tcolorbox: lines after break?

Question

Is there something equivalent to "lines before break" for the end part in tcolorbox? If there is I can't find it ;-)

The following box should have at least 3 lines on the second page. As the code is created automatically any solution that involves manual break points (like break at) is not suitable.

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{tcolorbox,lipsum}
\tcbuselibrary{skins,breakable}
\begin{document}
\begin{tcolorbox}[enhanced,colback=lightgray!20!white,frame hidden,breakable]
a\\b\\c\\d\\e\\f\\g
\lipsum[1-4]
\end{tcolorbox}

\end{document}

Answer 1

There is a (very limited) support for that by using the enlargepage flexible option from version 3.12 (2014/07/29). This allows to enlarge the pre-last (becoming last) page to avoid such lonely lines. For example:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{tcolorbox,lipsum}
\tcbuselibrary{skins,breakable}
\begin{document}
\begin{tcolorbox}[enhanced,colback=lightgray!20!white,frame hidden,breakable,
  enlargepage flexible=\baselineskip
  ]
a\\b\\c\\d\\e\\f\\g
\lipsum[1-4]
\end{tcolorbox}

\end{document}

Here, you avoid a single lonely line. If you insert some more lines, 2 lines will flip to the next page.

To avoid 2 lonely lines, you could use enlargepage flexible=2\baselineskip. Naturally, the enlarged page will become too large if you continue with that to higher values.

Note that this will not protect from getting a lonely line from one paragraph which is in the mid of other paragraphs. But at least, the worst case (a framed single line at the end) can be avoided...