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Re: Line Breaking Properties and the inline box model

From: Ian Hickson <ian@hixie.ch>
Date: Tue, 1 Nov 2005 21:43:05 +0000 (UTC)
To: Anne van Kesteren <annevk@opera.com>
Cc: www-style@w3.org
Message-ID: <Pine.LNX.4.62.0511012122020.9929@dhalsim.dreamhost.com>

On Tue, 1 Nov 2005, Anne van Kesteren wrote:
> 
> On Tue, 01 Nov 2005 18:58:56 +0100, Ian Hickson <ian@hixie.ch> wrote:
> > > Several people inside Opera wonder how CSS interacts with the Line
> > > Breaking Properties standard[1].
> > > 
> > > [1]<http://www.unicode.org/reports/tr14/>
> > 
> > It doesn't, in particular. User agents are free to use whatever they like
> > for line breaking.
> 
> Is there any chance future CSS specification become more specific on 
> this?

No. It does not affect interoperability in a particularly important way, 
and so is something we expect user agents to compete over.


> > > Especially as it defines some very specific rules for displaying 
> > > certain text, but does not say how this interacts with CSS. If you 
> > > have:
> > > 
> > >  <span>ABC </span>]
> > > 
> > > ...and the SPAN element has a 'border'. Is line-breaking allowed? I 
> > > assume it is allowed when the SPAN is set to 'display:block'.
> > 
> > I do not understand this question. Is line-breaking allowed where?
> 
> Currently Unicode TR #14 says that no line-breaking is allowed before 
> the "]" character even if that character is a space. (You may have a 
> line-break after a space but the rule for "]" prevents that.)
> 
> Is it likely that the behavior described in Unicode TR #14 becomes 
> mandatory one day or will be clarified by a CSS specification (as it is 
> also about presentation). And if so, in what direction would that go.

It is not likely that CSS will ever specify this. Implementations are 
encouraged to find better ways of doing line breaking.

For example, in the following text:

   <p>...and then there is a word, urn:it is an acronym that means 
   something. You can find out what it means by going to the Web site
   indicated by the address urn:it or by using a book.</p>

...an optimal implementation would know that it should line break after 
the first colon (since that is a colon separating two parts of a sentence, 
as in "a word, urn: it is an acronym"), but not after the second (since 
that is part of a URI, "urn:it").

Similarly, in:

   <p>[ Hello World ]</p>

...the optimal UA probably would avoid breaking after the [ and before the 
]; but in this sentence that you are reading now, the optimal UA would 
have no problem with putting a line break between the words "the" and "]", 
because there it is just another word, not paired up with the other [.

HTH,
-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Tuesday, 1 November 2005 21:43:18 GMT

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