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Re: from-page-master-region()

From: Peter B. West <lists@pbw.id.au>
Date: Wed, 02 Feb 2005 13:01:21 +1000
Message-ID: <42004281.9030905@pbw.id.au>
To: xsl-editors <xsl-editors@w3.org>

The editors,

In a previous message, I made some comments on the possibility of
"dynamic inheritance" of properties from the layout-master-set.

There exists already a model for "dynamic" inheritance, i.e.,
fo:marker/fo:retrieve-marker, and the newly proposed
fo:retrieve-table-marker.  It has been the cause of a great deal of
anguish, for me and other FOP developers at least, but most XSL
developers have found a solution to the problem.  What if a subset of
traits were defined to inherit directly from properties on their area's
controlling simple-page-master?  This set would not be extensive, so the
inheritance tree would not be particularly cpu or memory intensive.

This would entail either a) a change to the manner of inheriting
existing properties, or b) the definition of new properties whose
inheritance and usage characteristics are so defined.  Method b) brings
with it the necessity to arbitrate between. e.g., the existing
"writing-mode" and the new, say, "area-writing-mode".  I lean to using
a) in association with a switch that determines whether the old or new
mode is in effect.  The switch would default to 1.0 behaviour,
preserving the layout of existing fo: stylesheets.  It seems to me that
such a switch could be specified in fo:declarations.

Please consider some further speculation.

In developing the properties resolution for project Folio
<http://defoe.sourceforge.net/folio/>, Section 3 of the Recommendation
has been noted carefully.  Properties are resolved in the context of
areas generated by the immediate ancestor FOs of any given FO.  Taking
this approach, it makes sense to generate template pages from the
simple-page-masters in the layout-master-set.  The properties discovered
in descending the FO tree are resolved against these template pages,
which can be cloned as required.

In some previous communications from the WG, layout-based formatting has
been mentioned as a possible future development.  Inheriting from the
simple-page-masters could be a step in this direction.  If a switching
mechanism, as mentioned above, in the earlier message, were implemented
as a means of preserving backward compatiblity, static-content and flow
would inherit directly from the controlling simple-page-master.  Only
simple-page-masters would be in the inheritance ancestry.
Simple-page-master property resolution is "stand-alone"; it proceeds
independently of any use to which particular simple-page-masters are
put.  Note that I am thinking here of switching inheritance in toto from
page-sequence to simple-page-master.

Resolving inheritance through page-sequence-masters is do-able, along
the lines (again) of transplanting marker subtrees into the
static-content.  However, any properties defined directly on
simple-page-masters will take precedence, so it would seem to be of very
limited utility.

If the approach of layout inheritance were taken, it would be possible
to forgo not only from-page-master-region(), but page-sequence-wrapper.
  Much of the functionality of page-sequence-wrapper would be achieved
through simple-page-masters.  The relative benefit of each of approach
(s-p-m inheritance vs page-sequence-wrapper) would need to be assessed
against a range of commonly used document structures.

Peter West
Received on Wednesday, 2 February 2005 03:01:28 UTC

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