Add whitespace around a box

Question

I want to put some text in a box like \fcolorbox{red}{gray}{text} but such that moreover, the box is surrounded by an (non visible) space. So that if i put to such boxes near each other, there will be a small space between them. An such that if i put two such boxes in a \frac{}{} there will be some space between them and the fraction line. What would be the shortest way to do it ?

Answer 1

The adjustbox package provides \marginbox{<value(s)>}{<content>} which adds an margin, i.e. whitespace around all sites of the content. You can give either one value for all sites, two for left/right and top/bottom or four for left, bottom, right and top. Values must be separated by spaces.

Examples:

\usepackage{adjustbox}
% ...

\marginbox{1pt}{\fcolorbox{blue}{red}{text}}% Adds 1sp space around the box

\marginbox{1pt 0pt}{\fcolorbox{blue}{red}{text}}% Adds 1sp space to the left and right of the box

\marginbox{1pt 0pt 2pt 0pt}{\fcolorbox{blue}{red}{text}}% Adds 1sp space to the left and 2pt to the right of the box

There is also the margin key for \adjustbox{<key=value,...>}{<content>} from the same package. It also provides bgcolor (background color) and cfbox (colored framed box) which can be used as an replacement for \fcolorbox (but you still need to load xcolor).

\documentclass{article}
\usepackage{xcolor}
\usepackage{adjustbox}

\newcommand{\mybox}{\adjustbox{cfbox=blue,bgcolor=red,margin=1pt}}

\begin{document}

\fcolorbox{red}{green}{text}\fcolorbox{blue}{red}{text}

\adjustbox{cfbox=red,bgcolor=green,margin=1pt}{text}\mybox{text}

\end{document}

Answer 2

\DeclareRobustCommand{\roybox}[3]{%
  \ifdim\lastkern=1sp\,\fi\fcolorbox{#1}{#2}{#3}\kern1sp}

Now you can see the difference:

\fcolorbox{red}{green}{text}\fcolorbox{blue}{red}{text}

\roybox{red}{green}{text}\roybox{blue}{red}{text}

The small kern inserted by the macro will be unnoticeable (it's the minimum possible width and is less than the wavelength of visible light) if the box is not followed by another similar box: in this case, instead, it will be changed into a thin space \,.

I don't see any problem with fractions.