FcStrStrIgnoreCase - misleading summary in docs
See https://www.freedesktop.org/software/fontconfig/fontconfig-devel/fcstrstrignorecase.html
The Name section summarizes this function as "locate UTF-8 substring ignoring ASCII case", but then under Description the text says "case-insensitive for all proper UTF-8 encoded strings", which sounds as though the case-insensitivity applies to the full Unicode repertoire.
Checking the code, I believe the latter is correct, and the summary "ignoring ASCII case" is wrong.