A mixed-reality head mounted display (HMD) device supports a three dimensional (3D) virtual world application with which a real world desktop displayed on a monitor coupled to a personal computer (PC) may interact and share mouse input. A mouse input server executing on the PC tracks mouse movements on the desktop displayed on a monitor. When movement of the mouse takes it beyond the edge of the monitor screen, the mouse input server takes control of the mouse and stops mouse messages from propagating through the PC's system. The mouse input server communicates over a network connection to a mouse input client exposed by the application to inform the client that the mouse has transitioned to operating in the virtual world and passes mouse messages describing movements and control operation such as button presses.