The Mac G4 Laptop Lab (TH 604): Guidance and Troubleshooting

Guidance: Shifting between Mirroring and Split Screen Modes
Computer Screen Doesn't Show Cursor

When a laptop is connected to a computer projector or other display device, Mac OS X allows the user either to

  1. display the same screen on both displays (mirroring), or
  2. split the screen between between the two displays (screen splitting).

Sometimes a CartMac user will shift from mirroring mode to split screen mode and leave it that way with the projector turned off. Symptoms might include:

These symptoms can disconcert the next user, who might not realize that the screen is in split mode and can't find the cursor (because it resides on the (possibly now-dark) projected screen rather than the laptop display. (See below for instructions for restoring normal mirroring mode.)

To understanding how to resolve this dilemma, it helps first to understand how to shift from the normal mirroring mode into split screen mode.

Toggling from mirroring mode to split screen mode:

First, the easy way. There should be a "display" icon somewhere along the right side of the CartMac's toolbar along the top edge of the laptop display. If it's there, click on it to get a menu and select "Turn on mirroring". That should do the trick.(You can than select "Turn off mirroring" to toggle back to split screen mode.)

Second, the hard way, which you must do if there is no display icon in the CartMac's toolbar:

  1. Open System Preferences (pull down the Apple menu [upper-left corner of the screen] and select "System Preferences").

  2. Select "Displays". This produces two dialog boxes, one entitled "Color LCD" and beneath it another entitled "Epson PJ" (referring to the second display device, the Epson projector) or whatever your projector is.

  3. On the Epson PJ dialog box, click on the "Arrangement" button near the top of the box. This should produce a cartoon representation of two screen displays, one on top of the other.

  4. Uncheck the "Mirror displays" checkbox in the lower left-hand corner. The screen should flicker blue-blank and then generate two separate screens, one on the laptop and the other projected. Note the following:

    1. The cursor resides on the projected screen, along with the dock and the Epson PJ dialog box. The Epson PJ dialog box shows a cartoon representation of two screen displays side by side. (Its "Mirror displays" check button (lower left-hand cornder) is unchecked.)

    2. The CartMac hard drive icon and screen-top menu bar reside on the laptop screen. So does the Color LCD dialog box.

  5. You can slide the cursor leftward from the projected screen onto the laptop screen and back again. Applications started from the dock (on the projected screen) will open on the laptop screen, but you can drag the open windows rightward onto the projected screen and back again.

In split-screen mode, the computer behaves as follows:

Shifting from split-screen mode to mirroring (normal) mode:

To return to the normal, mirroring mode:

  1. If the projector is not hooked up to the CartMac and/or not turned on, hook it up and/or turn it on, so you can see the projected screen.

  2. Locate the cursor (which probably resides on the projected screen. Also locate the Epson PJ dialog box (which also probably resides on the projected screen).

    If you can't locate the Epson PJ dialog box, slide the cursor leftward onto the laptop screen, pull down the Apple menu, select "System Preferences", and select "Displays". The Epson PJ dialog box should appear on one of the two screens.

  3. Click on the "Mirror displays" check button on the lower-left corner of the Epson PJ dialog box. (This should produce the transient blue-blank flicker, the Epson PJ dialog box will appear on top of the Color LCD dialog box, the projected screen will show the same thing as the laptop screen.)

    If you see no "Mirror displays" check button, then click on the "Arrangement" button nera the top of the Epson PJ dialog box. You should then see the button.

  4. The laptop screen is probably shrunken laterally and is flanked by black bars. To return the laptop screen to normal resulution, refer again to the Epson PJ dialog box. Click on the "Display" button near the top of the box, then select "1280x1014" from the "Resolutions" menu.

  5. Quit Systems Preferences.

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Page last modified 9/14/06 by Dave Dempsey.