When I needed a good font support for one app I did some research and found out that the best functionality out of the box is in current web browsers. There're some libraries for font rendering you could try to use, in fact web browsers use them already but when it comes to typography, glyphs, kerning, sub-pixel rendering, etc. there're A LOT of small things you need to think about so even using all the libs is still very hard.
We've ended creating a HTML and rendering it with WebKit to a bitmap. So I'd suggest you to look for an engine that could take such custom bitmap and use it on UI controls.
One more thing is that if you target the best possible quality you should push as much data as possible through HTML rendering. So instead of rendering some text as black-on-white in some custom resolution and then scaling/coloring/rotating it in the engine, it's better to set desired text and background color, size, rotation, etc. in an HTML and then just put the resulting bitmap on the screen. This way you have a chance to not to break sub-pixel rendering and antialiasing.