Evitar saltar nodos en un árbol con bosque y proyector

Question

Hay algo en el manual sobre cómo evitar saltos y se explica aquí.Evitar saltos de fotogramas en el proyectortambién. Pero quizás tengo una situación diferente en los árboles. ¿Hay alguna forma de evitar los saltos entre las dos figuras en el siguiente código?

\documentclass{beamer}

\usepackage{forest}

% http://tex.stackexchange.com/questions/167690/presenting-a-forest-tree-from-bottom-to-top-in-beamer
% showing and hiding nodes and edges in forest
\tikzset{
    invisible/.style={opacity=0,text opacity=0},
    visible on/.style={alt=#1{}{invisible}},
    alt/.code args={<#1>#2#3}{%
      \alt<#1>{\pgfkeysalso{#2}}{\pgfkeysalso{#3}} % \pgfkeysalso doesn't change the path
    },
}
\forestset{
  visible on/.style={
    for tree={
      /tikz/visible on={#1},
      edge={/tikz/visible on={#1}}}}}

\newcommand{\sliste}[1]{%
\mbox{%
$\left\langle\mbox{\upshape\scshape #1}\right\rangle$}%
}

% specification for all trees, "default preamble" appends to existing specification.
% The version with apostrophe replaces it.
\forestset{default preamble'={
    for tree={align=center,parent anchor=south, child anchor=north,anchor=north,base=bottom},
    before drawing tree={
      sort by=y,
      for min={tree}{baseline}
    }
  }}


\forestset{
  declare dimen={child anchor yshift}{0pt},
  adjust childrens child anchors/.style={
    if n children>=2{
      before packing={
        tempdima/.max={max_y}{children},
        for children={
          child anchor yshift=tempdima()-max_y()
        },
      }
    }{}
  },
  default preamble={
    for tree={
      edge path'={(!u.parent anchor)--([yshift=\forestoption{child anchor yshift}].child anchor)},
      adjust childrens child anchors
    }
  },
}


\begin{document}

\frame{

\begin{forest}
[S
 [\alt<1>{XP}{NP1234}]
 [\alt<1>{YP}{NP1234}]
 [\alt<1>{ZP}{NP1234}]
 [\ldots, visible on=<1>]
 [{\alt<1>{H}{V} \sliste{ \alt<1>{XP}{NP}, \alt<1>{YP}{NP}, \alt<1>{ZP}{NP}\visible<1>{, \ldots} }}
   [{V \sliste{ NP, NP, NP }}, visible on=<1>,no edge]]]
\end{forest}

\pause

}


\end{document}

Editar: alargamos los NP agregando 1234 para que el salto sea realmente obvio.

Answer 1

Este puede ser un primer paso hacia una solución. Agregué una clave min widtha la que se pueden pasar los dos textos diferentes. Sí, sería mucho mejor si se pudiera cambiar \altpara hacerlo automáticamente, pero no pude hacerlo debido a problemas de expansión. (Ni siquiera sé contra quién estaba luchando la expansión, beamero forest.)

\documentclass{beamer}

\usepackage{forest}

% http://tex.stackexchange.com/questions/167690/presenting-a-forest-tree-from-bottom-to-top-in-beamer
% showing and hiding nodes and edges in forest
\tikzset{
    invisible/.style={opacity=0,text opacity=0},
    visible on/.style={alt=#1{}{invisible}},
    alt/.code args={<#1>#2#3}{%
      \alt<#1>{\pgfkeysalso{#2}}{\pgfkeysalso{#3}} % \pgfkeysalso doesn't change the path
    },
}
\forestset{
  visible on/.style={
    for tree={
      /tikz/visible on={#1},
      edge={/tikz/visible on={#1}}}}}

\newcommand{\sliste}[1]{%
\mbox{%
$\left\langle\mbox{\upshape\scshape #1}\right\rangle$}%
}

% specification for all trees, "default preamble" appends to existing specification.
% The version with apostrophe replaces it.
\forestset{default preamble'={
    for tree={align=center,parent anchor=south, child anchor=north,anchor=north,base=bottom},
    before drawing tree={
      sort by=y,
      for min={tree}{baseline}
    }
  }}


\forestset{
  declare dimen={child anchor yshift}{0pt},
  adjust childrens child anchors/.style={
    if n children>=2{
      before packing={
        tempdima/.max={max_y}{children},
        for children={
          child anchor yshift=tempdima()-max_y()
        },
      }
    }{}
  },
  default preamble={
    for tree={
      edge path'={(!u.parent anchor)--([yshift=\forestoption{child anchor yshift}].child anchor)},
      adjust childrens child anchors
    }
  },
}


\begin{document}
\tikzset{min width/.style n args={2}{/utils/exec={\pgfmathparse{max(width("#1"),width("#2"))}
 \edef\mywidth{\pgfmathresult}},
 text width={\mywidth pt}}}
\frame{

\begin{forest}
[S
 [\alt<1>{XP}{NP1234},min width={XP}{NP1234}]
 [\alt<1>{YP}{NP1234},min width={YP}{NP1234}]
 [\alt<1>{ZP}{NP1234},min width={ZP}{NP1234}]
 [\ldots, visible on=<1>]
 [{\alt<1>{H}{V} \sliste{ \alt<1>{XP}{NP}, \alt<1>{YP}{NP}, \alt<1>{ZP}{NP}\visible<1>{, \ldots} }}
   [{V \sliste{ NP, NP, NP }}, visible on=<1>,no edge]]]
\end{forest}

\begin{tikzpicture}[overlay,remember picture] 
\draw[red] (current page.south west) grid (current page.north east); 
\end{tikzpicture}
\pause

}


\end{document}

La cuadrícula roja es sólo para guiar la vista.