[XeTeX] Trouble with displaying word containing 3 conjunct consonants in Devanagari

[Robert Zydenbos]

Jonathan Kew schreef:

> On 29 Sep 2009, at 18:13, Peter Dyballa wrote:
>
>> You're not telling the XeTeX backend which script to use. This might 
>> produce the seen failures...
>
> No. The example is using Devanagari MT, which is the AAT font shipped 
> with OS X. AAT fonts do not require a Script specification, as the 
> engine is entirely generic and all the shaping behavior is in the 
> font. Adding [Script=...] would cause fontspec to load the font as 
> OpenType, and this would completely *disable* the desired features.
>
> The problem sequence originally cited was ङ्ख्ये, which fails to display 
> a 3-consonant conjunct, despite the use of the Additional Conjuncts 
> feature, although the necessary left-linking form of YA is present in 
> the font. Robert's example, on the other hand, used the word सङ्ख्या, 
> and in this case the triple conjunct does form. The key difference 
> appears to be the immediately-following vowel matra: Ravi's example 
> had  े on the य, and this is apparently conflicting with the rule to 
> access the left-linking glyph. I'd consider this a bug in the AAT 
> tables of the font.

Right, a specific flaw in Devanagari MT concerning the combination ṅ + k 
/ kh / g / gh + ye (only ye: not yā, yo,...), it seems. See the 
attachment, where I try to write "ullaṅghye ullaṅghyo saṅkhye saṅkhyā 
gāṅgye gāṅgyo aṅge ārghye kārtsnyaṃ kārtsnye vaktre" ('Kārtsnya' is my 
favourite word for testing a complex ligature: 5 consonants and a vowel, 
and it comes out well.) Only the combinations with 'ṅ' and 'ye' have the 
problem. Fortunately such combinations occur rarely in practice -- which 
must be the reason for the glitch having gone unnoticed.

Anyhow, even if the results with 'ṅ' and 'ye' are not quite so beautiful 
as we might like them to be, those combinations are correct and readable 
with the virāma, so the font is usable.

RZ

-- 
Prof. Dr. Robert J. Zydenbos
Department fuer Asienstudien - Institut fuer Indologie und Tibetologie
Universitaet Muenchen
Deutschland
Tel. (+49-89-) 2180-5782
Fax  (+49-89-) 2180-5827
http://www.lrz-muenchen.de/~zydenbos


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