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

[Dmitry Gutov]

On 17.10.2019 11:25, martin rudalics wrote:
>  > 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.

I think we can think of this "subarea" as directly corresponding to an 
Emacs window for the purposes of this discussion, when we think how 
diff-mode should display things.