[mpeg-OTspec] Registering new GPOS features?

[Ken Lunde]

John,

That concern was mentioned earlier on in the blog article:

> ...and while the existing kerning features were discussed as a possible vehicle for such metrics information, there is an obvious conflict for fonts that are intended to supply genuine kerning values versus contextual spacing values that generally used fixed values and affect a much smaller number of glyphs.

In other words, Japanese fonts that include genuine kerning data in these two GPOS features, kern and vkrn, also include metrics information in the palt and vpal GPOS features that also need to be turned on, which generally makes the kana proportional, along with most of the punctuation and some symbols, plus kerning values, some of them subtle, on top of all that. That's a bunch of metrics complexity that simpler environments that have no line-layout support whatsoever, which may merely want to get rid of unused "space" in full-width brackets and other full-width punctuation, in the form of half or a quarter of an em.

Regards...

-- Ken

> On Apr 23, 2018, at 2:46 AM, John Hudson <john at tiro.ca> wrote:
> 
> On 22-04-2018 22:14, Ken Lunde lunde at adobe.com [mpeg-OTspec] wrote:
>> Vladimir,
>> 
>> When is the next opportunity for registering new features? I ask, because I may have a couple in the proverbial hopper:
>> 
>> https://blogs.adobe.com/CCJKType/2018/04/contextual-spacing.html
>> 
> 
> From that discussion paper:
> 
>     'Our meeting ended with lunch at PHB, along with the idea to register two new OpenType 
>     GPOS (Glyph Positioning) features that would be tentatively tagged 'cspc' (“Contextual 
>     Spacing”) and 'vcsp' (“Vertical Contextual Spacing”), and which would behave like the 'kern' 
>     and 'vkrn' in that they adjust inter-glyph spacing.
>     ...
>     'In order to be able to test in environments that do not support arbitrary OpenType 
>     features, the example font includes the lookups for the 'cspc' and 'vcsp' GPOS features 
>     in the 'kern' and 'vkrn' GPOS features, respectively.'
> 
> Can you explain why you want to register two new features for this, rather than just putting the lookups in the 'kern' and 'vkrn' features as in this demonstration?
> 
> JH
> 
> -- 
> 
> John Hudson
> Tiro Typeworks Ltd    
> www.tiro.com
> 
> Salish Sea, BC        
> tiro at tiro.com
> 
> 
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