Release Version v1.0 "refcard" Class (#1)

* First version of the class "refcard"

CONTRIBUTORS

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+The current Maintainer is Martin C Schwarzer (polyluxus@gmail.com).
+
+This class is mainly based on the Tex - Latex Stack Exchange question and answer:
+
+  Document Class for Reference Cards (https://tex.stackexchange.com/q/99765/33413).
+
+It contains contributions from:
+
+ - Mike Renfro (https://tex.stackexchange.com/users/3345; https://github.com/mikerenfro)
+ - Sean Allred (https://tex.stackexchange.com/users/17423; https://github.com/vermiculus)
+ - Eric Berquist (https://github.com/berquist)
+
+Other code has also been imported into this repository. 
+This is also highlighted in the commented source code.
+
+ - Part of the code is adapted from the answer of Werner (https://tex.stackexchange.com/users/5764):
+   How to create a command with key values? (https://tex.stackexchange.com/a/34314/33413)
+
+ - The automatically adjusting label width is based on the answers by user121799 (no stack exchange profile page)
+   and Gonzalo Medina (https://tex.stackexchange.com/users/3954)
+   Why conflict between mathtools and Gonzalo's solution for auto-adjusting description environment?
+   (https://tex.stackexchange.com/q/461056/33413)
+   Automatically set description list `labelwidth` based on widest label?
+   (https://tex.stackexchange.com/q/130097/33413)
+
+ - Expansion of column types in array tables is  based on the code provided by Bruno Le Floch
+   (https://tex.stackexchange.com/users/2707).
+   How do I expand a macro into a tabular head? (https://tex.stackexchange.com/a/14460/33413)
+

README.markdown

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+# refcard
+
+A reference card class for LaTeX2e.
+
+According to [Wikipedia](https://en.wikipedia.org/wiki/Cheat_sheet), 
+a cheat sheet is a concise set of notes used for quick reference.
+Some might even call it a [reference card or sheet](https://en.wikipedia.org/wiki/Reference_card), 
+hence the name.
+
+This small class is aimed to make the typesetting of 
+reference cards a bit less tedious, so you can focus on using them.
+The class is inspired from the question and answer 
+[Document Class for Reference Cards](https://tex.stackexchange.com/q/99765).
+
+Since `refcard` is based on `article` most options can be passed on.
+
+## Additional Options
+
+  * `columns=<num>`    How many columns, default is 3.
+  * `margin=<length>` Passed to `geometry`, default 1 cm.
+
+## Disabled Options
+
+  * `portrait`   only supports `landscape`; ignored, warning.
+  * `titlepage`  saving space, so no title page; ignored, warning.
+  * `twocolumn`  class uses `multicol`; break, error.
+
+## Features
+
+  * Dense settings to save maximum space.
+  * No enumeration of (sub)sections.
+  * Customised itemise environments.
+
+## Acknowledgements
+
+Thanks to the following people, who have contributed to the
+original implementation:
+
+ - Mike Renfro ([Mike Renfro](https://tex.stackexchange.com/users/3345),
+  [mikerenfro](https://github.com/mikerenfro));
+ - Sean Allred ([Sean Allred](https://tex.stackexchange.com/users/17423),
+  [vermiculus](https://github.com/vermiculus));
+ - Eric Berquist, ([berquist](https://github.com/berquist)).
+
+Currently maintained by Martin C Schwarzer ([Martin-マーチン](https://chemistry.stackexchange.com/users/4945),
+  [polyluxus](https://github.com/polyluxus)).
+
+
+Other code has also been imported into this repository. 
+This is also highlighted in the commented source code.
+
+ - Part of the code is adapted from the answer of Werner ([Werner](https://tex.stackexchange.com/users/5764)):
+   [How to create a command with key values?](https://tex.stackexchange.com/a/34314/33413)
+
+ - The automatically adjusting label width is based on the answers by user121799 (no stack exchange profile page)
+   and Gonzalo Medina ([Gonzalo Medina](https://tex.stackexchange.com/users/3954)):
+   - [Why conflict between mathtools and Gonzalo's solution for auto-adjusting description environment?](https://tex.stackexchange.com/q/461056/33413)
+   - [Automatically set description list `labelwidth` based on widest label?](https://tex.stackexchange.com/q/130097/33413)
+
+ - Expansion of column types in array tables is based on the code provided by Bruno Le Floch
+   ([Bruno Le Floch](https://tex.stackexchange.com/users/2707)):
+   [How do I expand a macro into a tabular head?](https://tex.stackexchange.com/a/14460/33413)
+
+## License
+
+The class is licensed [CC-BY-SA 4.0](LICENSE.markdown).
+

demo/documentation.tex

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+\documentclass[   % inherits article
+  final,          % or
+  % draft,
+  a4paper,        % or
+  % letterpaper   % (etc. pp.)
+  % portrait,       % WILL PRODUCE WARNING
+  columns=3,       % this is the default
+  margin=1.0cm,   % default, or
+  % margin=0.5in, % default
+  % titlepage,      % WILL PRODUCE WARNING
+  % twocolumn     % WOULD PRODUCE ERROR
+]{refcard}
+
+%
+% Adapted from https://tex.stackexchange.com/a/99784.
+%
+
+% Fonts declaration
+\usepackage[T1]{fontenc}
+\usepackage[utf8]{inputenc}
+\usepackage{libertine}
+
+% language
+
+\usepackage[english]{babel}
+\usepackage{csquotes}
+
+% spacing for the letter
+\usepackage{setspace}
+% Typesetting code prettier
+\usepackage[dvipsnames]{xcolor}
+\definecolor{lightgray}{gray}{0.95}
+\usepackage{listings}
+\lstdefinestyle{mytex}{
+  language=[LaTeX]TeX,%
+  backgroundcolor=\color{lightgray},%
+  basicstyle=\footnotesize\ttfamily,%
+  keywordstyle=\bfseries,%
+  breaklines=true,%
+  morekeywords={part,chapter,subsection,subsubsection,paragraph,subparagraph}%
+}
+
+\lstset{style=mytex}
+
+% Symbols for SE and GH
+\usepackage{fontawesome} 
+% Symbols for creative commons
+\usepackage{ccicons}
+% linking to the outside world
+\usepackage{hyperref}
+
+% Please no font errors
+% https://tex.stackexchange.com/a/9366/33413
+\newcommand\mybackslash{\char`\\}
+
+% What this is about
+\title{Cheat sheet on \texttt{refcard}}
+\author{Version 1.0} % I know, horrible abuse
+\date{2020/01/18}
+
+\begin{document}
+\maketitle
+
+\section{Introduction}
+
+According to \href{https://en.wikipedia.org/wiki/Cheat_sheet}{Wikipedia}, 
+a cheat sheet is a concise set of notes used for quick reference.
+Some might even call it a \href{https://en.wikipedia.org/wiki/Reference_card}{reference sheet}, 
+hence the name.
+In lieu of a proper documentation, we provide herewith a 
+reference sheet for the document class \lstinline`refcard`.
+
+This small class is aimed to make the typesetting of 
+reference sheets a bit less tedious, so you can focus on using them.
+The class is inspired from the question and answer 
+\faStackExchange~\href{https://tex.stackexchange.com/q/99765}{Document Class for Reference Cards}.
+
+Since \lstinline`refcard` is based on \lstinline`article` most options can be passed on.
+
+\section{Additional Options}
+
+\begin{refcardtable}[envcolumns=2,cellalign=l]
+  \lstinline`columns=<num>`   & How many columns, default is 3.\\
+  \lstinline`margin=<length>` & Passed to \lstinline`geometry`, default 1~cm.
+\end{refcardtable}
+
+\section{Disabled Options}
+
+\begin{refcardtable}
+  \lstinline`portrait`  & only supports \lstinline`landscape`; ignored, warning.\\
+  \lstinline`titlepage` & saving space, so no title page; ignored, warning.\\
+  \lstinline`twocolumn` & class uses \lstinline`multicol`; break, error.\\
+\end{refcardtable}
+
+\section{Features}
+
+\begin{itemize}
+\item Dense settings to save maximum space.
+\item No enumeration of \lstinline`(sub)section`s.
+\item Customised itemise environments.
+\end{itemize}
+
+\section{Environments}
+
+\subsection{Description based environments}
+
+The environment \lstinline`refcardlist` is a description based list,
+which means that the item is a string, for example to use as a command.
+It automatically adjusts the width of the label to the longest one.
+The label can be formatted by specifying \lstinline`labelfont=<command>`.
+
+For example:
+\begin{refcardlist}[labelfont=\ttfamily]
+  \item[Short]         text text text
+  \item[A long label]  text text text
+  \item[Shorter]       text text text
+\end{refcardlist}
+
+\begin{lstlisting}
+\begin{refcardlist}[labelfont=\ttfamily]
+  \item[Short]         text text text
+  \item[A long label]  text text text
+  \item[Shorter]       text text text
+\end{refcardlist}
+\end{lstlisting}
+
+\subsection{Inline description list}
+
+With the environment \lstinline`refcardinline` the list will be
+set as a single paragraph.
+The label can be formatted by specifying \lstinline`labelfont=<command>`.
+Items are joined by a semicolon (;) and the list is closed with a full stop (.).
+
+For example: 
+\begin{refcardinline}[labelfont=\itshape]
+\item[Short]         text text text 
+\item[A long label]  text text text 
+\item[Shorter]       text text text 
+\end{refcardinline}
+
+\begin{lstlisting}
+\begin{refcardinline}[labelfont=\itshape]
+\item[Short]         text text text 
+\item[A long label]  text text text 
+\item[Shorter]       text text text 
+\end{refcardinline}
+\end{lstlisting}
+
+\subsection{Column assorted list}
+
+The environment \lstinline`refcardcolumnlist` provides access to a list, 
+which is set in multiple columns.
+The number of columns can be given as an optional argument,
+in the form \lstinline`envcolumns=<INT>`
+the default is to use two.
+
+\begin{refcardcolumnlist}[envcolumns=5]
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\end{refcardcolumnlist}
+
+\begin{lstlisting}
+\begin{refcardcolumnlist}
+\begin{rscolslist}[envcolumns=5]
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\item text
+\end{refcardcolumnlist}
+\end{lstlisting}
+
+\subsection{Verbatim Code Fragments}
+
+While it is often desired for these cheat sheets, it is not easily implemented.
+For the time being, there is an environment which accepts \textquote{code}: 
+\lstinline`refcardverblist`.
+
+\begin{refcardverblist}[envcolumns=3]
+    \item[\( \times   \)] \lstinline|\times| 
+    \item[\( \infty   \)] \lstinline|\infty| 
+    \item[\( \supset  \)] \lstinline|\supset|
+    \item[\( \alpha   \)] \lstinline|\alpha| 
+    \item[\( \epsilon \)] \lstinline|\epsilon|
+\end{refcardverblist}
+
+\begin{lstlisting}
+\begin{refcardverblist}[envcolumns=3]
+    \item[\( \times   \)] \lstinline|\times| 
+    \item[\( \infty   \)] \lstinline|\infty| 
+    \item[\( \supset  \)] \lstinline|\supset|
+    \item[\( \alpha   \)] \lstinline|\alpha| 
+    \item[\( \epsilon \)] \lstinline|\epsilon|
+\end{refcardverblist}
+\end{lstlisting}
+
+It is (currently) not possible to use  the verbatim string as a label.
+If this is desired, switch to a tabular based environment, which is described below.
+
+\subsection{Table based environments}
+
+The table based environments use the \lstinline`tabularx` package,
+where the row of the table will fill the whole line.
+
+The first one is \lstinline`refcardtable`.
+The number of columns can be changed in the optional argument, but defaults to two, 
+e.g. \lstinline`envcolumns=<INT>`. The alignment of the columns can be changed
+with \lstinline`cellalign=<r|l|c|X>`.
+The last column, however, is special, because it is used to balance the table and 
+therefore the column type is fixed as \lstinline`X`.
+
+As mentioned before, strings to be handled verbatim can be placed in this environment,
+see row 3
+
+\begin{refcardtable}[envcolumns=3,cellalign=c]
+  \hline
+  Short               & 1 & text text text\\
+  A long label        & 2 & text text text\\
+  \lstinline|Shorter| & 3 & %
+    text \lstinline|text| text\\\hline
+\end{refcardtable}
+
+\begin{lstlisting}
+\begin{refcardtable}[envcolumns=3,cellalign=c]
+  \hline
+  Short               & 1 & text text text\\
+  A long label        & 2 & text text text\\
+  \lstinline|Shorter| & 3 & %
+    text \lstinline|text| text\\\hline
+\end{refcardtable}
+\end{lstlisting}
+
+
+
+The second one is meant to be used for maths notation,
+called \lstinline`rsmathtable`, which has no argument.
+The first column is set in display style maths mode and 
+will be fitted to the widest entry.
+The second column is meant for the description and 
+like the table before, the type is fixed as \lstinline`X`.
+
+\begin{refcardmathtable}
+  pV = nRT                     & Ideal gas law \\
+  0 = e^{i\pi} + 1             & Euler's identity \\
+  \log(MN) = \log(M) + \log(N) & %
+    Logarithm addition rule\\
+\end{refcardmathtable}
+
+
+\begin{lstlisting}
+\begin{refcardmathtable}
+  pV = nRT                     & Ideal gas law \\
+  0 = e^{i\pi} + 1             & Euler's identity \\
+  \log(MN) = \log(M) + \log(N) & %
+    Logarithm addition rule\\
+\end{refcardmathtable}
+\end{lstlisting}
+
+\section{Acknowledgments}
+
+Thanks to the following people, who have contributed to the original implementation:
+\begin{refcardinline}
+\item[Mike Renfro] %
+  \href{https://tex.stackexchange.com/users/3345}{\faStackExchange}
+  \href{https://github.com/mikerenfro}{\faGithub}
+\item[Sean Allred]
+  \href{https://tex.stackexchange.com/users/17423}{\faStackExchange}
+  \href{https://github.com/vermiculus}{\faGithub}
+\item[Eric Berquist] 
+  \href{https://github.com/berquist}{\faGithub}
+\item[] please see the manual for a full list.
+\end{refcardinline}
+
+Currently maintained by Martin C Schwarzer \href{https://chemistry.stackexchange.com/users/4945}{\faStackExchange}
+  \href{https://github.com/polyluxus}{\faGithub}.
+
+The class and the document are licensed \ccbysa.
+
+\end{document}