Jeremias Maerki wrote:

> I got my copy of Michael Plass' dissertation today. A cursory 
> overview shows that this document will provide some insight 
> on using Knuth element model for page breaking but it also 
> makes clear that we still have to come up with solutions for 
> certain tricky problems that he didn't have to deal with back 
> then. At any rate, the dissertation seems more helpful than 
> the two documents we found by Brüggemann-Klein, Klein and Wohlfeil.

Hi Jeremias:

I got my copy yesterday and spent some time in it as well. I wanted to weave
some thoughts about it into the thread from a few days ago that dealt with
this same topic. In that thread, you raised the same two issues that I have
been troubled about for page-breaking: 1) differing page IPDs, and 2)

WRT differing page IPDs, I think it is probably very acceptable in almost
every case to simply change the rules. IOW, If you want to use layout
strategy X, you must do so on a page-sequence-master that has all page IPDs
the same and that uses the same column-count. (Plass acknowledges that the
problem to be solved is two-dimensional, but specifically says that his
algorithm is one-dimensional.) Whether dealing with business forms
(invoices, purchase orders, etc.) or high-end book publishing (I have
experience with both), I cannot think of a use case for differing IPDs on
pages in the same page-sequence. If the goal is 100% standard compliance,
this isn't good enough. However, if the goal is to get some work done for a
client, and it doesn't hinder future 100% compliance, then this would be the
way I would address it.

Side-floats are another story. Plass addresses them by adding a new
primitive to the box/glue/penalty model, called "insert" (page 15). However,
I thought the following was pretty interesting as well, drawn from the last
paragraph of his dissertation:

"There are other ways of incorporating approximations into the pagination
routine; for instance, inset figures could be handled satisfactorily by
doing the pagination as if they were full width figures with the same area
as the original figures; afterwards the paragraphs could be re-broken in
order to fit them around the figures. The optimizing line breaking algorithm
would be helpful in this regard, since it could break the text on the page
in such a way that it would come out to the right number of lines. Layout
artists traditionally use approximate copyfitting techniques to do such
tasks, so methods like this hold much promise."

So, if an insert requiring 4 square inches is required, and the IPD is six
inches, add 2/3 of an inch to the BPD of the block, do your copyfitting,
then come back and lay the block out properly later.

After thinking through all of these papers and ideas, I am more convinced
than ever of the utility of pluggable layout. But I guess you guys like
branches better :-)

Victor Mote

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