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From Manuel Mall ...@arcus.com.au>
Subject RE: Undesirable line breaks
Date Mon, 15 Sep 2008 14:38:29 GMT


> -----Original Message-----
> From: Amick, Eric [mailto:Eric.Amick@mail.house.gov]
> Sent: Monday, 15 September 2008 8:39 PM
> To: fop-users@xmlgraphics.apache.org
> Subject: RE: Undesirable line breaks
> 
> >> FOP is currently producing undesired line breaks.  I'm having this
> >> problem with FOP 0.95 and svn trunk.
> >>
> >> The problem is that FOP thinks that it's appropriate to split "Gtk+"
> >> across two lines.
> 
> >> I can't think of any other text layout engine that would consider
> that
> >> to be a legitimate place to insert a break.
> 
> >At what point? I assume it's right before the '+', correct?
> 
> >If the layout engine uses Unicode TR#14 as reference to determine the
> line-breaks,
> >then a break between 'k' and '+' would be allowed. '+'
> >belongs to the class of Numeric Prefix characters (PR), and as such
> allows a break before
> >but not a break after. (see: http://www.unicode/
> >reports/tr14/#DescriptionOfProperties)
> 
> The following description of the numeric prefix characters from the
> Unicode standard suggests it shouldn't be breaking there:
> 
> Characters that usually precede a numerical expression may not be
> separated from following numeric characters or following opening
> characters, even if a space character intervenes. For example, there is
> no break opportunity in "$ (100.00)".
> 
> Many currency signs can appear on both sides, or even the middle, of a
> numeric expression. Therefore the line breaking algorithm, by default,
> does not break between PR [numeric prefix] and numbers or *letters* on
> either side. [emphasis mine]
> 

Correct, that is what the text says. But when you look at the formal
definition there is a rule saying 'PR x AL' (in LB 24), but there is no rule
AL x PR in LB 25 (or anywhere else AFAICT). The same is true for the pair
table model of the rules which says AL followed by PR is a direct break
opportunity while PR followed by AL is an indirect break opportunity.

> 
> Eric Amick
> Legislative Computer Systems
> Office of the Clerk
> 

Manuel

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