Thanks Max that works perfectly! But It would still be useful if I could
change families inside a MPpage.

On Tue, May 31, 2022 at 1:31 AM Max Chernoff <mseven@telus.net> wrote:

> > 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
>