Is it possible to "window" fullscreen games?

Is it possible to force an OpenGL app into a window instead of fullscreen canvas?

I'm using two displays and would like to use the other, while playing a game on one display. Since fullscreen makes the secondary display go black, this it not possible by now.


Solution 1:

I'm not sure if there is a generic way, but a lot of games give you the option if you hold down option when starting.