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

[martin rudalics]

>> buffer-list-update-hook sounds like that infrastructure.

`window-selection-change-functions' please.

> But I think the real problem is how to define a window-specific
> default face.  It's not easy, and I'm not sure it will work.
> Something using the :filtered thingy, I guess?  But I'm not sure it
> will work for the default face.
>
> Basically, faces were never designed to be window-specific.  Even
> making them buffer-specific (via face-remapping-alist) is somewhat
> tricky.

Here I can write

(set-window-face-remapping-alist nil '((default (:background "yellow") 
default)))

It was pretty trivial to implement but lifting it from the rest of my
changes might be non-trivial.  If people are very, very interested, I
can give it a try.

martin