Text that doesn't affect the placement of other text

Question

I would like to be able to put blocks of text in a document that don't affect the layout of the main part of it. (Specifically, I'm writing the solutions to a previously written exam; I'd like to be able to add the solutions in without causing the text from the original exam to move around.)

For what it's worth, the original spacing was largely handled via "\vfill", and I'd like those to still take up the same amount of space. (In principle, this means that if a solution were too long, it would run over and end up on top of the next problem, and I expected to have to manually check that this doesn't happen.)

Update: Here's an example, except that it isn't doing the spacing quite right. (The stuff in typewriter font is the solutions.) The point is that I want to leave the spacing of the original exam content alone, while inserting the solutions---complete with formatting---in the gaps left behind. In the unlikely event that there isn't enough space, I expect that any solution might cause crazy things to happen, but I'd like the typical case, that my solution fits in the space allotted, to be relatively seamless.

Answer 1

There are multiple possibilities for this, dependent what you exactly need.

You can use \llap{<text>} and \rlap{<text>} to add text which doesn't take any horizontal space and laps to the left or right, respectively.

With \raisebox{<raise amount>}[<set height>][<set depth>]{<text>}, i.e. \raisebox{0pt}[0pt][0pt]{<text>} you can set the height and depth of the text to zero (without actually raising it). This is also done with the \smash{<text>} macro.

For example you could use \llap{\smash{<text>}} to place some text to the left of the current position without taking any vertical or horizontal space. However, this will enter horizontal mode, e.g. start a new paragraph if you are just between paragraphs.

Then there is my adjustbox package provides the keys set height, set depth and lap, e.g. \adjustbox{set height=0pt,set depth=0pt,lap=-\width}{<text>} would be the same as the above mentioned \llap{\smash{<text>}}. In this specific case there is no real benefit to use that package, but you can easily add more, e.g. the minipage or fbox key if you need line breaking or a frame, respectively. See my answer to Positioning of text (box) relative to other text for an example.

Finally you can place text to absolute positions of the current page using TikZ if you use the remember picture,overlay options. With overlay the whole picture doesn't take any space as well. The text would then be part of a \node {<text>};

Answer 2

\newsavebox{\zerobox}
\newenvironment{nospace}
  {\par\edef\theprevdepth{\the\prevdepth}\nointerlineskip
   \setbox\zerobox=\vtop to 0pt\bgroup
   \hrule height0pt\kern\dimexpr\baselineskip-\topskip\relax
  }
  {\par\vss\egroup\ht\zerobox=0pt \wd\zerobox=0pt \dp\zerobox=0pt
   \box\zerobox}

Here ends the text of the question

\begin{nospace}
Here is the solution
\end{nospace}

\vfill

Here is a sample document:

\documentclass[a4paper]{article}
\usepackage{multicol}
\newsavebox{\zerobox}
\newenvironment{nospace}
  {\par\edef\theprevdepth{\the\prevdepth}\nointerlineskip
   \setbox\zerobox=\vtop to 0pt\bgroup
   \hrule height0pt\kern\dimexpr\baselineskip-\topskip\relax
}
  {\par\vss\egroup\ht\zerobox=0pt \wd\zerobox=0pt \dp\zerobox=0pt
   \box\zerobox}

\begin{document}
Some text that may have descenders

\begin{nospace}
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
Here is some text
\end{nospace}

\vspace{10cm}

\textbf{And here is something else}

\newpage
Some text that may have descenders

\vspace{10cm}

\textbf{And here is something else}



\end{document}

Here is the result, that shows that the insertion takes up no space

Answer 3

Cheat a bit! Print the answer in white! Later on you can just change the color to a normal color. (You can write a macro for this).

\documentclass{article}
\usepackage{xcolor}
\usepackage{lipsum}
\parindent0pt
\begin{document}

\textbf{Question}

\lipsum[1]

\textbf{Answer}

\textcolor{white}{
  \lipsum[1]}

\textbf{Question}

\end{document}