Controling underline depth in math mode

Question

I use the ulem package to control the depth of underlines by setting

\renewcommand{\ULdepth}{1pt}

This works fine outside math mode. However, when using \uline inside math mode, I seem to lose control over the underline depth. (Adding \smash doesn't really solve the problem either.)

\documentclass{article}

\usepackage[normalem]{ulem}
\setlength{\parskip}{15pt} % add space between paragraphs for illustration

\begin{document}

\renewcommand{\ULdepth}{1pt} 
\uline{normal text} $\uline{f(x)=y}$

\uline{normal text} $\uline{\smash{f(x)=y}}$

\renewcommand{\ULdepth}{10pt}
\uline{normal text} $\uline{f(x)=y}$

\end{document}

enter image description here

Is there a way to "regain control" over underline depth within math mode. If such control is not possible with the ulem package (I also tried with soul, which didn't work), are there other packages that can achieve the purpose of making the depth of underlines uniform both inside and outside math mode?

do you want to underline the entire expression or subterms? If the former you can simply do \uline{normal text} \uline{$f(x)=y$} and it seems to obey the parameter — David Carlisle, Sep 13 '13 at 22:11
@DavidCarlisle: I know that \uline{$<math content>$} works. But I'm underlining texts in the game environment provided by Martin Osborne's sgame package, in which the cells in a matrix is automatically set in math mode. So when I do use \uline in that environment, it would be as if I'm using $\uline{...}$ . — Herr K., Sep 13 '13 at 22:11
See http://tex.stackexchange.com/questions/126291/list-of-underlining-packages-pros-and-cons/126358#126358 where the censor package has been hacked to permit underlining in math mode. You can set the underrule depth and the underrule thickness. — Steven B. Segletes, Sep 13 '13 at 22:15
As a follow-up on my prior comment, \xblackout{abc} $\mblackout[1pt]{y = x^2}$ seems to align the math underline and text underline, regardless of descenders in the math mode. — Steven B. Segletes, Sep 13 '13 at 22:30
@StevenB.Segletes: So in general, is it right that if I set \censorruledepth=<length>, then I'll just have to use the optional argument [<length>] with \mblackout to align the underlines in the two modes? — Herr K., Sep 14 '13 at 07:31

score 6 · Accepted Answer · answered Sep 13 '13 at 22:32

6

You can use $\mbox{\uline{$....$}}$ if you want to underline a subterm of the math with ulem text settings.

answered Sep 13 '13 at 22:32

David Carlisle

757,742

score 5 · Answer 2 · edited Apr 13 '17 at 12:35

This is an extension to David's answer:

It defines \mathuline that can be used in math mode to get the text mode version of \uline, using David's trick. Additionally \mathpalette is used to get the correct math style.
[Optional] \uline is redefined to use \mathuline in math mode instead of the default \underline. But beware, if you have larger symbols and formulas with larger depth (e.g. \int, \frac), then the line will cross the formula.

Example file:

\documentclass{article}
\usepackage{ulem}

\makeatletter
\newcommand*{\saved@uline}{}
\let\saved@uline\uline

\newcommand*{\mathuline}{%
  \mathpalette{\math@uline\saved@uline}%
}
\newcommand*{\math@uline}[3]{%
  % #1: ulem command
  % #2: math style
  % #3: contents
  \mbox{#1{$#2#3\m@th$}}%
}

% optional
\renewcommand*{\uline}{%
  \relax  
  \ifmmode
    \expandafter\mathuline
  \else
    \expandafter\saved@uline
  \fi
}
\makeatother

\begin{document}
\uline{normal text} $\uline{f(x)=y}$
\end{document}

Controling underline depth in math mode

2 Answers2

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