Q:

mdframed+tikz to display overfullrule

This may or may not be a bug, so I'll first ask it here before reporting.
In the following test case:
\documentclass{article}
\usepackage[framemethod=tikz]{mdframed}

\overfullrule=5pt

\def\sentence{%
  to be the morphism from $\delta^*$ to $(\delta')^*$ (resp.\ to
  $(\delta'')^*$) such that $h'((p', p'')a(q', q''))$}

\begin{document}

\begin{mdframed}[hidealllines=true]
  \sentence
\end{mdframed}

\begin{mdframed}[rightline=false,topline=false]
  \sentence
\end{mdframed}

\end{document}

the overfullrule is drawn only in the first mdframed.  How can I make it work
in the second one too?  This silent ignoring of overfullrule can be really dangerous...
Thanks!

TeXlive 2012.26892-2 on Arch Linux
latest mdframed from GitHub (1.6c, mdframed.dtx 436 2012-06-23 09:49:13Z marco)

A:

This question lead to the new option draft which is now implement in the development branch. 
https://github.com/marcodaniel/mdframed

The contents of the environment mdframed is saved in a savebox. The output, if you use framemethod=tikz, will be done by the environment tikzpicture. To allow the options of three different lines I must work with the command \clip provided by tikz which also clips the overfull boxes. 
If you use the option hidealllines=true there is nothing to clip which results in the output of overfull boxes. 
To show the overfull markers you can do the following:
\makeatletter
\renewrobustcmd*\mdf@tikzbox@tfl[1]{%three or four borders
    %\clip
    \path(0,0)rectangle(\mdfboundingboxwidth,\mdfboundingboxheight);%
    \begin{scope}[mdfcorners]%
       \clip[preaction=mdfouterline]%
            [postaction=mdfbackground]%
            [postaction=mdfinnerline]#1;%
    \end{scope}%
    \path[mdfmiddleline,mdfcorners]#1;
  }%

\renewrobustcmd*\mdf@tikzbox@otl[2]{%one or two borders
    %\clip
    \path(0,0)rectangle(\mdfboundingboxwidth,\mdfboundingboxheight);%
    \begin{scope}
       \path[mdfouterline,mdfcorners]#1;%
       \clip[postaction=mdfbackground]#2;%
       \path[mdfinnerline,mdfcorners]#1;%
    \end{scope}%
    \path[mdfmiddleline,mdfcorners]#1;}%
\makeatother

