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% P L A C E I N S . T E X ver 2.0 Mar 3, 1995
%
% By Donald Arseneau <asnd@reg.triumf.ca>
%
% Insertions that keep their place.
%
% This TeX file provides various mechanisms (for plain TeX and close
% relatives) to let insertions (footnotes, topins, pageins, etc.) float
% within their appropriate section, but to prevent them from intruding
% into the following section, even when sections do not normally begin
% a new page. (If your sections normally begin a new page, just use
% \supereject to flush out insertions.)
%
% Different combinations of insertions can be controlled with different
% commands:
%
% \par\penalty-20029
% If there are any insertions that will not fit on the current page,
% a \supereject is performed and the following text will continue at
% the top of a page after all insertions. If all insertions do fit
% on the current page, then the following text will continue
% immediately on this page.
% \par\penalty-20030
% Like above, except that if there are any footnotes at all on the
% current page, the section must begin on the next page. (This is so
% no footnote text from section 1 will appear beneath the beginning
% of section 2.)
% \par\penalty-10029
% If any insertions cannot fit on the current page, eject them, and
% then allow the following section to begin immediately on the same
% page as the last insert. If all insertions do fit on the current
% page, then the following text will continue immediately on this
% page.
% \barrier{\eject}{\topins}
% If there are any pageinserts or topinserts that do not fit on the
% current page, eject them, and then allow the following section to
% begin immediately on the same page as the last insert. Split
% footnotes or other insertions are allowed to intrude into the next
% section.
% \barrier{\supereject}{\topins}
% Like the \barrier command above, but if any inserts are ejected
% the following section will begin at the top of a new page (like
% \supereject).
% \barrier{...}{\footins}
% *** NOT ALLOWED *** You will get spurious space and footnote-rules
% at the bottom of pages!
% \barrier{...}{\margins}
% If you define other insertion classes, such as marginal notes, you
% can use \barrier for them too. But only if \skip\margins=0pt.
% You must also add any new insertion classes to the definition of
% \placerestoreoutput
%
% How to use: First, \input this file (of course!). Then, at the beginning
% of a new section, or at any boundary that insertions should not cross, put
% one of the commands listed above. Presumably, you will actually put these
% commands at the start of your own \section or \startsection macro; that is
% why they are non mnemonic!
%
% There is a slight chance that a footnote may be separated from its reference
% in the text after \penalty-xxxxx when there are no split insertions. (LaTeX
% has the same possibility at every float!)
\chardef\noplaceoutput\catcode`\@
\catcode`\@=11
\edef\zero@skip{\the\z@skip}
\def\barrier#1#2{\par\begingroup
\ifdim\skip#2>\z@{\newlinechar10\errhelp{\barrier#2may produce some spurious
extra material on the page, ^^J but I will try anyway.}\errmessage{Bad use
of \string\barrier}}%
\fi
\skip@\lastskip \edef\next{\the\skip@}\ifx\next\zero@skip\else\vskip-\skip@\fi
\penalty\z@ % update page parameters
\fam-\insertpenalties
\insert#2{\floatingpenalty\@ne}%
\ifx\next\zero@skip\else\vskip\skip@\fi
\advance\fam\insertpenalties % 0: no held; 1: held over
\expandafter\endgroup
\ifnum\fam=\@ne % then do eject
% \message{There are held-over \string#2 inserts; performing \string#1. }%
\ifdim\pagetotal<\topskip \leftline{}\kern-\topskip\fi % avoid empty list
{\dimen@\pagetotal \advance\dimen@\pagedepth
\ifdim\dimen@<\pagegoal\vfill\fi}%
#1\@barrier{#1}{#2}\else
% \message{There are no held-over \string#2 inserts. \space}%
\fi
}
\def\placeinsoutput{%
\ifnum\outputpenalty=-20030\relax % eject if any footnotes
\ifvoid\footins\else
\fam\insertpenalties \advance\fam\@ne \insertpenalties\fam
\fi \outputpenalty=-20029\relax
\fi
\ifnum\outputpenalty=-20029\relax % Check for `supereject' flag
\ifnum\insertpenalties>\z@ % something is being held over, must get it out
% \message{Forcing insertions on their own pages. \space}%
\ifvoid\footins \r@ggedbottomtrue \else \advance\skip\footins 0ptplus1fil\fi
\noplaceoutput % performs \supereject
\else % must rejoin seamlessly:
\placerestoreoutput
\fi
\else % check for other flag...
\ifnum\outputpenalty=-10028 % in the middle of ejecting
\ifnum\insertpenalties=\z@ \global\setbox\@cclv\vbox{}\fi
\outputpenalty=-10029
\fi
\ifnum\outputpenalty=-10029\relax % section start
\ifnum\insertpenalties>\z@ % something is being held over, must get it out
% \message{Forcing insertions. \space}%
\ifvoid\footins \r@ggedbottomtrue \else \advance\skip\footins 0ptplus1fil\fi
\noplaceoutput % performs \eject, perhaps repeatedly:
\leftline{}\kern-\topskip \penalty-10028\relax % (like \dosupereject)
\else % must rejoin seamlessly:
\placerestoreoutput
\fi
\else % just a regular page break
\noplaceoutput
\fi
\fi
}
% there is a slim chance that footnotes may lose their place.
\def\placerestoreoutput{%
\ifvoid\footins\else\insert\footins{\unvbox\footins}\fi
\ifvoid\topins\else\insert\topins{\unvbox\topins}\fi
% If you have other floating insertion classes, do the same here.
\unvbox\@cclv
}
\catcode`\@=\noplaceoutput
\edef\noplaceoutput{\the\output}
\output{\placeinsoutput}
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