[mpeg-OTspec] Different OpenType/CFF behavior on Windows 10 with 'gasp' table

[John Hudson]

On 11122018 12:32 PM, Ken Lunde lunde at adobe.com [mpeg-OTspec] wrote:
> They suspect that DirectWrite may be sensitive to the presence of the 
> 'gasp' table in OpenType/CFF (aka non-TrueType) fonts, which matches 
> their observations.

That makes sense to me; in fact, if someone had asked me to predict 
whether a gasp table would influence rendering of CFF fonts in DWrite, I 
would have guessed yes. The gasp table influences the antialiasing model 
applied in Windows rendering environments, so when one of those 
environments starts rasterising CFF fonts it makes sense that the 
antialiasing of those outlines becomes subject to the same influence. 
It's probably worth experimenting with to see if the gasp table is ever 
actually of beneficial use in a CFF font. Quite possibly, it isn't — 
since the gridfitting controls and TTF instruction interaction are not 
the same for CFF —, in which case the spec should clearly reserve the 
gasp table for TTF. But if there is a possible benefit, maybe we should 
allow this with caveats?

JH


-- 

John Hudson
Tiro Typeworks Ltd    www.tiro.com
Salish Sea, BC        tiro at tiro.com

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