Comment 22 for bug 1368402

(In reply to boennhoff from comment #2)
> Another way could be fiddling around with xinput (i assume
> gnome-settings-daemon is doing exactly that in the background), but i was
> too lazy to adapt that to my case...

I would not assume that, reverse scrolling is done at the device level, it makes no sense to me that gtk3 apps behave any differently than the others (and actually, xfce4-settings does the same as xinput).

So it needs a bit more investigation.