How to set text margin without conflict with block environment? - latex

Question

I want to decrease the margin between the content text and the page edge. I follow the method from: https://tex.stackexchange.com/questions/354022/modifying-the-margins-of-all-slides-in-beamer by using \setbeamersize{text margin left=1.40mm, text margin left=1.40mm}.
However, it will make the block not centered in the slide. Thus, how do I set the text margin without influencing the setting of the block?
Is there another way to set the text margin?
The full scripts as follows:
\documentclass[t]{beamer}
\usetheme{Madrid}
\usecolortheme{beaver}
\usefonttheme{structurebold}
\usepackage{graphicx}
\usepackage{booktabs}
\usepackage{multicol}
\title[Short title]{Full Title of the Talk}
\author{JJ XX}
\institute[UCLA]
{
University of California \\
\medskip
\textit{jx#111.com}
}
\date{\today}
% set the text margin
\setbeamersize{text margin left=1.40mm, text margin left=1.40mm}
\settowidth{\leftmargini}{\usebeamertemplate{itemize item}}
\settowidth{\leftmargini}{\usebeamertemplate{enumerate item}}
\addtolength{\leftmargini}{-0.2\labelsep}
\begin{document}
\begin{frame}
\titlepage % Print the title page as the first slide
\end{frame}
\begin{frame}
\frametitle{Contents}
\begin{multicols}{2}
\tableofcontents
\end{multicols}
\end{frame}
\section{blocka}
\begin{frame}
\frametitle{blocka}
\begin{itemize}
\item First
\item Second
\end{itemize}
\begin{exampleblock}{Introduction to Beamer}
Beamer is a class of \LaTeX.
\end{exampleblock}
\end{frame}
\section{blockb}
\begin{frame}
The second example.
\frametitle{blockb}
\begin{block}{Beamer Intro}
New is New.
\end{block}
\end{frame}

Answer 1

The margins of beamer blocks are designed in such a way that the text within the block is still aligned with the surrounding text. If you set the margin independently, this will break this alignment:
\documentclass[t]{beamer}
\usetheme{Madrid}
\usecolortheme{beaver}
\setbeamersize{text margin left=1.40mm, text margin left=1.40mm}
\makeatletter
\setbeamertemplate{block begin}
{%
\par\vskip\medskipamount%
\hfill\begin{minipage}{.98\textwidth}%
\begin{beamerboxesrounded}[upper=block title,lower=block body,shadow=true]%
{\raggedright\usebeamerfont*{block title}\insertblocktitle}%
\raggedright%
\usebeamerfont{block body}%
}
\setbeamertemplate{block end}
{\end{beamerboxesrounded}\end{minipage}\vskip\smallskipamount}
\makeatother
\begin{document}
\begin{frame}
The second example.
\frametitle{blockb}
\begin{block}{Beamer Intro}
New is New.
\end{block}
\end{frame}
\end{document}
Alternatively, you could use the tcolorbox inner theme:
\documentclass[t]{beamer}
\usetheme{Madrid}
\usecolortheme{beaver}
\setbeamersize{text margin left=1.40mm, text margin left=1.40mm}
\useinnertheme{tcolorbox}
\tcbset{
center,
width=\linewidth
}
\begin{document}
\begin{frame}
The second example.
\frametitle{blockb}
\begin{block}{Beamer Intro}
New is New.
\end{block}
\end{frame}
\end{document}