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Re: How can I dynmaically use page-number?

From: Christopher R. Maden <crism@maden.org>
Date: Thu, 04 Oct 2001 23:06:48 -0700
Message-Id: <5.1.0.14.0.20011004230001.00a72e00@mail.maden.org>
To: www-xsl-fo@w3.org
At 10:18 4-10-2001, Dave Pawson wrote:
>At 11:40 04/10/2001 -0400, Clute, Andrew wrote:
>
>>Ideally, I would like to do something like this:
>>
>><fo:external-graphic height="1.2in" width=".35in" 
>>src="<http://localhost:7001/barcode?code=04>http://localhost:7001/barcode?code=04<fo:page-number/>&amp;degree=270&amp;caption=t"/>
>
>The page number isn't determined until the layout engine gets hold of it?
>So that's the time it's needed.
>
>I think its another one for the wg Max?

This is a tricky one that comes down to a basic architectural issue.  There 
are essentially two kinds of batch formatters: tightly-coupled and 
loosely-coupled.  In a tightly-coupled system, like TeX, you can do things 
like measure the typeset width of an input string and decide to format the 
page as one column or two based on that.  In a loosely-coupled system, each 
step of typesetting is independent, with no circularity.  That makes 
implementation a little simpler, but means that there are some things - 
like the input depending on the current page number - that you can't do.

Full DSSSL required a tightly-coupled system.  The XSL WG, for better or 
for worse, decided to go with a design that allowed a loosely-coupled 
architecture for XSL; this decision was strengthened by the decision to 
separate out XSLT as its own Recommendation.

This particular example could be done in a loosely-coupled system as a 
special case, but as a general mechanism, getting access to the page number 
in the expression language would introduce the kind of tight coupling that 
XSL has avoided so far.

-Chris
-- 
Christopher R. Maden, Principal Consultant, HMM Consulting Int'l, Inc.
DTDs/schemas - conversion - ebooks - publishing - Web - B2B - training
<URL: http://www.hmmci.com/ > <URL: http://crism.maden.org/consulting/ >
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Received on Friday, 5 October 2001 02:08:22 GMT

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