Re: change barline type with time signature change

[Jan-Peter Voigt]

Hi Kieren, hi David,

I darkly remember a scheme engraver, that did something, whenever a 
time-sig-schange happens. IIRC it is based on snippet from you David.
One might reduce it to the following:

--snip--
% engraver
#(define-public timesig-barline
   (lambda (context)
     (let ((last-fraction #f)) ; remember last time-sig-fraction in 
this context
       `(
         (process-music
          . ,(lambda (trans)
               (let (; get parental Timing context
                     (timingctx (ly:context-find context 'Timing))
                     ; get current time-sig-fraction
                     (frac (ly:context-property context 
'timeSignatureFraction)))
                 ; compare the current with the last fraction
                 (if (and (not (equal? last-fraction frac))
                          (pair? frac))
                     ; if they are not equal, do something ...
                     (begin
                      ; action for this engraver: set barline
                      (ly:context-set-property! timingctx 'whichBar "||")
                      ; set last-fraction
                      (set! last-fraction frac)
                      )))))
         )
       )))

% example
\new Staff \with {
  \consists #timesig-barline
} \relative c'' {
  bes a c b | bes a c b | \time 3/4 cis c b | cis c b |
}
--snip--

You might create a scheme function to produce the engraver you need:

--snip--
% engraver builder
timeSigChangeEngraver =
#(define-scheme-function (parser location proc)(procedure?)
   (lambda (context)
     (let ((last-fraction #f)) ; remember last time-sig-fraction in 
this context
       `(
         (process-music
          . ,(lambda (trans)
               (let (; get current time-sig-fraction
                     (frac (ly:context-property context 
'timeSignatureFraction)))
                 ; compare the current with the last fraction
                 (if (and (not (equal? last-fraction frac))
                          (pair? frac))
                     ; if they are not equal, do something ...
                     (begin
                      ; action for this engraver
                      (proc context trans)
                      ; set last-fraction
                      (set! last-fraction frac)
                      )))))
         )
       )))

% example
\new Staff \with {
  \consists \timeSigChangeEngraver #(lambda (context trans)
                                      (let ((timingctx (ly:context-find 
context 'Timing)))
                                        (ly:context-set-property! 
timingctx 'whichBar "||")
                                        ))
} \relative c'' {
  bes a c b | bes a c b | \time 3/4 cis c b | cis c b |
}
--snip--

HTH

Best, Jan-Peter


Am 22.01.2013 16:18, schrieb David Nalesnik:
> Hi Kieren,
>
> On Tue, Jan 22, 2013 at 8:56 AM, Kieren MacMillan 
> <address@hidden <mailto:address@hidden>> 
> wrote:
>
>     Hello all!
>
>     I'm working in Lilypond v2.17.9, and the conductor of my chamber
>     opera (being performed in April) wants the following stylesheet
>     override: the default barline type should be dashed or dotted, but
>     the barline should be solid (i.e., standard) at every time
>     signature change.
>
>     What's the best way to do this, abstracted of course (because this
>     is the only conductor who has so far requested such a thing).
>
>
> Here's a thread containing a Scheme engraver which might be able to be 
> adapted to the purpose:
> http://www.mail-archive.com/address@hidden/msg72613.html
>
> Unfortunately I won't be able to work on it at the moment...
>
> -David
>
>
> _______________________________________________
> lilypond-user mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/lilypond-user