Weird behaviour of gdk_device_get_history

[Rafael Cunha de Almeida <rafael kontesti me>]

I'm using gdk_device_get_history and I have been hitting some weird
behavior.  Sometimes get_history returns coords at <0, 0>, but the mouse
(the device I'm using) never goes there. I notice that if I add 1 to the
start time and subtract 1 from the end value, things seem to work. I'm a
bit puzzled. When is this behavior supposed to happen? devhelp doesn't
seem to say anything about it.