Sstrhsrtj

I am trying to create a customized "proof" environment attached to a theorem. It looks like this:

So there is first the theorem, and then a gray bar starts on the inner margin. It ends, when the proof of the theorem is finished. It should also be possible to give a theorem without proof of cause.

The document you see above was created from the following code:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% HEADER

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

documentclass[a4paper,twoside,11pt]{article}

special{papersize=210mm,297mm}





%% Language %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

usepackage[USenglish]{babel}

usepackage[T1]{fontenc}

usepackage[ansinew]{inputenc}

usepackage{lmodern} % Type1-font for non-english texts and characters



%% Math Symbols %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

usepackage{amsmath}

usepackage{amsthm}

usepackage{amsfonts}



%% Other Packages %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

usepackage{color}                          % colors

usepackage{framed}                         % frames

usepackage{mdframed}                       % better frames



usepackage{fancyhdr}                   % Fancy headings



%% Style Definitions %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

numberwithin{equation}{section}



% My Theorem Style ============================================================



newtheoremstyle{myThmStyle}% name of the theorem

{6pt}% habovespacei

{6pt}% hbelowspacei

{itshape}% font

{}% hindenti

{}% hheadfonti

{}% hheadpuncti

{ }% hheadspacei

{thmname{normalfontlargetextsc{#1}normalsize} thmnote{#3:} thmnumber{ hfill normalfont(#2)}\[1pt]}



% Frame Styles ================================================================



definecolor{thmBgColor}{RGB}{250,250,250}

definecolor{thmLnColor}{RGB}{200,200,200}



mdfdefinestyle{MDFStyGrayScreen}{%

    linecolor=thmLnColor,

        backgroundcolor=thmBgColor,

        linewidth=1pt,

        topline=true,

    bottomline=true,

    rightline=false,

        leftline=false,

    outerlinewidth=2pt,

    roundcorner=0pt,

    innertopmargin=4pt, %baselineskip

    innerbottommargin=4pt, %baselineskip,

    innerrightmargin=3pt,

    innerleftmargin=3pt,

        skipabove=topskip,

        skipbelow=topskip,

        nobreak=true

        }



% Thorems =====================================================================



theoremstyle{myThmStyle}

newtheorem{myTheorem}[equation]{theorem}



% Proof environment ===========================================================

% (attached to theorem)



newenvironment{myTheoremEnvEx}[1][hsize]

{% 

defFrameCommand 

{%

    {color{thmLnColor}vrule width 8pt}%

    hspace{0pt}%must no space.

    fboxsep=5ptcolorbox{white}%

}%

vspace{-topskip}

vspace{-topskip}

vspace{-1pt}

MakeFramed{hsize#1advancehsize-widthnoindentFrameRestore}%

}

{endMakeFramed}

setlength{FrameSep}{0pt}



% Theorem environment =========================================================



newenvironment{theorem}[1]

{

begin{mdframed}[style=MDFStyGrayScreen]

begin{myTheorem}#1

}

{

end{myTheorem}

end{mdframed}

}



%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% DOCUMENT

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%



begin{document}





section{Section A}

label{sec:SectionA}



begin{theorem}[about something important] label{thm:important}

This is some important theorem with equations

[

    1 + 1 = 0 ;,

]

and text.

end{theorem} 



Some text with reference to theorem eqref{thm:important}.



begin{theorem}[about something important] label{thm:veryImportant}

This is some important theorem with equations

[

    1 + 1 = 0 ;,

]

and text.

end{theorem}%

begin{myTheoremEnvEx}

Proof of something important... The proof may exceed several pages. The proof may exceed several pages. The proof may exceed several pages. 



The proof may exceed several pages. The proof may exceed several pages. The proof may exceed several pages.

end{myTheoremEnvEx}



end{document}

There are two things that do not work yet:

1. When the text within the proof exceeds one page, then there appears a small gap between theorem and proof.


2. The gray bar of the proof is currently always on the left side. But I want it to be on the inner margin (left for right pages and right for left pages).

The first problem is certainly due to my dirty bugfix

vspace{-topskip}

vspace{-topskip}

vspace{-1pt}

within newenvironment{myTheoremEnvEx}[1][hsize].

Can you help me with this? I'd also be happy to see better solutions.

This is somewhat of an old question but I was interested in how to put a line down the margin, where the side changes depending on the parity of the page number.

Rather than using the mdfamed package I have used tcolorbox as I am more used to using it. For answer this question, tcolorbox has one particularly useful switch, toggle left and right, that can be used to swap the role of left and right in various instances. This is what is used to address point #2 in the OPs question.

Apart from this it is fairly straightforward except for the creation of a new theorem "style" for use by newtcbtheorem to cater for the particular style required by the question. This is done by the line

tcbset{theorem style/theorem wide name and number/.code={

                lettcb@theo@title=tcb@theo@widetitle}

}

with the associated macro tcb@theo@widetitle doing the actual work.
This the output

from the following code (updated for tcolorbox version 1.14, with breakable added to the theorem style to allow it also to break over pages)

documentclass[a4paper,twoside,11pt]{article}



usepackage{amsmath,amsthm,amsfonts}

usepackage{lipsum}



%% Other Packages %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

usepackage{tcolorbox}

tcbuselibrary{skins,breakable,theorems}

usepackage{changepage}% for use of ifoddpage below



% Theorems ==============

definecolor{thmBgColor}{RGB}{250,250,250}

definecolor{thmLnColor}{RGB}{200,200,200}



makeatletter

% define a new theorem style

deftcb@theo@widetitle#1#2#3{hbox to textwidth{textsc{large#1}normalsizespace#3hfil(#2)}}

tcbset{

  theorem style/theorem wide name and number/.code={ lettcb@theo@title=tcb@theo@widetitle},

  proofbox/.style={skin=enhancedmiddle,breakable,parbox=false,boxrule=0mm,

    check odd page, toggle left and right, colframe=thmLnColor,

    leftrule=8pt, rightrule=0mm, boxsep=0mm,arc=0mm, outer arc=0mm,

    left=3mm,right=0mm,top=0mm,bottom=0mm, toptitle=0mm,

    bottomtitle=0mm,colback=white,

    before={parvskip-2pt},after={parsmallbreak},

  },

}

newtcolorbox{ProofBox}{proofbox}

makeatother



newtcbtheorem[use counter=equation, number within=section]{mytheorem}{Theorem}%

  {theorem style=theorem wide name and number,enhanced,breakable,

  arc=0mm,outer arc=0mm,parbox=false,

  boxrule=0mm,toprule=2pt,bottomrule=2pt,left=1mm,right=1mm,

  titlerule=0mm,toptitle=0mm,bottomtitle=0mm,top=0mm,

  colback=thmBgColor,colframe=thmLnColor,

  title style={color=thmBgColor}, coltitle=black,

  attach title to upper={parnoindent},

  before={parvfillsmallbreaknoindent}, after={par},

  fonttitle=normalfontlarge,

  }{thm}



newenvironment{theorem}[2]{noindentmytheorem{#1}{#2}}{endmytheorem}



letrealproofproof

letrealendproofendproof

renewenvironment{proof}[1][Proof]{ProofBoxstruttextsc{#1}space}{endProofBox}



%% Style Definitions

numberwithin{equation}{section}



begin{document}

quadclearpage % to make it easier to get a screenshot with two pages



section{Section A}

label{sec:SectionA}



begin{theorem}[about something important]{important}

This is some important theorem with equations

[

    1 + 1 = 0 ;,

]

and text.

end{theorem}



begin{proof}

  lipsum*[1-8] Theorem eqref{thm:important}.

end{proof}



begin{theorem}[about something important]{veryImportant}

This is some important theorem with equations

[

    1 + 1 = 0 ;,

]

and text.



It continues for some more lines, so that a page break occurs during

its statement.

end{theorem}



begin{proof}[Proof of something important]

lipsum[1]

end{proof}



end{document}