Re: Bidi space Q&A

On Sat, 5 Jul 2003, Tex Texin wrote:
>
> "Note that there are two spaces between A and B, and none between B and C.
> This is best avoided by using the natural bidirectionality of characters
> instead of explicit embedding levels."
>
> Can someone explain this to me?

Below, CAPITALS represent hebrew characters and lowercase represents
latin1 characters, as per the UNICODE convention, and [LRE], [RLE], and
[PDF] represent the relevant bidi characters (U+202A to U+202C). The
latter are equivalent to using markup with "dir" attributes or the
'direction' property in CSS. The numbers underneath represent the
embedding levels.

   english [RTL] HEBREW [PDF] english
   11111111     22222222     11111111

...vs:

   english HEBREW english
   1111111122222211111111

Both are given in a context with a block 'direction' of 'ltr'.

The former would render as:

   english  WERBEHenglish
   1111111122222221111111

...while the latter would render as:

   english WERBEH english
   1111111122222211111111

See, e.g.:

   http://www.damowmow.com/playground/demos/bidi/001.html


> I understand that neutral-directionality characters in between strong
> characters inherit their direction. However, with css, direction is
> either ltr, rtl, or inherited.

The CSS directions are equivalent to explicit UNICODE bidi formatting
characters (U+202A to U+202E). See the bidi algorithm for more details on
how direction-neutral characters inherit their direction from the
surrounding characters:

   http://www.unicode.org/reports/tr9/tr9-11.html#Resolving_Neutral_Types


> 3) Just an aside, I think we need to tell the CSS folks to say that
> unicode-bidi has to be normal for their spec to be precise. We didn't
> need to say it because we ruled out CSS from the question.

I don't understand what this means.

Cheers,
-- 
Ian Hickson                                      )\._.,--....,'``.    fL
"meow"                                          /,   _.. \   _\  ;`._ ,.
http://index.hixie.ch/                         `._.-(,_..'--(,_..'`-.;.'

Received on Saturday, 5 July 2003 11:51:05 UTC