Re: grob-object information

[Marc Hohl]

Am 11.09.2012 20:48, schrieb address@hidden:
> On 11 sept. 2012, at 17:48, Marc Hohl <address@hidden> wrote:
>
> > Hello list,
> >
> > for my work on the volta bracket inclusion for the new bar line interface,
> > I need to know how the bars are ordered in (ly:grob-object grob 'bars).
> >
> > Please see the attached file.
> >
> > For the \musOne, I get a grob array with eight BarLine grobs
> > (two for each staff) for the first volta bracket (and one for
> > the second volta bracket, of course):
> >
> > |------volta------|
> > <BarLine> <BarLine>
> > <BarLine> <BarLine>
> > <BarLine> <BarLine>
> > <BarLine> <BarLine>
> >
> >
> > For \musTwo, I get a grob array consisting of eight BarLine grobs
> > (because the bracket spans eight bars in a single line) and a second
> > one for the second volta bracket.
> >
> > |-------------------------------------volta-----------------------------------|
> > <BarLine> <BarLine> <BarLine> <BarLine> <BarLine> <BarLine> <BarLine> <BarLine>
> >
> >
> > Is there any chance to get to know how the grobs are arranged?
> > Or more formally: how can I get the 2D structure back from a 1D vector?
> >
> > Thanks in advance,
> >
> > Marc
> >
> > <shortvoltatest.ly>_______________________________________________
> > lilypond-devel mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/lilypond-devel
> You can use Grob::get_vertical_axis_group_index (you'd have to write a Scheme 
> binding).
What value does that function return? A quick glance at its definition
in lily/grob.cc does not fully reveal its return value, but as this is 
an integer,
I have a 1D -> 1D function, but I need 2D.
>    Or sort the list it based on ly:grob::vertical-less? (that binding is 
> already written).
IIUC, that will sort the BarLine grobs, but I think that they *are* 
already sorted
in the grob array, like this:

|---------volta---------|
<BarLine 1a> <BarLine 2a>
<BarLine 1b> <BarLine 2b>
<BarLine 1c> <BarLine 2c>
<BarLine 1d> <BarLine 2d>

is returned as <1a> <1b> <1c> <1d> <2a> <2b> <2c> <2d> (I assume),
but if I only have the grob array, I do not have the length and
width of the underlying 2D structure.

Regards,

Marc