I've implemented a solution for this but it's not perfect. The trouble is that, when scrolling, the new JEdit editor panel only re-draws the emerging lines at the top/bottom of the screen (it assumes that all the other lines are unchanged and can simply be shifted up/down). This means that the image drawn behind the text also gets shifted instead of re-drawn.

My solution is simply to force a re-draw when scrolling. This is not perfect as the re-draw is not immediate meaning that the image jumps around a bit.

If anyone can think of a better solution please post it.