PS.
I never really sat down to understand the mechanism of size selection,
but reading the definition of \abs-fontsize backwards, I obtain:
Turns out it's actually quite simple.
The internal "relative" size is in units of 'magstep', which are
designed such that 6 magstep units precisely mean a doubling of the
size. Since this is a logarithmic scale, we obtain a nice additivity
feature:
\markup \fontsize #2 \fontsize #3 magicalmysterytrainride
is equivalent to
\markup \fontsize #5 magicalmysterytrainride
The paper parameter text-font-size (which I had never encountered before)
\paper {
text-font-size = 24
}
uses absolute font sizes (defaulting to 11 when not changed by
#(set-global-staff-size ...)). Hence the way to obtain the current
absolute font size for a markup is to read the text-font-size parameter
and multiply it with the font-size property (which is in magstep units,
so has to be turned into the actual multiplicative factor by using the
magstep function) of the markup property chain.
Lukas
