How to get out of fullscreen mode?
Pressing Keys F11 toggles Geany full screen mode.
Source: http://www.geany.org/manual/current/index.html#notebook-tab-keybindings
Ctrl+Shift+f worked for me.
This helped me on a guest Ubuntu running with VMware on a mac host.
I changed the line fullscreen=true in file ~/.config/geany/geany.conf to fullscreen=false.