Beamer + TikZ: Draw behind frame title

Question

For one beamer slide, I want to draw a with TikZ on the full beamer canvas. However, the logo and frame title of the heading should stay in the foreground.

Here is a minimal example:

\documentclass{beamer}
\usepackage{tikz}

\pgfdeclarelayer{background}
\pgfsetlayers{background,main}

\begin{document}

\begin{frame}{Frame Title}
    \begin{tikzpicture}[overlay, remember picture]
        \begin{pgfonlayer}{background}
            \path[fill=red] (current page.north west) rectangle (current page.south);
        \end{pgfonlayer}
    \end{tikzpicture}
\end{frame}

\end{document}

Currently, the red rectangle covers the frame title. I want it to be behind it (so the frame title is visible again). Do you know if this is possible (putting it in the "background" pgf layer obviously does not work)?

Answer 1

A beamer frame consists of several layers, see Figure 1 from the beamer user guide for an overview:

You can move your tikz picture to one of the beamer layers which are further down, e.g. the background canvas. If you do this within a group {...}, it won't affect other frames.

\documentclass{beamer}
\usepackage{tikz}


\begin{document}

{
\setbeamertemplate{background canvas}{%
    \begin{tikzpicture}[overlay, remember picture]
        \path[fill=red] (current page.north west) rectangle (current page.south);
    \end{tikzpicture}%
}
\begin{frame}{Frame Title}

\end{frame}
}
\end{document}