Re: changing grob properties?

[Marc Hohl]

Neil Puttock schrieb:
> 2009/5/15 Marc Hohl <address@hidden>:
>
>   
> > Upto now, I have achieved to make tablature fret numbers invisible which are
> > tied to another note.
> > But I don't know how to add parentheses to the numbers that are tied but
> > show up after a line break
> > (for example the first note in measure 5, see attachment).
> >
> > I tried something like
> >
> > (set! (ly:music-property note 'elements)
> >                (cons (make-music 'NoteEvent 'parenthesize #t)
> >                      (ly:music-property note 'elements)))
> >
> > but I realized that a grob is not a music expression as the variable called
> > "note" in the code fragment above.
> >     
>
> Indeed, once the grob's been created it's too late to be setting music
> properties.
>
>   
> > Then I came up with the vague idea to combine the TabNoteHead-Stencil with
> > the
> > stencil for the parentheses, but this was beyond my knowledge, it didn't
> > work.
> >     
>
> It won't work, since the stencil callback for parentheses has some
> rather specific requirements which are set in the
> Parenthesis_engraver.
>
> You could use markup to place the parentheses around the TabNoteHead,
> but unless I'm mistaken, that's not possible inside a callback for
> 'after-line-breaking, since it's called after stencils have been
> generated.
>   
So can I use it as a callback for 'stencil? (see below)
>   
> > \version "2.12.2"
> >
> > #(define (tie::handle-tab-tie grob)
> >  (let* ((original (ly:grob-original grob))
> >         (tied-tabnotehead (ly:spanner-bound original RIGHT))
> >     
>
> Should be (ly:spanner-bound grob RIGHT).
>
> The unbroken grob is only used to obtain the list of broken spanners,
> if there are any (remember that this callback will be called for every
> tie, including those which aren't split).
>
>   
> >         (siblings (if (ly:grob? original)
> >                     (ly:spanner-broken-into original) '() )))
> >
> >    (if (and (>= (length siblings) 2)
> >            (eq? (car (last-pair siblings)) grob))
> >       ;; tie is split
> >       ;; just a dummy function here, parentheses should be inserted
> >       (begin (ly:grob-set-property! tied-tabnotehead 'transparent #f)
> >     
>
> It would be easier to see whether this is actually working on the
> correct grob if you changed the override to 'color.
>   
Ok, I inserted

(ly:grob-set-property! tied-tabnotehead 'color (rgb-color 1 0 0))

and the first tab number (the one in measure 5) is now red, all other 
numbers
of tied notes disappear, as it should be.
>   
> >              (newline)
> >              (display "Tie is split.")
> >              (newline))
> >       ;; tie is not split -> make fret number invisible
> >       (ly:grob-set-property! tied-tabnotehead 'transparent #t)
> >       );; end if
> >       ))
> >
> > test = \relative c {
> >       f2 ~ f4 \parenthesize e
> >       g8 g ~ g g ~ g g~ g g ~
> >       g1
> >       c1 ~ \break c2 ~ c
> >       < c\3 e\2 g\1 >4 < c\3 e\2 g\1 > ~ < c\3 e\2 g\1 > < c\3 e\2 g\1 >
> >       \bar "|."
> >       }
> >
> > \score {
> >   << \new Staff { \clef "G_8" \test }
> >      \new TabStaff { \clef "tab"
> >                      \override Tie  #'stencil = #tie::handle-tab-tie
> >     
>
> Should be \override Tie #'after-line-breaking = #tie::handle-tab-tie
>
> There's no stencil returned by the function, which is why you're
> getting loads of programming errors and invisible ties.
>   
Hm, I didn't get any errors, and invisible ties are exactly the feature 
I need.
At first, I used

\override Tie #'after-line-breaking = #tie::handle-tab-tie

but I didn't quite understand the term "after-line-breaking", since 
tie::handle-tab-tie is
called on _every_ tie. So I changed the call to 

\override Tie  #'stencil = #tie::handle-tab-tie

and found out that it works, too, and has the advantage not to write 

\override Tie  #'stencil = ##f

explicitly. But if this is a crude style, I won't apply it. On the other hand, 
when
this offers a possibility to change the TabNoteHead stencil on the fly, it 
could be used.

Can I switch to another tablature format, according to

\set tablatureFormat = #parenthesized-tab-format / which is not defined yet?

but this has the drawback that notes inside a chord would be parenthesized 
individually,
but - as David Stocker mentioned - chords should be included in _one_ pair of 
parentheses,
as this is the standard for this kind of notation.

Is the a possibility to handle these situations with a different approach? For
the "normal" case (i.e. tied notes within the same staff line) everything works
properly with tie::handle-tab-tie, so if there is a possibility to filter all 
notes
that are tied _and_ placed immediately after a line break and put parenthesizes
around them, it would be fine.

Marc



> Regards,
> Neil
>
>