[MPEG-OTSPEC] Shaping behavior standardization: multi-engine or "Super USE"?

[John Hudson]

On 21082020 12:13 pm, Renzhi Li wrote:
> Therefore, for the shaping behavior standardization, should we 
> standardize all the existing engines (focus on the "status quo"), or 
> work on USE extension to use one single engine for every script?

Both.

We do need to ensure that the existing engines provide consistent 
results for existing fonts built to those specs, even if we also provide 
mechanisms to pass scripts to USE instead.

The USE layout model is both general and particular: it requires fonts 
for scripts with complex shaping requirements for correct text display 
to be made in a very particular ways, which are not compatible with the 
methods used in fonts for existing shaping engines. So passing any 
script that currently goes to a dedicated engine through USE is going to 
require new script tags (or another special convention, e.g. a generic 
script tag. Even simple scripts might involve some different methods 
when being passed through USE, and would need to be considered cautiously.

[With regard to the latter, there was recently a discussion on the Noto 
repo regarding whether scripts with very simple layout requirements 
should be passed to USE*. My inclination is yes, they should, and that 
any newly supported script should be passed through USE regardless of 
the simplicity or complexity of shaping requirements. It would be 
helpful to know the position of the USE implementers on this.]

JH


* https://github.com/googlefonts/noto-fonts/issues/576


-- 

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

NOTE: In the interests of productivity, I am currently
dealing with email on only two days per week, usually
Monday and Thursday unless this schedule is disrupted
by travel. If you need to contact me urgently, please
use some other method of communication. Thank you.