Changing the font family of the mini-navigation in the 'Frankfurt' beamer theme

Question

I am currently in process of tweaking the look of my beamer presentation and would like the navigational elements (TOC and mini-navigation, that is shipped alongside the Frankfurt theme) to use Sans-Serif fonts, while the rest of the presentation is supposed to use Roman fonts.

This wasn't such a problem for the TOC, but I have trouble correctly selecting the text above the navigational circles.

Referring to this answer, I tried to use mini, but that didn't change anything.

Here is the current code snippet:

\setbeamerfont{mini}{family=\sf}
\setbeamerfont{section in toc}{size=\scriptsize,family=\sf}
\setbeamerfont{subsection in toc}{size=\tiny,family=\sf}

Answer 1

I'm afraid I'm not completely sure what you want to achieve, as sans fonts are the same as sans-serif fonts, that is to say fonts without the little lines at the end of the strokes (like the one used on this website). I guess you're using something like

\usefonttheme{serif}

to get a serif typeface for the normal text of your presentation, but you still want to retain the default sans-serif typeface in the headline. This can be achieved by changing the beamer theme section in head/foot:

\setbeamerfont{section in head/foot}{family=\sffamily}

(using \sffamily instead of the deprecated \sf).

Full example code

\documentclass{beamer}
\usetheme{Frankfurt}
\usefonttheme{serif}
\setbeamerfont{section in head/foot}{family=\sffamily}
\begin{document}
\section{Section 1}
\subsection{Subsection}
\frame{Serif typeface}\frame{Serif typeface}\frame{Serif typeface}
\section{Section 2}
\subsection{Subsection}
\frame{Serif typeface}\frame{Serif typeface}\frame{Serif typeface}\frame{Serif typeface}\frame{Serif typeface}
\section{Section 3}
\subsection{Subsection}
\frame{Serif typeface}\frame{Serif typeface}
\end{document}