I'm not sure whether I've discovered a feature or a bug of LibreOffice Writer v. 188.8.131.52 in Gnome 3.4 on Ubuntu 12.04. Either way, I can't figure out how to get things back to how they normally are.
I accidentally engaged Writer's full screen function by pressing Ctrl+Shift+J on my keyboard. When I had Writer come back out of full screen mode, though, it lacked a window border. That is, it still has a menu bar and tool bars, but is otherwise stuck at full-screen without a close button or title bar.
I am unable to move the window using the top area of the window or Alt+Click. Writer is not frozen. However, I can toggle this new window mode back and forth from the actual full-screen mode (which lacks toolbars or a top menu), and can close the window using Alt+F4.
Other LibreOffice programs do not show this window mode when I open them. When I close Writer and then open other files with it, though, the files all show up in this semi-full-screen mode.
Since it appears to be isolated to Writer, I assume that this is a feature rather than a bug.
Might any of you know how to turn it off?