new gtk3 scrollbars

[Karl Anliot]

om 12.10 and later: the new gtk default scrollbars have a new
feature/setting.  It's all about what happens when you click on a
scrollbar.  If you click near the top of a vertical scrollbar, do you
expect to be taken near the top, or 1 page up?  This is a click below
or above the scrollbar button, but on the scrollbar.

They randomly changed the effect, without documenting the workaround.
But I have:
~/.config/gtk-3.0$ cat settings.ini
[Settings]
gtk-primary-button-warps-slider = 0