Most fonts are designed for the Latin script, but many do not support certain diacritics and extensions which are necessary for certain languages. Or, even when they do, the appearance is not always in line with the expectations of readers of that language. Even many professionally designed fonts have issues with certain characters.
The localization features in OpenType are useful in order to ensure that users get the best output from our fonts. But does anyone know of a list of resources like Adam's which discuss considerations applicable to other languages? For example, I know of issues with Ş/Ș and Ţ/Ț in Romanian fonts (which is well-known). But what about more niche examples like the different appearances of capital Ŋ, or different placements/accents in Najavo or Marshallese?
Of course, not all fonts will support all Latin-based languages. But while it would take a lot of effort to add an entirely new character set for non-Latin languages, for these languages, it would probably be easier to support them — if only the information were collected for the benefit of designers.
Does anyone know of any resources or have any tips to share?
Eng (1) is used in several African languages. There are two regional variants, (3) and (4). AFAIK, they are not tied to languages but to geography. So, you can't use OpenType features to set an automatic substitution for these variants. The best one can do is to offer (3) and (4) as alternates. The number of fonts that do this is near zero —I only see this in my own projects and in SIL fonts.
Denis Jacquerye is the specialist to watch about Eng and other African issues. Victor Gaultney and John Hudson are also amazing sources of good, trustful info.
I think that makes sense if one is supporting large character sets that cover African languages as well as European ones. African use of the letter, in its (1) form, is much more widespread than any European use.
A lot of fonts, for simply market reasons, target smaller sets of languages, often focusing on European languages and following standardised character sets for that purpose. I don’t think it is possible to determine what the correct default form of Eng should be in a font without considering the remainder of the character set and what target languages it supports.
For example, for Latin: https://scriptsource.org/cms/scripts/page.php?item_id=script_detail_des&key=Latn
This thread would benefit from having a list of words with those tricky glyph pairings.
Unfortunately, the place where this systematic analysis and implementation has to happen is exactly the place where OpenType GPOS and most font tools are weakest: in the interaction between spacing, kerning, mark positioning and, in some scripts, things like cursive attachment positioning.
Two practices I’ve occasionally indulged in:
German-tagged Ä, Ö and Ü, with lowered dieresis.
English-tagged vertically-flipped left quote marks.
As the initial post in this thread suggests, Latin-M is pretty manageable once you have a base Latin set