I am using more and more beamer this year. Since I used linux, I used to use evince to display my slides. But in my last class, I would like to write something on the slides and I was not prepared for that. My laptop is a nice good old X230t with a stylus on it. I can open xournal to write on the slides. But when I made it fullscreen, I could not get away with the toolbars previously.
It turns out to be very easy. Following this post, one can just modified interface_fullscreen and view_continuous in ~/.xournal/config as follows
interface_fullscreen=drawarea view_continuous=false
It will then hide the toolbars when switch to fullscreen (F11).
See the complete config file here