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

From: Stefan Kangas <[email-masked]>
Date: Sun, 16 Aug 2020 06:41:32 -0700

Eli Zaretskii <[email-masked]> writes:

> First, you don't need to do anything for vertical-scroll-bar, as the
> mouse wheel is already handled there, at least on my system.

Not here, unfortunately.  Tried emacs -Q with both GTK and Lucid: no
message from foo-mouse-message.

On GTK, I see this:

    "[The] 'bar' (inside the scroll bar) that indicates the current
    position strangely moves downwards slowly.  I get no error message,
    and the window doesn't scroll."

    https://debbugs.gnu.org/cgi/bugreport.cgi?bug=5557#28

On Lucid, nothing at all happens for the mouse wheel.  (Which is
actually better than the odd behaviour I see on GTK.)

> On a horizontal scroll-bar, if I use this:
>
>   (global-set-key [horizontal-scroll-bar wheel-up] 'foo-mouse-message)
>
> I get the expected result on my system.
>
> What do you see Emacs say if you turn the wheel on the horizontal
> scroll-bar in "emacs -Q"?

Same here: no message with the binding.  Instead:

On GTK, the horizontal scroll bar moves, but the window doesn't update.
The behaviour is similar to the vertical case: the 'bar' portion moves,
and when I then drag it with mouse-1, the window jumps to the position.

On Lucid, I see the same as for the vertical scroll bar: nothing happens.

So it's starting to sound like we have at least two separate bugs to
handle.

Best regards,
Stefan Kangas