Avoid vertical space in absolutelynopagebreak environment

Question

I like the idea of absolutelynopagebreak environment and I'd like to use it for wrapping theorem-like environments when needed (without modifying those environments). It does work, but the problem is that it creates additional vertical space (before and after).

Is there a way to fix this?

\documentclass{article}
\newtheorem{theorem}{Theorem}
\newenvironment{absolutelynopagebreak}
  {\par\nobreak\vfil\penalty0\vfilneg
   \vtop\bgroup}
  {\par\xdef\tpd{\the\prevdepth}\egroup
   \prevdepth=\tpd}
\begin{document}
\begin{theorem}
Statement 001.
\end{theorem}
\begin{theorem}
Statement 002.
\end{theorem}
\begin{absolutelynopagebreak}
\begin{theorem}
Statement 003.
\end{theorem}
\end{absolutelynopagebreak}
\begin{theorem}
Statement 004.
\end{theorem}
\begin{theorem}
Statement 005.
\end{theorem}
\end{document}

I was able to remove vertical space using vspace (approximately), but it's not reliable since it changes when text size changes.

\begin{absolutelynopagebreak}
\vspace{-1.3\baselineskip}
\begin{theorem}
Statement 006.
\end{theorem}
\vspace{-0.65\baselineskip}
\end{absolutelynopagebreak}

Answer 1

Try this:

\documentclass{article}
\usepackage{amsthm} % For theorem environments
\newtheorem{theorem}{Theorem}
\makeatletter
\newenvironment{absolutelynopagebreak}
  {\par@nobreaktrue\nobreak\penalty0}
  {\par@nobreakfalse}
\makeatother
\begin{document}
\begin{theorem}
Statement 001.
\end{theorem}
\begin{theorem}
Statement 002.
\end{theorem}
\begin{absolutelynopagebreak}
\begin{theorem}
Statement 003.
\end{theorem}
\end{absolutelynopagebreak}
\begin{theorem}
Statement 004.
\end{theorem}
\begin{theorem}
Statement 005.
\end{theorem}
\end{document}

The environment uses \@nobreaktrue and \@nobreakfalse to manage the page breaking behavior. This is a more direct approach and should interfere less with the natural spacing. The \penalty0 command is used to discourage page breaks without inserting additional space.