Beamer: columns independent

Question

I don't know why, but on beamer, when the size of the content on the left column changes between two slides, the position of the right column text also change. For example, if you compile the following code, you will see that at each slide, the A on the left column always change its position.

Do you know how to avoid that?

Thanks!

MWE

\documentclass[]{beamer}
\begin{document}

\begin{frame}{Test}
  \begin{columns}
    \begin{column}{.4\textwidth}
      A
    \end{column}
    \begin{column}{.4\textwidth}%
      \only<1>{B}
      \only<2>{C\\D}
      \only<3>{C\\D\\E}
      \only<4>{C\\D\\E\\F}
    \end{column}
  \end{columns}
\end{frame}

\end{document}

Answer 1

As default alignment, beamer centres the content vertically. In this particular case the columns environment as a whole is centred. If you add content to the right column, the columns environment becomes taller, thus the position changes to keep it in the centre.

A very easy workaround: use top aligned frames

The a bit more complicate answer: instead of \only, you can use \uncover or \visible to already reserve space for content that will be revealed step by step.

\documentclass[]{beamer}
\begin{document}

\begin{frame}[t]{Test}
  \begin{columns}
    \begin{column}{.4\textwidth}
      A
    \end{column}
    \begin{column}{.4\textwidth}%
      \only<1>{B}
      \only<2>{C\\D}
      \only<3>{C\\D\\E}
      \only<4>{C\\D\\E\\F}
    \end{column}
  \end{columns}
\end{frame}

\begin{frame}{Test}
  \begin{columns}
    \begin{column}{.4\textwidth}
      A
    \end{column}
    \begin{column}{.4\textwidth}%
      \uncover<1->{B}

      \uncover<2->{C}

      \uncover<3->{D}

      \uncover<4->{E}
    \end{column}
  \end{columns}
\end{frame}

\end{document}

Answer 2

I have a first solution, which is a bit verbose because it needs first this [great code][1] and then it adds a third empty column, but for now it's the best I can do. I'll also look at overlayarea as proposed by samcarter.

\documentclass[]{beamer}

% https://tex.stackexchange.com/questions/44218/set-image-to-full-all-available-space-in-beamer-without-overlapping-other-eleme/44298#44298
% Chate sidebarthemefalse to sidebarthemetrue if you have a sidebar
\newif\ifsidebartheme
\sidebarthemefalse

\newdimen\contentheight
\newdimen\contentwidth
\newdimen\contentleft
\newdimen\contentbottom
\makeatletter
\newcommand*{\calculatespace}{%
    \contentheight=\paperheight%
    \ifx\beamer@frametitle\@empty%
        \setbox\@tempboxa=\box\voidb@x%
      \else%
        \setbox\@tempboxa=\vbox{%
          \vbox{}%
          {\parskip0pt\usebeamertemplate***{frametitle}}%
        }%
        \ifsidebartheme%
          \advance\contentheight by-1em%
        \fi%
      \fi%
    \advance\contentheight by-\ht\@tempboxa%
    \advance\contentheight by-\dp\@tempboxa%
    \advance\contentheight by-\beamer@frametopskip%
    \ifbeamer@plainframe%
    \contentbottom=0pt%
    \else%
    \advance\contentheight by-\headheight%
    \advance\contentheight by\headdp%
    \advance\contentheight by-\footheight%
    \advance\contentheight by4pt%
    \contentbottom=\footheight%
    \advance\contentbottom by-4pt%
    \fi%
    \contentwidth=\paperwidth%
    \ifbeamer@plainframe%
    \contentleft=0pt%
    \else%
    \advance\contentwidth by-\beamer@rightsidebar%
    \advance\contentwidth by-\beamer@leftsidebar\relax%
    \contentleft=\beamer@leftsidebar%
    \fi%
}
\makeatother

\begin{document}


\begin{frame}{Test}
  \begin{columns}
    \begin{column}{.4\textwidth}
      A
    \end{column}
    \begin{column}{.4\textwidth}%
      \only<1>{B}
      \only<2>{C\\D}
      \only<3>{C\\D\\E}
      \only<4>{C\\D\\E\\F}
    \end{column}
    \begin{column}{0pt}
      \calculatespace%
      \vline height 0.95\contentheight
    \end{column}
  \end{columns}
\end{frame}

\end{document}

Edit: Here is the same thing, but with \parbox instead. The code has the same length because the "hard" part is to guess the height, and that code is needed in both solutions.

\documentclass[]{beamer}

% https://tex.stackexchange.com/questions/44218/set-image-to-full-all-available-space-in-beamer-without-overlapping-other-eleme/44298#44298
\newif\ifsidebartheme
\sidebarthemetrue

\newdimen\contentheight
\newdimen\contentwidth
\newdimen\contentleft
\newdimen\contentbottom
\makeatletter
\newcommand*{\calculatespace}{%
    \contentheight=\paperheight%
    \ifx\beamer@frametitle\@empty%
        \setbox\@tempboxa=\box\voidb@x%
      \else%
        \setbox\@tempboxa=\vbox{%
          \vbox{}%
          {\parskip0pt\usebeamertemplate***{frametitle}}%
        }%
        \ifsidebartheme%
          \advance\contentheight by-1em%
        \fi%
      \fi%
    \advance\contentheight by-\ht\@tempboxa%
    \advance\contentheight by-\dp\@tempboxa%
    \advance\contentheight by-\beamer@frametopskip%
    \ifbeamer@plainframe%
    \contentbottom=0pt%
    \else%
    \advance\contentheight by-\headheight%
    \advance\contentheight by\headdp%
    \advance\contentheight by-\footheight%
    \advance\contentheight by4pt%
    \contentbottom=\footheight%
    \advance\contentbottom by-4pt%
    \fi%
    \contentwidth=\paperwidth%
    \ifbeamer@plainframe%
    \contentleft=0pt%
    \else%
    \advance\contentwidth by-\beamer@rightsidebar%
    \advance\contentwidth by-\beamer@leftsidebar\relax%
    \contentleft=\beamer@leftsidebar%
    \fi%
}
\makeatother

\begin{document}


\begin{frame}{Test}
  \begin{columns}
    \begin{column}{.4\textwidth}
      \calculatespace
      % https://tex.stackexchange.com/questions/83672/beamer-vertically-center-picture-inside-overlayarea
      \parbox[t][\contentheight][t]{\linewidth}{
        A
      }
    \end{column}
    \begin{column}{.4\textwidth}%
      \only<1>{B}
      \only<2>{C\\D}
      \only<3>{C\\D\\E}
      \only<4>{C\\D\\E\\F}
    \end{column}
  \end{columns}
\end{frame}

\end{document}



  [1]: https://tex.stackexchange.com/questions/44218/set-image-to-full-all-available-space-in-beamer-without-overlapping-other-eleme/44298#44298