This is an old revision of the document!
by Richard Russell, November 2014
Suppose your program displays something which you would prefer the user not to be able to capture in a screenshot (e.g. using the Print Screen key). You can do that as follows:
WDA_MONITOR = 1 SYS "SetWindowDisplayAffinity", @hwnd%, WDA_MONITOR
Once this code has been executed, the specified window (here the main output window) will appear black in a screenshot.
Of course you can't stop the user taking a photograph of the screen, but the above code will go some way to discouraging the capture of your program's output