[HarfBuzz] Post Base Substitution fails with Malayalam repha

[Rajeesh K Nambiar]

On Fri, Sep 13, 2013 at 9:06 AM, Jonathan Kew <jfkthame at googlemail.com> wrote:
> Hi Suresh,
>
> Please specify the exact font (version? link?) being used, to ensure we can
> reliably reproduce the problem. Thanks.

We have also noticed this issue and been discussing about it.
The issue is due to the 'post-base' reordering of Dotreph. Consider
'ൎക്കു' (Dotreph+Ka+Virama+Ka+Virama+U). But harfbuzz reorders
Dotreph, so the sequence becomes (Ka+Virama+Ka+Virama+Dotreph+U). In
traditional orthography, (Ka+Virama+Ka+Virama+U) should form a single
glyph.

We have been trying to use 'abvm' for Dotreph and corresponding GPOS
rules, but such 'postbase' cases break due to reordering of Dotreph.

I'll upload a version of Meera font this evening once I have access,
to help with reproducing the issue.

>
>
> On 13/9/13 07:50, Suresh P wrote:
>> Hi,
>>
>> It seems that the post base substitutions is not happening with
>> Malayalam reph. The uukara ligature glyph (used traditional Malayalam
>> lipi) substitution via post base ligature lookup should happen prior to
>> the reordering of the reph glyph. A test case for the word 'പാൎക്കുക' is
>> attached.
>>
>> -suresh
>>
>>
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>
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-- 
Cheers,
Rajeesh
http://rajeeshknambiar.wordpress.com