Get current indentation inside an escape within lstlisting

Question

I'm typesetting source code with the listings package's lstlisting environment. Since I have to draw custom stuff in some lines, I use escapeinside in these lines to insert a tikzpicture.

Since these lines may be indented, I need to know the length of the indentation, or the remaining width of the line. Is there any way to access that? \linewidth still contains the full line length, so a box of width \linewidth sticks out on the right as much as the line was indented.

---

For example, consider this document:

\documentclass{article}

\usepackage{tikz}
\usepackage{listings}

\begin{document}

\newcommand{\mwebox}{\begin{tikzpicture}[baseline]\path[fill=black!10, draw=black!0, thick] (0,-0.20) rectangle (5, 0.30);\end{tikzpicture}}

\begin{lstlisting}[escapeinside=~~]
Test
~\mwebox~
Test

    Test
    ~\mwebox~
    Test
\end{lstlisting}

\end{document}

I want to extend the gray boxes to the end of the lines.

Answer 1

This isn't really answering your question as I am not doing this automatically, but I think that you probably need to manually tweak your tikzpicture environment because the listings manual says "indention must be done by hand".

For example, using

\documentclass{article}

\usepackage{tikz}
\usepackage{listings}

\begin{document}

\newcommand{\mwebox}[1][12]{\begin{tikzpicture}[baseline]\path[fill=black!10, draw=black!0, thick] (0,-0.20) rectangle (#1, 0.30);\end{tikzpicture}}

\begin{lstlisting}[escapeinside=~~]
Test
~\mwebox~
Test

    Test
    ~\mwebox[11.2]~
    Test
\end{lstlisting}

\end{document}

gives the output that I think you want:

So, I have defined \mwebox to have an optional argument that defaults to 12, which is close to the margin. I then found 11.2 by trial and error for the second box.