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

[Behdad Esfahbod]

I sketched how HarfBuzz's main OT+AAT "unishaper" works:

  https://prezi.com/view/THNPJGFVDUCWoM20syev/

I will keep adding more details, including the per-script parts. Feedback
welcome.

behdad
http://behdad.org/


On Fri, Aug 21, 2020 at 1:28 PM John Hudson <john at tiro.ca> wrote:

> 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
>
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