%% This is file 'prerex.sty'
%%
%% Copyright (C) 2006-19 R. D. Tennent, rdt@cs.queensu.ca
%% 
%% This work may be distributed and/or modified under the
%% conditions of the LaTeX Project Public License, either version 1.3
%% of this license or (at your option) any later version.
%% The latest version of this license is in
%%   http://www.latex-project.org/lppl.txt
%% and version 1.3 or later is part of all distributions of LaTeX
%% version 2003/12/01 or later.
%% 
%% This work has the LPPL maintenance status "author-maintained".
%%
\NeedsTeXFormat{LaTeX2e}[1995/12/01]
\ProvidesPackage{prerex}[2019/11/15 v6.8.0 LaTeX style for prerequisite charts, pgf version]
%
% Changelog is at the end of the file.
%
% Instructions supported inside  \begin{chart} ... \end{chart}:
%
%   \[req|opt]{half|full}course[c] x,y: {course code}{course title}{timetable code}[{color}]  
%
%   \mini x,y: {course code}
%
%   solid arrow:  \prereq x0,y0,x1,y1:    \prereqc x0,y0,x1,y1;curvature:
%   dotted arrow: \coreq x0,y0,x1,y1:     \coreqc x0,y0,x1,y1;curvature:
%   dashed arrow: \recomm x0,y0,x1,y1:    \recommc x0,y0,x1,y1;curvature:
%
%   \text x,y: {lines of text}
%
%   \grid      coordinate grid background
%
% Stand-alone instructions (for explanatory notes):
%
%   \solidarrow     in-line solid arrow
%   \dottedarrow    in-line dotted arrow
%   \dashedarrow    in-line dashed arrow
%
%   \lightbox   in-line light course box
%   \boldbox    in-line bold course box
%   \dottedbox  in-line dotted course box
%
% The nominal diagram width is (\textwidth divided by \unit) + 10
%

\newlength{\unit}
\setlength{\unit}{5.7816pt}  % 10 pixels per unit at 125dpi; 1pt = (1/72.27) in.
\newcommand{\PixelsPerUnit}{10}
\newcommand{\dpi}{125} 

\RequirePackage{relsize}
\RequirePackage{calc}
\RequirePackage{pgf}[2013/12/18]
\RequirePackage{tikz}\usetikzlibrary{arrows.meta}
\RequirePackage{textcomp}
\PassOptionsToPackage{urlcolor=black,colorlinks,raiselinks}{hyperref}
\RequirePackage{hyperref}

\RequirePackage{xcolor}
\definecolor{light}{gray}{0.5}
\definecolor{somewhatlight}{gray}{0.7}
\definecolor{verylight}{gray}{0.85}
\definecolor{white}{rgb}{1.0,1.0,1.0} % not transparent, hides grid

\newcommand{\DefaultCurvature}{20} 
%     where the argument should be in the range -100:100; 0 means no curvature.

\newcommand{\CourseURL}[3]{#3.html}
%     where the arguments supplied at the call are the x and y coordinates
%     and the course code.

\newcommand{\background}{yellow!15}

\newcommand{\solidwidth}{0.5pt}
\newcommand{\boldwidth}{1.0pt}
\newcommand{\dottedwidth}{0.8pt}
\newcommand{\dashedwidth}{0.5pt}
\newcommand{\smallersize}{\relsize{-3}}
\newcommand{\baselineAdj}{-0.5ex}

\newcounter{@myangle}
\newcounter{@inangle}
\newcounter{@dx}
\newcounter{@dy}

\newif\ifgridon
\gridonfalse
\newcounter{@gridwidth}
\newcounter{@gridright}
\newcounter{@gridheight}
\newcounter{@gridtop}

\newcounter{@diagwidth}
\newcounter{diagheight}

\setcounter{diagheight}{75}
\ifdim\paperwidth>\paperheight
  \setcounter{diagheight}{65}
\fi

\def\@unitmult{\unit * 5} % used for the grid and as the minimum height of half-course boxes

\pgfsetlayers{}

\def\solidarrow{%
\tikz[x=\unit,y=\unit,baseline=\baselineAdj]
\draw[-{Latex[length=4pt]},line width =\solidwidth] (0,0) -- (4,0);
}

\def\dottedarrow{%
\tikz[x=\unit,y=\unit,baseline=\baselineAdj]
\draw[-{Latex[length=4pt]},loosely dotted,line width=\dottedwidth] (0,0) -- (4,0);
}

\def\dashedarrow{%
\tikz[x=\unit,y=\unit,baseline=\baselineAdj]
\draw[-{Latex[length=4pt]},dashed,line width=\dashedwidth] (0,0) -- (4,0);
}

\def\lightbox{%
\tikz[thin,baseline=\baselineAdj]\node[draw,rounded corners=2pt,inner xsep=1.8pt] 
{\rule[-2pt]{0pt}{4pt}light};
}

\def\boldbox{%
\tikz[baseline=\baselineAdj]\node[draw,line width=\boldwidth,rounded corners=2pt,inner xsep=1.8pt] 
{\rule[-2pt]{0pt}{4pt}\bfseries bold};
}


\def\dottedbox{%
\tikz[baseline=\baselineAdj]\node[draw,dotted,line width=\boldwidth,rounded corners=2pt,inner xsep=1.8pt] 
{\rule[-2pt]{0pt}{4pt}dotted};
}

\pgfdeclarelayer{arrows}
\pgfdeclarelayer{courses}
\pgfdeclarelayer{grid}
\pgfsetlayers{grid,arrows,courses,main}

\def\@halfcourse#1,#2:#3#4#5{%
\begin{pgfonlayer}{courses}%
\node[draw,thin,fill=\background,minimum height=\@unitmult](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{0.8}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@halfcoursec#1,#2:#3#4#5#6{%
\begin{pgfonlayer}{courses}%
\node[draw,thin,fill=#6,minimum height=\@unitmult](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{0.8}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize\selectfont{#3}}%
\,\hfill\,%
{\smallersize{\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@reqhalfcourse#1,#2:#3#4#5{%
\begin{pgfonlayer}{courses}%
\node[draw,line width=\boldwidth,fill=\background,minimum height=\@unitmult](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{0.8}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize\bfseries#3}%
\,\hfill\,%
{\smallersize\bfseries\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}%
}};%
\end{pgfonlayer}%
}

\def\@reqhalfcoursec#1,#2:#3#4#5#6{%
\begin{pgfonlayer}{courses}%
\node[draw,line width=\boldwidth,fill=#6,minimum height=\@unitmult](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{0.8}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize\bfseries#3}%
\,\hfill\,%
{\smallersize\bfseries\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}%
}};%
\end{pgfonlayer}%
}


\def\@opthalfcourse#1,#2:#3#4#5{%
\begin{pgfonlayer}{courses}%
\node[draw,dotted,line width=\boldwidth,fill=\background,minimum height=\@unitmult](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{0.8}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@opthalfcoursec#1,#2:#3#4#5#6{%
\begin{pgfonlayer}{courses}%
\node[draw,dotted,line width=\boldwidth,fill=#6,minimum height=\@unitmult](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{0.8}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@fullcourse#1,#2:#3#4#5{%
\begin{pgfonlayer}{courses}%
\node[draw,thin,fill=\background](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{1.7}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@fullcoursec#1,#2:#3#4#5#6{%
\begin{pgfonlayer}{courses}%
\node[draw,thin,fill=#6](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{1.7}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@reqfullcourse#1,#2:#3#4#5{%
\begin{pgfonlayer}{courses}%
\node[draw,line width=\boldwidth,fill=\background](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{1.7}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize\bfseries#3}%
\,\hfill\,%
{\smallersize\bfseries\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@reqfullcoursec#1,#2:#3#4#5#6{%
\begin{pgfonlayer}{courses}%
\node[draw,line width=\boldwidth,fill=#6](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{1.7}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize\bfseries#3}%
\,\hfill\,%
{\smallersize\bfseries\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@fullcoursec#1,#2:#3#4#5#6{%
\begin{pgfonlayer}{courses}%
\node[draw,thin,fill=#6](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{1.7}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@optfullcourse#1,#2:#3#4#5{%
\begin{pgfonlayer}{courses}%
\node[draw,dotted,line width=\boldwidth,fill=\background](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{1.7}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}


\def\@optfullcoursec#1,#2:#3#4#5#6{%
\begin{pgfonlayer}{courses}%
\node[draw,dotted,line width=\boldwidth,fill=#6](x#1y#2) at (#1,#2)%
{
\renewcommand{\arraystretch}{1.7}%
\href{\CourseURL{#1}{#2}{#3}}{\begin{tabular}{@{\hspace{1pt}}c@{\hspace{1pt}}}%
{\smallersize#3}%
\,\hfill\,%
{\smallersize\renewcommand{\arraystretch}{0.5}\begin{tabular}[t]{@{}r@{}}#5\end{tabular}}%
\\ #4%
\end{tabular}}%
};%
\end{pgfonlayer}%
}

\def\@mini#1,#2:#3{%
\begin{pgfonlayer}{courses}%
\ifgridon
  \node[fill=white,draw=white](x#1y#2) at (#1,#2)%
  {
  \href{\CourseURL{#1}{#2}{#3}}{%
  {\smallersize\mdseries#3}}};%
\else
  \node[fill=none,draw=none](x#1y#2) at (#1,#2)%
  {
  \href{\CourseURL{#1}{#2}{#3}}{%
  {\smallersize\mdseries#3}}};%
\fi
\end{pgfonlayer}%
}

\def\@text#1,#2:#3{%
% include coordinates if grid on, but don't hyperlink if grid off
\begin{pgfonlayer}{courses}%
\ifgridon
  \node[fill=white,draw=white](x#1y#2) at (#1,#2)%
{\href{coord: #1,#2}{\sffamily\mdseries\renewcommand{\arraystretch}{0.5}\begin{tabular}[b]{@{}c@{}}#3\\[-0.4ex]\end{tabular}}};%
\else
  \node[fill=none,draw=none](x#1y#2) at (#1,#2){\sffamily\mdseries\renewcommand{\arraystretch}{0.5}\begin{tabular}[b]{@{}c@{}}#3\\[-0.4ex]\end{tabular}};%
\fi
\end{pgfonlayer}%
}

\def\@prereq#1,#2,#3,#4:{%
  \setcounter{@dy}{#2-#4}
  \ifnum\the@dy<10 
    \@straight#1,#2,#3,#4:
  \else\ifnum#1=#3 
    \@straight#1,#2,#3,#4:
  \else\ifnum#2=#4 
    \@straight#1,#2,#3,#4:
  \else
    \@prereqc#1,#2,#3,#4;\DefaultCurvature:
  \fi\fi\fi
}

\def\@prereqc#1,#2,#3,#4;#5:{%
  \ifnum#5=0 
    \@straight#1,#2,#3,#4:
  \else
    \@curved#1,#2,#3,#4;#5:
  \fi
} 

\def\@recomm#1,#2,#3,#4:{%
  \setcounter{@dy}{#2-#4}
  \ifnum\the@dy<10 
    \@straightDashed#1,#2,#3,#4:
  \else\ifnum#1=#3 
    \@straightDashed#1,#2,#3,#4:
  \else\ifnum#2=#4 
    \@straightDashed#1,#2,#3,#4:
  \else
    \@recommc#1,#2,#3,#4;\DefaultCurvature:
  \fi\fi\fi
}

\def\@recommc#1,#2,#3,#4;#5:{%
  \ifnum#5=0 
    \@straightDashed#1,#2,#3,#4:
  \else
    \@curvedDashed#1,#2,#3,#4;#5:
  \fi
} 

\def\@coreq#1,#2,#3,#4:{%
  \setcounter{@dy}{#2-#4}
  \ifnum\the@dy<10 
    \@straightDotted#1,#2,#3,#4:
  \else\ifnum#1=#3 
    \@straightDotted#1,#2,#3,#4:
  \else\ifnum#2=#4 
    \@straightDotted#1,#2,#3,#4:
  \else
    \@coreqc#1,#2,#3,#4;\DefaultCurvature:
  \fi\fi\fi
}

\def\@coreqc#1,#2,#3,#4;#5:{%
  \ifnum#5=0 
    \@straightDotted#1,#2,#3,#4:
  \else
    \@curvedDotted#1,#2,#3,#4;#5:
  \fi
} 



\def\@straight#1,#2,#3,#4:{%
  \begin{pgfonlayer}{arrows}
  \draw[draw=white,line width=1.5pt](x#1y#2) -- (x#3y#4) ;
  \ifgridon
    \draw[->,line width=\solidwidth](x#1y#2) -- node[anchor=mid] {\href{coord: #1,#2,#3,#4}{\textbullet}} (x#3y#4);
  \else
    \draw[->,line width=\solidwidth](x#1y#2) -- (x#3y#4) ;
  \fi
  \end{pgfonlayer}
}


\def\@curved#1,#2,#3,#4;#5:{
  \ifnum#4<#2
    \setcounter{@dy}{#2-#4}
    \ifnum#3<#1
      \setcounter{@dx}{#1-#3}
      \setcounter{@myangle}{-#5 * \the@dx * \the@dy * 2}
    \else
      \setcounter{@dx}{#3-#1}
      \setcounter{@myangle}{#5 * \the@dx * \the@dy * 2}
    \fi
  \else  
    \setcounter{@dy}{#4-#2}
    \ifnum#3<#1
      \setcounter{@dx}{#1-#3}
      \setcounter{@myangle}{-#5 * \the@dx * \the@dy * 2}
    \else
      \setcounter{@dx}{#3-#1}
      \setcounter{@myangle}{#5 * \the@dx * \the@dy * 2}
    \fi
  \fi
  \setcounter{@myangle}{\the@myangle / ((\the@dx + \the@dy) * (\the@dx + \the@dy))}
  \setcounter{@inangle}{180 - \the@myangle}
  \begin{pgfonlayer}{arrows}
  \draw[draw=white,line width=1.5pt](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] (x#3y#4) ;
  \ifgridon
    \draw[->,line width=\solidwidth](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] node[anchor=mid] {\href{coord: #1,#2,#3,#4}{\textbullet}} (x#3y#4) ;
  \else
    \draw[->,line width=\solidwidth](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] (x#3y#4) ;
  \fi
  \end{pgfonlayer}
}

\def\@straightDashed#1,#2,#3,#4:{%
\begin{pgfonlayer}{arrows}
\draw[draw=white,line width=1.5pt] (x#1y#2) -- (x#3y#4);
\ifgridon
  \draw[->,dashed,line width=\dashedwidth] (x#1y#2) -- node[anchor=mid] {\href{coord: #1,#2,#3,#4}{\textbullet}} (x#3y#4) ;
\else
  \draw[->,dashed,line width=\dashedwidth] (x#1y#2) -- (x#3y#4);
\fi
\end{pgfonlayer}
}

\def\@curvedDashed#1,#2,#3,#4;#5:{
  \ifnum#4<#2
    \setcounter{@dy}{#2-#4}
    \ifnum#3<#1
      \setcounter{@dx}{#1-#3}
      \setcounter{@myangle}{-#5 * \the@dx * \the@dy * 2}
    \else
      \setcounter{@dx}{#3-#1}
      \setcounter{@myangle}{#5 * \the@dx * \the@dy * 2}
    \fi
  \else  
    \setcounter{@dy}{#4-#2}
    \ifnum#3<#1
      \setcounter{@dx}{#1-#3}
      \setcounter{@myangle}{-#5 * \the@dx * \the@dy * 2}
    \else
      \setcounter{@dx}{#3-#1}
      \setcounter{@myangle}{#5 * \the@dx * \the@dy * 2}
    \fi
  \fi
  \setcounter{@myangle}{\the@myangle / ((\the@dx + \the@dy) * (\the@dx + \the@dy))}
  \setcounter{@inangle}{180 - \the@myangle}
  \begin{pgfonlayer}{arrows}
  \draw[draw=white,line width=1.5pt](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] (x#3y#4) ;
  \ifgridon
    \draw[->,dashed,line width=\dashedwidth](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] node[anchor=mid] {\href{coord: #1,#2,#3,#4}{\textbullet}} (x#3y#4);
  \else
    \draw[->,dashed,line width=\dashedwidth](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] (x#3y#4);
  \fi
  \end{pgfonlayer}
}

\def\@straightDotted#1,#2,#3,#4:{%
  \begin{pgfonlayer}{arrows}
  \draw[draw=white,line width=1.5pt] (x#1y#2) -- (x#3y#4);
  \ifgridon
    \draw[->,loosely dotted,line width=\dottedwidth] (x#1y#2) -- node[anchor=mid] {\href{coord: #1,#2,#3,#4}{\textbullet}} (x#3y#4) ;
  \else
    \draw[->,loosely dotted,line width=\dottedwidth] (x#1y#2) -- (x#3y#4);
  \fi
  \end{pgfonlayer}
}

\def\@curvedDotted#1,#2,#3,#4;#5:{
  \ifnum#4<#2
    \setcounter{@dy}{#2-#4}
    \ifnum#3<#1
      \setcounter{@dx}{#1-#3}
      \setcounter{@myangle}{-#5 * \the@dx * \the@dy * 2}
    \else
      \setcounter{@dx}{#3-#1}
      \setcounter{@myangle}{#5 * \the@dx * \the@dy * 2}
    \fi
  \else  
    \setcounter{@dy}{#4-#2}
    \ifnum#3<#1
      \setcounter{@dx}{#1-#3}
      \setcounter{@myangle}{-#5 * \the@dx * \the@dy * 2}
    \else
      \setcounter{@dx}{#3-#1}
      \setcounter{@myangle}{#5 * \the@dx * \the@dy * 2}
    \fi
  \fi
  \setcounter{@myangle}{\the@myangle / ((\the@dx + \the@dy) * (\the@dx + \the@dy))}
  \setcounter{@inangle}{180 - \the@myangle}
  \begin{pgfonlayer}{arrows}
  \draw[draw=white,line width=1.5pt](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] (x#3y#4) ;
  \ifgridon
    \draw[->,loosely dotted,line width=\dottedwidth](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] node[anchor=mid] {\href{coord: #1,#2,#3,#4}{\textbullet}} (x#3y#4) ;
  \else
    \draw[->,loosely dotted,line width=\dottedwidth](x#1y#2) to[out=\the@myangle,in=\the@inangle,relative] (x#3y#4) ;
  \fi
  \end{pgfonlayer}
}


\def\@grid{
  \gridontrue
  \renewcommand{\CourseURL}[3]{coord: ##1,##2} % "coord:" makes it look like a URI

  \begin{pgfonlayer}{grid}
  \draw[line width=0.3pt,draw=verylight] (0,0) grid [step=1]  (\value{@gridright},\value{@gridtop});
  \draw[line width=0.4pt,draw=somewhatlight] (0,0) grid [step=5] (\value{@gridright},\value{@gridtop});
   
  \foreach \i in {0,10,...,\value{@gridright}}
     \node at (\i,-4){\small \i};

  \foreach \i in {0,10,...,\value{@gridtop}}
     \node at (-5,\i){\small \i};

  \foreach \i in {0,10,...,\value{@gridright}}
     \node at (\i,\value{@gridtop}+4){\small \i};

  \foreach \i in {0,10,...,\value{@gridtop}}
     \node at (\value{@gridright}+5,\i){\small \i};

  % anchors are to allow computation of coordinates from mouse clicks in kpdf/okular:
  % latex/dvips requires non-null href box
  \node at (-5,-4) {\href{anchor: -5,-4}{\kern1sp}};
  \setcounter{@gridtop}{\value{@gridtop} + 4}
  \setcounter{@gridright}{\value{@gridright} + 5}
  \node at (\the@gridright,\the@gridtop) {\href{anchor: \the@gridright,\the@gridtop}{\kern1sp}};  
  \end{pgfonlayer}
}

%
%
%   \begin{chart}  ...  \end{chart}
%
%

\newenvironment{chart}
{ \setcounter{@diagwidth}{10 + 1 * \ratio{\textwidth}{\unit}}

  \let\halfcourse=\@halfcourse
  \let\halfcoursec=\@halfcoursec
  \let\reqhalfcourse=\@reqhalfcourse
  \let\reqhalfcoursec=\@reqhalfcoursec
  \let\opthalfcourse=\@opthalfcourse
  \let\opthalfcoursec=\@opthalfcoursec
  \let\fullcourse=\@fullcourse
  \let\fullcoursec=\@fullcoursec
  \let\reqfullcourse=\@reqfullcourse
  \let\reqfullcoursec=\@reqfullcoursec
  \let\optfullcourse=\@optfullcourse
  \let\optfullcoursec=\@optfullcoursec
  \let\mini=\@mini
  \let\text=\@text
  \let\prereq=\@prereq
  \let\prereqc=\@prereqc
  \let\coreq=\@coreq
  \let\coreqc=\@coreqc   
  \let\recomm=\@recomm
  \let\recommc=\@recommc
  \let\grid=\@grid
  \begin{tikzpicture}[x=\unit,y=\unit,>={Latex[length=4pt,fill=black]}]
  \tikzstyle{every rectangle node}=[inner xsep=1.8pt,rounded corners=2pt,inner ysep=0.5pt]
  \setcounter{@gridwidth}{(\the@diagwidth-5) / 10}
  \setcounter{@gridright}{10 * \value{@gridwidth}}
  \setcounter{@gridheight}{\thediagheight / 10}
  \setcounter{@gridtop}{10 * \value{@gridheight} }
  \useasboundingbox (0,-2) rectangle (\value{@gridright},\value{@gridtop});
}
{ 
  \end{tikzpicture}
}
%
% Changelog:
%
%  Vesrsion 6.8.0
%
%    allow for negative curvatures
%
%  Versin 6.7.0
%
%    allow for curved upward arrows
%
%  Version 6.6.0
%
%    remove code to generate \jobname.map and \jobname.sh files
%
%  Version 6.5.1
%
%    undid generation of \jobname.dat file:  SVG images (with clickable links)
%    can be generated by latest versions of pdf2svg (0.2.3) or dvisvgm (1.5.3)
%
%  Version 6.5.0
%
%    pdflatex processing now generates an auxiliary file \jobname.dat of link data
%    for use with a SVG image
%
%  Version 6.4.1
%
%    Set length=4pt for arrow tips in tikzpicture options.
%    Remove dependence on the ifthen package.
%    Generate map and cropping script only for pdf output.
%
%  Version 6.4.0
%
%    Revise arrows for tikz version 3.0.0
%
%  Version 6.3.6
%
%    Allow line breaks in \text boxes.
%
%  Version 6.3.5
%
%    Fix font usage to work with mweights.sty.
%
%  Version 6.3.4
%
%    Timetable and course code in bold for required boxes.
%
%  Version 6.3.3
%
%    Remove background colour from standalone boxes.
%    \smallersize increased to \relsize{-2}.
%
%  Version 6.3.2
%
%    Use pgf layers to keep grid below arrows below boxes (thanks to Ryan Kavanagh).
%    Add struts to stand-alone \...box commands.
%
%  Version 6.3
%
%    Allow "opt" course boxes (with dotted outlines).
%
%  Version 6.2
%
%    Allow for multi-line "timetable" arguments by using nested tabular environments.
%
%  Version 6.1.0
%
%    Added commands to specify background color of non-mini course boxes.
%
%  Version 6.0.6
%
%    Provide \textbullet at mid-point of edges when grid is on.
%
%  Version 6.0.5
%
%    Changed TARGET attribute in AREA outputs to "new".
%    New configuration command \baselineAdj.
%
%  Version 6.0.4
%
%    Added missing initializations of @dy to curved...  macros.
%
%  Version 6.0.3
%
%    Added required ALT tag to AREA outputs.
%
%  Version 6.0
%  Version 5.7
%
%    added implementation details to documentation
%    generated script now only crops the chart image
%
%  Version 5.6
%  Version 5.5
%
%    version increased to keep pace with previewer/vprerex
%
%  Version 5.4
%
%    code clean-up
%
%  Version 5.3
%
%    produces an image-generating script in \jobname.sh
%
%  Version 5.2
%
%    use \grid and \foreach (tikz) instead of \multido
%    half-course boxes now have a minimum height (5 units) to improve uniformity
%
%  Version 5.1
%
%    generates image-map data in \jobname_n.html for nth chart when n>1 
%
%  Version 5.0
%
%    also generates \jobname.html with image-map data for all node URLs
%    new configuration commands \dpi and \PixelsPerUnit
%    default \unit length adjusted to give 10 pixels per coordinate unit at 125 dpi
%
%  Version 4.4
%
%    increase ysep parameter to 1.8pt to separate course-code or text and arrow tails for minis 
%    and text boxes
%
%  Version 4.3
%
%    introduce \smallersize configuration command
%
%  Version 4.2
%
%    using tinting with xcolor package to ease background-color changes 
%
%  Version 4.1
%
%  Version 4.0
%
%   Implement the \text command to place a line of text (centered at the coordinates) in a chart
%
%  Version 3.8.1:
%
%   adjust arraystretch factors to work with long-ascender fonts such as Futura
%   adjust inner sep parameters to work with oblique/italic fonts
%   remove workaround for pgf-1.10 bug described at
%      http://sourceforge.net/forum/forum.php?thread_id=1621660&forum_id=477363
%   require version 1.18 (or later) of pgf
%
%  Version 3.8:
%
%    require version 1.10 (or later) of pgf
%
%  Version 3.7:
%
%    anchor nodes must be non-null for latex/dvips
%
%  Version 3.6:
%
%    first pgf-based version
%
%  Version 3.5:
%  Version 3.4:
%
%    introduce arrow borders to improve the appearance of crossing arrows
%    change default widths to artifacts created when arrow borders 
%      occlude box boundaries
%
%  Version 3.3:
%
%    arrows (as well as course boxes and minis) are hyperlinked with coordinate URIs
%
%  Version 3.2:
%
%  Version 3.1:
%
%  Version 3.0:
%
%   "anchor" hyperlinks are added to coordinate grid to allow computation of
%      chart coordinates at mouse clicks 
%
%  Version 2.0:
%
%    CourseURL now takes 3 arguments
%    box/mini coordinates displayed in (some) PDF viewers when grid on
%
%  Version 1.0.2:
%
%    using \relsize{-3} rather than \scriptsize
%    using \textsf in \lightbox and \boldbox
%
%  Version 1.0.1:
%
%    using \RequirePackage rather than \usepackage (suggested by Herbert Voss)
%