TikZ node positioning and keyvals

Question

What's the best way to specify a node position on a path? The ways I found are not equivalent, which bothers me.

Why is below right different to below, right and right, below? Why is below right different to below=1pt, right=1pt and right=1pt, below=1pt?

\documentclass[tikz]{standalone}

\begin{document}

\begin{tikzpicture}
\draw (0,0) [out=40, in=150] to node [very near end, sloped, below right] {curve1} (20:6);
\draw (0,0) [out=40, in=150] to node [very near end, sloped, right, below] {curve2} (20:6);
\draw (0,0) [out=40, in=150] to node [very near end, sloped, below, right] {curve3} (20:6);
\end{tikzpicture}

\begin{tikzpicture}
\draw (0,0) [out=40, in=150] to node [very near end, sloped, right=1pt, below=1pt] {curve1} (20:6);
\draw (0,0) [out=40, in=150] to node [very near end, sloped, below=1pt, right=1pt] {curve2} (20:6);
\end{tikzpicture}

\end{document}

Answer 1

Everything about positioning and anchors is explained in section 17.5 Positioning nodes and it's worth to read it.

In any case I'll try to gave you some basic ideas about it.

The first and most important lesson is that any positioning command determines the node's anchor to be used. If you write below, what will be placed below this position will be the north anchor, and if you write above right, the anchor selected will be south east. (You can change this behaviour selecting a different anchor after the positioning option)

Second lesson, only the last positioning option survives. If you write below, right (with , between them) only right will be applied.

As an example:

\draw (0,0) [out=40, in=150] to 
node [pos=0, draw, sloped, above left] (al) {above left}
node [pos=0, draw, sloped, below right] {below right} 
node [pos=.5, draw, sloped, right, below] (rb) {right, below}
node [pos=1, draw, sloped, below, right] (br) {below, right}
(20:6);

will produce

Third lesson: when using new positioning library with explicit distance values like above=2mm, expressions like above right=2mm and above right=2mm and 2mm produce different results.

As an example, following code:

\draw (0,0) [out=40, in=150] to coordinate[pos=.5] (aux)
    node [pos=.5, draw, sloped, below right=3pt] {below right} 
    node [pos=.5, draw, sloped, above left=3pt] {above left} 
    node [pos=.5, draw, sloped, above right=3pt and 3pt] {above right} 
    node [pos=.5, draw, sloped, below left=3pt and 7pt] {below left} 
    (20:6);

generates

Of course, everything is much more better explained in previous link.

The complete code for previous examples is

\documentclass[tikz]{standalone}

\usetikzlibrary{positioning}

\begin{document}

\begin{tikzpicture}
\draw (0,0) [out=40, in=150] to 
node [pos=0, draw, sloped, above left] (al) {above left}
node [pos=0, draw, sloped, below right] {below right} 
node [pos=.5, draw, sloped, right, below] (rb) {right, below}
node [pos=1, draw, sloped, below, right] (br) {below, right}
(20:6);

\fill[red] (al.south east) circle(1pt);
\fill[red] (rb.north) circle(1pt);
\fill[red] (br.west) circle(1pt);

\end{tikzpicture}

\begin{tikzpicture}
\draw (0,0) [out=40, in=150] to coordinate[pos=.5] (aux)
    node [pos=.5, draw, sloped, below right=3pt] {below right} 
    node [pos=.5, draw, sloped, above left=3pt] {above left} 
    node [pos=.5, draw, sloped, above right=3pt and 3pt] {above right} 
    node [pos=.5, draw, sloped, below left=3pt and 7pt] {below left} 
    (20:6);
\fill[red] (aux) circle(1pt);
\end{tikzpicture}

\end{document}