# tikz tree node on edge always above the line, not just on it

I am building attack trees for my bachelor thisis. And i need to connect some children nodes by a logical and operator. So i just drew a line between thoses nodes, and put a node on it.

Sadly I am not able to make the label of the edge to be put directly on the (hidden) line, its always midway above it. And i have no idea why... Hope you can help me.

Heres a minimal example:

\documentclass[a4paper,12pt,headsepline,dvipsnames,bibliography=totocnumbered]{scrartcl}

\usepackage{tikz}
\usepackage{tikz-qtree}

\usetikzlibrary{trees}

\begin{document}

\tikzset{
attackTree/.style={
auto,
font=\small,
edge from parent fork down,
level distance=2.5cm,
every node/.style=
{   rectangle,
minimum height=15mm,
minimum width=30mm,
draw=black,
align=center,
text depth = 0pt
},
edge from parent/.style=
{   draw=black}
},
treeOperator/.style={
minimum width=0,
minimum height=0,
draw=none
}
}

\begin{tikzpicture}[
attackTree,
sibling distance=35mm
]
\node {Open safe}
child{
node {Pick lock}
}
child{node {Learn combo}
child{node {Find written\\combo}}
child{node {Get combo\\from target}
child{node{Threaten}}
child{node{Blackmail}}
child{node{Eavesdrop}
child{node(listen){Listen to\\conversation}}
child{node(state){Get target to\\state combo}}
}
child{node{Bribe}}
}
}
child{node {Cut open safe}}
child{node {Install\\improperly}};

\draw[draw=none] (listen) -- (state) node[treeOperator,midway] {$\wedge$};
\end{tikzpicture}
\end{document}


And this is what it looks like:

I Just want the logical and operator centered right on the hidden line. There must be an option in my settings, which prevents it from beeing where it should be, but I am not able to figure out, which one it is.

• Add auto=false to the TreeOperator settings: treeOperator/.style={...,auto=false}.
add auto=false to the TreeOperator settings: TreeOperator/.style={...,auto=false}. –