Procedure WindowToVScreen(Var X1,Y1:Integer)

    Updates VX and VY       : No
    Updates Cursor Position : No

    This converts  the  window  coordinates  (X1,Y1)  to  virtual  screen
    coordinates.

    For example, if a  window  is  defined  from  (3,3)  to  (20,20) then
    calling

    X:=1;
    Y:=2;
    WindowToVScreen(X,Y);

    will cause

    X = 3  and
    Y = 4.