Without a MWE it's hard to know exactly what sort of thing you're after but I think that the listings extension to tikzmark can handle this sort of thing. You need tikzmark.dtx from TeX-SX Launchpad, run tex tikzmark.dtx and put the generated files somewhere that tex can find them (if you run latex tikzmark.dtx or pdflatex tikzmark.dtx it will complain about a missing file - ignore that).
Then the following code:
\documentclass{article}
%\url{http://tex.stackexchange.com/q/86309/86}
\usepackage{listings}
\usepackage{tikz}
\usetikzlibrary{arrows,tikzmark,shadows}
\usetikzmarkextra{listings}
\tikzset{
comment/.style={
draw,
fill=blue!70,
text=white,
rounded corners,
drop shadow,
align=left,
},
}
\begin{document}
\begin{lstlisting}[language=TeX,name=texcode,numbers=left,breakatwhitespace=true,breaklines=true]
\newcommand\balloon[4]{%
\pgfmathtruncatemacro\firstline{%
#3-1
}%
\iftikzmark{line-#2-\firstline-start}{%
\iftikzmark{line-#2-#3-first}{%
\xdef\blines{({pic cs:line-#2-\firstline-start} -| {pic cs:line-#2-#3-first})}%
}{%
\iftikzmark{line-#2-#3-start}{%
\xdef\blines{({pic cs:line-#2-\firstline-start} -| {pic cs:line-#2-#3-start})}%
}{%
\xdef\blines{(pic cs:line-#2-\firstline-start)}%
}%
}%
}{%
\xdef\blines{}%
}%
\foreach \k in {#3,...,#4} {%
\iftikzmark{line-#2-\k-first}{%
\xdef\blines{\blines (pic cs:line-#2-\k-first) }
}{}
\iftikzmark{line-#2-\k-end}{%
\xdef\blines{\blines (pic cs:line-#2-\k-end) }
}{}
}%
\ifx\blines\empty
\else
\edef\temp{\noexpand\tikz[remember picture,overlay] \noexpand\node[fit={\blines},balloon] (#1) {};}%
\temp
\fi
}
\end{lstlisting}
\begin{tikzpicture}[remember picture,overlay,>=stealth']
\draw[<-,ultra thick] (pic cs:line-texcode-1-end) +(1em,.7ex) -| +(2.5,1) node[above,comment,thin] {Command name};
\draw[<-,ultra thick] (pic cs:line-texcode-3-end) ++(1em,.7ex) -| +(5.8,1) node[above right,comment,thin] {Find previous line};
\draw[<-,ultra thick] (pic cs:line-texcode-5-end) ++(1em,.7ex) -| +(2.2,.5) node[above,comment,thin] {If previous line exists, add to the list};
\draw[<-,ultra thick] (pic cs:line-texcode-18-end) ++(1em,.7ex) -| +(2.2,.5) node[above,comment,thin] {Loop through rest of lines};
\draw[<-,ultra thick] (pic cs:line-texcode-28-end) ++(1em,.7ex) -| +(1,1.5) node[above,comment,thin] {Add a node covering all the lines};
\end{tikzpicture}
\end{document}
produces:
(Only it looks much nicer in the PDF. And note that there's been an eminent suggestion to replace \usetikzmarkextra with \usetikzmarklibrary which will happen sometime soon so if the above complains about \usetikzmarkextra try switching it.)
\documentclassand the appropriate packages that sets up the problem. While solving problems is fun, setting them up is not. Then those trying to help can simply cut and paste your MWE and get started on solving problem. – Peter Grill Dec 10 '12 at 4:37\begin{tikzpicture}and one after\end{tikzpicture}. Put percent signs after the opening brace of the\newcommandand after\end{tikzpicture}and that should stop things shifting. – Andrew Stacey Dec 10 '12 at 22:16