[Tex/LaTex] Remove indentation by fbox

Question

Here is an update of my question, showing what I really mean:

I want to add a frame to my inner minipage.

But \fbox indents the minipage so that it causes an overfull hbox error

\documentclass{beamer}
\usepackage{showframe}

\begin{document}

\begin{frame} %works fine
\begin{center}
a

\begin{minipage}{0.4\textwidth}
\hfill
b

\begin{minipage}{\textwidth}

\begin{itemize}
\item one
\end{itemize}
\end{minipage}
\end{minipage}
\hfill
\begin{minipage}{0.4\textwidth}
c

\begin{minipage}{\textwidth}

\begin{itemize}
\item two
\end{itemize}
\end{minipage}
\end{minipage}

d
\end{center}
\end{frame}

\begin{frame} %overfull hbox
\begin{center}
a

\begin{minipage}{0.4\textwidth}
\hfill
b

\fbox{\begin{minipage}{\textwidth}

\begin{itemize}
\item one
\end{itemize}
\end{minipage}}
\end{minipage}
\hfill
\begin{minipage}{0.4\textwidth}
c

\fbox{\begin{minipage}{\textwidth}

\begin{itemize}
\item two
\end{itemize}
\end{minipage}}
\end{minipage}

d
\end{center}
\end{frame}

\end{document}

Answer 1

Here are several solutions, with and without the framed environment:

\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{framed}

\begin{document}

\fbox{\begin{minipage}{0.4\textwidth} % fbox only for showing problem
% insert some tikz picture
\noindent
\fbox{\begin{minipage}{\dimexpr\linewidth-2\fboxsep-2\fboxrule}
some text
\end{minipage}}
\end{minipage}}
\hfill
\fbox{\begin{minipage}{0.4\textwidth} % fbox only for showing problem
% insert some tikz picture
\begin{framed}\begin{minipage}{\linewidth}
some other text
\end{minipage}\end{framed}
\end{minipage}}

\fbox{\begin{minipage}{0.4\textwidth} % fbox only for showing problem
% insert some tikz picture
\begin{minipage}{\linewidth}\begin{framed}
some other text
\end{framed}\end{minipage}
\end{minipage}}

\end{document}