Re: Bars

[Han-Wen Nienhuys]

address@hidden writes:
> Though I did not investigate it in that detail, it seems the main
> problem is that the existing code in span_bar.cc depends on the
> existence of a bar_engraver in the staff context.

that's no problem, you can simply make the bars disappear by setting
#'transparent to ##t in the BarLine grob.  (you also suggest  this
yourself)
 
> when creating a span_bar.  Another solution would be, as I already
> proposed, to introduce a visibility property for the bar engraver.
> Then, one would set the visibility rather than removing or adding a
> bar_engraver to whatever context.

See above.

> By the way, I would like to propose renaming bar* and span_bar* into
> staff_bar* and interstaff_bar*.

Do you mean files or variable names?

> +
> +  // first walk: compute axis_group parent via common_refpoint () on all bars
> +  Grob *refpoint = 0;

init this with me, the translation of the me grob should be
filtered. this also removes the need for checking below.

> +  /* assert: refpoint is an axis-group object */

Incorrect. The refpoint may be any grob.

> +  // compute extent of axis_group
> +  Real last_staff_bar_length;
> +  Real *interstaff_bar_length = new Real[staff_bar_count];

I prefer that an Array<Real> be used.

> +  for (SCM elts = first_elt;
> +       elts != SCM_EOL;
> +       elts = gh_cdr (elts))
> +  {
> +    SCM smobbed_staff_bar = gh_car (elts);
> +    SCM smobbed_staff_bar_molecule =
> +      Bar::brew_molecule (smobbed_staff_bar);
> +    Grob *staff_bar = unsmob_grob (smobbed_staff_bar);
> +    interstaff_bar_yoffs[staff_bar_count] =
> +      staff_bar->relative_coordinate (axis_group, (Axis)Y_AXIS);

this is overly complicated. Use Grob::extent (axis_group, Y_AXIS) to
find out the size of the bar lines.


> +     interstaff_bar_molecule[staff_bar_count] =
> +       *unsmob_molecule (smobbed_interstaff_bar_molecule);

don't do this -- you're storing a molecule on the heap, hiding it from
GUILE GC.  This code is bound to crash in ugly ways.

I think you're code is on the lengthy side, and the above points must
be addressed before I consider putting the patch in. The code
shouldn't have to be so difficult. Roughly, it should be like:

  Grob * last_bar = 0;
  for (SCM s = elements ; gh_pair (s) ; s =gh_cdr (s))
    {
      Grob *m = unsmob_grob (gh_car (s))


      if (last_bar){
            Interval l; l[LEFT] = last_bar->extent (refp, y_axis)[DOWN]
            l[RIGHT] = m->extent (refp, y_axis)[UP]
            span_bar_mol.add (make_bar_molecule (l));
      }
      last_bar = m;
    }

  return span_bar_mol;

-- 

Han-Wen Nienhuys   |   address@hidden    | http://www.cs.uu.nl/~hanwen/