That is correct. Due to the design of OTF, the font tables are insufficient.
Each Indic script requires its own orthographic syllabization logic. Where
there is common logic, it will be shared in the implementation.

Arabic script has other script specific requirements outside of the font
tables. For example, the determination of whether a character is subject to
certain contextual substitution.


On Wed, Jun 22, 2011 at 12:08 PM, Simon Pepping <>wrote:

> Glenn,
> I studied the OpenType spec. With that knowledge I assumed, perhaps
> naively, that for all OT fonts a correct rendering can be obtained by
> following the directives in the tables in the font.
> The code of the ComplexScripts branch provides specific processing of
> each Indic font (until now Devanagari). The main action seems to be
> that each word is first syllabized and then each syllable is
> separately submitted to the substitution code. Do I understand
> correctly that the font tables alone do not allow one to achieve a
> correct rendering, and that it is necessary to understand the syllabic
> structure of the text?
> Simon

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