TikZ-PGF – Changing Accepting States in Automata with Overlay-Beamer-Styles

automatabeameroverlaystikz-pgf

I am trying to draw an automaton using TikZ with the automata package that I am modifying from slide to slide with overlay-beamer-styles. One of the things I am changing is which nodes are marked as accepting states. However, changing this causes everything to shift around slightly, which looks bad when changing from slide to slide. How can I fix this? I would like all of the edges, node labels, etc to stay at the same places and only have the border of the nodes change, ideally by adding/removing the inner line.

Here is a minimum working example:

\documentclass{beamer}

\usepackage{tikz}
\usetikzlibrary{
    automata,
    overlay-beamer-styles}
    
\tikzset{
    accepting on/.style={alt=#1{accepting}{}}
}


\begin{document}

\begin{frame}{}
    \begin{tikzpicture}[initial text=,auto,state/.append style={minimum size=1.5cm}]
        \node[state,initial,accepting on=<2>] (z0) at (0,0) {$z_0$};
        \node[state,accepting on=<1>] (z1) at (2,0) {$z_1$};
        
        \path[->] (z0) edge [loop above] node {$a$} (z0)
                       edge node {$b$} (z1)
                  (z1) edge [loop above] node {$a,b$} (z1);
    \end{tikzpicture}
\end{frame}

\end{document}

and here is the output:

enter image description here

Best Answer

The automata style accepting by double is defined as

\tikzset{accepting by double/.style= {double,outer sep=.5\pgflinewidth+.3pt}} % .3pt is half double width distance

This means that not only a double line is added, but also that the size of the node changes due to the different outer sep.

You can avoid the node from jumping between overlays, if you increase the outer sep also on the non-accepted overlays:

\documentclass{beamer}

\usepackage{tikz}
\usetikzlibrary{
    automata,
    overlay-beamer-styles}
    
\tikzset{
    accepting on/.style={alt=#1{accepting}{accepting, double=none}}
}

\begin{document}

\begin{frame}
    \begin{tikzpicture}[initial text=,auto,state/.append style={minimum size=1.5cm}]
        \node[state,initial,accepting on=<2>] (z0) at (0,0) {$z_0$};
        \node[state,accepting on=<1>] (z1) at (2,0) {$z_1$};
        
        \path[->] (z0) edge [loop above] node {$a$} (z0)
                       edge node {$b$} (z1)
                  (z1) edge [loop above] node {$a,b$} (z1);
    \end{tikzpicture}
\end{frame}

\end{document}

enter image description here

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