[HarfBuzz] Valid range of deltaGlyphID is too small

[Dohyun Kim]

2011/9/28 Behdad Esfahbod <behdad at behdad.org>:
>
> I did that intentionally.  I have not found any references in the spec as to
> how to handle overflow and underflow.  Note that by not overflowing, I'm
> implicitly allowing limited support for fonts with more than 64k glyphs.  If I
> wrap around, it would be much harder to work with those fonts.  Specifically
> what should happen when you add a delta and there is no overflow, but the
> resulting glyphID is over 64k?  Ie. the initial glyphID was over 64k?
>

I cannot test that case; the font file I tested does not have any
lookup table where initial gid is over 64k.

GSUB single format 1 routine seems to return minus gid when
deltaGlyphID is very big.
For instance:

Initial gid = 9422
Resulting gid = -1389; this should be 64147.

-- 
Dohyun Kim
College of Law, Dongguk University
Seoul, Republic of Korea