Comment 119 for bug 1228250

(In reply to Masayuki Nakano [:masayuki] (JST, +0900) from comment #112)
> (In reply to Olli Pettay [:smaug] from comment #111)
> > (In reply to Masayuki Nakano [:masayuki] (JST, +0900) from comment #108)
> >
> > > On macOS, we may receive diagonal wheel operation events. In such case, we
> > > should not respect the new pref because the new pref is for legacy mouse
> > > device
> > How so? Isn't it for touchpads too.
>
> Oh, really? I remembered as so. Just my memory is wrong or macOS's behavior
> has been changed (IIRC, starting Sierra, mouse scroll event behavior has
> been changed, it might be changed at this time).
Sorry, I was unclear. I was talking about touchpads on Windows.
I have no idea about MacOS

> I'm not sure about GTK. GTK3's event has both delta values in an event. So,
> it could support diagonal scroll, but I don't have environment that Linux is
> installed on real machine (not virtual machine).
I see, on linux Chrome has odd behavior where it seems to allow vertical scrolling when diagonal scrolling is done. That behavior is really weird when one uses it. Makes scrolling feel like all broken since viewport is scrolled somewhat randomly. It is hard to control whether to do only up-down or left-right scrolling on a touchpad or a bit both.

> Anyway, I don't think that we should use this feature when the user's device
> is obviously non-legacy pointing device, i.e., it supports diagonal scroll.
> What do you think?
But this is enabled on touchpads too, if the pref is set. Could we somehow enable it on mouse input only, and not touchpad?