Hello. While trying to fix what I thought was an application program window placement problem, it turns out that the problem was that Gnome 3 seems to be detecting a display which does not seem to exist. Clicking the Gnome "Settings" icon, then the "Displays" icon seems to show both a primary and a secondary display. But there is only one monitor and one graphics card! The primary display is correct: 1366 x 768 resolution, 16 x 9 aspect ratio. But even thought there is no second monitor or graphics card, "Displays" shows a secondary display as: 848 x 480 resolution, 16 x 9 aspect ratio. So, how can I delete the non-existent secondary display. (In the good old days, "Displays" included a button to detect displays. Not now). 1) Wild guess: 848 x 480 seems like some sort of phone or tablet display, but 16 x 9 wouldn't seem to be a phone display. 2) A non-existent display - I worry: have I been hacked? This is on an unmodified, standard, name-brand computer running up-to-date Arch 64-bit.