music-function for ending TextSpanners sometimes fail for skip-events

[Thomas Morley]

Hi,

for some reason I wanted a music-function which should end a
TextSpanner automagically at the next event which starts a new
TextSpanner or the last possible event at all.

Although it needs further testing I already found a glitch I really
can't explain or cope with: Sometimes, when the TextSpanner is
attached to skip-events, ending them gets confused. It sometimes can
be cured, if the skips are devided, i.e. s2 becomes s4 s4.
So why????
And how to fix the function, which is inspired by our endSpanners-function.

Here the code:

\version "2.19.82"

endTextSpanners =
#(define-music-function (music) (ly:music?)
   (_i "Terminate a TextSpanner at the last rhythmic-event or at the next
rhythmic-event which starts a new TextSpanner, without the need to use
@code{\\stopTextSpan}.")
  (let ((counter 0)
        (last-rhythmic-ev #f)
        (end-span-ev-chrd
          (make-event-chord
            (list (make-music
                    'TextSpanEvent
                    'span-direction
                    1)))))
    (map-some-music
      (lambda (m)
        (and (or (music-is-of-type? m 'rhythmic-event)
                 (music-is-of-type? m 'skip-event))
             (let* ((mus (ly:music-deep-copy m)))
               (set! last-rhythmic-ev mus)
               (cond ((and (zero? counter)
                           (pair? (extract-typed-music mus 'text-span-event)))
                        (begin
                          (set! counter (1+ counter))
                          mus))
                     ((pair? (extract-typed-music mus 'text-span-event))
                      (make-sequential-music
                        (list
                          end-span-ev-chrd
                          mus)))
                     (else mus)))))
      music)
    (map-some-music
      (lambda (mc)
        (and (equal? mc last-rhythmic-ev)
             (make-sequential-music
               (list
                 end-span-ev-chrd
                 mc))))
       music)
     (set! counter 0)
     (set! last-rhythmic-ev #f)
     music))

%% Only for better viewing
\layout {
  \override TextSpanner.style = #'solid
  \override TextSpanner.bound-details.left.text = "X"
}

%% This returns:
%% warning: cannot find start of text spanner
\endTextSpanners
  {
     s2 -\startTextSpan
     s2
     s2
  }

%% This one works !!
\endTextSpanners
  {
     s2 -\startTextSpan
     s4 s
     s2
  }

%% This one as well
\endTextSpanners
  {
     c'2 -\startTextSpan
     d'2
     e'2
  }


Thanks,
  Harm