Shaded Theorems – Spanning Pages with Thmtools

amsthmpage-breakingtheoremsthmtools

When the thmtools package is used to create theorem environments with a shaded background, it does not allow separate theorems to span more than one page. This is a rather severe problem if the document contains many long theorems, one after the other. Here is a minimal example.

\documentclass{minimal}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage[english]{babel}
\usepackage{blindtext}

\declaretheoremstyle[
    shaded={bgcolor=\color{rgb}{0.9,0.9,0.9}}  % comment this line in/out
]{theorem}
\declaretheorem[style=theorem]{theorem}

\begin{document}

\begin{theorem}
\blindtext[5]
\end{theorem}

\begin{theorem}
\blindtext[5]
\end{theorem}

\end{document}

Here is what it looks like including and not including shading:
Bad Good

How does one include shading, but allow the theorems to span between pages?

Best Answer

You can use \newmdtheoremenv from the mdframed package; a little example (change the lengths and other settings according to your needs):

\documentclass{article}
\usepackage[english]{babel}
\usepackage[margin=2cm]{geometry}% just for the example
\usepackage{xcolor}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage{mdframed}
\usepackage{blindtext}

\definecolor{mybg}{rgb}{0.9,0.9,0.9}

\newmdtheoremenv [backgroundcolor=mybg, %
innertopmargin =0pt , %
splittopskip = \topskip, % 
skipbelow= 6pt, %
skipabove=6pt, %
topline=false,bottomline=false,leftline=false,rightline=false,]{theorem}{Theorem}

\begin{document}

\begin{theorem}
\blindtext[5]
\end{theorem}

\begin{theorem}
\blindtext[5]
\end{theorem}

\end{document}

enter image description here

As Ulrich Schwarz comments, you can use the preheadhook, postfoothook hooks form thmtools to add the mdframed environment with the desired specifications:

\documentclass{article}
\usepackage[english]{babel}
\usepackage[margin=2cm]{geometry}% just for the example
\usepackage{xcolor}
\usepackage{amsthm}
\usepackage{thmtools}
\usepackage{mdframed}
\usepackage{blindtext}
\usepackage{thmtools}

\definecolor{mybg}{rgb}{0.9,0.9,0.9}

\declaretheoremstyle[
headfont=\normalfont\bfseries,
notefont=\mdseries, notebraces={(}{)},
bodyfont=\normalfont\itshape,
postheadspace=0.5em,
preheadhook={\begin{mdframed}[backgroundcolor=mybg, %
  innertopmargin =0pt , splittopskip = \topskip, % 
  skipbelow= 6pt, skipabove=6pt, %
  topline=false,bottomline=false,leftline=false,rightline=false]},
postfoothook=\end{mdframed}
]{mystyle}
\declaretheorem[style=mystyle]{theorem}

\begin{document}

\begin{theorem}
\blindtext[5]
\end{theorem}

\begin{theorem}
\blindtext[5]
\end{theorem}

\end{document}

Related Solutions

Theorems – Decorations That Stay with Theorem Environment

The problem is that theorems are lists and lists introduce break points at their beginning and ending; as you put proofs inside theorems, your theorem ending has two break points (so preventing the break needs to overcome both).

The simplest would probably be to rewrite the theorem environments without using lists, but that means loosing (or rewritting) support of ntheorem features. And it's not guaranteed it will always work as things like \[...\] may also introduce break points (but setting \postdisplaypenalty=10000 inside the theorem does the trick).

Here's an attempt; I have tried to eliminated all possible break points, but using things like {center}, {enumerate}, {itemize} might introduce a break point (with the enumitem package you can use the endpenalty=10000 key to prevent this). This implementation supposes that your proofs will always end just before \end{theorem}.

\documentclass{memoir}

\usepackage{amsmath}
\usepackage{lipsum}
\usepackage{multido,xcolor}

\newcounter{theorem}[chapter]
\newenvironment{theorem}
  {\par\noindent\theoremhang\par\nobreak\noindent
   \refstepcounter{theorem}\postdisplaypenalty=10000 %
   {\sffamily\bfseries\upshape Theorem \thetheorem}\ \ignorespaces}
  {\par\nobreak\noindent\theoremhung\par\addvspace{\topsep}}

\newenvironment{proof}
  {\par\addvspace{\topsep}\noindent{\sffamily\bfseries\upshape Proof}\ \ignorespaces}
  {\par\nobreak}% no spacing here so that supposes you will always use {proof} inside {theorem} or else there might be some problems.

\newcommand{\theoremhang}{% top theorem decoration
  \begingroup%
    \setlength{\unitlength}{.005\linewidth}% \linewidth/200
    \begin{picture}(0,0)(1.5,0)%
      \linethickness{0.45pt} \color{black!50}%
      \put(-3,2){\line(1,0){206}}% Top line
      \multido{\iA=2+-1,\iB=50+-10}{5}{% Top hangs
        \color{black!\iB}%
        \put(-3,\iA){\line(0,-1){1}}% Top left hang
        \put(203,\iA){\line(0,-1){1}}% Top right hang
      }%
    \end{picture}%
  \endgroup%
}%

\newcommand{\theoremhung}{% bottom theorem decoration
  \begingroup%
    \setlength{\unitlength}{.005\linewidth}% \linewidth/200
    \begin{picture}(0,0)(1.5,0)%
      \linethickness{0.45pt} \color{black!50}%
      \put(-3,0){\line(1,0){206}}% Bottom line
      \multido{\iA=0+1,\iB=50+-10}{5}{% Bottom hangs
        \color{black!\iB}%
        \put(-3,\iA){\line(0,1){1}}% Bottom left hang
        \put(203,\iA){\line(0,1){1}}% Bottom right hang
      }%
    \end{picture}%
  \endgroup%
}%


\begin{document}

\chapter{First chapter}
\lipsum[1]

\begin{theorem}%
If~$G$ is a connected graph of order $n\geq 3$ and size~$m$, then
\[
    g(G)\geq \frac{m}{6}-\frac{n}{2}+1.%
\]

\begin{proof}%
Suppose a connected graph~$G$ of order $n\geq 3$ and size~$m$ is embedded in a surface of genus~$g(G)$, thus producing~$f$ faces. Then it follows by Theorem~XX that every face is a 2-cell and hence by Theorem~YY that $n-m+f=2-2\,g(G)$. An identical argument as in the proof of Theorem~ZZ shows that $3f\leq 2m$ and so
\[
    2-2\,g(G)=n-m+f\leq n-m+\frac{2m}{3},%
\]
from which the desired inequality follows.%
\end{proof}%
\end{theorem}%

\lipsum[2]

\begin{theorem}%
If~$G$ is a connected graph of order $n\geq 3$ and size~$m$, then
\[
    g(G)\geq \frac{m}{6}-\frac{n}{2}+1.%
\]
\end{theorem}%

\lipsum[3]

\begin{theorem}%
\lipsum[4]
\end{theorem}%

\lipsum[5]

\end{document}

[Tex/LaTex] numbering different theorem names with thmtools

You want

\newtheorem{theorem}{Theorem}[section]

not \numberwithin. I added thmtools and \listoftheorems to the example.

\documentclass{article}
\usepackage{amsmath, amssymb}
\usepackage[mathscr]{eucal}
\usepackage{amsthm,thmtools}
\usepackage{amscd}

\newtheorem{theorem}{Theorem}[section]
\newtheorem{lemma}[theorem]{Lemma}
\newtheorem{corollary}[theorem]{Corollary}
\theoremstyle{definition}
\newtheorem{definition}[theorem]{Definition}

\begin{document}

\section{Some Results}

\begin{lemma}
Here is a lemma.
\end{lemma}

\begin{definition}
Here is a definition.
\end{definition}

\begin{theorem}
Here is a theorem.
\end{theorem}

\begin{theorem}
Here is another theorem.
\end{theorem}

\begin{corollary}
Here is a corollary.
\end{corollary}

\listoftheorems

\end{document}

enter image description here

Best Answer

Related Solutions

Theorems – Decorations That Stay with Theorem Environment

[Tex/LaTex] numbering different theorem names with thmtools

Related Question