From c13b01f948b8fefef72737f58b8c24f8eb1453ad Mon Sep 17 00:00:00 2001
From: Matthias Vogelgesang <matthias.vogelgesang@kit.edu>
Date: Tue, 14 Feb 2017 09:49:01 +0100
Subject: [PATCH] Fix #260: check if TikZ external is loaded

---
 source/beamerthememetropolis.dtx | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/source/beamerthememetropolis.dtx b/source/beamerthememetropolis.dtx
index 6482f52..ba629e4 100644
--- a/source/beamerthememetropolis.dtx
+++ b/source/beamerthememetropolis.dtx
@@ -126,7 +126,15 @@
 }
 %    \end{macrocode}
 %
+% To avoid generating externalized figures of the progressbar we have to disable
+% them with ``tikzexternalenable'' and ``tikzexternaldisable''. However, if the
+% ``external'' libray is not loaded we would get undefined control sequence
+% problems, hence we define them as no-ops if they are not defined yet.
 %
+%    \begin{macrocode}
+\ifx\tikzexternalenable\undefined \newcommand{\tikzexternalenable}{} \fi
+\ifx\tikzexternaldisable\undefined \newcommand{\tikzexternaldisable}{} \fi
+%    \end{macrocode}
 %
 % \subsubsection{Component sub-packages}
 %