Axis background has missing draw/stroke

Question

I want to draw a rectangle around an axis created using pgfplots. This is a minimal example:

\documentclass{minimal}

\usepackage{tikz}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
\begin{axis}[axis background/.style={fill=blue!10, draw=black, line width=1pt},
    axis x line=center, axis y line=center, 
    xmin=-1, xmax=1, ymin=-1, ymax=1]
\addplot {x};
\end{axis}
\end{tikzpicture}
\end{document}

Here is what it creates:

As you can see, the left draw/stroke on the axis background is missing. Anybody know what the problem is?

Answer 1

The command that draws the two-dimensional axis appears to be lacking a \pgfpathclose command (I'll file a bug report for this). In the meantime, you can work around the problem by using insert path={ \pgfextra{\pgfplots@clippath@install{} \pgfpathclose} } in your axis background style.

In the example below, I've wrapped the insert path in a new style called closed background.

\documentclass{minimal}

\usepackage{tikz}
\usepackage{pgfplots}

\makeatletter
\tikzset{
    closed background/.style={
        insert path={
            \pgfextra{\pgfplots@clippath@install{} \pgfpathclose}
        }
    }
}
\makeatother

\begin{document}
\begin{tikzpicture}
\begin{axis}[
    axis background/.style={
        fill=blue!10,
        draw=black,
        line width=1pt,
        line cap=round,
        closed background
    },
    axis lines*=center, 
    xmin=-1, xmax=1, ymin=-1, ymax=1]
\addplot {x};
\end{axis}
\end{tikzpicture}
\end{document}

Answer 2

I am not sure why axis background does not draw the left line. However, you can use the backgrounds library to add a background rectangle which by default appears to produce better results by adding a separation between the axis and the box. Note that the grey box is the result of cropping, and not part of the graph:

\documentclass[border=5pt]{standalone}

\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{backgrounds}

\begin{document}
\begin{tikzpicture}
\begin{axis}[
    axis x line=center, axis y line=center,
    xmin=-1, xmax=1, ymin=-1, ymax=1,
    /tikz/background rectangle/.style={
        fill=blue!10,
        draw=black,
        line width=1pt
    },
    show background rectangle
    ]
\addplot {x};
\end{axis}
\end{tikzpicture}
\end{document}