For Sinhala, the following named sequences are defined (for good reasons): SINHALA CONSONANT SIGN YANSAYA;0DCA 200D 0DBA SINHALA CONSONANT SIGN RAKAARAANSAYA;0DCA 200D 0DBB SINHALA CONSONANT SIGN REPAYA;0DBB 0DCA 200D
I'll abbreviate these as Yansaya, Rakaransaya, and Repaya, and I'll write Ya for 0DBA and Ra for 0DBB. Note that these give rise to two potentially ambiguous codepoint strings, namely 0DBB 0DCA 200D 0DBA 0DBB 0DCA 200D 0DBB I'll concentrate on the first, as all arguments apply to the second one analogously. At a first glance, the sequence 0DBB 0DCA 200D 0DBA has two possible parses: 0DBB + 0DCA 200D 0DBA, i.e. Ra + Yansaya 0DBB 0DCA 200D + 0DBA, i.e. Repaya + Ya First question: Does the standard give any guidance as to which one is the intended parse? The section on Sinhala in the Unicode Standard is silent about this. Is there a general principle I'm missing? Sri Lanka Standard SLS 1134 (2004 draft) states that Ra+Yansaya is not used and is considered incorrect, suggesting that the second parse (Repaya+Ya) should be the default interpretation of this sequence. However, SLS 1134 does not address the potential ambiguity of this sequence explicitly and the description there could be read as informative, not normative. Second question: Given that one parse of this sequence should be the default, how does one represent the non-default parse? In most cases one can guess what the intended meaning is, but I suspect this is somewhat of a gray area. In practice, trying to render these problematic sequences and their neighbors in HarfBuzz with a variety of fonts results in a variety of outcomes (including occasionally unexpected glyph choices). If the meaning of these sequences is not well defined, that would partly explain the variation across fonts. Am I missing something fundamental? If not, it seems this issue should be called out explicit in some part of the standard. Regards, -- martin
