[HarfBuzz] OpenType features in ScriptShape/PlaceOpenType

[Behdad Esfahbod]

On 13-08-09 12:09 PM, Andrew Glass (WINDOWS) wrote:
> Hi Behdad,
> 
> The required features are marked in the published specifications where
> applicable. For example:

I know the specs.  But unfortunately they are far from what's actually
implemented in Windows.

For example, in the table you quote:

  * <ccmp> is NOT marked required, but my testing shows that it is NOT turned
off when I set features,

  * <calt> is NOT listed at all, but my testing shows that it is applied by
default, but not required,

  * <locl> is NOT listed either, but testing shows that it's a required feature,

> During Win 8, we added <dist> to the list of required features. Your question
> has made me realize that I need to update this document.

Interesting.  So, is <dist> a required version of <kern> then?

> Note that not all of our engines currently accept custom feature lists. I’m
> currently working on updating our documentation in this area, and will make
> sure that specification of all of the required features is up to date.

That's great to know.  If you are serious about fixing issues in the spec I'll
send a list your way!

Cheers,
behdad


> 
> Cheers,
> 
>  
> 
> Andrew
> 
>  
> 
> -----Original Message-----
> From: Behdad Esfahbod [mailto:behdad.esfahbod at gmail.com] On Behalf Of Behdad
> Esfahbod
> Sent: Friday, August 9, 2013 8:53 AM
> To: Andrew Glass (WINDOWS)
> Cc: Peter Constable; Harfbuzz
> Subject: Re: OpenType features in ScriptShape/PlaceOpenType
> 
>  
> 
> Thanks Andrew.  That's what I suspected.  Can you please clarify which
> features are considered non-required?  Is that exactly kern, liga, clig, and calt?
> 
>  
> 
> Cheers,
> 
> behdad
> 
>  
> 
> On 13-08-09 11:50 AM, Andrew Glass (WINDOWS) wrote:
> 
>> Hi Behdad,
> 
>>
> 
>> Yes, this is the design. If a caller passes a list specifying features they
> wish to have applied, the need to specify all non-required features. For
> example, if they want to turn off kern and add tnum they just pass the set of
> optional features that they want to have applied.
> 
>>
> 
>> Cheers,
> 
>>
> 
>> Andrew
> 
>>
> 
>> -----Original Message-----
> 
>> From: Behdad Esfahbod [mailto:behdad.esfahbod at gmail.com] On Behalf Of
> 
>> Behdad Esfahbod
> 
>> Sent: Friday, August 9, 2013 6:45 AM
> 
>> To: Andrew Glass (WINDOWS)
> 
>> Cc: Peter Constable; Harfbuzz
> 
>> Subject: OpenType features in ScriptShape/PlaceOpenType
> 
>>
> 
>> Hi Andrew,
> 
>>
> 
>> Is it intentional that specifying any features in ScriptShape/PlaceOpenType
> disables kern, calt, clig, liga?
> 
>>
> 
>> Thanks,
> 
>> --
> 
>> behdad
> 
>> http://behdad.org/
> 
>>
> 
>  
> 
> --
> 
> behdad
> 
> http://behdad.org/
> 
>  
> 

-- 
behdad
http://behdad.org/