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From "Peter B. West" <pbw...@powerup.com.au>
Subject Re: markers in redesign
Date Sun, 02 Mar 2003 21:24:17 GMT
J.Pietschmann wrote:
> Hello,
> I reexamined the marker problematic again.
> "When comparing two areas to determine which one is better, the
>  terms "first" and "last" refer to the pre-order traversal order
>  of the area tree."
> The quote above shows another problem: I'm used to the term
> "pre-order" in context of binary trees, where it means that
> first the "first"/"left" subtree is visited, then the node
> itself, then the "last"/"right" subtree. Unfortunately, the
> area tree is hardly a binary tree. How should the term be
> interpreted in this context?
> Let's take an example:
>  <fo:block id="A">
>    <fo:marker marker-class="I" id="m1"/>
>    <fo:block id="B">
>      <fo:marker marker-class="I" id="m2"/>
>      ...
>    </fo:block>
>  </fo:block>


More heart-in-the-mouth stuff for me, as I have coded the pre- and 
post-order iterators in Node according to another interpretation, and I 
have just had a mad search to try to justify it.

 From the DOM Level 2 Traversal and Range spec glossary:

document order
     The term document order has the same meaning as depth first, 
pre-order traversal, which is equivalent to the order in which the start 
tags occur in the text representation of the document.

In such an ordering, A precedes B.

> Block B is, according to my interpretation of "pre-order"
> before block A, therefore retrieving class I with
> first-starting-within-page would get marker 2. Also,
> retrieving with either last-starting-within-page or
> last-ending-within-page should return marker m1.

Peter B. West  pbwest@powerup.com.au  http://www.powerup.com.au/~pbwest/
"Lord, to whom shall we go?"

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