The system provides a pointer to allow the user to make selections from
menus, choose gadgets, and so on.  The user may control the pointer with a
mouse, the keyboard cursor keys or some other type of controller.  The
specific type of controller is not important, as long as the proper types
of input events can be generated.

The pointer is associated with the active window and the input focus.  The
active window controls the pointer imagery and receives the input stream
from the mouse.  The pointer and mouse may be used to change the input
focus by selecting another window.

 Pointer Position    Custom Pointer    Pointer Example