On 23/7/12 13:57, Behdad Esfahbod wrote:
Also noticed that post-base 'LA' is not correctly rendered for 'സ്പ്ലേ'. This one is more interesting. And we differ from Uniscribe, and I see why. Jonathan, this is what's happening: Both Rachana and Raghu have 'half' lookups that subtitute C,H sequences with glyphs that are essentially ligatures of explicit halant on the consonant (not half forms really, from what I can see). As such, our L-matra repositioning logic positions matras to the left of such glyphs. In other words, since there is no explicit Halant glyph, matra is not repositioned. This is exactly what the spec says, and works for Devanagari. But Uniscribe seems to move it anyway. Is it the case that Malayalam does not have half forms? If that is the case, that would explain, and we can adjust this. What other scripts do not have half forms BTW?
AFAIK, Malayalam doesn't have half forms (although it does have a bunch of possible ligated conjunct forms). So perhaps it's appropriate to position the left-matra after "half" forms (that are really composites of consonant with visible halant [candrakala] form). That's also what seems to be happening with the Rachana font under Apple's Core Text shaper, FWIW.
Another issue to check is the handling of a sequence with vowel-matra followed by virama, such as <U+0D38,0D41,0D4D>. I notice that we differ from Core Text on this one (using the Lohit Malayalam font) - our shaper appears to use a ligature of the u-matra and virama, whereas Core Text doesn't ligate them. I haven't tried Uniscribe yet to see what it gives.
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