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

["Drew Adams" <drew.adams@oracle.com>]

> 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?