bug#68698: 30.0.50; Making xt-mouse emit `wheel-up/down`

[Jared Finder]

On 2024-01-24 23:30, Eli Zaretskii wrote:
> > Date: Wed, 24 Jan 2024 15:31:32 -0500
> > From:  Stefan Monnier via "Bug reports for GNU Emacs,
> >  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> >
> > Package: Emacs
> > Version: 30.0.50
> >
> >
> > Currently, wheel-up/down events are generated in most setups instead
> > of the old mouse-4/5.  There are still two exceptions:
> > - X11 builds not using XInput2.
> > - text terminals.
> > The attached patch intends to fix the second bullet.
> > Text terminals themselves only give us info equivalent to `mouse-4/5`
> > and don't actually tell us that it's a wheel movement, but we can 
> > still
> > turn those things into `wheel-up/down`.
> >
> > This is related to bug#49803.
>
> Jared, any comments on the patch, or related issues?
>
> Thanks.
>
> > The second step would be to do something similar for the non-XInput2 
> > X11
> > build: make it generate `wheel-up/down` events according to
> > `mouse-wheel-down/up-event` settings.  Then packages like
> > `completion-preview` and `mwheel` won't need to pay attention to the
> > (confusingly named) `mouse-wheel-down/up-event` vars any more.

I'll be so happy if everything switches over to mouse-up / mouse-down 
events.  This would be great.  I'd love to ignore mouse-wheel-down-event 
and mouse-wheel-down-alternate-event.

> > diff --git a/lisp/mwheel.el b/lisp/mwheel.el
> > @@ -231,12 +239,24 @@ xterm-mouse--read-event-sequence
> >               ;; event: assume, that the last button was button 1.
> >               (t 1)))
> >         (sym (if move 'mouse-movement
> > -              (intern (concat (if ctrl "C-" "")
> > -                              (if meta "M-" "")
> > -                              (if shift "S-" "")
> > -                              (if down "down-" "")
> > -                              "mouse-"
> > -                              (number-to-string btn))))))
> > +             (intern
> > +              (concat
> > +               (if ctrl "C-" "")
> > +               (if meta "M-" "")
> > +               (if shift "S-" "")
> > +               (if down "down-" "")
> > +               (cond
> > +                ;; BEWARE: `mouse-wheel-UP-event' corresponds to
> > +                ;; `wheel-DOWN' events and vice versa!!
> > +                ((xterm-mouse--same-button-p mouse-wheel-down-event 
> > btn)
> > +                 "wheel-up")
> > +                ((xterm-mouse--same-button-p mouse-wheel-up-event 
> > btn)
> > +                 "wheel-down")
> > +                ((xterm-mouse--same-button-p mouse-wheel-left-event 
> > btn)
> > +                 "wheel-left")
> > +                ((xterm-mouse--same-button-p mouse-wheel-right-event 
> > btn)
> > +                 "wheel-right")

I think there is a bug with mouse-wheel-up/down/left/right-event and 
alternate event where it doesn't take window-system into account.  
Without fixing that bug, this won't work because it is valid for 
mouse-wheel-up-event to be wheel-down in a terminal.  A local run of 
HEAD (as of Jan 17, I'm at daec3e) with "./configure --with-pgtk" has 
mouse-wheel-up-event set to wheel-down because (featurep 'pgtk-win) is 
t, even with -nw on the command line.  Testing on Windows at Emacs 29.1 
shows the same behavior.

Also, I do not think xt-mouse knows how to generate mouse-6 or mouse-7 
events.  I think to generate events beyond mouse-5, you need to test 
against the 128 bit as well.  I don't have mouse hardware to confirm 
this behavior.

  -- MJF