Automatically start a new line at the beginning of a proof environment?

Question

I use amsmath to provide the proof environment. However, if a itemize (or tikzpicture) environment immediately follows the proof environment, xelatex will produce a messy result:

\begin{proof}
\begin{itemize}
\item 1
\item 2
\end{itemize}
\end{proof}

Will produce something like this:

Proof. * 1

• 2

So I have to manually add a \mbox after the proof env. Is it possible to make proof automatically add a newline in these situations?

Answer 1

You can redefine the proof environment and add a \mbox:

\documentclass[a5paper]{article}
\usepackage{amsmath,amsthm}
\makeatletter
\renewenvironment{proof}[1][\proofname]{\par
  \pushQED{\qed}%
  \normalfont \topsep6\p@\@plus6\p@\relax
  \trivlist
  \item[\hskip\labelsep
        \itshape
    #1\@addpunct{.}]\mbox{}\ignorespaces
}{%
  \popQED\endtrivlist\@endpefalse
}
\makeatother
\begin{document}
\begin{proof}
\begin{itemize}
\item 1
\item 2
\end{itemize}
\end{proof}
\end{document}