It is possible to take complete control of the mouse for your own application, preventing it being used to activate other applications. This is most useful for immersive games such as first-person shooters.
When you enable mouse-exclusive mode, the mouse cursor is no longer available. It is not merely hidden -- no amount of mouse movement will make it leave your application. Because there is no longer a mouse cursor, the x and y parameters of the mouse events are meaningless; you should use only the dx and dy parameters to determine how the mouse was moved.
Activate mouse exclusive mode with set_exclusive_mouse:
window = pyglet.window.Window() window.set_exclusive_mouse(True)
You should activate mouse exclusive mode even if your window is full-screen: it will prevent the window "hitting" the edges of the screen, and behave correctly in multi-monitor setups (a common problem with commercial full-screen games is that the mouse is only hidden, meaning it can accidentally travel onto the other monitor where applications are still visible).
Note that on Linux setting exclusive mouse also disables Alt+Tab and other hotkeys for switching applications. No workaround for this has yet been discovered.