Smaller font sizes in boitecoloriee environment gives bad result

Question

The boites package defines environments that allow page breaks inside framed boxes whose edges may be variously fancy. The bundle includes a few examples (shaded box, box with a wavy line on its side, etc).

boitecoloriee is one of those environments. It typesets its contents in a gray background color inside a framed box.

With smaller fonts the lines typeset with this environment are cut in its bottom, as can be seen with the following example:

\documentclass{standalone}
\usepackage{boites,boites_exemples}
\usepackage{lipsum}

\begin{document}

\begin{boitecoloriee}
  \lipsum[131]
\end{boitecoloriee}

\footnotesize

\begin{boitecoloriee}
  \lipsum[131]
\end{boitecoloriee}

\end{document}

which gives:

Notice how the second box has defective lines.

Does anybody have any idea on how to fix this?

Answer 1

It seems to be a bug in boites.sty that makes wrong assumptions about how to paint the background line by line. Indeed, if you say

\footnotesize

\begin{boitecoloriee}\baselineskip=12pt
  \lipsum[131]
\end{boitecoloriee}

the lines are not cut. So it's just that when the following line is typeset, it's assumed to be too high and it covers part of the line above.

Answer 2

I think I have found a fix to this issue: add the following line

\splittopskip\z@

just before the line

\baselineskip\z@

in the definition of \endbreakbox in boites.sty

The \splittopskip parameter specifies the glue that TeX inserts at the top of a box resulting from a \vsplit. \splittopskip plays the same role that \topskip plays for a page.