OK. so this is strange.
I recently bought a HP Pavilion ab153nr laptop and installed Mate 15.04 on it. While setting everything up, I noticed that the screensaver would occasionally stop showing (ie, go back to the desktop) without me touching the computer, but I didn’t worry about it. When I started using the computer, however, I noticed some additional strange behavior. Scrolling in my browser would sometimes cause the page to zoom in or out, and while typing in my IDE I would get apparently random commands.
Running xev shows that something is sending Alt_L, Control_L and Shift_R events. I ran xev overnight, and it counted 5 Shift_R KeyRelease events, 15 Alt_L events, and 25 Control_L events. Interestingly, there are no KeyPress events, though there are FocusOut, FocusIn, and KeymapNotify events. I don’t know enough to know if those are relevant, however.
It’s not related to my KVM switch (symptoms persisted when I disconnected it) or the laptop hardware (booting into the Windows 10 partition and leaving either the screen saver or the on-screen keyboard up for hours showed no unexpected behavior.)
Anyone have any ideas about what could be causing this? A way to better identify what process is sending these events? The laptop is supposed to be my development machine, but it’s pretty much unusable with random control characters being sent every 10 minutes or so. I’ve put the log at http://pastebin.com/3inwfuxG if anyone wants to take a look; everything after the Scroll_Lock presses until the mouse movements at the end of the file is from when the box was left idle over night.