Is there a chance to get SyncTeX work with text within environments?

Question

I know that SyncTeX does not work correctly in Beamer (see Inverse PDF Search in beamer).

But there seems to be also a problem with inverse search in environments defined with \NewEnviron.

I want to call something like this:

\begin{foo}{x}{y}
bla bla
\end{foo}

It does not need to be an environment. But I do not know what to use else because I want to control the body which is possible with \BODY in \NewEnviron but not possible with \newenvironment.

So is it possible to define an environment-like thing, where SyncTeX points to the text in the environment and not at the end of the environment?

In itemize-environments it seems to work. Does someone know how it is implemented there?

Example:

\documentclass{letter}
\usepackage{environ}

\newif\ifshow

\NewEnviron{foo}[3]{
\ifshow
    #1\\
    \BODY
    -----------
\else
  Alert #1 #2 #3
\fi
}

\begin{document}
\begin{foo}{hide}{1}{2}
hidden Text
\end{foo}

\showtrue

\begin{foo}{show}{2}{1}
\begin{itemize}
    \item a
    \item b
    \item c
\end{itemize}
\end{foo}

\begin{itemize}
    \item d
    \item e
    \item f
\end{itemize}

\end{document}

For a, b, c inverse search does not work for d, e, f it works. For me it is important that the original text body can be replaced.

Answer 1

We can realize it with \newenvironment and \comment from verbatim:

\documentclass{letter}
\usepackage{verbatim}

\newif\ifshow

\newenvironment{foo}[3]{
 \ifshow
    #1\\
 \else
    \def\a{#1}
    \def\b{#2}
    \def\c{#3}
    \expandafter\comment
 \fi
}
{
 \ifshow
    -----------
 \else
    \expandafter\endcomment
    Alert \a~\b~\c
 \fi
}

\begin{document}
\begin{foo}{hide}{1}{2}
hidden Text
\end{foo}

\showtrue

\begin{foo}{show}{2}{1}
\begin{itemize}
    \item a
    \item b
    \item c
\end{itemize}
\end{foo}

\begin{itemize}
    \item d
    \item e
    \item f
\end{itemize}

\end{document}

Then inverse search does also work for a, b and c.