[kbr]

Their semantics might be consistent, but they sort of leak into the parent. Height and width are local to what the component renders, and they don't depend on the parent (as long as they aren't relative sizes). But things like margin and align-self change how the parent renders all of its children.

In other words, the view rendered by the component is a function of properties like height and width. But when you throw in margin or align-self, the component now depends on its siblings.

The OO perspective is interesting — I agree that it effectively makes these things hard to express. I now think that it's more of a problem relating to encapsulation and isolation. OO would isolate it through a child component interface while FP would have a function that can't affect siblings.

[iainmerrick]

Yeah, I think we’re mostly agreeing! Encapsulation and isolation are the key bits, and both FP and OO suggest ways to achieve them.