unicode is great!

tex/main.tex

@@ -12,6 +12,7 @@
 \textinput{whitespace\de}
 \textinput{paragraph\de}
 \textinput{mathmode\de}
+\textinput{unicode\de}
 \textinput{operatorname\de}
 \textinput{references\de}
 \docEnd

tex/mathmode.tex

@@ -162,4 +162,9 @@ Look at the code for an example.
 Since in aligned environments \lstinline|\overset| can always be used
 and \lstinline|\stackrel| only for one-symbol explanations \lstinline|\overset|
 together with \lstinline|aligned-overset| is to be preferred.
+
+\subsection{Find the right command}
+If you do not know what a makro is called, use the website
+\url{http://detexify.kirelabs.org/classify.html}.
+Also consider using unicode, see section \ref{sec:unicode}.
 \docEnd

tex/unicode.tex

@@ -0,0 +1,56 @@
+%! TEX program = lualatex
+
+\input{.maindir/tex/header/preamble-section}
+% inputs the preamble only if necessary
+\docStart
+\section{Lua\texorpdfstring{\LaTeX}{LaTeX} and Unicode}\label{sec:unicode}
+Plain text files like \TeX-source files are written using an encoding that tells the computer how to translate bytes into letters.
+There are hundreds of encodings developed over the years but nowadays there is only one that makes any sense to use: UTF-8, one form of unicode.
+In order to use UTF-8 in \LaTeX-documents compiled with \lstinline!pdflatex! one needs the line \lstinline!\usepackage[utf8]{inputenc}!.
+In the more modern compilers Lua\LaTeX{} (and Xe\LaTeX{}%
+\footnote{I am not familiar with Xe\LaTeX, so I will only refer to Lua\LaTeX.}
+UTF-8 is the standard (and only possible (?)) encoding.
+Lua\LaTeX{} supports UTF-8 far better than pdf\LaTeX{}.
+That means that you can use any UTF-8 symbol in the code and it is used.
+With one limitation: the font you use must include it.
+The font is set with the package \lstinline!fontspec!.
+
+I use in my template the following fonts which have a quite wide support of the unicode ranges I have used to far:
+\begin{lstlisting}
+\usePackage{fontspec}
+% Standard fonts that work, can be overwritten
+\setmainfont{DejaVu Serif}
+\setsansfont{DejaVu Sans}
+\setmonofont{DejaVu Sans Mono}
+\end{lstlisting}
+
+For setting the mathematics font you can use
+\begin{lstlisting}
+\usePackage{unicode-math}
+\setmathfont{TeX Gyre DejaVu Math}
+\end{lstlisting}
+but I could not see any visual difference when adding those lines.
+
+The important question now is: how to input the UTF-8 symbols.
+I use the Neo2 keyboard layout%
+\footnote{\url{https://neo-layout.org}} which already includes a lot
+of symbols like greek letters and mathematical logic operators.
+If you want to keep qwertz, there is also qwertz-neo which combines
+qwertz with the other symbols from Neo2.
+Additionally there is a feature in Linux called the \enquote{Compose} key
+which allows you to type a sequence of keys to get an Unicode character.
+You can configure it with a file \lstinline!~/.XCompose!.
+For Windows there are programs that supply similar functionality.
+For details search the web for \enquote{Compose key}, \enquote{.XCompose mathematical symbols}, etc.
+This allows to have \LaTeX-code that has mathematical formulas that are closer to the pdf output and shorter: \lstinline!$\sin α + \sin β + Σ_{ι=1}^3 λ_ι = Π_{κ = 1}^5 𝒫_κ$!.
+
+Note that sometimes you might want to give unicode characters a different meaning than they originally have. In my case \lstinline!Σ! is the sum symbol, not the greek capital letter Sigma. Hence I have in my template:
+\begin{lstlisting}
+\RequirePackage{newunicodechar}       % makes this remapping possible
+\newunicodechar{Σ}{\ensuremath{\sum}} % not capital sigma which is smaller!
+\end{lstlisting}
+It is debatable though if that is a good idea since there is also a sum symbol in UTF-8: \href{https://unicode-table.com/en/2211/}{∑}.
+
+You can find unicode characters on the website \url{https://unicode-table.com}.
+If you know what you want, but do not know how it is called, the website \url{http://shapecatcher.com/} might be helpful.
+\docEnd

tex/unicode_de.tex

@@ -0,0 +1,7 @@
+%! TEX program = lualatex
+
+\input{.maindir/tex/header/preamble-section}
+% inputs the preamble only if necessary
+\docStart
+\textinput{unicode}
+\docEnd