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Re: TextAlign002 and use of textAlign on span elements

From: John Birch <john.birch@screen.subtitling.com>
Date: Thu, 11 Dec 2008 08:16:24 -0000
Message-ID: <4476B296B92A4741A49B0BD01759070099FCA3@sss-uk-ex-02.screen.subtitling.local>
To: <gadams@xfsi.com>, <plh@w3.org>, <public-tt@w3.org>
Thanks Glen,
I wasn't seeking to introduce new reqs. :-) 
If a p element does not necessarily incur crlf behaviour then what I need could presumably be achieved using two p elements in par with different alignment style attributes 'drawing' into the same region?

Regards
John
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----- Original Message -----
From: Glenn A. Adams <gadams@xfsi.com>
To: John Birch; Philippe Le Hegaret <plh@w3.org>; Public TTWG List <public-tt@w3.org>
Sent: Thu Dec 11 04:08:51 2008
Subject: Re: TextAlign002 and use of textAlign on span elements


Inline below.

On 12/11/08 7:05 AM, "John Birch" <john.birch@screen.subtitling.com> wrote:



	One aspect of broadcast subtitling requirements is multiple text alignments within a single displayed line... I.e left and right aligned text on the same 'displayed' line... While I realise this can be achieved using multiple overlapping regions with different alignment styles that's not an ideal solution...
	
	

This behavior doesn’t really work with the inline packing formatting model which is used by DFXP (as based on XSL). The box model of CSS also does not support this. So it is very unlikely we will do so in DFXP. This would also be a new requirement, which we are really not entertaining at this time, particularly since  there is already a solution in DFXP to support this indirectly (as you note). I think you should avoid modeling such behavior on the basis of the notion of having a single line.

What you are calling a single line is actually much more complex. In XSL it could be expressd as a table row with multiple cells (without borders) with each cell having different text alignments on their internal block content, something like:

<fo:block>
  <fo:table border=”none”>
    <fo:table-body border=”none”>
      <fo:table-row border=”none”>
        <fo:table-cell inline-progression-dimension=”50%” border=”none”>
          <fo:block text-align=”left”>
            <fo:inline>LEFT ALIGNED</fo:inline>
          </fo:block>
        </fo:table-cell>
       <fo:table-cell inline-progression-dimension=”50%” border=”none”>
          <fo:block text-align=”right”>
            <fo:inline>RIGHT ALIGNED</fo:inline>
          </fo:block>
        </fo:table-cell>
      </fo:table-row>
    </fo:table-body>
  </fo:table>
</fo:block>

Of course, DFXP does not support tables, and it would add considerable complexity to do so now.


	
	Does a p element imply a crlf?
	


If you are asking whether an empty <p/> element would cause the insertion of an empty block (line) area, then the answer is no. This is not implied by DFXP’s presentation processing semantics. However, you could achieve this by using any of the following examples (and others):

(1) <p><br/></p>
(2) <p xml:space=”preserve”>&#x000A;</p>
(3) <p xml:space=”preserve”>&#x0020;</p>

All of these result in the generation of a single block (line) area which height is determined by applicable font* and lineHeight properties. The first of these three examples would be preferable.

Glenn





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Received on Thursday, 11 December 2008 08:17:07 GMT

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