Superscripts after fs - spacing

Question

When certain characters in superscripts follow certain letters ("f" at least) they collide. I'm using a numeric superscripted citation style, but the problem is more general that that as the following MWE demonstrates:

\documentclass{article}
\begin{document}
f$^6$ f$^1$ y$^6$

f\,$^6$ f\,$^1$ y\,$^6$
\end{document}

In the first line, all but the first example look right; in the second line even f$^6$ looks rather wide, the other superscripts are floating off into the middle distance. This probably applies to \footnotes (with letters) as well, I just don't happen to have a combination that demonstrates that.

Can it really be right that for certain combinations I have to add a manual correction (\kern0.05em looks about right)? Or is there a more general solution?

Answer 1

The font "knows" the adjustment needed here and makes it available as the italic correction \/

\documentclass{article}
\begin{document}
f$^6$ f$^1$ y$^6$

f\textsuperscript6 f\textsuperscript1 y\textsuperscript6 

f\/\textsuperscript{6} f\/\textsuperscript{1} y\/\textsuperscript{6}  $\leftarrow$ this one

f\,$^6$ f\,$^1$ y\,$^6$

f\kern0.05em$^6$ f\kern0.05em$^1$ y\kern0.05em$^6$
\end{document}

Answer 2

Using f$^6$ is not the best way to cope with this, because it's not math, so

f\textsuperscript{6}

would be a better way. The problem is that the character “f” slightly extends beyond its bounding box. There is a built-in mechanism for coping with this, the italic correction that, despite its name, can come to rescue also for non slanted fonts, which are the ones where the problem presents more often.

Unfortunately, \textsuperscript doesn't add the italic correction, which it should, in my opinion. More unfortunately, patching \textsuperscript is not sufficient for footnotes.

Let's do a test document:

\documentclass{article}

\begin{document}
f\textsuperscript{6} f\textsuperscript{1} y\textsuperscript{6}

f\footnote{A}
f\footnote{B}
f\footnote{C}
f\footnote{D}
f\footnote{E}
f\footnote{F}

\setcounter{footnote}{0}

y\footnote{A}
y\footnote{B}
y\footnote{C}
y\footnote{D}
y\footnote{E}
y\footnote{F}

\end{document}

that outputs

Now we patch \textsuperscript and \footnote; actually a couple of internal macros need to be patched.

\documentclass{article}
\usepackage{etoolbox}

\makeatletter
\pretocmd\@textsuperscript{\/}{}{}
\patchcmd\@footnotemark{\edef}{\/\edef}{}{}
\makeatother

\begin{document}
f\textsuperscript{6} f\textsuperscript{1} y\textsuperscript{6}

f\footnote{A}
f\footnote{B}
f\footnote{C}
f\footnote{D}
f\footnote{E}
f\footnote{F}

\setcounter{footnote}{0}

y\footnote{A}
y\footnote{B}
y\footnote{C}
y\footnote{D}
y\footnote{E}
y\footnote{F}

\end{document}

and we get

You can see that the output with y is unaffected, while it's improved for f, because we essentially add \/ before \textsuperscript and \footnote. If the font is properly designed, the italic correction should compensate the right amount of spacing.

A possible patch for \supercite is

\patchcmd{\mkbibsuperscript}{\unspace}{\unspace\/}{}{}

Example.

\documentclass{article}
\usepackage{biblatex}
\makeatletter
\pretocmd\@textsuperscript{\/}{}{}
\patchcmd\@footnotemark{\edef}{\/\edef}{}{}
\patchcmd{\mkbibsuperscript}{\unspace}{\unspace\/}{}{}
\makeatother

\addbibresource{xampl.bib}

\begin{document}
\nocite{*}

f\supercite{article-full}

\printbibliography
\end{document}