TextSpanner custom line

[Artur Wrona]

Hi, dear Lilypond users. I ask at forum very rarement, always first
find at Google, DuckDuck.. but now I didn't found solution for one
thing. So... Is anybody, who knows, how to creat own symbol for
textspanner? I would like for example use chars pattern instead line. I
know that I must use \override TextSpanner.stencil or \override
TextSpanner.style . I didn't found, how to define own line style. In
future I'm going to use segment symbols from Bravura font (I know how
to input Unicode symbols - rather easy to find). 
Thanks in advance.
Artur Wrona.