[MPEG-OTSPEC] near-term OT spec work

[Peter Constable]

OpenType / OFF stakeholders:

I want to let you all know that I have been in discussion with the Google Fonts team and Microsoft about getting work on the OpenType spec unblocked for the near term. Google approached me about working on an extension to the COLR table (more below). That was something Microsoft also wanted to see move forward, along with a backlog of reported issues. I've been able to work out compatible agreements with each of them which are making it possible for me to resume working as editor on the OpenType spec for a period of time.

Let me be clear that this is not a long-term arrangement. There has been recent community discussion about better structures for working together on the OpenType spec and, perhaps, other specs related to text layout and shaping. That is a parallel discussion, and this doesn't presume any particular outcomes of those discussions.

There are a couple of specific spec projects that Google and Microsoft agreed I should work on:

The first is to address the backlog of issues on the OT spec that have been reported* to Microsoft since OT 1.8.3 was published (two years ago this month). This will include incorporating anything that was in Amendment 1 of OFF that's not yet reflected in OT. But it would not include extending the OT format with any new capabilities. It also won't include anything regarding shaping-engine / script-implementation specs; it's just the OT spec proper.

* OT spec issues can be reported using the feedback link at the bottom of the page for each page of the OT spec<https://docs.microsoft.com/en-us/typography/opentype/spec/>; these get filed as issues in a public GitHub repo, MicrosoftDocs/typography-issues<https://github.com/MicrosoftDocs/typography-issues>. (I've tagged OT spec issues with the "OpenType spec" label.) For the time being, this remains the preferred way to report issues on the OT spec. I'll say a bit more below about reviewing drafts of changes.

The only technical changes to the OT spec would be corrections to errors or clarifications-some of which might have larger impact, but all of the changes will be proposals offered for broad review. Note that this will not be an attempt to re-write major portions of the spec or rid it of legacy, technical cruft. The main objective is to keep work alive and make incremental but worthwhile improvements.

The second project will be to add some significant new capabilities for color fonts, extending the COLR table to support gradient fills and to integrate variations. This is a proposal that's been floated for a little while. In particular, it was discussed between several companies over a year ago (or maybe earlier?), and a preliminary proposal was drafted by Behdad Esfahbod and Dominik Röttsches. That proposal (with some subsequent revisions) is in the googlefonts/colr-gradients-spec<https://github.com/googlefonts/colr-gradients-spec> repo. I've also prepared a separate doc<https://github.com/PeterConstable/OT_Drafts/blob/master/COLR_V1/COLRv1formats_rev4.md> showing the new structure formats as they'd appear in the OT spec (for those not familiar with C++ template syntax). For now, input should be filed as issues in the googlefonts repo.

In terms of timelines for these two projects, I hope both will progress quickly. The only thing to slow down the first is the volume of feedback to be considered, and possible need for in-depth investigation on some issues to get the right information. The second project still requires some design work, and that might take longer. If both can progress fairly quickly, then I would combine the two into a proposed OpenType 1.9 release. But if the second requires somewhat more time, then I could split these into a 1.8.4 release for the maintenance update, followed before long with 1.9.

For both of these, I'll be working with MS, Google and Vlad Levantovsky to come up with as good a way I can find to make drafts (with changes highlighted) available for public review and input. I'm open to suggestions on how to do this, but for quick progress I'll opt for what's feasible quickly over better long-term options. I know some would like MS's private repo that has the OT sources to be made public; that might not be so easy since that repo has a lot more content than just the OT spec. Something like that might eventually be possible, but we want to make sure that what's best for the long term doesn't get in the way of making some valuable progress in the near term, provided the latter is done in a manner that reasonably transparent and that allows anybody who has useful input to offer can do so.

I should mention how I anticipate this will fold into ISO process for OFF. After there's been some public review (by whatever means), proposed changes for OFF will be circulated on the MPEG-OTSpec list, which is how the formal process for ISO would be initiated. ISO has certain policies around amendments and timelines that somewhat limit flexibility. For that reason, if there were to be an OT 1.8.4 update, there probably would _not_ be a corresponding amendment to the OFF standard. Rather, any OFF amendment would be held to take the additional changes that would go into OT 1.9, notably COLR enhancements. Vlad can provide more info on ISO process if needed.

In the big scheme, this is a small step, but I hope it's generally seen as a positive step nonetheless.


Peter Constable
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