Overlaying text: overlayarea vs overprint

[josephwright]

Looking to round out (most of) the ideas in beamerbaseoverlay, I'm struggling to see how overprint adds things. It's got a very odd interface, as it relies on \onslide but not in the way that this command works elsewhere. The internals also seem very strange, and I can't really see what it's needed for vs using overlayarea and \only or similar (e.g. \includegraphics<..>, which is what I do routinely).

Anyone got good examples here?

[samcarter]

In theory, overprint is superior to overlayarea as it automatically calculates the required height. In praxis, it does not work very well and does not seem to get used very often.

[samcarter]

Yes, I think \onslide and its variants did not really catch on. I think one problem is that it is hard to remember which of them does what. With distinctive names like \uncover it is much easier, so users used these instead.

[josephwright]

I am left wondering a little about \onslide (and to a lesser extend \pause) - \uncover, \only, etc. as you say are clearer.

What I do notice is that beamer's use of 'onslide in overprint is rather inconsistent with what happens otherwise, as something like

\begin{frame}
  \begin{overprint}
    \onslide<1>
    Some stuff
    \onslide<2>
    More stuff
  \end{overprint}
  Extra content
\end{frame}

shows Extra content on all slides, even though in general it shouldn't. I know Till documents that, but it's still a little awkward - I suspect it goes back a long way to before the idea of \uncover, etc., was established. On that basis, I think the approach we have where \only is suggested as the setup command works better.

[samcarter]

What do you mean with setup command in this context?

[josephwright]

@samcarter beame needs the different overprint parts to be set up using \onslide, whereas we are using \only.

[samcarter]

ah! Yes, I think \only etc will be much easier for users to use here.

[cfr42]

More-or-less random example:

\begin{frame}<1-| handout:1-2>{Explananda}
  \begin{block}{Qualia}
    \alert{Qualia} (sing.~\alert{quale}) are, very roughly, the ‘raw feels’ or phenomenal characters of some conscious mental states.

    They are the qualitative features possessed by some (conscious) experiences.
  \end{block}
  \begin{exampleblock}<2-| handout:1-2>{Examples}
    \begin{itemize}
      \begin{overprint}[\linewidth]
        \only<1| handout:0>{%
          \item[] \mbox{ }
        }%
        \only<2| handout:1>{%
          \item The raw look (visual feel) of red things.
          The phenomenal redness of post boxes, ripe tomatoes and oxygenated blood.
          \item The raw look of green things.
          The phenomenal greenness of healthy grass, evergreens and first aid boxes.
        }%
        \only<3| handout:2>{%
          \item The raw sounds (auditory feels) of police sirens and concertos.
          \item The raw feels of silk, sandpaper and cotton wool.
          \item The raw smells (olfactory feels) of baking bread, coffee and rotten eggs.
        }%
      \end{overprint}
    \end{itemize}
  \end{exampleblock}
\end{frame}
\begin{frame}<1-| handout:1-3>{Explananda}
  \begin{block}{What-It-Is-Likeness}
    The \alert{what-it-is-likeness} of certain conscious mental states refers to the fact that there is something it is like to be in those states.
  \end{block}
  \begin{exampleblock}<2->{Examples}
    \begin{itemize}
      \begin{overprint}[\linewidth]
        \only<1| handout:0>{%
          \item[] \mbox{ }
        }%
        \only<2| handout:1>{%
          \item What it is like to be a bat echolocating a moth.
          \item What it is like to be an octopus who has just discovered how to turn the lights out \autocite{godfrey-smith-mo}.
        }%
        \only<3| handout:2>{%
          \item What it is like to realise one believes the light-switching octopus didn't learn the trick by reading the small print.
          \item What it is like to calculate $2+2$ in one's head.
          \item What it is like to find the roots of $x^2+2x-3=0$ in one's head.
        }%
        \only<4| handout:3>{%
          \item What it is like to be a twelfth century boy experiencing one's first day as a monastic novice.
          \item What it is like to be an Ancient Greek slave giving birth.
          \item What it is like to experience menstrual cramping.
          \item What it is like to ejaculate.
        }%
      \end{overprint}
    \end{itemize}
  \end{exampleblock}
\end{frame}

Not sure it is a good example, though.

[josephwright]

Try with the latest checking:

\DocumentMetadata{tagging = on}
\documentclass{xbeamer}
\NewEnvironmentCopy{exampleblock}{block}
\ProvideDocumentCommand\autocite{m}{}
\begin{document}
\begin{frame}<1-| handout:1-2>
  \frametitle{Explananda}
  \begin{block}{Qualia}
    \alert{Qualia} (sing.~\alert{quale}) are, very roughly, the ‘raw feels’ or phenomenal characters of some conscious mental states.

    They are the qualitative features possessed by some (conscious) experiences.
  \end{block}
  \begin{exampleblock}<2-| handout:1-2>
    \blocktitle{Examples}
    \begin{overprint}
      \begin{itemize}
        \only<1| handout:0>{%
          \item[] \mbox{ }
        }%
        \only<2| handout:1>{%
          \item The raw look (visual feel) of red things.
          The phenomenal redness of post boxes, ripe tomatoes and oxygenated blood.
          \item The raw look of green things.
          The phenomenal greenness of healthy grass, evergreens and first aid boxes.
        }%
        \only<3| handout:2>{%
          \item The raw sounds (auditory feels) of police sirens and concertos.
          \item The raw feels of silk, sandpaper and cotton wool.
          \item The raw smells (olfactory feels) of baking bread, coffee and rotten eggs.
        }%
      \end{itemize}
    \end{overprint}
  \end{exampleblock}
\end{frame}

\begin{frame}<1-| handout:1-3>
  \frametitle{Explananda}
  \begin{block}{What-It-Is-Likeness}
    The \alert{what-it-is-likeness} of certain conscious mental states refers to the fact that there is something it is like to be in those states.
  \end{block}
  \begin{exampleblock}<2->
     \blocktitle{Examples}
     \begin{overprint}
       \begin{itemize} 
        \only<1| handout:0>{%
          \item[] \mbox{ }
        }%
        \only<2| handout:1>{%
          \item What it is like to be a bat echolocating a moth.
          \item What it is like to be an octopus who has just discovered how to turn the lights out \autocite{godfrey-smith-mo}.
        }%
        \only<3| handout:2>{%
          \item What it is like to realise one believes the light-switching octopus didn't learn the trick by reading the small print.
          \item What it is like to calculate $2+2$ in one's head.
          \item What it is like to find the roots of $x^2+2x-3=0$ in one's head.
        }%
        \only<4| handout:3>{%
          \item What it is like to be a twelfth century boy experiencing one's first day as a monastic novice.
          \item What it is like to be an Ancient Greek slave giving birth.
          \item What it is like to experience menstrual cramping.
          \item What it is like to ejaculate.
        }%
      \end{itemize}
    \end{overprint}
  \end{exampleblock}
\end{frame}
\end{document}

[cfr42]

You've provided a lovely example of what's wrong with overprint in beamer :) Try replacing \only with \onslide (the official interface), and whilst the result is understandable when you read the code, it's likely not what you meant.

I think you have to remove the grouping, too. That is, it wants e.g.

      \begin{overprint}[\linewidth]
        \onslide<1| handout:0>
          \item[] \mbox{ }
        \onslide<2| handout:1>
          \item The raw look (visual feel) of red things.
          The phenomenal redness of post boxes, ripe tomatoes and oxygenated blood.
          \item The raw look of green things.
          The phenomenal greenness of healthy grass, evergreens and first aid boxes.
        \onslide<3| handout:2>
          \item The raw sounds (auditory feels) of police sirens and concertos.
          \item The raw feels of silk, sandpaper and cotton wool.
          \item The raw smells (olfactory feels) of baking bread, coffee and rotten eggs.
      \end{overprint}

but this does not work properly with itemize, so it should actually be something more like

  \begin{exampleblock}<2-| handout:1-2>{Examples}
    \begin{overprint}[\linewidth]
      \onslide<1| handout:0>
      \begin{itemize}
        \item[] \mbox{ }
      \end{itemize}
      \onslide<2| handout:1>
      \begin{itemize}
        \item The raw look (visual feel) of red things.
          The phenomenal redness of post boxes, ripe tomatoes and oxygenated blood.
        \item The raw look of green things.
          The phenomenal greenness of healthy grass, evergreens and first aid boxes.
      \end{itemize}
      \onslide<3| handout:2>
      \begin{itemize}
        \item The raw sounds (auditory feels) of police sirens and concertos.
        \item The raw feels of silk, sandpaper and cotton wool.
        \item The raw smells (olfactory feels) of baking bread, coffee and rotten eggs.
      \end{itemize}
    \end{overprint}
  \end{exampleblock}

At the same time, you are not getting quite what I think you want either - the block having a predictable fixed size across all frames.

Hmm, yes. Well, as you point out, I'm not actually using it properly.

I think Till's mistake here is hoping he can insist on \onslide then typeset every single bit in each pass (that's only apparent when you read the code). I think what's wanted instead is a multi-pass approach that means the user can put 'whatever' inside the overprint block, and the height is recorded between runs.

Actually, it does seem to work correctly (at least in this case) if I change my example to follow the documented method. Try:

\documentclass{beamer}
\usetheme{Warsaw}
\usepackage{biblatex}
\begin{document}
\begin{frame}<1-| handout:1-2>{Explananda}
  \begin{block}{Qualia}
    \alert{Qualia} (sing.~\alert{quale}) are, very roughly, the ‘raw feels’ or phenomenal characters of some conscious mental states.

    They are the qualitative features possessed by some (conscious) experiences.
  \end{block}
  \begin{exampleblock}<2-| handout:1-2>{Examples}
    \begin{overprint}[\linewidth]
      \onslide<1| handout:0>
      \begin{itemize}
        \item[] \mbox{ }
      \end{itemize}
      \onslide<2| handout:1>
      \begin{itemize}
        \item The raw look (visual feel) of red things.
          The phenomenal redness of post boxes, ripe tomatoes and oxygenated blood.
        \item The raw look of green things.
          The phenomenal greenness of healthy grass, evergreens and first aid boxes.
      \end{itemize}
      \onslide<3| handout:2>
      \begin{itemize}
        \item The raw sounds (auditory feels) of police sirens and concertos.
        \item The raw feels of silk, sandpaper and cotton wool.
        \item The raw smells (olfactory feels) of baking bread, coffee and rotten eggs.
      \end{itemize}
    \end{overprint}
  \end{exampleblock}
\end{frame}
\begin{frame}<1-| handout:1-3>{Explananda}
  \begin{block}{What-It-Is-Likeness}
    The \alert{what-it-is-likeness} of certain conscious mental states refers to the fact that there is something it is like to be in those states.
  \end{block}
  \begin{exampleblock}<2->{Examples}
    \begin{overprint}[\linewidth]
      \onslide<1| handout:0>
      \begin{itemize}
        \item[] \mbox{ }
      \end{itemize}
      \onslide<2| handout:1>
      \begin{itemize}
        \item What it is like to be a bat echolocating a moth.
        \item What it is like to be an octopus who has just discovered how to turn the lights out \autocite{godfrey-smith-mo}.
      \end{itemize}
      \onslide<3| handout:2>
      \begin{itemize}
        \item What it is like to realise one believes the light-switching octopus didn't learn the trick by reading the small print.
        \item What it is like to calculate $2+2$ in one's head.
        \item What it is like to find the roots of $x^2+2x-3=0$ in one's head.
      \end{itemize}
      \onslide<4| handout:3>
      \begin{itemize}
        \item What it is like to be a twelfth century boy experiencing one's first day as a monastic novice.
        \item What it is like to be an Ancient Greek slave giving birth.
        \item What it is like to experience menstrual cramping.
        \item What it is like to ejaculate.
      \end{itemize}
    \end{overprint}
  \end{exampleblock}
\end{frame}
\end{document}

But the different approaches for overlayarea and overprint (and the fact that there are two of them at all) is not great, imho.

[cfr42]

Try with the latest checking:

I get tagpdf complaints about the structure. Is that expected?

[josephwright]

At the moment, sadly yes - I need to work on the tagging structure a bit - I have a list of 'needs fixing' things to do before I add any more functionality, and will be working on those.

[josephwright]

@cfr42 Thanks to help from @u-fischer, should now be sorted