Re: Draft of feature encoding changes

The link included there is a direct download link for the 2nd edition of
the OFF (published 2009). We are now at 4th edition standard with two
additional amendments finalized, and the 5th edition is now on the way
(still a working draft though).
I wouldn't use that link from specref, it's way outdated. Rather, I would
simply reference the main ISO page for the standard (
https://www.iso.org/standard/74461.html)  because it's static and will
always be updated to the most recent version. We can also mention that it
is available free of charge for download from ITTF.


On Wed, Jun 21, 2023 at 2:51 PM Garret Rieger <grieger@google.com> wrote:

> Looks like the ISO standard is in spec ref (
> https://www.specref.org/?q=open%20font%20format) so I should be able to
> link it via bikeshed.
>
> On Wed, Jun 21, 2023 at 10:58 AM Skef Iterum <siterum@adobe.com> wrote:
>
>> Vlad - I was referring specifically to this:
>> https://www.iso.org/obp/ui/en/#iso:std:iso-iec:14496:-22:ed-4:v1:en:sec:2
>>
>> Skef
>> ------------------------------
>> *From:* Vladimir Levantovsky <vladimir.levantovsky@gmail.com>
>> *Sent:* Wednesday, June 21, 2023 6:24 AM
>> *To:* Skef Iterum <siterum@adobe.com>
>> *Cc:* Garret Rieger <grieger@google.com>; w3c-webfonts-wg <
>> public-webfonts-wg@w3.org>
>> *Subject:* Re: Draft of feature encoding changes
>>
>>
>> *EXTERNAL: Use caution when clicking on links or opening attachments.*
>>
>>
>> I get it that the ISO website is confusing, but you only have to pay for
>> paper copy of the standard. If you follow the blue box “download” link, it
>> will bring you to the list of publicly available standards - you scroll
>> down to ISO/IEC 14496-22 and download the PDF file after you click through
>> the license dialog box. (Or, just use the link in my previous email.)
>>
>> Thank you,
>> Vlad
>>
>>
>> On Jun 20, 2023, at 10:51 PM, Skef Iterum <siterum@adobe.com> wrote:
>>
>> 
>> The fact that there's an HTML preview with only the early sections and
>> that asks for money is ... unfortunate.
>>
>> Skef
>> ------------------------------
>> *From:* Vladimir Levantovsky <vladimir.levantovsky@gmail.com>
>> *Sent:* Tuesday, June 20, 2023 6:49 PM
>> *To:* 'Garret Rieger' <grieger@google.com>; 'w3c-webfonts-wg' <
>> public-webfonts-wg@w3.org>
>> *Subject:* RE: Draft of feature encoding changes
>>
>>
>> *EXTERNAL: Use caution when clicking on links or opening attachments.*
>>
>>
>> Regarding ISO OFF text – it is publicly available, but it’s a PDF
>> document that can only be downloaded in full, not making it possible to
>> link to a particular chapter or feature.
>>
>>
>>
>> I think we can utilize a dual approach where normative references section
>> includes the reference to OFF using main ISO link (
>> https://www.iso.org/standard/74461.html), and we can also use direct
>> links to various OT pages offering it as informative reference with the
>> note that the content is identical to ISO OFF standard.
>>
>>
>>
>> Also, note that the blue box on the ISO OFF page provides the information
>> and link for free download:
>> https://standards.iso.org/ittf/PubliclyAvailableStandards/
>>
>>
>>
>> Vlad
>>
>>
>>
>>
>>
>> *From:* Garret Rieger [mailto:grieger@google.com]
>> *Sent:* Tuesday, June 20, 2023 8:26 PM
>> *To:* w3c-webfonts-wg (public-webfonts-wg@w3.org) <
>> public-webfonts-wg@w3.org>
>> *Subject:* Draft of feature encoding changes
>>
>>
>>
>> As discussed on the call this morning I've made a draft of some changes
>> to how we encode the feature tag set included in the request. The PR can be
>> found here: https://github.com/w3c/IFT/pull/149
>>
>>
>>
>> Note, there are a couple deviations from what we discussed:
>>
>>    1. We talked about switching to referencing the ISO OFF specification
>>    instead of Microsoft's OpenType spec. However, it appears that ISO OFF
>>    isn't publicly available. So I can't easily link to it from the IFT
>>    specification. Given that, I think it's more useful for implementers to
>>    continue to link to the public OpenType one instead.
>>    2. After thinking about the process of how we could actually add
>>    entries to the list after the initial publication I've decided we'll need
>>    some versioning mechanism to accomplish future updates since the client and
>>    server must be speaking the same encoding. For now since there is only one
>>    version, I haven't actually introduced the mechanism yet, but I did note in
>>    the appendix that the current list is version 1 and future updates may
>>    introduce a new version plus a mechanism to communicate it (likely a new
>>    field in client state and request).
>>    3. One thing that I forgot to mention during the call which is
>>    important is that the sorted integer list is delta encoded. That means we
>>    encode the delta between an entry in the list and the previous entry
>>    instead of the absolute value. This means generally most entries should
>>    encode in one byte even if we have IDs that are greater than 127. I made
>>    one small change to help here and moved the ss01-ss20 and cv01-cv99
>>    encodings to the end of ID space so they don't add large gaps between other
>>    unrelated feature tags. With that change everything other than those two
>>    groups now have ID's less than 127 which guarantees they will encode in one
>>    byte.
>>
>>