problem with LSR 643

[Werner LEMBERG]

The LSR 643 snippet gives a very nice function to append punctuation
to an extender line.  However, using \extendComma to get

  ______________ ,


the depth of the comma glyph is cut while using lilypond-book if it
happens that this particular extender line is the lower edge of the
image, and if there are no other letters with descenders.  I suspect
that for lyrics extenders, skyline computation is not taken into
account, and this must be added somehow.  Any idea how to fix that?


    Werner


PS: How can I find out who has written that snippet?

\documentclass{article}

\begin{document}

foo

\begin[quote]{lilypond}
#(define (extend text . padding)
   (let ((extender (make-music 'ExtenderEvent))
         ;; optional padding
         (padding (if (pair? padding)
                      (car padding)
                      0)))

     (set! (ly:music-property extender 'tweaks)
           (acons 'stencil (lambda (grob)
                             (ly:stencil-combine-at-edge
                              (ly:lyric-extender::print grob)
                              X RIGHT
                              (grob-interpret-markup grob text)
                              padding))
                  (ly:music-property extender 'tweaks)))

     extender))

%Define custom extenders, first with extra padding
extendComma = #(extend "," 0.2)

\score {  
  <<
    \new Staff \new Voice = melody \relative c' {
      c4( d e f)
    }
    \new Lyrics \lyricsto melody {
      AAA \extendComma
    }
  >>
  \layout {
    \context {
      \Lyrics
      \consists "Tweak_engraver"
    }
  }
}
\end{lilypond}

bar

\end{document}