bug#33320: 27.0.50; `describe-key' fails to display help for C-mouse-3

[Drew Adams]

> in this case I wasn't looking for the documentation of one
> of the menu items, I was looking for the
> documentation for whatever function pops up the menu itself.

I know of no good answer for that.  Maybe it should be an
enhancement request.

You can find out which keymap the prefix key is bound to by
doing this:

M-x pp-eval-expression
(lookup-key (current-global-map) (kbd "C-<down-mouse-3>"))

But you have to know whether it is <down-mouse-3> or <mouse-3>
that has the binding.  And that evaluation does not tell you
the name of a variable that might be bound to the keymap.  It
just shows you the keymap itself.