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Re: Need to clarify the effects of bidi paragraph breaks

From: fantasai <fantasai.lists@inkedblade.net>
Date: Wed, 23 Feb 2011 23:42:24 -0800
Message-ID: <4D660BE0.1040505@inkedblade.net>
To: "Aharon (Vladimir) Lanin" <aharon@google.com>
CC: W3C style mailing list <www-style@w3.org>, "public-i18n-bidi@w3.org" <public-i18n-bidi@w3.org>
On 12/15/2010 02:11 PM, Aharon (Vladimir) Lanin wrote:
> Currently, the CSS Writing Modes Module Level 3 spec on text direction
> <http://dev.w3.org/csswg/css3-writing-modes/#text-direction> states:
>
> I think that these parts of the spec needs to be tweaked in several respects:
>
> 1. There is no reason to mention rule P1 when describing how unicode-bidi:plaintext affects the base directionality of each
> paragraph. P1 deals with how the text is split up into paragraphs, not with the direction of each paragraph, and applies to
> all content, regardless of unicode-bidi:plaintext.

Hm, good point. Fixed.

> 2. I think it would improve clarity to mention the unicode-bidi:plaintext exception when first describing how the paragraph
> embedding level is set (first quote above). Thus, the last sentence of the first quote should read:
>
> "The paragraph embedding level is set according to the value of the ‘direction’ property of the containing block, unless the
> containing block element has unicode-bidi:plaintext, in which case it is set according to the heuristic given in steps P2 and
> P3 of the Unicode algorithm."

I am.. less sure of this. I prefer to have unicode-bidi: plaintext to
be described as an exception to the general rule than to have it be
described as some kind of determining switch. Anyway, I've added
some clarifying wording.

> 3. We must probably explicitly define the effect of a paragraph break
> [when it splits an embedding inline]
> The overall direction of both paragraphs is ltr (P2 and P3 are overridden),
> and since the paragraph break resets all embedding levels, the [PDF] is
> orphaned, and the question mark winds up to the right of "EB OT TON RO".

Good point. I've added text to this effect.

> Does a line break does result in anonymous boxes?

No, just more line boxes. :)

> 4. When the path from the containing block element to the paragraph break includes an element with unicode-bidi:isolate, there
> is no reason to go back all the way to the containing block element to get the new paragraph's base direction and the
> embeddings to be reconstituted at its start. Instead of referring to the containing block element, the spec should be
> referring to the closest unicode-bidi:isolate ancestor or containing block element, whichever is closer.

Good point. I've updated the spec for this, too.

~fantasai
Received on Thursday, 24 February 2011 07:44:04 GMT

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