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Re: from-page-master-region() and Re: reference-orientation

From: Grosso, Paul <pgrosso@ptc.com>
Date: Tue, 28 Feb 2006 13:20:32 -0500
Message-ID: <CF83BAA719FD2C439D25CBB1C9D1D302027469A7@HQ-MAIL4.ptcnet.ptc.com>
To: <peter.west@hp.com>, "xsl-editors" <xsl-editors@w3.org>

 
The XSL FO SG discussed this issue again at our recent f2f.

We reconfirmed our position on this issue which is that there 
will be no change to the 1.1 spec in this area.

We understand that there are two ways inheritance could work 
in the FO tree with respect to the properties in the layout-master-set. 
Each of the two ways is necessary to support certain capabilities. 
In scoping XSL 1.0, we decided to restrict ourselves to a single 
simple inheritance model that always follows the structure of the 
formatting object tree (section 5.1.4); that limitation continues 
in XSL 1.1. We have always had plans to allow the other way as part 
of a larger effort to support layout-driven composition requirements, 
but we determined that work to be out of scope for 1.0. The reasons 
we picked the inheritance model we did instead of the other one are: 
(1) we had to choose one for 1.0, and most of the time one wants 
inheritance from the content, and (2) though out of scope for 1.0, 
we knew we would want to do layout-driven formatting at some point, 
and this would require much more capability to "inherit" properties 
in ways other than down the formatting object tree, so we decided 
we'd leave all such capabilities for the future work.

Between 1.0 and 1.1, we realized that the 1.0 wording wasn't clear. 
(For example, we discovered that while RenderX interpreted it the 
way we meant, Antenna House interpreted it differently. Antenna 
House's latest implementation has now been modified to follow the 
clarified interpretation.) This led us to reword this section 
in 1.1 to clarify our original intent. It also led us to add the 
from-page-master-region() function to 1.1 to enable stylesheet 
writers to access writing-mode and reference-orientation from 
the page-master. In a future version of XSL, we plan to extend 
this function to enable it to access other properties from the 
page master and to use this function within expressions.

Paul Grosso
for the XSL FO SG

> -----Original Message-----
> From: xsl-editors-request@w3.org 
> [mailto:xsl-editors-request@w3.org] On Behalf Of Peter B. West
> Sent: Tuesday, 2005 August 09 9:23
> To: xsl-editors
> Subject: Re: from-page-master-region() and Re: reference-orientation
> 
> 
> Peter B. West wrote:
> > Sharon,
> > 
> > My apologies for taking so long to respond.
> > 
> > I did appreciate that the use of the function did not 
> violate lexical
> > (is that an appropriate term?) inheritance.  My concern was with the
> > mooted changes to "6.4.5 fo:page-sequence", under "Trait 
> Derivation".
> > 
> >  'The reference-orientation and writing-mode of the
> >  region-viewport-areas are determined by the values of the
> >  "reference-orientation" and "writing-mode" properties of the
> >  fo:page-sequence.'
> > 
> > Is this change still in play?
> 
> Sharon,
> 
> The answer, as the Last Call makes clear, is "yes".  What a 
> astonishing
> performance by the editors.
> 
> This change purports to be a "clarification."  What it 
> clarifies is that
> in 1.0 (and the initial draft of 1.1), reference-orientation and
> writing-mode defined on elements of fo:simple-page-master 
> subtrees were
> completely inaccessible.  In neither 1.0 or the first draft of 1.1 do
> reference-orientation or writing-mode appear as properties applying to
> fo:page-sequence.  They do, however, appear as properties applying to
> fo:simple-page-master, fo:region-body, fo:region-before,
> fo:region-after, fo:region-start and fo:region-end.  They still do.
> 
> A basic prop of the Recommendation has been the inheritance of
> properties down the FO tree: not, as far as I have ever been able to
> tell, down the "FO tree that holds the content."  For instance, see my
> question
> http://lists.w3.org/Archives/Public/xsl-editors/2005JanMar/0060.html
> substantially unanswered in
> http://lists.w3.org/Archives/Public/xsl-editors/2005AprJun/0014.html
> which refers me to http://www.w3.org/2001/08/28-XSL-PR-DOC , 
> comment 20,
> item 3, a response to a message of 10 Jan 2001, which states, "The
> design approach taken for XSL was to have a simple inheritance model.
> Making this change would obviously introduce an exception to 
> this model. ...
> The consensus of the working group was to not introduce this 
> breaking of
> the inheritance as it is sometimes very useful and in the 
> cases where it
> is not what the stylesheet author wishes it is very easy to make an
> explicit specification ..."
> 
> That, of course, is also the case here.  Should an author be 
> unable, for
> reasons which escape me, to construct sufficient 
> fo:simple-page-masters
> to cover their requirements, and insist on overriding the
> reference-orientation and writing-mode on the 
> fo:simple-page-master they
> just specified for the current fo:page-sequence, there is always the
> option to create a top-level reference-area to contain the contents of
> fo:flow and fo:static-content.
> 
> The simple-page-master subtree has all the tools for specifying
> orientation and mode on every region, and that is the job of the page
> masters.
> 
> However, the editors have chosen discard the simple inheritance
> principle, but only in the fo:layout-master-set subtree, and only with
> respect to reference-orientation and writing-mode.
> 
> My suggestion is to remove most of this "clarification" from 
> the draft,
> along with from-page-master-region (still defined, 
> incidentally, with an
> optional argument which it is an error to use, and other 
> infelicities),
> and to replace that function with the following:
> <q>
> object from-page-sequence()
> The from-page-page-sequence function returns the computed value of the
> property for which the expression is being evaluated.
> 
> In XSL 1.1 this function may only be used as the value of the
> "writing-mode" and "reference-orientation" properties.
> 
> The computed value of the designated property is taken from
> fo:page-sequence ancestor of the formatting object on which 
> the function
> is being applied.  It is an error if the formatting object has no
> fo:page-sequence ancestor.
> </q>
> 
> fo:page-sequence will still need its new adornments of "7.21.3
> reference-orientation" and "7.29.7 writing-mode" among the set of
> properties applying.
> 
> Thanks for your attention.
> Peter
> 
> > Sharon Adler wrote:
> > 
> >>Peter,
> >>
> >>Yes you are correct in that we should not violate our rule to have
> >>inheritance down the  FO tree that holds the content.  We 
> do not believe we
> >>have properties that inherit from the fo:layout-master-set. 
>  Pulling a
> >>value using a property-value function is not inheritance.
> >>
> >>Thanks again for your comments and interest in XSL 1.1.
> >>
> >>Sharon
> >>
> >>
> >>
> >>
> >>Sharon Adler wrote:
> >>
> >>
> >>>Peter,
> >>>
> >>>I must apologize for taking so long to answer your comment 
> on XSL 1.1.
> >>
> >>We
> >>
> >>
> >>>value your comments and recognize that we need to introduce an
> >>
> >>inheritance
> >>
> >>
> >>>mechanism that inherits selectively from the layout rather 
> than down
> >>>formatting object tree.  However, we believe that this is 
> part of a more
> >>>extensive set of functionality we wish to introduce in the 
> next version
> >>
> >>of
> >>
> >>
> >>>XSL.  It is at that time that we will design 
> "layout-driven inheritance".
> >>>
> >>>Thank you for your interest in XSL 1.1.
> >>>
> >>>Sharon
> >>
> >>
> >>Sharon,
> >>
> >>Thank you for your response.  I have some feeling for the 
> difficulties
> >>the editors face with these questions.
> >>
> >>Given that the editors wish to retain a simple FO tree inheritance
> >>model, it seems to me important that such a principle not 
> be violated
> >>for the properties on the fo:layout-master-set subtree.  If 
> properties
> >>on, e.g., individual fo:region-body elements are inherited, 
> not down the
> >>fo:layout-master-set subtree, but through the 
> fo:page-sequence-master,
> >>then FO tree inheritance has been partially replaced by 
> layout driven
> >>inheritance.
> >>
> >>I much appreciate the efforts of the editors.
> > 
> > 
> > 
> 
> 
> -- 
> Peter B. West <http://cv.pbw.id.au/>
> Folio <http://defoe.sourceforge.net/folio/>
> <http://folio.bkbits.net/> <- the atTridged version
> ---
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Received on Tuesday, 28 February 2006 18:22:12 UTC

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