Nesting tikzpictures, style inheritance and save box

Question

Throughout my document, I need a custom symbol, which I draw using TikZ. I have created a macro for it, so I do not need to copy the picture. I also need to use the symbol within other tikzpictures. The problem here is style inheritance: the style of the outer pictures must not interfere with the symbol produced by the macro.

The answers to this question and this question suggest to use a savebox to overcome this problem. I have tried to do this but, so far, have failed. Here is a minimal working example:

\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{automata, positioning}

\newsavebox{\blankbox}
\savebox{\blankbox}{\hspace{0.1ex}\tikz[baseline=0.1em]{%
    \node [shape=rectangle, anchor=south, draw, inner sep=0pt, minimum width=1ex, minimum height=0.9em] (char) {}}%
  \hspace{0.1ex}}

\begin{document}
  \begin{tikzpicture}[auto, shorten >=1pt, >=latex]
    \node[state] (0) {$\usebox{\blankbox}$};
    \node[state, dotted, right=1ex of 0] (1) {$\usebox{\blankbox}$};
  \end{tikzpicture}
\end{document}

and its output

As you can see, the style of the right node is inherited by the rectangle.

My question is: how can I fix this while still using the same macro everywhere?

Edit: In the comments Zarko suggests to change the line type in the inner picture manually. This obviously solves the problem in this specific example but what other properties do I need to set as well to "protect" the inner picture? I have tried some (like color, double, decoration, rotate) but (surprisingly to me) those aren't inherited. Does that mean that only dash pattern is inherited?

Answer 1

If you have the option of switching to another engine, XeTeX will behave as you wish.

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{automata, positioning}

\newsavebox{\blankbox}
\savebox{\blankbox}{\hspace{0.1ex}\tikz[baseline=0.1em]{%
    \node [shape=rectangle, anchor=south, draw, inner sep=0pt, minimum width=1ex, minimum height=0.9em] (char) {}}%
  \hspace{0.1ex}}

\begin{document}
  \begin{tikzpicture}[auto, shorten >=1pt, >=latex]
    \node[state] (0) {\usebox{\blankbox}};
    \node[state, dotted, right=1ex of 0] (1) {\usebox{\blankbox}};
  \end{tikzpicture}
\end{document}

Answer 2

You cannot. You cannot protect the inner picture by a box. You cannot protect the inner picture by .pic. You cannot protect the inner picture even you externalize it and then include it back.

In fact, you can Change color in finished pdf file.

@Heiko Oberdiek's answer shows that it is indeed a PDF feature to inherit everything. All you can do is to reset every parameters that potentially affects the inner picture.

Fortunately, there is a finite list of parameters and can be found in PDF specification. So good luck.