Variable: ARABIC_SUBSET_UNICODES

const ARABIC_SUBSET_UNICODES: readonly ["U+0600-06FF", "U+0750-077F", "U+08A0-08FF", "U+FB50-FDFF", "U+FE70-FEFF", "U+061C", "U+200C-200F", "U+2066-2069"];

Defined in: fonts.ts:29

The unicode-range of the shipped subsets, and the --unicodes argument the build tool passes to pyftsubset — one constant so the two cannot drift.

The four bidi entries are not decoration. U+061C (Arabic letter mark) and U+2066–2069 (the isolates) are what §5 of docs/13 wraps numerals in; a subset that drops them makes the browser fall back to a different font for the control character alone, which resets the itemisation run and breaks the cursive join around it.