Every time I move the mouse across the menu bar the menu drops down but theunderlying window is partly drawn over it.I only notice with netsurf, and I assume it is the program shown in yourscreenshot too. In that case I'm pretty sure it's a netsurf-bug.
I think here we have 2 odd things:1. Netsurf fails to do correct clipping (I'm assuming the visible rectangle list is correct and Netsurf DOES iterate over the visible rectangles) 2. Why does XaAES send an WM_REDRAW message when you move from one menu item to another one? AFAIK there is an Buffer called "1/3 buffer" (or similar name...) in the AES for such things. Please tell me :)
Greets, Ole