bug#21643: 25.0.50; Error "<nil> <down-mouse-1> is undefined"

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 8 Oct 2015 11:39:44 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 21643@debbugs.gnu.org
> 
> 1. Start Emacs with an MS Windows shortcut that has this target:
> runemacs.exe -Q --debug-init -l "onetest4.el" -f "1on1-emacs" "onetest4.el"
> 
> 2. Click the title bar of the minibuffer frame (not needed, but
>    just to make sure the frame is selected.
> 
> 3. C-h k
> 
> 4. Click mouse-1 somewhere in the second line of the minibuffer frame.
> 
> You see this message:
> <nil> <down-mouse-1> (translated from <down-mouse-1>) at that spot is undefined

Thanks.  There's clearly some display bug that shows in the minibuffer
frame: look carefully and you will see that the fringes and the scroll
bar only extend for a single line there.  The second line is some kind
of "no-man's land", which explains the "nil" part in the mouse event.

If you drag the lower edge of the minibuffer frame by even a single
pixel, then return it back to its original (or even smaller) height,
the problem with the fringes goes away, and so does the problem with
the mouse click.

I will take a look.

Martin, this looks somewhat similar to the problem you solved the
other day, whereby "M-x" echo would not be visible.  So maybe you
could look into this as well, if you have time.