bug#68213: 30.0.50; completion-preview-tests failure in --without-x build

[Stefan Monnier]

>> But why is `mouse-4` sometimes on `mouse-wheel-down-event` and sometimes
>> on `mouse-wheel-down-alternate-event`?  What difference does it make?

Any chance you could try and help me figure out answers to those questions?

At the very least we have a documentation problem because, as a user
reading the docstring of `mouse-wheel-down-alternate-event`, I have no
idea what this means or does and how it differs from
`mouse-wheel-down-event`.

`mouse-wheel-down-event` is a defcustom because X11 failed
to define events for scroll wheel, and depending on your mouse, those
were not always mapped to the same `mouse-N` events.  That doesn't seem
to apply to `mouse-wheel-down-alternate-event`.

>> But, AFAICT the `wheel-up/down` events always mean the same, so I think
>> `mwheel.el` should just always bind `wheel-DIR` events and then the
>> `mouse-wheel-DIR-event` vars are used only for those cases where other
>> events also need to be bound, like in the patch below, WDYT?
> I think we should let sleeping dogs lie,

These vars were new in Emacs-29, so they're still pretty awake, AFAIC.

> because the last time changes were made to these options in mwheel.el,
> several obscure problems emerged under text terminals that required
> another round of changes, yielding the current values.

Do you happen to remember the bug numbers of bug titles or something to
help me find info about those obscure problems?


        Stefan