Re: Scheme function to print out active Voice context during interpretation?

[John Mandereau]

Hi Trevor!
Le dimanche 14 décembre 2008 à 12:42 -0600, Trevor Bača a écrit :
> Is there a way to print out the name (or other identity) of the
> currently active voice just before any given note or rest in an input
> file?

> Does something like this exist?

I haven't found such a function in Lily sources and docs, try these two
music functions (freely inspired from barNumberCheck definition):

whichContext = #(define-music-function (parser location) ()
                 (make-music 'ApplyContext 
                  'origin location
                  'procedure (
                    lambda (c)
                    (display
                     (string-append
                      "\nCurrent voice is "
                      (ly:context-id c)
                      "\n")))))

locationWhichContext = #(define-music-function (parser location) ()
                 (make-music 'ApplyContext 
                  'origin location
                  'procedure (
                    lambda (c)
                    (display
                     (ly:input-message location
                      "current voice is ~a"
                      (ly:context-id c))))))

It's also possible to make Scheme avatars of these functions, but then
they would need to take the location as an argument.

This should be added to the docs IMHO; should this be added in LSR, the
manual or the (yet to be written) docstring of applyContext?


> [The motivation is that I'm researching the way that LilyPond
> determines which voice music events are assigned to ... from a user's
> perspective based solely on looking at input files. Voice-resolution
> in the example above is of course quite clear; voice-resolution when
> there are multiple anonymous voices, possibly in parallel, has become
> extremely tricky as I've written more and more test files, all of
> which I'll be happy to post if anyone else is interested in that sort
> of thing.]

Please do :-) I guess some of these tests may be added to LSR.

Hope this helps,
John