> it is a more serious problem that requires changes deep in Plan 9's
> drawing library and we see it all the time without it even bothering
> us -- try dragging a window border over something that does draw() in
> the meantime and you'll get a leftover red streak from the border.
> the solution is to slightly resize the original window causing a new
> draw() to refresh it.

that's a different problem as far as i'm aware - due to the fact that
rio uses unbuffered windows to draw the borders.