\ProvidesPackage{rtthesis-theorems}[2010/02/18 Theorem-like environments for the rtthesis class]

\@ifpackageloaded{rtthesis-captions}{}{% If not loaded...
  \PackageError{rtthesis-theorems}{%
    The package rtthesis-captions must be loaded\MessageBreak
    before rtthesis-theorems.  Since\MessageBreak
    rtthesis-theorems cannot guess which\MessageBreak
    character encoding you prefer, it won't\MessageBreak
    load rtthesis-captions for you, so you have\MessageBreak
    to do it yourself%
  }{%
    The package rtthesis-captions must be loaded\MessageBreak
    before rtthesis-theorems.  Since\MessageBreak
    rtthesis-theorems cannot guess which\MessageBreak
    character encoding you prefer, it won't\MessageBreak
    load rtthesis-captions for you, so you have\MessageBreak
    to do it yourself%
  }
}

% Use same counter for theorem-like environments?
\newif\ifrtthm@shareTheoremCounter
\DeclareOption{sharecounter}{\rtthm@shareTheoremCountertrue}
\DeclareOption{nosharecounter}{\rtthm@shareTheoremCounterfalse}

\ExecuteOptions{nosharecounter}

% Put breaks after theorem (and similar) labels?
\newif\ifrtthm@break
\DeclareOption{break}{\rtthm@breaktrue}
\DeclareOption{nobreak}{\rtthm@breakfalse}

\ExecuteOptions{nobreak}

% Choice of definition style
\newif\ifrt@definitionNotTheorem
\newif\ifrt@definitionMarks
\DeclareOption{definition=theorem}{\rt@definitionNotTheoremfalse}
\DeclareOption{definition=naked}{\rt@definitionNotTheoremtrue\rt@definitionMarksfalse}
\DeclareOption{definition=marks}{\rt@definitionNotTheoremtrue\rt@definitionMarkstrue}

\ExecuteOptions{definition=naked}

% Should we use italics or slanted text in theorems?
\newif\ifrtthm@slanted
\DeclareOption{slanted}{\rtthm@slantedtrue}
\DeclareOption{italics}{\rtthm@slantedfalse}

\ExecuteOptions{italics}

% Use parskip.sty and adjust sectioning commands?
\newif\ifrtthm@parskipDefault
\rtthm@parskipDefaulttrue
\newif\ifrtthm@parskip
\DeclareOption{noparskip}{\rtthm@parskipfalse\rtthm@parskipDefaultfalse}
\DeclareOption{parskip}{\rtthm@parskiptrue\rtthm@parskipDefaultfalse}

\@ifpackageloaded{parskip}{%
  \rtthm@parskiptrue
}{% In case KpFonts was not loaded:
  \rtthm@parskipfalse
  \AtBeginDocument{%
    \ifrtthm@parskipDefault
    \@ifpackageloaded{parskip}{%
      \PackageWarningNoLine{rtthesis-theorems}{%
        The default setting regarding `parskip' or\MessageBreak
        `noparskip' is `noparskip' since package\MessageBreak
        parskip was loaded after \MessageBreak
        rtthesis-theorems.  This is probably not\MessageBreak
        what you want.  Avoid this warning by\MessageBreak
        explicitly passing one of the options\MessageBreak
        `parskip' or `noparskip', or change the\MessageBreak
        package loading order
      }}{}%
    \fi
  }
}

% When should counters be reset?
% Use same counter for theorem-like environments?
\DeclareOption{reset=chapter}{\def\rtthm@reset{chapter}}
\DeclareOption{reset=section}{\def\rtthm@reset{section}}

\@ifundefined{thechapter}{%
  \ExecuteOptions{reset=section}}{%
  \ExecuteOptions{reset=chapter}}


\ProcessOptions\relax


\RequirePackage{amsthm}


\ifrtthm@slanted
% It's dangerous to use the italic shape, since italic small caps seem hard to find.
\let\theoremshape\slshape
\else
\let\theoremshape\itshape
\fi

\newlength{\rt@theoremtopskip}
\ifrtthm@parskip
\setlength{\rt@theoremtopskip}{1.5\parskip plus 1.5pt}
\else
\setlength{\rt@theoremtopskip}{0.5em plus 1.5pt}
\fi

% In case the user adjusts this length, and later decides not to use marks, we define the following length no matter whether marks are used or not.
\newlength{\rt@definitionlinewidth}
\setlength{\rt@definitionlinewidth}{0.3pt}

\ifrt@definitionMarks
\newcommand{\rt@definitionBeginMark}{%
  \begin{picture}(0,0)
    \settoheight{\unitlength}{(D)}
    \linethickness{\rt@definitionlinewidth}
    \put(-0.3,1.3){\line(0,-1){0.5}}
    \put(-0.3,1.3){\line(1,0){4}}
  \end{picture}%
}
\newcommand{\rt@definitionEndMark}{%
  \unskip
  % Whether we are in vmode here seems to depend on whether we are using parskip...
  \ifrtthm@parskip
  \ifvmode
  \nopagebreak\vspace{-\baselineskip}%
  \fi
  \fi
  \ifhmode
  \nopagebreak\\[-1\baselineskip]%
  \fi
  \nopagebreak\hspace*{\linewidth}%
  \begin{picture}(0,0)
    \settoheight{\unitlength}{(D)}
    \linethickness{\rt@definitionlinewidth}
    \put(0.3,-0.3){\line(0,1){0.5}}
    \put(0.3,-0.3){\line(-1,0){4}}
  \end{picture}%
}
\newcommand{\rt@topmarkskip}{%
  \settoheight{\unitlength}{(D)}%
  \ifhmode
  \par\vspace{-\rt@theoremtopskip}\vspace{0.3\unitlength}%
  \else
  \setlength{\unitlength}{0.3\unitlength}%
  \addtolength{\unitlength}{\parskip}
  \addvspace{\unitlength}%
  \fi
}
\newcommand{\rt@botmarkskip}{%
  \settoheight{\unitlength}{(D)}%
  \setlength{\unitlength}{0.3\unitlength}%
  \addtolength{\unitlength}{\parskip}
  \addvspace{\unitlength}%
%%% The following line does more than just cancelling the \addtolength{\unitlength}{\parskip} above.
  \rt@unparskip% Next thing that happens will probably be a \par, but we don't want that extra \parskip.
%
%%% By leaving TeX in hmode, it might be possible to continue the paragraph right after the environment...
%%% but how exactly should this be done?!
%%% One should probably redefine \par temporarily so that it produces the correct after-theorem space and then
%%% resets itself to the usual \par.  This would work as long as a \par is actually the first thing that follows
%%% the environment.  However, if the user really continues to add stuff in hmode, then this must be detected so that
%%% we can reset \par to its usual meaning before the user leaves hmode.  The important question seems to be:
%%%   How can we detect that the user is adding stuff in hmode before we reach the next \par?
}
\else
\newcommand{\rt@definitionBeginMark}{\relax}
\newcommand{\rt@definitionEndMark}{\relax}
\newcommand{\rt@topmarkskip}{%
  \ifhmode
  \par\vspace{-\rt@theoremtopskip}%
  \fi
}
\newcommand{\rt@botmarkskip}{%
  \rt@unparskip
%
%%% By leaving TeX in hmode, it might be possible to continue the paragraph right after the environment...
%%% See comments above.
}
\fi

\ifrtthm@shareTheoremCounter
\newtheoremstyle{break}{\rt@theoremtopskip}{\rt@theoremtopskip}{\theoremshape}{}{\bfseries}{}
  {\newline}{\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\newtheoremstyle{nobreak}{\rt@theoremtopskip}{\rt@theoremtopskip}{\theoremshape}{}{\bfseries}{.}
  {.75em}{\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\newtheoremstyle{definition}{\rt@theoremtopskip}{\rt@theoremtopskip}{\normalfont}{}{\bfseries}{.}
  {.75em}{\rt@definitionBeginMark\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\newtheoremstyle{remark}{\rt@theoremtopskip}{\rt@theoremtopskip}{\normalfont\small}{}{\slshape}{.}
  {.75em}{\rt@definitionBeginMark\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\else
\newtheoremstyle{break}{\rt@theoremtopskip}{\rt@theoremtopskip}{\theoremshape}{}{\bfseries}{}
  {\newline}{\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\newtheoremstyle{nobreak}{\rt@theoremtopskip}{\rt@theoremtopskip}{\theoremshape}{}{\bfseries}{.}
  {.75em}{\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\newtheoremstyle{definition}{\rt@theoremtopskip}{\rt@theoremtopskip}{\normalfont}{}{\bfseries}{.}
  {.75em}{\rt@definitionBeginMark\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\newtheoremstyle{remark}{\rt@theoremtopskip}{\rt@theoremtopskip}{\normalfont\small}{}{\slshape}{.}
  {.75em}{\rt@definitionBeginMark\thmname{#1}~\thmnumber{#2}\thmnote{~(#3)}}
\fi

\ifrtthm@break
\theoremstyle{break}
\else
\theoremstyle{nobreak}
\fi
\ifrtthm@shareTheoremCounter
\newtheorem{theorem}{\theoremname}[\rtthm@reset]
\newtheorem{lemma}[theorem]{\lemmaname}
\newtheorem{corollary}[theorem]{\corollaryname}
\newtheorem{proposition}[theorem]{\propositionname}
\else
\newtheorem{theorem}{\theoremname}[\rtthm@reset]
\newtheorem{lemma}{\lemmaname}[\rtthm@reset]
\newtheorem{corollary}{\corollaryname}[\rtthm@reset]
\newtheorem{proposition}{\propositionname}[\rtthm@reset]
\fi

\ifrt@definitionNotTheorem
\theoremstyle{definition}% Change theorem style unless the user prefers to use the break/nobreak style also for definitions.
\fi
\ifrtthm@shareTheoremCounter
\newtheorem{rt@definition}[theorem]{\definitionname}
\newtheorem{rt@assumption}[theorem]{\assumptionname}
\else
\newtheorem{rt@definition}{\definitionname}[\rtthm@reset]
\newtheorem{rt@assumption}{\assumptionname}[\rtthm@reset]
\fi
\renewcommand*{\thert@assumption}{A\arabic{rt@assumption}}

\newenvironment{definition}{\rt@topmarkskip\begin{rt@definition}}{\rt@definitionEndMark\end{rt@definition}\rt@botmarkskip}
\newenvironment{assumption}{\rt@topmarkskip\begin{rt@assumption}}{\rt@definitionEndMark\end{rt@assumption}\rt@botmarkskip}


\theoremstyle{remark}
\ifrtthm@shareTheoremCounter
\newtheorem{rt@remark}[theorem]{\remarkname}
\else
\newtheorem{rt@remark}{\remarkname}[\rtthm@reset]
\fi
\newenvironment{remark}{\rt@topmarkskip\begin{rt@remark}}{\rt@definitionEndMark\end{rt@remark}\rt@botmarkskip}

\renewenvironment{proof}[1][\proofname]{\par
  \pushQED{\qed}%
  \normalfont \topsep6\p@\@plus6\p@\relax
  \trivlist
\item[\hskip\labelsep\bfseries#1\@addpunct{:}]\ignorespaces
}{%
  \popQED\endtrivlist\@endpefalse
}

\ifrtthm@parskip
\newcommand{\rt@unparskip}{%
  \vspace{-\parskip}% It's hard to know which is best of \addvspace and \vspace here...
}
%%% Adjust space before proof environment
\let\ams@proof\proof
\let\ams@endproof\endproof
\renewenvironment{proof}{\rt@unparskip\ams@proof}{\ams@endproof}
\else
\newcommand{\rt@unparskip}{\relax}
\fi