Is there a TikZ equivalent to the PSTricks \ncbar command?

Question

Although I now use TikZ, every so often I find myself looking for very useful PSTricks commands which don't seem to exist in TikZ. The pst-node package has an \ncbar command which allows one to connect two nodes with arms dropping down, typically at a 90 degree angle. Here's an example:

\documentclass{article}
\usepackage{pst-node}
\begin{document}
\rput(0,0){\rnode{A}{\psframebox{A}}}
\rput(2,0){\rnode{B}{\psframebox{B}}}
\ncbar[angle=90]{A}{B}
\end{document}

Is there a TikZ equivalent to this useful command? If not, how easy would it be to create one?

Answer 1

There's no direct equivalent, but you can use the to path mechanism together with the calc library to do something similar. If you set:

\tikzset{
    ncbar angle/.initial=90,
    ncbar/.style={
        to path=(\tikztostart)
        -- ($(\tikztostart)!#1!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztotarget)$)
        -- ($(\tikztotarget)!($(\tikztostart)!#1!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztotarget)$)!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztostart)$)
        -- (\tikztotarget)
    },
    ncbar/.default=0.5cm,
}

you can draw a rectangular connection between two coordinates using \draw (a) to [ncbar] (b);. The offset of the line can be controlled using the optional parameter: \draw (a) to [ncbar=1cm] (b);. To change the angle of the connecting line, you can use the key ncbar angle: \draw [blue] (a) to [ncbar=1.5cm, ncbar angle=70] (b);

\documentclass[landscape]{article}
\usepackage{tikz}
\usetikzlibrary{calc}

\tikzset{
    ncbar angle/.initial=90,
    ncbar/.style={
        to path=(\tikztostart)
        -- ($(\tikztostart)!#1!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztotarget)$)
        -- ($(\tikztotarget)!($(\tikztostart)!#1!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztotarget)$)!\pgfkeysvalueof{/tikz/ncbar angle}:(\tikztostart)$)
        -- (\tikztotarget)
    },
    ncbar/.default=0.5cm,
}

\begin{document}
\begin{tikzpicture}
\node [draw] (a) {A};
\node at (2,-1) [draw] (b) {B};

\draw  (a) to [ncbar] (b);
\draw [red] (a) to [ncbar=-1cm] (b);
\draw [blue] (a) to [ncbar=1.5cm, ncbar angle=70] (b);
\end{tikzpicture}
\end{document}