Re: Improves some parmesan noteheads. (issue 4639065)

[Benkő Pál]

>> > * Use the left-stemmed longa in ligatures.
>
>> exactly what is this last one?
>
> When note_shape is MLP_LONGA and the direction of the stem is UP, then
> the left-stemmed longa is used.

oh, indeed.  I must have messed up my build, now I see it.
unfortunately this is bad.
look at the first row of the mensural-ligatures.ly regtest:
the second LB and the second SS are indistinguishable.

> I know, this should be Mensural_ligature_engraver's job.
> The mensural ligature engraver needs to be rewritten. All the postscript
> stuff should somehow be replaced with good old MetaFont.

I don't mind that (I didn't eve know that the Stencil - Interval
manipulations were PostScript) and I'm willing to take part.

p