Code review comment for lp:~vanvugt/unity/regionalDamage

Tip on detecting if the shell is hidden (I did this once myself).

It might make more sense to use core's built in occlusion detection to figure this out. I think in that case when you get a redraw on a nux window, region will be empty in glPaint. That's worth double checking. (Also worth noting is that this only works if you disable removing the nux windows from the paint list, which should hopefully be done in the future)