Babel standard family and .otf font features

Question

Compiling this simple code to apply a particular Style Set locally:

\documentclass{article}
\usepackage{fontspec}
\usepackage[italian]{babel}
\babelfont{rm}[Numbers={Proportional,OldStyle},RawFeature=+calt]{EBGaramond}
\newfontfamily\myfont[Numbers={Proportional,OldStyle},RawFeature={+calt,+ss06}]{EBGaramond}

\begin{document}

Q \textsc{Q} \textsc{q}

\myfont{Q  \textsc{Q} \textsc{q}}

\end{document}

I receive:

Package babel Info: The current font is not a babel standard family:
(babel)             EBGaramond:mode=node;script=latn;language=dflt;+pnum;+onum;
+calt,+ss06;
(babel)             There is nothing intrinsically wrong with this warning, and

(babel)             you can ignore it altogether if you do not need these
(babel)             families. But if they are used in the document, you should 
be
(babel)             aware 'babel' will no set Script and Language for them, so
(babel)             you may consider defining a new family with \babelfont.

How should I correct \newfontfamily?

Thank you

Answer 1

In this case, you can switch to the standard font and add the font feature. You seem to want the command to change the text within brackets, but what the \myfont command actually does is change the font to EB Garamond stylistic set 6 from that point on. So, here is a demo of how to do it three different ways:

• A \textswash command, like \textsc or \textsf
• A \swashstyle command, like \scshape or \sffamily
• Commands \Qswash for a capital sqashed Q and \qswash for a small-caps swashed Q

\documentclass{article}
\usepackage[italian]{babel}
\usepackage{fontspec}

\babelfont{rm}[Numbers={Proportional,OldStyle},RawFeature=+calt]{EBGaramond}
\newcommand\swashstyle{\rmfamily\addfontfeature{StylisticSet=6}}
\DeclareTextFontCommand\textswash{\swashstyle}
\newcommand\Qswash{\textswash{Q}}
\newcommand\qswash{\textswash{\scshape q}}

\begin{document}

\noindent Q \textsc{Q} \textsc{q} \\
\textswash{Q  \textsc{Q} \textsc{q}} \\
\Qswash \textsc{\Qswash} \qswash \\
{\swashstyle Q \textsc{Q} \textsc{q}}

\end{document}

You could also ignore the warning. Like the message says, it’s harmless.

Answer 2

EDIT: looking at p. 25-26 of babel's documentation, I've found this way:

\documentclass{article}
\usepackage{fontspec}
\usepackage[italian]{babel}
\babelfont{rm}[Numbers={Proportional,OldStyle},RawFeature=+calt]{EB Garamond}
\babelfont{myfont}[Numbers={Proportional,OldStyle},RawFeature={+calt,+ss06}]{EB Garamond}

\begin{document}

Q \textsc{Q} \textsc{q}

\textmyfont{Q} {\myfontfamily \textsc{Q} \textsc{q}}

\end{document}

Another way: use polyglossia instead of babel. Then, use \addfontfeature to activate the +ss06 feature.

\documentclass{article}
\usepackage{fontspec}
\usepackage{polyglossia}
\setmainlanguage{italian}
\setmainfont[Numbers={Proportional,OldStyle},RawFeature={+calt}]{EB Garamond}

\begin{document}

Q \textsc{Q} \textsc{q}

{\addfontfeature{RawFeature=+ss06} Q  \textsc{Q} \textsc{q}}

\end{document}