Very true. Even in "leaf" components (I'd never heard them called that. Cool.), the actual appearance is often dependent on some state that only the parent knows. Is the button highlighted or dimmed? Blue or red? Well, the
button component doesn't know. (It shouldn't). But the parent who spawned it must know and pass that information into the button by a param.
This should, ideally, be as short and sweet as possible. In reality, like you say, the two ideas (visual + biz logic) will always be married in any non-trival application.
