\part{\LuaTeX-only font features}
\label{sec:luatex-features}

\section{Custom font features}

Pre-2016, it was possible to load an OpenType font feature file to define new OpenType features for a selected font. This facility was particularly useful to implement custom substitutions, for example.  As of \TeX{}Live~2016, \LuaTeX/\pkg{luaotfload} no longer supports this feature, but provides its own internal mechanisms for an equivalent interface.

Any documents using `feature file' options will need to transition to the new interface.
Figure~\ref{fig:featurefile} shows an example.
Please refer to the \LuaTeX/\pkg{luaotfload} documentation for more details.

\begin{figure}
\caption{An example of custom font features.}
\label{fig:featurefile}
\hrule
\begin{Verbatim}
\documentclass{article}
\usepackage{fontspec}
\directlua{
    fonts.handlers.otf.addfeature {
        name = "oneb",
        {
            type = "substitution",
            data = {
                ["1"] = "one.ss01",
            },
        },
        "feature oneb for vollkorn font",
    }
}
\setmainfont{Vollkorn-Regular.otf}[RawFeature=+oneb]
\begin{document}
1234567890
\end{document}
\end{Verbatim}
\hrule
\end{figure}