Variable Fonts

What are variable fonts

MDN Web Docs define variable fonts as:

“Variable fonts are an evolution of the OpenType font specification that enables many different variations of a typeface to be incorporated into a single file, rather than having a separate font file for every width, weight, or style.”

Getting information about the variable font

It is better to start playing with a variable font (such as Recursive, which you can download for free at GitHub).

Once you put them in a place where ConTeXt can find them, just execute:

\usemodule[fonts-variable]
\starttext
  \showfontvariations[font=file:recursive.ttf]
\stoptext

This will generate a PDF document with information about parameters, OpenType features (grouped by type) and axes (design axes cannot be accessed by the user). Instances are also provided with values for each used axis.

You may have either the variable font and the font styles, but there is no gain in having both font styles (or instances [individual font files]) and the variable font. And there is room for font name clashes (when variable fonts aren’t named differently than their instances).

The axis information displays a table with: tag, name, minimum, default and maximum values (Recursive has the following axes, tagged as mono, casl, wght, slnt and crsv).

Using the variable axes

Access to the variable font configuration is achieved through a font feature (using the axis key), such as in:

\definefontfeature[myaxisa][axis={wght=500, mono=1}]
\definefontfeature[myaxisb][axis={wght=500, mono=1, casl=1}]
\definefontfeature[myaxisd][axis={wght=500, mono=1, casl=1, crsv=1}]
\definefontfeature[myaxise][axis={wght=500, mono=1, casl=1, crsv=1, slnt=-15}]
\definefontfamily[mainface][rm][Recursive]
  [features={default, myaxisa}]
\definefontfamily[mainfaceb][rm][Recursive]
  [features={default, myaxisb}]
\definefontfamily[mainfaced][rm][Recursive]
  [features={default, myaxisd}]
\definefontfamily[mainfacee][rm][Recursive]
  [features={default, myaxise}]
\setupbodyfont[mainface]
\starttext
\scale[width=\textwidth]
  {\tf Regular \it Italic}
\scale[width=\textwidth]
  {\mainfaceb\tf Regular \it Italic}
\scale[width=\textwidth]
  {\mainfaced\tf Regular \it Italic}
\scale[width=\textwidth]
  {\mainfacee\tf Regular \it Italic}
\stoptext

This font feature requires a new font instance (it cannot be added with \feature).