Hmm… Some further testing has revealed some points that are interesting, but a little odd:
I commented out the calls to “setButton -Down/-Up -Event” that act on the “keyboard-and-mouse” button-thrower–that is, the two calls above the for-loop. In this case, I (understandably) don’t get any mouse-events–except for those first two.
But conversely, I printed out the device-class associated with the devices that appear in that for-loop, and the mouse doesn’t seem to be there.
However! In further investigating, I think that I’ve found the source of the events: my Bamboo drawing tablet (which I generally leave plugged in). If I unplug that, I get no phantom mouse-events. A quick test with my gamepad plugged in but the tablet disconnected again produced no phantom mouse-events, indicating that the problem is related to the drawing-tablet.
Note that during these tests, the tablet was lying by my side, its pen on the table; I wasn’t using it, so I would expect no events from it.
I note that when printing out the name and device-type of the tablet, while the name looks fine, its device-type is given as “unknown”.
Perhaps that’s the problem, then? That a thrower associated with the “unknown” device-type automatically picks up mouse events for some reason?