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From: julian@uhunix2.uhcc.Hawaii.Edu (Julian Cowley)
Newsgroups: comp.text.tex
Subject: Re: TeX bug or feature?
Message-ID: <13067@uhccux.uhcc.Hawaii.Edu>
Date: 16 May 91 08:02:11 GMT
References: <13021@uhccux.uhcc.Hawaii.Edu> <1991May15.223441.23055@csrd.uiuc.edu>
Sender: news@uhccux.uhcc.Hawaii.Edu
Organization: University of Hawaii at Manoa
Lines: 41

Victor Eijkhout <eijkhout@s41.csrd.uiuc.edu> writes:
>julian@uhunix2.uhcc.Hawaii.Edu (Julian Cowley) writes:
>>Can anyone explain to me why TeX sets \pagegoal to the g present
>>at the end of the page breaking algorithm rather than the g for
>>the best break?

>The \pagegoal is set to the \vsize when the first nondiscardable item is
>added to the current page.  After that it doesn't change, except when an
>insertion occurs:  rather than adding insertions to the \pagetotal they
>are subtracted from the \pagegoal, which makes sense, because the text of
>the page has to fit in \vsize so why not decrease that?

That does make sense, but really what I was after is the height
of all insertions present when the \output routine is called.

>>% t=1066.0 plus 17.0 minus 12.0 g=1063.1112 b=1 p=100 c=201
>                                   ^^^^
>>% split254 to -16.83324,12.0 p=-10000
>                         ^^^^
>>% t=1078.0 plus 17.0 minus 12.0 g=1051.1112 b=* p=0 c=*
>                                   ^^^^
>And this looks like a split insertion, leaving 12pt (that is, one line) to
>be placed on the current page. Beats me how you can force to split to a
>negative value, but hey, they're your macros.

>Anyhow, the \pagegoal is again diminished by 12pt.

And that's the problem.  To get the height of all insertions, I
expected to use \vsize - \pagegoal, but since \pagegoal is set to
something different, I got the wrong answer.  However, I've since
discovered that I can use the height of \box255, since that's
what TeX uses as the final page height sans insertions.

In my subject line I contemplated it being a bug, but now I'm not
so sure of myself since TeX has been working that way for quite
some time without much outcry from users.  But, it's something
that I wish Knuth had taken into consideration when he decided
to make all the \page* primitives available.

Julian Cowley / U. of Hawaii at Manoa	| "God is love." -- John, c. 60 A. D.
julian@uhunix.uhcc.hawaii.edu		| "All you need is love." -- John, 1967