\typeout{ LaTeX 2.09 substyle: ShadeThm <94/07/11 jh>}
% ShadeThm.sty
%   Shaded theorem environments in LaTeX 2.09 with \newshadetheorem instead of
% \newtheorem.  Requires PostScript.
%
% USAGE
%   Used as a LaTeX substyle
%      \documentstyle[...,shadethm,...]{...}
% it allows declarations like
%      \newshadetheorem{theorem}{Theorem}
% so that
%      \begin{theorem}  $e=mc^2$  \end{theorem}
% will produce the usual theorem text, only placed in a shaded box.
%
% REMARKS
%  (1) You can of course have non-shaded environments, also.  The 
%  \newtheorem command still works (but see Remark (2)).
%  (2) Numbering within:
%    LaTeX allows you to say \newtheorem{guess}{Conjecture}[section] so
%  that at each new section the conjectures are numbered starting again
%  at 1.  So does \newshadetheorem.
%    LaTeX also allows you to say \newtheorem{remark}[guess]{Remark} so
%  that remark and guess use the same counter: 
%      \begin{guess} 
%         Dinosaurs are small at one end, large in the middle,
%         and very small again at the other end.
%      \end{guess}
%      \begin{remark}
%         This conjecture is due to me.
%      \end{remark}
%   gets printed as
%      Conjecture 1  Dinosaurs are small at one end, large in the middle, and
%      very small again at the other end.
%      Remark 2  This conjecture is due to me.
%  The \newshadetheorem allows the same thing, but with one change.  If you want
%  to refer to a theorem environment `xxx' that was declared with 
%  \newshadetheorem{xxx}{Xxx} then you must call it `shadexxx': e.g.,
%      \newshadetheorem{thm}{Theorem}
%      \newshadetheorem{note}[shadethm]{Note}
%  (references to non-shaded theorem environments, of course, go as usual).
%  (3) Uses fancybox.sty and pstricks.sty.  They are available, for instance,
%  in the TeX-archive at pip.shsu.edu.  In particular, they require PostScript
%  for the shade.  If you want to figure out a way to, for example, use PiCTeX
%  to shade, then that could work also.  (I use dvips; PSTricks may work with
%  other PS drivers but it definitely works with dvips.)
%
% INSTALLATION
%   Put this where your TeX looks for .sty files.  In emTeX that is probably
%  c:\emtex\texinput\shadethm.sty.
%   There are three parameters to set the default for (try it as it is, first).
%    (i) thmshade  the darkness of the shading
%    (ii) shadeparindent  the paragraph indentation inside the shaded text
%    (iii) frameboxsep  the length by which the shade box surrounds the text
% Find them by using your editor to find `PARAMETER'.
%  If you want this file to input fancybox and pstricks (that is, you don't
% want to ask for them yourself) uncomment those lines.
%
% BUGS
%  1) Page breaks are a problem since it sets the theorem before it shades it.
%  2) I haven't tested it with the new LaTeX.  
%
% HISTORY
%  94VII11 jim hefferon hefferon@smcvax.smcvt.edu.  First written (after lots
%    of sporadic tries, over months; I couldn't get any of the extant shading 
%    macros to work with theorems) from a hint in TvZ's Fancybox writeup. 
%    It's all so easy once you know how.
%
%\input{fancybox.sty}
%\input{pstricks.sty}

% PARAMETER: thmshade 
% Set the default darkness for the shading.
% I find .97 looks good out of my printer, but a darker shade like .92 is 
% needed to make it copy well.  (PostScript sets 0 as black and 1 as white.)
% This can be reset in each document, say with \newgray{thmshade}{.92}
% (or with \newrgbcolor{thmshade}{num1 num2 num3} for color, I think).
\newgray{thmshade}{.97}  

% PARAMETER: saveparindent
% Normally, in theorems, paragraphs retain their usual indent.  But inside
% a minipage they lose their indent, so I need to restore it once I'm inside
% the minipage that is to be shaded.   This can be changed inside of each 
% document, say with \resetlength{\saveparindent}{0pt}.
\newlength{\saveparindent}              %to have paragraphs default to their 
\setlength{\saveparindent}{\parindent}  %usual indent inside the minipage

% PARAMETER: frameboxsep
% I think the shading looks best if the text doesn't run all the way to the
% exact edge of the gray.  That is, I like the gray to overlap outside the text
% box a little.  That amount is this number.  This can be changed inside of
% each document, say with \resetlength{\frameboxsep}{.2ex}.
\newlength{\frameboxsep}        % user can change in a .sty file or on 
\setlength{\frameboxsep}{2pt}   % a per-document basis.

\newbox{\shadesavebox}        % no `@'; users can redefine shadebox if they want
\newenvironment{shadebox}%    % shadow boxes or something. 
{\beginsbox{\shadesavebox}\begin{minipage}{\textwidth}%
\setlength{\parindent}{\saveparindent}}%
{\end{minipage}\endsbox%
{\begin{trivlist}\item[]%
\psframebox*[fillcolor=thmshade,boxsep=false,framesep=\frameboxsep]{%
\usebox{\shadesavebox}}%
\end{trivlist}}}

%  The definition of \newshadetheorem is modelled on the one for \newtheorem
% in latex.tex.
%  The invocation possibilities are:
%   \newshadetheorem{NAME}{TEXT}[COUNTER]
%      e.g., \newshadetheorem{theorem}{Theorem}[section] meaning to allow
%      one to say \begin{theorem} $e=mc^2$ \end{theorem} to produce
%        Theorem 1.1.1 e=mc2
%      shaded and numbered by section.
%   \newshadetheorem{NAME}[OLDNAME]{TEXT}
%      e.g., \newshadetheorem{remark}[theorem]{Remark} meaning to allow
%      one to say \begin{remark} Obvious. \end{remark} to produce
%        Remark 1.1.2  Obvious.
%      shaded and numbered with the same counter used for theorems.
% The flowchart for parsing the arguments goes like this.
%   1) \newshadetheorem{#1}    (note  #1<--NAME)
%   2) If the next character is `[' then we have the second case.  This
%       is handled by \shade@othm
%   3) If not, go to \shade@nthm.  There are two cases here, either there
%       is an optional argument (this is handled by \shade@xnthm) or there is
%       not (this is handled by \shade@ynthm).
% (Possibly these cases could be folded somewhat as all use the same tail.)
% Notice I have to have different names for the theorem and the environment.
% I elected to call the theorem `xxx' by the name `shadexxx' so the user 
% just says `\begin{xxx} ...' for the environment.   (All this is, of course,
% just adapted from Lamport's code.)
%
\def\newshadetheorem#1{\@ifnextchar[{\shade@othm{#1}}{\shade@nthm{#1}}}

\def\shade@othm#1[#2]#3{%
\newtheorem{shade#1}[#2]{#3}%
\newenvironment{#1}%
{\begin{shadebox}\begin{shade#1}}%  
{\end{shade#1}\end{shadebox}}}

\def\shade@nthm#1#2{\@ifnextchar[{\shade@xnthm{#1}{#2}}{\shade@ynthm{#1}{#2}}}

\def\shade@xnthm#1#2[#3]{%
\newtheorem{shade#1}{#2}[#3]%
\newenvironment{#1}%
{\begin{shadebox}\begin{shade#1}}%
{\end{shade#1}\end{shadebox}}}

\def\shade@ynthm#1#2{%
\newtheorem{shade#1}{#2}%
\newenvironment{#1}%
{\begin{shadebox}\begin{shade#1}}%
{\end{shade#1}\end{shadebox}}}

\endinput %end shadethm.sty
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-test.tex-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
\documentstyle[fancybox,pstricks,shadethm]{article}

\newshadetheorem{theorem}{Theorem}
\newshadetheorem{cor}[shadetheorem]{Corollary}
\newtheorem{remark}[shadetheorem]{Remark}

\begin{document}
Here is some initial text before the shaded box.

\begin{theorem}
This is the text to be shaded.
\end{theorem}

This is some text after the first shade.
It is separated from the environments by a blank line; that is 
all handled as usual in \LaTeX.

\begin{cor}
This is more text to be shaded.
It is numbered with the same counter as the environment above.

Multiple paragraphs will be handled with the usual paragraph indentation,
unless of course the user asks for a different paragraph indentation inside
the environment.
\end{cor}

\begin{remark}
More text.
This time not set in shade, however it is numbered in the same sequence.
\end{remark}

Finishing text.
\end{document}