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The package hf-tikz is great for putting a frame around an equation. Although I am not absolutely sure there seems to be a "new" error massage when using this package: "Missing character: There is no ; in font nullfont!"

I stripped my complex beamer-file down to actually a minimal LaTeX-file which also gives the error message:

\documentclass{article}
\usepackage{hf-tikz}
% \font\nullfont=cmr10
\begin{document}
\begin{displaymath}
  \tikzmarkin{eq}
  c^2 = a^2+b^2
  \tikzmarkend{eq}
\end{displaymath}
\end{document}

The resulting PDF-file is ok with no errors, but the error message makes me a bit nervous because the question is always what happens after the next update? My system is a MINT Linux 21.1 with an underlying Ubuntu 22.04 and a full installation of Texlive 2022.

If I uncomment the line "% \font\nullfont=cmr10" a semicolon appears at the end of the coloured box. From other postings about the "Missing character..." error message I learned that setting the nullfont to a visible font allows to find the error in the underlying LaTeX code. It seems that there is an error in the package hf-tikz or that the syntax of tikz has changed a little bit and the older package hf-tikz has not been adapted to these changes.

Any idea how to overcome the problem?

1 Answer 1

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In this case the message is harmless. It was always in the log but appears now also on the terminal because \tracinglostchars has been set to 2 in a current LaTeX.

But it would be better if hf-tikz would avoid it by delimiting the \tikz arguments by braces instead of using the semicolon syntax, as with it there is always the danger to end up with one stray semicolon too much:

\documentclass{article}
\usepackage{hf-tikz}

\renewcommand\tikzmarkend[2][]{%
\tikz[remember picture with id=#2]{#1}} %{#1} instead of #1;

\begin{document}

\begin{displaymath}
 \tikzmarkin{eq}
 c^2 = a^2+b^2
 \tikzmarkend{eq}
\end{displaymath}

\end{document}
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  • Thanks for the fast & complete answer! It seems that hf-tikz needs some care but since the latest version is almost ten years old it is in question if the package is still being maintained?
    – JeBa
    Mar 31, 2023 at 9:18
  • no idea, write to the author and look what happens. Mar 31, 2023 at 9:22
  • Already did that after your answer:-) -- let's see if the author is still active
    – JeBa
    Mar 31, 2023 at 10:04
  • Nice guy, he already answered and will take a closer look at the problem in the next days / weeks :-)
    – JeBa
    Apr 5, 2023 at 9:21

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