> > Specify it in pixels
> No thank you.
The article is NOT about px versus em or pt.
It is about specifying sizes in a way that makes sense, i.e. based on visible quantities rather than abstract quantities that are difficult to understand.
> No thank you.
The article is NOT about px versus em or pt.
It is about specifying sizes in a way that makes sense, i.e. based on visible quantities rather than abstract quantities that are difficult to understand.
Which ultimately means that font sizing is entirely nonsense: the only thing you can say is font size 1 is smaller than font size 2, but it’s impossible to say by how much, or guess the difference, except when talking about one, and only one font.
That is, a font with size 16 roughly corresponding to the same size in another font is entirely defined and enforced by nothing at all — it’s purely a “happens to be true”.
Thus, the only real way to handle font sizing predictably is to never switch them out, because you’re really dealing with undefined behavior
The article is mostly about switching two fonts with the expectation that the visual size of the characters remains consistent. That expectation fails because the em size is arbitrary with respect to the visible caps-height.
As it stands, fonts can have drastically different rendered sizes at the same specified font size. This leads to all sorts of problems, like ensuring fallback fonts have similar metrics to the one you expect to load.
It would fail with caps-height, too, as other visible measures of characters (not just abstract ones like em) have no guaranteed consistent relationship to caps-height, so, as such, there's no guarantee that fonts with the same caps-height have the same “visual size”, or even visual vertical size, since cap height doesn't i close descender and ascender height.
If the font size would be specified using only cap height then the work of font designer on specific relationship between negative and positive space and line height would be thrown out. That would be a net negative for the state of typography on Web.
Again putting things into fixed size containers that do not adjust based on different font face is not a good practice and it is not what Web meant to be.