# Aligning \overline to “italics” font but starting with upshape

I want to write an X with a bar on top. The X should be upright, but in headings it should be italics. The bar should be in the correct position. So my question is a variant of Aligning \overline to "italics" font. I started to play with jfbu's solution but cannot get the original upshape position to work.

\documentclass{article}

\usepackage{xspace}

\newbox\usefulbox

\makeatletter
\def\getslant #1{\strip@pt\fontdimen1 #1}

\def\skoverline #1{\mathchoice
{{\setbox\usefulbox=\hbox{$\m@th\displaystyle #1$}%
\dimen@ \getslant\the\textfont\symletters \ht\usefulbox
\divide\dimen@ \tw@
\kern\dimen@
\overline{\kern-\dimen@ \box\usefulbox\kern\dimen@ }\kern-\dimen@ }}
{{\setbox\usefulbox=\hbox{$\m@th\textstyle #1$}%
\dimen@ \getslant\the\textfont\symletters \ht\usefulbox
\divide\dimen@ \tw@
\kern\dimen@
\overline{\kern-\dimen@ \box\usefulbox\kern\dimen@ }\kern-\dimen@ }}
{{\setbox\usefulbox=\hbox{$\m@th\scriptstyle #1$}%
\dimen@ \getslant\the\scriptfont\symletters \ht\usefulbox
\divide\dimen@ \tw@
\kern\dimen@
\overline{\kern-\dimen@ \box\usefulbox\kern\dimen@ }\kern-\dimen@ }}
{{\setbox\usefulbox=\hbox{$\m@th\scriptscriptstyle #1$}%
\dimen@ \getslant\the\scriptscriptfont\symletters \ht\usefulbox
\divide\dimen@ \tw@
\kern\dimen@
\overline{\kern-\dimen@ \box\usefulbox\kern\dimen@ }\kern-\dimen@ }}%
{}}
\makeatother

\newcommand{\xbar}{$\skoverline{X}$\xspace}
\newcommand{\xbarup}{\mbox{$\overline{\mbox{X}}$}\xspace}

\newcommand{\xbarupsk}{\mbox{$\skoverline{\mbox{X}}$}\xspace}

\begin{document}\thispagestyle{empty}

\xbar-Theory
\emph{\xbar-Theory} (correct)

\xbarup-Theory (correct)
\emph{\xbarup-Theory}

\xbarupsk-Theory
\emph{\xbarupsk-Theory}

\end{document}

• the way you're using it, the X with overbar is text, not math. unfortunately, the usual text accent \= isn't long enough. what is needed is a diacritic equivalent to unicode U+0305. this may be available in the xits fonts. – barbara beeton Mar 1 '18 at 14:35
• Hm, but then the X may be different from my X, which is Linux Libertine. – Stefan Müller Mar 1 '18 at 15:34
• i wasn't suggesting to use another font entirely. it should be potentially possible to access just one or a few characters from an "extra" font, similarly to what is done here (although this example is for a math symbol): Importing a single symbol from a different font – barbara beeton Mar 1 '18 at 16:30
• Yes, but the X would be different. – Stefan Müller Mar 2 '18 at 6:55
• If there was a way to detect whether I am in \emph or not, I could use either of the macros. – Stefan Müller Mar 2 '18 at 7:00