Attached is a patch which enables game mode via a window initarg "game-mode". The enter-game-mode and leave-game-mode calls must be used instead of create-window and destroy-window, hence the somewhat invasive coding. I'm not sure if this is the right approach, another possibility would be to make a sibling class of "window", "game-mode-window"?
I also made the display-window :around method for windows set init-window position and size, so that the window isn't created one place then immediately modifed. But the base-window's display-window :around still calls position/reshape window. Apologies, this is sloppy, but I didn't want to muck with part of the code with which I wasn't at all familiar.
Hope any of this is of use in some form?
Thank you,
Dan