Re: grob-object information

[Marc Hohl]

Am 11.09.2012 21:08, schrieb address@hidden:
> On 11 sept. 2012, at 22:02, Marc Hohl <address@hidden> wrote:
>
> > 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),
> Are you certain that every vertical axis group will always contain the same 
> number of bar lines?  If not, it's possible that the matrix you're talking 
> about may not have complete rows, in which case it's difficult to know how to 
> break it.
I am not 100% sure – there could be corner cases where a staff line 
stops before the
volta bracket is closed, but this could lead to an error when compiling 
the .ly file.
> One way to check it is to look at the left or right of the spanned_rank_interval of the 
> grobs (the values will be the same as you're dealing with items which only ever 
> "span" one column).  Once it goes backwards, you know that you've skipped to 
> the next row.
What kind of values does spanned_rank_interval return?

Regards,

Marc