OS X Yosemite: Options pane of Displays preferences
If you connected one or more displays to your Mac, you can set what happens when you press the Power button on your display and the brightness buttons on your Mac in the Options pane of Displays preferences.
To open this pane, choose Apple menu > System Preferences, click Displays, then, in the Displays preferences window on the connected display, click Options.
| Display Power Button | Set behavior for when you press the power button on the connected display. |
| Brightness Buttons | Set behavior for when you press the brightness buttons on the keyboard of your Mac. |
| Gather Windows | Moves all open Displays preferences windows to the display showing this button. This button appears only if more than one display is connected to your Mac. |