Re: grob-object information

[address@hidden]

On 11 sept. 2012, at 22:29, Marc Hohl <address@hidden> wrote:

>>> 
>> 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.

What about pieces with different simultaneous time signatures?  They'd have 
different numbers of bars for a given section.

>> 
>> 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?
> 

The column number of a grob's left and right bound. Columns are linearly 
ordered from the beginning of a score to the end, so you can use it to know 
when a new staff is beginning in your array.  For bar lines, the grob only 
spans one column so the left and right values of the returned will be the same 
- you can use either one.

In C++, if I had a vector <Grob *> foo that I wanted to sort into vector 
<vector <Grob *> > bar, if I understand you correctly, I'd do:


int current_column = INT_MAX;

for (vsize i = 0; i < foo.size (); i++)
 {
   int column = foo[i]->spanned_rank_interval ()[LEFT];
   if (column <= current_column)
     bar.push_back (vector<Grob *> ());
   bar.back ().push_back (foo[i]);
   current_column = column;
 }

The same thing is doable in Scheme - I just write pseudo-code faster in C++.

Cheers,
MS