Can you inform us on what environment you are working on, I don’t think this is due to GLUT, as far as I know, there is not even a function that could make appear/disappear the window title bar.
Compiz is a window manager that uses hardware acceleration via opengl. It enables many effects like 3d desktop. You will find more information googling.
To disable/enable it graphically, install the compiz-swith package with synatic. Or try this in command line: