summaryrefslogtreecommitdiff
path: root/macros/latex/contrib/everyhook/everyhook.dtx
blob: bb62f32b53538c6eff2e080641f5ed336fba040e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
% \iffalse The license starting three lines down applies to this file
%<*batchfile>
\begingroup\input docstrip \preamble
Copyright (C) 2010, 2011, 2014 by Stephen Checkoway

This file may be distributed and/or modified under the
conditions of the LaTeX Project Public License, either
version 1.3c of this license or (at your option) any later
version.  The latest version of this license is in:

    http://www.latex-project.org/lppl.txt

and version 1.3c or later is part of all distributions of
LaTeX version 2005/12/01 or later.

This work has the LPPL maintenance status 'maintained'.

The Current Maintainer of this work is Stephen Checkoway.

This work consists of everyhook.dtx and the derived file
everyhook.sty.
\endpreamble
\keepsilent
\usedir{tex/latex/everyhook}
\askforoverwritefalse
\generate{\file{\jobname.sty}{\from{\jobname.dtx}{}}}
\endgroup

\documentclass{ltxdoc}
\usepackage{fixltx2e}
\usepackage{etoolbox}
\usepackage[osf]{mathpazo}
\usepackage[scaled=0.86]{berasans}
\usepackage[scaled=1.03]{inconsolata}
\usepackage[T1]{fontenc}
\usepackage{microtype}
\usepackage[margin=1.5in]{geometry}
\usepackage[excludeor]{everyhook}
\usepackage{enumitem}
\usepackage[pdfborder={0 0 0}]{hyperref}
\usepackage{ifpdf}
\usepackage{listings}
\usepackage{lipsum}
\begingroup
\catcode`\^^09\active
\gdef\obeytabs{%
\catcode`\^^09\active
\def^^09{\ \ \ \ \ \ \ \ }%
}
\endgroup
\makeatletter
\patchcmd\macrocode{\@vobeyspaces}{\@vobeyspaces\obeytabs}{}{\undefined}
\makeatother

\CheckSum{190}
\CharacterTable
 {Upper-case    \A\B\C\D\E\F\G\H\I\J\K\L\M\N\O\P\Q\R\S\T\U\V\W\X\Y\Z
  Lower-case    \a\b\c\d\e\f\g\h\i\j\k\l\m\n\o\p\q\r\s\t\u\v\w\x\y\z
  Digits    \0\1\2\3\4\5\6\7\8\9
  Exclamation   \!     Double quote  \"     Hash (number) \#
  Dollar    \$     Percent       \%     Ampersand     \&
  Acute accent  \'     Left paren    \(     Right paren   \)
  Asterisk      \*     Plus      \+     Comma     \,
  Minus     \-     Point     \.     Solidus       \/
  Colon     \:     Semicolon     \;     Less than     \<
  Equals    \=     Greater than  \>     Question mark \?
  Commercial at \@     Left bracket  \[     Backslash     \\
  Right bracket \]     Circumflex    \^     Underscore    \_
  Grave accent  \`     Left brace    \{     Vertical bar  \|
  Right brace   \}     Tilde     \~}

\EnableCrossrefs
\CodelineIndex
\RecordChanges
\GetFileInfo{\jobname.sty}
\title{The \textsf{\jobname} package\thanks{This document
corresponds to \textsf{\jobname}~\fileversion, dated \filedate.}}
\author{Stephen Checkoway\\\texttt{s@cs.jhu.edu}}

\lstset{language=[LaTeX]TeX,basicstyle=\ttfamily,
texcsstyle=*\normalfont\bfseries,
moretexcs={paragraph,RequirePackage},xleftmargin=\parindent}

\renewcommand*\arg[1]{\textsf{\{#1\}}}
\makeatletter
\renewcommand*\meta@font@select{\normalfont\itshape}
% \DescribeOption taken from trivfloat.dtx
\newcommand*{\DescribeOption}{%
  \leavevmode
  \@bsphack
  \begingroup
    \MakePrivateLetters
    \Describe@Option
}
\newcommand*{\Describe@Option}[1]{%
    \endgroup
  \marginpar{%
    \raggedleft
    \PrintDescribeEnv{#1}%
  }%
  \@esphack
  \ignorespaces
}
\makeatother
\begin{document}
\maketitle

\begin{abstract}
The \textsf{\jobname} package takes control of the six \TeX\
token parameters \cs{everypar}, \cs{everymath}, \cs{everydisplay},
\cs{everyhbox}, \cs{everyvbox}, and \cs{everycr}. Real hooks for
each of these can be installed using a stack like interface. For
compatibility with \LaTeX\ standard classes and packages, each of
the \cs{everyX} token lists can be set without interfering with the
hooks.
\end{abstract}
\tableofcontents

\section{Introduction}
\TeX\ contains nine token parameters, seven of which are inserted
into the current list at various times. Quoting from \textit{The
\TeX book}, the seven token parameters of interest are\footnote{The remaining two
token parameters are \cs{output} and \cs{errhelp}.}
\begin{description}[labelindent=1em, noitemsep]
\item{\cs{everypar}\enskip} tokens to insert when a paragraph begins,
\item{\cs{everymath}\enskip} tokens to insert when math in text begins,
\item{\cs{everydisplay}\enskip} tokens to insert when display math begins,
\item{\cs{everyhbox}\enskip} tokens to insert when an hbox begins,
\item{\cs{everyvbox}\enskip} tokens to insert when a vbox begins,
\item{\cs{everyjob}\enskip} tokens to insert when the job begins, and
\item{\cs{everycr}\enskip} tokens to insert after every \cs{cr} or
nonredundant \cs{crcr}.
\end{description}
Of these, \cs{everyjob} is not very useful outside of INITEX and so
it won't be considered further.

The remaining six token parameters can be used to great effect. For
example, the \cs{everypar} is used in \cs{paragraph} to set the title
of the paragraph inline allowing constructions like\\
\indent\hbox to.45\textwidth{%
\begin{lstlisting}[boxpos=b]
\paragraph{Paragraph title.}

A blank line followed by
the rest of the paragraph.
\end{lstlisting}\hfil
}
\hfill
\parbox[b]{.45\textwidth}{
\paragraph{Paragraph title.}

\strut A blank line followed by the rest of the paragraph.
\\[\baselineskip]
}\\[\baselineskip]
which work properly rather than starting a new paragraph due to the
blank line.

Similarly, \cs{everymath} and \cs{everydisplay} are used by the
\LaTeX\ kernel to set up math fonts.

Using the \TeX\ primitives directly has the major downside that they
cannot be used by multiple packages at the same time. Setting
\cs{everypar} overwrites a prior usage. Even if one package is careful
and always uses
\begin{lstlisting}
\everypar=\expandafter{\the\everypar new tokens here}
\end{lstlisting}
so as not to stomp on another's usage, there's no guarantee that the
other package will not later set \lstinline!\everypar={}!.

To get around this, the \textsf{\jobname} package takes control of the
six \cs{everyX} primitives listed above and for each one provides a
stack like interface for two additional token lists, one to be
expanded before the \cs{everyX} and one to be expanded after. For
example,
\begin{lstlisting}
\PushPreHook{hbox}{1}
\PushPreHook{hbox}{2}
\everyhbox={3}
\PushPostHook{hbox}{4}
\PushPostHook{hbox}{5}
\end{lstlisting}
will cause the insertion of the tokens |21345| at the start of an
\cs{hbox}. Note that \cs{PushPreHook} adds tokens to the \emph{left}
of the list of tokens to appear before those in \cs{everyhbox} whereas
\cs{PushPostHook} adds tokens to the \emph{right} of the list of
tokens to appear after those in \cs{everyhbox}.

\section{Usage}
The \textsf{\jobname} package has one (rather experimental) option,
|excludeor| and is loaded using
\begin{lstlisting}
\usepackage[excludeor]{everyhook}
\end{lstlisting}
or
\begin{lstlisting}
\RequirePackage[excludeor]{everyhook}
\end{lstlisting}
as required where the option is, of course, optional.

\subsection{Options}
\DescribeOption{excludeor}
Some of the hooks described below can cause unwanted behavior when
active during the execution of \LaTeX's output routine. The
experimental |excludeor| option saves and clears the hooks at
the beginning of the output routine and restores them at the end.

\subsection{Manipulating hooks}
There are 12 hooks, a pre and post hook for each of the six token
parameters |par|, |math|, |display|, |hbox|, |vbox|, and |cr|. The
first argument to all of the macros described in this section must be
one of these six. \textbf{All hook manipulation is \emph{global}.}

\paragraph{Pre hooks.}
\DescribeMacro{\PushPreHook}
\DescribeMacro{\PopPreHook}
Additional tokens \meta{balanced text} are prepended to the pre hook
\meta{hook} using \cs{PushPreHook}\arg{\meta{hook}}\arg{\meta{balanced
text}}. The most recently pushed tokens can be popped off using
\cs{PopPreHook}\arg{\meta{hook}}.

\paragraph{Post hooks.}
\DescribeMacro{\PushPostHook}
\DescribeMacro{\PopPostHook}
Additional tokens \meta{balanced text} are appended to the post hook
\meta{hook} using
\cs{PushPostHook}\arg{\meta{hook}}\arg{\meta{balanced text}}. The most
recently pushed tokens can be popped off using
\cs{PopPostHook}\arg{\meta{hook}}.

\paragraph{Saving, restoring, and clearing hooks.}
\DescribeMacro{\SavePreHook}
\DescribeMacro{\SavePostHook}
\DescribeMacro{\RestorePreHook}
\DescribeMacro{\RestorePostHook}
\DescribeMacro{\ClearPreHook}
\DescribeMacro{\ClearPostHook}
Each of the 12 pre and post hooks can be saved to a macro, restored
from a macro, or cleared independently. To save the pre hook
\meta{hook} to the macro \cs{cs}, use
\cs{SavePreHook}\arg{\meta{hook}}\arg{\cs{cs}}. Restoring is
accomplished by \cs{RestorePreHook}\arg{\meta{hook}}\arg{\cs{cs}}. To
clear all of the tokens in a pre hook use
\cs{ClearPreHook}\arg{\meta{hook}}. The \cs{SavePostHook},
\cs{RestorePostHook}, and \cs{ClearPostHook} are analogous.

\section{Example}
As a nontrivial example of where this package can be used, consider
the following example.
\begin{lstlisting}
\documentclass{article}
\usepackage{everyhook}
\usepackage{lipsum}

\begin{document}
\setlength{\parindent}{0pt}
\PushPreHook{par}{\llap{\textbullet\enskip}\null}
\paragraph{Lorem ipsum.}
\lipsum[1-4]
\PopPreHook{par}
\end{document}
\end{lstlisting}
This code will cause each paragraph of the \emph{lorem ipsum} text to
have no indentation and instead to place a bullet in the margin. See
Figure~\ref{fig:example}. If \cs{everypar} were used instead, the
\cs{paragraph} would replace the command to create the bullet with
those needed to typeset the paragraph title.

\begin{figure}[p]
\centering
\fbox{\makebox[.975\textwidth][c]{\parbox{\dimexpr.975\textwidth-1in\relax}{
\vspace*{\dimexpr .5in-3.25ex}
\PushPreHook{par}{\llap{\textbullet\enskip}\null}
\paragraph{Lorem ipsum.}
\lipsum[1-4]
\PopPreHook{par}

\vskip.5in
}}}
\caption{Example output.}
\label{fig:example}
\end{figure}

Note that this package is not a panacea. We had to add a \cs{null} to
the |par| hook because \cs{paragraph} uses \cs{lastbox} to remove the
indentation box. Without the \cs{null} it ends up removing the box
constructed by \cs{llap} instead.

Using the post |par| hook solves the \cs{lastbox} problem, but then
the bullet is placed to the right of the \cs{paragraph} title.

Perhaps a better way to solve this problem is to remove the
indentation box first, insert the bullet, and then place the box
after. In this way, the bullet is always to the left of the
paragraph indentation.
\begin{lstlisting}
\PushPreHook{par}{{\setbox0=\lastbox
	\llap{\textbullet\enskip}\box0}}
\end{lstlisting}

\section{Potential pitfalls}
As noted in the previous section, it can be tricky to use the |par|
hook correctly. This section contains an (almost certainly) incomplete
list of pitfalls to watch out for when using \textsf{\jobname}.
\begin{enumerate}
\item When using the |par| hooks, be aware that TeX will insert a box
with the width of \cs{parindent} before the tokens in the pre hook.
One way to handle this is to propogate the box to the right.
\item It is probably not a good idea to use the |hbox|, |vbox|, and
|par| hooks at any place where TeX's output routine is likely to run.
The |excludeor| option \emph{should} help with this, but it might
cause problems with other packages that also modify the output
routine.
\item \LaTeX's kernel takes control of the \cs{everymath} and
\cs{everydisplay} token parameters to make its own adjustments in much
the same way this package does. The \textsf{trace} package uses the
kernel's private macros to insert its own hooks. It is probably best
to only use the post |math| and |display| hooks to ensure that the
kernel has done what it needs to do before you start typesetting stuff
in math mode.
\item When using the |hbox| and |vbox| hooks, any hbox or vbox that
appears in a \cs{setbox} will have the \cs{afterassignment} token
inserted \emph{before} the hooks. This is no different from TeX's
normal behavior with \cs{afterassignment} and
\cs{everyhbox}/\cs{everyvbox}, but can be surprising.
\item I'm sure there are others.
\end{enumerate}

\StopEventually{
	\typeout{**************************************************}
	\typeout{*}
	\typeout{* To finish the installation, you have to move the}
	\typeout{* following file into a directory searched by TeX:}
	\typeout{*}
	\typeout{* \space\space \jobname.sty}
	\typeout{*}
	\typeout{* Documentation is in \jobname.\ifpdf pdf\else dvi\fi.}
	\typeout{*}
	\typeout{* Happy TeXing!}
	\typeout{**************************************************}
	\end{document}
}

\clearpage
\DocInput{\jobname.dtx}
\clearpage
\phantomsection
\addcontentsline{toc}{section}{Change History}%
\PrintChanges
\phantomsection
\addcontentsline{toc}{section}{Index}%
\PrintIndex
\Finale
%</batchfile>
% \fi
% \DoNotIndex{\csdef,\cslet,\csname,\csuse,\def,\endcsname,\endinput,
% \every,\expandafter,\gdef,\global,\ifcsdef,\ifcsempty,\ifdefequal,
% \letcs,\newrobustcmd,\newtoks,\PackageError,\protect,\RequirePackage,
% \space,\the,\undef}
%
% \section{Implementation}
% The package begins with the usual package identification and then it
% declares the one option |excludeor| and finally it loads the
% \textsf{etoolbox} package. This package is not strictly necessary,
% but it does simplify some stuff and provides handy macros for
% dealing with control sequence names.
%
% \changes{v1.0}{2010/09/26}{Initial version}
% \changes{v1.1}{2011/02/03}{Add excludeor}
% \changes{v1.2}{2014/11/26}{Let everyX be redefined}
%    \begin{macrocode}
\NeedsTeXFormat{LaTeX2e}[1999/12/01]
\RequirePackage{svn-prov}
\ProvidesPackageSVN
	{$Id: everyhook.dtx 12 2014-11-26 15:34:56Z steve $}
	[v1.2 \revinfo\ Hooks for low level TeX everyX primitives.]
\DeclareOption{excludeor}{%
	\AtBeginDocument{%
		\output\expandafter{%
			\expandafter\eh@saveclearallhooks
			\the\output
			\eh@restoreallhooks
		}%
	}%
}
\ProcessOptions\relax
\RequirePackage{etoolbox}
%    \end{macrocode}
%
% \begin{macro}{\eh@definehook}
% This performs all of the setup work for each hook. First, it takes
% control of \TeX's token parameter given in the second argument. Then
% it shadows the name of the primitive with a normal token register (and
% copies the current definition). The pre and post hooks are defined
% to be initially empty.
%    \begin{macrocode}
\def\eh@definehook#1#2{%
	\cslet{eh@every#1}#2%
	\newtoks#2%
	\cslet{eh@private#1}#2%
	#2\csuse{eh@every#1}%
	\csdef{eh@pre#1}{}%
	\csdef{eh@post#1}{}%
%    \end{macrocode}
% This is slightly tricky to get right. Basically, we want to set the
% \cs{everyfoo} primitive which we have saved as \cs{eh@everyfoo}
% like
%
% \indent\lstinline!\eh@everyfoo={\eh@prefoo\the\expandafter\everyfoo\eh@postfoo}!.
%
% The reason for the \cs{expandafter} is to make sure it is expanded
% before the the token register \cs{everyfoo} is expanded. Thus if the
% post hook is empty, then code in \cs{everyfoo} sees no additional
% tokens, in case that is important.
%
% Unfortunately, some code wants to redefine \cs{everyfoo} itself in
% order to prevent \emph{other} code that uses \cs{everyfoo} from
% actually setting anything. To deal with that, we use the private
% token list
%
% \indent\lstinline!\eh@everyfoo{\eh@prefoo\the\expandafter\eh@privatefoo\eh@postfoo}!
%    \begin{macrocode}
	\csuse{eh@every#1}\expandafter{\csname eh@pre#1\expandafter\endcsname
		\expandafter\the\csname eh@private#1\expandafter\endcsname
		\csname eh@post#1\endcsname}%
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\everypar}
% Define the hooks for the |par| hook.
%    \begin{macrocode}
\eh@definehook{par}\everypar
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\frozen@everymath}
% \begin{macro}{\frozen@everydisplay}
% Define the |math| and |display| hooks. Since the \LaTeX\ kernel has
% already saved \cs{everymath} and \cs{everydisplay} into the frozen
% macros, we take control by redefining the frozen ones instead.
%    \begin{macrocode}
\eh@definehook{math}\frozen@everymath
\eh@definehook{display}\frozen@everydisplay
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\everyhbox}
% \begin{macro}{\everyvbox}
% \begin{macro}{\everycr}
% Define the |hbox|, |vbox|, and |cr| hooks and free up some used
% memory.
%    \begin{macrocode}
\eh@definehook{hbox}\everyhbox
\eh@definehook{vbox}\everyvbox
\eh@definehook{cr}\everycr
\undef\eh@definehook
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\eh@hookseparator}
% An separator used to separate tokens in each hook.
%    \begin{macrocode}
\def\eh@hookseparator{}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\eh@checkhook}
% Check that the hook is one of the six.
%    \begin{macrocode}
\def\eh@checkhook#1#2{%
	\ifcsdef{eh@every#1}{}{\PackageError{everyhook}{Argument #1 to
	\protect#2\space is invalid}{There is no hook for
	\protect\every#1.}}%
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\eh@checkhooknotempty}
% Check that the hook is both defined and not empty so that we can
% pop.
%    \begin{macrocode}
\def\eh@checkhooknotempty#1#2#3{%
	\eh@checkhook{#2}#3%
	\ifcsempty{eh@#1#2}{\PackageError{everyhook}{The #1 hook for
	\protect\every#2\space is empty}{I have seen too many
	\protect#3{#2}s.}{}}%
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\PushPreHook}
% Prepend tokens to the pre hook, separated via the separator.
%    \begin{macrocode}
\newrobustcmd\PushPreHook[2]{%
	\eh@checkhook{#1}\PushPreHook
	\def\eh@tempi{#2}%
	\letcs\eh@tempii{eh@pre#1}%
	\expandafter\gdef\csname eh@pre#1\expandafter\expandafter
		\expandafter\endcsname\expandafter\expandafter
		\expandafter{\expandafter\eh@tempi\expandafter
		             \eh@hookseparator\eh@tempii}%
	\undef\eh@tempi
	\undef\eh@tempii
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\PopPreHook}
% \begin{macro}{\eh@popprehook}
% Check that the hook is not empty, and then pop off the left tokens
% and separator. We can use delimited parameters to strip off the
% first set of tokens.
%    \begin{macrocode}
\newrobustcmd\PopPreHook[1]{%
	\eh@checkhooknotempty{pre}{#1}\PopPreHook
	\expandafter\eh@popprehook\csname eh@pre#1\expandafter
		\expandafter\expandafter\endcsname
		\csname eh@pre#1\endcsname\eh@hookend
}
\def\eh@popprehook#1#2\eh@hookseparator#3\eh@hookend{\gdef#1{#3}}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\PushPostHook}
% Append a separator and tokens to the post hook.
%    \begin{macrocode}
\newrobustcmd\PushPostHook[2]{%
	\eh@checkhook{#1}\PushPostHook
	\letcs\eh@tempi{eh@post#1}%
	\expandafter\gdef\csname eh@post#1\expandafter\endcsname
		\expandafter{\eh@tempi\eh@hookseparator#2}%
	\undef\eh@tempi
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\PopPostHook}
% \begin{macro}{\eh@popposthook}
% \begin{macro}{\eh@sentinel}
% Check that the post hook is not empty. Then, iterate over the tokens
% in the list until we reach the end and strip that off.
%    \begin{macrocode}
\newrobustcmd\PopPostHook[1]{%
	\eh@checkhooknotempty{post}{#1}\PopPostHook
	\letcs\eh@tempi{eh@post#1}%
	\expandafter\eh@popposthook\csname eh@post#1\expandafter
		\endcsname\expandafter{\expandafter}\eh@tempi
		\eh@hookend\eh@hookseparator\eh@sentinel\eh@hookend
	\undef\eh@tempi
}
\def\eh@popposthook#1#2\eh@hookseparator#3\eh@hookseparator#4\eh@hookend{%
	\def\eh@tempi{#4}%
	\ifdefequal\eh@sentinel\eh@tempi%
		{\gdef#1{#2}\undef\eh@tempi}%
		{\eh@popposthook#1{#2\eh@hookseparator#3}\eh@hookseparator#4\eh@hookend}%
}
\def\eh@sentinel{\eh@sentinel}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\eh@clearhook}
% Internal hook reset.
%    \begin{macrocode}
\def\eh@clearhook#1{%
	\global\csdef{eh@#1}{}%
}
%    \end{macrocode}
% \end{macro}
% \begin{macro}{\ClearPreHook}
% \begin{macro}{\ClearPostHook}
% Reset the pre/post hook to empty.
%    \begin{macrocode}
\newrobustcmd\ClearPreHook[1]{%
	\eh@checkhook{#1}\ClearPreHook
	\eh@clearhook{pre#1}%
}
\newrobustcmd\ClearPostHook[1]{%
	\eh@checkhook{#1}\ClearPostHook
	\eh@clearhook{post#1}%
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\eh@savehook}
% \begin{macro}{\eh@restorehook}
% Internal macros to \cs{let} the hook to the supplied control
% sequence to save. Perform the \cs{let} in the other direction to
% restore.
%    \begin{macrocode}
\def\eh@savehook#1#2{%
	\letcs#2{eh@#1}%
}
\def\eh@restorehook#1#2{%
	\global\cslet{eh@#1}#2%
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \begin{macro}{\SavePreHook}
% \begin{macro}{\SavePostHook}
% \begin{macro}{\RestorePreHook}
% \begin{macro}{\RestorePostHook}
% User macros to save and restore hooks.
%    \begin{macrocode}
\newrobustcmd\SavePreHook[2]{%
	\eh@checkhook{#1}\SavePreHook
	\eh@savehook{pre#1}#2%
}
\newrobustcmd\SavePostHook[2]{%
	\eh@checkhook{#1}\SavePostHook
	\eh@savehook{post#1}#2%
}
\newrobustcmd\RestorePreHook[2]{%
	\eh@checkhook{#1}\RestorePreHook
	\eh@restorehook{pre#1}#2%
}
\newrobustcmd\RestorePostHook[2]{%
	\eh@checkhook{#1}\RestorePostHook
	\eh@restorehook{post#1}#2%
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
% \end{macro}
% \end{macro}
% \begin{macro}{\eh@saveclearallhooks}
% \begin{macro}{\eh@restoreallhooks}
% Internal macros to save and clear (resp.\ restore) all hooks at the
% start (resp.\ end) of the output routine.
%    \begin{macrocode}
\def\eh@saveclearallhooks{%
	\global\eh@savehook{prepar}\eh@or@prepar
	\global\eh@savehook{postpar}\eh@or@postpar
	\global\eh@savehook{premath}\eh@or@premath
	\global\eh@savehook{postmath}\eh@or@postmath
	\global\eh@savehook{predisplay}\eh@or@predisplay
	\global\eh@savehook{postdisplay}\eh@or@postdisplay
	\global\eh@savehook{prehbox}\eh@or@prehbox
	\global\eh@savehook{posthbox}\eh@or@posthbox
	\global\eh@savehook{prevbox}\eh@or@prevbox
	\global\eh@savehook{postvbox}\eh@or@postvbox
	\global\eh@savehook{precr}\eh@or@precr
	\global\eh@savehook{postcr}\eh@or@postcr
	\eh@clearhook{prepar}%
	\eh@clearhook{postpar}%
	\eh@clearhook{premath}%
	\eh@clearhook{postmath}%
	\eh@clearhook{predisplay}%
	\eh@clearhook{postdisplay}%
	\eh@clearhook{prehbox}%
	\eh@clearhook{posthbox}%
	\eh@clearhook{prevbox}%
	\eh@clearhook{postvbox}%
	\eh@clearhook{precr}%
	\eh@clearhook{postcr}%
}
\def\eh@restoreallhooks{%
	\eh@restorehook{prepar}\eh@or@prepar
	\eh@restorehook{postpar}\eh@or@postpar
	\eh@restorehook{premath}\eh@or@premath
	\eh@restorehook{postmath}\eh@or@postmath
	\eh@restorehook{predisplay}\eh@or@predisplay
	\eh@restorehook{postdisplay}\eh@or@postdisplay
	\eh@restorehook{prehbox}\eh@or@prehbox
	\eh@restorehook{posthbox}\eh@or@posthbox
	\eh@restorehook{prevbox}\eh@or@prevbox
	\eh@restorehook{postvbox}\eh@or@postvbox
	\eh@restorehook{precr}\eh@or@precr
	\eh@restorehook{postcr}\eh@or@postcr
}
\endinput
%    \end{macrocode}
% \end{macro}
% \end{macro}
\endinput