I'm making a choose font dialog that lets you choose the family, size,
and emphasis for a run of text. There's just one hitch left: I've hit a
wall on setting the family on just the selected text -- it appears you
have to set the textStyle globally for the whole paragraph. 

Is there a way to set the textStyle just for a given run within a
NewParagraph? And if this is forbidden, why? Would it be reasonable to
have a subclass of TextAttribute called TextFamily, or to have family be
a slot of TextFontChange?