I don't know what I did caused Emacs to emit such a message:

<nil> <wheel-down> is undefined


enter image description here

How did I issue this input event?
In other words, what does this <nil> stand for?

Now I know how to reproduce it:

(emacs -Q, of course)

Put the mouse pointer

  • anywhere above the tool bar
  • at the edge of a frame

, then wheel.

As Drew and db48x suggested, I reported it as bug#63054.

emacs-version: 28.2
system-configuration: x86_64-w64-mingw32

  • Show your mouse/key-binding code that binds wheel-down etc. Do, somewhere, use [nil] in a binding? (First, repro with emacs -Q.) Provide a recipe that's step-by-step, showing what modes you're in, etc.
    – Drew
    Apr 23, 2023 at 13:53
  • @Drew: I will show it once I can, of course. But currently, I don't know what I did that led to such a message. And, there's no code that binds wheel-down in my configuration.
    – shynur
    Apr 23, 2023 at 14:01
  • @Drew: updated :-)
    – shynur
    Apr 23, 2023 at 14:51
  • It looks like you answered your own question - in the question itself. If the question is how you issued that event, the answer is that you rolled the mouse wheel over the menu bar. ;-)
    – Drew
    Apr 23, 2023 at 17:07

2 Answers 2


Now that you've added a mention that you see the same thing with emacs -Q, and you see it when you roll the mouse wheel over a menu-bar menu:

On MS Windows, at least, I see the same thing.

And I see it in every Emacs version back to 22. It may also be the case for 21 -- I don't have that version. (It's not the case for Emacs 20, because that treats the menu bar the same as the rest of the window wrt wheel rolling.)

Is this a bug? I doubt it, especially based on the longstanding behavior. I suspect it's just undocumented behavior. But maybe someone can find somewhere where this is documented.

If no one does that here, you might consider filing a bug report, M-x report-emacs-bug, at least to get this documented.

  • 1
    Thanks for testing each version, +1. |||| "I suspect it's just undocumented behavior." --- I'll spend some time trying (and that's it) to search the documentation and see whether the behavior is described. |||| "you might consider filing a bug report" --- I will, if I fail to find it in the documentation.
    – shynur
    Apr 23, 2023 at 17:20
  • 1
    Not reproducible with Gtk+ Emacs 28.2 on Linux, FWIW. There, rolling the mouse wheel over the menu bar has no visible effect and doesn't put anything in *Messages* either. (Also emacs -Q; had to be, my personal configuration turns off the menu bar.)
    – zwol
    Apr 23, 2023 at 17:37
  • I reported it. I guess you may be interested in it: see my updated question.
    – shynur
    Apr 24, 2023 at 16:20
  • 1
    Yes, I see it's Emacs bug #63054. Closed as not a bug but a feature - an undocumented feature. (Why shouldn't the <nil> event description be documented?)
    – Drew
    Apr 24, 2023 at 16:46
  • 1
    "Closed as not a bug but a feature" --- It doesn't matter, I'll change the title of the question (I'm not sure whether the terminology I used is concise and standard, you can edit it) so that even if it's not documented, other users can easily find this question via the Internet and notice the bug#63054 and this feature.
    – shynur
    Apr 24, 2023 at 19:08

You should see this instead:

<menu-bar> <wheel-down> is undefined
<menu-bar> <double-wheel-down> is undefined

Does it still happen if you start Emacs with -Q? If it does, then file a bug report using M-x report-emacs-bug. If it does not, then bisect your init file until you find the part that breaks it.

  • 1
    yes, with -Q. I will report it tomorrow to see what developers will reply. May I ask what you see? (I think I should add version information to the question.)
    – shynur
    Apr 23, 2023 at 16:54
  • I can't reproduce the behavior described in the question and see the behavior described in the answer above ( GNU Emacs 29.0.60, Linux Mint 21 Cinnamon).
    – Claudio
    May 1, 2023 at 16:42

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