Bug#645416: Tracked this down: independent Num Lock settings on ThinkPads

[Josh Triplett]

I finally managed to track down this problem.  ThinkPad laptops have a
BIOS setting to make Num Lock independent for the internal keyboard and
any external keyboard.  This setting allows enabling Num Lock on an
external keyboard with a real numpad, while leaving it disabled on the
internal keyboard where the "numpad" just remaps existing keys and
prevents normal typing.

With this setting enabled, a ThinkPad has two independent numlock
settings.  When I plugged in an external keyboard, I found that it had
Num Lock enabled.  (I noticed rather quickly, because I used an external
ThinkPad keyboard, with the same numpad overlay that prevents normal
typing.)  Once I turned off the external Num Lock, gnome-screensaver
stopped warning about enabled Num Lock.

Having the external Num Lock enabled causes gnome-screensaver to warn
about Num Lock, even with no external keyboard attached.

I don't know the ideal fix for this problem.  In an ideal world,
gnome-screensaver could know whether any particular keyboard has an
overlay numpad or similar that would break typing a password with Num
Lock on, and would warn iff the user has Num Lock enabled on such a
keyboard and tries to type their password.  However, I seriously doubt
that such a keyboard database exists.  In the absence of that, it would
at least help to note *which* Num Lock the user has enabled when warning
about it.

I'll report this upstream and try to get a conversation going.

- Josh Triplett