custom--inhibit-theme-enable

custom-theme-set-*を無視して設定できる。userの設定のみ受け付けたい場合は apply-only-userに設定できる。

nilにすることで一時的なthemeを割り当てたいのだろう。

table: 設定可能な値

value

nil どんなthemeでも有効

apply-only-user user themeのみ有効

* どんな時も無効

code: custom.el

(defvar custom--inhibit-theme-enable 'apply-only-user

"Whether the custom-theme-set-* functions act immediately.

If nil, custom-theme-set-variables' and custom-theme-set-faces'

change the current values of the given variable or face. If

t, they just make a record of the theme settings. If the

value is `apply-only-user', then apply setting to the

`user' theme immediately and defer other updates.")