Load custom highlighting after colorscheme change

Question

I am a Vim user and i recently decided to try Emacs Spacemacs, i have a problem setting up custom highlighting, i set some lines like the following in my .spacemacs (i guess it's the same problem in your .emacs):
(set-face-background 'font-lock-comment-face nil) The idea is to always disable the background highlighting of "commented areas" but it has a problem, it works fine when starting Emacs but changing the theme resets it (the new theme overwrites it).
There is the same problem in Vim which is easily fixed by loading the custom colors after a theme has been loaded :
autocmd ColorScheme * call LoadMyCustomHighlighting() How do you translate that in elisp?

Note: I found what seems to be a similar question here but it don't understand it (elisp noob), i would want some actual working code with a basic explanation.

Answer 1

As discussed in the other question there are no hooks for this in load-theme. Neither is there in enable-theme, the function for enabling themes, which would be the right point to do this. The easiest solution is to add advice (code that is latched onto another function in some way).

(advice-add 'enable-theme :after #'aj/apply-face-definitions)

(defun aj/apply-face-definitions (&optional theme)
  "Do face definition stuff after loading theme."
  (set-face-attribute 'font-lock-comment-face nil :background nil))

set-face-attribute is used instead of set-face-background which “mostly provide compatibility with old versions of Emacs” according to the elisp manual.