Re: Opinions: expressive text and markup sizes

[Aaron Hill]

On 2018-07-08 12:54, Abraham Lee wrote:
> Nothing special. Though I have dreamed of a function to do it
> automatically, it just takes a bit of trial and error to find the right
> size because each font has a different x-height. I almost never use an
> absolute font size outside of the header. If the global staff size is
> relatively small e.g. less than 16pt, then it wouldn’t hurt to make the
> text size a little bit larger.

Here is a hack, which I suspect has holes that will need patching:

%%%%
  \version "2.19.82"

  #(define-markup-command (fontsize-x-height layout props size arg) 
(number? markup?)
    (let* ((y-extent (ly:stencil-extent
                      (ly:text-interface::interpret-markup layout props 
(markup "x")) Y))
           (scale-factor (* (/ size (cdr y-extent)) 1.125)))
      (interpret-markup layout props #{ \markup \magnify #scale-factor 
#arg #})))

  \score {
    <<
      \new Voice { s1 }
      \new Lyrics { \lyricmode {
        \markup \roman \fontsize-x-height #1 "Oxy" 4
        \markup \sans \fontsize-x-height #2 "Oxy" 4
        \markup \typewriter \fontsize-x-height #3 "Oxy" 4
        \markup \italic \fontsize-x-height #4 "Oxy" 4
      } }
    >>
    \layout { \context { \Lyrics
        % Force overlap with staff lines to use them as a ruler.
        \override VerticalAxisGroup.nonstaff-relatedstaff-spacing =
          #'((basic-distance . 2) (minimum-distance . 0)
            (padding . -20) (stretchability . 0))
    } }
  }
%%%%

The principle seems sound.  Use ly:stencil-extent to measure the height 
of a single "x", compute the necessary scaling factor and \magnify.  
However, there is something odd with the units returned.  I 
experimentally found that a fudge factor of 1.125 appeared to mostly 
correct things, but I am almost certainly just overlooking something 
important.

-- Aaron Hill