Peter B. West wrote:

> It occurs to me that some of the implications of the FAD 
> approach have not been successfully communicated.  Part of 
> this may well be because of my own inadequate understanding 
> of the FOP process.  Before I continuing with this 
> discussion, I had better ensure that my understanding of one 
> important point is correct.  Why does FOP process in minimum 
> units of a page-sequence?

1. To process in units smaller than a page-sequence presents layout
dependency problems. An item on the last page of a page-sequence can
theoretically change the layout of something on the first page.
2. To process in units larger than page-sequence presents memory-usage
problems.

Except for things like unresolved page numbers in other page-sequences
(deemed to have an acceptable workaround), you can layout a page-sequence in
isolation from the other page-sequences.

BTW, although the main purpose of the FO Tree event-firing mechanism
(recently removed from HEAD) was to allow different layout engines to react
to page-sequence objects in different ways, one of the IMO advantageous
side-effects was that other high-level events could be fired as well,
allowing a layout engine to use something other than page-sequence as a
trigger. I thought at the time that this might be helpful to those wanting a
more "eager" layout strategy.

Victor Mote

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