How to avoid covering nodes with connection lines

Question

When drawing connection lines (edge) between nodes, the lines will be drawn over the nodes (due to the drawing sequence). If having many connections, it may problematically cover the nodes, and particularly the text therein. A very basic example is

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
   \node[fill=blue,circle,text width=3cm] (first) at (1,1) {First};
   \node[fill=green,circle,text width=3cm] (second) at (5,5) {This is the text that will be cover with the connection lines};
   \node[fill=purple,circle,text width=3cm] (third) at (1,9) {This text will be covered too};

\draw[->,thick,draw=red!50] (first.east) to [out=0,in=0] (third.east);
\draw[->,thick,draw=red!50] (first.west) to [out=180,in=75] (third.north east);
\end{tikzpicture}

\end{document}

Ideal Solution: Turning the connection lines around the node. In fact, the node area should be a forbidden zone for lines.

Practical Solution: Passing the lines under the nodes. At least lines will not affect readability of the text.

How to implement one of these solutions to avoid lines over nodes?

Answer 1

One solution (that could be put in the practical branch) is to use the backgrounds library.

The code is:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{backgrounds}
\begin{document}

\begin{tikzpicture}
\node[fill=blue,circle,text width=3cm] (first) at (1,1) {First};
\node[fill=green,circle,text width=3cm] (second) at (5,5) {This is the text that will be cover with the connection lines};
\node[fill=purple,circle,text width=3cm] (third) at (1,9) {This text will be covered too};
% insert connection lines in background 
\begin{pgfonlayer}{background}
\draw[->,thick,draw=red!50] (first.east) to [out=0,in=0] (third.east);
\draw[->,thick,draw=red!50] (first.west) to [out=180,in=75] (third.north east);
\end{pgfonlayer}
\end{tikzpicture}

\end{document}

The graphical result:

For details, see section 25 Background Library and section 82 Layered Graphics on the pgfmanual (version October 25, 2010).

EDIT

Following Andrew Stacey's suggestion, in the code there will be defined a new layer set before the main layer (to see it in background with respect to the main layer).

The modified code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{backgrounds}
\pgfdeclarelayer{myback}
\pgfsetlayers{background,myback,main} 
% to still have the possibility of exploiting the background layer
\begin{document}

\begin{tikzpicture}
\node[fill=blue,circle,text width=3cm] (first) at (1,1) {First};
\node[fill=green,circle,text width=3cm] (second) at (5,5) {This is the text that will be cover with the connection lines};
\node[fill=purple,circle,text width=3cm] (third) at (1,9) {This text will be covered too};
% insert connection lines in background using myback layer
\begin{pgfonlayer}{myback}
\draw[->,thick,draw=red!50] (first.east) to [out=0,in=0] (third.east);
\draw[->,thick,draw=red!50] (first.west) to [out=180,in=75] (third.north east);
\end{pgfonlayer}
\end{tikzpicture}

\end{document}

will lead to the same graphical result shown above.

Answer 2

Disclaimer: This is an overkill for this case. Please read the comments.

Another option would be to use append after command key to use the node name and location before it's drawn in the picture. Since the (second) node is not related to the (first) and (third) interaction it can be placed later.

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}
\node[fill=blue,circle,text width=3cm] (first) at (1,1) {First};
\draw[->,thick,draw=red!50] node[
     fill=purple,
     circle,
     text width=3cm,
     append after command={
           (first.west) to [out=180,in=75] (third.north east)
     }]
     (third) at (1,9) {This text will be covered too};

\draw[->,thick,draw=red!50] (first.east) to [out=0,in=0] (third.east);

\node[fill=green,circle,text width=3cm] (second) at (5,5) {This is the text that will be cover with the connection lines};
\end{tikzpicture}
\end{document}