%% This is part of the OpTeX project, see http://petr.olsak.net/optex

\_famdecl [Fraunces] \Fraunces {Display, "Old Style" soft serif typeface}
        {\wonky} {\rm \bf \it \bi} {Bonum}
        {[Fraunces-VariableFont_SOFT,WONK,opsz,wght]}
        {\_def\_fontnamegen {[Fraunces-\_currV VariableFont_SOFT,WONK,opsz,wght]:-liga;%
         axis={wght=\_f_getwght{+300},opsz=\_the\_f_opsz,soft=\_the\_f_soft};\_wonkyV\_fontfeatures}}

% \_f_getwght{+300} returns \the\wght but if \bf or \bi is processed then it returns \wght+300.
\_def \_f_getwght#1{\_if b\_ea\_ignoresecond\_famv \_the\_numexpr \_f_wght#1\_relax \_else \_the\_f_wght \_fi}

\_wlog{\_detokenize{%
Modifiers:^^J
 \wonky ..... alternative strokes^^J
 \thin ...... \rm, \it = Thin, \bf, \bi = Normal^^J
 \light ..... \rm, \it = Light, \bf, \bi = Medium^^J
 \normal .... \rm, \it = Normal, \bf, \bi = Bold^^J
 \bolder .... \rm, \it = Medium, \bf, \bi = Black^^J%
Variable font parameters:^^J
 \wght ...... 100--1000 (default 400): weight of the strokes^^J
 \opsz ...... 6--144 (default 14): optical size modification^^J
 \ssoft ..... 0--100 (default 0): softness of serifs^^J
 Use \wght=650 \ssoft=50 (for example). It acts like others font modifiers.^^J%
Extended variants:^^J
 \tf \ti .... Thin, ThinItalic^^J
 \lf \li .... Light, LightItalic^^J
 \mf \mi .... Medium, MediumItalic^^J
 \kf \ki .... Black, BlackItalic^^J
}}

\_ifx\_f_wght\_undefined \_newcount\_f_wght \_f_wght=400 \_newpublic \_let\wght=\_f_wght  \_fi
\_ifx\_f_opsz\_undefined \_newcount\_f_opsz \_f_opsz=14  \_newpublic \_let\opsz=\_f_opsz  \_fi
\_ifx\_f_soft\_undefined \_newcount\_f_soft \_f_soft=0   \_newpublic \_let\ssoft=\_f_soft \_fi

\_moddef \resetmod {\_fsetV wonky={} \_fvars {} {} Italic- Italic- }
\_moddef \wonky    {\_fsetV wonky=+ss01; }
\_moddef \thin     {\_f_wght=100 }
\_moddef \light    {\_f_wght=250 }
\_moddef \normal   {\_f_wght=400 }
\_moddef \medium   {\_f_wght=550 }
\_let\_thinM=\thin \_let\_lightM=\light \_let\_mediumM=\medium

\_famvardef \tf    {\_thinM \_rm}
\_famvardef \ti    {\_thinM \_it}
\_famvardef \lf    {\_lightM \_rm}
\_famvardef \li    {\_lightM \_it}
\_famvardef \mf    {\_mediumM \_rm}
\_famvardef \mi    {\_mediumM \_it}
\_famvardef \kf    {\_mediumM \_bf}
\_famvardef \ki    {\_mediumM \_bi}

\_initfontfamily % new font family must be initialized

\_loadmath {[texgyrebonum-math]}

\_endcode

This is an example of a font-file used for a variable fonts.

\begitems
* Declare counters with the same names as parameters of axis. 
* Use `\_ifx\_...\_undefined` in order to more font-files with variable fonts can be loaded.
* Use `axis={...}` in font features area in the `\_fontnamegen` macro.
* Print about axis parameters of given font to the log using `\_wlog`.
* The `\_f_getwght` macro should be declared same in all font-files with variable fonts.
  It enables \bf and \bi variants implemented as the given shift of the current wght parameter.
* You can declare more variants by `\famvardef`.
* You can declare font modifiers and font variants using values of axis parameters.
\enditems