acmsmall class: linebreak in theorem headline

Question

I have a theorem in a acmsmall document where no linebreak in the headline occurs despite its length:

\documentclass[prodmode,acmtosn]{acmsmall}

\begin{document}
\begin{theorem}[long long long long long long long long long long long long long long long long long long long long long long long long long long title]
    content...
\end{theorem}
\end{document}

Its related to these questions: 1 2 but I guess that I'm obliged to use the builtin theorem setup and can't switch to amsthm or ntheorem.

Answer 1

Theorems are lists. The headlines are set through the optional argument of \item, and in your class actually in a \box. There won't break.

You can try to fake a suitable look by changing the behaviour for an empty optional argument. But imho it would be better to shorten the title.

\documentclass[prodmode,acmtosn]{acmsmall}
\makeatletter
\def\@opargbegintheorem#1#2#3{%
    \trivlist
    \item[\hskip 12pt
          \hskip \labelsep
          {\ifitalicenv{\scshape{#1}}\else{\itshape#1}\fi%
       \savebox\@tempboxa{\ifitalicenv{\scshape#3}\else{\itshape#3}\fi}%
       \ifdim\wd\@tempboxa>\z@%
           \ {\rmfamily #2}\unskip\hskip5pt\relax$($\box\@tempboxa$)$.%
       \else \ {\rmfamily #2}\unskip\hskip5pt\relax    
       \fi\unskip\hskip5pt}]
\ifitalicenv\itshape\else\upshape\fi\hskip-\labelsep}

\makeatother

\begin{document}
\begin{theorem}[blub]
    content...
\end{theorem}

\begin{theorem}[] {$($\scshape long long long long long long long long long long long long long long long long long long long long long long long long long long title$)$.\unskip\hskip5pt}
    content...
\end{theorem}
\end{document}