defineBarLine confusion

[David Zelinsky]

I'm trying to understand how to use defineBarLine, based on the
documentation in Notation Reference 1.2.5, and bar-line.scm.  The
meaning of the "bartype" argument seems to not be exactly explained
anywhere, but from what is said (mostly in bar-line.scm), and a lot of
experimentation, I deduce that all the characters before a possible "-"
are taken to be names of existing barline glyph elements, and the new
barline glyph is the concatenation of those.

Moreover, from the documentation, the second argument is a list of 3
things that define the behavior at a line break or for spanning multiple
staves.  So I expected these to have no effect when the barline is
occuring in the middle of a single staff.

However, I'm seeing some different behavior:

\version "2.24.0"
\relative c'' {
  \defineBarLine ":;|!-a" #'(#t #t #t)
  \defineBarLine ":;|!-b" #'(#t #t #f)
  \defineBarLine ":;|!-c" #'(#t #t "||")
  a1 \bar ":;|!-a"
  b1 \bar ":;|!-b"
  c1 \bar ":;|!-c"
  d1
}

Since this is a single staff, I expected all these to appear the same.
But version "b" only uses the first character of the bartype argument.
I don't see this documented anywhere, and can't imagine a use-case.

Is it a bug?


-David