RE: Re[2]: [cgmo-webcgm] XCF and "inherit" value

[Dieter Weidenbruck <dieter@itedo.com>]

I second this.

> -----Original Message-----
> From: Benoit Bezaire [mailto:benoit@itedo.com]
> Sent: Thursday, May 26, 2005 2:56 PM
> To: cgmo-webcgm@lists.oasis-open.org
> Subject: Re[2]: [cgmo-webcgm] XCF and "inherit" value
>
>
> Hi Lofton,
>
> Ok we are getting close. There's a reason why the CSS specification
> uses the word 'element' instead of 'node', and it's because a node is
> not always an element (ex: text node, comment node, doctype node
> etc...). Inheritance only applies to elements, not nodes.
>
> So I'm a bit hesitant to start using the word 'node' or 'element' for
> that matter. 'element' more or less implies XML syntax, which is not
> the case here.
>
> I disagree that Metafile is the root of the document. I think the
> Picture is the root. Here's why:
>
> i)   A root must be derived from the node class. This is not the case
> for Metafile.
> ii)  We currently say for 'parentNode': The parent (immediate ancestor
> node of a node) of this node. All nodes, except WebCGMPicture may have
> a parent.
> iii) We get to the first picture via getWebCGMDocument().firstPicture,
> not using firstChild.
>
> So would you agree on the following wording?
>
> "For the purposes of this inheritance model, Picture (the parent of
> top-level APSs within the picture body) is treated like an APS and is
> the root of the document tree."
>
> --
>  Benoit   mailto:benoit@itedo.com
>
>
> Wednesday, May 25, 2005, 10:25:00 AM, Lofton wrote:
>
> LH> First:  I agree that "inherit" should also be on 'layer'  (as
> you said,
> LH> don't specialize an attribute-value set depending on the host
> element).
>
> LH> Second:  I think we all agree what we want to happen for the
> top-level APS
> LH> or 'layer'.  If it has the value "" (empty string, no set value) or
> LH> "inherit", then it ought to take Initial Value.  What is
> unclear (to me at
> LH> least) is what the inheritance-model wording currently says
> about it, i.e.,
> LH> if/how 5.4 currently specifies that.  Because Picture and
> Metafile nodes
> LH> are ancestors to the top-level APS within the picture.
>
>
> LH> At 03:34 PM 5/24/2005 -0400, Benoit Bezaire wrote:
> >>Hi Lofton,
> >>
> >>I'm catching up to emails... I've read the whole thread and I'm
> >>replying only to this email. I don't think the problem is as
> >>complicated as the thread seems to imply. See inline.
>
> LH> No, I don't think it's particularly complicated, but ... if I
> was unable to
> LH> determine the answer from 5.4, then that might indicate a
> problem for a
> LH> naive reader (note, I'm not necessarily claiming to be non-naive!).
>
> >>[...]
> >>LH> Thoughts?  How can we deal with this cleanly?
> >>To me, the thing seems quite simple and I doubt any changes are
> >>required. Here's why?
> >>
> >>(i'm using markup, it's easier :)
> >><metafile>
> >>   <picture>
> >>     <grobject visibility="inherit"/>
> >>   </picture>
> >></metafile>
>
> LH> Let me make it simpler yet:
>
> LH> <metafile>
> LH>     <picture>
> LH>       <grobject id="obj1" ... />
> LH>     </picture>
> LH> </metafile>
>
> LH> This should have exactly the same effect as your example,
> right?  (And it
> LH> doesn't force us to look at 5.4.2 -- handling of "inherit" value.)
>
> LH> The problem is in 5.4.1.1, #2:  "Otherwise [if not explicitly
> set], if the
> LH> style attribute is inherited and the Application Structure is
> not the root
> LH> of the document tree, use the computed value of the parent Application
> LH> Structure."
>
> LH> I understand that you did a first-order adaptation of CSS2
> wording (well
> LH> done, at that!) and changed "element" to "APS".  To answer
> your question,
> LH> No, Picture is not an APS, altho it sort of looks like one for some
> LH> purposes.  (Nor is Metafile, which is the root according to
> figure 5.1b,
> LH> and is where WebCGMNode.parentNode stops, presumably).
>
> LH> So we need wording that allows the inheritance chain to
> continue up beyond
> LH> the top-level APS, to the "root of the document tree".  Options:
>
> LH> Opt.1:  s/APS/node/  ?  (Or in original CSS2, s/element/node/).
> LH> Opt.2:  add at end of 5.4.1.1 something like, "For the
> purposes of this
> LH> inheritance model, Picture (the parent of top-level APSs
> within the picture
> LH> body) is treated like an APS, and Metafile (the root of the
> document tree)"
>
> LH> Recommendation:  Opt.2.  Reason:  if those words had been
> present, I never
> LH> would have asked the question in the first place.
>
> LH> (Note.  We might want to add even more words, or an example involving
> LH> 'visibility' or 'interactivity', the two affected attributes.)
>
> LH> One last comment...
>
>
> >>What is the value of visibility on the <grobject>?
> >> From section: 5.4.1.1 Specified values,
> >>"1. If the style attribute is assigned a value, use it."
> >>Ok, simple enough... so we go to section 5.4.1.2 Computed values,
> >>"See the section on inheritance for the definition of computed values
> >>when the specified value is 'inherit'."
> >>Ok, to section 5.4.2.1 The 'inherit' value,
> >>"the property takes the same computed value as the style attribute for
> >>the Application Structure's parent."
> >>Here it doesn't really matter if you think there is a parent or not,
> >>you will end up that you have to use the initial value, which is "on".
> >>In both cases you will end up with "3. Otherwise use the style
> >>attributes's initial value." of section 5.4.1.1
> >>
> >>BTW, this definition seems to work perfectly fine for HTML and SVG.
> >>And I don't quite see what is the difference between my example above
> >>and this:
> >>
> >><svg>
> >>   <g visibility="inherit"/>
> >></svg>
> >>
> >>The point is that when an implementation is doing the cascade, it
> >>has no choice but to initialize it's style properties structure to the
> >>Initial Values; those values are then cascaded down. So it doesn't
> >>matter if you start at the <metafile> node, the <picture> node, or on
> >>the <grobject> node... as soon as you see 'inherit', it will be
> >>replaced by 'on' (the initial value).
> >>
> >>I tried to adapt the CSS wording to WebCGM when I first wrote it, and
> >>it was me who replaced 'element' with 'Application Structure', which
> >>may be introducing the question of "Is the picture node an APS?. I
> >>think that's the only possible source of confusion on the matter. What
> >>is a good replacement for 'element'?
>
> LH> Yes, as 5.4.1.1, #2, shows, it is the specific use of APS
> that causes the
> LH> problem, because ancestors of top-level APSs are not APSs.
>
> LH> -Lofton.
>
>
>