I'm using the following macro to set the font size via h-height:
\starttexdefinition setxheight [#1][#2] \switchtobodyfont[#1, 12pt] \scratchdimen=\dimexpr#2\relax \switchtobodyfont[#1, \cldcontext{tex.dimen.scratchdimen / tex.sp"1ex" * tex.sp"1em" .. "sp"}] \stoptexdefinition
But I can't figure out how to use that in MPpage.
So it looks like the "\cldcontext" command doesn't work quite right inside "textext", and it also looks like "\switchtobodyfont" doesn't take effect until text is actually typeset when we're inside "textext". This seems to work: \starttexdefinition setxheight [#1] \switchtobodyfont[\the\dimexpr #1 * \number\dimexpr1em\relax / \number\dimexpr1ex\relax \relax] \stoptexdefinition \starttext \switchtobodyfont[adventor] \startMPpage draw textext.origin("\setxheight[1cm]Hello!"); draw (0, 1cm) -- (6cm, 1cm); \stopMPpage \switchtobodyfont[pagella] \startMPpage draw textext.origin("\setxheight[1cm]Hello!"); draw (0, 1cm) -- (6cm, 1cm); \stopMPpage \switchtobodyfont[heros] \startMPpage draw textext.origin("\setxheight[6pt]Hello!"); draw textext.origin("\setxheight[24pt]Hello!"); draw (0, 6pt) -- (6cm, 6pt); draw (0, 24pt) -- (6cm, 24pt); \stopMPpage \stoptext The catch here is that you need to set the font family *before* you start the MPpage. -- Max