How can I know the default PGF line width?

Question

Is there some macro that will tell me what the default PGF line width is? I have tried creating my own macro by cloning \pgflinewidth before it has been modified, i.e.

\let\defaultlinewidth\pgflinewidth

but \defaultlinewidth seems to be affected by \pgfsetlinewidth anyway, and change to whatever \pgflinewidth is. So, the problem is that after I have called \pgfsetlinewidth, I don't know what the default pgf line width is anymore. Is there some way to get around this?

Answer 1

\pgflinewidth is a length. So you can use \setlength to copy its current value:

\documentclass{standalone}
\usepackage{tikz}
\newlength{\defaultpgflinewidth}
\setlength{\defaultpgflinewidth}{\pgflinewidth}
\begin{document}
\begin{tikzpicture}[line width=1mm]
  \draw circle [radius=1cm];
  \draw[line width=\defaultpgflinewidth] (-1cm,-1cm) rectangle (1cm,1cm);
\end{tikzpicture}
\end{document}

Edit (suggestion from Christian Feuersänger)

You can also use \edef to make a copy of the current representation of this length.

 \edef\defaultpgflinewidth{\the\pgflinewidth}

Answer 2

If you mean the standard line width, it's 0.4 pt or the setting thin.

\tikzstyle{ultra thin}=              [line width=0.1pt]
\tikzstyle{very thin}=               [line width=0.2pt]
\tikzstyle{thin}=                    [line width=0.4pt]
\tikzstyle{semithick}=               [line width=0.6pt]
\tikzstyle{thick}=                   [line width=0.8pt]
\tikzstyle{very thick}=              [line width=1.2pt]
\tikzstyle{ultra thick}=             [line width=1.6pt]

Answer 3

You can always query PGF directly:

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
\foreach \width [count=\yi] in {ultra thin,very thin,thin,semithick, thick, very thick, ultra thick}
  \node[\width] at (0,-0.5*\yi) {The value with the \texttt{\width} option is \the\pgflinewidth};
\end{tikzpicture}

\end{document}

In a similar way, you can define a command to keep the default value:

\documentclass{article}
\usepackage{tikz}

\newcommand\defvalue{%
  \tikz[baseline=-0.5ex]\node[line width=\pgflinewidth] {The default value is \the\pgflinewidth};}

\begin{document}

\begin{tikzpicture}
\pgfsetlinewidth{3pt}
\draw (0,3ex) -- (1,3ex);
\node at (6,3ex) {The current value is \the\pgflinewidth. \defvalue};
\pgfsetlinewidth{3mm}
\draw (0,-1cm) -- (1,-1cm);
\node at (6,-1cm) {The current value is \the\pgflinewidth. \defvalue};
\end{tikzpicture}

\end{document}