Unicode character ſ (U+17F) in LyX 2.3

Question

How to use the following character ſ (U+17F) in LyX? Setting the UTF8 encoding does not work:

Package inputenc Error: Unicode character Ĺż (U+17F)

The complete source code of the document is:

\documentclass[english]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\begin{document}
ſ
\end{document}

I have also tried to use:

\DeclareUnicodeCharacter{17F}{ſ}

Thanks for your help.

Answer 1

First we have to find a way to insert the needed glyph. The standard font Computer Modern does not include a ſ, so another font is needed. A good alternative is Latin Modern, which should be mostly compatible with Computer Modern but features a significantly wider range of characters. Latin Modern has ſ encoded in slot 115 (ASCII s) of the TS1 encoding.

To make the TS1 encoding available, replace

\usepackage[T1]{fontenc}

with

\usepackage[TS1,T1]{fontenc}

Then you have two options: Use Latin Modern for you entire document or only use one glyph from this font. If you want to use the complete font, add

\usepackage{lmodern}
\DeclareUnicodeCharacter{17F}{{%
  \fontencoding{TS1}%
  \selectfont s%
}}

To avoid changing the global font, you can instead add

\DeclareUnicodeCharacter{17F}{{%
  \fontencoding{TS1}%
  \fontfamily{lmr}%
  \selectfont s%
}}

This tells LaTeX to use the s from encoding TS1 (and family lmr), whenever Unicode character U+017F is requested.

\documentclass[english]{article}
\usepackage[TS1,T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{lmodern}
\DeclareUnicodeCharacter{17F}{{%
  \fontencoding{TS1}%
  \selectfont s%
}}
\begin{document}
ſ
\end{document}

A more elegant solution would be switching to LuaLaTeX, there you can directly use ſ as long as the character exists in your font.