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Level 1

4 points

Screen detection in clamshell mode problems

I have a weird issue with clamshell mode in Lion 10.7.2

Hardware: MacBook Air 13" i5 1.7, Apple Cinema Display 30" connected with Apple Mini DisplayPort to Dual-Link DVI adapter.

Normally I use the computer in clamshell mode, with the laptop lid closed. It only sees the main 30" display, which is the desired behaviour—all good so far.

When I put the computer to sleep, then wake it up, it suddenly sees two displays—despite the lid being closed all along.

The laptop screen is on (even though it is closed). I open the lid, then close it—the screen backlight gets switched off but the laptop LCD is still active in OS settings, I can move mouse cursor and windows to it and so on.

There is no way to get rid of laptop display unless I restart the computer—then it only sees the active 30" screen again.

In the end, I have to restart the computer every time I wake it up.

Did anyone experience something like that? Any ideas what is going on? Thanks.

MacBook Air, Mac OS X (10.7.2), ACD 30"

Posted on Oct 25, 2011 3:04 PM

34 replies

Apr 10, 2012 10:33 AM in response to raftr

WORKAROUND: I too have this same issue and discovered a workaround. Basically, I connected the CinemaDisplay after my MacBook Air 2011 i7 has been on and working for several days, and as usual the external CinemaDisplay turned on and activated as a secondary monitor (not mirrored). I then entered System Preferences, chose 'Displays,' chose 'Arrangement,' and then dragged the white bar at the top of the MacBook Air display repsentation to the representation of the CinemeDisplay. The CinemaDisplay became the primary monitor. I then closed my MacBook Air and the light went out. Thus far, this appears to have 'stuck,' as I can close my MacBook Air and the external monitor switches, becoming the primary display. I'm not certain if this will remain the case after a reboot. I admit that I've only been experiementing with this solution for the past hour, but it appears to work repeatedly.

I was inspired by the following article which illustrates what I am doing, although for a different purpose:

http://osxdaily.com/2010/04/27/set-the-primary-display-mac/

Good luck and I hope it works for everyone else!

Apr 10, 2012 11:24 AM in response to gregarious64

I will add that even though the display light has turned off on my MacBook Air since writing the workaround post, it doesn't mean that the Air's display isn't recognized. I can still move my cursor off screen.

If anyone was wondering the iSight camera still works on the CinemaDisplay.

raftr Author

Level 1

4 points

Apr 10, 2012 11:52 AM in response to gregarious64

gregarious64 wrote:

I will add that even though the display light has turned off on my MacBook Air since writing the workaround post, it doesn't mean that the Air's display isn't recognized. I can still move my cursor off screen.

Yes, this is the problem this thread describes. When the lid is closed, ony the external display should be active and the cursor bound by its edges. Strangely, not everyone with an external display has it so it is hard to tell how widespread it is.

It is fixed in Mountain Lion.

Apr 10, 2012 7:27 PM in response to raftr

I have this problem as well. I have been using clamshell mode since the first day of getting my macbook pro 13". Yet I only realized this problem when i started to wonder why the scrolling of long documents or webpage was always 'sluggish' after waking up from sleep. It led me to check the system setting and there were two screen appearing under the arrangement tab!

I have been thinking how to roll back the update and even preparing to restore to backup using Time Machine, but still not sure whether it works. Apple please fix this irritating problem on the next update. I don't want upgrade it to ML just to get this thing fixed.

Screen detection in clamshell mode problems