bug#50141: Current part of emacs red, other parts blue

[martin rudalics]

> But the request here is not to do this for a particular window, the
> request is to do this for _any_ window when it is selected.

We'd have to add a minor mode that puts its function on
`window-selection-change-functions'.  That function would simply move
the background from the old selected window to the new selected window
like

(set-window-face-remapping-alist
 (old-selected-window) '((default (:background nil) default)))
(set-window-face-remapping-alist
 nil '((default (:background background-of-selected-window) default)))

What else would we want?

martin