self_scm ());
 224
 225   status_= final;
 226 }
 227
 228 Molecule *
 229 Grob::get_molecule ()  const
 230 {
 231   if (!live())
 232     {
 233       return 0;
 234
 235     }
 236
 237   SCM mol = get_grob_property ("molecule");
 238   if (unsmob_molecule (mol))
 239     return unsmob_molecule (mol);
 240
 241   mol =  get_uncached_molecule ();
 242
 243   if (live ())
 244     {
 245       Grob *me = (Grob*)this;
 246       me->set_grob_property ("molecule", mol);
 247     }
 248
 249   return unsmob_molecule (mol);
 250 }
 251
 252 SCM
 253 Grob::get_uncached_molecule ()const
 254 {
 255   SCM proc = get_grob_property ("molecule-callback");
 256
 257   SCM  mol = SCM_EOL;
 258   if (gh_procedure_p (proc))
 259     mol = gh_apply (proc, scm_list_n (this->self_scm (), SCM_UNDEFINED));
 260
 261   Molecule *m = unsmob_molecule (mol);
 262
 263   if (unsmob_molecule (mol))
 264     {
 265       SCM origin = ly_symbol2scm ("no-origin");
 266
 267       if (store_locations_global_b)
 268         {
 269           SCM cause = get_grob_property ("cause");
 270           if (Music*m = unsmob_music (cause))
 271             {
 272               SCM music_origin = m->get_mus_property ("origin");
 273               if (unsmob_input (music_origin))
 274                 origin = music_origin;
 275             }
 276       }
 277
 278       // ugr.
 279
 280       mol = Molecule (m->extent_box (),
 281                       scm_list_n (origin, m->get_expr (), SCM_UNDEFINED)
 282                       ). smobbed_copy ();
 283
 284       m = unsmob_molecule (mol);
 285     }
 286
 287   /*
 288     transparent retains dimensions of element.
 289    */
 290   if (m && to_boolean (get_grob_property ("transparent")))
 291     mol = Molecule (m->extent_box (), SCM_EOL).smobbed_copy ();
 292
 293   return mol;
 294 }
 295
 296 /*
 297
 298   VIRTUAL STUBS
 299
 300  */
 301 void
 302 Grob::do_break_processing ()
 303 {
 304 }
 305
 306 System *
 307 Grob::get_system () const
 308 {
 309   return 0;
 310 }
 311
 312 void
 313 Grob::add_dependency (Grob*e)
 314 {
 315   if (e)
 316     {
 317       Pointer_group_interface::add_grob (this, ly_symbol2scm ("dependencies"),e);
 318     }
 319   else
 320     programming_error ("Null dependency added");
 321 }
 322
 323
 324 void
 325 Grob::handle_broken_dependencies ()
 326 {
 327   Spanner * sp = dynamic_cast<Spanner*> (this);
 328   if (original_ && sp)
 329     return;
 330
 331   if (sp)
 332     {
 333       for (SCM s = mutable_property_alist_; gh_pair_p(s);
 334            s = gh_cdr(s))
 335         {
 336           sp->substitute_one_mutable_property (gh_caar (s),
 337                                               gh_cdar (s));
 338
 339         }
 340     }
 341
 342   System *system = get_system ();
 343
 344   if (live ()
 345       && system && common_refpoint (system, X_AXIS) && common_refpoint (system, Y_AXIS))
 346     {
 347       substitute_mutable_properties (system ? system->self_scm () : SCM_UNDEFINED,
 348                                      mutable_property_alist_);
 349     }
 350   else if (dynamic_cast <System*> (this))
 351     {
 352       substitute_mutable_properties (SCM_UNDEFINED, mutable_property_alist_);
 353     }
 354   else
 355     {
 356       /*
 357         This element is `invalid'; it has been removed from all
 358         dependencies, so let's junk the element itself.
 359
 360         do not do this for System, since that would remove references
 361         to the originals of score-grobs, which get then GC'd (a bad
 362         thing.)
 363
 364       */
 365       suicide ();
 366     }
 367 }
 368
 369 /*
 370  Note that we still want references to this element to be
 371  rearranged, and not silently thrown away, so we keep pointers
 372  like {broken_into_{drul,array}, original}
 373 */
 374 void
 375 Grob::suicide ()
 376 {
 377   if (!live ())
 378     return;
 379
 380 #if 0 // see below.
 381    String nm = name();
 382 #endif
 383
 384   mutable_property_alist_ = SCM_EOL;
 385   immutable_property_alist_ = SCM_EOL;
 386
 387   set_extent (SCM_EOL, Y_AXIS);
 388   set_extent (SCM_EOL, X_AXIS);
 389
 390   for (int a= X_AXIS; a <= Y_AXIS; a++)
 391     {
 392       dim_cache_[a].offset_callbacks_ = SCM_EOL;
 393       dim_cache_[a].offsets_left_ = 0;
 394     }
 395
 396 #if 0
 397   /*
 398     This can make debugging a little easier: we can still know what
 399     the object used to be. However, since all its links have been
 400     broken, it's usually more convenient to set a conditional
 401     breakpoint in GDB before the property lists are wiped.
 402    */
 403   mutable_property_alist_ = scm_acons (ly_symbol2scm ("name"),
 404                                        scm_makfrom0str (nm.to_str0()),
 405                                        mutable_property_alist_
 406                                        );
 407 #endif
 408 }
 409
 410 void
 411 Grob::handle_prebroken_dependencies ()
 412 {
 413   /*
 414     Don't do this in the derived method, since we want to keep access to
 415     mutable_property_alist_ centralized.
 416    */
 417   if (original_)
 418     {
 419       Item * it = dynamic_cast<Item*> (this);
 420       substitute_mutable_properties (gh_int2scm (it->break_status_dir ()),
 421                                original_->mutable_property_alist_);
 422     }
 423 }
 424
 425 Grob*
 426 Grob::find_broken_piece (System*) const
 427 {
 428   return 0;
 429 }
 430
 431 /*
 432   translate in one direction
 433 */
 434 void
 435 Grob::translate_axis (Real y, Axis a)
 436 {
 437   if (isinf (y) || isnan (y))
 438     programming_error (_ (INFINITY_MSG));
 439   else
 440     {
 441       dim_cache_[a].offset_ += y;
 442     }
 443 }
 444
 445
 446 /*
 447   Find the offset relative to D.  If   D equals THIS, then it is 0.
 448   Otherwise, it recursively defd as
 449
 450   OFFSET_ + PARENT_L_->relative_coordinate (D)
 451 */
 452 Real
 453 Grob::relative_coordinate (Grob const*refp, Axis a) const
 454 {
 455   if (refp == this)
 456     return 0.0;
 457
 458   /*
 459     We catch PARENT_L_ == nil case with this, but we crash if we did
 460     not ask for the absolute coordinate (ie. REFP == nil.)
 461
 462    */
 463   if (refp == dim_cache_[a].parent_)
 464     return get_offset (a);
 465   else
 466     return get_offset (a) + dim_cache_[a].parent_->relative_coordinate (refp, a);
 467 }
 468
 469
 470
 471 /*
 472   Invoke callbacks to get offset relative to parent.
 473 */
 474 Real
 475 Grob::get_offset (Axis a) const
 476 {
 477   Grob *me = (Grob*) this;
 478   while (dim_cache_[a].offsets_left_)
 479     {
 480       int l = --me->dim_cache_[a].offsets_left_;
 481       SCM cb = scm_list_ref (dim_cache_[a].offset_callbacks_,  gh_int2scm (l));
 482       SCM retval = gh_call2 (cb, self_scm (), gh_int2scm (a));
 483
 484       Real r =  gh_scm2double (retval);
 485       if (isinf (r) || isnan (r))
 486         {
 487           programming_error (INFINITY_MSG);
 488           r = 0.0;
 489         }
 490       me->dim_cache_[a].offset_ +=r;
 491     }
 492   return dim_cache_[a].offset_;
 493 }
 494
 495
 496 MAKE_SCHEME_CALLBACK (Grob,point_dimension_callback,2);
 497 SCM
 498 Grob::point_dimension_callback (SCM , SCM)
 499 {
 500   return ly_interval2scm (Interval (0,0));
 501 }
 502
 503 bool
 504 Grob::empty_b (Axis a)const
 505 {
 506   return ! (gh_pair_p (dim_cache_[a].dimension_) ||
 507             gh_procedure_p (dim_cache_[a].dimension_));
 508 }
 509
 510 Interval
 511 Grob::extent (Grob * refp, Axis a) const
 512 {
 513   Real x = relative_coordinate (refp, a);
 514
 515
 516   Dimension_cache * d = (Dimension_cache *)&dim_cache_[a];
 517   Interval ext ;
 518   if (gh_pair_p (d->dimension_))
 519     ;
 520   else if (gh_procedure_p (d->dimension_))
 521     {
 522       /*
 523         FIXME: add doco on types, and should typecheck maybe?
 524        */
 525       d->dimension_= gh_call2 (d->dimension_, self_scm (), gh_int2scm (a));
 526     }
 527   else
 528     return ext;
 529
 530   if (!gh_pair_p (d->dimension_))
 531     return ext;
 532
 533   ext = ly_scm2interval (d->dimension_);
 534
 535   SCM extra = get_grob_property (a == X_AXIS
 536                                 ? "extra-X-extent"
 537                                 : "extra-Y-extent");
 538
 539   /*
 540     signs ?
 541    */
 542   if (gh_pair_p (extra))
 543     {
 544       ext[BIGGER] +=  gh_scm2double (ly_cdr (extra));
 545       ext[SMALLER] +=   gh_scm2double (ly_car (extra));
 546     }
 547
 548   extra = get_grob_property (a == X_AXIS
 549                                 ? "minimum-X-extent"
 550                                 : "minimum-Y-extent");
 551   if (gh_pair_p (extra))
 552     {
 553       ext.unite (Interval (gh_scm2double (ly_car (extra)),
 554                            gh_scm2double (ly_cdr (extra))));
 555     }
 556
 557   ext.translate (x);
 558
 559   return ext;
 560 }
 561
 562 /*
 563   Find the group-element which has both #this# and #s#
 564 */
 565 Grob *
 566 Grob::common_refpoint (Grob const* s, Axis a) const
 567 {
 568   /*
 569     I don't like the quadratic aspect of this code, but I see no other
 570     way. The largest chain of parents might be 10 high or so, so
 571     it shouldn't be a real issue. */
 572   for (Grob const *c = this; c; c = c->dim_cache_[a].parent_)
 573     for (Grob const * d = s; d; d = d->dim_cache_[a].parent_)
 574       if (d == c)
 575         return (Grob*)d;
 576
 577   return 0;
 578 }
 579
 580
 581 Grob *
 582 common_refpoint_of_list (SCM elist, Grob *common, Axis a)
 583 {
 584   for (; gh_pair_p (elist); elist = ly_cdr (elist))
 585     {
 586       Grob * s = unsmob_grob (ly_car (elist));
 587       if (!s)
 588         continue;
 589       if (common)
 590         common = common->common_refpoint (s, a);
 591       else
 592         common = s;
 593     }
 594
 595   return common;
 596 }
 597
 598
 599
 600 Grob *
 601 common_refpoint_of_array (Link_array<Grob> const &arr, Grob *common, Axis a)
 602 {
 603   for (int i = arr.size() ; i--; )
 604     {
 605       Grob * s = arr[i];
 606       if (!s)
 607         continue;
 608
 609       if (common)
 610         common = common->common_refpoint (s, a);
 611       else
 612         common = s;
 613     }
 614
 615   return common;
 616 }
 617
 618 String
 619 Grob::name () const
 620 {
 621   SCM meta = get_grob_property ("meta");
 622   SCM nm = scm_assoc (ly_symbol2scm ("name"), meta);
 623   nm = (gh_pair_p (nm)) ? ly_cdr (nm) : SCM_EOL;
 624   return  gh_symbol_p (nm) ? ly_symbol2string (nm) :  classname (this);
 625 }
 626
 627 void
 628 Grob::add_offset_callback (SCM cb, Axis a)
 629 {
 630   if (!has_offset_callback_b (cb, a))
 631   {
 632     dim_cache_[a].offset_callbacks_ = gh_cons (cb, dim_cache_[a].offset_callbacks_);
 633     dim_cache_[a].offsets_left_ ++;
 634   }
 635 }
 636
 637 bool
 638 Grob::has_extent_callback_b (SCM cb, Axis a)const
 639 {
 640   return scm_equal_p (cb, dim_cache_[a].dimension_) == SCM_BOOL_T;
 641 }
 642
 643
 644 bool
 645 Grob::has_offset_callback_b (SCM cb, Axis a)const
 646 {
 647   return scm_memq (cb, dim_cache_[a].offset_callbacks_) != SCM_BOOL_F;
 648 }
 649
 650 void
 651 Grob::set_extent (SCM dc, Axis a)
 652 {
 653   dim_cache_[a].dimension_ =dc;
 654 }
 655
 656 void
 657 Grob::set_parent (Grob *g, Axis a)
 658 {
 659   dim_cache_[a].parent_ = g;
 660 }
 661
 662 MAKE_SCHEME_CALLBACK (Grob,fixup_refpoint,1);
 663 SCM
 664 Grob::fixup_refpoint (SCM smob)
 665 {
 666   Grob *me = unsmob_grob (smob);
 667   for (int a = X_AXIS; a < NO_AXES; a ++)
 668     {
 669       Axis ax = (Axis)a;
 670       Grob * parent = me->get_parent (ax);
 671
 672       if (!parent)
 673         continue;
 674
 675       if (parent->get_system () != me->get_system () && me->get_system ())
 676         {
 677           Grob * newparent = parent->find_broken_piece (me->get_system ());
 678           me->set_parent (newparent, ax);
 679         }
 680
 681       if (Item * i  = dynamic_cast<Item*> (me))
 682         {
 683           Item *parenti = dynamic_cast<Item*> (parent);
 684
 685           if (parenti && i)
 686             {
 687               Direction  my_dir = i->break_status_dir () ;
 688               if (my_dir!= parenti->break_status_dir ())
 689                 {
 690                   Item *newparent =  parenti->find_prebroken_piece (my_dir);
 691                   me->set_parent (newparent, ax);
 692                 }
 693             }
 694         }
 695     }
 696   return smob;
 697 }
 698
 699 void
 700 Grob::warning (String s)const
 701 {
 702   SCM cause = self_scm();
 703   while (Grob * g = unsmob_grob (cause))
 704     {
 705       cause = g->get_grob_property ("cause");
 706     }
 707
 708   if (Music *m = unsmob_music (cause))
 709     {
 710       m->origin()->warning (s);
 711     }
 712   else
 713     ::warning (s);
 714 }
 715
 716 void
 717 Grob::programming_error (String s)const
 718 {
 719   s = "Programming error: "  + s;
 720   warning (s);
 721 }
 722
 723
 724 /****************************************************
 725   SMOB funcs
 726  ****************************************************/
 727
 728
 729
 730 IMPLEMENT_SMOBS (Grob);
 731 IMPLEMENT_DEFAULT_EQUAL_P (Grob);
 732
 733 SCM
 734 Grob::mark_smob (SCM ses)
 735 {
 736   Grob * s = (Grob*) SCM_CELL_WORD_1 (ses);
 737   scm_gc_mark (s->immutable_property_alist_);
 738
 739   for (int a =0 ; a < 2; a++)
 740     {
 741       scm_gc_mark (s->dim_cache_[a].offset_callbacks_);
 742       scm_gc_mark (s->dim_cache_[a].dimension_);
 743
 744       /*
 745         don't mark the parents. The pointers in the mutable property
 746         list form two tree like structures (one for X relations, one
 747         for Y relations). Marking these can be done in limited stack
 748         space.  If we add the parents, we will jump between X and Y in
 749         an erratic manner, leading to much more recursion depth (and
 750         core dumps if we link to pthreads.)
 751        */
 752     }
 753
 754   if (s->original_)
 755     scm_gc_mark (s->original_->self_scm ());
 756
 757   s->do_derived_mark ();
 758   return s->mutable_property_alist_;
 759 }
 760
 761 int
 762 Grob::print_smob (SCM s, SCM port, scm_print_state *)
 763 {
 764   Grob *sc = (Grob *) ly_cdr (s);
 765
 766   scm_puts ("#<Grob ", port);
 767   scm_puts ((char *)sc->name ().to_str0 (), port);
 768
 769   /*
 770     don't try to print properties, that is too much hassle.
 771    */
 772   scm_puts (" >", port);
 773   return 1;
 774 }
 775
 776 SCM
 777 Grob::do_derived_mark () const
 778 {
 779   return SCM_EOL;
 780 }
 781
 782
 783
 784 void
 785 Grob::discretionary_processing ()
 786 {
 787 }
 788
 789 bool
 790 Grob::internal_has_interface (SCM k)
 791 {
 792   SCM ifs = get_grob_property ("interfaces");
 793
 794   return scm_memq (k, ifs) != SCM_BOOL_F;
 795 }
 796
 797
 798 /** Return Array of Grobs in SCM list L */
 799 Link_array<Grob>
 800 ly_scm2grobs (SCM l)
 801 {
 802   Link_array<Grob> arr;
 803
 804   for (SCM s = l; gh_pair_p (s); s = gh_cdr (s))
 805     {
 806       SCM e = gh_car (s);
 807       arr.push (unsmob_grob (e));
 808     }
 809
 810   arr.reverse ();
 811   return arr;
 812 }
 813
 814 /** Return SCM list of Grob array A */
 815 SCM
 816 ly_grobs2scm (Link_array<Grob> a)
 817 {
 818   SCM s = SCM_EOL;
 819   for (int i = a.size (); i; i--)
 820     s = gh_cons (a[i-1]->self_scm (), s);
 821
 822   return s;
 823 }
 824
 825
 826 IMPLEMENT_TYPE_P (Grob, "ly:grob?");
 827
 828 ADD_INTERFACE (Grob, "grob-interface",
 829   "In music notation, lots of symbols are related in some way.  You can\n"
 830 "think of music notation as a graph where nodes are formed by the\n"
 831 "symbols, and the arcs by their relations. A grob is a node in that\n"
 832 "graph.  The directed edges in the graph are formed by references to\n"
 833 "other grobs (i.e. pointers).  This big graph of grobs specifies the\n"
 834 "notation problem. The solution of this problem is a description of the\n"
 835 "printout in closed form, i.e. a list of values.  These values are\n"
 836 "Molecules.\n"
 837 "\n"
 838 "All grobs have an X and Y-position on the page.  These X and Y positions\n"
 839 "are stored in a relative format, so they can easily be combined by\n"
 840 "stacking them, hanging one grob to the side of another, and coupling\n"
 841 "them into a grouping-grob.\n"
 842 "\n"
 843 "Each grob has a reference point (a.k.a.  parent): the position of a grob\n"
 844 "is stored relative to that reference point. For example the X-reference\n"
 845 "point of a staccato dot usually is the note head that it applies\n"
 846 "to. When the note head is moved, the staccato dot moves along\n"
 847 "automatically.\n"
 848 "\n"
 849 "A grob is often associated with a symbol, but some grobs do not print\n"
 850 "any symbols. They take care of grouping objects. For example, there is a\n"
 851 "separate grob that stacks staves vertically. The @ref{NoteCollision}\n"
 852 "is also an abstract grob: it only moves around chords, but doesn't print\n"
 853 "anything.\n"
 854 ,
 855   "X-offset-callbacks Y-offset-callbacks X-extent-callback molecule cause "
 856 "Y-extent-callback molecule-callback extra-offset spacing-procedure "
 857 "staff-symbol interfaces dependencies X-extent Y-extent extra-X-extent "
 858 "causes meta layer before-line-breaking-callback "
 859 "after-line-breaking-callback extra-Y-extent minimum-X-extent "
 860 "minimum-Y-extent transparent");
 861
 862