Large braces over several items in an itemize with text by the brace

Question

This question is related to this question: Adding large brace next to body text, but is not a duplicate.

I have an itemize in a beamer presentation. I want to put a brace over some of these items. So here's what I have so far:

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,calc}
\newcommand{\tikzmark}[1]{\tikz[overlay,remember picture] \node (#1) {};}
\begin{document}
\begin{frame}
  \frametitle{Here is text}
  \begin{itemize}[<+->]
  \item A first item \tikzmark{topbrace}
  \item Another item, also inside the brace \tikzmark{bottombrace}\tikzmark{right}
  \item Outside the brace
  \end{itemize}
\onslide<+->{
\begin{tikzpicture}[overlay, remember picture]
\draw [decoration={brace,amplitude=0.5em},decorate,ultra thick,black]
 ($(right)!(topbrace.north)!($(right)-(0,1)$)$) --  ($(right)!(bottombrace.south)!($(right)-(0,1)$)$);
\end{tikzpicture}
}
\end{frame}
\end{document}

(needs compiling twice to get the right result). Incidentally, why is this? Is it something to do with the remember picture thing?

I have two issues with this excellent solution: the spacing doesn't look right (I'd like the top of the brace to be higher), and I'd like to add text to the right of the brace (see picture).

I can't quite fathom the complicated positioning commands used to add an extra node with text, or modify the spacing...

What I'd really like from an answer to this question is an explanation of what the ! and $ are doing...

Answer 1

These symbols are used for coordinate calculations. You need to load the library calc with \usetikzlibrary{calc} in order to use the coordinate calculation functions

\documentclass{scrartcl}
\usepackage{tikz} 
\usetikzlibrary{calc}
\begin{document}

\begin{tikzpicture} 
\draw [help lines] (0,0) grid (5,3);
\path coordinate (a) at (1,1) 
      coordinate (b) at (5,3) 
      coordinate (c) at (2,3); 
\fill [blue] (a) circle (2pt); 
\fill [green] (b) circle (2pt); 
\fill [red] ($(a) + 2*(1,1)$) circle (2pt); 
\fill [purple] ($(a)!-.5!(b)$) circle (2pt);
\coordinate (d) at ($(a)!(c)!(b)$);
\fill [black] (c) circle (2pt) (d) circle (2pt); 
\draw (c) -- (d); 
\end{tikzpicture}
\end{document}

1. How to use $: As you can see, the syntax uses the TEX math symbol $ to indicate that a “mathematical computation”. The red circle is placed from (a). I add 2*(1,1) at the coordinates of (a) so I get 1+2 and 1+2 (it's like addition of vectors)
2. How to use !: I want to get a coordinate of point between (a) and (b). If I want the middle I use ($(a)!.5!(b)$). I use (...) to search coordinates. Then I use $..$ to make a calculation. Finally, I use !number! to get a point on the line (a)--(b). It's like to use pos =.5.

Answer 2

\documentclass{beamer}
\usepackage{picture}
\begin{document}
\begin{frame}{Here is text}
  \begin{itemize}[<+->]
  \item A first item
  \item Another item, also inside the brace 
        \makebox(0,0){\put(0,2.2\normalbaselineskip){%
               $\left.\rule{0pt}{1.1\normalbaselineskip}\right\}$ foo}}
  \item Outside the brace
  \end{itemize}
\end{frame}
\end{document}

Answer 3

Another TikZ answer. I think using the let operation makes the code a bit easier to parse. It also saves you from having to use declare the right anchor.

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{decorations.pathreplacing,calc}
\newcommand{\tikzmark}[1]{\tikz[overlay,remember picture] \node (#1) {};}
\begin{document}
\begin{frame}
  \frametitle{Here is text}
  \begin{itemize}[<+->]
  \item A first item \tikzmark{topbrace}
  \item Another item, also inside the brace \tikzmark{bottombrace}
  \item Outside the brace
  \end{itemize}
\onslide<+->{
\begin{tikzpicture}[overlay, remember picture]
  \draw [decoration={brace,amplitude=0.5em},decorate,ultra thick,black]
    let \p1=(topbrace), \p2=(bottombrace) in
    ({max(\x1,\x2)}, {\y1+0.8em}) -- node[right=0.6em] {I'd like some text here} ({max(\x1,\x2)}, {\y2});
\end{tikzpicture}
}
\end{frame}
\end{document}

After let \p1=(topbrace), one can access its x and y coordinates with \x1 and \y1. So it is easier to find the right place for the brace (note that the anchors are placed on the baseline, hence the +0.8em in the top point). If you place a node immediately after -- it is place in the middle of the line. We want it to be a bit to the right of that.