# How can I tikz the equivalence (i.e. $\Leftrightarrow$) as arrow over a background color?

Follow-up question to How can I tikz the equivalence (i.e. $\Leftrightarrow$) as arrow?

What if I want to draw the equivalence arrow over a (non-white) background color? The fill option seems to have no effect.

\documentclass{beamer}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{arrows}
\begin{document}

\begin{frame}
\begin{definition}[How to fill the following arrow with background color?]
\begin{tikzpicture}
\draw[implies-implies,double equal sign distance,fill=bg] (2,1) -- (3,2);
\end{tikzpicture}
\end{definition}
\end{frame}

\end{document}


You want the double key, not fill. Also note that the arrows.meta library has superseded the arrows library.

\documentclass{beamer}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
\begin{document}

\begin{frame}
\begin{definition}[How to fill the following arrow with background color?]
\begin{tikzpicture}
\draw[Implies-Implies,double equal sign distance,double=bg] (2,1) -- (3,2);
\end{tikzpicture}
\end{definition}
\end{frame}

\end{document}


You have to specify the double styling :

\draw[implies-implies,double equal sign distance,double=bg] (2,1) -- (3,2);