Mouse Tracking Sphere-Requirements

From IGSTK

Viewer Requirement

   1. VTK objects would be used to create and render the sphere in a 
      VTK window.

User Interface Requirements

   1. FLTK would be used for the user interface.
   2. A VTK-FLTK Interactor* is required for embedding VTK window into
      an FLTK window.
      *This interactor is already available as part of ITK Applications.
      (to decide on how we distribute this interactor code).

Mouse Tracker Requirement

   1. The tracker should provide mouse position in the viewer 
      window on demand.   
   2. When the mouse cursor in outside the viewer window, the
      last mouse position, when the mouse cursor was in the 
      viewer window, should be maintained.