(apologies - I'm completely new to this kind of forum. and I have no idea if I'm doing this right.)
All I wanted to say was that putting $mw->InvalidateRect(1); at the end of the splitter onResize method (called "do_splitter" in the example) solved the weird (hard to explain) artifact problem for me. (They seemed to be echoes of the splitter.) ~Greg.ps: my problem now is I don't know how to make the splitter visible - with color, or 3-D styles. )