Re: skylines and custom-code

[Thomas Morley]

Am Do., 8. Apr. 2021 um 16:21 Uhr schrieb Kevin Barry <barrykp@gmail.com>:
>
> Hi Harm,
>
> > Ok, another 5 days passed working allday on the problem, progress: zero.
> > I give up.
> >
> > Some insights:
> > (1)
> > It would have been helpful to understand how Stems fit into a Beam,
> > then I could use this knowledge to probably do similar with glissando
> > and Stems.
> > I was not able to figure it out.
> > (2)
> > Obviously the Stems needs to be positioned after Beam (or Glissando) is 
> > done.
> > An unpure-pure-container looked promising.
> > Though, I was not able to code even the simplest via native scheme.
> > This leads to the conclusion that unpure-pure-containers are not
> > accessible/customizable for users like me.
> > At least unless much more working examples are done in the docs.
>
> I haven't had time to try and understand your issue, but having worked
> on problems with Stems and Beams in the past I think it's an area of the
> code that could be improved, because there is an effective circular
> dependency:
> - Stems check Beams in order to determine their direction/position etc
> - Beams check where the first and last noteheads are - compared to the
>   whole system - to try and figure out on which side they should be on
>   or if the beam should be kneed, etc
> - Checking where noteheads are in relation to the whole system triggers
>   lots of other grob calculations. If any of these calculations check
>   the Beam or the Stem you get a circular dependency (I fixed at least
>   one regression in this area where DynamicText was triggering the
>   circular dependency).
> - If you try to dive into all the consequences of the code that
>   calculates a Stem's direction it is almost impossible to understand.
>   It's a long chain of pure/unpure calls - maybe 50 stack frames of just
>   that stuff (IIRC); completely impenetrable (for me at any rate)
> - In my opinion, the fix is to find a way to figure out notehead
>   positions without calculating everything else, then Beams, then Stems
>
> I doubt that is any help to you, but perhaps someone else will read this
> and know more.
>
> Kevin

Hi Kevin,

thanks for your reply.
You surely mean the position in x-axis direction for the NoteHeads!?

Best,
  Harm