https://github.com/TeX-Live/texlive-source/blob/457f9684cbdfc29fb2f0b48f848dd7ff605dc407/texk/web2c/xetexdir/XeTeXFontMgr.cpp#L466
is making the same conversion that you described. David On Mon, 26 Jan 2026 at 16:15, Martin Ruckert <[email protected]> wrote: > Hi all! > > This is a bit of a technical question: > > I use the function hb_ot_layout_get_size_params() to get the design size > of an OpenType font. The result specifies a design size in 1/10 of a point. > So, a design size of 100 means 10pt. OpenType/Harfbuzz assumes that 72 > pt = 1 inch. > TeX on the other hand assumes that 72.27 pt = 1 inch. So, to convert a > design > size of 100 found for an OpenType font to TeX's points, I should > divide by 10 and then by 72 (giving the design size in inch) > and then multiply by 72.27 to get TeX points. > When I use this formula in HiTeX, my fonts are slightly larger than in > XeTeX > and so are inter-word-spaces and inter-line-skips. > If I do not use the extra divide and multiply, my fonts are still not the > same size as those produced by XeTeX. > > So how does XeTeX compute the design size of an OpenType font? > > Regards > Martin > > -- > Martin Ruckert > Hochschule München > Fakultät für Informatik und Mathematik > >
