bug#5557: <left-margin> <double-wheel-down> is undefined

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: lennart.borgman@gmail.com,  5557@debbugs.gnu.org
> Date: Tue, 01 Oct 2019 18:19:30 +0200
> 
> After
> 
> (set-window-margins (get-buffer-window) 10 10)
> 
> and I try to do any mouse stuff there, I get
> 
> <left-margin> <down-mouse-1> is undefined
> <left-margin> <mouse-1> is undefined
> 
> (I don't have a mouse with a scroll wheel.)
> 
> So I guess what should be changed is this:
> 
>   (when mouse-wheel-mode
>     (dolist (event (list mouse-wheel-down-event mouse-wheel-up-event mouse-wheel-right-event mouse-wheel-left-event))
>       (dolist (key (mapcar (lambda (amt) `[(,@(if (consp amt) (car amt)) ,event)])
>                            mouse-wheel-scroll-amount))
>         (global-set-key key 'mwheel-scroll)
>         (push key mwheel-installed-bindings)))))
> 
> to also work in left-margin/right-margin?  It's a bit difficult for me
> to test since I don't have a scroll wheel -- can somebody who has one do
> the additional key bindings?  (The code is in mwheel.el.)

I actually am not sure a click on the margins should produce the same
effect as on the text area.  The margins are used to display different
text from what's in the text area, so I'm not sure I understand the
rationale.

Does anyone else have an opinion on this?  Should we perhaps ask a
couple of people who maintain packages that display on the margins?