Getting rid of a ghost display

Today I hooked my MacBook Pro up to an external monitor for the first time. I used it in “clam mode”, and used an external keyboard and mouse with it. No problems with that. Except when I unplugged it. Because when the monitor was unplugged, I had no dock, and no file menu on my display (the MacBook display, that is). So I plugged it in once more, and everything was fine on the external monitor and the Mac display. But once disconnected, the display again showed just my wallpaper. So a series of creative disconnect procedures followed with no luck.

But I did notice something strange: My Mac was convinced it had a third monitor connected. Huh.. And when I disconnected my Mac from the external monitor, this non existing display was set to being the primary display.

Display options Mac OS X
My display with the mysterious ghost display

So I finally figured out how to change the primary display to being my Mac display. Really simple when you know how: Just drag the white field that represent the primary screen over to the screen you want to be primary. But what was this “ghost” display?

Then I remembered, that some months ago, I installed iDisplay on my Mac. Could this have something to with it? iDisplay lets you use your iPad as a external monitor with your Mac. Sounded like a useful thing to have, I thought at the time, and downloaded the app to the iPad, and the required software to the Mac. But it didn’t win me over, since it was very slow at responding (it uses wi-fi), and I didn’t really see the use of a very small external screen, after all. But the software was still on my system (you know, just in case). So I uninstalled it. But the “ghost” display was still there.

Then I did some more googling. And found that to be able to uninstall iDisplay completely, you actually have to download and run a script the producers have posted on their website. So I did that. And the “ghost” display was gone, and all was good.

Uninstall iDisplay promt box
Hell, yeah!

So in the end: I discovered that connecting a Mac to a display is very seamless. I learned how to change primary display, and I realized iDisplay can be quite shit. To quote Engadget: We have just looked evil in the face. Its name is iDisplay. Always good to learn something new on a Sunday.