Text render using Xamarin Forms + OpenGLView (OpenTK)

Could anybody post a sample showing how to render text using a Xamarin.Form.OpenGLView? Even better showing how to use a custom font file (TTF).

I've looked for samples, but can only find the one in the documentation and another on painting a triangle. Is there any good URL or other resource where to get more info on using OpenGLView's.

Thanks!