[MPEG-OTSPEC] 回复: [EXTERNAL] Re: Defining the text shaping working group’s scope

Renzhi Li Renzhi.Li at microsoft.com
Wed Jul 29 23:53:57 CEST 2020

Agree with John. As an addition, font-fallback, and its interaction with segmentation should also be added into the list.
·¢¼þÈË: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at> ´ú±í John Hudson <john at tiro.ca>
·¢ËÍʱ¼ä: 2020Äê7ÔÂ29ÈÕ 10:15
ÊÕ¼þÈË: mpeg-otspec at lists.aau.at <mpeg-otspec at lists.aau.at>
Ö÷Ìâ: [EXTERNAL] Re: [MPEG-OTSPEC] Defining the text shaping working group¡¯s scope

In terms of defining scope, I would employ a broad view of typographic text display. There are intersections and mutual dependencies to be mapped with text encoding and text interaction (input and editing), but I think a natural scope can be defined in terms of the space where font interaction is necessary to achieve overall layout and display of text, i.e. everywhere from script segmentation to justification.

That's the scope I suggested in looking 'beyond shaping' in my IUC39 presentation:
To the aspects discussed there, I would add text block orientation, i.e. layout directionality as distinct from character and string directionality.


Thank you Liang and Simon for starting the discussion!

Since we are going to embark on the exploration activity to determine the scope of this future work, it is extremely important to identify what relevant information is currently missing [that affects interoperability of fonts and implementations] and if it needs to be specified as a formal standard. It is also important to determine who currently possesses the relevant knowledge and experience, and is willing to contribute to this important work.

I also agree with you that it is very valuable to identify all related documentation, but we also need to be aware of its current status (public / opensource / proprietary / copyrights, etc.) Knowing what we have as a starting point (such as e.g. USE document: https://docs.microsoft.com/en-us/typography/script-development/use<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.microsoft.com%2Fen-us%2Ftypography%2Fscript-development%2Fuse&data=02%7C01%7CRenzhi.Li%40microsoft.com%7C5a74f15f53cd487484af08d833e2f9eb%7C72f988bf86f141af91ab2d7cd011db47%7C0%7C0%7C637316398130298355&sdata=4qeZmtVOc7NV9nf7ZP%2Bmhu%2Fu4GeIysPAyJLSqwm6dLk%3D&reserved=0> and all other resources Liang has mentioned) and whether any existing / prior documentation could be contributed for us to use will not only give us a head start, but also helps come quickly to a decision on whether we need to consider publishing formal script-specific text layout specifications, or if it may be more appropriate to publish it as OFF/OpenType implementation guidelines, or both.

All these components ¨C the information about what we have to start with, who can contribute to this development [and whether they are willing to do so], and what we believe the outcome of this work should be ¨C will help us greatly to decide what organization (Unicode Consortium and this ISO WG were initially named for consideration) would be best suitable to be selected as the venue for this future work.

Thank you,


From: mpeg-otspec <mpeg-otspec-bounces at lists.aau.at><mailto:mpeg-otspec-bounces at lists.aau.at> On Behalf Of ?? Liang Hai
Sent: Wednesday, July 29, 2020 10:35 AM
To: mpeg-otspec at lists.aau.at<mailto:mpeg-otspec at lists.aau.at>
Subject: [MPEG-OTSPEC] Defining the text shaping working group¡¯s scope

(If this topic confuses you, see the appended background introduction.)

In order to figure out the scope we care about, how about we start with maintaining a list of existing projects that are intended to complement the OT spec (and its semi-standard specs such as the USE spec)?

In terms of my personal concerns, one of the most important projects today is this documentation by Nate Willis, et al, which is focused on documenting how OTL should actually be implemented for each complex script, so developers can actually implement compatible shapers:

Documentation of OpenType shaping behavior


On the other hand, my main personal interest is about clarifying how Unicode encoded complex scripts (especially the Indic ones) should be implemented with OTL fonts. (Note the difference from Nate¡¯s project, which is about how to shape texts using these fonts.)

I believe we need to document a reference interface between orthographical correctness and typographical concerns. The whole process from Unicode text up to this interface can be vetted by experts (especially for compatibility and reasonable fallback behavior) and automated by tooling, while font producers are left with a straightforward glyph set to fill. This will greatly improve reliability of complex scripts¡¯ fonts, and also remove the unreasonable obstacle that prevents native users to implement their own scripts in fonts. Some knowledge collected during this effort should even be incorporated into the Unicode Standard, if it¡¯s relevant and the community can achieve an agreement on it.

The current early draft is still very sketchy, but I expect to significantly update it and transform it into a tutorial-based document (because concrete instructions will be much easier to read) in a couple of months:

Indic text shaping for type designers


Áºº£ Liang Hai


Some context for subscribers of this mailing list who didn¡¯t participate in yesterday¡¯s meeting:

There¡¯s a collective effort to seek a clear path forward for improving the whole text shaping industry (including the font formats)¡¯s situation. Yesterday there was the first meeting, and the next meeting (open to all) is scheduled for four weeks later (25 Aug, 13:30¨C14:50 UTC-4). The following document contains yesterday¡¯s meeting notes:

Text Shaping Working Group (working title)


By the end of the meeting we decided this list could be a temporary home for our discussions because of the significant overlap of interest. I hope we¡¯re not spamming you guys.

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John Hudson
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