forest-animate.sty

\ProvidesPackage{forest-animate}[2013/01/20]
\RequirePackage{forest}[2013/01/20]
\RequirePackage{animate}

%%% cumulative animation
%%% - must be done by producing all the frame-boxes in advance, since
%%%   animate's \newframe command introduces a TeX group
%%% - frames are controlled "node-wise"
%%% - after changing node's properties between frames, the node
%%%   usually needs to be re-typeset; this is done automatically, but
%%%   (i) doesn't cover all the cases (e.g. if a propagator is used to
%%%   modify some other node) and (ii) can be turned off using
%%%   "animate don't autotypeset".

\forestset{
  animate/.style 2 args={%
    declare keylist={frames}{},
    draw tree stage/.style={%
      TeX={\def\nframes{0}},
      for root'={if n children=0{frames=draw frame}{for last leaf={frames=draw frame}}},
      process keylist=frames,
      TeX={%
        \def\framen{0}%
        \def\animateminx{16000pt}%
        \def\animateminy{16000pt}%
        \def\animatemaxx{-16000pt}%
        \def\animatemaxy{-16000pt}%
        \loop
        \ifnum\framen<\nframes\relax
          \pgfmathsetlengthmacro{\animateminx}{min(\animateminx,\csname animateminx\framen\endcsname)}%
          \pgfmathsetlengthmacro{\animateminy}{min(\animateminy,\csname animateminy\framen\endcsname)}%
          \pgfmathsetlengthmacro{\animatemaxx}{max(\animatemaxx,\csname animatemaxx\framen\endcsname)}%
          \pgfmathsetlengthmacro{\animatemaxy}{max(\animatemaxy,\csname animatemaxy\framen\endcsname)}%
          \edef\framen{\number\numexpr\framen+1}%
        \repeat
        \begin{animateinline}[#1]{#2}
          \multiframe{\nframes}{iframen=0+1}{%
            \edef\animatemarshal{%
              \noexpand\begin{minipage}{\the\dimexpr\animatemaxx-\animateminx\relax}%
                \noexpand\vspace*{\the\dimexpr\animatemaxy-\csname animatemaxy\iframen\endcsname\relax}%
                \noexpand\hspace*{\the\dimexpr\csname animateminx\iframen\endcsname-\animateminx}%
                \noexpand\expandafter\box\noexpand\csname framebox\iframen\endcsname
                \noexpand\vspace*{\the\dimexpr\csname animateminy\iframen\endcsname-\animateminy}%
              \noexpand\end{minipage}%
            }\animatemarshal
          }%
        \end{animateinline}
      },
    },
  },
  animate typeset node/.style={typeset node},
  animate don't autotypeset/.style={animate typeset node/.style={}},
  frame/.style 2 args={
    frames={delay n={#1}{#2,animate typeset node}},    
  },
  draw frame/.style={
    TeX={\expandafter\locbox\csname framebox\nframes\endcsname},
    draw tree box/.expanded=\csname framebox\nframes\endcsname,
    tikz+={%
      \csxdef{animateminx\nframes}{\the\pgf@picminx}%
      \csxdef{animateminy\nframes}{\the\pgf@picminy}%
      \csxdef{animatemaxx\nframes}{\the\pgf@picmaxx}%
      \csxdef{animatemaxy\nframes}{\the\pgf@picmaxy}%
    },
    for root'=draw tree',
    TeX={\edef\nframes{\number\numexpr\nframes+1}},
    if have delayed={delay=draw frame}{}
  },
}

%%% non-cumulative animation
%%% - easier on memory (no boxes)
%%% - controlled centrally, not node-wise (but this could be reworked)
%%% - the real question is: should this mechanism be included in the
%%%   style as well? Will anybody ever need it?
\forestset{
  new frame/.style={draw tree',TeX={\newframe}},
  animate non-cumulative/.style n args=3{
    draw tree stage/.style={%
      TeX={\begin{animateinline}[#1]{#2}},%
      for root'=new frame,%
      #3,%
      for root'=draw tree,
      TeX={\end{animateinline}}%
    },
  },
}