I wanted to try out the game Glest on my machine and ran into some odd things.
1. Running with two displays, the game spans over both displays with the menu being split right down the middle. I'm guessing this is due to the xrandr 1.1 compatibility of the Catalyst 9.1 (fglrx 9.1) drivers.
2. Switching the displays into clone mode prior to bringing up game and then trying to start it, causes the game to crash on start.
[kdekorte@quad ~]$ glest
X Error of failed request: BadValue (integer parameter out of range for operation)
Major opcode of failed request: 135 (XFree86-VidModeExtension)
Minor opcode of failed request: 10 (XF86VidModeSwitchToMode)
Value in failed request: 0x5b
So I guess I am kinda out of luck trying out the game. I might try and play it in dual head and see if I can move some of the in game menus around. But for games, I really wish they would stick to one display unless told otherwise.