Re: bis

[Andrew Bernard]

Hi Erik,

This is a use for a text spanner with centred text that I had been
asking about on the list for some time, Eventually I wrote a function
to do it with the kind help of Thomas Morley also. Very useful - I
always said so!

Have a look at this - it may do what you require.

Andrew

== snip

\version "2.19.37"

\include "/home/andro/lib/lilypond/scheme.ily"

% Annotation bracket with centred text.
% Andrew Bernard and Thomas Morley

TextSpannerCentredText =
#(define-music-function (text extra-length) (string? pair?)
   "Use TextSpanner semantics to create spanner brackets with centred text"
   #{
     \once \override TextSpanner.after-line-breaking =
     #(lambda (grob)
        (let* (
                ;; get stencil of grob
                (stil (ly:grob-property grob 'stencil))
                ;; get spanner length
                (spanner-len (interval-length (ly:stencil-extent stil X)))
                ;; make stencil from text arg
                (text-stil (grob-interpret-markup grob
                             (markup #:sans #:upright text)))
                ;; get text length
                (text-len (interval-length (ly:stencil-extent text-stil X))))
          ;; if text length exceeds the spanner length we cannot really proceed.
          ;; do nothing - make an ordinary text spanner and warn.
          (if (>= text-len spanner-len)
              (begin
               (ly:warning "text length longer than spanner")
               #f
               )
              (let* (
                      ;; get direction, up or down
                      (dir (ly:grob-property grob 'direction))
                      ;; some padding
                      (padding 1)
                      ;; line thickness
                      (thickness 0.25)
                      ;; extra length on left, negative values shorten
                      (left-ext (car extra-length))
                      ;; extra length on right, negative values shorten
                      (right-ext (cdr extra-length))
                      ;; calculate length considering text length
                      (path-part-len (/ (- spanner-len text-len) 2))
                      ;; make left bracket stencil
                      (path-left-part-stil
                       (make-path-stencil
                        `(
                           moveto ,(- left-ext) ,(* -1 dir)
                           lineto ,(- left-ext) 0
                           lineto ,path-part-len 0
                           )
                        thickness 1 1 #f))
                      ;; make right bracket stencil
                      (path-right-part-stil
                       (make-path-stencil
                        `(
                           moveto ,(+ path-part-len right-ext) ,(* -1 dir)
                           lineto ,(+ path-part-len right-ext) 0
                           lineto 0 0
                           )
                        thickness 1 1 #f))
                      ;; make complete stencil combining left and right parts
                      ;; and text
                      (full-stil
                       (stack-stencils X RIGHT padding
                         (list
                          path-left-part-stil
                          (centered-stencil text-stil)
                          path-right-part-stil)))
                      )
                ;; set grob stencil to fully constructed stencil
                (ly:grob-set-property! grob 'stencil full-stil)
                ))))
   #}
   )


{
  c' d' ees' fis'
  \once \override TextSpanner.direction = #DOWN
  \TextSpannerCentredText "6\"" #'(0 . 0)
  g' \startTextSpan
  a' bes' c'' \stopTextSpan
  \TextSpannerCentredText "x3" #'(2 . 1)
  bes'\startTextSpan a' g' c'\stopTextSpan
  \TextSpannerCentredText "x3" #'(2 . -6)
  c''1\startTextSpan
  c''1\stopTextSpan
}


== snip