Bad positioning of math accents for the beamer standard font

Question

With a recent TeX distribution, the easy answer to this question is "load the sansmathaccent package" (which is Ariel's implementation of my answer). Actually, the corrected font should be loaded automatically by beamer, but somehow this doesn't work at the moment.

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I just went to a math conference where I saw lots of slides prepared with the beamer class that contained badly positioned math accents like these: . The LaTeX file is

\documentclass{beamer}
\begin{document}
\begin{frame}{}
$\tilde M$ $\dot u$ $\hat T$
\end{frame}
\end{document}

As you can see, the accents are centered over the bases of the corresponding letters, i.e., the skew of the letters isn't taken into account. I'm pretty sure that the reason for this is missing entries in the kerning table of the standard math font; see also the discussion of the \skewchar in this post.

I know that one option would be to try other fonts, but I don't like this for two reasons: Firstly, I otherwise do like the appearance of the standard fonts, and secondly, if I use different fonts, then I'll still have to live with looking at the slides of all the others who use the standard fonts. So my questions are: Does there exist a fix that gives me well-behaved standard fonts with beamer, and is there hope that the above LaTeX file will yield correctly positioned accents in some future version of beamer? (I think it wouldn't be a problem to make such a change in the fonts of the class as it won't affect the bounding box of, e.g. \dot u, so it wouldn't lead to any changes in spacing, line breaks and page breaks.)

Answer 1

You can use the \skew macro:

\skew{shift}{accent}{character}

Specifically, I would define macros for the symbols. So they can easily be adjusted later, especially if a font change occurs.

\newcommand*{\Mtilde}{\skew{5}{\tilde}{M}}
\newcommand*{\That}{\skew{3}{\hat}{T}}
\newcommand*{\udot}{\skew{3}{\dot}{u}}

Gives in beamer:

Answer 2

OK, after talking to Joseph Wright I went ahead and wrote a patch for cmssi, which is the standard math font in beamer. The problem is that this font (computer modern sans serif italics) is designed as a text font, so it doesn't contain any information about positioning of accents. Compare these for before and after patching:

Now the answer (hopefully) is in its final version and ready for use. However, what I'm going to write will only work on Unix type systems. Strangely enough, the patch I initially wrote for 10pt works also great for the other sizes.

Here's what you have to do in order to obtain nicely positioned accents. No change to the actual TeX files is needed, and nothing in the output will change except the accent positions. OK, create some testing directory and run the following script. (If you have root rights on your system, you probably want to replace the updmap command with updmap-sys; thanks, Herbert! Moreover, the map file that gets deleted in the end should probably be stored at some proper location, but I'm not sure where.)

# Create the patch file:
echo '17a18,61
>    (LABEL C E)
>    (LABEL C H)
>    (LABEL C M)
>    (LABEL C N)
>    (LABEL C Q)
>    (LABEL C i)
>    (LABEL C j)
>    (KRN O 177 R 0.1)
>    (STOP)
>    (LABEL C J)
>    (KRN O 177 R 0.22)
>    (STOP)
>    (LABEL C e)
>    (LABEL C m)
>    (LABEL C n)
>    (LABEL C r)
>    (LABEL C B)
>    (LABEL C R)
>    (LABEL C S)
>    (LABEL C Z)
>    (KRN O 177 R 0.08)
>    (STOP)
>    (LABEL C c)
>    (LABEL C q)
>    (LABEL C s)
>    (LABEL C z)
>    (KRN O 177 R 0.06)
>    (STOP)
>    (LABEL C v)
>    (LABEL C x)
>    (KRN O 177 R 0.04)
>    (STOP)
>    (LABEL C h)
>    (KRN O 177 R 0.02)
>    (STOP)
>    (LABEL C l)
>    (LABEL C U)
>    (KRN O 177 R 0.11)
>    (STOP)
>    (LABEL C d)
>    (LABEL C C)
>    (LABEL C G)
>    (KRN O 177 R 0.12)
>    (STOP)
25a70
>    (KRN O 177 R 0.1)
61a107
>    (KRN O 177 R 0.04)
62a109
>    (KRN O 177 R 0.03)
68a116
>    (KRN O 177 R 0.08)
70a119
>    (KRN O 177 R 0.04)
77a127
>    (KRN O 177 R 0.1)
79a130
>    (KRN O 177 R 0.07)
86a138
>    (KRN O 177 R 0.08)
87a140
>    (KRN O 177 R 0.06)
93a147
>    (KRN O 177 R 0.09)
95a150
>    (KRN O 177 R 0.06)
103a159
>    (KRN O 177 R 0.08)
104a161
>    (KRN O 177 R 0.1)
111a169
>    (KRN O 177 R 0.05)
112a171
>    (KRN O 177 R 0.06)
120a180
>    (KRN O 177 R 0.08)
122a183
>    (KRN O 177 R 0.07)
124a186
>    (KRN O 177 R 0.08)
127a190
>    (KRN O 177 R 0.14)
134a198
>    (KRN O 177 R 0.05)
140a205
>    (KRN O 177 R 0.01)
143a209
>    (KRN O 177 R 0.1)' > cmssi.patch
# Patch the font metrics of cmssi8, 9, 10, 12 and 17:
for i in 8 9 10 12 17; do
tftopl $(kpsewhich cmssi$i.tfm) > cmssmi$i.pl
patch cmssmi$i.pl cmssi.patch
pltotf cmssmi$i.pl
done
# Include the patched font in beamerbasefont.sty and define its \skewchar:
cp $(kpsewhich beamerbasefont.sty) newbeamerbasefont.sty
sed '
/{OT1}{cmss}{m}{it}/,/{}/{
s|cmssi|cmssmi|g
s|{}|{\\skewchar\\font=127}|}
' newbeamerbasefont.sty > beamerbasefont.sty
# Make the font metric available to the system:
echo 'cmssmi8 cmssmi8 <cmssi8.pfb
cmssmi9 cmssmi9 <cmssi9.pfb
cmssmi10 cmssmi10 <cmssi10.pfb
cmssmi12 cmssmi12 <cmssi12.pfb
cmssmi17 cmssmi17 <cmssi17.pfb' > cmssmi.map
updmap --enable Map=cmssmi.map
# clean up:
rm cmssi.patch cmssmi{8,9,10,12,17}.pl newbeamerbasefont.sty cmssmi.map

This creates six files: five tfm files named cmssmi<n>.tfm , which contain the patched font metrics, and beamerbasefont.sty, which will be used instead of the original beamerbasefont.sty. (I thought that cmssmi is nice for "computer modern sans serif math italics".) Now you're ready to go and test the following example TeX file. This should go into the same testing directory since the above six files are only available there. Feedback is highly appreciated!

\documentclass{beamer}
\newcommand\test{}
\newcommand\testframe[1]{
\renewcommand\test[1]{{$#1 ##1_{{#1 ##1_{#1 ##1}}}$} }
\begin{frame}{}
\test a
\test b
\test c
\test d
\test e
\test f
\test g
\test h
\test i
\test j
\test k
\test l
\test m
\test n
\test o
\test p
\test q
\test r
\test s
\test t
\test u
\test v
\test w
\test x
\test y
\test z
\test A
\test B
\test C
\test D
\test E
\test F
\test G
\test H
\test I
\test J
\test K
\test L
\test M
\test N
\test O
\test P
\test Q
\test R
\test S
\test T
\test U
\test V
\test W
\test X
\test Y
\test Z
\end{frame}
}

\begin{document}
\renewcommand{\baselinestretch}{1.4}\normalsize
\testframe{\dot}
\testframe{\hat}
\testframe{\tilde}
\testframe{\bar}
\end{document}

Answer 3

Apparently the default beamer font is not suitable font for quality math typesetting (lacking proper accent positioning is one aspect, but I suspect there are more).

There is no way to fix this except by using a proper math font, see this for samples of different math fonts with beamer. Of course, it would be much better if beamer maintainers were notified to set a better font by default.

Answer 4

I suggest using

\usefonttheme{professionalfonts}

in the preamble. This turns the math-fonts into serif ones, so that you have a better visual separation between math and normal text. And it gives you proper math fonts.

Answer 5

I find sans-serif fonts ugly for talks. They are hard to read in books, so I don't see any reason to use them in talks, either. The following looks reasonably good to me. (I also slightly adjusted the accenting commands.)

\documentclass[serif]{beamer}
\usepackage{mathptmx}
\usepackage{helvet}
\usepackage{courier}
\begin{document}
\begin{frame}{}
$\widetilde{M}$ $\dot u$ $\widehat{T}$
\end{frame}
\end{document}

Answer 6

I use

\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usefonttheme[stillsansserifsmall]{serif}

and also experience bad positioning of math accents. I use a quick and dirty hack to make some corrections which in most cases work:

\let\oldtilde\tilde
\renewcommand{\tilde}[1]{\,\oldtilde{\!#1}}

\let\oldoverline\overline
\renewcommand{\overline}[1]{\hspace{1pt}\oldoverline{\hspace{-1pt}#1}}

\let\olddot\dot
\renewcommand{\dot}[1]{\,\olddot{\!#1}}

\let\oldhat\hat
\renewcommand{\hat}[1]{\,\oldhat{\!#1}}

Disclaimer: I know that this is not a good idea.