Re: Determining location of the staff lines

[Carl Sorensen]

On 2/14/10 9:38 AM, "Eric Knapp" <address@hidden> wrote:

> On Wed, Feb 10, 2010 at 8:58 PM, Carl Sorensen <address@hidden> wrote:
> 
>> You're making great sense. =A0This is *really* easy, once you understand =
> how
>> LilyPond engravers work.
>> 
> 
> I think I'm still missing a few pieces.
> 
>> As an example, look at lily/fretboard-engraver.cc.
> 
> My C++ is really rusty and while I see what going on, I can't see how
> to do this in a Scheme engraver.

I think it's not yet possible to do this in a Scheme engraver.

Han-Wen indicated that it could be done here:

http://lists.gnu.org/archive/html/lilypond-devel/2010-01/msg00594.html

But I don't think it's been implemented yet.  Perhaps Han-Wen will do so,
now that we've identified a need.

> OK, the next questions are this.
> 
> When you say, "will listen", do you mean that I'll have code in the
> "(cons 'listeners..." section of the Scheme engraver?

Exactly.  You'll have a listener for note-events and for string-number
events.

> 
> How do I create the vectors in Scheme so that they are persistent?
> Everything I've tried has resulted in only having the last item in the
> vector there once I'm done.

We need to have the capability to store private data in Scheme engravers.
Hopefully we can get that implemented.

> 
> How do I get the vectors to the spot where I'm making the grob?
> 

Once you have the private data stored, it will be available to all of the
Scheme functions in the engraver.

> What section of the Scheme engraver will I create the grobs? What
> grobs do I make?

The grob will be created in the process-music function, which occurs after
all of the notes at the current moment.

You should create StaffTabStringIndicator grobs  (you'll need to create a
new grob type for that -- see scm/define-grobs.scm).

HTH,

Carl