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From Vincent Hennebert <vhenneb...@gmail.com>
Subject Re: Funding for Float support in FOP?
Date Fri, 14 Feb 2014 14:05:53 GMT
On 13/02/14 18:29, Aaron W. Hsu wrote:
> Chris Bowditch <bowditch_chris@hotmail.com> writes:
>
>> Assuming the prototype can be finished within say another 12 months,
>> it would then take several further man years to port the rest of FOP's
>> functionality onto the prototype. We estimate the implementation cost
>> would be in the range of several hundred thousand GBP :-o
>>
>> This is why fo:float has not yet been implemented. Sorry to be the
>> bearer of bad news.
>
> Thanks for the information. It's not bad news for me at all, but more
> just a data point. I wanted to see an actual estimate of just how
> difficult it is to add float support to FOP, and your estimate is quite
> helpful. I haven't read the specification myself, so I have no intuition
> about how crazy floats are, and it doesn't surprise me that a feature
> like this could take years to implement.

On top of this, an implementation of the standard fo:float element
wouldn’t allow you to achieve the Sigplan layout you mentioned in this
other thread:
http://mail-archives.apache.org/mod_mbox/xmlgraphics-fop-users/201402.mbox/%3C87ob2mkv58.fsf%40sacrideo.us%3E

You can’t use side-float because you don’t know in which paragraph to
put the anchor such that it would end up at the bottom of the first
column. You can’t use before-float because it would flow up to the top
of the page. Neither can you use a footnote, because it would take up
the whole width of the page, so it would push both columns up. Plus in
some cases it might be deferred to the next page.

So to my knowledge your requirement is not achievable in plain XSL-FO.

All that said, implementing before-floats should be doable in the
current layout engine without too much effort. There’s a branch in
Subversion with the start of an implementation that would need to be
brought up-to-date, debugged, completed and cleaned up. I can’t say much
more without studying the problem in more details, but we are talking in
terms of weeks rather than months or years.

Implementing side-floats is IMO not achievable without undertaking
a major redesign of the layout engine.


HTH,
Vincent

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