Include theorem name from thmtools into mdframed title box

Question

mdframed is nice for controlling the outer layout of theorems. thmtools on the other hand can take care of a number of other things great and small, in particular the detailed formatting of the title within the flow of text, but also stuff like maintaining a flexible list of theorems, properly setting autoref names, and so on. I know I can use the mdframed key to the \declaretheorem command to let it create a frame and control most aspects of that frame. What I'm missing, though, is a way to make use of the frametitle facilities of mdframed in this way.

Is there a way to redirect the title typesetting commands from thmtools into the frametitle argument to the mdframed environment it creates?

I see that I can add a hook before and a hook after the title, but at least my naive way of capturing the title between these two using \def\myframetitle\bgroup and \egroup failed:

\documentclass{article}
\usepackage{xcolor,tikz,geometry,amsthm,thmtools}
\usepackage[framemethod=TikZ]{mdframed}
\usepackage{thm-patch}% copied from thmdef-mdframed.sty
\makeatletter
\mdfdefinestyle{fstyle}{linecolor=blue,frametitlerule=true}
% The following was adapted from thmdef-mdframed.sty but does not work:
\define@key{thmdef}{mymdframed}[{}]{%
  \thmt@trytwice{}{%
    \addtotheorempreheadhook[\thmt@envname]{%
      \def\myframetitle\bgroup}%
    \addtotheorempostheadhook[\thmt@envname]{%
      \egroup\begin{mdframed}[frametitle=\myframetitle,#1]}%
    \addtotheorempostfoothook[\thmt@envname]{\end{mdframed}}%
    }%
}
% Change the mymdframed to mdframed to make this compile at all:
\declaretheoremstyle[mymdframed={style=fstyle}]{tstyle}
\declaretheorem[style=tstyle]{thm}
\begin{document}
\begin{thm}[Round] The world is round\end{thm}

And this is what it \emph{should} look like:
\begin{mdframed}[frametitle={Thm 1: Round},style=fstyle]
The world is round\end{mdframed}
\end{document}

I'll be happy to learn about any approach to get the two packages working together including the title. There must be some solution, e.g. by defining your own wrapper macros to handle the title argument, but I hope for some more elegant approaches from those who know more.

Answer 1

Let me try to provide an answer.

thmtools uses the default environment provided by amsthm. To use mdframed with frametitle you have to redefine the default environment of amsthm. However I don't know whether it's a good idea. With the simple test file below it works. Please note that all theorem environments are enclosed by mdframed.

In the example I also show how to modify the style of mdframed:

\setcounter{errorcontextlines}{999}
\documentclass{article}
\usepackage{xcolor,tikz,geometry,amsthm}
\usepackage{thmtools,thm-patch}% copied from thmdef-mdframed.sty
\usepackage[framemethod=TikZ]{mdframed}
\makeatletter

\def\@thm#1#2#3{%
%  \ifhmode\unskip\unskip\par\fi
  \normalfont
  \let\thmheadnl\relax
  \let\thm@swap\@gobble
  \thm@notefont{\fontseries\mddefault\upshape}%
  \thm@headpunct{.}% add period after heading
  \thm@headsep 5\p@ plus\p@ minus\p@\relax
  \thm@space@setup
  #1% style overrides
  \@topsep \thm@preskip               % used by thm head
  \@topsepadd \thm@postskip           % used by \@endparenv
  %
  \def\@tempa{#2}\ifx\@empty\@tempa
    \def\@tempa{\@oparg{\@begintheorem{#3}{}}[]}%
  \else
    \refstepcounter{#2}%
    \def\@tempa{\@oparg{\@begintheorem{#3}{\csname the#2\endcsname}}[]}%
  \fi
  \@tempa
}
\def\@begintheorem#1#2[#3]{%
    \mdframed[style=fstyle,frametitle={%
    \the\thm@headfont \thm@indent
    \@ifempty{#1}{\let\thmname\@gobble}{\let\thmname\@iden}%
    \@ifempty{#2}{\let\thmnumber\@gobble}{\let\thmnumber\@iden}%
    \@ifempty{#3}{\let\thmnote\@gobble}{\let\thmnote\@iden}%
    \thm@swap\swappedhead\thmhead{#1}{#2}{#3}%
    \the\thm@headpunct}]%
  }%

\def\@endtheorem{\endmdframed}
\makeatother


\mdfdefinestyle{fstyle}{linecolor=blue,frametitlerule=true,linewidth=2pt,}
\declaretheoremstyle[notefont=\itshape,preheadhook={\mdfapptodefinestyle{fstyle}{backgroundcolor=gray}}]{tstyle}
\declaretheorem[style=tstyle]{thm}
\begin{document}
\begin{thm}[Round] The world is round\end{thm}

And this is what it \emph{should} look like:

\begin{thm}The world is round\end{thm}


\end{document}