# MinionPro kerning math mode and punction (comma)

I'm trying to write a short explantion of the quantities in a formula but I think the kerning doesn't really work. (or I'm wrong?).

\documentclass[12pt]{scrreprt}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[fullfamily,opticals,minionint,footnotefigures]{MinionPro}
\usepackage{icomma}

\usepackage{array}
\newenvironment{conditions}[1][with:]
{#1 \begin{tabular}[t]{>{$}l<{$} @{${}-{}$} p{10cm}}}
{\end{tabular}\\[\belowdisplayskip]}

\begin{document}

\begin{conditions}
W,~L,~t_{\mathrm{OX,eff}}                                   &  $\dots$\\
\textit{W\textnormal{,}}~\textit{L\textnormal{,}}~t_{\mathrm{OX,eff}} &  $\dots$\\
\mathit{W,~L,}~t_{\mathrm{OX,eff}}                  &  $\dots$
\end{conditions}

\end{document}


The image shows the MWE with cm as well as minonpro but it seems like the kerning ist worse in mminion.

I'll analyze the case of Computer Modern, because I don't have Minion, with the following input file:

\documentclass{article}

\begin{document}
\showoutput

$W,$

$\textit{W,}$

$\mathit{W,}$
\end{document}


showing what \showoutput writes in the log file.

## Case 1: $W,$

....\mathon
....\OML/cmm/m/it/10 W
....\kern1.3889
....\kern-1.66667
....\OML/cmm/m/it/10 ;
....\mathoff


The first kern is the italic correction, that TeX adds after an ordinary symbol, if it has one defined, the second one is the kerning between W and comma, as defined by the font.

## Case 2: \textit{W,}

....\mathon
....\hbox(6.83331+1.94444)x13.05548
.....\OT1/cmr/m/it/10 W
.....\OT1/cmr/m/it/10 ,
....\mathoff


The two characters are typeset in the text italic font, with no kerning because there's none defined between them.

## Case 3: $\mathit{W,}$

....\mathon
....\hbox(6.83331+1.94444)x14.60272
.....\OT1/cmr/m/it/10 W
.....\kern1.8361
.....\OML/cmm/m/it/10 ;
....\mathoff


TeX adds the italic correction for W, as in case 1, but there's no kerning because the two characters are from different font. With $\mathit{W},$ (which is more correct), we'd get

....\mathon
....\OT1/cmr/m/it/10 W
....\kern1.8361
....\OML/cmm/m/it/10 ;
....\mathoff


No additional box is used, because \mathit involves only one character.

## General notes

We see a semicolon where a comma would be expected, because the math comma in a font under the OML encoding is in the place of the semicolon: the math code of the comma is "613B, which means punctuation (6), from math group 1 and slot 3B (which in ASCII is the semicolon).

## What happens with Minion?

The Minion font has, as far as I know, some very dramatic kerning between letters and punctuation (for instance the apostrophe). This shows very well in case 2, where text mode, rather than math mode, is used. In cases 1 and 3, the kerning is absent possibly because the W is taken from a different font than the math letter one, so case 1 and 3 are essentially the same; one should examine the math font setup in MinionPro.sty and the font metric files to know precisely: it's very possible that the package defines math italic just as text italic.

## What should be done?

The input should be $W$, $L$, $t_{\mathrm{OX,eff}}$, because these are three distinct formulas and the commas are textual, not mathematical.

• Thanks for your command, I will look in to it, tomorrow. But isn't the kerning for case 2 \textit{W\textnormal{,}}~\textit{L\textnormal{,}}~t_{\mathrm{OX,eff}} correct or should there be a bigger space as in the text body between $W$` and the comma? – jlk Sep 27 '15 at 22:30
• @harryhaller No, it's incorrect. See the last paragraph. – egreg Sep 27 '15 at 22:33