example.tex

\documentclass[]{article}

\usepackage{lmodern}


\usepackage{amssymb,amsmath}
\usepackage{ifxetex,ifluatex}
\usepackage{fixltx2e} % provides \textsubscript

\ifnum 0\ifxetex 1\fi\ifluatex 1\fi=0 % if pdftex
  \usepackage[T1]{fontenc}
  \usepackage[utf8]{inputenc}

  
\else % if luatex or xelatex

  \ifxetex
    \usepackage{mathspec}
    \usepackage{xltxtra,xunicode}
  \else
    \usepackage{fontspec}
  \fi
  \defaultfontfeatures{Mapping=tex-text,Scale=MatchLowercase}
  \newcommand{\euro}{€}




\fi

% use upquote if available, for straight quotes in verbatim environments
\IfFileExists{upquote.sty}{\usepackage{upquote}}{}
% use microtype if available
\IfFileExists{microtype.sty}{%
\usepackage{microtype}
\UseMicrotypeSet[protrusion]{basicmath} % disable protrusion for tt fonts
}{}




\usepackage[style=numeric,backend=bibtex,natbib]{biblatex}
\addbibresource{references.bib}







\ifxetex
  \usepackage[setpagesize=false, % page size defined by xetex
              unicode=false, % unicode breaks when used with xetex
              xetex]{hyperref}
\else
  \usepackage[unicode=true]{hyperref}
\fi

\hypersetup{breaklinks=true,
            bookmarks=true,
            pdfauthor={},
            pdftitle={A Module Type System for Embedded System Synthesis},
            colorlinks=true,
            citecolor=blue,
            urlcolor=blue,
            linkcolor=magenta,
            pdfborder={0 0 0}}
\urlstyle{same}  % don't use monospace font for urls



\setlength{\parindent}{0pt}
\setlength{\parskip}{6pt plus 2pt minus 1pt}
\setlength{\emergencystretch}{3em}  % prevent overfull lines

\setcounter{secnumdepth}{0}


\title{A Module Type System for Embedded System Synthesis}

\author{Rohit Ramesh}

\date{}

\usepackage{tikz}
%\usetikzlibrary{
%  ,graphs
%  ,graphdrawing}
%\usegdlibrary{trees,layered}
\usepackage{todonotes}
\usepackage{module-type-diagram}

\let\oldtodo\todo

\DeclareDocumentCommand \todo {D[]{} +m} {
  \oldtodo[size=\tiny,#1]{\emph{Todo:} #2}
}

\begin{document}


\resizebox{\columnwidth}{!}{
\begin{modulediagram}
  \module(modfoo){bar}{
    \port            <east>   (etest)  {eport};
    \port[supprequ]  <east>   (etest2) {eportd};
    \port            <north>  (ntest)  {nport};
    \port            <north>  (ntest2) {nport2};
    \port[supp]      <west>   (wtest)  {wport};
    \port[requ]      <west>   (wtest2) {westport};
    \port            <south>  (stest)  {sport};
    \port            <south>  (stest2) {spor3t};
  };

  
  \node[draw,right=of modfoo] (testnode) {testnode};

  \fittedmodule[thick][outer sep = 1cm]
  <modfoo,testnode> (testfit) {test label $\aleph$} {
    \port            <east>   (eteest)  {eport};
    \port[supprequ]  <east>   (eteset2) {eportd};
    \port            <north>  (nteset)  {nport};
    \port            <north>  (nteset2) {nport2};
    \port[supp]      <west>   (wteset)  {wport};
    \port[requ]      <west>   (wteset2) {westport};
    \port            <south>  (steset)  {sport};
  };



\end{modulediagram}
} 

\end{document}

module-type-diagram.sty

% A Latex Package for creating Module Type System Block 
% Diagrams 

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{module-type-system}

\RequirePackage{tikz}
\RequirePackage{ifthen}
\RequirePackage{xparse}

% TODO : I have no clue which of these libraries I actually need :V if anyone 
%        wants to cull the useless ones I'd appreciate it. 
\usetikzlibrary{
  graphs,
  shapes,
  calc,
  intersections,
  through,
  fit,
  backgrounds,
  positioning,
  arrows,%
  shapes.misc,% wg. rounded rectangle
  shapes.arrows,%
  chains,%
  matrix,%
  scopes,%
  decorations.pathmorphing,% /pgf/decoration/random steps | erste Graphik
  shadows,%
  fixedpointarithmetic
}

% ### Default Styles ###

\tikzset{
  % The depth of the notches for the various port shapes
  ,notch depth/.initial = 2pt
  % The ammount of buffer space to have on either side of a module's
  % center box to leave aside for port placement. 
  ,module center overrun/.initial = 15pt
}

% Styles applied to every mtd diagram
\tikzstyle{mtd-diagram}=[
  remember picture
]

% The default style for the wrapper object that allows MTD modules to 
% be positioned as single objects. 
\tikzstyle{mtd-module-wrap}=[
  ,inner sep = 0pt
  ,outer sep = 0pt
]

% The style for the center box of an MTD module
\tikzstyle{mtd-module-center}=[
  ,black
  ,draw
  ,rounded corners
  ,inner sep = 3pt
  ,align = center
]

% Default Style for the boxes that contain a set of ports
\tikzstyle{mtd-portbox}=[
  ,inner sep = 0pt
  ,outer sep = 0pt
  ,node distance = 4pt
]

% Default style for a single port 
\tikzstyle{mtd-port}=[
  ,draw
  ,inner sep = 3pt
  ,align = center
]

\tikzstyle{mtd-fit-module-wrap}=[
  ,mtd-module-wrap
]

\tikzstyle{mtd-fit-innerfit}=[
  ,inner sep = 0pt
  ,outer sep = 0pt
]

\tikzstyle{mtd-fit-label}=[
  ,node distance = 4pt
  ,parent-innerfit/.style={above=of ##1.north}
  ,anchor=south
]

\tikzstyle{mtd-fit-module-center}=[
  ,mtd-module-center
]

\tikzstyle{mtd-fit-portbox}=[
]

\tikzstyle{supplier}=[
  port-type=supply
]

\tikzstyle{requester}=[
  port-type=request
]

\tikzstyle{supplier requester}=[
  port-type=supplyrequest
]

\tikzstyle{normal port}=[
  port-type=normal
]

% Shortcut style options, these are just light aliases to other styles that 
% are easier to type out

\tikzstyle{norm}=[normal port]
\tikzstyle{supp}=[supplier]
\tikzstyle{requ}=[requester]
\tikzstyle{supprequ}=[supplier requester]
\tikzstyle{rc}=[rounded coreners]

% Directional Style Options, if you need to change these for styling 
% purposes you are doing it wrong. They mostly exist to provide shims for 
% tikz workarounds, and to cleanly encapsulate certains heirarchies. 

\tikzstyle{mtd-portbox-north}=[
  ,mtd-portbox
]

\tikzstyle{mtd-portbox-south}=[
  ,mtd-portbox
]

\tikzstyle{mtd-portbox-east}=[
  ,mtd-portbox
]

\tikzstyle{mtd-portbox-west}=[
  ,mtd-portbox
]


\tikzstyle{mtd-fit-portbox-north}=[
  ,mtd-portbox-north
  ,mtd-fit-portbox
]

\tikzstyle{mtd-fit-portbox-south}=[
  ,mtd-portbox-south
  ,mtd-fit-portbox
]

\tikzstyle{mtd-fit-portbox-east}=[
  ,mtd-portbox-east
  ,mtd-fit-portbox
]

\tikzstyle{mtd-fit-portbox-west}=[
  ,mtd-portbox-west
  ,mtd-fit-portbox
]

\tikzstyle{mtd-port-north}=[
  ,mtd-port
]

\tikzstyle{mtd-port-south}=[
  ,mtd-port
]

\tikzstyle{mtd-port-east}=[
  ,mtd-port
]

\tikzstyle{mtd-port-west}=[
  ,mtd-port
]

% ### Do Not Edit Below This Line ###

% If flags for modifying Ports
% Directional Flags 
\newif\if@isnorth
\newif\if@issouth
\newif\if@iseast
\newif\if@iswest

\tikzset{
  % Default settings the user should not be able to override
  % (at least if they don't edit the bits they're not supposed to edit)
  ,mtd diagram/.append style={
    ,remember picture
  }
  ,mtd-portbox-north/.append style={
    ,anchor=south
  }
  ,mtd-portbox-south/.append style={
    ,anchor=north
  }
  ,mtd-portbox-east/.append style={
    ,anchor=west
  }
  ,mtd-portbox-west/.append style={
    ,anchor=east
  }
  ,mtd-port-east/.append style={
    ,previous-port/.style={below=of ##1.sw,anchor=nw}
  }
  ,mtd-port-west/.append style={
    ,previous-port/.style={below=of ##1.se,anchor=ne}
  }
  ,mtd-port-north/.append style={
    ,previous-port/.style={right=of ##1.se,anchor=sw}
  }
  ,mtd-port-south/.append style={
    ,previous-port/.style={right=of ##1.ne,anchor=nw}
  }
  % Boolean flags for direction
  ,port-info/is north/.initial = false
  ,port-info/is north/.is if=@isnorth
  ,port-info/is north/.default = false
  ,port-info/is south/.initial = false
  ,port-info/is south/.is if=@issouth
  ,port-info/is south/.default = false
  ,port-info/is east/.initial = false
  ,port-info/is east/.is if=@iseast
  ,port-info/is east/.default = false
  ,port-info/is west/.initial = false 
  ,port-info/is west/.is if=@iswest
  ,port-info/is west/.default = false 
  % Switch for Direction and Flag settings
  ,port-dir/.is choice
  ,port-dir/north/.style={
    ,port-info/is north = true
    ,port-info/is south = false
    ,port-info/is east = false
    ,port-info/is west = false
    ,mtd-port-north
  }
  ,port-dir/south/.style={
    ,port-info/is north = false
    ,port-info/is south=true
    ,port-info/is east = false
    ,port-info/is west = false
    ,mtd-port-south
  }
  ,port-dir/west/.style={
    ,port-info/is north = false
    ,port-info/is south = false
    ,port-info/is east = false
    ,port-info/is west = true
    ,mtd-port-west
  }
  ,port-dir/east/.style={
    ,port-info/is north = false
    ,port-info/is south = false
    ,port-info/is east = true
    ,port-info/is west = false
    ,mtd-port-east
  }
  ,port-dir/reset/.style={
    ,port-info/is north = false
    ,port-info/is south = false
    ,port-info/is east = false
    ,port-info/is west = false
  }
  ,port-type/.is choice
  ,port-type/.initial = normal 
  ,port-type/normal/.style={
    ,normshape
  }
  ,port-type/supply/.style={
    ,suppshape
  }
  ,port-type/request/.style={
    ,requshape
  }
  ,port-type/supplyrequest/.style={
    ,supprequshape
  }
}

% Advance a point in direction theta for distance r 
% #1 = x
% #2 = y
% #3 = theta 
% #4 = r
\DeclareDocumentCommand \@advancepoint {m m m m}{
  \pgfmathsetmacro{\mts@xo}{sin(#3) * #4}
  \pgfmathsetmacro{\mts@yo}{cos(#3) * #4}
  \pgfmathsetmacro{#1}{#1 + \mts@xo}
  \pgfmathsetmacro{#2}{#2 + \mts@yo}
}

% Copy a point into a pair of new macros.
% #1 = destx
% #2 = desty
% #3 = srcx
% #4 = srcy 
\DeclareDocumentCommand \@copypoint {m m m m}{
  \pgfmathsetmacro{#1}{#3}
  \pgfmathsetmacro{#2}{#4}
}

% A command to draw a normal ine between two points 
% as poart of a PGF Backgroun Path process, assumes
% that a the startx and y are where the path is at 
% the beginning of the command.
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@normline {m m m m}{
  \pgfpathlineto{\pgfpoint{#3}{#4}}
}

% returns the connection point for each side of a normal block
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@normconn {m m m m}{
  % Initial setup 
  \pgfmathsetmacro{\mts@xa}{#1}
  \pgfmathsetmacro{\mts@ya}{#2}
  \pgfmathsetmacro{\mts@xb}{#3}
  \pgfmathsetmacro{\mts@yb}{#4}
  % xc,yc := the point in the middle of the line
  \pgfmathsetmacro{\mts@xc}{(\mts@xa + \mts@xb) * 0.5}
  \pgfmathsetmacro{\mts@yc}{(\mts@ya + \mts@yb) * 0.5}
  % Actualize point
  \pgfpoint{\mts@xc}{\mts@yc}
}

% Draw the bowed out line for supplires in the correct
% direction, assumes that the line is going counter clockwise.
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@suppline {m m m m}{
  % Initial setup 
  \pgfmathsetmacro{\mts@xa}{#1}
  \pgfmathsetmacro{\mts@ya}{#2}
  \pgfmathsetmacro{\mts@xb}{#3}
  \pgfmathsetmacro{\mts@yb}{#4}
  % Calculate key constants / gather variables
  \pgfkeysgetvalue{/tikz/notch depth}{\mts@notchdepth}
  % Calculate key constants / gather variables
  % theta_a := the angle along the path of the line -
  \pgfmathsetmacro{\mts@thetaa}{atan2(\mts@yb - \mts@ya,\mts@xb - \mts@xa)}
  % theta_b := the angle perpendicular to the path of the line 
  \pgfmathsetmacro{\mts@thetab}{\mts@thetaa - 90}
  % Get points for current line 
  \@copypoint{\mts@xc}{\mts@yc}{\mts@xa}{\mts@ya}
  \@advancepoint{\mts@xc}{\mts@yc}{\mts@thetaa}{\mts@notchdepth}
  \@advancepoint{\mts@xc}{\mts@yc}{\mts@thetab}{\mts@notchdepth}
  \@copypoint{\mts@xd}{\mts@yd}{\mts@xb}{\mts@yb}
  \@advancepoint{\mts@xd}{\mts@yd}{\mts@thetaa}{-\mts@notchdepth}
  \@advancepoint{\mts@xd}{\mts@yd}{\mts@thetab}{\mts@notchdepth}
  % Actualize Line 
  \pgfpathlineto{\pgfpoint{\mts@xc}{\mts@yc}}
  \pgfpathlineto{\pgfpoint{\mts@xd}{\mts@yd}}
  \pgfpathlineto{\pgfpoint{\mts@xb}{\mts@yb}}
}

% returns the connection point for each side of a supplier
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@suppconn {m m m m}{
  % Initial setup 
  \pgfmathsetmacro{\mts@xa}{#1}
  \pgfmathsetmacro{\mts@ya}{#2}
  \pgfmathsetmacro{\mts@xb}{#3}
  \pgfmathsetmacro{\mts@yb}{#4}
  % Calculate key constants / gather variables
  \pgfkeysgetvalue{/tikz/notch depth}{\mts@notchdepth}
  % Calculate key constants / gather variables
  % theta_a := the angle along the path of the line -
  \pgfmathsetmacro{\mts@thetaa}{atan2(\mts@yb - \mts@ya,\mts@xb - \mts@xa)}
  % theta_b := the angle perpendicular to the path of the line 
  \pgfmathsetmacro{\mts@thetab}{\mts@thetaa - 90}
  % xc,yc := the point in the middle of the line
  \pgfmathsetmacro{\mts@xc}{(\mts@xa + \mts@xb) * 0.5}
  \pgfmathsetmacro{\mts@yc}{(\mts@ya + \mts@yb) * 0.5}
  % move center point correctly
  \@advancepoint{\mts@xc}{\mts@yc}{\mts@thetab}{\mts@notchdepth}
  % Actualize point
  \pgfpoint{\mts@xc}{\mts@yc}
}

% Draw the bowed in line for requesters in the correct
% direction, assumes that the line is going counter clockwise.
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@requline {m m m m}{
  % Initial setup 
  \pgfmathsetmacro{\mts@xa}{#1}
  \pgfmathsetmacro{\mts@ya}{#2}
  \pgfmathsetmacro{\mts@xb}{#3}
  \pgfmathsetmacro{\mts@yb}{#4}
  % Calculate key constants / gather variables
  \pgfkeysgetvalue{/tikz/notch depth}{\mts@notchdepth}
  % theta_a := the angle along the path of the line 
  \pgfmathsetmacro{\mts@thetaa}{atan2(\mts@yb - \mts@ya,\mts@xb - \mts@xa)} 
  % theta_b := the angle perpendicular to the path of the line 
  \pgfmathsetmacro{\mts@thetab}{\mts@thetaa - 90}
  % Get points for current line 
  \@copypoint{\mts@xc}{\mts@yc}{\mts@xa}{\mts@ya}
  \@advancepoint{\mts@xc}{\mts@yc}{\mts@thetab}{\mts@notchdepth}
  \@copypoint{\mts@xd}{\mts@yd}{\mts@xa}{\mts@ya}
  \@advancepoint{\mts@xd}{\mts@yd}{\mts@thetaa}{\mts@notchdepth}
  \@copypoint{\mts@xe}{\mts@ye}{\mts@xb}{\mts@yb}
  \@advancepoint{\mts@xe}{\mts@ye}{\mts@thetaa}{-\mts@notchdepth}
  \@copypoint{\mts@xf}{\mts@yf}{\mts@xb}{\mts@yb}
  \@advancepoint{\mts@xf}{\mts@yf}{\mts@thetab}{\mts@notchdepth}
  % Actualize Line 
  \pgfpathlineto{\pgfpoint{\mts@xc}{\mts@yc}}
  \pgfpathlineto{\pgfpoint{\mts@xd}{\mts@yd}}
  \pgfpathlineto{\pgfpoint{\mts@xe}{\mts@ye}}
  \pgfpathlineto{\pgfpoint{\mts@xf}{\mts@yf}}
  \pgfpathlineto{\pgfpoint{\mts@xb}{\mts@yb}}
}

% returns the connection point for each side of a requester
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@requconn {m m m m}{
  % Initial setup 
  \pgfmathsetmacro{\mts@xa}{#1}
  \pgfmathsetmacro{\mts@ya}{#2}
  \pgfmathsetmacro{\mts@xb}{#3}
  \pgfmathsetmacro{\mts@yb}{#4}
  % Calculate key constants / gather variables
  \pgfkeysgetvalue{/tikz/notch depth}{\mts@notchdepth}
  % Calculate key constants / gather variables
  % theta_a := the angle along the path of the line -
  \pgfmathsetmacro{\mts@thetaa}{atan2(\mts@yb - \mts@ya,\mts@xb - \mts@xa)}
  % theta_b := the angle perpendicular to the path of the line 
  \pgfmathsetmacro{\mts@thetab}{\mts@thetaa - 90}
  % xc,yc := the point in the middle of the line
  \pgfmathsetmacro{\mts@xc}{(\mts@xa + \mts@xb) * 0.5}
  \pgfmathsetmacro{\mts@yc}{(\mts@ya + \mts@yb) * 0.5}
  % Actualize point
  \pgfpoint{\mts@xc}{\mts@yc}
}

% Draw the wavy line for supp/receivers in the correct
% direction, assumes that the line is going counter clockwise.
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@supprequline {m m m m}{
  % Initial setup 
  \pgfmathsetmacro{\mts@xa}{#1}
  \pgfmathsetmacro{\mts@ya}{#2}
  \pgfmathsetmacro{\mts@xb}{#3}
  \pgfmathsetmacro{\mts@yb}{#4}
  % Calculate key constants / gather variables
  \pgfkeysgetvalue{/tikz/notch depth}{\mts@notchdepth}
  % theta_a := the angle along the path of the line 
  \pgfmathsetmacro{\mts@thetaa}{atan2(\mts@yb - \mts@ya,\mts@xb - \mts@xa)} 
  % theta_b := the angle perpendicular to the path of the line 
  \pgfmathsetmacro{\mts@thetab}{\mts@thetaa - 90}
  % hnd := half the notch depth 
  \pgfmathsetmacro{\mts@hnd}{\mts@notchdepth * 0.5}
  % xc,yc := the point in the middle of the line
  \pgfmathsetmacro{\mts@xc}{(\mts@xa + \mts@xb) * 0.5}
  \pgfmathsetmacro{\mts@yc}{(\mts@ya + \mts@yb) * 0.5}
  % Get points for current line 
  \@copypoint{\mts@xd}{\mts@yd}{\mts@xa}{\mts@ya}
  \@advancepoint{\mts@xd}{\mts@yd}{\mts@thetab}{\mts@notchdepth}
  \@copypoint{\mts@xe}{\mts@ye}{\mts@xa}{\mts@ya}
  \@advancepoint{\mts@xe}{\mts@ye}{\mts@thetaa}{\mts@notchdepth}
  \@copypoint{\mts@xf}{\mts@yf}{\mts@xc}{\mts@yc}
  \@advancepoint{\mts@xf}{\mts@yf}{\mts@thetaa}{-\mts@hnd}
  \@copypoint{\mts@xg}{\mts@yg}{\mts@xc}{\mts@yc}
  \@advancepoint{\mts@xg}{\mts@yg}{\mts@thetaa}{\mts@hnd}
  \@advancepoint{\mts@xg}{\mts@yg}{\mts@thetab}{\mts@notchdepth}
  \@copypoint{\mts@xh}{\mts@yh}{\mts@xb}{\mts@yb}
  \@advancepoint{\mts@xh}{\mts@yh}{\mts@thetaa}{-\mts@notchdepth}
  \@advancepoint{\mts@xh}{\mts@yh}{\mts@thetab}{\mts@notchdepth}
  % Actualize Line 
  \pgfpathlineto{\pgfpoint{\mts@xd}{\mts@yd}}
  \pgfpathlineto{\pgfpoint{\mts@xe}{\mts@ye}}
  \pgfpathlineto{\pgfpoint{\mts@xf}{\mts@yf}}
  \pgfpathlineto{\pgfpoint{\mts@xg}{\mts@yg}}
  \pgfpathlineto{\pgfpoint{\mts@xh}{\mts@yh}}
  \pgfpathlineto{\pgfpoint{\mts@xb}{\mts@yb}}
}

% returns the connection point for each side of a supplier/requester
% #1 = x1
% #2 = y1
% #3 = x2 
% #4 = y2 
\DeclareDocumentCommand \@supprequconn {m m m m}{
  % Initial setup 
  \pgfmathsetmacro{\mts@xa}{#1}
  \pgfmathsetmacro{\mts@ya}{#2}
  \pgfmathsetmacro{\mts@xb}{#3}
  \pgfmathsetmacro{\mts@yb}{#4}
  % Calculate key constants / gather variables
  \pgfkeysgetvalue{/tikz/notch depth}{\mts@notchdepth}
  % Calculate key constants / gather variables
  % theta_a := the angle along the path of the line -
  \pgfmathsetmacro{\mts@thetaa}{atan2(\mts@yb - \mts@ya,\mts@xb - \mts@xa)}
  % theta_b := the angle perpendicular to the path of the line 
  \pgfmathsetmacro{\mts@thetab}{\mts@thetaa - 90}
  % xc,yc := the point in the middle of the line
  \pgfmathsetmacro{\mts@xc}{(\mts@xa + \mts@xb) * 0.5}
  \pgfmathsetmacro{\mts@yc}{(\mts@ya + \mts@yb) * 0.5}
  % move center point correctly
  \@advancepoint{\mts@xc}{\mts@yc}{\mts@thetab}{(0.5 * \mts@notchdepth)}
  % Actualize point
  \pgfpoint{\mts@xc}{\mts@yc}
}

% #1 = shape name
% #2 = special line command 
% #3 = special conn point command
\DeclareDocumentCommand \@initportshape {m m m} {
  \pgfdeclareshape{#1}{
    \inheritsavedanchors[from=rectangle] % this is nearly a rectangle
    \inheritanchorborder[from=rectangle]
    \inheritanchor[from=rectangle]{center}
    \inheritanchor[from=rectangle]{north}
    \inheritanchor[from=rectangle]{south}
    \inheritanchor[from=rectangle]{west}
    \inheritanchor[from=rectangle]{east}
    \backgroundpath{
      % store lower right in xa/ya and upper right in xb/yb
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      % construct main path
      \pgfpathmoveto{\pgfpoint{\pgf@xa}{\pgf@ya}}
      \if@iswest
        #2{\pgf@xa}{\pgf@ya}{\pgf@xa}{\pgf@yb}
      \else
        \@normline{\pgf@xa}{\pgf@ya}{\pgf@xa}{\pgf@yb}
      \fi
      \if@isnorth
        #2{\pgf@xa}{\pgf@yb}{\pgf@xb}{\pgf@yb}
      \else
        \@normline{\pgf@xa}{\pgf@yb}{\pgf@xb}{\pgf@yb}
      \fi
      \if@iseast
        #2{\pgf@xb}{\pgf@yb}{\pgf@xb}{\pgf@ya}
      \else
        \@normline{\pgf@xb}{\pgf@yb}{\pgf@xb}{\pgf@ya}
      \fi
      \if@issouth
        #2{\pgf@xb}{\pgf@ya}{\pgf@xa}{\pgf@ya}
      \else
        \@normline{\pgf@xb}{\pgf@ya}{\pgf@xa}{\pgf@ya}
      \fi
      \pgfpathclose
    }
    % Anchors defined by sensible people in a language that is
    % only the devil's 3rd cousin
    \anchor{northconn}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      #3{\pgf@xa}{\pgf@yb}{\pgf@xb}{\pgf@yb}
    }
    \anchor{southconn}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      #3{\pgf@xb}{\pgf@ya}{\pgf@xa}{\pgf@ya}
    }
    \anchor{westconn}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      #3{\pgf@xa}{\pgf@ya}{\pgf@xa}{\pgf@yb}
    }
    \anchor{eastconn}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      #3{\pgf@xb}{\pgf@yb}{\pgf@xb}{\pgf@ya}
    }
    \anchor{nw}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      \pgfpoint{\pgf@xa}{\pgf@yb}
    } 
    \anchor{ne}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      \pgfpoint{\pgf@xb}{\pgf@yb}
    } 
    \anchor{sw}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      \pgfpoint{\pgf@xa}{\pgf@ya}
    } 
    \anchor{se}{
      \southwest \pgf@xa=\pgf@x \pgf@ya=\pgf@y
      \northeast \pgf@xb=\pgf@x \pgf@yb=\pgf@y
      \pgfpoint{\pgf@xb}{\pgf@ya}
    } 
  }
}

% Initialize the various port types
\@initportshape{normshape}{\@normline}{\@normconn}
\@initportshape{suppshape}{\@suppline}{\@suppconn}
\@initportshape{requshape}{\@requline}{\@requconn}
\@initportshape{supprequshape}{\@supprequline}{\@supprequconn}

\ExplSyntaxOn

% some helper / wrapper commands around \pgfplacenodelater
% #1 = identifier for nodes to be placed later
% #2 = elements to be placed 
\DeclareDocumentCommand \@placenodelater {r() +m}{
  \cs_new_protected:cpn {mtd@#1-save}
   {
    % Save Necessary Registers
    \cs_gset_eq:cN {mtd@#1-name} \pgfpositionnodelatername
    \cs_gset_eq:cN {mtd@#1-minx} \pgfpositionnodelaterminx
    \cs_gset_eq:cN {mtd@#1-miny} \pgfpositionnodelaterminy
    \cs_gset_eq:cN {mtd@#1-maxx} \pgfpositionnodelatermaxx
    \cs_gset_eq:cN {mtd@#1-maxy} \pgfpositionnodelatermaxy
    \box_if_exist:cF{mtd@#1-box} {\box_new:c {mtd@#1-box}}
    \box_gset_eq:cN {mtd@#1-box} \pgfpositionnodelaterbox
    % Calculate Length and Width as well
    \pgfmathsetmacro{\mtd@tempwid}
      {\pgfpositionnodelatermaxx - \pgfpositionnodelaterminx}
    \pgfmathsetmacro{\mtd@temphei}
      {\pgfpositionnodelatermaxy - \pgfpositionnodelaterminy}
    \cs_gset_eq:cN {mtd@#1-height} \mtd@temphei
    \cs_gset_eq:cN {mtd@#1-width} \mtd@tempwid
  }
  {
    \exp_args:Nc \pgfpositionnodelater {mtd@#1-save} #2
  }
}

% #1 = identifier for nodes already saved by \@placenodelater
% #2 = location for the node to be placed at
\DeclareDocumentCommand \@placenodenow {r() +m}{
  \cs_gset_eq:Nc \pgfpositionnodelatername {mtd@#1-name}
  \cs_gset_eq:Nc \pgfpositionnodelaterminx {mtd@#1-minx}
  \cs_gset_eq:Nc \pgfpositionnodelaterminy {mtd@#1-miny}
  \cs_gset_eq:Nc \pgfpositionnodelatermaxx {mtd@#1-maxx}
  \cs_gset_eq:Nc \pgfpositionnodelatermaxy {mtd@#1-maxy}
  \box_gset_eq:Nc \pgfpositionnodelaterbox {mtd@#1-box}
  \pgfpositionnodenow{#2}
}


% Provide Outer Modular diagram environment
% #1 = options to pass to tikz
\DeclareDocumentEnvironment{modulediagram}{D[]{}}
{
  \begin{tikzpicture}[mtd-diagram,#1]
}
{
  \end{tikzpicture}
}

% The specifier for a module that contains a number of ports
% #1 = outerbox styles
% #2 = innerbox styles 
% #3 = outerbox name 
% #4 = innerbox content
% #5 = port specifiers
\DeclareDocumentCommand \module {D[]{} D[]{} r() +m +m}{
  
  \node[mtd-module-wrap,#1] (#3) {
    \tikz[]{
      % Initialize Local Variables 
      \def\currentmodulename{#3}
      \tikzstyle{local-port-style}=[]
      % Initialise Data Structures and the like to store ports
      \seq_clear_new:c {#3-north-ports}
      \seq_clear_new:c {#3-south-ports}
      \seq_clear_new:c {#3-east-ports}
      \seq_clear_new:c {#3-west-ports}
      \seq_clear_new:c {#3-port-cleanup}
      % Run port specifiers to store ports into relevant structures
      #5
      % Construct each side's portboxes and save into temporary scopes
      \@placenodelater(#3-north-portbox){
        \node[mtd-portbox-north](#3-portbox-north){
         % Local variables 
          \let\prevnode\undefined
          % Get all the ports from the list
          \tikz[remember~picture]{ \seq_use:cn {#3-north-ports}{;} }
       };
      }
      \@placenodelater(#3-south-portbox){
        \node[mtd-portbox-south](#3-portbox-south){
         % Local variables 
          \let\prevnode\undefined
          % Get all the ports from the list
          \tikz[]{ \seq_use:cn {#3-south-ports}{;} }
       };
      }
      \@placenodelater(#3-east-portbox){
        \node[mtd-portbox-east](#3-portbox-east){
         % Local variables 
          \let\prevnode\undefined
          % Get all the ports from the list
          \tikz[]{ \seq_use:cn {#3-east-ports}{;} }
       };
      }
      \@placenodelater(#3-west-portbox){
        \node[mtd-portbox-west](#3-portbox-west){
         % Local variables 
          \let\prevnode\undefined
          % Get all the ports from the list
          \tikz[]{ \seq_use:cn {#3-west-ports}{;} }
       };
      }
      % Construct the central box using information on each portboxes's 
      % length and width
      \pgfkeysgetvalue{/tikz/module~center~overrun}{\mtd@mco}

      \pgfmathsetmacro{\mtd@centralwidth}
      {max(\use:c{mtd@#3-north-portbox-width}
          ,\use:c{mtd@#3-south-portbox-width}) + \mtd@mco}

      \pgfmathsetmacro{\mtd@centralheight}
      {max(\use:c{mtd@#3-east-portbox-height}
          ,\use:c{mtd@#3-west-portbox-height}) + \mtd@mco}

      \node[
        ,mtd-module-center
        ,minimum~width=\mtd@centralwidth
        ,minimum~height=\mtd@centralheight
        ,#2
      ](#3-center){#4};
      % Place port boxes relative to the central box
      \@placenodenow(#3-north-portbox){\pgfpointanchor{#3-center}{north}}
      \@placenodenow(#3-south-portbox){\pgfpointanchor{#3-center}{south}}
      \@placenodenow(#3-east-portbox){\pgfpointanchor{#3-center}{east}}
      \@placenodenow(#3-west-portbox){\pgfpointanchor{#3-center}{west}}
      % Active any cleanup code that's to be run after placement
      \seq_use:cn {#3-port-cleanup}{}
    }
  };
}

% The command to create a fit module, which will be placed around a 
% set of elements. 
% #1 = Styles to be exported to every element inside the fitted module. 
%      Should not have position specifiers or anything that will 'draw' or 
%      'fill' as those will be applied to everything from the top down. 
% #2 = Styles to be exported to the innerfit box, meant for things like 
%      transperancies and borders. All other styles can be added in with the 
%      port specifiers using the local name information. 
% #3 = Tikz elements to fit around 
% #4 = Fit module name 
% #5 = Label content
% #6 = port specifiers
\DeclareDocumentCommand \fittedmodule { D[]{} D[]{} r<> r() +m +m}{
  % Set local variables
  \def\currentmodulename{#4}
  \tikzstyle{local-port-style}=[#1]
  \tikzstyle{#4-label-style}=[]
  % Gather elements to fit around into list
  \seq_clear_new:c {#4-fit-elements}
  \seq_set_from_clist:cn {#4-fit-elements} {#3}
  % Initialise Data Structures and the like to store ports
  \seq_clear_new:c {#4-north-ports}
  \seq_clear_new:c {#4-south-ports}
  \seq_clear_new:c {#4-east-ports}
  \seq_clear_new:c {#4-west-ports}
  \seq_clear_new:c {#4-port-cleanup}
  % Run port specifiers to store ports into relevant structures
  #6
  % Place the inner fit node
  \node[
    ,mtd-fit-innerfit
    ,fit=(\seq_use:cn {#4-fit-elements} {)(})
    ,#1
    ,#2
  ] (#4-innerfit){};
  % Place the label above the inner fitted node
  \node[
    ,mtd-fit-label
    ,parent-innerfit=#4-innerfit
    ,#1
    ,#4-label-style
  ](#4-label){#5};
  % Construct each side's portboxes and save into temporary scopes
  \@placenodelater(#4-north-portbox){
    \node[mtd-fit-portbox-north](#4-portbox-north){
     % Local variables 
      \let\prevnode\undefined
      % Get all the ports from the list
      \tikz[#1]{ \seq_use:cn {#4-north-ports}{;} }
   };
  }
  \@placenodelater(#4-south-portbox){
    \node[mtd-fit-portbox-south](#4-portbox-south){
     % Local variables 
      \let\prevnode\undefined
      % Get all the ports from the list
      \tikz[#1]{ \seq_use:cn {#4-south-ports}{;} }
   };
  }
  \@placenodelater(#4-east-portbox){
    \node[mtd-fit-portbox-east](#4-portbox-east){
     % Local variables 
      \let\prevnode\undefined
      % Get all the ports from the list
      \tikz[#1]{ \seq_use:cn {#4-east-ports}{;} }
   };
  }
  \@placenodelater(#4-west-portbox){
    \node[mtd-fit-portbox-west](#4-portbox-west){
     % Local variables 
      \let\prevnode\undefined
      % Get all the ports from the list
      \tikz[#1]{ \seq_use:cn {#4-west-ports}{;} }
   };
  }
  % Construct the central box using information on each portboxes's 
  % length and width
  \pgfkeysgetvalue{/tikz/module~center~overrun}{\mtd@mco}

  \pgfmathsetmacro{\mtd@centralwidth}
  {max(\use:c{mtd@#4-north-portbox-width}
      ,\use:c{mtd@#4-south-portbox-width}) + \mtd@mco}

  \pgfmathsetmacro{\mtd@centralheight}
  {max(\use:c{mtd@#4-east-portbox-height}
      ,\use:c{mtd@#4-west-portbox-height}) + \mtd@mco}
  % Place the center
  \node[
    ,mtd-fit-module-center
    ,fit=(#4-innerfit)(#4-label)
    ,minimum~width=\mtd@centralwidth
    ,minimum~height=\mtd@centralheight
    ,#1
  ](#4-center){};
  % Place port boxes relative to the central box
  \@placenodenow(#4-north-portbox){\pgfpointanchor{#4-center}{north}}
  \@placenodenow(#4-south-portbox){\pgfpointanchor{#4-center}{south}}
  \@placenodenow(#4-east-portbox){\pgfpointanchor{#4-center}{east}}
  \@placenodenow(#4-west-portbox){\pgfpointanchor{#4-center}{west}}
  % Active any cleanup code that's to be run after placement
  \seq_use:cn {#4-port-cleanup}{}
  % Place the module wrapper that we'll use for positioning mainly.
  \node[
    ,mtd-fit-module-wrap
    ,fit=(#4-center)(#4-portbox-north)(#4-portbox-south)
         (#4-portbox-east)(#4-portbox-west)
    ,#1
  ](#4){};
}

% The command to add a port to a module, should only work within
% a module's port specifier block. 
% #1 = port styles
% #2 = position specifier
% #3 = port name
% #4 = port content
\DeclareDocumentCommand \port {D[]{} r<> r() +m}{
  % Code that is run on the creation of a node
  \seq_put_right:cn {\currentmodulename-#2-ports} {
    % Add previous node info to current style data
    \ifthenelse{\isundefined\prevnode}
      {\tikzstyle{pp}=[]}
      {\tikzstyle{pp}=[previous-port=\prevnode]}
    % Generate Nod
    \node[
      ,port-type=normal
      ,port-dir=#2
      ,local-port-style
      ,pp
      ,#1
    ] (#3) {#4};
    % Bootstrap for next section, 
    \def\prevnode{#3}
    % Generate Forward and Reverse "Pseudo-Anchors" 
    \ifthenelse{\equal{#2}{north}}{
      \coordinate(#3-conn) at (#3.northconn);
      \coordinate(#3-rear) at (#3.south);
    }{}
    \ifthenelse{\equal{#2}{south}}{
      \coordinate(#3-conn) at (#3.southconn);
      \coordinate(#3-rear) at (#3.north);
    }{}
    \ifthenelse{\equal{#2}{east}}{
      \coordinate(#3-conn) at (#3.eastconn);
      \coordinate(#3-rear) at (#3.west);
    }{}
    \ifthenelse{\equal{#2}{west}}{
      \coordinate(#3-conn) at (#3.westconn);
      \coordinate(#3-rear) at (#3.east);
    }{}
  }
  % Code that is run after all the elements are placed.  
  \seq_put_left:co {\currentmodulename-port-cleanup}{
  }
}

\ExplSyntaxOff