%\version "2.14.2"
\version "2.12.3"

#(define-public PI (* 4 (atan 1)))

#(define (radians->degree radians)
  (/ (* radians 180) PI))

#(define ((gliss-plus-text padding text) grob)
  (let* ((text-stencil (grob-interpret-markup grob text))
         (spanner-stencil (ly:line-spanner::print grob))
         (left-bound-info (ly:grob-property grob 'left-bound-info))
         (y-left (cdar left-bound-info))
         (right-bound-info (ly:grob-property grob 'right-bound-info))
         (y-right (cdar right-bound-info))
         (slant (if (> y-right y-left) 1 -1)) 
         (spanner-stencil-x-length (interval-length (ly:stencil-extent spanner-stencil X)))
         (spanner-stencil-y-length (interval-length (ly:stencil-extent spanner-stencil Y)))
         (alpha (radians->degree (atan (/ spanner-stencil-y-length spanner-stencil-x-length))))
         (spanner-center-X (interval-center (ly:stencil-extent spanner-stencil X)))
         (label-center-X (interval-center (ly:stencil-extent text-stencil X))))
  
  (ly:stencil-combine-at-edge 
    spanner-stencil 
    Y UP
    (ly:stencil-translate 
      (ly:stencil-rotate text-stencil (* slant alpha) 0 0)
      (cons (- spanner-center-X label-center-X) 0)) 
    ;;(* -0.5 spanner-stencil-y-length)
    padding
    )))
                   
glissandoTextOn = \override Glissando #'stencil = #(gliss-plus-text -9 (markup #:italic #:tiny "gliss"))
glissandoTextOff = \revert Glissando #'stencil

noteHeadsOff = {
        \override NoteHead #'transparent = ##t
        \override NoteHead #'no-ledgers = ##t
}
noteHeadsOn = {
        \revert NoteHead #'transparent
        \revert NoteHead #'no-ledgers 
}

%---- test

\paper { ragged-right = ##f }

\new PianoStaff <<
 \new Staff = "right" {
   \clef treble

   \glissandoTextOn
   e'''8\glissando s s4
   \change Staff = "left"
   \noteHeadsOff
   a,,8\glissando s s4 |
   \change Staff = "right" 
   b''8
 }
 \new Staff = "left" {
   \clef bass
   s1 s8
 }
>>