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Would like to disconnect my external monitor without unplugging the Mini DisplayPort Adapter. Any ideas? Running Mountain Lion, mid 2012 MacBook Pro.

The scenario:

I have another Windows machine connected to this external display via VGA. So when I switch to my Windows machine, I would like to use the MacBook Pro without extending to the external monitor. It's too much an hassle to keep plugging out the Mini DisplayPort Adapter every time I switch.

The Windows machine has VGA connected all the time, but it has an option to select a laptop display only mode without extending to the external monitor.

Thanks.

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Could you clarify what you mean by "disconnect"? Do you want your laptop to stop sending a signal to the external monitor? –  Bart Arondson Nov 21 '12 at 14:34
    
Yes. That's what I mean. Thanks! –  revolver Nov 21 '12 at 15:04
    
Ok, I see now in your edit that the display is connected to two machines. Could you post the product name of the display? Maybe it has some built in feature that decides if it gives priority to the thunderbolt input or the VGA input. –  Bart Arondson Nov 21 '12 at 15:20
    
Does it matter? I have the external display set as Primary Display on my Mac, the dock and menubar is on my external display. When I switch to VGA (I can control the input via the display menu), I don't see the menubar and dock on my laptop display. That's the reason I would like to disconnect the DisplayPort, so that I can have my MacBook Pro's LCD screen as primary display again. –  revolver Nov 21 '12 at 15:24
1  
It might matter, the more information you provide, the more likely it is that someone gives you an answer that will help you. –  Bart Arondson Nov 21 '12 at 17:01

5 Answers 5

switchresx (http://www.madrau.com/) will allow you to do this. You can set up a display profile with the external monitor disabled. Note that with Mavericks, this functionality can be a bit problematic depending on how Spaces is set up.

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  1. Does your shared monitor have a physical or electronic way to switch among input sources? I share a large monitor between a Mini with its own monitor and a MacBook Pro. Both machines stay connected to the shared monitor all the time. The shared monitor has a button to bring up its settings, so I can hit the button then move up or down to select which computer uses the shared display.
  2. Then when you switch the shared display away from your laptop, you need a way to see things the laptop had been showing on the shared monitor. I originally looked for a command or a script to make OS X "de-extend" the laptop's display, but didn't find anything. I finally settled on a little app called Moom, which deftly handles re-sizing windows and, importantly for this case, moving windows between displays. If I turn back to the laptop, and see that the window I want is being projected to the shared monitor (but not showing because the other computer is displaying), then I use a keyboard command to invoke Moom and then hit an arrow key to move the desired window into view on the laptop screen. (I first heard about Moom here at Ask Different; have had it for several months and am over my skepticism about needing a third-party utility for this use. The window-resizing is also very handy. I have no connection to them.)
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Sounds interesting. Thanks. Will give it a try later –  revolver Dec 28 '12 at 2:59

I will going to repeat daGUY's solution with extra explanation:

So if you're using your Mac with the external display, you're 'extending' your desktop. That means, those displays are presenting different content, and you may have dock and the menu bar on just one display.

That's say, you want to switch to your Windows machine, and you've switched your display's input to display Windows machine's desktop. Here's the problem, your dock is still on the external display!

Here's why DaGUY suggest you to use mirroring mode, mirroring mode make both displays present the exact same content, which means one dock but displaying at both displays.

Here's a few problem you may run into,

a) Resolution - You want your resolution to match your laptop screen's, and that might be an extra step, and sometimes might not work

b) SO MANY STEPS! - You got to go into System Preferences, click on Displays, and check that checkbox that reads "Mirror Display". Luckily, there's an app for that, here's the link: https://itunes.apple.com/tw/app/id549083868?mt=12

This app will put the option on the menu bar, and make it easier to change resolution, AND, it's free.

I'll upload photos soon.

Here's before mirroring: One dock on one of the displays

Here's after mirroring, and you can see I checked "Mirror Displays" in the menubar, that's the app I mentioned. You can do fine without it, just a few extra clicks:Same content on both displays

Please, do comment if you have further questions.

EDIT: Added photos

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There is a program that will allow you to switch the menu bar back to your MBP screen via the command line. It can be downloaded at: http://www.pyehouse.com/cscreen/ Since you are leaving the external monitor connected your MBP thinks it's still active and you will have to use cscreen to switch the menubar back to the MBP screen. Or manually do it via Display system preferences.

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How do I do it via Display System Preferences? I didn't see any option to disconnect the monitor. –  revolver Nov 22 '12 at 1:05
    
Oh I see what you mean. You mean changing the menubar back to MBP screen. But sorry. This is not the solution I am looking for. All my other application will still be on the external display. –  revolver Nov 22 '12 at 2:43
    
cscreen -p will swap all windows as well. I can't test it out until next week though. –  sbit Nov 22 '12 at 3:13
    
I see. That's interesting. Will give it a try later. Thanks! –  revolver Nov 22 '12 at 4:35
    
cscreen doesn't work for me :( –  revolver Nov 23 '12 at 3:21

Do you mean you want to leave the secondary monitor plugged into the computer, but not use it?

You can go to System Preferences > Displays > Arrangement and check the Mirror Displays checkbox. Make sure your primary display is set to the laptop's built-in display. Then just shut the secondary monitor off (so you don't see the mirrored display).

Now all your windows will be on the primary monitor and you won't be able to drag any to (or open any on) the secondary monitor, but it will still be plugged into the computer.

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Sorry, can't use your solution. See my updated question. –  revolver Nov 21 '12 at 15:15

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