Clamshell mode problem: laptop screen still active

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Hi folks

I have a somewhat unusual problem. When running my Mac Air in clamshell mode, it still thinks its own screen is active. The laptop's screen is turned off, but when I move my mouse around the external monitor, it can drift off into the (closed, dark) monitor of the laptop itself. When I open Displays in the System preferences, it clearly thinks both screens are active.

Has anyone else run into this? Any suggestions on handling it?

Thanks in advance.
 

pigoo3

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Try rebooting the computer.

- Nick
 
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Try rebooting the computer.

- Nick

Thanks Nick, I should have said upfront that I have already tried rebooting, to no avail.

The problem appeared quite recently, so I wonder if there's an obscure setting somewhere that's somehow breaking this -- but I can't figure out what it would be.
 

pigoo3

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Thanks Nick, I should have said upfront that I have already tried rebooting, to no avail.

When you rebooted…was the MacBook Air's display closed & the external monitor connected?

- Nick
 
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Stupid question...
You are in mirrored mode right?
 
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Stupid question...
You are in mirrored mode right?

Not a stupid question! I'm not in mirrored mode, and I'm aware that I could use that to fix this -- but I often unplug my Mac from my desk and plug it into an external projector, at which point I don't want mirroring. Until now, I've never used mirrored mode, and this problem didn't happen... so I was hoping to find another solution.

(You'd imagine the system would be clever enough to *not* detect the laptop's screen when it's in clamshell mode... it certainly used to manage this!)

But maybe ticking the 'mirror' option and just messing with system preferences every time I connect to and disconnect from a projector is the easiest way to fix this.
 

pigoo3

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I'm not in mirrored mode, and I'm aware that I could use that to fix this --

Give it a try. The goal at the moment is to find a solution to the current problem.:) Let's worry about what happens later…later.:)

(You'd imagine the system would be clever enough to *not* detect the laptop's screen when it's in clamshell mode... it certainly used to manage this!)

It usually is/does!:)

- Nick
 
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Give it a try. The goal at the moment is to find a solution to the current problem.:) Let's worry about what happens later…later.:)

Good point, well made. :)

And usually.when someone connects to an external projector.you want to be in "mirror-mode".since you want the external project or to mirror what's on the computer display.:)

Yeah, I prefer to work without mirroring, but it's not a wildly big deal to mess with system settings each time I connect to / disconnect from a projector. And this does solve the problem!

It usually is/does!:)

- Nick

Gotta love technology, eh ;)

My thanks to both of you for your suggestions and help with this issue. As a forum n00b, I very much appreciate the rapid and helpful responses :)
 

pigoo3

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Gotta love technology, eh ;)

My thanks to both of you for your suggestions and help with this issue. As a forum n00b, I very much appreciate the rapid and helpful responses :)

Please let its know if changing to mirror mode setting helps. I run my 17" MacBook Pro in both extended desktop mode and clamshell mode (alternate between the two) all the time (almost never just use the MBP's built-in display only). And as far as I know…have not run into this trouble.

- Nick
 
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And I assume all the requirements and quirks have been double checked??
https://support.apple.com/en-ca/HT201834

Next, try a Safe Boot to possibly eliminate any non-Apple software that could be causing the problem.
 
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Please let its know if changing to mirror mode setting helps. I run my 17" MacBook Pro in both extended desktop mode and clamshell mode (alternate between the two) all the time (almost never just use the MBP's built-in display only). And as far as I know…have not run into this trouble.

- Nick

Yep, as expected mirror mode solves the problem. I've been running various Macs in extended desktop mode and clamshell for over a decade, and it's the first time I've run into this issue, too!

Thanks again.
 

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