I dont use windows, if you want a screenshot with fluxbox in linux you either use a commandline program and tell it which screen and window on which virtual desktop to grab, or use a graphics program like gimp to get one. I can bind a key like the print screen key to a program if I wanted to grab a screenshot but Id have to add a script to handle which desktop I was on and I have no clue how to handle the window selection.There's lots of options to choose with that, have to tell it which display too since im running two of them.