https://issues.apache.org/bugzilla/show_bug.cgi?id=51639

--- Comment #13 from Vincent Hennebert <vhenneb...@gmail.com> 2011-10-12 
18:41:50 UTC ---
(In reply to comment #10)
<snip/>
> I don't think Aleksev was talking about making glue into boxes he was
> simply suggesting giving them a height (alignmentContext). This is 
> completely outside of the Knuth algorithm and has nothing to do with it. 
> This information is not currently used by the Knuth algorithm and there
> is no proposal here I can see to make the algorithm use it. Attaching
> non Knuth algorithm related information to the Knuth elements is simply
> a convenient way to hold on to some stuff required for line building in
> this case. 
> It's too long ago since I wrote this code for me to assess if the 
> proposal is in compliance with the FO spec but I can't see it being
> 'contrary to the Knuth algorithm' as the data we are talking about is 
> not being used by it and its presence or absence will not change the 
> outcome of the algorithm.

I would agree with that. Knuth elements are one-dimensional only, and in the
present case this dimension applies to the inline-progression-direction. That
is, for Western scripts and the default settings, the line width.

What we are talking about here is the line height, and as described in Section
4.6, "Inline-areas" of the XSL-FO 1.1 Recommendation, "An inline-area with
inline-area children has a content-rectangle which extends from its dominant
baseline [...] by its text-depth in the block-progression-direction, and in the
opposite direction by its text-altitude".

So even if an fo:inline only contains white space characters, it would still
have a height calculated from the font-size that applies to it.

My concern with adding an AlignmentContext to KnuthGlue elements is that it may
cause regressions regarding line stacking in some cases. I don't know this area
of the code very well so cannot predict all the implications of such a change.
That said, it's just a matter of increasing the test coverage and
experimenting.

Vincent

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