Random compile-time document style

Question

I am trying to create a document class with random style attributes, determined at compilation time. Random attributes would ideally include:

• Margins
• Line spacing
• Font selection

For my particular use case, in-document references are not typically useful/a design constraint, so there's no first-order need to worry about layout being consistent across compilations.

I attempted to use \pgfmathrandomitem in a new .cls file, as follows:

% randocls.cls
\LoadClass{article}
\usepackage{pgffor}

\pgfmathdeclarerandomlist{marginmargins}{{0.0}{0.25}{0.5}{0.75}}
\pgfmathrandomitem{\marginns}{marginmargins}

% none of the following work...
% (the implied margins are different; this is MWE so nbd)

% Case 1:
\usepackage[margin={\marginns}in]{geometry}

% Case 2:
% \addtolength{\topmargin}{{\marginns}in}

% Case 3:
% \let\rmarginns{\marginns}
% \addtolength{\topmargin}{{\rmarginns}in}

---

Under Case 1:

("C:\Program Files\MiKTeX 2.9\tex/latex/geometry\geometry.cfg")
! Missing number, treated as zero.
<to be read again> 
                   {
l.1007 \ProcessOptionsKV[p]{Gm}
                               %

Under Case 2:

! Missing number, treated as zero.
<to be read again> 
                   {
l.23 \addtolength{\topmargin}{{\marginns}in}

Under Case 3:

! LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.30 \let\rmarginns{\marginns
                             }

---

My best guess is that the problem relates to when pgfmathrandomitem can actually yield a random item, but I am in over my head. Is there a way to work around this, or another randomization mechanism that will allow randomization in the document header?

Answer 1

There is some issue with expansion and groups - this is always tricky in LaTeX. A solution here is to put the unit in the list:

% randocls.cls
\LoadClass{article}
\usepackage{pgffor}

\pgfmathdeclarerandomlist{marginmargins}{{0.0in}{0.25in}{0.5in}{0.75in}}
\pgfmathrandomitem{\marginns}{marginmargins}

% Case 1:
\usepackage[margin=\marginns]{geometry}

\documentclass{randocls}
\begin{document}
margin: \marginns
\end{document}