Re: vertical spacing of footnotes

[Werner LEMBERG]

>> However, there is one problem that I don't understand: Why is the
>> space between footnotes 3 and 4 (and 4 and 5) larger than between 1
>> and 2 (and 2 and 3)?
> 
> Well, in footnotes 1 and 2, there is only one strut for the two
> lines.  Try this, [...]

Excellent, thanks again!  Here's my new version – the (baseline)
distance between footnotes is now controlled by the paper variable
`footnote-dist`, while the baseline skip within a footnote is taken
from `text-font-defaults.baseline-skip`.  I've split the strut into
two components, to be inserted before the first line and after the
last line of a footnote.


    Werner

\version "2.24.0"

#(set-default-paper-size "a7landscape")

#(define-markup-command (footnote-height-strut layout props)
   ()
   "Insert a height strut.  The value is derived from the
`footnote-dist` paper variable."
   (let* ((dist (ly:output-def-lookup layout 'footnote-dist))
          (yext (cons 0 (* 0.7 dist))))
     (ly:make-stencil
      (ly:stencil-expr
       (make-transparent-box-stencil '(0 . 0.05) yext))
      empty-interval
      yext)))

#(define-markup-command (footnote-depth-strut layout props)
   ()
   "Insert a depth strut.  The value is derived from the
`footnote-dist` paper variable."
   (let* ((dist (ly:output-def-lookup layout 'footnote-dist))
          (yext (cons (* -0.3 dist) 0)))
     (ly:make-stencil
      (ly:stencil-expr
       (make-transparent-box-stencil '(0 . 0.05) yext))
      empty-interval
      yext)))

#(define-markup-command (footnote-struts layout props elts)
   (markup-list?)
   "Insert a height strut at the beginning of the first line
and a depth strut at the end of the last line of a footnote
`elts` (which is a markup list holding the lines)."
   (let ((stils (interpret-markup-list layout props elts)))
     (if (null? (cdr stils))
         (let ((stil (car stils)))
           (interpret-markup layout props
                             #{ \markup {
                                  \footnote-height-strut
                                  \stencil #stil
                                  \footnote-depth-strut } #}))
         (let* ((first-stil (car stils))
                (first-mkup #{ \markup {
                                 \footnote-height-strut
                                 \stencil #first-stil } #})
                (last-stil (last stils))
                (last-mkup #{ \markup {
                                \stencil #last-stil
                                \footnote-depth-strut } #})
                (rest-stils (cdr stils))
                (rest-stils (drop-right rest-stils 1))
                (rest-mkups
                 (map (lambda (stil)
                        #{ \markup \stencil #stil #})
                      rest-stils)))
           (interpret-markup layout props
                           #{ \markup {
                                \column {
                                  #first-mkup
                                  #rest-mkups
                                  #last-mkup } } #})))))

#(define (markup-list-or-markup? x)
   (or (markup-list? x) (markup? x)))

% This command accepts either a markup (for a single-line
% footnote) or a markup list (for a multi-line footnote).
% The baseline skip between the lines of a multi-line
% footnote is controlled by the paper variable
% `text-font-defaults.baseline-skip`.
myFootnote =
  #(define-music-function (mark offset text item)
     ((markup?)
      number-pair?
      markup-list-or-markup?
      symbol-list-or-music?)
     (let ((text (if (markup? text) (list text) text)))
       (if mark
           #{ \footnote #mark #offset
                \markup \footnote-struts #text #item #}
           #{ \footnote #offset
                \markup \footnote-struts #text #item #})))

\book {
  \header { tagline = ##f }

  \paper {
    text-font-defaults.baseline-skip = 1.8

    footnote-dist = 3.5
    footnote-padding = 0\mm
    footnote-separator-markup =
      \markup { \override #'(span-factor . 1/3) \draw-hline }
    footnote-number-raise = -0.5\mm
  }

  \markup "time-based footnotes"

  \score {
    \relative c'' {
      r1 |
      \myFootnote #'(-0.5 . -1)
        \markuplist {
          \override #'(line-width . 40)
          \wordwrap-lines {
            Meter change. This is a multi-line footnote
            grob. }
        } Staff.TimeSignature
        \time 3/4
      \myFootnote #'(1 . -1)
        \markuplist {
          \override #'(line-width . 40)
          \wordwrap-lines {
            Note stem. This is another multi-line footnote
            grob with a lot of senseless text. }
        } Stem
        <c e g>4 q q |
      \myFootnote #'(-0.5 . 2) "Bar line." Staff.BarLine
        q q
      \myFootnote #'(0.5 . -1) "Key change." Staff.KeySignature
        \key c \minor q |
    }
  }
}