bug#65360: emacs 29.1 with MSYS2: vertical scrolling with touchpad not working

[Eli Zaretskii]

> From: Vincent Torri <vincent.torri@gmail.com>
> Date: Fri, 18 Aug 2023 07:51:45 +0200
> Cc: 65360@debbugs.gnu.org
> 
> >  Unfortunately, we don't currently have
> > anyone with access to such a machine who could debug the relevant code
> > and tell what is wrong with it.  If you can run Emacs under GDB on
> > that machine and report some findings (I can provide more detailed
> > instructions), we might be able to fix this.
> 
> I can do that, tell me what to do

Thank you.

The relevant code is in w32term.c:w32_construct_mouse_wheel.  For
starters, could you please step through that function and tell what
you see when you scroll with the touchpad?  In particular, does the
value of 'delta' become positive or negative depending on the
direction of the scrolling?  Also, what are the computed values of p.x
and p.y, and what are the values in the structure pointer to by
'result' immediately before the function returns?

Note: to be able to show values of Lisp objects, you need to tell GDB
to read the src/.gdbinit file in the Emacs source tree:

  (gdb) source /path/to/emacs/src/.gdbinit

P.S. It goes without saying that you will need to have the sources of
Emacs 29.1 available, if you don't already.