Drawing a border around the progress bar in the Metropolis beamer theme

Question

Hi all and happy new year!

First time poster here and I just had a quick question that I am having trouble solving. I posted a MWE of basic LaTeX beamer code using the Metropolis theme.* I would like to (globally) have the progress bar have a border around it, specifying the color and thickness of the border (let's say a blue border that is 0.25pt thick). How can this be accomplished?

Please let me know if there is anything I can clarify. Thank you very much in advance to anyone kind enough to consider my question.

I hope you all have a happy and healthy 2024!

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*Specifically, the Overleaf template, with frames replaced and with minor modifications in the first line of the MWE code and in the "My Mods" section of the preamble.

---

Minimum Working Example (MWE)

\documentclass[12pt,aspectratio=169,xcolor={svgnames, dvipsnames}]{beamer}

\usetheme[progressbar=frametitle]{metropolis}
\usepackage{appendixnumberbeamer}

\usepackage{booktabs}
\usepackage[scale=2]{ccicons}

\usepackage{pgfplots}
\usepgfplotslibrary{dateplot}

\usepackage{xspace}
\newcommand{\themename}{\textbf{\textsc{metropolis}}\xspace}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% My Mods
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\makeatletter
\setlength{\metropolis@titleseparator@linewidth}{2pt}
\setlength{\metropolis@progressonsectionpage@linewidth}{2pt}
\setlength{\metropolis@progressinheadfoot@linewidth}{2pt}
\makeatother
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%



\title{Metropolis -- Modified}
\subtitle{A modern beamer theme}
% \date{\today}
\date{}
\author{Matthias Vogelgesang}
\institute{Center for modern beamer themes}
% \titlegraphic{\hfill\includegraphics[height=1.5cm]{logo.pdf}}


\begin{document}

\maketitle

\begin{frame}{First Frame}
    blah blah blah?
    \begin{itemize}
        \item blah blah blah.
        \item blah blah.
        \item yadda yadda yadda.
    \end{itemize}
\end{frame}

\begin{frame}{Second Frame}
    blah blah!
    \begin{enumerate}
        \item blah blah blah.
        \item blah blah.
        \item blah blah bah.
    \end{enumerate}
\end{frame}

\end{document}

Answer 1

The progress bar styling is defined using TikZ in the beamer templates progress bar in section page and progress bar in head/foot. The definitions of these templates are available in the metropolis documentation. By copy-pasting those definitions into your MWE and modifying the TikZ code, I was able to get a very simple border around the progress bar (2pt thickness for ease of visibility):

\documentclass[12pt,aspectratio=169,xcolor={svgnames, dvipsnames}]{beamer}

\usetheme[progressbar=frametitle]{metropolis}
\usepackage{appendixnumberbeamer}

\usepackage{booktabs}
\usepackage[scale=2]{ccicons}

\usepackage{pgfplots}
\usepgfplotslibrary{dateplot}

\usepackage{xspace}
\newcommand{\themename}{\textbf{\textsc{metropolis}}\xspace}


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% My Mods
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\makeatletter
\setlength{\metropolis@titleseparator@linewidth}{2pt}
\setlength{\metropolis@progressonsectionpage@linewidth}{2pt}
\setlength{\metropolis@progressinheadfoot@linewidth}{2pt}

% Redefine `progress bar in head/foot` to add border
\newlength{\metropolis@progressinheadfoot@borderwidth}
\setlength{\metropolis@progressinheadfoot@borderwidth}{2pt}
\setbeamertemplate{progress bar in head/foot}{
  \nointerlineskip
  \setlength{\metropolis@progressinheadfoot}{%
    \paperwidth * \ratio{\insertframenumber pt}{\inserttotalframenumber pt}%
  }%
  \begin{beamercolorbox}[wd=\paperwidth]{progress bar in head/foot}
  \begin{tikzpicture}
    % Add blue progress bar border
    \fill[blue] (0,-\metropolis@progressinheadfoot@borderwidth) rectangle (\paperwidth, \metropolis@progressinheadfoot@linewidth+\metropolis@progressinheadfoot@borderwidth);
    \fill[bg] (\metropolis@progressinheadfoot@borderwidth,0) rectangle (\paperwidth-\metropolis@progressinheadfoot@borderwidth, \metropolis@progressinheadfoot@linewidth);
    \fill[fg] (\metropolis@progressinheadfoot@borderwidth,0) rectangle (\metropolis@progressinheadfoot-\metropolis@progressinheadfoot@borderwidth, \metropolis@progressinheadfoot@linewidth);
  \end{tikzpicture}%
  \end{beamercolorbox}
}

% Redefine `progress bar in section page` to add border
\newlength{\metropolis@progressonsectionpage@borderwidth}
\setlength{\metropolis@progressonsectionpage@borderwidth}{2pt}
\setbeamertemplate{progress bar in section page}{
  \setlength{\metropolis@progressonsectionpage}{%
    \textwidth * \ratio{\insertframenumber pt}{\inserttotalframenumber pt}%
  }%
  \begin{tikzpicture}
    % Add blue progress bar border
    \fill[blue] (0,-\metropolis@progressonsectionpage@borderwidth) rectangle (\textwidth, \metropolis@progressonsectionpage@linewidth+\metropolis@progressonsectionpage@borderwidth);
    \fill[bg] (\metropolis@progressonsectionpage@borderwidth,0) rectangle (\textwidth-\metropolis@progressonsectionpage@borderwidth, \metropolis@progressonsectionpage@linewidth);
    \fill[fg] (\metropolis@progressonsectionpage@borderwidth,0) rectangle (\metropolis@progressonsectionpage-\metropolis@progressonsectionpage@borderwidth, \metropolis@progressonsectionpage@linewidth);
  \end{tikzpicture}%
}

\makeatother
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%



\title{Metropolis -- Modified}
\subtitle{A modern beamer theme}
% \date{\today}
\date{}
\author{Matthias Vogelgesang}
\institute{Center for modern beamer themes}
% \titlegraphic{\hfill\includegraphics[height=1.5cm]{logo.pdf}}


\begin{document}

\maketitle

\begin{frame}{First Frame}
    blah blah blah?
    \begin{itemize}
        \item blah blah blah.
        \item blah blah.
        \item yadda yadda yadda.
    \end{itemize}
\end{frame}

\begin{frame}{Second Frame}
    blah blah!
    \begin{enumerate}
        \item blah blah blah.
        \item blah blah.
        \item blah blah bah.
    \end{enumerate}
\end{frame}

\section{Test section}

\begin{frame}{Third Frame}
    blah blah!
    \begin{enumerate}
        \item blah blah blah.
        \item blah blah.
        \item blah blah bah.
    \end{enumerate}
\end{frame}

\end{document}