Comment 99 for bug 1228250

(In reply to Olli Pettay [:smaug] from comment #85)
> (In reply to Masayuki Nakano (:masayuki) (Mozilla Japan) from comment #82)
> > > That sounds like a minor problem that could be fixed in this bug or a
> > > follow-up.
> >
> > I think that we should decide it in this bug. Smaug, how do you think? I
> > believe that if we'd swap deltaX/deltaY for default action, DOM wheel event
> > and legacy mouse scroll events should represent it. However, if we do so in
> > default settings, there is an issue mentioned in #4 (below).
>
> Doesn't sound like a minor problem.
> Since widgets on web pages tend to emulate native scrollable areas, they
> should get events similar to
> native viewport or other scrollable areas.
>
> #4 is tricky, but I think we should favor the more common case, so swap.
> How does IE handle this? What does Chrome actually report in delta values?

Looks like that IE/Edge doesn't have this feature since Shift+wheel causes navigating history like us. Chrome just swaps default action (i.e., not touching DOM event values).

I wonder, wheel related events are cancelable, that means that it does NOT represent default action's behavior. So, perhaps, we can just take the Chrome's behavior? (Even if web apps check their implementation only with Chrome, it won't cause any problem only on Firefox.) That's not ideal behavior from a point of view of DOM events, but low risk approach in the real world.

FYI: At bug 1358017 Comment 2, similar issue on vertical writing web pages, dbaron thinks that only changing default action is reasonable.

How about you?