Reducing screen size of the 27" iMac

[andersjm]

Hi,

Im thinking about buying the high-end 27" iMac i7+2gb 6970 gfx.
In my spare time i want to play world of warcraft, starcraft II and possibly Diablo III. What worries me, however, is if the 27" screen is too big for gaming, i.e i don't want to a tennis-match experience having to turn my head all the time.
So i'm wondering if it is possible to reduce the active screen size to like 21" inch when gaming?
Just to be clear, im not talking about playing in nonnative resolution at 27".

Thank you

 

[TMRaven]

Some games do have the option of playing at a smaller display resolution but still keeping native pixel resolution. There's always the option of playing in windows mode as well.

 

[andersjm]

Thanks for your reply. I'm not sure about windowed mode, as i think accidentally clicking outside the windowed game could be annoying (i.e. suddenly the game won't register keyboard clicks.
Do you know if the games i mentioned have the option of playing at reduced size?