Column-balancing

["Puppala, Kumar (LNG-DAY)" <ku...@lexisnexis.com>]

Hello:
  I am trying to fix the column balancing issue in fop 0.20.5 in my local
copy. The method I am looking at is resetSpanArea() in
BodyAreaContainer.java. There is a fixed value that we are adding in this
function, which is referred to as heuristic safety factor. The current value
used is (2*15600). Changing this value is having both positive and negative
effects on the layout. Does anyone know what this value is supposed to
accomplish? Maybe knowing more about this might help me fixing my column
balancing issue. 

Thanks,
Kumar Puppala



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RE: Column-balancing

[Victor Mote <vi...@outfitr.com>]

Puppala, Kumar wrote:

>   I am trying to fix the column balancing issue in fop 0.20.5 
> in my local copy. The method I am looking at is 
> resetSpanArea() in BodyAreaContainer.java. There is a fixed 
> value that we are adding in this function, which is referred 
> to as heuristic safety factor. The current value used is 
> (2*15600). Changing this value is having both positive and 
> negative effects on the layout. Does anyone know what this 
> value is supposed to accomplish? Maybe knowing more about 
> this might help me fixing my column balancing issue. 

I'm guessing that nobody knows that answer to your question. I don't know
either, but my guess is that the author was trying to leave room for
variations in line height that might exist, and to deal with rounding. The
author noted that the algorithm is "primitive". IMO the algorithm needs to
be totally rewritten. To do better, you will need to look at the height of
each line and test "breaks" that minimize the variation in columns heights.

BTW, AFAIK, FOP developers are no longer applying patches to 0.20.5 for any
reason, which means that you will be maintaining custom code on your own.
You may get a better return on your investment by working on one of the
rewrite efforts. The FOP redesign is one, and the others are graciously
listed by FOP here:
http://xml.apache.org/fop/resources.html#products-other

Victor Mote


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