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

From: Jared Finder <[email-masked]>
Date: Thu, 25 Jan 2024 17:41:20 -0800

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" <[email-masked]>
>> 
>> 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