Although the Unicode Bidirectional Algorithm clearly defines how to reorder characters in memory, I don’t understand precisely what it means to display one character after another once they’ve been reordered; specifically, when bidi reordering changes the number of user-perceived characters.
For example, after a right-to-left override, the Hangul string 보기 (“bogi”) becomes 기보 (“gibo”) in visual order. However, its NFD form is reordered by jamo instead of by syllable; that is, it looks like “igob”. I don’t think it is the intent of the algorithm that canonically equivalent strings display so very differently, but I can’t find any explicit guidance. What should a UBA-conformant renderer do? Another unclear case is Indic clusters. षिक् is unambiguously two clusters, but after an RLO, and after following rule L3 to put combining marks after their bases, it looks like one cluster: क्षि. If Devanagari were actually written right-to-left, I would expect it to stay as two clusters: क्षि. Does the UBA prefer one rendering over the other, or is this outside its scope?
