Procedure ScreenToVScreen4 (Var X1,Y1,X2,Y2:Integer)

    Updates VX and VY       : No
    Updates Cursor Position : No

    This converts screen coordinates to virtual screen coordinates.

    For example, if the viewable  area  (screen) is from (5,5) to (84,29)
    then calling

    X1:=1;
    Y1:=2;
    X2:=4;
    Y2:=4;
    ScreenToVScreen(X1,Y1,X2,Y2);

    will cause

    X1 = 5,
    Y1 = 6,
    X2 = 8  and
    Y2 = 8.