Mac OS X Dual Monitors

You might think the picture above is showing a Windows PC sitting beside my Mac. Actually it's not: that other monitor is attached to the Mac and that's Parallels running Windows XP on the screen.

If you've never used dual monitors, you may not immediately see the advantages - after all, you can quickly Apple-TAB to any application or use Spaces to switch screens entirely. The dual monitor does offer more screen real estate, but is that really all that useful?

Yes, it is. Even Microsoft says so, and we know they are always right. No, really: it is useful. And it's even more useful on a Mac, though before I leave PC's out entirely, let me mention this interesting use of dual monitors. That uses a VNC product and Mac dual displays to bring up a PC screen on the extra monitor. That's conceptually similar to what I do for remote support: when I'm using VNC, Remote Desktop or even GoToMeeting or similar tools, putting that support session into the other monitor is very useful.

So how do you set up dual monitors on your Mac? Pretty simple: plug it in. On my MacBook Pro I have to use an adapter (make sure you bring that adapter when you take your Mac out for a ride: you never know when you'll need or want it) but it's really that easy.. well, not quite.

First, I'd suggest NOT having Parallels running when you hook up the second monitor. It's not going to break anything, but it can confuse things a bit, and this experience can be confusing enough at first anyway. I'd also recommend disabling Spaces if you have it enabled; again, there's nothing wrong with Spaces, and it works perfectly with dual monitors - I love Spaces with dual monitors! - but it can be more confusing at first. Baby steps first, and once you feel comfy, you can turn Spaces back on.

You'll want to open Displays in Preferences and tell it to "Detect Displays". Unless there's something very strange about your monitor, that's all you need to do: a desktop and a Display Preferences window should pop up on the new monitor. If it does not, click "Gather Windows" to bring that Preference dialog back onto your main screen - it will probably be slightly behind your main monitor's preferences, but it should be there. Adjust resolution, colors and Refresh Rate if necessary. You'll notice a "Rotate" button also - I'd stay away from that just now too unless you have put your monitor on its side or upside down.

Back on your main display's Preferences you'll see "Arrangement". It makes sense to arrange the screens to match their physical location. Your Mac doesn't know where the cable goes, so you need to drag the screens so that they make sense - because it is moving your mouse off your main screen that lets the cursor get to the second monitor. If the Mac thinks the other screen is to the right, you need to move the mouse to the right.. and just keep going at the edge of the screen and your cursor suddenly will appear on the other monitor. Neat, right?

But where is the menu bar? Hey, somebody forgot something, because the Dock and the Menu Bar stayed on the main screen! Yes, that is the way it works, and at first I thought that was really annoying, but it only took me a few minutes to get used to that and now it just seems natural. However, if you can't acclimate, take a look at DejaMenu, a utility made just for this problem.

If you feel comfortable, turn Spaces back on (and start up Parallels too). Spaces is really neat with dual monitors because the new monitor space is just part of the Spaces real estate: so when you switch to a different Space, your other monitor switches to whatever it displays in that Space. Confused? Play with it and you'll see what I mean.

If your monitors don't use the same resolution you will find that Spaces will annoyingly resize things - I don't know any way around that other than matching resolutions. But even at that, dual monitors are still great to have.

One more thing to watch out for: if you've left something in the other monitor and disconnected it, it can be impossible to get to that app's window until you click "Detect Displays" again. That's all you need to do: everything will return to the main display immediately.

Comments /MacOSX/dual_monitors.html


Sat May 10 18:42:00 2008: Subject: Wake MBP   Rodion


I use 22" acer monitor connected to my MBP with MacOS X Leopard to show cartoons to my daughter while working. And I noticed a strange way MacOS X acts with two monitors. If I close my MBP with another monitor still connected and then move or cleck my mouse, which I use with my MBP - all the stuff that has been being displayed on the screen of the MBP moves to Acer monitor (including Dock and top Menu bar). But when I open my MBP again, there is no way to wake up its display but disconnect external monitor.
Is there any way to fix that problem?

Sun May 11 22:15:42 2008: Subject:   anonymous


"Detect Displays" doesn't work?

Sun May 25 07:44:51 2008: Subject:   anonymous


That's not a bug. it's a feature :-)
What you are describing is the established process for how you initiate using just the monitor w/o activating the laptops screen. Having an extermal monitor and key board attahced to a sleeping mac will wake it up and just activate the monitor. You'll need to unplug the monitor and keyboard to get the laptop screen to reactivate. You don't need to put it to sleep again to do that.



Tue Jun 10 08:28:56 2008: Subject:   Rodion


It might have been a feature if it didn't have me to unconnect external monitor to return the work area back to MBP display. However, if I cannot switch back to MBP screen fast pushing some shortkey and have to unplug my external monitor, it's a bug :(

Btw, I haven't yet checked out if the situation remains the same in Mac OS X 10.5.3 (the last update), they might have fixed it already.

Wed Jun 25 19:49:51 2008: Subject:   anonymous


to come back to work on the main screen you don't need to unconnect the external monitor, just use detect monitor while MBP lid is open. It should switch immediately.

Fri Jul 18 15:34:58 2008: Subject: how to move dock to secondary?   georgeBroyles


Do you know how to get the dock and menu bar to switch to the secondary monitor whenever it is connected? Since my secondary display is bigger/nicer, I work mostly from it and would like the dock and menu bar to be there.
I had this set up on my MBP at work, but I no longer work there and can't ask the support guy how he did it.

Fri Jul 18 15:50:38 2008: Subject:   anonymous


Isn't it just In your Displays pref, drag the menu bar to the external monitor??

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