TextScript isn't entirely scaled, while using another "staff-size"

[Thomas Morley]

Hi,

the following example shows that the markup isn't scaled correct,
according to the changed "staff-size"

\version "2.15.20"

music = {
        c'-\markup { "XXX" \draw-line #'(0 . 4) }
}

\new StaffGroup <<
\new Staff \with { fontSize = #-20
                   \override StaffSymbol #'staff-space = #(magstep -20)
                   \override StaffSymbol #'thickness = #(magstep -20) }
                { \music }

\new Staff
        { \music }
>>


Cheers,
  Harm