162. LaTeX技巧493：beamer做的callout效果

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选自：http://tex.stackexchange.com/questions/5423/how-to-open-a-temporary-comics-like-balloon-in-a-beamer-slide

代码如下：

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{shapes.callouts}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\begin{document}
\begin{frame}
\frametitle{An Unexpected Website}

We learnt of this trick from tex.SX\tikz[remember picture] \node (a) {\vphantom{X}};

\begin{tikzpicture}[remember picture,overlay]
\path<2> (a.east) ++(0,1) node[anchor=west,ellipse callout,fill=red!50,opacity=.5, callout absolute pointer={(a.mid)}] {tex.stackexchange.com};
\end{tikzpicture}

\pause
\pause

And now for something completely different.
\end{frame}
\end{document}

效果图：

运行中有两个问题：

1、MIKTeX，会提示：找来源码，编译一下，出现错误如Undefined control sequence.\pgf@sh@bg@ellipse callout ...pgf@sh@np@\pgf@test\noexpand \endcsname }\ede.。

解决方案参看：http://bbs.chinatex.org/forum.php?mod=viewthread&tid=6274&page=1&extra=#pid14061

2、TeXLive 新系统会有错误提示：

! Undefined control sequence.
\Gm@lmargin ->\Geom@lmargin

解决方案参看：http://bbs.chinatex.org/forum.php?mod=viewthread&tid=6273&extra=page=1