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After many many hours of restarting X, we've found that, in order to get all seven of the buttons to be visible to X, you need to define the mouse as follows:
Section "InputDevice" Identifier "Mouse0" Driver "mouse" Option "Protocol" "ExplorerPS/2" Option "Device" "/dev/mouse" Option "Buttons" "7" Option "ZAxisMapping" "6 7" EndSection
That block goes in XF86Config which might be in /etc/X11 or /etc and
might also be called XF86Config-4.
Please note that this is for XFree86 Version 4, not 3.3.x!!!
If left as-is, your scrolling will occur with the "side buttons"
and NOT with the wheel, so one has to
xmodmap -e "pointer = 1 2 3 6 7 4 5"
to get the wheel working correctly. I have this in a shell script that GNOME executes on startup. I've tried ~/.Xdefaults ~/.xdefaults ~/.Xmodmap ~/.xmodmap ~/.xinitrc ~/.xsession and a couple of things in /etc/X11/ and none of them work. However, I've received a ton of email saying that other people have had luck with some of these, so give it a shot. But please don't email me with what you find, because I don't care.
If you set ZAxisMapping to "4 5" the mousewheel will work, but X won't see the other buttons. (xev)
Once you have this configured, you may wish to head over to Colas Nahaboo X mouse wheel scroll page. He has a lot of good information on how to get various applications working with the mouse-wheel.
So dude steals my content and gives me no credit, but he provides some potentially useful info, so he gets a link.
Send comments to Sam Rowe, deadman at deadman dot org.