%%%%
\version "2.19.83"
#(define-markup-command
(staff-fontsize layout props size arg)
(number? markup?)
(let* ((staff-space (ly:output-def-lookup layout 'staff-space 1))
(sten (interpret-markup layout props (markup "x")))
(yex (ly:stencil-extent sten Y))
(height (interval-length yex))
(magnification (* size (/ staff-space height)))
(font-size (magnification->font-size magnification)))
(interpret-markup layout props
(markup (#:fontsize font-size arg)))))
test =
\new Staff
\with {
\omit Clef
\omit TimeSignature
\override NoteHead.stencil =
#(lambda (grob)
(grob-interpret-markup grob #{
\markup {
\staff-fontsize #1 "bxq"
\staff-fontsize #2 "bxq"
\staff-fontsize #3 "bxq"
\staff-fontsize #4 "bxq"
} #}))
}
{ e'1 }
\score { \test \layout { #(layout-set-staff-size 12) } }
\score { \test \layout { #(layout-set-staff-size 20) } }
\score { \test \layout { #(layout-set-staff-size 28) } }
%%%%
'x' usually has a flat top and bottom, making it a stable reference. If
the x-height is not your interest, you can substitute 'x' for something
else. Just be aware that some glyphs often have larger physical
dimensions than their ideal bounds as a way to compensate for optic
effects. This is most noticeable with rounded or pointed features. If
you wanted to measure 'o', for instance, you would need to adjust the
height computation:
%%%%
(height (+ (interval-length yex) (* 2 (car yex))))
%%%%
The principle here is to assume that the extent with which the character
descends is the optic adjustment, so we subtract it from the top and
bottom to get the effective height. This only works with glyphs that
are vertically symmetric in this regard. An 'A', for instance, usually
has a flat bottom but the point at the top often extends slightly beyond
its nominal height.
-- Aaron Hill
Thank you very much, Aaron