(frame-background-mode): Define a :set function

to update the background mode of existing frames.

1 files changed, 4 insertions, 0 deletions

diff --git a/lisp/faces.el b/lisp/faces.el
index 58b984ce876..2e3529fabf3 100644
--- a/lisp/faces.el
+++ b/lisp/faces.el
@@ -1432,6 +1432,10 @@ Set this to the symbol dark if your background color is dark, light if
 your background is light, or nil (default) if you want Emacs to
 examine the brightness for you."
   :group 'faces
+  :set #'(lambda (var value)
+           (set var value)
+           (mapcar 'frame-set-background-mode (frame-list)))
+  :initialize 'custom-initialize-changed
   :type '(choice (choice-item dark) 
                  (choice-item light)
                  (choice-item :tag "default" nil)))