Cfrgtkky

With beamer frames, this does not work.

newenvironment{itemframe}[1]{

  begin{frame}{#1}

    begin{itemize}

}{

    end{itemize}

  end{frame}

}

Adding fragile, environment=itemframe as an optional argument to the frame will solve the issue. But there is also an alternative that avoids making the frame fragile: Exporting everything apart from the frame environments to own commands.

documentclass{beamer}

usepackage{xparse}



newenvironment{itemframe}[1]{

%NewDocumentEnvironment{itemframe}{m}{

  begin{frame}{#1}

    itemframebegin

}{

    itemframeend

  end{frame}

}

newcommanditemframebegin{

  begin{itemize}

}

newcommanditemframeend{

  end{itemize}

}



begin{document}

begin{itemframe}{Title}

  item A

  item B

  item C

end{itemframe}

end{document}

Now when newenvironment is replaced with NewDocumentEnvironment from the xparse package, as shown as a comment above, both solutions again fail with

! File ended while scanning use of beamer@collect@@body.

Is there a possibility to make a NewDocumentEnvironment including a frame? Avoiding the fragile option is preferred.

Unfortunately, xparse defined environments play bad with beamer@collect@@body.

A workaround is using environ:

documentclass{beamer}

usepackage{xparse,environ}



NewEnviron{itemframe}{expandafterdoitemframeBODYENDBODY}

NewDocumentCommand{doitemframe}{mo u{ENDBODY}}{%

  begin{frame}{#1}

  IfNoValueTF{#2}{NO OPT}{OPT}

  begin{itemize}

  #3

  end{itemize}

  end{frame}

}



begin{document}

begin{itemframe}{Title}[opt]

  item A

  item B

  item C

end{itemframe}

end{document}

The argument list is ended by u{ENDBODY} so that doitemframe collects the arguments in the proper way and then you can use #3 (or whatever is the resulting argument number).

If you don't need the full force of xparse but just standard arguments, you can do

NewEnviron{itemframe}[1]{%

  begin{frame}{#1}

  begin{itemize}

  BODY

  end{itemize}

  end{frame}

}

With xparse release 2019-05-03 one can do as follows: +b denotes that the body of the environment will be collected (in this case as #3) before processing further.

documentclass{beamer}

usepackage{xparse}



NewDocumentEnvironment{itemframe}{mo+b}

 {%

  begin{frame}{#1}

  IfNoValueTF{#2}{NO OPT}{OPT: #2}

  begin{itemize}

  #3

  end{itemize}

  end{frame}

 }{}



begin{document}

begin{itemframe}{Title}[opt]

  item A

  item B

  item C

end{itemframe}

end{document}