BladePoint I was unable to extend starling.text.TextField to do this because I can't override its private methods. I had to copy and paste a lot of code though, which I suppose has some licensing problems?
First of all, copying Starling's code will never cause you any licensing problems! In fact, anytime somebody re-uses code from Starling, I'm happy about it! 😀
The reason those methods are private, though, is that my recommendation is to not subclass it, but instead (in your case) to extend "BitmapFont". I created a similar (but far more limited!) extension as a proof of concept here:
The advantage of this approach is that you can make a standard TextField switch between different font renderers — i.e. a TextField could decide for itself if it uses, say, TrueType font rendering (via a TrueTypeFontCompositor) or a StyledBitmapFont.
But in the end, it's not a problem to copy & paste the class directly and make the adaptations where you need them. 😄 The class looks super useful, in any case! 👍