'Benutzereingaben 
    Dim userwidth As Single = 600, userheight As Single = 800
 
    'angepasste Größe (maximal 400 * 400) 
    Dim displayheight As Single = userheight
    Dim displaywidth As Single = userwidth
 
    If userwidth > 400 Then
       displayheight = userheight * 400 / userwidth : displaywidth = 400
    End If
 
    If displayheight > 400 Then
       displaywidth = userwidth * 400 / userheight : displayheight = 400
    End If