Using tikz with both tex4ht and pdflatex

Question

I found that in order to use tikz with tex4ht to produce HTML, I need to do the following:

\def\pgfsysdriver{pgfsys-tex4ht.def}
\usepackage{tikz}

I also need to produce PDF from the same tex file using pdflatex, but that gives me an error with the \def above.

Is there a way to exclude the def from pdflatex?

Answer 1

htlatex loads package tex4ht at the end of the class. Therefore \@ifpackageloaded can be used to detect TeX4ht. Inside a class tex4ht is not yet loaded if htlatex is used. Then TeX4ht can be detected via \HCode that is defined by htlatex.

\makeatletter
\@ifpackageloaded{tex4ht}{%
  \def\pgfsysdriver{pgfsys-tex4ht.def}%
}{%
  % only needed inside a class
  \begingroup\expandafter\expandafter\expandafter\endgroup
  \expandafter\ifx\csname HCode\endcsname\relax
  \else
    \def\pgfsysdriver{pgfsys-tex4ht.def}%
  \fi
}
\makeatother
\usepackage{tikz}