This may improve reliability with left click select and pen input, assuming
that the place where the pen first touched the surface is closer to the
intended location than where it was released from the surface.
I'm not sure if this will make a significant difference in practice, but it
seems worth a try.
Was using UI_BLOCK_LOOP to control draw style,
this meant we couldn't use popup theme colors for cases
where it the interface has the same purpose as a popup but happens
not to use this flag.
