Self call from a call from a self call lead to strange placement of arrows

[ebousse]

When a self-call is made while we are still already inside a self-call of another object, it seems to shift the arrows to the right, like this:

To reproduce:

\documentclass[]{article}

\usepackage{tikz}
\usepackage{pgf-umlsd}
\usepgflibrary{arrows} % for pgf-umlsd

\begin{document}

	\begin{sequencediagram}
	\newthread{t}{:Thread}
	\newinst{i}{:Inst}
	
	\begin{call}{t}{}{t}{}
		
		\begin{call}{t}{}{i}{}
			\begin{call}{i}{}{i}{}
			\end{call}
		\end{call}
	\end{call}
	
\end{sequencediagram}

\end{document}

[ebousse]

I've opened a pull request for fixing the issue #30

[IceflowRE]

The return arrow from :Inst is wrong placed too.