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From Luca Furini <lfur...@cs.unibo.it>
Subject Re: Error message: "Should be first"
Date Tue, 11 Jul 2006 08:33:51 GMT
Jeremias Maerki wrote:

> One of my clients reported to me that he gets a "Should be first" error
> message on the log. This happens in (Page)BreakingAlgorithm.removeNode().
> I get the impression that the code there is not finished rather than
> that is a real error condition. I'll try to extend removeNode() so it
> really removes the disabled node.

That's quite strange ...

The reason why the to-be-removed node should be the first one is this:

active nodes are ordered by line (page) number and by index of the element 
where the feasible break can happen, so, for example, a node representing 
a break for page 13 at element #150 is (or at least it should be) before a 
break for page 13 at element #152;

a node is removed when it is too far from the current feasible break being 
evaluated (or, in other words, from the node and the current position 
there is too much content to be placed in a single line / page), so in 
"normal" situations nodes are removed in order: for example, if we are 
evaluating a break at element #180, and we are too far from the node 
representing the break for page 13 at element #152, we will have already 
removed the node representing a break at page 13 element #150 (as it will 
be farther from the current element);

this could be no more true when there are footnotes: for example the break 
at element #152 could represent a page where we have placed one more 
"normal" line in page 13, but fewer footnote lines with regard to the 
break at element #150, so the node coming first allows to place more 
content than the following one, and we could need to remove the node at 
#152 *before* the one at element #150

However, this does not explain why this warning shows in what appears to 
be a very simple document.

I'm going to have a closer look ...

Regards
     Luca

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