Re: Please review performance aspects of Incremental Font Transfer

Thanks for sending this for review Chris! This is super interesting!!

Looking at the explainer, I think it could benefit from some examples and
flow diagrams in the part that touches on patch maps.
Some questions that came to mind:

   - Can font processors create any (reasonable) number of potential
   patches for arbitrary codepoint ranges?
   - How would the discovery process work? When would browsers load patches?
   - Are there restrictions on cross-origin serving of the patches? If not,
   is there a risk of privacy leaks? The spec's privacy section discusses the
   risk, but doesn't mention mitigations AFAICT


On Wed, Jul 24, 2024 at 3:27 PM Chris Lilley <chris@w3.org> wrote:

> The Web Fonts WG requests review of the Incremental Font Transfer (IFT)
> specification by the Web Performance WG. A new WD of IFT was published
> on 9 July 2024 [1]
>
> This specification defines a way to incrementally transfer fonts from
> server to client. Incremental transfer allows clients to load only the
> portions of the font they actually need which speeds up font loads and
> reduces data transfer needed to load the fonts. A font can be loaded
> over multiple requests where each request incrementally adds additional
> data.
>
> Earlier work [2] demonstrated the performance improvements in terms of
> bytes transferred and reduced network delay, for various network types.
>
> The current draft (unlike earlier drafts) does not require a dynamic web
> server to compute patches. Instead, a table of URLs to the pre-computed
> patches is contained within the subsetted font itself. This means that
> patches are applicable to multiple users, and are cacheable.
>
> Also (unlike earlier drafts, which used a custom patch request protocol)
> the patches are requested with a regular HTTP GET.
>
> We have an Explainer [3].
>
> We would particularly value the review of the Web Performance WG on
> those aspects, although review of the entire specification would of
> course be most welcome.
>
> Comments should be raised as individual issues on our GitHub [4].
>
> [1] https://www.w3.org/TR/2024/WD-IFT-20240709/
> [2] https://www.w3.org/TR/PFE-evaluation/
> [3] https://github.com/w3c/IFT/blob/main/IFT-Explainer.md
> [4] https://github.com/w3c/IFT
>
> --
> Chris Lilley
> @svgeesus
> Technical Director @ W3C
> W3C Strategy Team, Core Web Design
> W3C Architecture & Technology Team, Core Web & Media
>
>
>