I've been struggling to find a way to get this to work. I can have "resize freely" or "clamp content", but there is no option that lets allows both.
I could just set it to a fixed size of 300, but I need the label to grow/shrink due to having a background sprite anchored to it.
(NGUIText.GetEndOfLineThatFits is almost what I need (with some extra custom code), but it's giving the wrong side of the string.)