Stop trying to deduce whether the document is being formatted for a
typesetter (a device that can use proportional fonts) or a terminal (a
device that generally can't) by asking the formatter to measure
formatted texts. Instead, use the built-in `n` and `t` conditions that
nroff and troff have supported for this purpose since 1976 at the
latest. All known troff implementations support these.
https://www.gnu.org/software/groff/manual/groff.html.node/Operators-in-Conditionals.html
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