Limit VerticalPosition feature to the numbers only

Question

By selecting the feature VerticalPosition = Numerator/Superior/Inferior etc... one may vary the relative position of numbers and other character with respect to the baseline.

For example, this code

\documentclass[12pt, a5paper]{memoir}

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

\setmainfont{Linux Biolinum}

\def\Text{1Inizio del Vangelo secondo me, che sono io. 2Come è scritto nel rotolo del professor Richard: Voce di uno che grida: 3Delle onde fate la trasformata!}

\begin{document}

\Text

\addfontfeature{VerticalPosition = Superior}
\Text

\end{document}

gives as a result this:

The problem holds also if you select other options, like Numerator. Is there any way to limit the vertical position to the only numbers?

Answer 1

In TeX Live 2016, you can use fonts.handlers to adjust font features. Here, I make a new feature, which I’ve called nsup (for “numerical superiors”), defining superiors for numbers only:

\documentclass[12pt,a5paper]{memoir}
\usepackage[italian]{babel}
\usepackage{fontspec}
\directlua{
fonts.handlers.otf.addfeature {
    name = "nsup",
    {
        type = "substitution",
        data = {
            one = "¹",
            two = "²",
            three = "³",
            four = "⁴",
            five = "⁵",
            six = "⁶",
            seven = "⁷",
            eight = "⁸",
            nine = "⁹",
            zero = "⁰",
        }
    },
    "superior numerals only"
  }
}
\setmainfont{linuxbiolinumo}% my system doesn’t recognize the name you used
\def\Text{1Inizio del Vangelo secondo me, che sono io. 2Come è scritto
  nel rotolo del professor Richard: Voce di uno che grida: 3Delle onde
  fate la trasformata!}
\begin{document}
\addfontfeature{RawFeature=+nsup}
\Text
\end{document}

Before 2016, you could write your own feature file, but I no longer have an older system to play with, so I won’t provide an example of that approach (there are questions about it elsewhere on this site). Best to learn the new one, anyway.

This approach is for luatex only, not xetex.

Answer 2

You should use the superscript digits, in my opinion.

Anyway, with XeLaTeX you can use the interchar tokens feature.

\documentclass[12pt, a5paper]{memoir}

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

\setmainfont{Linux Biolinum O}
\newfontfamily{\super}{Linux Biolinum O}[VerticalPosition = Superior]

\newXeTeXintercharclass\superior
\XeTeXcharclass`0=\superior
\XeTeXcharclass`1=\superior
\XeTeXcharclass`2=\superior
\XeTeXcharclass`3=\superior
\XeTeXcharclass`4=\superior
\XeTeXcharclass`5=\superior
\XeTeXcharclass`6=\superior
\XeTeXcharclass`7=\superior
\XeTeXcharclass`8=\superior
\XeTeXcharclass`9=\superior
\XeTeXinterchartoks 0 \superior = {\begingroup\super}
\XeTeXinterchartoks 4095 \superior = {\begingroup\super}
\XeTeXinterchartoks \superior 0 = {\endgroup}
\XeTeXinterchartoks \superior 4095 = {\endgroup}


\def\Text{%
  1Inizio del Vangelo secondo me, che sono io. 
  2Come è scritto nel rotolo del professor Richard: Voce di uno che grida: 
  3Delle onde fate la trasformata!%
}

\begin{document}

\Text

\XeTeXinterchartokenstate=1
\Text

\end{document}