pass to \geometry{} options using a macro - keyval error

Question

MWE:

\documentclass{article}
\usepackage{geometry}
\newcommand{\GeomOpts}{a4paper,vmargin={3cm,3cm}}
\geometry{\GeomOpts}
\begin{document}
\end{document}

Because of the braces in \GeomOpts its expansion fails when inserted as parameter to \geometry. I did read [1] and [2] but I didn't find a way to adapt this to my simpler \geometry case.

I did try with \expandafter before \geometry and before its braces. Also I did try with xparse's commands intented to define macros/command without success.

[1] Keyval Error with \includegraphics: options undefined

[2] Strip one level of braces for using keyval-value within nested keyval

Answer 1

You don't need this type of tricks. Options passed to the \geometry command are cumulative. So you can simply say

\geometry{a4paper,vmargin={3cm,3cm}

(which I think is your standard) and then add whatever adjustment you like in another \geometry command.

So, saying

\geometry{a4paper,vmargin={3cm,3cm}
\geometry{headheight=14.5pt}

is just the same as doing

\newcommand{\GeomOpts}{a4paper,vmargin={3cm,3cm}}
\expandafter\geometry\expandafter{\GeomOpts,headheight=14.5pt}

which I think was your aim. I don't see how

\newcommand{\GeomOpts}{a4paper,vmargin={3cm,3cm}}
\expandafter\geometry\expandafter{\GeomOpts}

is clearer than my suggestion above.