Self-loops in graphs change their shapes when the picture is rotated

Question

I am using tkz-graph for drawing graphs. Self-loops change their shapes when the picture is rotated. Is this normal? Since I could probably redesign the rotated graph from the beginning, I am more interested in knowing why the behaviour occurs, or whether I am doing something wrong than in solving the problem. An example follows.

\documentclass{article}
\usepackage{tkz-graph}
\newcommand{\tp}[1]{\begin{tikzpicture}[rotate=#1]
                         \Vertex{a}
                         \Loop(a)
                    \end{tikzpicture}}

\begin{document}     
     \tp{0}

     \tp{90}

     \tp{180}

     \tp{270}
\end{document}

Answer 1

Edit in it's source it has:

\let\loop\grLoop

And grLoop is defined as:

\newcommand*{\grLoop}[1][]{\tkzGR@loop[#1]}%
\def\tkzGR@loop[#1](#2){%
\setkeys[GR]{loop}{#1}%
\protected@edef\@tempa{%
\noexpand \draw[\cmdGR@loop@color] (#2)%
  edge [EdgeStyle,LoopStyle,\cmdGR@loop@style]%
  node [LabelStyle,\cmdGR@loop@labelstyle]%
  {\cmdGR@loop@label} (#2)}\@tempa;%
}%

So we have to check EdgeStyle,LoopStyle,\cmdGR@loop@style

But in initializing Loopstyle contains:

\define@choicekey*[GR]{loop}{dir}[\val\nr]{WE,EA,NO,SO,NOWE,NOEA,SOWE,SOEA}{%
\ifcase\nr\relax
\tikzset{LoopStyle/.style = {in=225, out=135, distance=\cmdGR@loop@dist}}%
\or
\tikzset{LoopStyle/.style = {in= 45, out=-45, distance=\cmdGR@loop@dist}}%
\or
\tikzset{LoopStyle/.style = {in=135, out= 45, distance=\cmdGR@loop@dist}}%
\or
\tikzset{LoopStyle/.style = {in=-45, out=-135, distance=\cmdGR@loop@dist}}%
\or
\tikzset{LoopStyle/.style = {in=180, out=90, distance=\cmdGR@loop@dist}}%
\or
\tikzset{LoopStyle/.style = {in=90, out=0, distance=\cmdGR@loop@dist}}%
\or
\tikzset{LoopStyle/.style = {in=-90, out=-180, distance=\cmdGR@loop@dist}}%
\or
\tikzset{LoopStyle/.style = {in=0, out=-90, distance=\cmdGR@loop@dist}}%
\fi%
}

And that means that the starting point does not initializing there (just angles and distance)

So looking for the other option I find that \cmdGR@loop@style is no refered anywhere else and that probably is empty.

So the package doesn't provides any option for real rotation.

And if I try a loop with the code:

\newcommand{\tp}[1]{\xdef\ea{#1+90}\begin{tikzpicture}[rotate=#1]
                         \Vertex{a}
                         \draw (a) edge [in=0, out=90,distance=40] (a);
                    \end{tikzpicture}}

I get the same problem. This problem is reproduced by \Loop command

If I could add to in or if latex was adding to it by the rotation it would by better. May be we have to fill a bug for no valid rotation of edge options.

Old Answer:

What about something like this:

\documentclass{article}
\usepackage{xcolor}
\usepackage{tkz-graph}
\newcommand{\tp}[1]{\xdef\val{#1}\pgfmathsetmacro\vval{#1+60}\begin{tikzpicture}
                         \Vertex{a}
                         \path[->] (a) edge [out=\val,in=\vval,looseness=9] (a);
                    \end{tikzpicture}}

\begin{document}     
     \tp{0}

     \tp{90}

     \tp{180}

     \tp{270}
\end{document}

I just found here: How do you make a tkz graph with edges starting and ending at the same vertex? that \Loop command takes strange arguments for direction (see dir option) and may be this breaks the behavior. We can also do other thinks using calculations if this is not problem for you. But I think you can see now what is the problem.