Answer a number from 0 to 15 that indicates which of the sixteen
display rules is to be used when copying the receiver's model (a
DisplayText) onto the display screen.
Normally only sent to a StandardSystemView, but for casees where a DisplayTextView is used alone, without a superview, in which we make this a no-op, put in so that the Character Recognizer doesn't fail. 8/9/96 sw