Bad SVG output when using htlatex

Question

I am trying to compile some minimal test.tex using htlatex test.tex "xhtml,svg", but the SVG generated from tikz pictures does not seem to work.

\documentclass[11pt]{article}

\usepackage{tikz}

\title{Testing}
\begin{document}

\maketitle

Inline equation \(X_1 + X_2 = Y\), equation
\[\int^{X \in \mathbf{C}} \mathbf{C}(X,X).
\]

Tikz picture.

\begin{tikzpicture}
  \draw [blue,fill] (0,0) rectangle (3,3);
  \draw [red,fill] (0,0) rectangle (3,2);
\end{tikzpicture}

\end{document}

The svg file for the tikz picture seems to be generated in a different way from the other SVGs (it has a different name scheme from the others, for instance), and it does not display due to the following error.

XML Parsing Error: mismatched tag. Expected: </g>.
Location: file:///home/mario/testing-htlatex/test-1.svg
Line Number 5, Column 3:
</p><g stroke="#000" fill="#000">

Indeed, removing that conflicting <p> makes the SVG display again. Is this a bug or am I missing something? Did I do something wrong that added that <p> to the tikz picture? Why is the tikz picture generated differently?

What puzzles me the most is that, if I decide to try without svg, using just htlatex test.tex, then a correct SVG for the tikz picture gets generated (!).

Answer 1

By default, TikZ uses special driver for TeX4ht to create the SVG file. It maps the low-level PGF command to SVG, so it doesn't use the mechanism TeX4ht uses for the conversion of LaTeX code to SVG. Sometimes this method fails. You can use the alternative TikZ driver for TeX4ht. It uses dvisvgm for the conversion to SVG. It results in better results in most cases (but there are cases where it fails completely). It seems to work nice for your example:

\documentclass[11pt]{article}

\ifdefined\HCode
   \def\pgfsysdriver{pgfsys-dvisvgm4ht.def}
\fi

\usepackage{tikz}

\title{Testing}
\begin{document}

\maketitle

Inline equation \(X_1 + X_2 = Y\), equation
\[\int^{X \in \mathbf{C}} \mathbf{C}(X,X).
\]

Tikz picture.

\begin{tikzpicture}
  \draw [blue,fill] (0,0) rectangle (3,3);
  \draw [red,fill] (0,0) rectangle (3,2);
\end{tikzpicture}

\end{document}

You may also want to use make4ht instead of htlatex. It fixes lot of issues that htlatex has and provides additional features.

This is the result when I compile your document using

make4ht filename.tex "svg"