%% 
%%  Ein Beispiel der DANTE-Edition
%%  
%%  1. Auflage
%% 
%% 
%%  Copyright (C) 2013 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\setlength\parindent{0pt}
\usepackage[ngerman]{babel}
%StartShownPreambleCommands
\usepackage{luacode}
\begin{luacode*}
function markNode(color)
 local w=node.new("whatsit","pdf_literal")
 w.data=string.format("q "..color.."RG 2 w 0 -0.1 m 0 10 l S Q")
 return w
end
function markList(List)
 for n in node.traverse(List) do
  if n.id==1 then markList(List.head)
  elseif n.id==0 then  -- Zeilenanfang gefunden
    n.head=node.insert_before(
           n.head, n.head, markNode("1 0 0"))
  end
 end
 return true
end
\end{luacode*}
%StopShownPreambleCommands
\begin{document}
\parbox{5cm}{%
\directlua{luatexbase.add_to_callback("post_linebreak_filter",markList,"markList")}%
Jetzt soll \hbox{hier ein} langer Text angegeben werden, dessen Knotenliste wir
betrachten.\par
Rot: Zeilenanfang\par
Grun: Wortende\par
Blau: Absatzende}
\directlua{luatexbase.remove_from_callback("post_linebreak_filter","markList")}
\end{document}