when you don't want it to; like in the middle of a movie.
Mouse Mover: Go to Menu --> Sound & Video --> Mouse Mover before watching a video. This should prevent the screen from blanking. If you can watch a video for over 10 minutes without the screen going black, full-length movie watching will be fine.If the screen still blanks; you'll need to deactivate screen locking altogether.
4. Delete lxlock and "X" out of LXSession configuration
Click the Security tab, uncheck Lock screen when system
is going to sleep and click the "X