Re: Background Colour

[Jean Abou Samra]

Le 18/05/2021 à 17:55, Lukas-Fabian Moser a écrit :
> Hi Jean,
>
> > How about a separate grob with engraver? Try the attached.
>
> This should be included in the documentation as a textbook example for 
> a not-quite-trivial, but reasonably straightforward example of a both 
> a custom engraver and a custom grob.

Well, the documentation doesn't have any material about Scheme engravers 
yet. For now, I'll add it to the guide I wrote up.

> Thanks very much for this!

You're welcome.

> And wouldn't it be worth to add the convenience macro define-grob! to 
> LilyPond's stock scheme library?

In this state, it is a dirty hack that will cause problems in particular 
cases (like defeating per-session semantics). I'd rather recode this 
part of the internals so that grobs can be defined with a nicer 
interface. For some time, I have been musing with the perspective of 
grob definitions in a fashion similar to context definitions, borrowing 
most of the syntax, like:

\layout {
  \grob {
    \NoteHead
    color = "red"
  }
  \grob {
    \name Highlight
    \type Item
    \interface text-interface
    \interface ...
    stencil = #highlight::print
    Y-extent = ##f
    ...
  }
}

I'd be happy if someone led discussions for this and implemented it in 
some form; I might do it at some point, but my contributor stack already 
contains quite a few projects currently.

Best,
Jean