In certain types of literature, the name Allah and words related to this name are given unique rendering. Unicode has a presentation form character (U+FDF2 ARABIC LIGATURE ALLAH ISOLATED FORM) that implements this rendering and, while this can work (in some fonts) for the word in isolation, it doesn’t help users obtain special rendering in other contexts where it is desired. 

Harmattan provides the special rendering for sequences of Arabic letters that meet specific patterns, giving much more flexibility to document authors.

• Under certain conditions, a sequence of lam-lam-heh will form an Allah ligature:
  • The sequence must include either a preceding isolate alef or a shadda on the second lam, or both.
  • If there is an isolate alef but no shadda, a shadda-superscript-alef will be automatically displayed.
  • The shadda may be followed or preceded by either a superscript-alef diacritic or a fatha.
  • The heh may be either the standard heh (0647) or the heh-goal (06C1).
  • The alef, if present may have marks. Similar characters such as alef-hamza, alef-hamza-below, alef-madda, and alef-wasla will also form the ligature.
  • The first lam may include a kasra, but no other diacritics.
  • The special Unicode character U+FDF2 will always display the Allah ligature.

To disable the special ligature, insert a zero-width joiner character (200D) somewhere in the sequence.