Wow, nice !!
I worked a bit on Drawable Spans too, and they are not easy at all to read (ok, it is not supposed to be read by anything else than plasma itself, but still...).
Extracting any object from them is a real pain (that's what I was trying to do, before Dustin made his distillation tool available in the command line of Drizzle).
Before we get a better post about it from Branan, you might want to check these forums - there are some useful infos in them.Here
Have fun messing with it