Hi Arno,
Here are some design remarks about what I understood from my work on the
breaker. Hopefully a sum of a few [dozen?] of mails like this will
together constitute something to transform into a chapter in the CG...
Thanks, I've reverted the patch in the meantime. However, the
information that you see in annotate-spacing is actually computed after
line-breaking,
ok, so why can't it then be taken into account for page-breaking?
The problem is that page-breaking does not come *after* page-breaking.
Well, conceptually, it sort of does. But the optimization of breaking
is global over the product space of all line breaking possibilities by
all page breaking possibilities. It is done in the hope to get more
optimal breaks. The downside is that we are forced to use "height
estimations" instead of real heights of things; otherwise we would need
to do page layout for every possible break configuration, which would be
prohibitively expensive.
This was discussed on this list only a few weeks ago. I think we are on
our way to get rid of global page*line breaking. Height estimation is
just too inaccurate, so you either have music running off the page at
the bottom, or (no less ugly) empty space. We did fix a bunch of height
estimation issues, but I do not know how many more are left. This one
we are discussing right now, is another example of problem caused by
height estimation.
Since it more than doubles the computation time (often by far) there
must be something redundant, no?
No, because the height used in page breaking, is not the actual height;
it is just an estimate (often wrong). This is what Joe means when he
says, "...and they aren't actually correct to begin with".
Boris
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