For whatever reason, the touchpad right edge would no longer allow me to do scrolling (like the usual middle wheel on the mouse) under the gnome flashback session in Debian testing.
Here's a way to make it work : http://askubuntu.com/questions/248290/enable-both-edge-scrolling-and-two-finger-scrolling-for-touchpad/373134#373134 .
This post provides a more elaborate script : http://who-t.blogspot.fr/2011/03/custom-input-device-configuration-in.html reusing an example script (in Debian, in
/usr/share/doc/gnome-settings-daemon/examples/input-device-example.sh), but attention: it may be invoked twice, if like on my system, once for an "AlpsPS/2 ALPS GlidePoint" and then for a "PS/2 Mouse", but resetting the VertEdgeScroll to 0 in between.
So the script looks like that on my system, now :
... if [ "$device" = "AlpsPS/2 ALPS GlidePoint" -o "$device" = "PS/2 Mouse" ]; then synclient VertEdgeScroll=1 fi
I guess there's some kind of a bug here... but the gnome session is a hell when needing to spot the culprit package to report to, so for once, I'll let reportbug quiet.
Hope this helps
Update: this unfortunately doesn't seem to work on initial session start :-/