On Mon, 10 Aug 2015 17:58:24 +0000 "Andrew Glass (WINDOWS)" <[email protected]> wrote: I had asked:
>> According to the text just after TUS 7.0.0 Figure 23-3 >> (http://www.unicode.org/versions/Unicode7.0.0/ch23.pdf#G25237), ZWJ >> suppresses ligatures in Arabic script. Does this rule apply to other >> normally cursive joined scripts, e.g. Syriac and Mongolian? > To ligate or not to ligate is up to the font designer. Normally, GSUB > lookups that perform ligation will be broken by the presence of ZWJ > or ZWNJ. If a font designer wishes to ligate in the presence of a ZWJ > or ZWNJ then they could choose to include appropriate glyph sequences > in their ligation lookups. For example: > glyphA glyphB -> glyphC > glyphA ZWJ glyphB -> glyphC So, any rule as to what ZWJ means is not implemented in the OpenType engine, but rather in the font. (As is the rule that 'a' does not look like 'b'.) For which scripts may a font designer defensibly omit the duplicate with ZWJ? The TUS says Arabic is one. Are there any others? Richard.

