I feel like I needed it ten years ago ;) On Tue 27 Dec 2022, 23:25 Jean Abou Samra, <j...@abou-samra.fr> wrote:
> Le 26/12/2022 à 19:18, Gregory Evans a écrit : > > Hi Jean, > > I apologize for my delayed reply. > > > > I do not think I can use the VoiceFollower grob because I am not using > > staff changes. > > > > You can. A VoiceFollower won't be created automatically without a staff > change, but you can create it yourself in your Scheme engraver. > > > > > Attached is a pdf of what I am trying to do. It works successfully if > > I input the y-position by hand but ideally it would be calculated > > automatically. You see, they are completely unrelated voices. Also see > > this image of hocket indications in Ben Johnston's 3rd string quartet > > which I think would not be done with VoiceFollower: > > > > I have also included the lilypond file for my interruptive polyphony > > example if that is of any use to you even though it is quite large. > > While it's true that certain aspects of the process could be > > simplified (such as removing the use of 'meta as you suggest), there > > is little reason to revise it if the callback cannot be delayed until > > after the skyline calculation. Is there no way to simply trigger > > callback at a later time? > > > "Trigger callback at a later time" sounds like you are thinking > too much in imperative programming terms of "get parameters, set > stencil to what I want". That's not how most of LilyPond's backend > works, with the exception of after-line-breaking and a few other > properties. Instead, you build callbacks that compute the initial > values of properties (instead of getting their values and changing > them). See also this recent discussion: > > https://lists.gnu.org/archive/html/lilypond-user/2022-12/msg00001.html > > Thus, the question is not "how to trigger this callback at a later > time, so it knows everything" but "how to ensure that nothing this > callback depends on also depends on it, so there are no cyclic > dependencies". The answer is the cross-staff property, as I explained > previously, on a grob that supports it like VoiceFollower (but > not NoteHead). > > See the attached file for an implementation of your graphical > notation. I basically started from scratch because it was simpler, > so its exact behavior might deviate from what you wanted (there > were some oddities in your original code and I don't know which > of them were intentional), but it outputs the same thing on the > excerpt you give, and it should get you going. > > By the way, not sure if you or Piaras is the author of the PostScript > code, but if you are, please read the documentation of \postscript > <https://lilypond.org/doc/v2.24/Documentation/notation/graphic> > on why you should only use embedded PostScript code if you absolutely > need it, which is not the case here (make-path-stencil does the job). > > Best, > Jean > >
