Re: programming error for thickness/control-points of Slur

[Jean Abou Samra]

Le 27/05/2022 à 11:22, Thomas Morley a écrit :
> Hi,
>
> lsr-snippet "Variable bow thickness depending on length"
> https://lsr.di.unimi.it/LSR/Item?u=1&id=1028 looks at 'control-points
> to calculate a modified thickness.
>
> For recent lily-versions this throws
> programming error: cyclic dependency: calculation-in-progress
> encountered for Slur.thickness
> as soon as 'control-points are called in a thickness-override.
>
> Stripped down example:
>
> \version "2.23.9"
>
> {
>    \override Slur.thickness =
>    #(lambda (grob)
>      ;; all of below trigger the programming error
>      (ly:slur::calc-control-points grob)
>      ;(ly:grob-property grob 'control-points)
>      ;((assoc-get 'control-points (ly:grob-basic-properties grob)) grob)
>      2)
>
>    b1( b')
> }
>
> I think I can make it work with an override for 'after-line-breaking
> (calling 'control-points, set 'thickness to the result of calculations
> based on the 'control-points and finally redo setting
> 'control-points).
>
> Is there a better way?


Yes, quite logical since the control points depend on the
thickness. No, short of refactoring the C++ code, I don't
see a better way than what you described.

Best,
Jean