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From "Barry Whiting" <barry_whit...@londonmarketing.com>
Subject RE: Flow-Map
Date Tue, 17 Feb 2009 10:54:06 GMT
Hi Jeremias

Thank you very much for getting back to me so quick.

Sorry if my terminology is incorrect but hopefully I will learn this
quickly here.

> "adding the xml to the tree".
> Does that mean you managed to get the FO tree objects?

Yeap that's exactly how far I have got.  I am know reading the
documentation to get a full understanding of the layout managers I
didn't realise how complicated this would be so know I do and realise
the docs are very important to me right now.

Thanks for the encouragement.


-----Original Message-----
From: Jeremias Maerki [mailto:dev@jeremias-maerki.ch] 
Sent: 16 February 2009 22:42
To: fop-dev@xmlgraphics.apache.org
Subject: Re: Flow-Map

Hi Barry,

I'm not sure I understand what you mean by "adding the xml to the tree".
Does that mean you managed to get the FO tree objects built from the
corresponding FO elements? The stuff in ElementMapping, the necessary FO
tree classes, the makers? How far did you really get?

Anyway, I remembered that someone already started to work towards flow
maps a couple of years ago and a quick search revealed this:
It seems this was never properly resolved but maybe this could help with
your task.

Anyway, building up the FO tree structure is probably the easy part in
all this. When it gets to area production (i.e. the layout managers), it
gets more complicated. You have not chosen an easy task (just to be
honest). I haven't studied flow maps in detail, yet, so I'm not sure
about all the details but I suspect this will have an impact on the page
production level (i.e. PageSequenceLayoutManager). At the moment,
there's just the region-body which drives page production with the
static content from the side regions around it. From what I know of flow
maps, you can have multiple flows on one page [1]. What that means to
the whole page breaking process, I can't tell at the moment. One part of
your task is certainly to learn how the layout engine works: starting
with the Knuth approach (info to be found on the FOP Wiki), continuing
with stuff like page-position, marker implications, multi-column layout
and stuff like that.

Then, I hope Vincent will also speak up because this may need to be
coordinated with him as he's working on improving page breaking. I don't
know if he's already taken flow maps into the picture.

I don't want to discourage you, just be prepared for a steep learning
curve. It's great to see new blood taking up the challenge. Getting the
FO tree right is certainly a good first step. It may make sense to work
on this incrementally, i.e. post a first patch to update the FO tree and
then go on to work on the layout engine. I don't expect any significant
changes in and after the area tree at least.

Good luck! I'll try to help where I can but lately, Vincent is certainly
closer to all the layout stuff.

[1] http://www.w3.org/TR/xsl11/#d0e7202

On 16.02.2009 18:57:56 Barry Whiting wrote:
> Hi
> Please understand I'm not a main java developer but I have taken the
> responsibility of fop in our workplace as I usually write the xsltfo.
> I am trying to implement flow maps inside and have so far found no
> problems with adding the xml to the tree but that's where I get stuck.

> Could anybody point me in the right direction on how to know get these
> Regions added to the renderer with the correct content for the flows
> please?
> Kind regards
> Barry

Jeremias Maerki

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