Fwd: Please review performance aspects of Incremental Font Transfer

-------- Forwarded Message --------
Subject:  Re: Please review performance aspects of Incremental Font 
Transfer
Date:  Fri, 2 Aug 2024 07:59:44 +0200
From:  Yoav Weiss <yoav.weiss@shopify.com>
To:  Chris Lilley <chris@w3.org>
CC:  public-web-perf@w3.org



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