wxPython OGL: How make LineShape text b/g transparent?

[John Perks and Sarah Mount]

(Having problems receiving wxPython mailing list entries, so I'll ask here.)

I'm using wxPython 2.5.4, windows ansi version, on Python 2.4, the OS in
Win98SE. My application manipulates a graph, with CircleShapes for nodes and
LineShapes for arcs. The user needs to be able to get and set text on a arc.
When I use LineShape.AddText(), a large rectangle of background colour
blocks out much of the line, crucially including the arrow at the midpoint.

How I can I make the text b/g transparent so the lines can be seen, and
further is it possible programmatically to displace the text such that the
arrow is not covered?

Thanks

John