Re: problem with extending 'magnetic snapping lyrics' engraver

[Jean Abou Samra]

Le 06/04/2022 à 09:49, Werner LEMBERG a écrit :
> I'm trying to generalize the 'magnetic snapping lyrics' engraver (the
> most recent version posted as
> https://lists.gnu.org/archive/html/lilypond-user/2019-05/msg00389.html)
> by providing a new property `hyphen-formatter`, to be used instead of
> the hard-coded `ly:lyric-hyphen::print`.  Attached you can see the
> final file together with a diff to the original version (ignoring
> whitespace), and an example.  Unfortunately, it doesn't work, and I
> can't find the problem: It aborts with
>
> ```
> ERROR: Wrong type to apply: ()
> ```
>
> Please advise.


It's uncomfortable to have grob properties of procedure type,
since they are automatically resolved as callbacks. You set
LyricWord.hyphen-formatter to ly:lyric-hyphen::print. Then,
when you do

  (ly:grob-property grob 'hyphen-formatter)

this not only looks up ly:lyric-hyphen::print in the property,
but executes it on the LyricWord and returns the result. Since
ly:lyric-hyphen::print is written to work on a LyricHyphen and
not a LyricWord, it gives up and returns '(). Then you try to
apply the "formatter" '() to the hyphen, which goes wrong. You
could use ly:grob-property-data, which skips callbacks, but how
about just changing

   (let* ((hyphen-sten (ly:lyric-hyphen::print hyphen))

to

   (let* ((hyphen-sten (ly:grob-property hyphen 'stencil))


? Then you can do \override LyricHyphen.stencil = #what-you-want to
get the result.


Jean