Page Layout ⇒ Tikz graybox \textwidth problem?

[csmgroup]

I need to draw round grayed box using tikz. The problem is that I need to reduce -5ex to fit into the box in a graybox. Why is this? Why \textwidth is not the width of the gray box?

Code: Select all

\documentclass{article}
\usepackage{layouts}

\usepackage{tikz}

\newlength{\mytikzwidth}
\setlength{\mytikzwidth}{\textwidth}
\addtolength{\mytikzwidth}{-5ex} % this 5ex is just rule of thumb.
\verb|capital| is a Map\footnote{The example uses country and capital,
  and it can be described as a map. Isn't it intentioanl?}, so it
understands the meaning of `+=' if the input is \verb|( -> )|.

\begin{document}

\noindent\begin{tikzpicture}
  \draw node[draw=black,fill=black!20,rounded corners,inner sep=2ex,text width=\mytikzwidth] {
    Lorem ipsum dolor sit amet \dots
    };
\end{tikzpicture}

\end{document}

[torbjorn t.]

The option text width given to the node makes the text in the node that width. However, the node is wider than the text, as the inner separation (the distance from the text to the edge of the node) of the node is set to 2ex. As you have 2ex of space on both sides of the text, the width of the box will be 4ex wider than \mytikzwidth.

I don't know if there are any better solutions to the problem, than the one you have already found.

[csmgroup]

That makes sense, and I experimented to check subtracting 2*sep from the textwidth gives me well aligned gray box.

Thanks a lot for the help.