bug#37802: 27.0.50; Feature request: hook for theme enabling/disabling

["Óscar Fuentes" <ofv@wanadoo.es>]

I'm experimenting with some code that uses face-remap-add-relative to
modify colors on specific windows. It takes the attribute of an existing
face, alters it and uses :filtered to apply the change conditionally. On
my specific case I use that technique for darkening the default
background of the windows that have no keyboard focus.

However, when I switch themes I have to manually force the recalculation
of the "darked" background to adapt it to the new theme. If I had a hook
that fires *after* a theme is enabled or disabled, I could automatize
the recalculation.

I looked at custom.el and the change seems simple enough so I wonder if
there is any reason for not implementing such hook.


In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit)
 of 2019-09-12 built on sky
Repository revision: 421084d2cb160261b259bddb687bb2c234f8f1ef
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12004000
System Description: Debian GNU/Linux bullseye/sid