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RE: [css3-writing-modes] vertical orientation and UTR50

From: Koji Ishii <kojiishi@gluesoft.co.jp>
Date: Fri, 29 Jun 2012 05:43:11 -0400
To: John Daggett <jdaggett@mozilla.com>
CC: www-style list <www-style@w3.org>
Message-ID: <A592E245B36A8949BDB0A302B375FB4E0D5E51CF73@MAILR001.mail.lan>
> Then we should request another UTR50 draft containing the changes and use that.  I
> am very strongly against defining something that looks like a delta on top of the UTR50
> proposal.  There is absolutely no reason to rush to publish something based on
> preliminary edits that have not necessarily converged to their final form.

First, we resolved to put our own table in the writing-modes spec[1]:

> - RESOLVED: put our own table of behaviors for mixed-right and upright
>               values in the writing-modes spec until UTR50 stabilizes

Second. It's very unfortunate but there's a reason. The next draft has to wait for the next UTC conference at 30th Jul. If we asked vendors and publishers to wait for it, they said they'll go with the current WebKit implementation. I tried draft #5 too, but it didn't work either because it has too critical errors to use in CJK.

It is our goal to avoid spreading files that depends on a specific implementation, I hope you agree with this, and I think this is the only way to avoid it.

> I don't understand what you mean by "derived property" here.  The existing text is
> non-normative and does not sufficiently explain how the values of the SVO/MVO map
> to the actual placement of glyphs in vertical text runs.

I meant "derived property" as defined by UAX#44[2].

The normative part of 5.1.1. Vertical Orientations[3] defines two derived properties, and defines how UA must render using them. I think this part is clear and sufficient for both implementers and authors. Are we agree on this?

You're right that how to derive is non-normative. I intentionally did so because of the instability of the UTR50. We're still not sure proposed values like IR/IU will make it or not. UTR50 may introduce more values or properties to support Old Turkic[4]. We will need to edit this part every time UTR50 changes definitions. I think it's better to make it non-normative until UTR50 stabilize further.

> The use of pseudo-code is part
> of the problem, the use of symbols with unclear definitions is another.  I think the
> replacement text I proposed solves this and is clearer:
>   For the 'mixed-right' and 'upright' property values, vertical orientation is
>   defined in terms of the corresponding Unicode property value, MVO
>   and SVO respectively. If the orientation value is "R" then the glyph
>   is rotated right.  If the orientation value is "U", "T", "Tu", or
>   "Tr" then the glyph is displayed upright.  The one exception is for
>   scripts like Mongolian for which special handling is required for
>   the stacked case due to the vertical-only nature of the underlying
>   script.
> I think with the last sentence and a discussion of Mongolian/Phags-pa in UTR50 is
> sufficient for interoperability, I don't see the need for a verbose explanation of SVO
> handling for these scripts.

Ok, I will change the code to the text late tonight. It was too complex for me to write in English, your proposed wordings really helps me. Thank you about that.

[1] http://lists.w3.org/Archives/Public/www-style/2012May/0541.html

[2] http://www.unicode.org/reports/tr44/#Simple_Derived

[3] http://dev.w3.org/csswg/css3-writing-modes/#vertical-orientations

[4] http://www.unicode.org/forum/viewtopic.php?f=35&t=337


Received on Friday, 29 June 2012 09:40:29 UTC

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