纠正框架定理的格式

Question

我一直在使用下面的代码来为我的定理（和其他类似定理的环境）创建悬垂。

\documentclass{article}

\usepackage{amsthm}
\usepackage{mdframed}

\newlength{\marginlabelsep}\setlength{\marginlabelsep}{1em}
\newtheoremstyle{thmoverhang} %% Name
{} 
{}
{\sffamily}
{} 
{\bfseries}
{} 
{0pt}
{\vtop to 0pt{\hbox to -\marginlabelsep{\hss\thmname{#1}}
        \hbox to -\marginlabelsep{\hss\thmnumber{#2}}}\thmnote{#3\\}%
}
\theoremstyle{thmoverhang}
\newtheorem{thm}{Theorem}

（事实上​​，它是由本网站的另一位用户贡献的，但这不是重点。）我最近想使用包在我认为重要的定理周围添加一个框\mdframed，就像这样

\newenvironment{fthm}{\begin{mdframed}\begin{thm}}{\end{thm}\end{mdframed}\vspace{-0.3cm}

但这会导致一个问题，即盒子里没有定理和计数器（见下图）。我怎样才能使框更大，以同时包含定理描述和定理标题和计数器？此外，是否可以抬起框的上边框；它似乎太低了，框内文本的顶部和底部填充似乎不相等。任何意见都值得赞赏！

梅威瑟：

\documentclass{article}

\usepackage{amsthm}
\usepackage{mdframed}
\usepackage{lipsum}

\newlength{\marginlabelsep}\setlength{\marginlabelsep}{1em}
\newtheoremstyle{thmoverhang} %% Name
{} 
{}
{\sffamily}
{} 
{\bfseries}
{} 
{0pt}
{\vtop to 0pt{\hbox to -\marginlabelsep{\hss\thmname{#1}}
        \hbox to -\marginlabelsep{\hss\thmnumber{#2}}}\thmnote{#3\\}%
}
\theoremstyle{thmoverhang}
\newtheorem{thm}{Theorem}

\renewcommand{\familydefault}{\sfdefault}

\newenvironment{fthm}{ \begin{mdframed}\begin{thm} }{ \end{thm}\end{mdframed}\vspace{-0.3cm} }

\setlength{\parskip}{1em}

\begin{document}
    \begin{fthm}
    Theorem Description Theorem Description Theorem Description Theorem Description
    \end{fthm}
    \lipsum[1]
\end{document}

Answer 1

和tcolorbox：

\documentclass{article}
\usepackage{lipsum}%<--- for testing purpose only
\usepackage[most]{tcolorbox}
\newcounter{myth}
\tcbset{
    commonopt/.style={
        enhanced,
        enhanced jigsaw,
        breakable, 
        sharp corners,
        left=80pt,
        fontupper=\itshape,
        opacityback=0,
        boxrule=1pt,
        text width=\linewidth,
        oversize,
        },
    }
  
\tikzset{
    titlenode/.style={
        anchor=north west, 
        font=\bfseries, 
        text width=66pt, 
        inner sep=3mm+1pt, 
        align=right
    }
  }

\newtcolorbox[use counter=myth]{thm}[2][]{%
    commonopt,
    opacityframe=0,
    overlay={\node[titlenode] at (frame.north west) {\vphantom{p}Theorem~\themyth\ #2};},
    #1
}

\newtcolorbox[use counter=myth]{fthm}[2][]{%
    commonopt,
    before skip=14pt plus 2pt minus 2pt,
    after skip=14pt plus 2pt minus 2pt,
    overlay={\node[titlenode] at (frame.north west) {\vphantom{p}Theorem~\themyth\ #2};},
    #1
}

\begin{document}
\lipsum[1]

Theorem \ref{th:nofnot} is with no frame and no title, only with theorem number.
\begin{thm}[label=th:nofnot]{}
    Theorem Description Theorem Description Theorem Description Theorem Description
\end{thm}
Theorem \ref{th:nofyest} is with no frame but with title, other than number.
\begin{thm}[label=th:nofyest]{(Pythagoras)}
    Theorem Description Theorem Description Theorem Description Theorem Description
\end{thm}
Theorem \ref{th:yesfnot} is with frame but without title, only number.
\begin{fthm}[label=th:yesfnot]{}
    Theorem Description Theorem Description Theorem Description Theorem Description
\end{fthm}
Theorem \ref{th:yesfyest} is with frame, title and number.
\begin{fthm}[label=th:yesfyest]{(Pythagoras)}
    Theorem Description Theorem Description Theorem Description Theorem Description
\end{fthm}
\lipsum[1]
\end{document}