Can I use a TeX primitive in a "before" and "after" macro? (and how?)

Question

The Question

Can I use a TeX primitive in a "before" and "after" macro? (and how?)

There are two questions that I found useful and related to my question, which sent me in the right direction: how to even ask this question!

• What are the different kinds of boxes in (La)TeX?
• Why does LaTeX make a distinction between commands and environments?
• How to make a list of unbreakable items?
• How to prevent pagebreak in description environment

Example Situation

I am using a custom list setup with the enumitem package and I would like to use a primitive in the variables below:

\newlist{legal}{enumerate}{10}
\setlist[legal]{label*=\texttt{\arabic*.},resume,before={<HERE>}, after={<HERE>}}

I would like to put \vbox{ in the before={} and } in the after={}, but obviously I cannot type before={\vbox{}, after={}}

Why would I want to do this? For example, I could want to put a box around each mother and daughter list item, such that they remain on the same page. Or maybe I would like to put other primitives around my list environment just for kicks. Is there any way to do this?

Answer 1

You can use

\vbox\bgroup

and

\egroup 

to start the box without using {} so you can pass these constructs in {} delimited arguments, but they are not supported latex commands and things will go wrong if you do.

But this should not be necessary for example to put \fbox around a list you should not do that you should use the lrbox environment which was explicitly added to latex for that example. (Or a package such as framed or mdframed)