@Romain Awesome - thanks for this:
Would it be possible for you to post a more complete sample of the code (i.e. what is in the customDraw method)
I'm a bit of a noob at C++ and I'm getting errors if I use the code you posted with a 'customDraw' method of my own...
No need, I checked out the demo sources and, once I knew what I was looking for, it all sort of made sense!