set_fullscreen
Description:
Sets the ApplicationWindow into either the fullscreen or unfullscreen
state based on fullscreen.
The titlebar for the window is contained within a Revealer which is repurposed as a floating bar when the application is in fullscreen mode.
See get_fullscreen to get the current fullscreen state.
Parameters:
| this | |
| fullscreen |
if the window should be in the fullscreen state |