Beamer and TikZ: uncovering a tree level by level

[Rob]

Hi,

I have been managed to define an environment in which I can draw a
tree with TikZ, which Beamer will uncover, one level at a time. Not
only the text in the nodes will uncover, but also the edges. Here is a
MWE:

\documentclass{beamer}
\mode<presentation>{\setbeamercovered{transparent}}
\usepackage{tikz}
\usetikzlibrary{trees}

\newenvironment{appearingtree}{
\alt<-1>{\tikzstyle overlayed1=[draw=black!30]}{\tikzstyle
overlayed1=[draw=black]}
\alt<-2>{\tikzstyle overlayed2=[draw=black!30]}{\tikzstyle
overlayed2=[draw=black]}
\alt<-3>{\tikzstyle overlayed3=[draw=black!30]}{\tikzstyle
overlayed3=[draw=black]}
\begin{tikzpicture}
[level 1/.style={overlayed1},level 2/.style={overlayed2},level
3/.style={overlayed3}]
}{
\end{tikzpicture}
}

\begin{document}
\frame{
\begin{appearingtree}
\node{root}
child{node{{\onslide<2->{child at level 1}}}
child{node{{\onslide<3->{child at level 2}}}
child{node{{\onslide<4->{child at level 3}}}}
}
}
;
\end{appearingtree}
}
\end{document}

I would like to parametrize the environment on the number of layers
the tree will have, because Beamer will generate slides up to the
highest pausenumber it encounters. So, for example, a tree with 2
levels will have an 'extra' slide (which uncovers nothing), with the
current definition.

I have tried to rewrite the definition, but I don't understand LaTeX's
loops, expansion and things like csname enough to make it work. This
is how far I got (omitting all my fruitless experimenting with
combinations of the aforementioned commands):

\documentclass{beamer}
\mode<presentation>{\setbeamercovered{transparent}}
\usepackage{tikz}
\usetikzlibrary{trees}

\newcount\n
\newcount\z
\newenvironment{appearingtree}[1]{
\n=1%
\z=#1\advance\z by 1%
\loop\ifnum\n<\z%
\alt<-\n>{\tikzstyle overlayed\n=[draw=black!30]}{\tikzstyle
overlayed\n=[draw=black]}%
\advance\n by 1%
\repeat%
\begin{tikzpicture}
[level 1/.style={overlayed1},level 2/.style={overlayed2},level
3/.style={overlayed3}]
}{
\end{tikzpicture}
}

\begin{document}
\frame{
\begin{appearingtree}{3}
\node{root}
child{node{{\onslide<2->{child at level 1}}}
child{node{{\onslide<3->{child at level 2}}}
child{node{{\onslide<4->{child at level 3}}}}
}
}
;
\end{appearingtree}
}
\end{document}

This should make my basic problem clear. Can anyone help me make this
loop work the way I intend?

[Rob]

Well, I'm halfway there. Replacing the definition by the following
seems to work:

\newenvironment{appearingtree}[1]{
\n=1%
\z=#1\advance\z by 1%
\loop\ifnum\n<\z%

\edef\tmp{overlayed\the\n}
\alt<-\n>{\tikzstyle \tmp=[draw=black!30]}{\tikzstyle
\tmp=[draw=black]}%

\advance\n by 1%
\repeat%
\begin{tikzpicture}
[level 1/.style={overlayed1},level 2/.style={overlayed2},level
3/.style={overlayed3}]
}{
\end{tikzpicture}
}

Now I just need to the parameters for the tikzpicture environment in a
similar way. Unfortunately, I can't seem to get it to work.

[Rob]

I am able to formulate the parameters I need to pass in a savebox. Is
there any way I can pass the contents of this savebox as the
(optional) argument to the tikzpicture environment? Just using \unhbox
\mybox or pulling the same \edef trick doesn't work (btw, the trailing
comma doesn't matter):

\documentclass{beamer}
\mode<presentation>{\setbeamercovered{transparent}}
\usepackage{tikz}
\usetikzlibrary{trees}

\newcount\n
\newcount\z
\newsavebox{\mybox}

\newenvironment{appearingtree}[1]{
\n=1%
\z=#1\advance\z by 1%
\loop\ifnum\n<\z%
\edef\tmp{overlayed\the\n}
\alt<-\n>{\tikzstyle \tmp=[draw=black!30]}{\tikzstyle
\tmp=[draw=black]}%

\savebox{\mybox}{\unhbox\mybox level \the\n/.style=\{overlayed\the\n
\},}% i.e. append 'level #/.style={overlayed#},' (where # = \n) to the
savebox

\advance\n by 1%
\repeat%

\edef\tmp{\unhbox\mybox}
\begin{tikzpicture}[\tmp] % this does not work

[Mike Kaufmann]

Hello Rob,

the following may work, but no guarantee (my tikz always complains,
may be too old or somehow broken).

\documentclass{beamer}
\mode<presentation>{\setbeamercovered{transparent}}
\usepackage{tikz}
\usetikzlibrary{trees}

\newcount\n
\newcount\z
\newtoks\mytoken

\newenvironment{appearingtree}[1]{
\n=1%
\z=#1\advance\z by 1%

\mytoken{[}% initialize
%\typeout{Test 0: \the\mytoken}% just for testing

\loop\ifnum\n<\z%
\edef\tmp{overlayed\the\n}
\alt<-\n>{\tikzstyle \tmp=[draw=black!30]}{\tikzstyle \tmp=[draw=black]}%

\ifnum\n>1\mytoken\expandafter{\the\mytoken,}\fi% add ',' after first
option
\edef\tmp{\the\mytoken level \the\n/.style={\tmp}}
\mytoken\expandafter{\tmp}
%\typeout{Test \the\n: \the\mytoken}% just for testing

\advance\n by 1%
\repeat%

\mytoken\expandafter{\the\mytoken]}
%\typeout{Test \the\n: \the\mytoken}% just for testing
\expandafter\calltikzpicture\the\mytoken\nil
}{
\end{tikzpicture}
}
\def\calltikzpicture#1\nil{\begin{tikzpicture}#1}

[Rob]

On 13 aug, 01:08, Mike Kaufmann <m...@gmx.de> wrote:
> Hello Rob,
>
> the following may work, but no guarantee (my tikz always complains,
> may be too old or somehow broken).

It works perfectly fine over here. Thank you very much!

For completeness' sake, this is my own final version:

% environment for drawing a tikz tree which uncovers level by level
% #1 = additional options to pass to tikz
% #2 = number of tree levels
\newenvironment{overlaytree}[2][]{%
% declaring variables

\newcount\n
\newcount\z
\newtoks\mytoken

% initializing variables
\n=1%
\z=#2\advance\z by 1%
\mytoken{[text depth=0pt,}%

%\typeout{Test 0: \the\mytoken}

% looping, building up declarations and parameters
\loop\ifnum\n<\z%
\edef\tmp{overlayed\the\n}%

\alt<-\n>{\tikzstyle \tmp=[draw=black!30]}{\tikzstyle
\tmp=[draw=black]}%
\ifnum\n>1\mytoken\expandafter{\the\mytoken,}\fi% add ',' after
first option

\edef\tmp{\the\mytoken level \the\n/.style={\tmp}}%
\mytoken\expandafter{\tmp}%

%\typeout{Test \the\n: \the\mytoken}

\advance\n by 1%
\repeat%

% add additional (optional) parameters
\mytoken\expandafter{\the\mytoken,#1]}%

%\typeout{Test \the\n: \the\mytoken}

% call tikz
\expandafter\tikz\the\mytoken
}{}