Re: grob-object information

[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.

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.

Cheers,
MS