Linux, especially Ubuntu, has quickly evolved, introducing core UI changes such as the global menu bar (akin to OS X’s single menubar system) as well as Overlay Scrollbars. Overlay Scrollbars were meant to reduce the amount of clutter needed around content areas by showing up only when hovered over, and always outside the content area. If you’re developing any kind of serious application on Linux, especially if you are targeting Ubuntu, you want to be able to detect whether or not the system supports Overlay Scrollbars.
