Mail, stay! Stay! Bad dog!

April 30, 2008 7:02 AM

How do I limit an application to one screen of a dual-screen setup in Mac OS X (Leopard)?

A coworker recently switched from a desktop to a laptop at work, and I'm in charge of helping her work the kinks out and otherwise keep the migration as painless as possible.

She is using a Powerbook G4 connected to an Apple Display, and for all intents and purposes, she only uses the monitor at work. Normally, mirroring displays would solve the problem, but the laptop is a wide-screen computer, so mirrored displays leads to a letterbox effect on the computer.

The issue: Apple Mail seems to want to open new windows on the second (laptop) window, and we cannot figure out how to fix this behavior. Even if we drag the windows over, the next one opened will be back on the secondary monitor. As long as the external display is plugged into the laptop, the dock and menu bar are on the external display, so I am assuming OS X thinks of it as the primary display.

So I guess the crux of it is, how do I force applications to open new windows only in one display or the other?

posted by explosion to computers & internet (7 comments total)

Sounds like you just need to tell Mac OS X which screen is the primary screen. You can do this in System Preferences > Display. In the Arrangement tab of the Display prefs, you can drag your screens around to arrange them, but you can also assign one screen to be the primary screen.

If you look, you'll notice a little (representation of the) menu bar on one of the screens in the Arrangement tab. You can drag that menu bar around to the other screens. Whichever screen you drag the little menu bar to, that becomes the main display.
posted by Mikey-San at 7:15 AM on April 30, 2008

I wish that was the answer. We've already done that, and the monitor (Apple Display) is set as the primary screen. The menu bar has been dragged over.

Right now, with the monitor plugged in, the laptop screen shows nothing at all except for the background image. Unfortunately, when a new email is opened in Mail, the window opens on the laptop screen.

If there's a way to turn off the laptop screen while the Display is attached, that might be a solution to this problem here, but I'd also like to generically know how to wrangle application windows in case I am setting up someone later who wants to use both screens.
posted by explosion at 7:22 AM on April 30, 2008

Close Powerbook. Plug in external display. Laptop should wake up, and the external should be the only display.

(I'm assuming you have an external keyboard and mouse as well, of course.)
posted by Tomorrowful at 7:37 AM on April 30, 2008

Mail (and I believe most other apps) will open new windows in the same monitor that a window from that app was last closed in.

So: open new mail message (in the wrong display). Drag that window to the right display. Close that mail message window. Open a new one, and it should appear on the correct display.
posted by ook at 9:07 AM on April 30, 2008

Yeah, I just tested; safari, terminal, firefox, photoshop behave the same way; the only one I checked that does not is BBEdit (which always opens new windows in the primary display).
posted by ook at 9:20 AM on April 30, 2008

Normally, mirroring displays would solve the problem, but the laptop is a wide-screen computer, so mirrored displays leads to a letterbox effect on the computer.

Keep mirroring on. Pick a resolution through System Preferences > Display that doesn't show the letterbox effect on the external monitor.
posted by Izner Myletze at 9:33 AM on April 30, 2008

I have a similar setup, and have no need for the laptop screen.
What I do:
1. Start with computer and monitor OFF
2. Turn on computer, close it so it goes to sleep.
3. Turn on monitor. This will wake the computer up.

You can now work with a closed laptop and everything on the external monitor. There must be a saner way to do it, I jus stumbled into this method.
posted by Dr. Curare at 1:35 AM on May 1, 2008