GTK3-apps: Scrollbar jumps to the bottom after scrolling with mouse wheel when regaining focus

[Nils Dallmeyer <danils@gmx.net>]

Hello,

I run a GTK3-app with scrollbars (for example evince with a big PDF
file opened) and the vertical scrollbar is positioned somewhere above
the bottom. I use XFCE and if I move the cursor to the taskbar and back
again to evince and then I scroll a little bit up or down, the
scrollbar jumps to the bottom (thus evince jumps to the last page).
This is only one example, it seems that the loss of focus is enough to
cause this bug in any GTK3-app with scrollbars.

GTK2-apps and QT-4/5-apps don't make any trouble, therefore I guess it
has something to do with GTK3 and/or XFCE but I am not able to find out
which package is affected. I currently use the Testing Distribution
(Debian 4.0.8-1 (2015-07-11) x86_64 GNU/Linux). The bug occured the
first time before a few days.

Best regards,
Nils Dallmeyer