[HarfBuzz] fallback kerning

[Behdad Esfahbod]

Thanks both.  I still have an item in hb-ng/TODO for "kern/GPOS interaction".
 Around the same time that the commits Evan pointed to happened, this issue
was being discussed on the OpenType mailing list.  I need to go back and
figure out what the conclusion was...

behdad

On 07/27/10 19:12, Evan Martin wrote:
> I remember running into this issue when experimenting with harfbuzz-ng
> some months ago.
> 
> For reference, take a look at commits
>   d740c8f78bcbe80a8bcd8a9468830a406da37cc0
> and
>   e70f45eb522bcb41388cc218b79bbd6aaecf8050
> 
> On Tue, Jul 27, 2010 at 3:55 PM, Jonathan Kew <jonathan at jfkew.plus.com> wrote:
>> Hi Behdad,
>>
>> We're seeing some widespread fonts (such as Verdana and Trebuchet) where there is a GPOS table that does *not* include a 'kern' feature, and an old-style TrueType 'kern' table is present. To support fonts like this, I think we need to modify the positioning logic so that the use of the fallback positioning code is not dependent simply on the presence of a GPOS table, but on whether it actually includes a 'kern' feature.
>>
>> Suggested patch is attached. This checks at feature-compilation time whether a 'kern' feature is present (or if it has been explicitly disabled), and returns a boolean to indicate whether kerning was "handled" at this level; if not, the fallback path will be used.
>>
>> Jonathan
>>
>>
>>
>>
>>
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>>
>>
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