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+% \iffalse meta-comment
+%
+%% File: fewerfloatpages.dtx (C) Copyright 2019-2020 Frank Mittelbach
+%
+% It may be distributed and/or modified under the conditions of the
+% LaTeX Project Public License (LPPL), either version 1.3c of this
+% license or (at your option) any later version. The latest version
+% of this license is in the file
+%
+% https://www.latex-project.org/lppl.txt
+%
+% The development version of the bundle can be found below
+%
+% https://github.com/FrankMittelbach/fmitex/
+%
+% for those people who are interested or want to report an issue.
+%
+
+\def\fewerfloatpagesdate {2020/02/14}
+\def\fewerfloatpagesversion{v1.0a}
+
+
+%<*driver>
+\documentclass
+ [final]
+ {l3doc-TUB}
+\hfuzz=1.6pt % not even one tt character, don't worry.
+
+\makeatletter
+ \@mparswitchfalse
+\makeatother
+
+\setcounter{page}{1}
+
+\newcommand\ctr[1]{\texttt{\upshape#1}}
+\newcommand\option[1]{\texttt{\upshape#1}}
+\newcommand\mnote[1]{\marginpar{\raggedleft\em #1}}
+
+\usepackage{csquotes}
+\EnableCrossrefs
+\CodelineIndex
+
+
+\begin{document}
+ \DocInput{fewerfloatpages.dtx}
+\addtolength\signaturewidth{42pt}
+\makesignature
+\end{document}
+%</driver>
+%
+% \fi
+%
+%
+% \title{The \texttt{fewerfloatpages} package\thanks{The current
+% package version is \texttt{\fewerfloatpagesversion} dated
+% \fewerfloatpagesdate.}}
+% \author{Frank Mittelbach}
+% \address{Mainz, Germany}
+% \netaddress{https://www.latex-project.org}
+% \personalURL{https://ctan.org/pkg/fewerfloatpages}
+%
+% \maketitle
+%
+%
+% \begin{abstract}
+%
+% \LaTeX{}'s float algorithm has the tendency to produce fairly
+% empty float pages, i.e., pages containing only floats but with a
+% lot of free space remaining that could easily be filled with nearby
+% text. There are good reasons for this behavior; nevertheless, the
+% results look unappealing and in many cases documents are
+% unnecessarily enlarged.
+%
+% The \pkg{fewerfloatpages} package provides an extended algorithm
+% that improves on this behavior without the need for manual intervention by
+% the user.
+%
+% \end{abstract}
+%
+% \microtypesetup{protrusion=false}
+% \tableofcontents
+% \microtypesetup{protrusion=true}
+%
+% \DoNotIndex{\@fpmin}
+% \DoNotIndex{\@testwrongwidth}
+% \DoNotIndex{\@cons}
+% \DoNotIndex{\@currbox}
+% \DoNotIndex{\@currtype}
+% \DoNotIndex{\@elt}
+% \DoNotIndex{\@empty}
+% \DoNotIndex{\@gobble}
+% \DoNotIndex{\@ne}
+% \DoNotIndex{\@next}
+% \DoNotIndex{\@spaces}
+% \DoNotIndex{\@tempcnta}
+% \DoNotIndex{\@tempcntb}
+% \DoNotIndex{\@tempdima}
+% \DoNotIndex{\@tempdimb}
+% \DoNotIndex{\@testtrue}
+% \DoNotIndex{\@undefined}
+% \DoNotIndex{\@vtryfc}
+% \DoNotIndex{\@xxxii}
+% \DoNotIndex{\@ztryfc}
+% \DoNotIndex{\fl@trace}
+% \DoNotIndex{\@bitor}
+% \DoNotIndex{\NeedsTeXFormat}
+% \DoNotIndex{\TeX}
+% \DoNotIndex{\advance}
+% \DoNotIndex{\begingroup}
+% \DoNotIndex{\bx@B}
+% \DoNotIndex{\bx@D}
+% \DoNotIndex{\bx@I}
+% \DoNotIndex{\count}
+% \DoNotIndex{\def}
+% \DoNotIndex{\divide}
+% \DoNotIndex{\else}
+% \DoNotIndex{\endgroup}
+% \DoNotIndex{\fi}
+% \DoNotIndex{\gdef}
+% \DoNotIndex{\global}
+% \DoNotIndex{\ht}
+% \DoNotIndex{\if@test}
+% \DoNotIndex{\if@twocolumn}
+% \DoNotIndex{\ifdim}
+% \DoNotIndex{\ifnum}
+% \DoNotIndex{\ifodd}
+% \DoNotIndex{\ifx}
+% \DoNotIndex{\let}
+% \DoNotIndex{\maxdimen}
+% \DoNotIndex{\multiply}
+% \DoNotIndex{\newcommand}
+% \DoNotIndex{\newcount}
+% \DoNotIndex{\newcounter}
+% \DoNotIndex{\providecommand}
+% \DoNotIndex{\relax}
+% \DoNotIndex{\renewcommand}
+% \DoNotIndex{\reserved@a}
+% \DoNotIndex{\sixt@@n}
+% \DoNotIndex{\space}
+% \DoNotIndex{\string}
+% \DoNotIndex{\the}
+% \DoNotIndex{\tw@}
+% \DoNotIndex{\typeout}
+% \DoNotIndex{\xdef}
+% \DoNotIndex{\z@}
+%
+%
+% \section{Introduction}
+
+% We start by giving a quick overview of \LaTeX{}'s float algorithm
+% and the problems that result from the approach used.
+%
+% We then look in some detail into possible alterations and
+% improvements to that algorithm and discuss possible issues that
+% need to be resolved. In this section we also describe all
+% configuration possibilities of the extended algorithm.
+%
+% The final section then documents the code changes that are
+% necessary to \LaTeX{} kernel macros to implement the extension.
+%
+% \subsection{A quick overview of \LaTeX's float algorithm}
+%
+% \LaTeX{}'s output routine uses a greedy algorithm to place floats
+% near to their call-outs in the source document. The decision of how
+% to place a float is made when the float is first encountered. If
+% possible it is placed onto the current page, either in mid-text,
+% on top or into the bottom area, depending on what is allowed for
+% the float and how many floats are already placed into those
+% areas.
+%
+% If the float can't be placed immediately, it goes into a defer
+% list, and in order to not accumulate too many unplaced floats
+% \LaTeX{} tries to empty that list whenever there is a chance. This
+% chance comes after the next page break: \LaTeX{} then starts a
+% special ``float page'' algorithm in which it examines the defer
+% list and from it forms float pages (i.e., pages that contain only
+% floats). If necessary, it generates several float pages and only
+% stops if there are no floats waiting to be placed, or there are
+% too few floats to form a float page, or there are only floats left
+% that are for one or another reason not allowed to be placed in
+% this way.
+%
+% Finally \LaTeX{} looks at the remaining floats and tries to place
+% as many of them as possible into the top and bottom area of the
+% next page. Then it continues to process further text to fill the
+% text part of that page. Details on the exact behavior of the
+% algorithm are discussed in \cite{fmi:floatplacement}.
+%
+%
+% \subsection{The typical float page and its problems}
+%
+% \LaTeX{} considers a float page to be successfully built if its
+% floats take up more than \cs{floatpagefraction} of the whole
+% page. By default this parameter is set to \texttt{.5} which means
+% that such float pages may end up being half empty.
+%
+% Many users think that this is not a good value and try to improve on
+% it by enforcing a higher percentage (such as 80\%) only to find
+% that this prevents \LaTeX{} in many cases from successfully
+% generating any float page, with the effect that all floats are
+% suddenly piling up at the end of the document.
+%
+% Why is this the case? In a nutshell, because a higher percentage
+% makes it much more likely that a float can't be
+% placed, because it is not big enough to be used on its
+% own and no other nearby floats can be combined with
+% it, because their combination violates some other restriction,
+% e.g., together they are bigger than a page, not all of them are
+% allowed to go on float pages, etc. The moment that happens this
+% float prevents the placement of all later floats of the same
+% class too (i.e., all figures) and disaster is ensured. In most
+% cases these floats will then never get placed, because they need a
+% float of the right size from a different class to appear, which
+% may in theory happen but is, unfortunately, unlikely.
+%
+% Thus,\mnote{Tinkering with the parameter settings will usually
+% produce unwanted effects} while tempting, tinkering with this
+% parameter by making it larger is usually not a good idea, unless
+% you are prepared to place most if not all of your floats
+% manually, by overwriting the placement algorithm on the level of
+% individual floats (e.g., using \texttt{!}\@ syntax and/or
+% shifting its position in the source document).
+%
+% Why does the current algorithm have these problems? To some extent,
+% because it offers only global parameters that need to fit
+% different scenarios and thus settings that are suitable when many
+% floats need to be placed result in sub-optimal paginations in
+% document parts that contain only a few floats, and vice versa.
+% To overcome this problem, either one can try to develop
+% algorithms with many more configurable parameters that act
+% differently in different scenarios or one can let the algorithm
+% follow a main strategy, configurable with only a few parameters
+% (like today), but monitor the process and make more local
+% adjustments and corrections depending on the actual outcome of
+% that base strategy and additional knowledge of the actual
+% situation in a given document part. This is the
+% approach taken by the extension implemented in this package.
+%
+% \section{Improvements to the float page algorithm}
+%
+% A simple way to improve on the existing algorithm, without
+% compromising its main goal of placing the floats as fast as
+% possible and as close as possible to their call-outs, is the
+% following: as long as there are many floats waiting to be placed,
+% generate float pages as necessary to get them placed (using the
+% current algorithm and its parameters).
+
+% Once we are unable to build further float pages, do some level
+% of backtracking by checking if we have actually succeeded in
+% placing all floats. If there are still floats waiting to be
+% placed then assume that what has been done so far is the best
+% possible way to place as many floats as possible (which it
+% probably is). However, if we have been able to place all floats
+% onto float pages then check if the last float page is
+% sufficiently full; if not, undo that float page and instead
+% redistribute its floats into the top and bottom area of the next
+% upcoming page. This way the floats will be combined with further
+% text and we avoid a possible half-empty float page.
+%
+% This approach will not resolve all the problematic scenarios
+% where we find that \LaTeX{} has decided to favor fairly empty
+% float pages over some tighter type of placement. It will,
+% however, help to improve typical cases that do not involve too
+% many floats. For\mnote{A typical case where we don't really want
+% \LaTeX{} to make a float page} a example, if a single (larger)
+% float appears near the end of a page, then using the standard
+% algorithm it can't be immediately placed (because there isn't
+% enough free space on the current page). It is therefore moved to
+% the defer list and at the page break it is then placed onto a
+% float page (possibly by itself, if it is large enough to allow
+% for that) even though it could perfectly well go into the top or
+% bottom area of the next page and thus be combined with textual
+% material on that page.
+%
+% With the new algorithm this float page is reexamined and unless
+% it is pretty much filled up already, it is unraveled and its
+% floats are redistributed into the top and bottom areas of the
+% next page. If, however, we have many floats waiting on the defer
+% list, the normal float page algorithm will first place as many of
+% them as possible into float pages and only the last of these
+% pages will be subject to a closer inspection and a possible
+% unraveling.
+%
+% An extension of this idea (and the one that we actually
+% implement) is to monitor the whole float page generation process
+% and instead of just considering the last float page in the sequence
+% for unraveling, we look at each prospective float page in turn and
+% based on the current situation (e.g., number of floats still
+% being unplaced, free space on the float page, etc.)\@ decide
+% whether this float page should be produced or whether we should
+% stop making float pages and instead place the pending floats into
+% top and bottom areas of the upcoming page.
+%
+%
+% \subsection{Details on the extended algorithm}
+%
+% The main idea of the extended algorithm is to avoid unnecessary cases of
+% float pages especially if those float pages are fairly
+% empty.\mnote{Don't unravel a float page if there are too many
+% floats on the defer list}
+% Natural candidates are single float pages, but even in cases where
+% the current \LaTeX{} algorithm produces several sequential float
+% pages the extended algorithm may decide to replace them by normal
+% pages under certain conditions.
+% However, the main goal
+% is and should remain to place as many floats as soon as possible
+% and so generating float pages when many floats are waiting is
+% usually essential.
+%
+% \begin{variable}{floatpagedeferlimit}
+% \begin{syntax}
+% \cs{setcounter}\{floatpagedeferlimit\}\Arg{number}
+% \end{syntax}
+% Whether or not unraveling for a float page is considered at all
+% is guided by the counter \ctr{floatpagedeferlimit}. As long as
+% there are more floats waiting on the defer list than this number,
+% float pages are not considered for unraveling. The default is
+% \texttt{3} which corresponds to the default value for
+% \ctr{totalnumber}, i.e., with that setting the unraveling of a
+% floating page has a fighting chance to place all floats into the
+% top and bottom areas on the current page.
+% It would also resolve cases for up to three floats, each larger than
+% \cs{floatpagefraction}, where the standard \LaTeX{} algorithm would
+% produce three individual float pages.\strut
+% \end{variable}
+%
+% If you set the counter to \texttt{1} then only the last float
+% page in a sequence is considered, and only if it contains only a
+% single float and if there are no other floats that are still
+% waiting to be placed. If you set it to \texttt{0}, then the
+% extension is disabled, because float pages are produced only if
+% there was at least one float on the defer list.
+%
+% Even\mnote{Don't unravel if the float page contains many floats}
+% if we set \ctr{floatpagedeferlimit} to a fairly high value, we
+% may not want to unravel float pages that contain many floats. To
+% support this case there is a second counter that guides the
+% algorithm in this respect.
+%
+% \begin{variable}{floatpagekeeplimit}
+% \begin{syntax}
+% \cs{setcounter}\{floatpagekeeplimit\}\Arg{number}
+% \end{syntax}
+% Whenever the float page contains at least
+% \ctr{floatpagekeeplimit} floats it will not be unraveled. The
+% default is also \texttt{3} so that float pages with three or more
+% floats are not touched. Obviously the counter can have any effect
+% only if it has a value less than or equal to
+% \ctr{floatpagedeferlimit} because this is tested first.\strut
+% \end{variable}
+%
+%
+% There are, however, a number of other situations in which we
+% shouldn't unravel a float page even if the above checks for the
+% size of the defer list were passed successfully.\mnote{Don't
+% unravel if the float page contains at least one \texttt{\upshape
+% [p]} float} The most important one is the case when the float
+% page contains at least one float that is allowed \emph{only} on
+% float pages (i.e., has a \texttt{[p]} argument). Such a float
+% would not be placeable in a top/bottom area on any page and thus
+% would be repeatedly sent back to the defer list (possibly forever).
+%
+% The other case where unraveling would normally be
+% counterproductive is when the particular float page is nearly or
+% completely filled up with floats.\mnote{Don't unravel if the
+% float page is nearly filled} If we unravel it, then it is
+% certain that we can place only some of the floats into the top or
+% bottom area of the next page, while some would end up on the defer
+% list. That in turn means that these deferred floats float even
+% further away from their call-out positions than need be.
+%
+% \begin{variable}{\floatpagekeepfraction}
+% \begin{syntax}
+% \cs{renewcommand}\cs{floatpagekeepfraction}\Arg{decimal}
+% \end{syntax}
+% So what is a good way to determine if a float page is ``full
+% enough''? A possible answer is that if the remaining free space
+% on that page is less than \cs{textfraction} we consider it full
+% enough to stay. \cs{textfraction} defines the minimum amount of
+% space that has to be occupied by text on a normal page, thus if
+% all floats together need so much space that this amount of text
+% could not fit, then trying to place all floats onto a
+% normal page can't succeed and some of them would get deferred for
+% sure. To allow for further flexibility the algorithm uses
+% the variable \cs{floatpagekeepfraction} (defaulting to
+% \cs{textfraction}) so if desired a lower (or even a higher)
+% boundary can be set.\strut
+% \end{variable}
+%
+% The above parameters give some reasonable configuration
+% possibilities to guide the algorithm as to when and when not to unravel
+% a possible float page and instead produce further normal pages.
+% It should be noted, however, that except for the case of setting
+% \ctr{floatpagedeferlimit} to \texttt{1}, there is always a chance
+% that floats drift further away from their call-outs, because they
+% may not be immediately placeable due to other parameter settings
+% of the float algorithm. For example, the counter
+% \texttt{topnumber} (default value 2) limits the number of floats
+% that can be placed in the top area on a normal page and if more
+% remain after unraveling only two can immediately go in this area.
+%
+%
+% \subsection{Possible pitfalls and how to avoid them}
+%
+% The algorithm detects if a float is allowed only on float pages
+% (i.e., is given in the source as \texttt{[p]}) and it will ensure
+% that float pages containing such floats are not unraveled.
+%
+% However, if you have a float with the default specifier
+% \texttt{[tbp]} whose size is larger than the allowed size of the
+% top or bottom area (e.g., larger than \cs{topfraction}
+% \texttimes{} \cs{textheight}), then this effectively means it can
+% only be placed on a float page.
+%
+% However, according to the specifier the float is allowed to go
+% into the top or bottom area, so the algorithm, as explained so
+% far, would be allowed to unravel and when that float later is
+% considered for top or bottom placement it will get again deferred
+% and thus move from one page to the next, most likely messing up
+% the whole float placement.
+%
+% There\mnote{\option{checktb} (option)} are two possible ways to
+% improve the algorithm to avoid this disaster. One way
+% would be to check the float size when it is initially encountered
+% and remove any specifier that is technically not possible because
+% of the parameter settings and the float size. A possible
+% disadvantage is that this determination will be done once and any
+% later (temporary) change to the float parameters will have no
+% effect. This is currently the package default. It can be
+% explicitly selected by specifying the option \option{checktb}. In
+% this case you might see warnings like
+%\begin{verbatim}
+% LaTeX Warning: Float too large for top area: t changed to p on line ...
+%\end{verbatim}
+%
+% Another\mnote{\option{addbang} (option)} possibility is that we automatically add a
+% \texttt{!}\@ specifier to all floats during unraveling, i.e., when
+% we send them back for reevaluation. This way such floats become
+% placeable into top and bottom areas regardless of their size. This
+% may result in fewer pages at the cost of violating the area size
+% restrictions once in a while. It is specified with the option \option{addbang}.
+%
+% If\mnote{\option{nocheck} (option)} you prefer no automatic
+% adjustment of the specifiers, add the option \option{nocheck}.
+% In this case you might find that floats of certain sizes are
+% unplaceable and thus get delayed to the end of the document. If
+% that happens, the remedy is either to explicitly specify
+% \texttt{[p]} or \texttt{[hp]} for such a float (to ensure that
+% they aren't subject to unraveling) or to manually add an
+% exclamation specifier, e.g., \texttt{[!tp]} so that \LaTeX{}
+% doesn't use the size restrictions in its algorithm.
+%
+%
+%
+% \subsection{Tracing the algorithm}
+%
+% The\mnote{\option{trace} (option)} package offers the option
+% \option{trace}, which if used, will result in messages such as
+%\begin{verbatim}
+% [1]
+% fewerfloatpages: PAGE: trying to make a float page
+% fewerfloatpages: ----- \@deferlist: \bx@B \bx@D
+% fewerfloatpages: starting with \bx@B
+% fewerfloatpages: --> success: \bx@B \bx@D
+% fewerfloatpages: ----- current float page unraveled
+% (free space 192.50336pt > 109.99832pt)
+% [2]
+%\end{verbatim}
+% which means that the algorithm is trying to make a float page
+% from the defer list which at that point contained two floats (the
+% float boxes \cs[no-index]{bx@B} and \cs[no-index]{bx@D}), that it
+% was able to produce a float page containing just
+% \cs[no-index]{bx@B} and \cs[no-index]{bx@D}, and that the extended
+% algorithm then decided to unravel that float page, because it has
+% an unused space of \texttt{192.5pt}, i.e., roughly 16 text lines. With the current
+% \cs{floatpagekeepfraction} that is too much empty space on the
+% page.
+%
+% Or it might say
+%\begin{verbatim}
+% fewerfloatpages: PAGE: trying to make a float page
+% fewerfloatpages: ----- \@deferlist: \bx@D \bx@F \bx@G \bx@H \bx@I
+% fewerfloatpages: starting with \bx@D
+% fewerfloatpages: --> success: \bx@D \bx@F
+% fewerfloatpages: ----- too many deferred floats for unraveling (5 > 3)
+% [3]
+%\end{verbatim}
+% which means that the algorithm made a float page out of the first
+% two floats from the defer list (i.e., 3 remained).
+% That
+% page was kept regardless of the amount of free space it contained
+% because we have a total of 5 floats on the defer list and the
+% counter \ctr{floatpagedeferlimit} has its default value of \texttt{3}.
+%
+% The above tracing messages are both from the same test
+% document. What they also (implicitly) show is that the unraveling
+% that happened after page~1 resulted in only one float (\cs[no-index]{bx@B})
+% being placed on page~2, because we see the second one (\cs[no-index]{bx@D})
+% reappearing in the defer list after page~2 got finished. In other
+% words it was moved one page further away from its call-out: the
+% price for getting a nicely filled page~2 instead of a fairly empty
+% float page with roughly 200 points left empty.
+% The final part of that test document then exhibits another
+% type of message:
+%\begin{verbatim}
+% fewerfloatpages: PAGE: trying to make a float page
+% fewerfloatpages: ----- \@deferlist: \bx@G \bx@H \bx@I
+% fewerfloatpages: starting with \bx@G
+% fewerfloatpages: --> success: \bx@G \bx@H \bx@I
+% fewerfloatpages: ----- all floats placed on float page(s)
+% fewerfloatpages: ----- current float page kept, full enough
+% (free space 38.99496pt < 109.99832pt)
+% [4]
+%\end{verbatim}
+% This means that the remaining floats (that were left unplaced
+% after float page~3 got constructed) formed a float
+% page and that float page was the last in sequence (i.e., all
+% floats have been placed). However, this time the algorithm decided not
+% to unravel it, because it is nicely full: there are only 39 points
+% of free space left on that page.
+%
+% Three other possible messages are shown in this sequence of
+% tracing lines from a second test document (which is using some uncommon
+% settings: \ctr{floatpagedeferlimit} is \texttt{10} and
+% \ctr{floatpagekeeplimit} is \texttt{5}):
+%\begin{verbatim}
+% [1]
+% fewerfloatpages: PAGE: trying to make a float page
+% fewerfloatpages: ----- \@deferlist: \bx@B \bx@C \bx@D \bx@E \bx@F \bx@G \bx@H
+% fewerfloatpages: starting with \bx@B
+% fewerfloatpages: --> success: \bx@B \bx@C \bx@D \bx@E \bx@F \bx@G \bx@H
+% fewerfloatpages: ----- current float page kept (contains at least 5 floats)
+% [2] [3]
+%\end{verbatim}
+% In this case 7 floats have been waiting on the defer list and the
+% algorithm was able to construct a float page using all of them.
+% The algorithm then keeps that page because it has 5 or more floats
+% in it (the value of the \ctr{floatpagekeeplimit} counter).
+%
+% The next message in that test document shows what happens
+% when there are not enough floats waiting or they are simply too
+% small (to even get past the \cs{floatpagefraction} limit):
+%\begin{verbatim}
+% fewerfloatpages: PAGE: trying to make a float page
+% fewerfloatpages: ----- \@deferlist: \bx@I \bx@J
+% fewerfloatpages: starting with \bx@I
+% fewerfloatpages: --> fail
+% fewerfloatpages: starting with \bx@J
+% fewerfloatpages: --> fail
+% fewerfloatpages: --> fail: no float page made
+% [4]
+%\end{verbatim}
+% So no float page was made, but for some reason (that becomes clear
+% later) the two floats also didn't got distributed into the top or
+% bottom area of the next page. Instead they remained on the
+% defer list and during processing of page~4 one more float was
+% found so that after that page the defer list had grown to
+% length~3:
+%
+%\begin{verbatim}
+% fewerfloatpages: PAGE: trying to make a float page
+% fewerfloatpages: ----- \@deferlist: \bx@I \bx@J \bx@K
+% fewerfloatpages: starting with \bx@I
+% fewerfloatpages: --> success: \bx@I \bx@J \bx@K
+% fewerfloatpages: ----- current float page kept, contains a float
+% fewerfloatpages: with p but no t or b specifier
+% [5]
+%\end{verbatim}
+% This time all floats could be placed, but again the float page
+% wasn't unraveled (even though in the test document it contained a
+% lot of white space) because of the fact that one of its floats (in fact
+% the first though that can only be deduced implicitly) was
+% specified as a \enquote{float page only} float. This explains why
+% on page~4 \cs[no-index]{bx@I} couldn't be placed into the top or bottom
+% area and then all following floats of the same class (the test
+% document contained only \env{figure} floats) couldn't be placed
+% either.
+%
+% If\mnote{Detailed tracing of the complete algorithm} you want
+% detailed tracing of the complete algorithm, also load the
+% \pkg{fltrace} package and enable the tracing with
+% \cs{tracefloats} anywhere in your document. Note, however, that
+% the resulting output is very detailed but rather low-level and
+% unpolished.
+%
+%
+%
+%
+%
+% \subsection{Local (manual) adjustments}
+%
+% If the extended algorithm is used you will get fewer float pages
+% that contain a noticeable amount of white space. By adjusting
+% \cs{floatpagekeepfraction} and the counters \ctr{floatpagekeeplimit} and
+% \ctr{floatpagedeferlimit} you can direct the algorithm to unravel more or
+% fewer of the otherwise generated float pages. However, in some cases
+% it might happen that redistribution of the floats into the top and
+% bottom areas of the next page(s) may result in some of them
+% drifting too far away from their call-outs. If that happens, you can
+% either try to change the general parameters or you could help the
+% algorithm along by using the optional argument of individual float
+% environments.
+% The two main tools at your disposal are
+% \begin{itemize}
+% \item
+% using the \texttt{[!..]} notation to allow the float to go into
+% the top or bottom area even if it would be normally prevented by
+% other restrictions;
+% \item
+% using \texttt{[p]} to force a float into a float page as that
+% prevents the algorithm from unravelling the float page which contains
+% that float.
+% \end{itemize}
+% As an alternative you can, of course, temporarily alter the
+% definition of the command \cs{floatpagekeepfraction} or the values
+% of two counters in mid-document, but remember that they are not
+% looked at when a float is encountered in the source but when we
+% are at a page break and \LaTeX{} attempts to empty the defer list,
+% which is usually later and unfortunately somewhat asynchronous,
+% i.e., not easy to predict.
+%
+%
+% \StopEventually{
+% \begin{thebibliography}{1}
+% \raggedright
+% \bibitem{fmi:floatplacement}
+% Frank Mittelbach.
+% \newblock How to influence the position of float environments like figure and table in \LaTeX?
+% \newblock \textsl{TUG}boat 35:3, 2014.\\
+% \newblock \url{https://www.latex-project.org/publications/indexbytopic/2e-floats/}
+% \bibitem{source2e}
+% \LaTeX{} Project Team.
+% \newblock The \LaTeXe{} Sources (660+ pages), 2020.\\
+% \newblock \url{https://www.latex-project.org/help/documentation}
+% \end{thebibliography}
+% \ifx\thisissuepageref\undefined ^^A is this TUB production ??? if not gen index
+% \setlength\IndexMin{200pt} \PrintIndex
+% \fi
+%}
+%
+%
+%
+% \section{The implementation}
+%
+% We start off with the package announcement. Requiring a fairly new
+% \LaTeX{} kernel is not absolutely necessary but it will help to
+% ensure that we patch what we think we patch and in the future it
+% means that will can be assured that the rollback functionality of
+% the kernel is available in case will need to support several
+% releases of the package.
+% \begin{macrocode}
+%<*package>
+\NeedsTeXFormat{LaTeX2e}[2018-04-01]
+% \end{macrocode}
+%
+% \begin{macrocode}
+\ProvidesPackage{fewerfloatpages}
+ [\fewerfloatpagesdate\space \fewerfloatpagesversion\space
+ improve float page generation (FMi)]
+% \end{macrocode}
+%
+% \subsection{Option handling}
+%
+% This release of the package has four options: \option{trace}
+% for tracing the algorithm, \option{addbang} and
+% \option{checktb} to handle cases where the float size in
+% combination with the float specifiers makes it difficult if not
+% impossible to place the floats, and \option{nocheck} to not make
+% adjustments for that case.
+%
+% The option \option{trace} enables tracing of the algorithm and is
+% implemented by giving the command \cs[no-index]{fl@trace} (which is also
+% used by the \pkg{fltrace} package) a suitable definition.
+%
+% To handle the case that the \pkg{fltrace} package is loaded
+% first, we use \cs[no-index]{providecommand}, so that its definition is not
+% overwritten, but used if it is already available. If the package is
+% loaded later everything works fine because it unconditionally
+% defines \cs[no-index]{fl@trace}, i.e., overwrites whatever
+% \pkg{fewerfloatpages} has defined.
+%
+% \begin{macrocode}
+\DeclareOption{trace}
+ {\providecommand\fl@trace[1]%
+ {{\let\@elt\@empty\typeout{fewerfloatpages: #1}}}}
+% \end{macrocode}
+%
+% The other three options are mutually exclusive so we number them 0
+% to 2 in the command \cs[no-index]{fp@strategy} to ensure that
+% only one is ever active. Option \option{nocheck} does nothing, with
+% the cost that some floats may float to the end of the
+% document. Option \option{addbang} adds a \texttt{!}\@ to floats
+% that are sent back for reevaluation when a float page gets
+% unraveled. Option \option{checktb} implements a different
+% approach to handling problematic floats: the vertical
+% size of a float is checked, and if it is too large to be allowed
+% into the top or the bottom area, any \texttt{t} or \texttt{b}
+% specifier is replaced by \texttt{p} (or dropped if \texttt{p} is
+% already specified).
+% \begin{macrocode}
+\def\fp@strategy{0}%
+\DeclareOption{nocheck}{\def\fp@strategy{0}} % better name?
+\DeclareOption{addbang}{\def\fp@strategy{1}}
+\DeclareOption{checktb}{\def\fp@strategy{2}}
+% \end{macrocode}
+% The actual implementation is done later. The default is
+% currently \option{checktb} but this may change to
+% \option{addbang} based on user feedback.
+% \begin{macrocode}
+\ExecuteOptions{checktb}
+\ProcessOptions
+% \end{macrocode}
+%
+%
+% \subsection{Tracing code}
+%
+% \begin{macro}[internal]{\fl@trace}
+% The command \cs[no-index]{fl@trace} is used to output tracing information.
+% By default the tracing of the algorithm is turned off, so
+% \cs[no-index]{fl@trace} will simply swallow its argument. But if
+% \pkg{fltrace} is loaded or the option \option{trace} is given
+% then the command already has a definition so we don't change it
+% here.
+% \begin{macrocode}
+\providecommand\fl@trace[1]{}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \subsection{User-level interfaces}
+%
+% For the most part the packages provides internal code that
+% extends the float algorithm of \LaTeX{}. There are, however, also
+% three new parameters that guide this algorithm; they are defined
+% in this section.
+%
+% \begin{macro}[var]{\floatpagekeepfraction}
+% The fraction that the algorithm uses to decide whether a given float
+% page is so full that it would be pointless to unravel it for the
+% reasons outlined above. The default is whatever fraction has been
+% chosen as the minimum amount of text that needs to be on a normal
+% page (i.e., \cs{textfraction}).
+% \begin{macrocode}
+\newcommand\floatpagekeepfraction{\textfraction}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \begin{macro}[var]{floatpagedeferlimit,\c@floatpagedeferlimit}
+
+% The algorithm will only consider unraveling float pages if there
+% are not too many floats on the defer list. The definition of
+% \enquote{too many} is provided through the counter
+% \ctr{floatpagedeferlimit} if there are more floats waiting to be
+% placed; float pages are generated until their number falls below
+% this level. Thus, a value of \texttt{0} will disable the whole
+% algorithm and a value of \texttt{1} means that only float pages
+% with a single float might get unraveled and only if there aren't
+% others still waiting to be placed.
+% \begin{macrocode}
+\newcounter{floatpagedeferlimit} \setcounter{floatpagedeferlimit}{3}
+% \end{macrocode}
+% \end{macro}
+
+
+
+% \begin{macro}[var]{floatpagekeeplimit,\c@floatpagekeeplimit}
+%
+% A float page that contains at least this number of floats will
+% also be kept. The default is \texttt{3} but if you have a lot of
+% small floats it might be better to set this to a higher
+% value.
+% \begin{macrocode}
+\newcounter{floatpagekeeplimit} \setcounter{floatpagekeeplimit}{3}
+% \end{macrocode}
+% \end{macro}
+
+
+
+
+
+% \subsection{Patching the \LaTeX{} kernel commands}
+%
+
+
+%
+% \begin{macro}[internal]{\@tryfcolumn}
+% The main macro we have to patch to extend \LaTeX's algorithm is
+% \cs{@tryfcolumn}. That command is changed when \pkg{fltrace}
+% gets loaded, so we make our definition as late as possible to
+% ensure that it will survive.
+% \begin{macrocode}
+\AtBeginDocument{%
+% \end{macrocode}
+%
+% \begin{macrocode}
+\def \@tryfcolumn #1{%
+ \global \@fcolmadefalse
+ \ifx #1\@empty
+ \else
+ \fl@trace{PAGE: trying to make a float
+ \if@twocolumn column/page\else page\fi}%
+ \fl@trace{----- \string #1: #1}%
+ \xdef\@trylist{#1}%
+ \global \let \@failedlist \@empty
+ \begingroup
+ \let \@elt \@xtryfc \@trylist
+ \endgroup
+% \end{macrocode}
+% Up to this point the definition is the same as in the original
+% algorithm. At this point the switch \cs[no-index]{if@fcolmade} tells us if making a
+% float page was successful and the original algorithm then called
+% \cs[no-index]{@vtryfc} and removed the floats used for this float page from the defer list.
+%
+% In the extended algorithm this is the place where things start to
+% differ as we may not want that float page to actually come into
+% existence.
+% \begin{macrocode}
+ \if@fcolmade
+% \end{macrocode}
+% As a first step we count the number of floats in the defer list
+% and save the result in \cs{fp@candidates}.
+% \begin{macrocode}
+ \fp@candidates\z@
+ \def\@elt##1{\advance\fp@candidates\@ne}%
+ #1%
+ \let\@elt\relax
+% \end{macrocode}
+% Now we compare this number with the values of the counter \ctr{floatpagedeferlimit}
+% and if it is higher we definitely want to keep the float
+% page. The rationale is that if we unravel now, then all floats from
+% the defer list need to go into the top/bottom areas (or get
+% deferred again but to a later page) and so a high number means the defer list will
+% not get shortened very much and too many floats will get delayed further.
+% \begin{macrocode}
+ \ifnum \fp@candidates >\c@floatpagedeferlimit
+ \fl@trace{----- too many deferred floats for unraveling
+ (\the\fp@candidates\space> \the\c@floatpagedeferlimit)}%
+ \else
+% \end{macrocode}
+%
+% Otherwise we do a bit more testing. First we set \cs[no-index]{if@fcolmade}
+% back to false; after all our goal is to not keep the float page. If
+% during the tests we decide otherwise we set it back to true, which
+% then signals that it should stay.
+%
+% We also count the floats on the float page, reusing \cs[no-index]{fp@candidates}
+% for that, which is why we initialize it to zero.
+% \begin{macrocode}
+ \global\@fcolmadefalse
+ \fp@candidates\z@
+% \end{macrocode}
+% The actual checking is done with
+% \cs{fp@analyse@floats@for@unraveling} and it loops over
+% \cs{@flsucceed}, i.e., the floats for that float page. This
+% checks if any float for that page has only a \texttt{[p]}
+% specifier and if so it sets \cs[no-index]{if@fcolmade} back to
+% \texttt{true} and as a side effect it also does the counting for
+% us. Furthermore, it also changes the switch to true if it finds
+% at least \ctr{floatpagekeeplimit} floats on that page.
+% \begin{macrocode}
+ \let\@elt\fp@analyse@floats@for@unraveling
+ \@flsucceed
+ \let\@elt\relax
+% \end{macrocode}
+% Now we recheck the state of the switch and if it still says
+% \texttt{false}, all tests so far indicate that we don't want the float
+% page.
+% \begin{macrocode}
+ \if@fcolmade \else
+% \end{macrocode}
+% But we aren't done yet: the float page might be nicely filled,
+% in which case it would be a shame to unravel it. During the above
+% loop we also measured the free space on the float page and stored
+% it in \cs{fp@unused@space} (see \cs{@xtryfc} below). We now
+% compare that to the maximum free space that we consider to be
+% still okay and if there is more we finally do the unraveling.
+% \begin{macrocode}
+ \@tempdima\floatpagekeepfraction\@colht
+ \ifdim \fp@unused@space >\@tempdima
+ \fl@trace{----- current float page unraveled^^J%
+ \@spaces\@spaces\@spaces\space\space\space
+ (free space \fp@unused@space\space > \the\@tempdima)}%
+% \end{macrocode}
+% For this we basically return all floats back to the
+% defer list. The switch is still \texttt{false} so it doesn't need
+% changing.
+% \begin{macrocode}
+ \xdef #1{\@failedlist\@flsucceed\@flfail}%
+% \end{macrocode}
+% However, we may also want to add a \texttt{!}\@ specifier to each of
+% the floats (if the \option{addbang} option was given)
+% so we loop over all the floats once more to get this
+% done.\footnote{This could have been integrated with
+% \cs{fp@analyse@floats@for@unraveling} but there is not much gain if
+% any and by keeping it separate the processing logic seems clearer to me.}
+% \begin{macrocode}
+ \let\@elt\fp@maybe@add@bang
+ \@flsucceed
+ \let\@elt\relax
+ \else
+% \end{macrocode}
+% But if we want to keep the float page after all, we have to set
+% the switch back to \texttt{true} so that the rest of the
+% algorithm proceeds correctly.
+% \begin{macrocode}
+ \global \@fcolmadetrue
+ \fl@trace{----- current float page kept, full enough^^J%
+ \@spaces\@spaces\@spaces\space\space\space
+ (free space \fp@unused@space\space < \the\@tempdima)}%
+ \fi
+ \fi
+ \fi
+% \end{macrocode}
+% The next \cs[no-index]{else} matches the first \cs[no-index]{if@fcolmade}, i.e., the
+% case that the algorithm wasn't able to make any float page. If
+% we are tracing the algorithm, we want to tell the user about this.
+% \begin{macrocode}
+ \else
+ \fl@trace{ --> fail: no float page made}%
+ \fi
+% \end{macrocode}
+%
+% Finally, at this point we are back in the original algorithm. Now the
+% switch tells the truth about whether or not we want to make a float
+% page, and if so, we go ahead and produce it.
+% \begin{macrocode}
+ \if@fcolmade
+ \@vtryfc #1%
+ \fi
+ \fi}%
+}% -- END of \AtBeginDocument
+% \end{macrocode}
+% \end{macro}
+%
+% \pagebreak
+%
+%
+% \begin{macro}[internal]{\@makefcolumn}
+%
+% In contrast to \cs{@tryfcolumn} this macro will always make float
+% pages out of the deferred floats. It is used by \cs{clearpage}
+% when we really need the floats to get out because there is no further
+% text coming up. Thus, in that case we should not unravel the
+% float pages. That would happen with the kernel definition of
+% \cs{@makefcolumn} as that calls \cs{@tryfcolumn} which we just
+% changed above. We therefore modify its definition to include the
+% original code for \cs{@tryfcolumn} instead of calling our updated
+% version.
+%
+% Again this change is made at \verb=\begin{document}= so that it
+% is not overwritten in case \pkg{fltrace} is loaded afterwards.
+% \begin{macrocode}
+\AtBeginDocument{%
+\def\@makefcolumn #1{%
+ \begingroup
+ \@fpmin -\maxdimen
+ \let \@testfp \@gobble
+% \end{macrocode}
+% At this point the original definition called \cs[no-index]{@tryfcolumn} and
+% the lines above ensured that it was always succeeding in making
+% a float page. However, since we have changed that command to do unraveling
+% we had better not use it any more. Instead we replace it by its original
+% definition (with the addition of two tracing lines).
+% \begin{macrocode}
+ \global \@fcolmadefalse
+ \ifx #1\@empty
+ \else
+ \fl@trace{PAGE: trying to make a float
+ \if@twocolumn column/page\else page\fi}%
+ \fl@trace{----- \string #1: #1}%
+ \xdef\@trylist{#1}%
+ \global \let \@failedlist \@empty
+ \begingroup
+ \let \@elt \@xtryfc \@trylist
+ \endgroup
+ \if@fcolmade
+ \@vtryfc #1%
+ \fi
+ \fi
+ \endgroup
+}%
+}% -- END of \AtBeginDocument
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+% \begin{macro}[internal]{\@xtryfc}
+% The only change to \cs{@xtryfc} is the addition of the
+% \cs[no-index]{fl@trace} calls. But this extra tracing info is generally
+% useful and should also be done in the \pkg{fltrace} package.
+%
+% The macro initiates a float page trial starting with the first
+% float in \cs{@trylist}. More detailed explanations can be found
+% in the documented sources of the \LaTeX{} kernel~\cite{source2e}.
+% \begin{macrocode}
+\def\@xtryfc #1{%
+ \fl@trace{ starting with \string#1}%
+ \@next\reserved@a\@trylist{}{}%
+ \@currtype \count #1%
+ \divide\@currtype\@xxxii
+ \multiply\@currtype\@xxxii
+ \@bitor \@currtype \@failedlist
+ \@testfp #1%
+ \@testwrongwidth #1%
+ \ifdim \ht #1>\@colht
+ \@testtrue
+ \fi
+ \if@test
+ \@cons\@failedlist #1%
+ \fl@trace{ --> fail}%
+ \else
+ \@ytryfc #1%
+ \fi
+}%
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+%
+%
+% \begin{macro}[internal]{\@ytryfc}
+%
+% The command \cs{@ytryfc}, which is also part of the code in the
+% kernel, loops through the defer list and tries to build a float
+% page starting with the float passed to it in |#1|. If it succeeds,
+% the floats that are part of the float page are listed in
+% \cs{@flsucceed} and the switch \cs[no-index]{if@fcolmade} is set to
+% \texttt{true}. Also of interest to us is that inside the code
+% \cs[no-index]{@tempdima} holds the size taken up by the floats, so we can
+% use this to calculate the unused space on the float page and
+% store it in \cs{fp@unused@space} for use in our extended
+% algorithm.
+% \begin{macrocode}
+\def\@ytryfc #1{%
+ \begingroup
+ \gdef\@flsucceed{\@elt #1}%
+ \global\let\@flfail\@empty
+ \@tempdima\ht #1%
+ \let\@elt\@ztryfc
+ \@trylist
+ \ifdim \@tempdima >\@fpmin
+ \global\@fcolmadetrue
+% \end{macrocode}
+% This branch is executed when the floats together are big enough
+% to form a float page. Thus, this is the right place to calculate
+% the free space by subtracting the used space from the column
+% height (which may not be the full height if there are spanning
+% floats in two column mode).
+% \begin{macrocode}
+ \@tempdimb\@colht
+ \advance\@tempdimb-\@tempdima
+ \xdef\fp@unused@space{\the\@tempdimb}%
+% \end{macrocode}
+% The remaining code is again unchanged except that we added two
+% additional tracing lines (though those should be added to
+% the \pkg{fltrace} package too one of these days).
+% \begin{macrocode}
+ \else
+ \@cons\@failedlist #1%
+ \fl@trace{ --> fail}%
+ \fi
+ \endgroup
+ \if@fcolmade
+ \let\@elt\@gobble
+ \fl@trace{ --> success: \@flsucceed}%
+ \fi}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+% \begin{macro}[internal]{\@largefloatcheck}
+%
+% The final kernel macro we need to patch is
+% \cs{@largefloatcheck}. This is called when a float box is
+% constructed and it checks if that box is larger than the available
+% \cs{textheight}, which would mean it could never be placed
+% anywhere, not even on a float page. The code therefore reduces
+% the box size as necessary and issues a warning.
+%
+% This macro is therefore a natural candidate to also check if the
+% float size is too large for the float to go into top or bottom
+% areas (if the option \option{checktb} is used).
+% \begin{macrocode}
+\def \@largefloatcheck{%
+ \ifdim \ht\@currbox>\textheight
+ \@tempdima -\textheight
+ \advance \@tempdima \ht\@currbox
+ \@latex@warning {Float too large for page by \the\@tempdima}%
+ \ht\@currbox \textheight
+ \fi
+% \end{macrocode}
+% The \cs{fp@maybe@check@tb} does the checking (or nothing if the
+% option is not given).
+% \begin{macrocode}
+ \fp@maybe@check@tb
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+%
+% \subsection{Internal helper commands and parameters}
+%
+%
+% \begin{macro}[internal]{\fp@candidates}
+% We use an internal counter to count the number of floats in the
+% defer list and on a float page under construction.
+% \begin{macrocode}
+\newcount\fp@candidates
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}[internal]{\fp@unused@space}
+% In \cs{fp@unused@space} we store the amount of free space
+% on the current float page.
+% \begin{macrocode}
+\def\fp@unused@space{}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}[internal]{\fp@analyse@floats@for@unraveling}
+% With \cs{fp@analyse@floats@for@unraveling} we loop over the
+% floats on the float page, i.e., |#1| will be one such float.
+%
+% One of its tasks is to count the floats (in \cs{fp@candidates}) and
+% check if
+% there are at least \ctr{floatpagekeeplimit} of them (which means
+% the float page should definitely be kept).
+%
+% Its most important task, however, is to check if one of the floats
+% has only a \texttt{p} specifier but no other. In that case it is
+% essential that we not unravel the float page because such a
+% float would then only go back onto the defer list as it has no
+% place to go except a float page.
+% \begin{macrocode}
+\def\fp@analyse@floats@for@unraveling#1{%
+ \advance\fp@candidates\@ne
+ \ifnum \fp@candidates <\c@floatpagekeeplimit
+% \end{macrocode}
+% So far we haven't got enough floats to know that this float page
+% should be kept so we check the given float specifiers.
+%
+% The test may look a little weird,\footnote{\enquote{Little} might
+% be an understatement. Encoding a lot of information in individual
+% bits of the counter value associated with a float was a great way
+% in the early days of \LaTeX{} to preserve macro space (and
+% absolutely essential back then), but these days \ldots{} Anyway,
+% it is the way it is and that part can't really be changed without
+% breaking a lot of packages.} but what we want to know is this:
+% is there a \texttt{p} (third bit) but neither a \texttt{b}
+% (second bit) nor a \texttt{t} (first bit). We don't care about
+% \texttt{h} or \texttt{!} which are the next two bits in the float
+% counter nor any of its higher bits (which encode the type of
+% float). So we divide the integer number by 8, which drops
+% the two least significant bits (think of the integer
+% represented in binary format), and then multiply it again by 8. As
+% a result the first two bits are zeroed out. We then compare the
+% result with the original value and if the two values are the same
+% then the \texttt{b} and \texttt{t} bits must both have been zero
+% from the start. And since the float was on a float page we also
+% know that it had a \texttt{p} specifier.
+% \begin{macrocode}
+ \@tempcntb\count#1%
+ \divide\@tempcntb 8\relax
+ \multiply\@tempcntb 8\relax
+ \ifnum \count#1=\@tempcntb
+% \end{macrocode}
+% In that case we set \cs[no-index]{if@fcolmade} to \texttt{true}
+% to signal that this float page should be kept, generate a tracing
+% message and change \cs[no-index]{@elt} to become
+% \cs[no-index]{@gobble} to quickly jump over any remaining floats
+% in the loop without doing further tests or generate further
+% tracing messages.
+% \begin{macrocode}
+ \global \@fcolmadetrue
+ \fl@trace{----- current float page kept, contains a float}%
+ \fl@trace{\@spaces\space\space with p but no t or b specifier}%
+ \let\@elt\@gobble
+ \fi
+% \end{macrocode}
+% On the other hand, if we have seen enough floats we also know
+% that the float page should be kept, so change the switch, give
+% some tracing info and stop checking:
+% \begin{macrocode}
+ \else
+ \global \@fcolmadetrue
+ \fl@trace{----- current float page kept
+ (contains at least \the\fp@candidates\space floats)}%
+ \let\@elt\@gobble
+ \fi
+}
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+% \begin{macro}[internal]{\fp@maybe@add@bang}
+%
+% The helper \cs{fp@maybe@add@bang} is used to loop through all of
+% the floats of a float page (receiving each as |#1| in turn) and
+% add a \texttt{!}\@ specifier if there wasn't one before.
+%
+% However, we only define it if we implement strategy 1 which is
+% option \option{addbang}.
+% \begin{macrocode}
+\ifnum\fp@strategy=1
+ \def\fp@maybe@add@bang#1{%
+% \end{macrocode}
+% Find out if the fourth bit is set (which means no \texttt{!}\@)
+% and if so subtract 16 from the float counter which means setting
+% it to zero.
+% \begin{macrocode}
+ \@boxfpsbit #1\sixt@@n
+ \ifodd \@tempcnta
+ \global\advance\count#1-\sixt@@n
+ \fi
+ }
+\else
+ \let\fp@maybe@add@bang\@gobble
+\fi
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+%
+% \begin{macro}[internal]{\fp@maybe@check@tb}
+% The code in \cs{fp@maybe@check@tb} is used in
+% \cs{@largefloatcheck} to test if the float has a \texttt{t} or
+% \texttt{b} specifier but is too large to fit into the
+% respective area. This test is not made by default but only if the
+% option \option{checktb} is used, i.e., strategy~2.
+% \begin{macrocode}
+\ifnum\fp@strategy=2
+ \def\fp@maybe@check@tb{%
+% \end{macrocode}
+% Again this is a case of
+% looking at various bits in the float counter value in binary
+% notation.
+% If the specifier contained a \texttt{!}\@ we are ok and it would
+% be wrong to change the specifier, because in
+% that case size restrictions for areas do not apply. For this we
+% have to test the fourth bit which means dividing by 16 and then
+% checking if the result is odd or even (odd means there was no
+% \texttt{!}\@).\footnote{I'm sure we had good reasons to
+% implement it this way in 1992\Dash we probably saved a few bytes
+% which was important back then. But it is certainly odd that for
+% \texttt{!}\@ a value of zero means that it was specified on the
+% float while for all other specifiers a value of \texttt{1}
+% indicates that the specifier was given.} The kernel
+% \cs{@getfpsbit} does this for us and stores the result in
+% \cs[no-index]{@tempcnta} so we can test this with \cs[no-index]{ifodd} to see if the
+% bit was set.
+% \begin{macrocode}
+ \@getfpsbit \sixt@@n
+ \ifodd \@tempcnta
+% \end{macrocode}
+% If there was no \texttt{!}\@ we check if the height of the
+% float is too large to fit into the top area.
+% \begin{macrocode}
+ \ifdim \ht\@currbox>\topfraction\textheight
+% \end{macrocode}
+%
+% If that is the case we also check the first bit of the float
+% counter to see if a \texttt{t} was specified. For this we use
+% \cs{@getfpsbit} again but this time with \texttt{2} as the argument
+% since we test the first bit.
+% \begin{macrocode}
+ \@getfpsbit \tw@
+ \ifodd \@tempcnta
+% \end{macrocode}
+% If \texttt{t} was specified we need to remove it (next line) and
+% add (if not already present) a \texttt{p} instead. This is done
+% by \cs[no-index]{fp@add@p@bit}. Finally we add a warning for the user about
+% the change.
+% \begin{macrocode}
+ \global\advance\count\@currbox -\tw@
+ \fp@add@p@bit
+ \@latex@warning {Float too large for top area: t changed to p}%
+ \fi
+ \fi
+% \end{macrocode}
+% A similar test and action is needed for bottom floats; here we
+% need to look at and zero out the second bit (i.e., using 4 as a value).
+% \begin{macrocode}
+ \ifdim \ht\@currbox>\bottomfraction\textheight
+ \@getfpsbit 4\relax
+ \ifodd \@tempcnta
+ \global\advance\count\@currbox -4\relax
+ \fp@add@p@bit
+ \@latex@warning {Float too large for bottom area:
+ b changed to p}%
+ \fi
+ \fi
+ \fi
+ }
+% \end{macrocode}
+% In all other cases \cs{fp@maybe@check@tb} does nothing.
+% \begin{macrocode}
+\else \let\fp@maybe@check@tb\relax \fi
+% \end{macrocode}
+% \end{macro}
+%
+%
+%
+% \begin{macro}[internal]{\fp@add@p@bit}
+% The command \cs{fp@add@p@bit} adds the \texttt{p} specifier which
+% means checking the third bit and if not set, adding 8 to the float counter.
+% \begin{macrocode}
+\def\fp@add@p@bit{%
+ \@getfpsbit 8\relax
+ \ifodd \@tempcnta \else \global\advance\count\@currbox 8\relax \fi}
+% \end{macrocode}
+% \end{macro}
+%
+%
+% \ifx\thisissuepageref\undefined ^^A is this TUB production ??? if not gen index
+% \subsection{Patches that will eventually go into \pkg{fltrace}}
+%
+% The \pkg{fewerfloatpages} package added some additional general
+% tracing info into some of the kernel functions which isn't
+% currently available when using only the \pkg{fltrace} package. As
+% that tracing info is generally useful for understanding what the
+% base part of the float algorithm does, it should also be added to
+% the latter package.
+%
+% \fi
+%
+% \begin{macrocode}
+%<*package>
+% \end{macrocode}
+% \Finale
+%
+
+
+\endinput