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Proposed CR change to default bidi behavior for elements with dir

From: Erika Doyle Navara <Erika.Doyle@microsoft.com>
Date: Thu, 24 Oct 2013 23:34:28 +0000
To: "'public-html@w3.org'" <public-html@w3.org>, "member-i18n-core@w3.org" <member-i18n-core@w3.org>, Richard Ishida <ishida@w3.org>, Addison Phillips <addison@lab126.com>, "Sam Ruby (rubys@intertwingly.net) (rubys@intertwingly.net)" <rubys@intertwingly.net>, Paul Cotton <Paul.Cotton@microsoft.com>
Message-ID: <0108475888e149cdb96139c1342fc3de@BN1PR03MB039.namprd03.prod.outlook.com>
The I18N working group has requested [1] that bug 22326 [2] be addressed in the HTML5 CR timeframe. This bug represents the implementation of the I18N proposal [3] to change the bidi semantics of the dir attribute to imply isolation rather than embedding. 
 
The technical discussion so far has taken place on the WHATWG cloned bug [4], but here is a summary of the pro/con arguments (Richard/I18N members, please correct if I have missed or misrepresented anything):

Pro (make dir="" imply unicode-bidi:isolate)
==========================================
- HTML5 is consistent with  Unicode 6.3 spec (and other specs, like CSS3 Writing Modes) in making isolation the default for all inline bidi text embeddings

- Bidirectional text is easy and intuitive for web developers to implement correctly, and without needing to know anything about the intricacies of bidi algorithm

- Drives browser implementation to make the web less buggy with bidi issues. Problems with existing legacy pages will be fixed automatically.

- Easy transition period while browsers adopt new behavior (code will work better in browsers with the change, but work the same in browsers without)

- Once a browser supports isolation, it is trivial to implement this change in semantics for dir (simple change to default style sheet)

Con (dir="" continues to imply unicode-bidi:embed)
===========================================
- Currently no implementations yet of this behavior

Rebuttal: IE8-IE10 did a similar (but not identical) change, however, and there was little or no compat fallout, both according to IE bug records and also i18n community

- Default isolation for dir potentially makes the new HTML5 <bdi> element seem redundant.

Rebuttal: <bdi> element is still useful in cases when text of unknown direction is dynamically inserted to a page (because it has new HTML5 dir="auto" value as default, which determines dir at run time). Perhaps we could even re-label <bdi> from "bidi isolate" to "bidi insert".

...given the favorable reasons outweighing the unfavorable, I have implemented this change in the HTML5.1 Nightly draft, and believe it merits porting over to the HTML5 CR draft as well:

	https://github.com/w3c/html/commit/efbf692e44fa3e6b9d66a0823fc2133ff1d18f1e 

Please reply with any objections. Otherwise, I will port this change to the CR draft within a couple weeks (11/6).

Thank you,
Erika

[1] http://lists.w3.org/Archives/Public/public-html-admin/2013Oct/0015.html 
[2] https://www.w3.org/Bugs/Public/show_bug.cgi?id=22326
[3] http://www.w3.org/International/wiki/Html-bidi-isolation#Proposal_A:_change_the_dir_semantics 
[4] https://www.w3.org/Bugs/Public/show_bug.cgi?id=23260 
Received on Thursday, 24 October 2013 23:35:43 UTC

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