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Re: Alignment of paragraphs with unicode-bidi: plaintext [css3-text] [css3-writing-modes]

From: fantasai <fantasai.lists@inkedblade.net>
Date: Wed, 25 Apr 2012 16:34:40 -0700
Message-ID: <4F988A10.50400@inkedblade.net>
To: public-i18n-bidi@w3.org
CC: "www-style@w3.org" <www-style@w3.org>
On 04/15/2012 06:34 AM, Aharon (Vladimir) Lanin wrote:
>>  Ok, I have
>>      An element immediately contains a bidi paragraph if the element itself,
>>      but none of its descendants, is a block container or bidi-isolating
>>      inline that contains the entire bidi paragraph.
>
> It is not immediately obvious that the "that contains the entire bidi paragraph"
> clause applies to both the "block container" and "bidi-isolating inline" cases.
> It may be a little clearer if it is phrased as:
>
> An element immediately contains a bidi paragraph if the element itself, but
> none of its descendants, both contains the entire bidi paragraph and is either
> a block container or bidi-isolating inline.

Ok, fixed.

>> > I am not sure why you use the term "inline base direction"
>> > (of a bidi paragraph) instead of just "base direction".
>
>>  See http://dev.w3.org/csswg/css3-writing-modes/#text-flow
>>  It's to contrast it with the block flow direction.
>
> Writing Modes defines inline base direction as a property of a writing mode (along with block flow direction). The definition
> being proposed for Text, on the other hand, is talking about a property of a bidi paragraph. An "inline base direction"
> property has never been defined for paragraphs. What UAX #9 does define for paragraphs is "paragraph embedding level" and then
> "paragraph direction [...] in some contexts [...] also known as the base direction".

I think it's reasonable to conclude that the "inline base direction" in CSS
and the "base direction" in UAX9 are the same thing.

If you feel it's important to drop "inline", I'll raise an issue with the CSSWG.
But I think it's better to keep it, as there is also a block direction to consider.

> Writing Modes itself, when talking about
> a property of a paragraph, uses the terms "paragraph embedding level" and "base directionality", but not "inline base direction".

The use of "paragraph embedding level" is explicitly hooking into the
terminology used in UAX9, so that can't change. I've looked over the
other cases and tried to make them consistent, though; older versions
of the draft used "base directionality" in place of "inline base direction".

>  In fact, perhaps Text should actually give a precise definition of a line box's inline base direction
> (as we have been discussing here), and then simply say that "the start and end edges of a line box are relative to the line
> box's inline base direction".
> ...
> I think I have a much better idea here: instead of deriving it from the previous bidi paragraph (which is actually
> ill-defined), derive it from the preceding line box (in the same containing block). Thus, this would be:
> ...
>>  Another question: should this definition also affect text-indent?
>
> Yes! This underscores the need for defining the inline base direction of a line box.

Ok, I've made edits to that effect and pushed them here:
   http://dev.w3.org/csswg/css3-text/#bidi-linebox

It's kindof a long complicated section. I'm wondering if there's a better place to put it...

>>  What about hanging-punctuation?
>
> I guess. If I understand correctly, the concept comes from East Asian languages, with which I am not familiar.

It's also used in Western typography, although not quite as formally, I think;
for Western typography there isn't a strong grid, so it's more about approximating
optical alignment.

~fantasai
Received on Wednesday, 25 April 2012 23:35:09 GMT

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