How to globally add kerning between f and right parenthesis using TeX Gyre Termes?

Question

I'm using TeX Gyre Termes as text font. On 2nd level enumerations, in the label corresponding to the letter f, the upper loop of the letter touches the upper tip of the right parenthesis, as illustrated.

How can I globally add kerning between the letter f and the right parenthesis in order to avoid this effect? I would favor a solution that could be used with standard latex or pdflatex.

Edit: here's code that reproduces the situation.

\documentclass{article}
\usepackage{tgtermes}
\begin{document}
\begin{enumerate}
\item This is level 1.
\begin{enumerate}
\item This is level 2.
\item B
\item C
\item D
\item E
\item F
\end{enumerate}
\end{enumerate}
\end{document}

Answer 1

It's a bad bug indeed in the metrics for TeX Gyre Termes. Note that the same happens with the OpenType version. And also with newtxtext (that uses a different clone of Times New Roman)

You can at least obviate to the problem by redefining \labelitemii:

\documentclass{article}
\usepackage{tgtermes}

\renewcommand{\labelenumii}{(\theenumii\/)} % add the italic correction

\begin{document}
\begin{enumerate}
\item \begin{enumerate}% go to the second level
\setcounter{enumii}{5}% print just the f item
\item x
\end{enumerate}
\end{enumerate}

\end{document}

It's a fact that all clones of Times New Roman available in TeX distributions exhibit the same problem. In the TFM files for Computer Modern we find (abridged version)

(LIGTABLE
   (LABEL C f)
   (KRN O 51 R 0.077779)

which means that Computer Modern applies a small kerning between an “f” and a closed parenthesis (ASCII octal '51).

The rm-qtmr font (TeX Gyre Termes under OT1 encoding, but it's the same for ec-qtmr, used for the T1 encoding) has an extensive kerning table for “f”, but misses the closed parenthesis.

The same happens with the fonts used by newtxtext and by mathptmx.

This bug should be made known to the maintainers of the font packages. In the case of Computer Modern the kerning is small, because the drop of the “f” is not so much outside the bounding box. A larger kerning is needed with Times New Roman, where the drop protrudes more, but the fonts define none.

Answer 2

Here is something that is rather a comment, which I am though not allowed to post as I have no reputation points. I am writing as a proxy to the developers, who take the following position in regard to the suggestion that the problem discussed is a bug in TeX Gyre Termes (quoting):

TeX Gyre Termes is an extension and substitution for the Times font. Neither Adobe Times nor Times New Roman have a kern between ‘f’ and ‘parenright’. In many fonts (and all Times-like) these characters touch each other. Only a few fonts, e.g., Computer Modern or Lucida Bright, have a kern between ‘f’ and ‘parenright’. So it is rather a font feature than a bug.