Re: customizing `frame-background-mode'

[martin rudalics]

> As the documentation string says: "Set nil (default) if you want Emacs
> to examine the brightness for you".
>
> I think the [default] button is misleading into thinking it has
> something to do with the default value of frame-background-mode.
> Perhaps it should be changed from the button to ordinary text,
> because the [Value Menu] button prior to it has the same menu
> for selecting its value.  Also the tag "default" could be changed
> to something more descriptive like "default brightness".

The [Value Menu] and the [dark/light/default] button behave in exactly
the same manner.  I wonder whether they should do something different.
With other words, why not replace

  :type '(choice (choice-item dark)
                 (choice-item light)
                 (choice-item :tag "default" nil)))

by

  :type '(choice (const dark)
                 (const light)
                 (const :tag "default" nil)))

but probably I'm missing something here.