% Define \SXtitle to lift \SSubtitle out:
\def\SXtitle#1{\title{\let\SSubtitle\SSubtitleDrop#1}\SExtractSubtitle#1\SExtractSubtitleDone}
\def\SSubtitleDrop#1{}
\def\SExtractSubtitleDone {}
\def\SExtractSubtitle{\futurelet\next\SExtractSubtitleX}
\def\SExtractSubtitleX#1{\ifx{#1}\SSubtitle \let\Snext\SWithSubtitle \else \let\Snext\SExtractSubtitleY \fi \Snext}
\def\SExtractSubtitleY{\ifx\next\SExtractSubtitleDone \let\Snext\relax \else \let\Snext\SExtractSubtitle \fi \Snext}
\def\SWithSubtitle#1{\subtitle{#1}\SExtractSubtitle}

\renewcommand{\titleAndVersionAndAuthors}[3]{\SXtitle{#1}#3\maketitle}
\renewcommand{\titleAndEmptyVersionAndAuthors}[3]{\titleAndVersionAndAuthors{#1}{#2}{#3}}
\renewcommand{\titleAndVersionAndEmptyAuthors}[3]{\SXtitle{#1}\authorinfo{Anonymous}{}{}\maketitle}
\renewcommand{\titleAndEmptyVersionAndEmptyAuthors}[3]{\titleAndVersionAndEmptyAuthors{#1}{#2}{#3}}

% Support plain `author' while enabling `authorinfo': for each
% use of \SAuthor, check whether it contains an \SAuthorinfo form:
\def\SAuthor#1{\SAutoAuthor#1\SAutoAuthorDone{#1}}
\def\SAutoAuthorDone#1{}
\def\SAutoAuthor{\futurelet\next\SAutoAuthorX}
\def\SAutoAuthorX{\ifx\next\SAuthorinfo \let\Snext\relax \else \let\Snext\SToAuthorDone \fi \Snext}
\def\SToAuthorDone{\futurelet\next\SToAuthorDoneX}
\def\SToAuthorDoneX#1{\ifx\next\SAutoAuthorDone \let\Snext\SAddAuthorInfo \else \let\Snext\SToAuthorDone \fi \Snext}
\newcommand{\SAddAuthorInfo}[1]{\authorinfo{#1}{}{}}

\renewcommand{\SAuthorinfo}[3]{\authorinfo{#1}{#2}{#3}}
\renewcommand{\SAuthorSep}[1]{}

\renewcommand{\SConferenceInfo}[2]{\conferenceinfo{#1}{#2}}
\renewcommand{\SCopyrightYear}[1]{\copyrightyear{#1}}
\renewcommand{\SCopyrightData}[1]{\copyrightdata{#1}}
\renewcommand{\Sdoi}[1]{\doi{#1}}
\renewcommand{\SPexclusivelicense}[0]{\exclusivelicense}

\renewcommand{\SCategory}[3]{\category{#1}{#2}{#3}}
\renewcommand{\SCategoryPlus}[4]{\category{#1}{#2}{#3}[#4]}
\renewcommand{\STerms}[1]{\terms{#1}}
\renewcommand{\SKeywords}[1]{\keywords{#1}}

% A later \doi will replace this one:
\doi{}