Why the `click' modifier for a mouse-wheel event?

Why the `click' modifier for a mouse-wheel event?

[Drew Adams]

Subject line says it all.

In Emacs 22 (and 21, 20...), using the mouse wheel did not add any modifiers to
the event that was read.  In Emacs 23, `event-modifiers' for a
`mouse-wheel-down-event' or `mouse-wheel-up-event' returns `(click)'.

Why? Is this a bug or a feature or just an inescapable implementation
limitation?

This behavior doesn't seem right. Using the mouse wheel (without pressing it to
realize a click) is not the same as clicking a mouse button.

(I'm using Windows, so the `event-basic-type' for a wheel rotation is `wheel-up'
or `wheel-down'.)

RE: Why the `click' modifier for a mouse-wheel event?

[Drew Adams]

> Subject line says it all.
> 
> In Emacs 22 (and 21, 20...), using the mouse wheel did not 
> add any modifiers to
> the event that was read.  In Emacs 23, `event-modifiers' for a
> `mouse-wheel-down-event' or `mouse-wheel-up-event' returns `(click)'.
> 
> Why? Is this a bug or a feature or just an inescapable implementation
> limitation?
> 
> This behavior doesn't seem right. Using the mouse wheel 
> (without pressing it to
> realize a click) is not the same as clicking a mouse button.
> 
> (I'm using Windows, so the `event-basic-type' for a wheel 
> rotation is `wheel-up' or `wheel-down'.)

I might add that this can complicate user code. In a context where I know the
mouse wheel has been used, if I want to test for a keyboard (only) modifier, I
now need to do something like this:

(when (intersection (event-modifiers evnt)
                    '(shift control meta alt hyper super))
  ...)

instead of just (when (event-modifiers evnt) ...).
That brings in cl.el (or equivalent code) for `intersection'.

Not a biggee, if there's a good reason why `click' should be returned for a
mouse-wheel event. So...why?

Re: Why the `click' modifier for a mouse-wheel event?

[Chong Yidong]

"Drew Adams" <drew.adams@oracle.com> writes:

> Subject line says it all.
>
> In Emacs 22 (and 21, 20...), using the mouse wheel did not add any modifiers to
> the event that was read.  In Emacs 23, `event-modifiers' for a
> `mouse-wheel-down-event' or `mouse-wheel-up-event' returns `(click)'.

I think this change was made to make Windows behave like the other
ports.  IIRC, this was in response to a bug report by Lennart (?), but I
can't find it in the tracker right now.

Re: Why the `click' modifier for a mouse-wheel event?

[Jason Rumney]

Chong Yidong wrote:

> "Drew Adams" <drew.adams@oracle.com> writes:
>
>   
>> Subject line says it all.
>>
>> In Emacs 22 (and 21, 20...), using the mouse wheel did not add any modifiers to
>> the event that was read.  In Emacs 23, `event-modifiers' for a
>> `mouse-wheel-down-event' or `mouse-wheel-up-event' returns `(click)'.
>>     
>
> I think this change was made to make Windows behave like the other
> ports.  IIRC, this was in response to a bug report by Lennart (?), but I
> can't find it in the tracker right now.
>   

It was bug#687, about wheel events triggering mouse-avoidance, since 
they were not considered as mouse events.

RE: Why the `click' modifier for a mouse-wheel event?

[Drew Adams]

> >> In Emacs 22 (and 21, 20...), using the mouse wheel did not 
> >> add any modifiers to the event that was read.  In Emacs 23,
> >> `event-modifiers' for a `mouse-wheel-down-event' or
> >> `mouse-wheel-up-event' returns `(click)'.
> >
> > I think this change was made to make Windows behave like the other
> > ports.  IIRC, this was in response to a bug report by Lennart (?),
> > but I can't find it in the tracker right now.
> 
> It was bug#687, about wheel events triggering mouse-avoidance, since 
> they were not considered as mouse events.

Thanks for tracking that other bug down, Jason. But I don't understand why that
fix to bug #687 is TRT. It seems to me very wrong that a wheel event that does
not in any way involve the user pressing the wheel as a middle mouse button
should be treated as a mouse-button `click' event. I don't understand everything
about bug #687 (and it sounds, from reading it, like others might not either),
but this fix seems off-base.

And I was obviously wrong in my own last post in that bug thread, when I said
that I thought I would not need to change my own code because of your change. As
I mentioned earlier, that change complicates user code - see the examples I
gave. The test for a keyboard-only modifier (shift, control, meta, alt, hyper,
or super) has become downright silly - but perhaps there is a better way to do
it than what I posted?


[OT - BTW, do others find the Emacs bug-maintenance site usable? I found no
field for entering a bug number (e.g. 687), to show a specific bug, so I
searched the page for it. Not finding it, I tried to show the Archived bugs
(there is a field for that, at least). More than 50 minutes later (!), with
still no page displayed, I gave up, just clicked some other bug link, and
changed the bug number in the resulting URL. I can't believe this is the best
bug-maintenance tool we could find, but so be it.]

Re: Why the `click' modifier for a mouse-wheel event?

[Jan D.]

> 
> [OT - BTW, do others find the Emacs bug-maintenance site usable? I found no
> field for entering a bug number (e.g. 687), to show a specific bug, so I
> searched the page for it. 

I go to http://emacsbugs.donarmstrong.com/ and there is a "Find bug by 
number:" there.  What is the problem?

	Jan D.

Emacs bug list [was: Why the `click' modifier for a mouse-wheel event?]

[Drew Adams]

> > [OT - BTW, do others find the Emacs bug-maintenance site 
> > usable? I found no field for entering a bug number (e.g. 687),
> > to show a specific bug, so I searched the page for it. 
> 
> I go to http://emacsbugs.donarmstrong.com/ and there is a 
> "Find bug by number:" there.  What is the problem?

Thanks. I've been going to this URL that I bookmarked long ago:
http://emacsbugs.donarmstrong.com/cgi-bin/pkgreport.cgi?pkg=emacs
Guess I picked that up from some correspondence. That page is similar to the URL
linked from the page you cite with the link "main list of bugs".

There you will see what I reported. I will use the URL you sent to get to a
specific bug (or, as I did, click some other bug link and then change the bug #
in the URL). Thx.

(That doesn't change the rest of what I said, however.)