bug#65070: 29.1; (Only on Windows) Both touchpad scroll gestures scroll the screen up and down.

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: kzhr@d1.dion.ne.jp,  hiroya.ebine1@gmail.com,  max@mal-richtig.de,
>   65070@debbugs.gnu.org
> Date: Sun, 20 Aug 2023 15:04:40 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > And another question: what if PIXEL-DELTA provides deltas that are
> > smaller than one screen line -- what should the LINES member of the
> > wheel-up/down event be in that case?  The code both in w32term.c and
> > xterm.c produces NO_EVENT event in those cases, AFAICT, so it sounds
> > like we cannot support such fine scrolling amounts?  Or did I miss
> > something?
> 
> Actually, LINES is only meant to be produced under NS, where the window
> system allegedly provides this information.  handle_one_xevent and most
> other terminals merely set LINES to nil.

So, when PIXEL-DELTA is non-nil, LINES is (or should be) ignored?
What happens on NS, which does provide this information?