How to prevent linebreaks after hyphen if word starts with hyphen?

Question

(Remark: Maybe this is a typically German problem, I'm not sure in which other languages that might be relevant)

Sometimes there are words which start with a hyphen, as they are connected with a word used before, e. g. Werkstoffforschung und -entwicklung is a shorter (and I think more elegant) way to say Werkstoffforschung und Werkstoffentwicklung.

However, if the second word, which starts with the hyphen, is at the beginning of a new line, it can happen that the hyphen stays in the previous line and the word itself is the first one in the next line.

Minimal example:

\documentclass[11pt]{scrreprt}
\usepackage[ngerman]{babel}  
\begin{document}
Das ist ein Mustertext, der dazu da ist, um diese aa Textsatzproblematik
    bzw. -schwierigkeit zu demonstrieren 
\end{document}

(I hope that the example "works" for you to demonstrate the problem, when I typeset it with pdflatex, the "-" is at the end of the first line and the "schwierigkeit" is in the second one which is not wanted.)

Is there a smart* way to avoid that problem?
* pdflatex shall handle this automatically and "know" that a hyphen at the beginning of a word always has to stay connected to the word and shall not be separated from it.

Answer 1

UPDATE: babel v3.9, released in March 2013, introduces a set of \babelhyphen macros -- see section 1.6 of the manual for details. In particular, \babelhyphen{nobreak} (the non-starred version) provides a non-breakable hyphen which allows hyphenation in the rest of the word -- for the present question, this may be used to define a new shorthand which removes the need to look up allowed breakpoints. (Note: Sometimes, the first allowed breakpoint will be located three or less characters after the non-breakable hyphen; if you consider such a breakpoint as inadequate, use my original answer.)

\documentclass[11pt]{scrreprt}
\usepackage[ngerman]{babel}  
% The following requires babel v3.9 (released March 2013)
\defineshorthand[ngerman]{"+}{\babelhyphen{nobreak}}
\begin{document}
Das ist ein Mustertext, der dazu da ist, um diese aa Textsatzproblematik
    bzw. "+schwierigkeit zu demonstrieren 
\end{document}

ORIGINAL ANSWER: Use babel's "~ shorthand to add an explicit hyphen with prohibited line break; supplement this by using the "- shorthand to specify the first allowed follow-up breakpoint. (You will have to look up those with \showhyphens{Schwierigkeit}. See pp. 5--7 of the documentation of the german package for details and other shorthands. (Note: the babel shorthands originate from the german package, which is considered obsolete nowadays.)

By the way, using "~ but not "- in your example would produce an overfull hbox.

\documentclass[11pt]{scrreprt}
\usepackage[ngerman]{babel}  
\begin{document}
Das ist ein Mustertext, der dazu da ist, um diese aa Textsatzproblematik
    bzw. "~schwie"-rigkeit zu demonstrieren 
\end{document}

Answer 2

(Edited answer; my initial idea of redefining \- was bad; thanks to lockstep for pointing that out and for suggesting \declare@shorthand.)

Based on Ulrike's solution I came up with a version that does not have the side effect of disabling hyphenation at the - in "Arbeiter-Unfallversicherung"; you also won't have to specify the first allowed follow-up breakpoint (cf. lockstep's answer). I can't tell if it has other side effects. The drawback is that you'll have to type "_ to get a hyphen that disallows a linebreak after it.

\documentclass[11pt]{scrreprt}
\usepackage[ngerman]{babel}
\makeatletter
\declare@shorthand{ngerman}{"_}{\hyphenchar\font=-1 -\hyphenchar\font=`\-}
\makeatother
\begin{document}
Das ist ein Mustertext, der dazu dient, diese unsch"one Textsatzproblematik
bzw. "_schwierigkeit zu demonstrieren.
Im n"achsten Satz gibt es einen Test f"ur die Arbeiter-Unfallversicherung.
\end{document}

Note that this solution does not depend on T1-encoding.

Answer 3

You can use T1-encoding and set \hyphenchar to 127. But you must do it for all fonts, which in the end means that for you must correct the font definitions (here as an example the entries from T1cmr.fd:

\documentclass[11pt]{scrreprt}

\makeatletter
\providecommand{\EC@family}[5]{%
  \DeclareFontShape{#1}{#2}{#3}{#4}%
  {<5><6><7><8><9><10><10.95><12><14.4>%
   <17.28><20.74><24.88><29.86><35.83>genb*#5}{\hyphenchar\font=127}}
\DeclareFontFamily{T1}{cmr}{}
\EC@family{T1}{cmr}{m}{n}{ecrm}
\EC@family{T1}{cmr}{m}{sl}{ecsl}
\EC@family{T1}{cmr}{m}{it}{ecti}
\EC@family{T1}{cmr}{m}{sc}{eccc}
\EC@family{T1}{cmr}{bx}{n}{ecbx}
\EC@family{T1}{cmr}{b}{n}{ecrb}
\EC@family{T1}{cmr}{bx}{it}{ecbi}
\EC@family{T1}{cmr}{bx}{sl}{ecbl}
\EC@family{T1}{cmr}{bx}{sc}{ecxc}
\EC@family{T1}{cmr}{m}{ui}{ecui}
\makeatother
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\begin{document}

Das ist ein Mustertext, der dazu da ist, um diese aa Textsatzproblematik bzw. -schwierigkeit zu demonstrieren

\end{document}

Answer 4

Perhaps it's useful to think about breaking the line at this explicit hyphen in terms of how TeX looks at the issue.

According to the TeXbook at the bottom of pg. 96, hyphenating words at their explicit hyphen implies in a penalty given by \exhyphenpenalty, whose default is 50 (at least in plain TeX).

So forbidding breaks at the explicit hyphen with \exhyphenpenalty=10000 in the preamble of your document seems to me like the least effort solution. I tested here and it works with your MWE.