bug#37774: 27.0.50; new :extend attribute broke visuals of all themes and other packages

[Juri Linkov]

> I miss you here.  Emacs now by default also extends the region to the
> right window edge.

Emacs doesn't extend the region to the right window edge when the region
face was already customized, and has no "extend t" in the init file.

>> Also I looked how other applications extend diff blocks, and e.g.
>> GitLab extends diff background colors to the window right edge,
>> not to EOL, for example,
>> https://github.com/emacs-mirror/emacs/commit/3d6075e3ee8c447f8974b37007a1b1ae1af8917c
>
> With Firefox these diffs are boxed in a subarea of the Firefox window.
> They do not start or extend at the window edges and text in these
> boxes is static, can neither overflow into a newline nor be broken.

This is why I proposed to limit these boxes to some fixed column
like fill-column.

> But I think that our (e)diff blocks are affected by the change and all
> their face settings probably have to change, as well as tables and
> listings.

Yes, (e)diff face settings have to change, but actually I discovered
that diff-refined faces don't need to extend to the window edge,
because they don't form a block, they are word-based.