Why ascender can't use interline gap, but diacritics can?

Igor Petrovic

It is a norm that the basic Latin characters don't go beyond the em space.

And now I have a kind of typical situation in Black master. Lowercase /f and /i need more space (on the ascender side) for the hook and dot. I lowered the /f bar and /i apex a bit, but I still need more space.

Why is it a good idea not to go beyond the defined ascender here, if diacritic characters will do it anyway? Or I can go over the ascender a bit, anyway?

John Hudson

You can definitely do this. The relationship of outlines to the body (em) height is arbitrary but conventional. So if you have an existing design with a particular relationship to the body height, and then add another master or some additional glyphs that need to be taller, then they can extend beyond the em height. You just need to be aware of the impact on apparent linespacing.

John Savard

I can see one reason why, despite the way TrueType and OpenType actually work, as John Hudson had explained, that the convention that ascenders must stay within the bounding box, while diacritics are more free had arisen.

Texts will always include letters with ascenders.

Diacritics, though, are... optional.

At least if your language happens to be English.

So, since, in my personal opinion, it's kind of silly to have a font which can't be set solid at whatever its nominal point size is, the conclusion is that if it's a font serving other Latin alphabet languages then those diacritics ought to be pulled strictly within the bounding box too - thus going outside the convention in the other direction.

Of course, allowing diacritics on upper-case characters to go outside the box is still a legitimate option, since whether or not to use them is considered to be a choice in many languages that use accents.

In the era of hot metal, of course, accented capital letters that fit within the nominal line spacing by being shrunk below their accents were a thing. That tends not to be bothered with nowadays.