To be clear, Jean, are you conducting this review for Non-GNU ELPA?

> I think that longer lines shall be wrapped, you have to include word
> wrap, as otherwise lines will become smaller thant the original line!

Such a change is in progress.  I'm just about to stash some re-work of the
core logic for `moc-focus' to have general support for most cases.  It's
looking like 1k lines of rework and quite annoying.  I suspect there must
be a better way.

I can fit visual lines by using their horizontal and vertical height after
breaks to calculate what will provide the best aspect ratio.  Such a
calculation with reasonable accuracy can be done in one step without
troubling Emacs.  With some length of selection there is never anything I
can do to make the text big, but we can make it pretty.

The fundamental issue remains that translating overlays after such a reflow
is not so trivial.  That is unless I do the reflow within a buffer with
editing commands after copying all of the necessary information over
instead of stitching and welding overlays and strings together without the
aid of a buffer.  This would allow some savings by re-using editing logic
to preserve overlays and property applications to injected whitespace.
Instead of calculating things I can just read the final result of all the
edits.  This seems more robust and I think I will implement the easiest and
most relevant cases first:

- whitespace trimming of indentation
- whitespace injection to maintain column alignment of first line in source
- newline insertion to reflow long logical lines and match the target
aspect ratio

I might just need a break lol.