Iterate over all defined PGF keys

Question

Is there a way to iterate over all PGF keys that have been defined previously? My idea is to capture the value of all keys in order to do Proper nesting of tikzpicture environments: Reset all PGF values to their defaults.

EDIT: I imagine something along these lines:

\documentclass{article}
\beginrecordallpgfkeys
\usepackage{tikz}
\endrecordallpgfkeys

\begin{document}
  \restoreallrecordedpgfkeys
\end{document}

I wouldn't mind if recording and restoring would use a temporary file.

Answer 1

There is no such feature (and it would be way too expensive).

If you need it, you have to record all options "in scope" manually (and you would need to define clearly what "in scope" means).

One way to record options might be the key filtering ability of pgfkeys (which is quite advanced, however).