1 files changed, 1883 insertions, 1908 deletions

diff --git a/tex/context/base/supp-vis.tex b/tex/context/base/supp-vis.tex
index 54dc4779b..9a9d14ea9 100644
--- a/tex/context/base/supp-vis.tex
+++ b/tex/context/base/supp-vis.tex
@@ -1,1908 +1,1883 @@
-%D \module

-%D   [       file=supp-vis,

-%D        version=1996.10.21,

-%D          title=\CONTEXT\ Support Macros,

-%D       subtitle=Visualization,

-%D         author=Hans Hagen,

-%D           date=\currentdate,

-%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]

-%C

-%C This module is part of the \CONTEXT\ macro||package and is

-%C therefore copyrighted by \PRAGMA. Non||commercial use is 

-%C granted. 

-

-%D \gdef\ShowBufferedExample% private typeseting macro

-%D   {\startregelcorrectie

-%D    \bgroup

-%D    \steltypenin[marge=0pt,optie=kleur]

-%D    \showmakeup

-%D    \centeredvcuetrue

-%D    \dontinterfere

-%D    \baselinerulefalse

-%D    \normalvbox

-%D      {\normalhbox to \hsize

-%D         {$\hsize=.5\hsize

-%D          \advance\hsize by -.5em

-%D          \normalvcenter{\vbox{\haalbuffer}}\normalhss

-%D          \normalvcenter{\vbox{\dontshowcomposition\typebuffer}}$}}

-%D    \egroup

-%D    \stopregelcorrectie}

-%D

-%D \gdef\ShowBufferedExampleBox% private typeseting macro

-%D   {\startregelcorrectie

-%D    \bgroup

-%D    \steltypenin[marge=0pt,optie=kleur]

-%D    \showmakeup

-%D    \centeredvcuetrue

-%D    \dontinterfere

-%D    \baselinerulefalse

-%D    \normalvbox

-%D      {\normalhbox to \hsize

-%D         {$\hsize=.5\hsize

-%D          \advance\hsize by -.5em

-%D          \normalvcenter{\baselineruletrue\vbox{\haalbuffer}}\normalhss

-%D          \normalvcenter{\vbox{\dontshowcomposition\typebuffer}}$}}

-%D    \egroup

-%D    \stopregelcorrectie}

-

-%D Although an integral part of \CONTEXT, this module is one

-%D of the support modules. Its stand alone character permits

-%D use in \PLAIN\ \TEX\ or \TEX\ based macropackages.

-%D \ifCONTEXT \else If in some examples the verbatim listings

-%D don't show up nice, this is due to processing by a system

-%D that does not support buffering. In \CONTEXT\ we show the

-%D commands in the margin, use bit more advanced way of

-%D numbering, and typeset the source in \TEX nicolored

-%D verbatim. Sorry for this inconvenience.\fi 

-

-%D This module is still in development. Depending on my 

-%D personal need and those of whoever uses it, the macros will

-%D be improved in terms of visualization, efficiency and 

-%D compatibility.  

-

-\ifx \undefined \writestatus \input supp-mis.tex \fi

-

-%D One of the strong points of \TEX\ is abstraction of textual

-%D input. When macros are defined well and do what we

-%D want them to do, we will seldom need the tools present in

-%D What You See Is What You Get systems. For instance, when

-%D entering text we don't need rulers, because no manual

-%D shifting and/or alignment of text is needed. On the other

-%D hand, when we are designing macros or specifying layout

-%D elements, some insight in \TEX's advanced spacing, kerning,

-%D filling, boxing and punishment abilities will be handy.

-%D That's why we've implemented a mechanism that shows some of

-%D the inner secrets of \TEX.

-

-\writestatus{loading}{Context Support Macros / Visualization}

-

-%D In this module we are going to redefine some \TEX\

-%D primitives and \PLAIN\ macro's. Their original meaning is

-%D saved in macros with corresponding names, preceded by

-%D \type{normal}. These original macros are (1)~used to

-%D temporary restore the old values when needed and

-%D (2)~used to prevent recursive calls in the macros that

-%D replace them.

-

-\unprotect

-

-%D \macros

-%D   {dontinterfere}

-%D   {}

-%D

-%D Indentation, left and/or right skips, redefinition of

-%D \type{\par} and assignments to \type{\everypar} can lead to

-%D  unwanted results. We can therefore turn all those things

-%D off with \type{\dontinterfere}.

-

-\def\dontinterfere%

-  {\everypar  = {}%

-   \let\par   = \endgraf

-   \parindent = \!!zeropoint

-   \parskip   = \!!zeropoint

-   \leftskip  = \!!zeropoint

-   \rightskip = \!!zeropoint

-   \relax}

-

-%D \macros

-%D   {dontcomplain}

-%D   {}

-%D

-%D In this module we do a lot of box manipulations. Because we

-%D don't want to be confronted with to many over- and underfull

-%D messages we introduce \type{\dontcomplain}.

-

-\def\dontcomplain%

-  {\hbadness  = \!!tenthousand

-   \hfuzz     = \maxdimen

-   \vbadness  = \!!tenthousand

-   \vfuzz     = \maxdimen}

-

-%D \macros

-%D   {normaloffinterlineskip}

-%D   {}

-%D

-%D The next hack is needed because in \CONTEXT\ we redefine 

-%D \type{\offinterlineskip}.  

-

-\ifx\undefined\normaloffinterlineskip 

-  \let\normaloffinterlineskip=\offinterlineskip

-\fi

-

-%D \macros

-%D   {normalhbox,

-%D    normalvbox,normalvtop}

-%D   {}

-%D

-%D There are three types of boxes, one horizontal and two

-%D vertical in nature. As we will see later on, all three types

-%D are to be handled according to their orientation and

-%D baseline behavior. Especially \type{\vtop}'s need our

-%D special attention.

-

-\let\normalhbox     = \hbox

-\let\normalvbox     = \vbox

-\let\normalvtop     = \vtop

-\let\normalvcenter  = \vcenter

-

-%D \macros

-%D   {normalhskip,

-%D    normalvskip}

-%D   {}

-%D

-%D Next come the flexible skips, which come in two flavors

-%D too. Like boxes these are handled with \TEX\ primitives.

-

-\let\normalhskip    = \hskip

-\let\normalvskip    = \vskip

-

-%D \macros

-%D   {normalpenalty,

-%D    normalkern}

-%D   {}

-%D

-%D Both penalties and kerns are taken care of by mode sensitive

-%D primitives. This means that when making them visible, we

-%D have to take the current mode into account.

-

-\let\normalpenalty  = \penalty

-\let\normalkern     = \kern

-

-%D \macros

-%D   {normalhglue,

-%D    normalvglue}

-%D   {}

-%D

-%D Glues on the other hand are macro's defined in \PLAIN\ \TEX.

-%D As we will see, their definitions make the implementation of

-%D their visible counterparts a bit more \TeX{}nical.

-

-\let\normalhglue    = \hglue

-\let\normalvglue    = \vglue

-

-%D \macros

-%D   {normalmkern,

-%D    normalmskip}

-%D   {}

-%D

-%D Math mode has its own spacing primitives, preceded by

-%D \type{m}. Due to the relation with the current font and the

-%D way math is typeset, their unit \type{mu} is not compatible

-%D with other dimensions. As a result, the visual appearance

-%D of these primitives is kept primitive too.

-

-\let\normalmkern    = \mkern

-\let\normalmskip    = \mskip

-

-%D \macros

-%D   {hfilneg,

-%D    vfilneg}

-%D   {}

-%D

-%D Fills can be made visible quite easy. We only need some

-%D additional negation macros. Because \PLAIN\ \TEX\ only

-%D offers \type{\hfilneg} and \type{\vfilneg}, we define our

-%D own alternative double \type{ll}'ed ones.

-

-\def\hfillneg%

-  {\normalhskip\!!zeropoint \!!plus-1fill\relax}

-

-\def\vfillneg%

-  {\normalvskip\!!zeropoint \!!plus-1fill\relax}

-

-%D \macros

-%D   {normalhss,normalhfil,normalhfill,

-%D    normalvss,normalvfil,normalvfill}

-%D   {}

-%D

-%D The positive stretch primitives are used independant and in

-%D combination with \type{\leaders}.

-

-\let\normalhss      = \hss

-\let\normalhfil     = \hfil

-\let\normalhfill    = \hfill

-\let\normalvss      = \vss

-\let\normalvfil     = \vfil

-\let\normalvfill    = \vfill

-

-%D \macros

-%D   {normalhfilneg,normalhfillneg,

-%D    normalvfilneg,normalvfillneg}

-%D   {}

-%D

-%D Keep in mind that both \type{\hfillneg} and \type{\vfillneg}

-%D are not part of \PLAIN\ \TEX\ and therefore not documented

-%D in standard \TEX\ documentation. They can nevertheless be

-%D used at will.

-

-\let\normalhfilneg  = \hfilneg

-\let\normalhfillneg = \hfillneg

-\let\normalvfilneg  = \vfilneg

-\let\normalvfillneg = \vfillneg

-

-%D Visualization is not always wanted. Instead of turning this

-%D option off in those (unpredictable) situations, we just

-%D redefine a few \PLAIN\ macros.

-

-\def\rlap#1{\normalhbox to \!!zeropoint{#1\normalhss}}

-\def\llap#1{\normalhbox to \!!zeropoint{\normalhss#1}}

-

-\def~{\normalpenalty\!!tenthousand\ }

-

-%D \macros

-%D   {makeruledbox}

-%D   {}

-%D

-%D Ruled boxes can be typeset is many ways. Here we present

-%D just one alternative. This implementation may be a little 

-%D complicated, but it supports all three kind of boxes. The 

-%D next command expects a \BOX\ specification, like: 

-%D

-%D \starttypen

-%D \makeruledbox0

-%D \stoptypen

-

-%D \macros

-%D   {baselinerule,baselinefill}

-%D   {}

-%D

-%D We can make the baseline of a box visible, both dashed and

-%D as a rule. The line is drawn on top of the baseline. All 

-%D we have to say is:

-%D

-%D \starttypen

-%D \baselineruletrue

-%D \baselinefilltrue

-%D \stoptypen

-%D

-%D At the cost of some overhead these alternatives are

-%D implemented using \type{\if}'s:

-

-\newif\ifbaselinerule  \baselineruletrue

-\newif\ifbaselinefill  \baselinefillfalse

-

-%D \macros

-%D   {iftoprule,ifbottomrule,ifleftrule,ifrightrule}

-%D   {}

-%D

-%D Rules can be turned on and off, but by default we have:

-%D

-%D \starttypen

-%D \topruletrue

-%D \bottomruletrue

-%D \leftruletrue

-%D \rightruletrue

-%D \stoptypen

-%D

-%D As we see below:

-

-\newif\iftoprule       \topruletrue

-\newif\ifbottomrule    \bottomruletrue

-\newif\ifleftrule      \leftruletrue

-\newif\ifrightrule     \rightruletrue

-

-%D \macros

-%D   {boxrulewidth}

-%D   {}

-%D

-%D The width in the surrounding rules can be specified by

-%D assigning an apropriate value to the dimension used. This

-%D module defaults the width to:

-%D

-%D \starttypen

-%D \boxrulewidth=.2pt

-%D \stoptypen

-%D

-%D Although we are already low on \DIMENSIONS\ it's best to

-%D spend one here, mainly because it enables easy manipulation,

-%D like multiplication by a given factor.

-

-\newdimen\boxrulewidth \boxrulewidth=.2pt

-

-%D The core macro \type{\makeruledbox} looks a bit hefty. The

-%D manipulation at the end is needed because we want to

-%D preserve both the mode and the baseline. This means that

-%D \type{\vtop}'s and \type{\vbox}'es behave the way we expect

-%D them to do.

-%D

-%D \startregelcorrectie

-%D \hbox

-%D   {\ruledhbox to 5em{\strut test\normalhss}\hskip1em

-%D    \ruledvbox{\hsize 5em\strut test \par test\strut}\hskip1em

-%D    \ruledvtop{\hsize 5em\strut test \par test\strut}}

-%D \stopregelcorrectie

-%D

-%D The \type{\cleaders} part of the macro is responsible for

-%D the visual baseline. The \type{\normalhfill} belongs to this

-%D primitive too. By storing and restoring the height and depth

-%D of box \type{#1}, we preserve the mode.

-

-\def\makeruledbox#1%

-  {\edef\ruledheight{\the\ht#1}%

-   \edef\ruleddepth {\the\dp#1}%

-   \edef\ruledwidth {\the\wd#1}%

-   \setbox\scratchbox=\normalvbox

-     {\dontcomplain

-      \normaloffinterlineskip

-      \hrule

-        \!!height\boxrulewidth

-        \iftoprule\else\!!width\!!zeropoint\fi

-      \normalvskip-\boxrulewidth

-      \normalhbox to \ruledwidth

-        {\vrule

-           \!!height\ruledheight

-           \!!depth\ruleddepth

-           \!!width\ifleftrule\else0\fi\boxrulewidth

-         \ifdim\ruledheight>\!!zeropoint \else \baselinerulefalse \fi

-         \ifdim\ruleddepth>\!!zeropoint \else \baselinerulefalse \fi

-         \ifbaselinerule

-           \ifdim\ruledwidth<20\boxrulewidth

-             \baselinefilltrue

-           \fi

-           \cleaders

-             \ifbaselinefill

-               \hrule

-                 \!!height\boxrulewidth

-             \else

-               \normalhbox

-                 {\normalhskip2.5\boxrulewidth

-                  \vrule

-                    \!!height\boxrulewidth

-                    \!!width5\boxrulewidth

-                  \normalhskip2.5\boxrulewidth}%

-             \fi

-         \fi

-         \normalhfill

-         \vrule

-           \!!width\ifrightrule\else0\fi\boxrulewidth}%

-       \normalvskip-\boxrulewidth

-       \hrule

-         \!!height\boxrulewidth

-         \ifbottomrule\else\!!width\!!zeropoint\fi}%

-   \wd#1=\!!zeropoint

-   \setbox#1=\ifhbox#1\normalhbox\else\normalvbox\fi

-     {\normalhbox{\box#1\lower\ruleddepth\box\scratchbox}}%

-   \ht#1=\ruledheight

-   \wd#1=\ruledwidth

-   \dp#1=\ruleddepth}

-

-%D Just in case one didn't notice: the rules are in fact layed

-%D over the box. This way the contents of a box cannot

-%D visually interfere with the rules around (upon) it. A more

-%D advanced version of ruled boxes can be found in one of the 

-%D core modules of \CONTEXT. There we take offsets, color, 

-%D rounded corners, backgrounds and alignment into account too.

-

-%D \macros

-%D   {ruledhbox,

-%D    ruledvbox,ruledvtop,

-%D    ruledvcenter}

-%D   {}

-%D 

-%D These macro's can be used instead of \type{\hbox},

-%D \type{\vbox}, \type{\vtop} and, when in math mode,

-%D \type{\vcenter}. They just do what their names state. Using

-%D an auxiliary macro would save us a few words of memory, but

-%D it would make their appearance even more obscure. 

-%D 

-%D \startbuffer

-%D \hbox

-%D   {\strut

-%D    one

-%D    two

-%D    \hbox{three}

-%D    four

-%D    five}

-%D \stopbuffer

-%D

-%D \ShowBufferedExampleBox

-

-\unexpanded\def\ruledhbox%

-  {\normalhbox\bgroup

-   \dowithnextbox{\makeruledbox\nextbox\box\nextbox\egroup}%

-   \normalhbox}

-

-%D \startbuffer

-%D \vbox

-%D   {\strut

-%D    first line  \par

-%D    second line \par

-%D    third line  \par

-%D    fourth line \par

-%D    fifth line

-%D    \strut }

-%D \stopbuffer

-%D

-%D \ShowBufferedExampleBox

-

-\unexpanded\def\ruledvbox%

-  {\normalvbox\bgroup

-   \dowithnextbox{\makeruledbox\nextbox\box\nextbox\egroup}%

-   \normalvbox}

-

-%D \startbuffer

-%D \vtop

-%D   {\strut

-%D    first line  \par

-%D    second line \par

-%D    third line  \par

-%D    fourth line \par

-%D    fifth line

-%D    \strut }

-%D \stopbuffer

-%D

-%D \ShowBufferedExampleBox

-

-\unexpanded\def\ruledvtop%

-  {\normalvtop\bgroup

-   \dowithnextbox{\makeruledbox\nextbox\box\nextbox\egroup}%

-   \normalvtop}

-

-%D \startbuffer

-%D \hbox

-%D   {$\vcenter{\hsize.2\hsize 

-%D       alfa \par beta}$

-%D    $\vcenter to 3cm{\hsize.2\hsize 

-%D       alfa \par beta \par gamma}$

-%D    $\vcenter{\hsize.2\hsize 

-%D       alfa \par beta}$}

-%D \stopbuffer

-%D

-%D \ShowBufferedExampleBox

-

-\unexpanded\def\ruledvcenter%

-  {\normalvbox\bgroup

-   \dontinterfere

-   \dowithnextbox

-     {\scratchdimen=.5\ht\nextbox

-      \advance\scratchdimen by .5\dp\nextbox

-      \ht\nextbox=\scratchdimen

-      \dp\nextbox=\scratchdimen

-      \ruledhbox{\box\nextbox}%

-      \egroup}%

-   \normalvbox}

-

-%D \macros

-%D   {ruledbox,

-%D    setruledbox}

-%D   {}

-%D

-%D Of the next two macros the first can be used to precede a

-%D box of ones own choice. One can for instance prefix boxes

-%D with \type{\ruledbox} and afterwards --- when the macro

-%D satisfy the needs --- let it to \type{\relax}.

-%D

-%D \starttypen

-%D \ruledbox\hbox{What rules do you mean?}

-%D \stoptypen

-%D

-%D The macro \type{\setruledbox} can be used to directly

-%D rule a box.

-%D

-%D \starttypen

-%D \setruledbox12=\hbox{Who's talking about rules here?}

-%D \stoptypen

-%D

-%D At the cost of some extra macros we can implement a

-%D variant that does not need the~\type{=}, but we stick to:

-

-\unexpanded\def\ruledbox%

-  {\dowithnextbox{\makeruledbox\nextbox\box\nextbox}}

-

-\def\setruledbox#1=%

-  {\dowithnextbox{\makeruledbox\nextbox\setbox#1=\nextbox}}

-

-%D \macros

-%D   {investigateskip,

-%D    investigatecount,

-%D    investigatemuskip}

-%D   {}

-%D

-%D Before we meet the visualizing macro's, we first implement

-%D ourselves some handy utility ones. Just for the sake of

-%D efficiency and readability, we introduce some status

-%D variables, that tell us a bit more about the registers we

-%D use:

-%D

-%D \starttypen

-%D \ifflexible

-%D \ifzero

-%D \ifnegative

-%D \ifpositive

-%D \stoptypen

-%D

-%D These status variables are set when we call for one of the

-%D investigation macros, e.g.

-%D

-%D \starttypen

-%D \investigateskip\scratchskip

-%D \stoptypen

-%D

-%D We use some dirty trick to check stretchability of \SKIPS.

-%D Users of these macros are invited to study their exact

-%D behavior first. The positive and negative states both

-%D include zero and are in fact non-negative ($\geq0$) and

-%D non-positive ($\leq0$) .

-

-\newif\ifflexible

-\newif\ifzero

-\newif\ifnegative

-\newif\ifpositive

-

-\def\investigateskip#1%

-  {\relax

-   \scratchdimen=#1\relax

-   \edef\!!stringa{\the\scratchdimen}%

-   \edef\!!stringb{\the#1}%

-   \ifx\!!stringa\!!stringb \flexiblefalse \else \flexibletrue \fi

-   \ifdim#1=\!!zeropoint\relax

-     \zerotrue      \else

-     \zerofalse     \fi

-   \ifdim#1<\!!zeropoint\relax

-     \positivefalse \else

-     \positivetrue  \fi

-   \ifdim#1>\!!zeropoint\relax

-     \negativefalse \else

-     \negativetrue  \fi}

-

-\def\investigatecount#1%

-  {\relax

-   \flexiblefalse

-   \ifnum#1=0

-     \zerotrue      \else

-     \zerofalse     \fi

-   \ifnum#1<0

-     \positivefalse \else

-     \positivetrue  \fi

-   \ifnum#1>0

-     \negativefalse \else

-     \negativetrue  \fi}

-

-\def\investigatemuskip#1%

-  {\relax

-   \edef\!!stringa{\the\scratchmuskip}%

-   \edef\!!stringb{0mu}%

-   \def\!!stringc##1##2\\{##1}%

-   \expandafter\edef\expandafter\!!stringc\expandafter

-     {\expandafter\!!stringc\!!stringa\\}%

-   \edef\!!stringd{-}%

-   \flexiblefalse

-   \ifx\!!stringa\!!stringb

-     \zerotrue

-     \negativefalse

-     \positivefalse

-   \else

-     \zerofalse

-     \ifx\!!stringc\!!stringd

-       \positivefalse

-       \negativetrue

-     \else

-       \positivetrue

-       \negativefalse

-     \fi

-   \fi}

-

-%D Now the neccessary utility macros are defined, we can make a

-%D start with the visualizing ones. The implementation of these

-%D macros is a compromise between readability, efficiency of

-%D coding and processing speed. Sometimes we do in steps what

-%D could have been done in combination, sometimes we use a few

-%D boxes more or less then actually needed, and more than once

-%D one can find the same piece of rule drawing code twice.

-

-%D \macros

-%D   {ifcenteredvcue,normalvcue}

-%D   {}

-%D

-%D Depending on the context, one can force visual vertical cues 

-%D being centered along \type{\hsize} or being put at the 

-%D current position. Although centering often looks better, 

-%D we've chosen the second alternative as default. The main 

-%D reason for doing so is that often when we don't set the 

-%D \type{\hsize} ourselves, \TEX\ takes the value of the 

-%D surrounding box. As a result the visual cues can migrate 

-%D outside the current context. 

-%D 

-%D This behavior is accomplished by a small but effective 

-%D auxiliary macro, which behavior can be influenced by the 

-%D boolean \type{\centeredvcue}. By saying 

-%D

-%D \starttypen 

-%D \centeredvcuetrue

-%D \stoptypen

-%D 

-%D one turns centering on. As said, we turn it off. 

-

-\newif\ifcenteredvcue  \centeredvcuefalse

-

-\def\normalvcue#1%

-  {\normalhbox \ifcenteredvcue to \hsize \fi {\normalhss#1\normalhss}}

-

-%D We could have used the more robust version 

-%D 

-%D \starttypen

-%D \def\normalvcue%

-%D   {\normalhbox \ifcenteredvcue to \hsize \fi

-%D    \bgroup\bgroup\normalhss

-%D    \aftergroup\normalhss\aftergroup\egroup

-%D    \let\next=}

-%D \stoptypen

-%D 

-%D or the probably best one: 

-%D 

-%D \starttypen

-%D \def\normalvcue%

-%D   {\hbox \ifcenteredvcue to \hsize

-%D      \bgroup\bgroup\normalhss

-%D      \aftergroup\normalhss\aftergroup\egroup

-%D    \else

-%D      \bgroup

-%D    \fi

-%D    \let\next=}

-%D \stoptypen

-%D 

-%D Because we don't have to preserve \CATCODES\ and only use 

-%D small arguments, we stick to the first alternative. 

-

-%D \macros

-%D   {testrulewidth}

-%D   {}

-%D

-%D We build our visual cues out of rules. At the cost of a much

-%D bigger \DVI\ file, this is to be prefered over using

-%D characters (1)~because we cannot be sure of their

-%D availability and (2)~because their dimensions are fixed.

-%D

-%D As with ruled boxes, we use a \DIMENSION\ to specify the

-%D width of the ruled elements. This dimension defaults to:

-%D

-%D \starttypen

-%D \testrulewidth=\boxrulewidth

-%D \stoptypen

-%D

-%D Because we prefer whole numbers for specifying the

-%D dimensions, we often use even multiples of

-%D \type{\testrulewidth}.

-

-%D \macros

-%D   {visiblestretch}

-%D   {}

-%D 

-%D A second variable is introduced because of the stretch

-%D components of \SKIPS. At the cost of some accuracy we can

-%D make this stretch visible. 

-%D 

-%D \starttypen

-%D \visiblestretchtrue

-%D \stoptypen

-

-\newdimen\testrulewidth  \testrulewidth=\boxrulewidth

-\newif\ifvisiblestretch  \visiblestretchfalse

-

-%D \macros

-%D   {ruledhss,

-%D    ruledhfil,ruledhfilneg,

-%D    ruledhfill,ruledhfillneg}

-%D   {}

-%D

-%D We start with the easiest part, the fills. The scheme we

-%D follow is {\em visual filling -- going back -- normal

-%D filling}. Visualizing is implemented using \type{\cleaders}.

-%D Because the \BOX\ that follows this command is constructed

-%D only once, the \type{\copy} is not really a prerequisite. We

-%D prefer using a \type{\normalhbox} here instead of a

-%D \type{\hbox}.

-

-\def\setvisiblehfilbox#1\to#2#3#4%

-  {\setbox#1=\normalhbox

-     {\vrule

-        \!!width#2\testrulewidth

-        \!!height#3\testrulewidth

-        \!!depth#4\testrulewidth}%

-   \smashbox#1}

-

-\def\doruledhfiller#1#2#3#4%

-  {#1#2%

-   \bgroup

-     \dontinterfere

-     \dontcomplain

-     \setvisiblehfilbox0\to{4}{#3}{#4}%

-     \setvisiblehfilbox2\to422%

-     \copy0\copy2

-     \bgroup

-       \setvisiblehfilbox0\to422%

-       \cleaders

-         \normalhbox to 12\testrulewidth

-           {\normalhss\copy0\normalhss}%

-         #1%

-     \egroup

-     \setbox0=\normalhbox

-       {\normalhskip-4\testrulewidth\copy0\copy2}%

-     \smashbox0

-     \box0

-   \egroup}

-

-%D The horizontal fillers differ in their boundary

-%D visualization. Watch the small dots. Fillers can be 

-%D combined within reasonable margins.   

-%D

-%D \startregelcorrectie

-%D \baselinerulefalse

-%D \ruledhbox to \hsize

-%D   {\strut\type{\hss}\ruledhss test}

-%D \stopregelcorrectie

-%D

-%D \startregelcorrectie

-%D \baselinerulefalse

-%D \ruledhbox to \hsize

-%D   {\strut\type{\hfil}\ruledhfil test}

-%D \stopregelcorrectie

-%D

-%D \startregelcorrectie

-%D \baselinerulefalse

-%D \ruledhbox to \hsize

-%D   {\strut\type{\hfill}\ruledhfill test}

-%D \stopregelcorrectie

-%D

-%D \startregelcorrectie

-%D \baselinerulefalse

-%D \ruledhbox to \hsize

-%D   {\strut

-%D    \type{\hfil}\type{\hfil}\ruledhfil\ruledhfil 

-%D    test%

-%D    \ruledhfil\type{\hfil}}

-%D \stopregelcorrectie

-%D

-%D The negative counterparts are visualizes, but seldom

-%D become visible, apart from their boundaries.

-%D

-%D \startregelcorrectie

-%D \baselinerulefalse

-%D \ruledhbox to \hsize

-%D   {\strut\type{\hfilneg}\ruledhfilneg test}

-%D \stopregelcorrectie

-%D

-%D \startregelcorrectie

-%D \baselinerulefalse

-%D \ruledhbox to \hsize

-%D   {\strut\type{\hfillneg}\ruledhfillneg test}

-%D \stopregelcorrectie

-%D

-%D Although leaders are used for visualizing, they are

-%D visualized themselves correctly as the next example shows.

-%D

-%D \startregelcorrectie

-%D \baselinerulefalse

-%D \ruledhbox to \hsize

-%D   {\strut\cleaders\normalhbox to 2em{\normalhss$\circ$\normalhss}\ruledhfill}

-%D \stopregelcorrectie

-%D

-%D All five substitutions use the same auxiliary macro. Watch

-%D the positive first -- negative next approach.

-

-\unexpanded\def\ruledhss%

-  {\doruledhfiller\normalhss\normalhfilneg{0}{0}}

-

-\unexpanded\def\ruledhfil%

-  {\doruledhfiller\normalhfil\normalhfilneg{10}{-6}}

-

-\unexpanded\def\ruledhfill%

-  {\doruledhfiller\normalhfill\normalhfillneg{18}{-14}}

-

-\unexpanded\def\ruledhfilneg%

-  {\doruledhfiller\normalhfilneg\normalhfil{-6}{10}}

-

-\unexpanded\def\ruledhfillneg%

-  {\doruledhfiller\normalhfillneg\normalhfill{-14}{18}}

-

-%D \macros

-%D   {ruledvss,

-%D    ruledvfil,ruledvfilneg,

-%D    ruledvfill,ruledvfillneg}

-%D   {}

-%D

-%D The vertical mode commands adopt the same visualization

-%D scheme, but are implemented in a slightly different way.

-

-\def\setvisiblevfilbox#1\to#2#3#4%

-  {\setbox#1=\normalhbox

-     {\vrule

-        \!!width#2\testrulewidth

-        \!!height#3\testrulewidth

-        \!!depth#4\testrulewidth}%

-   \smashbox#1}%

-

-\def\doruledvfiller#1#2#3%

-  {#1#2%

-   \bgroup

-     \dontinterfere

-     \dontcomplain

-     \normaloffinterlineskip

-     \setvisiblevfilbox0\to422%

-     \setbox2=\normalvcue 

-       {\normalhskip -#3\testrulewidth\copy0}%

-     \smashbox2

-     \copy2

-     \bgroup

-       \setbox2=\normalvcue 

-         {\normalhskip -2\testrulewidth\copy0}%

-       \smashbox2

-       \copy2

-       \cleaders

-         \normalvbox to 12\testrulewidth

-           {\normalvss\copy2\normalvss}%

-         #1%

-       \setbox2=\normalvbox

-         {\normalvskip-2\testrulewidth\copy2}%

-       \smashbox2

-       \box2

-     \egroup

-     \box2

-   \egroup}

-

-%D Because they act the same as their horizontal counterparts

-%D we only show a few examples.

-%D

-%D \startregelcorrectie

-%D \hbox to \hsize

-%D   {\dontinterfere

-%D    \baselinerulefalse

-%D    \centeredvcuetrue

-%D    \ruledvbox to 10ex

-%D      {\hsize.18\hsize

-%D       \type{\vss}\ruledvss last line}\normalhss

-%D    \ruledvbox to 10ex

-%D      {\hsize.18\hsize

-%D       \type{\vfil}\ruledvfil last line}\normalhss

-%D    \ruledvbox to 10ex

-%D      {\hsize.18\hsize

-%D       \type{\vfill}\ruledvfill last line}\normalhss

-%D    \ruledvbox to 10ex

-%D      {\hsize.18\hsize

-%D       \type{\vfilneg}\ruledvfilneg last line}\normalhss

-%D    \ruledvbox to 10ex

-%D      {\hsize.18\hsize

-%D       \type{\vfillneg}\ruledvfillneg last line}}

-%D \stopregelcorrectie

-%D 

-%D Keep in mind that \type{\vfillneg} is not part of \PLAIN\

-%D \TEX, but are mimmicked by a macro. 

-

-\unexpanded\def\ruledvss%

-  {\doruledvfiller\normalvss\normalvfilneg{2}}

-

-\unexpanded\def\ruledvfil%

-  {\doruledvfiller\normalvfil\normalvfilneg{-4}}

-

-\unexpanded\def\ruledvfill%

-  {\doruledvfiller\normalvfill\normalvfillneg{-12}}

-

-\unexpanded\def\ruledvfilneg%

-  {\doruledvfiller\normalvfilneg\normalvfil{8}}

-

-\unexpanded\def\ruledvfillneg%

-  {\doruledvfiller\normalvfillneg\normalvfill{16}}

-

-%D \macros

-%D   {ruledhskip}

-%D   {}

-%D

-%D Skips differ from kerns in two important aspects:

-%D

-%D \startopsomming[opelkaar]

-%D \som  line and pagebreaks are allowed at a skip

-%D \som  skips can have a positive and/or negative

-%D       stretchcomponent

-%D \stopopsomming

-%D

-%D Stated a bit different: kerns are fixed skips at which no

-%D line or pagebreak can occur. Because skips have a more open

-%D character, they are visualized in a open way.

-%D

-%D \startbuffer

-%D one

-%D \hskip +30pt plus 5pt

-%D two

-%D \hskip +30pt

-%D \hskip -10pt plus 5pt

-%D three

-%D \hskip   0pt

-%D four

-%D \hskip +30pt

-%D five

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-%D

-%D When skips have a stretch component, this is visualized by

-%D means of a dashed line. Positive skips are on top of the

-%D baseline, negative ones are below it. This way we can show

-%D the combined results. An alternative visualization of

-%D stretch could be drawing the mid line over a length of the

-%D stretch, in positive or negative direction.

-

-\def\doruledhskip%

-  {\relax

-   \dontinterfere

-   \dontcomplain

-   \investigateskip\scratchskip

-   \ifzero

-     \setbox0=\normalhbox

-       {\normalhskip-\testrulewidth

-        \vrule

-          \!!width4\testrulewidth

-          \!!height16\testrulewidth

-          \!!depth16\testrulewidth}%

-   \else

-     \setbox0=\normalhbox to \ifnegative-\fi\scratchskip

-       {\vrule

-          \!!width2\testrulewidth

-          \ifnegative\!!depth\else\!!height\fi16\testrulewidth

-        \cleaders

-          \hrule

-            \ifnegative

-              \!!depth2\testrulewidth

-              \!!height\!!zeropoint

-            \else

-              \!!height2\testrulewidth

-              \!!depth\!!zeropoint

-            \fi

-          \normalhfill

-        \ifflexible

-          \normalhskip\ifnegative\else-\fi\scratchskip 

-          \normalhskip2\testrulewidth

-          \cleaders

-            \normalhbox

-              {\normalhskip 2\testrulewidth

-               \vrule

-                 \!!width2\testrulewidth

-                 \!!height\ifnegative-7\else9\fi\testrulewidth

-                 \!!depth\ifnegative9\else-7\fi\testrulewidth

-               \normalhskip 2\testrulewidth}%

-            \normalhfill

-        \fi

-        \vrule

-          \!!width2\testrulewidth

-          \ifnegative\!!depth\else\!!height\fi16\testrulewidth}%

-     \setbox0=\normalhbox

-       {\ifnegative\else\normalhskip-\scratchskip\fi

-        \box0}%

-   \fi

-   \smashbox0%

-   \ifvisiblestretch \else

-     \flexiblefalse

-   \fi

-   \ifflexible

-     % breaks ok but small displacements can occur

-     \skip2=\scratchskip

-     \advance\skip2 by -1\scratchskip

-     \divide\skip2 by 2

-     \advance\scratchskip by -\skip2

-     \normalhskip\scratchskip

-     \normalpenalty\!!tenthousand

-     \box0

-     \normalhskip\skip2

-   \else

-     \normalhskip\scratchskip

-     \box0

-   \fi

-   \egroup}

-

-\unexpanded\def\ruledhskip%

-  {\bgroup

-   \afterassignment\doruledhskip

-   \scratchskip=}

-

-%D The visual skip is located at a feasible point. Normally

-%D this does not interfere with the normaltypesetting process.

-%D The next examples show (1)~the default behavior, (2)~the

-%D (not entirely correct) distributed stretch and (3)~the way

-%D the text is typeset without cues.

-%D

-%D \startbuffer

-%D \dorecurse

-%D   {15}

-%D   {test\hskip1em plus .5em minus .5em

-%D    test\hskip2em

-%D    test}

-%D \stopbuffer

-%D

-%D \startregelcorrectie

-%D \showmakeup

-%D \haalbuffer

-%D \stopregelcorrectie

-%D

-%D \startregelcorrectie

-%D \showmakeup

-%D \visiblestretchtrue

-%D \haalbuffer

-%D \stopregelcorrectie

-%D

-%D \startregelcorrectie

-%D \haalbuffer

-%D \stopregelcorrectie

-

-%D \macros

-%D   {ruledvskip}

-%D   {}

-%D

-%D We are less fortunate when implementing the vertical skips.

-%D This is a direct result of interference between the boxes that

-%D visualize the skip and skip removal at a pagebreak. Normally

-%D skips disappear at the top of a page, but not of course when

-%D visualized in a \type{\vbox}. A quite perfect simulation

-%D could have been built if we would have had available two

-%D more primitives: \type{\hnop} and \type{\vnop}. These new

-%D primitives could stand for boxes that are visible but are

-%D not taken into account in any way. They are there for us,

-%D but not for \TEX.

-%D

-%D \startbuffer

-%D first line

-%D \vskip +30pt plus 5pt

-%D second line

-%D \vskip +30pt

-%D \vskip -10pt plus 5pt

-%D third line

-%D \par

-%D fourth line

-%D \vskip +30pt

-%D fifth line

-%D \vskip   0pt

-%D sixth line

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-%D

-%D We have to postpone \type{\prevdepth}. Although this 

-%D precaution probably is not completely waterproof, it works 

-%D quite well. 

-

-\def\dodoruledvskip%

-  {\nextdepth=\prevdepth

-   \dontinterfere

-   \dontcomplain

-   \normaloffinterlineskip

-   \investigateskip\scratchskip

-   \ifzero

-     \setbox0=\normalvcue

-       {\vrule

-          \!!width32\testrulewidth

-          \!!height2\testrulewidth

-          \!!depth2\testrulewidth}%

-   \else

-     \setbox0=\normalvbox to \ifnegative-\fi\scratchskip

-       {\hrule

-          \!!width16\testrulewidth

-          \!!height2\testrulewidth

-        \ifflexible

-          \cleaders

-            \normalhbox to 16\testrulewidth

-              {\normalhss

-               \normalvbox

-                 {\normalvskip 2\testrulewidth

-                  \hrule

-                  \!!width2\testrulewidth

-                  \!!height2\testrulewidth

-                  \normalvskip 2\testrulewidth}%

-               \normalhss}%

-            \normalvfill

-        \else

-          \normalvfill

-        \fi

-        \hrule

-          \!!width16\testrulewidth

-          \!!height2\testrulewidth}%

-     \setbox2=\normalvbox to \ht0

-       {\hrule

-          \!!width2\testrulewidth

-          \!!height\ht0}%

-     \ifnegative

-       \ht0=\!!zeropoint

-       \setbox0=\normalhbox

-         {\normalhskip2\testrulewidth % will be improved

-          \normalhskip-\wd0\box0}%

-     \fi

-     \smashbox0%

-     \smashbox2%

-     \setbox0=\normalvcue

-       {\box2\box0}%

-     \setbox0=\normalvbox

-       {\ifnegative\normalvskip\scratchskip\fi\box0}%

-     \smashbox0%

-   \fi

-   \ifvisiblestretch

-     \ifflexible                      

-       \skip2=\scratchskip            

-       \advance\skip2 by -1\scratchskip

-       \divide\skip2 by 2              

-       \advance\scratchskip by -\skip2 

-       \normalvskip\skip2              

-     \fi

-   \fi

-   \normalpenalty\!!tenthousand

-   \box0

-   \prevdepth=\nextdepth % not \dp0=\nextdepth

-   \normalvskip\scratchskip}

-

-%D We try to avoid interfering at the top of a page. Of course

-%D we only do so when we are in the main vertical list.

-

-\def\doruledvskip%

-  {\endgraf % \par

-   \ifdim\pagegoal=\maxdimen

-     \ifinner

-       \dodoruledvskip

-     \fi

-   \else

-     \dodoruledvskip

-   \fi

-   \egroup}

-

-\unexpanded\def\ruledvskip%

-  {\bgroup

-   \afterassignment\doruledvskip

-   \scratchskip=}

-

-%D \macros

-%D   {ruledkern}

-%D   {}

-%D

-%D The macros that implement the kerns are a bit more

-%D complicated than needed, because they also serve the

-%D visualization of glue, our \PLAIN\ defined kerns with

-%D stretch or shrink. We've implemented both horizontal and

-%D vertical kerns as ruled boxes.

-%D

-%D \startbuffer

-%D one

-%D \kern +30pt

-%D two

-%D \kern +30pt

-%D \kern -10pt

-%D three

-%D \kern   0pt

-%D four

-%D \kern +30pt

-%D five

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-%D

-%D Positive and negative kerns are placed on top or below the

-%D baseline, so we are able to track their added result. We

-%D didn't mention spacings of 0~pt yet. Zero values are 

-%D visualized a bit different, because we want to see them 

-%D anyhow.

-

-\def\doruledhkern%

-  {\dontinterfere

-   \dontcomplain

-   \baselinerulefalse

-   \investigateskip\scratchskip

-   \boxrulewidth=2\testrulewidth

-   \ifzero

-     \setbox0=\ruledhbox to 8\testrulewidth

-       {\vrule

-          \!!width\!!zeropoint

-          \!!height16\testrulewidth

-          \!!depth16\testrulewidth}%

-     \setbox0=\normalhbox

-       {\normalhskip-4\testrulewidth\box0}%

-   \else

-     \setbox0=\ruledhbox to \ifnegative-\fi\scratchskip

-       {\vrule

-          \!!width\!!zeropoint

-          \ifnegative\!!depth\else\!!height\fi16\testrulewidth

-        \ifflexible

-          \normalhskip2\testrulewidth

-          \cleaders

-            \normalhbox

-              {\normalhskip 2\testrulewidth

-               \vrule

-                 \!!width2\testrulewidth

-                 \!!height\ifnegative-7\else9\fi\testrulewidth

-                 \!!depth\ifnegative9\else-7\fi\testrulewidth

-               \normalhskip 2\testrulewidth}%

-            \normalhfill

-        \else

-          \normalhfill

-        \fi}%

-     \testrulewidth=2\testrulewidth

-     \setbox0=\ruledhbox{\box0}%  \make...

-   \fi

-   \smashbox0%

-   \normalpenalty\!!tenthousand

-   \normalhbox to \!!zeropoint

-     {\ifnegative\normalhskip1\scratchskip\fi

-      \box0}%

-   \afterwards\scratchskip

-   \egroup}

-

-\unexpanded\def\ruledhkern#1%

-  {\bgroup

-   \let\afterwards=#1\relax

-   \afterassignment\doruledhkern

-   \scratchskip=}

-

-%D After having seen the horizontal ones, the vertical kerns

-%D will not surprise us. In this example we use \type{\par} to

-%D switch to vertical mode.

-%D

-%D \startbuffer

-%D first line

-%D \par \kern +30pt

-%D second line

-%D \par \kern +30pt

-%D \par \kern -10pt

-%D third line

-%D \par

-%D fourth line

-%D \par \kern +30pt

-%D fifth line

-%D \par \kern   0pt

-%D sixth line

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-%D

-%D Like before, we have to postpone \type{\prevdepth}. If we 

-%D leave out this trick, we got ourselves some wrong spacing. 

-

-\def\dodoruledvkern%

-  {\nextdepth=\prevdepth

-   \dontinterfere

-   \dontcomplain

-   \baselinerulefalse

-   \normaloffinterlineskip

-   \investigateskip\scratchskip

-   \boxrulewidth=2\testrulewidth

-   \ifzero

-     \setbox0=\ruledhbox to 32\testrulewidth

-       {\vrule

-          \!!width\!!zeropoint

-          \!!height4\testrulewidth

-          \!!depth4\testrulewidth}%

-   \else

-     \setbox0=\ruledvbox to \ifnegative-\fi\scratchskip

-       {\hsize16\testrulewidth

-        \ifflexible

-          \cleaders

-            \normalhbox to 16\testrulewidth

-              {\normalhss

-               \normalvbox

-                 {\normalvskip 2\testrulewidth

-                  \hrule

-                    \!!width2\testrulewidth

-                    \!!height2\testrulewidth

-                  \normalvskip 2\testrulewidth}%

-               \normalhss}%

-            \normalvfill

-        \else

-          \vrule

-            \!!width\!!zeropoint

-            \!!height\ifnegative-\fi\scratchskip

-          \normalhfill

-        \fi}

-   \fi

-   \testrulewidth=2\testrulewidth

-   \setbox0=\ruledvbox{\box0}%  \make...

-   \smashbox0%

-   \setbox0=\normalvbox

-     {\ifnegative\normalvskip\scratchskip\fi

-      \normalvcue 

-       {\ifnegative\normalhskip-16\testrulewidth\fi\box0}}%

-   \smashbox0%

-   \normalpenalty\!!tenthousand

-   \box0

-   \prevdepth=\nextdepth} % not \dp0=\nextdepth

-

-\def\doruledvkern%

-  {\ifdim\pagegoal=\maxdimen

-     \ifinner

-       \dodoruledvkern

-     \fi

-   \else

-     \dodoruledvkern

-   \fi

-   \afterwards\scratchskip

-   \egroup}

-

-\unexpanded\def\ruledvkern#1%

-  {\bgroup

-   \let\afterwards=#1\relax

-   \afterassignment\doruledvkern

-   \scratchskip=}

-

-\unexpanded\def\ruledkern%

-  {\ifvmode

-     \expandafter\ruledvkern

-   \else

-     \expandafter\ruledhkern

-   \fi

-   \normalkern}

-

-%D A a bit more \TEX nice solution is:

-%D 

-%D \starttypen

-%D \unexpanded\def\ruledkern%

-%D   {\csname ruled\ifvmode v\else h\fi kern\endcsname\normalkern}

-%D \stoptypen

-

-%D \macros

-%D   {ruledhglue,ruledvglue}

-%D   {}

-%D

-%D The non-primitive glue commands are treated as kerns with

-%D stretch. This stretch is presented as a dashed line. I

-%D have to admit that until now, I've never used these glue

-%D commands.

-%D

-%D \startbuffer

-%D one

-%D \hglue +30pt plus 5pt

-%D two

-%D \hglue +30pt

-%D \hglue -10pt plus 5pt

-%D three

-%D \hglue   0pt

-%D four

-%D \hglue +30pt

-%D five

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-

-\def\doruledhglue%

-  {\leavevmode

-   \scratchcounter=\spacefactor

-   \vrule\!!width\!!zeropoint

-   \normalpenalty\!!tenthousand

-   \ruledhkern\normalhskip\scratchskip

-   \spacefactor=\scratchcounter

-   \egroup}

-

-\unexpanded\def\ruledhglue%

-  {\bgroup

-   \afterassignment\doruledhglue\scratchskip=}

-

-%D \startbuffer

-%D first line

-%D \vglue +30pt plus 5pt

-%D second line

-%D \vglue +30pt

-%D \vglue -10pt plus 5pt

-%D third line

-%D \par

-%D fourth line

-%D \vglue +30pt

-%D fifth line

-%D \vglue   0pt

-%D sixth line

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-

-\def\doruledvglue%

-  {\endgraf % \par

-   \nextdepth=\prevdepth 

-   \hrule\!!height\!!zeropoint

-   \normalpenalty\!!tenthousand

-   \ruledvkern\normalvskip\scratchskip

-   \prevdepth=\nextdepth

-   \egroup}

-

-\unexpanded\def\ruledvglue%

-  {\bgroup

-   \afterassignment\doruledvglue\scratchskip=}

-

-%D \macros

-%D   {ruledmkern,ruledmskip}

-%D   {}

-%D

-%D Mathematical kerns and skips are specified in mu. This

-%D font related unit is incompatible with those of \DIMENSIONS\

-%D and \SKIPS. Because in math mode spacing is often a very

-%D subtle matter, we've used a very simple, not overloaded way

-%D to show them.

-

-\def\dodoruledmkern#1%

-  {\dontinterfere

-   \dontcomplain

-   \setbox0=\normalhbox

-     {$\normalmkern\ifnegative-\fi\scratchmuskip$}%

-   \setbox0=\normalhbox to \wd0

-     {\vrule

-        \!!height16\testrulewidth

-        \!!depth16\testrulewidth

-        \!!width\testrulewidth

-      \leaders

-        \hrule

-          \!!height\ifpositive16\else-14\fi\testrulewidth

-          \!!depth\ifpositive-14\else16\fi\testrulewidth

-        \normalhfill

-      \ifflexible

-        \normalhskip-\wd0

-        \leaders

-          \hrule

-            \!!height\testrulewidth

-            \!!depth\testrulewidth

-          \normalhfill

-      \fi

-      \vrule

-        \!!height16\testrulewidth

-        \!!depth16\testrulewidth

-        \!!width\testrulewidth}%

-   \smashbox0%

-   \ifnegative

-      #1\scratchmuskip

-     \box0

-   \else

-     \box0

-      #1\scratchmuskip

-   \fi

-   \egroup}

-

-%D \startbuffer

-%D $a \mkern3mu = \mkern3mu

-%D  b \quad

-%D  \mkern-2mu + \mkern-2mu

-%D  \quad c$

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-

-\def\doruledmkern%

-  {\investigatemuskip\scratchmuskip

-   \flexiblefalse

-   \dodoruledmkern\normalmkern}

-

-\unexpanded\def\ruledmkern%

-  {\bgroup

-   \afterassignment\doruledmkern\scratchmuskip=}

-

-%D \startbuffer

-%D $a \mskip3mu = \mskip3mu

-%D  b \quad

-%D  \mskip-2mu + \mskip-2mu

-%D  \quad c$

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-

-\def\doruledmskip%

-  {\investigatemuskip\scratchmuskip

-   \flexibletrue

-   \dodoruledmkern\normalmskip}

-

-\unexpanded\def\ruledmskip%

-  {\bgroup

-   \afterassignment\doruledmskip\scratchmuskip=}

-

-%D \macros

-%D   {penalty}

-%D   {}

-%D

-%D After presenting fills, skip, kerns and glue we've come to

-%D see penalties. In the first implementation --- most of the

-%D time needed to develop this set of macros went into testing

-%D different types of visualization --- penalties were mere

-%D small blocks with one black half, depending on the sign.

-%D This most recent version also gives an indication of the

-%D amount of penalty. Penalties can go from less than $-10000$

-%D to over $+10000$, and their behavior is somewhat

-%D non-lineair, with some values having special meanings. We

-%D therefore decided not to use its value for a lineair

-%D indicator.

-%D

-%D \startbuffer

-%D one

-%D \penalty +100

-%D two

-%D \penalty +100

-%D \penalty -100

-%D three

-%D \penalty    0

-%D four

-%D \penalty +100

-%D five

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-%D

-%D The small sticks at the side of the penalty indicate it

-%D size. The next example shows the positive and negative

-%D penalties of 0, 1, 10, 100, 1000 and 10000.

-%D

-%D \startregelcorrectie

-%D \hbox

-%D   {test \ruledhpenalty0

-%D    test \ruledhpenalty1

-%D    test \ruledhpenalty10

-%D    test \ruledhpenalty100

-%D    test \ruledhpenalty1000

-%D    test \ruledhpenalty10000

-%D    test}

-%D \stopregelcorrectie

-%D

-%D \blanko

-%D

-%D \startregelcorrectie

-%D \hbox

-%D   {test \ruledhpenalty0

-%D    test \ruledhpenalty-1

-%D    test \ruledhpenalty-10

-%D    test \ruledhpenalty-100

-%D    test \ruledhpenalty-1000

-%D    test \ruledhpenalty-10000

-%D    test}

-%D \stopregelcorrectie

-%D

-%D \blanko

-%D

-%D This way stacked penalties of different severance can be

-%D shown in combination.

-%D

-%D test \ruledhpenalty10 \ruledhpenalty100

-%D test

-%D test \ruledhpenalty1000 \ruledhpenalty-1000

-%D test

-

-\def\setruledpenaltybox#1#2#3#4#5#6%

-  {\setbox#1=\normalhbox

-     {\ifnum#2=0 \else

-        \ifnum#2>0

-          \def\sign{+}%

-        \else

-          \def\sign{-}%

-        \fi

-        \dimen0=\ifnum\sign#2>9999

-                  28\else

-                \ifnum\sign#2>999

-                  22\else

-                \ifnum\sign#2>99

-                  16\else

-                \ifnum\sign#2>9

-                  10\else

-                  4

-                \fi\fi\fi\fi \testrulewidth

-        \ifnum#2<0

-          \normalhskip-\dimen0

-          \normalhskip-2\testrulewidth

-          \vrule

-            \!!width2\testrulewidth

-            \!!height#3\testrulewidth

-            \!!depth#4\testrulewidth

-        \fi

-        \vrule

-          \!!width\dimen0

-          \!!height#5\testrulewidth

-          \!!depth#6\testrulewidth

-        \ifnum#2>0

-          \vrule

-            \!!width2\testrulewidth

-            \!!height#3\testrulewidth

-            \!!depth#4\testrulewidth

-         \fi

-      \fi}%

-   \smashbox#1}

-

-\def\doruledhpenalty%

-  {\dontinterfere

-   \dontcomplain

-   \investigatecount\scratchcounter

-   \testrulewidth=2\testrulewidth

-   \boxrulewidth=\testrulewidth

-   \setbox0=\ruledhbox to 8\testrulewidth

-     {\ifnegative\else\normalhss\fi

-      \vrule

-        \!!depth8\testrulewidth

-        \!!width\ifzero0\else4\fi\testrulewidth

-      \ifpositive\else\normalhss\fi}%

-   \setruledpenaltybox{2}{\scratchcounter}{0}{8}{-3.5}{4.5}%

-   \normalpenalty\!!tenthousand

-   \setbox0=\normalhbox

-     {\normalhskip-4\testrulewidth

-      \ifnegative

-        \box2\box0

-      \else

-        \box0\box2

-      \fi}%

-   \smashbox0%

-   \box0

-   \normalpenalty\scratchcounter

-   \egroup}

-

-\unexpanded\def\ruledhpenalty%

-  {\bgroup

-   \afterassignment\doruledhpenalty

-   \scratchcounter=}

-

-%D The size of a vertical penalty is also shown on the

-%D horizontal axis. This way there is less interference with

-%D the often preceding or following skips and kerns.

-%D

-%D \startbuffer

-%D first line

-%D \par \penalty +100

-%D second line

-%D \par \penalty +100

-%D \par \penalty -100

-%D third line

-%D \par \penalty    0

-%D fourth line

-%D \par \penalty +100

-%D fifth line

-%D \stopbuffer

-%D

-%D \ShowBufferedExample

-

-\def\doruledvpenalty%

-  {\ifdim\pagegoal=\maxdimen

-   \else

-     \nextdepth=\prevdepth  

-     \dontinterfere

-     \dontcomplain

-     \investigatecount\scratchcounter

-     \testrulewidth=2\testrulewidth

-     \boxrulewidth=\testrulewidth

-     \setbox0=\ruledhbox

-       {\vrule

-          \!!height4\testrulewidth

-          \!!depth4\testrulewidth

-          \!!width\!!zeropoint

-        \vrule

-          \!!height\ifnegative.5\else4\fi\testrulewidth

-          \!!depth\ifpositive.5\else4\fi\testrulewidth

-          \!!width8\testrulewidth}%

-     \setruledpenaltybox{2}{\scratchcounter}{4}{4}{.5}{.5}%

-     \setbox0=\normalhbox

-       {\normalhskip-4\testrulewidth

-        \ifnegative

-          \box2\box0

-        \else

-          \box0\box2

-        \fi

-        \normalhss}%

-     \smashbox0%

-     \normalpenalty\!!tenthousand

-     \nointerlineskip

-     \dp0=\nextdepth  % not \prevdepth=\nextdepth 

-     \normalvbox

-       {\normalvcue{\box0}}%

-   \fi

-   \normalpenalty\scratchcounter

-   \egroup}

-

-\unexpanded\def\ruledvpenalty%

-  {\bgroup

-   \afterassignment\doruledvpenalty

-   \scratchcounter=}

-

-\unexpanded\def\ruledpenalty%

-  {\ifvmode

-     \expandafter\ruledvpenalty

-   \else

-     \expandafter\ruledhpenalty

-   \fi}

-

-%D At the cost of some more tokens, a bit more clever 

-%D implementation would be:

-%D

-%D \starttypen

-%D \unexpanded\def\ruledpenalty%

-%D   {\csname ruled\ifvmode v\else h\fi penalty\endcsname}

-%D \stoptypen

-

-%D \macros

-%D   {showfils,dontshowfils,

-%D    showboxes,dontshowboxes,

-%D    showskips,dontshowskips,

-%D    showpenalties,dontshowpenalties}

-%D   {}

-%D

-%D For those who want to manipulate the visual cues in detail,

-%D we have grouped them.

-

-\def\showfils%

-  {\let\hss      = \ruledhss

-   \let\hfil     = \ruledhfil

-   \let\hfill    = \ruledhfill

-   \let\hfilneg  = \ruledhfilneg

-   \let\hfillneg = \ruledhfillneg

-   \let\vss      = \ruledvss

-   \let\vfil     = \ruledvfil

-   \let\vfill    = \ruledvfill

-   \let\vfilneg  = \ruledvfilneg

-   \let\vfillneg = \ruledvfillneg}

-

-\def\dontshowfils%

-  {\let\hss      = \normalhss

-   \let\hfil     = \normalhfil

-   \let\hfill    = \normalhfill

-   \let\hfilneg  = \normalhfilneg

-   \let\hfillneg = \normalhfillneg

-   \let\vss      = \normalvss

-   \let\vfil     = \normalvfil

-   \let\vfill    = \normalvfill

-   \let\vfilneg  = \normalvfilneg

-   \let\vfillneg = \normalvfillneg}

-

-\def\showboxes%

-  {\baselineruletrue

-   \let\hbox     = \ruledhbox

-   \let\vbox     = \ruledvbox

-   \let\vtop     = \ruledvtop

-   \let\vcenter  = \ruledvcenter}

-

-\def\dontshowboxes%

-  {\let\hbox     = \normalhbox

-   \let\vbox     = \normalvbox

-   \let\vtop     = \normalvtop

-   \let\vcenter  = \normalvcenter}

-

-\def\showskips%

-  {\let\hskip    = \ruledhskip

-   \let\vskip    = \ruledvskip

-   \let\kern     = \ruledkern

-   \let\mskip    = \ruledmskip

-   \let\mkern    = \ruledmkern

-   \let\hglue    = \ruledhglue

-   \let\vglue    = \ruledvglue}

-

-\def\dontshowskips%

-  {\let\hskip    = \normalhskip

-   \let\vskip    = \normalvskip

-   \let\kern     = \normalkern

-   \let\mskip    = \normalmskip

-   \let\mkern    = \normalmkern

-   \let\hglue    = \normalhglue

-   \let\vglue    = \normalvglue}

-

-\def\showpenalties%

-  {\let\penalty  = \ruledpenalty}

-

-\def\dontshowpenalties%

-  {\let\penalty  = \normalpenalty}

-

-%D \macros

-%D   {showingcomposition,

-%D    showcomposition,dontshowcomposition,}

-%D   {}

-%D

-%D All these nice options come together in two macros. The

-%D first one turns the options on, the second turnes them off.

-%D Both macros only do their job when we are actually showing

-%D the composition.

-%D

-%D \starttypen

-%D \showingcompositiontrue

-%D \showcomposition

-%D \stoptypen

-%D 

-%D Because the output routine can do tricky things, like

-%D multiple column typesetting and manipulation of the

-%D pagebody, shifting things around and so on, the macro

-%D \type{\dontshowcomposition} best can be called when we enter

-%D this routine. Too much visual cues just don't make sense. In

-%D \CONTEXT\ this has been taken care of. 

-

-\newif\ifshowingcomposition

-

-\def\showcomposition%

-  {\ifshowingcomposition

-     \showfils

-     \showboxes

-     \showskips

-     \showpenalties

-   \fi}

-

-\def\dontshowcomposition%

-  {\ifshowingcomposition

-     \dontshowfils

-     \dontshowboxes

-     \dontshowskips

-     \dontshowpenalties

-   \fi}

-

-%D \macros

-%D   {showmakeup,

-%D    defaulttestrulewidth}

-%D   {}

-%D

-%D Just to make things even more easy, we have defined:

-%D

-%D \starttypen

-%D \showmakeup

-%D \stoptypen

-%D

-%D For the sake of those who don't (yet) use \CONTEXT\ we 

-%D preset \type{\defaulttestrulewidth} to the already set 

-%D value. Otherwise we default to a bodyfontsize related value.

-%D

-%D \starttypen

-%D \def\defaulttestrulewidth{.2pt}

-%D \stoptypen

-%D

-%D Beware, it's a macro not a \DIMENSION.

-

-\ifx\korpsgrootte\undefined

-  \edef\defaulttestrulewidth{\the\testrulewidth}

-\else

-  \def\defaulttestrulewidth{.02\korpsgrootte}  % still dutch

-\fi

-

-\def\showmakeup%

-  {\testrulewidth=\defaulttestrulewidth

-   \showingcompositiontrue

-   \showcomposition}

-

-\protect

-

-%D \ifCONTEXT \let\next=\relax \else \let\next=\endinput 

-%D The documented source you have been reading was processed

-%D using some surrogate makeup. When this file is processed

-%D in \CONTEXT, a few more examples show up here, like a local

-%D table of contents and a local register. 

-%D \fi \next

-

-% %D Lets end with some more advanced examples. When visualized,

-% %D the table of contents of the outer level is typeset as:

-% %D

-% %D {\showmakeup\plaatsinhoud[criterium=vorige]}

-% %D

-%D Lets end with some more advanced examples. 

-%D Definitions and enumerations come in many flavors. The 

-%D next one for instance is defined as: 

-%D

-%D \starttypen

-%D \definedescription[test][place=left,hang=3,width=6em]

-%D \stoptypen

-%D

-%D When applied to some text, this would look like: 

-%D

-%D \bgroup

-%D \showmakeup

-%D \doordefinieren[test][plaats=links,hang=3,breedte=6em]

-%D

-%D \test{visual\\debugger} I would be very pleased if \TEX\

-%D had two more primitives: \type{\vnop} and \type{\hnop}. Both

-%D should act and show up as normal boxes, but stay invisible

-%D for \TEX\ when it's doing calculations. The \type{\vnop} 

-%D for instance should not interact with the internal mechanism 

-%D responsible for the disappearing skips, kerns and penalties

-%D at a pagebreak. As long as we don't have these two boxtypes, 

-%D visual debugging will never be perfect. 

-%D

-%D \egroup

-%D

-%D The index to this section looks like:

-%D

-%D {\stelrefererenin[prefix=dummy]\showmakeup\plaatsindex[criterium=lokaal]}

-%D

-%D Although not impressive examples or typesetting, both

-%D show us how and where things happen. When somehow the last

-%D lines in this two column index don't allign, then this is

-%D due to some still unknown interference.

-

-\endinput

+%D \module
+%D   [       file=supp-vis,
+%D        version=1996.10.21,
+%D          title=\CONTEXT\ Support Macros,
+%D       subtitle=Visualization,
+%D         author=Hans Hagen,
+%D           date=\currentdate,
+%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]
+%C
+%C This module is part of the \CONTEXT\ macro||package and is
+%C therefore copyrighted by \PRAGMA. Non||commercial use is 
+%C granted. 
+
+%D \gdef\ShowBufferedExample% private typeseting macro
+%D   {\startregelcorrectie
+%D    \bgroup
+%D    \steltypenin[marge=0pt,optie=kleur]
+%D    \showmakeup
+%D    \centeredvcuetrue
+%D    \dontinterfere
+%D    \baselinerulefalse
+%D    \normalvbox
+%D      {\normalhbox to \hsize
+%D         {$\hsize=.5\hsize
+%D          \advance\hsize by -.5em
+%D          \normalvcenter{\vbox{\haalbuffer}}\normalhss
+%D          \normalvcenter{\vbox{\dontshowcomposition\typebuffer}}$}}
+%D    \egroup
+%D    \stopregelcorrectie}
+%D
+%D \gdef\ShowBufferedExampleBox% private typeseting macro
+%D   {\startregelcorrectie
+%D    \bgroup
+%D    \steltypenin[marge=0pt,optie=kleur]
+%D    \showmakeup
+%D    \centeredvcuetrue
+%D    \dontinterfere
+%D    \baselinerulefalse
+%D    \normalvbox
+%D      {\normalhbox to \hsize
+%D         {$\hsize=.5\hsize
+%D          \advance\hsize by -.5em
+%D          \normalvcenter{\baselineruletrue\vbox{\haalbuffer}}\normalhss
+%D          \normalvcenter{\vbox{\dontshowcomposition\typebuffer}}$}}
+%D    \egroup
+%D    \stopregelcorrectie}
+
+%D Although an integral part of \CONTEXT, this module is one
+%D of the support modules. Its stand alone character permits
+%D use in \PLAIN\ \TEX\ or \TEX\ based macropackages.
+%D \ifCONTEXT \else If in some examples the verbatim listings
+%D don't show up nice, this is due to processing by a system
+%D that does not support buffering. In \CONTEXT\ we show the
+%D commands in the margin, use bit more advanced way of
+%D numbering, and typeset the source in \TEX nicolored
+%D verbatim. Sorry for this inconvenience.\fi 
+%D 
+%D Depending on my personal needs and those of whoever uses it,
+%D the macros will be improved in terms of visualization,
+%D efficiency and compatibility. These rather low level
+%D visualization macros are supplemented by ones that can
+%D visualize baselines, the page layout and whatever deserves
+%D attention. Most of those macros can be found in \type
+%D {core-vis} and other core modules. Their integration in
+%D \CONTEXT\ prohibits generic applications. 
+
+\ifx \undefined \writestatus \input supp-mis.tex \fi
+
+%D One of the strong points of \TEX\ is abstraction of textual
+%D input. When macros are defined well and do what we
+%D want them to do, we will seldom need the tools present in
+%D What You See Is What You Get systems. For instance, when
+%D entering text we don't need rulers, because no manual
+%D shifting and/or alignment of text is needed. On the other
+%D hand, when we are designing macros or specifying layout
+%D elements, some insight in \TEX's advanced spacing, kerning,
+%D filling, boxing and punishment abilities will be handy.
+%D That's why we've implemented a mechanism that shows some of
+%D the inner secrets of \TEX.
+
+\writestatus{loading}{Context Support Macros / Visualization}
+
+%D In this module we are going to redefine some \TEX\
+%D primitives and \PLAIN\ macro's. Their original meaning is
+%D saved in macros with corresponding names, preceded by
+%D \type{normal}. These original macros are (1)~used to
+%D temporary restore the old values when needed and
+%D (2)~used to prevent recursive calls in the macros that
+%D replace them.
+
+\unprotect
+
+\let\visualvrule\vrule
+\let\visualhrule\hrule
+
+%D \macros
+%D   {dontinterfere}
+%D
+%D Indentation, left and/or right skips, redefinition of
+%D \type{\par} and assignments to \type{\everypar} can lead to
+%D  unwanted results. We can therefore turn all those things
+%D off with \type{\dontinterfere}.
+
+\def\dontinterfere%
+  {\everypar  = {}%
+   \let\par   = \endgraf
+   \parindent = \!!zeropoint
+   \parskip   = \!!zeropoint
+   \leftskip  = \!!zeropoint
+   \rightskip = \!!zeropoint
+   \relax}
+
+%D \macros
+%D   {dontcomplain}
+%D
+%D In this module we do a lot of box manipulations. Because we
+%D don't want to be confronted with to many over- and underfull
+%D messages we introduce \type{\dontcomplain}.
+
+\def\dontcomplain%
+  {\hbadness  = \!!tenthousand
+   \hfuzz     = \maxdimen
+   \vbadness  = \!!tenthousand
+   \vfuzz     = \maxdimen}
+
+%D \macros
+%D   {normaloffinterlineskip}
+%D
+%D The next hack is needed because in \CONTEXT\ we redefine 
+%D \type{\offinterlineskip}.  
+
+\ifx\undefined\normaloffinterlineskip 
+  \let\normaloffinterlineskip=\offinterlineskip
+\fi
+
+%D \macros
+%D   {normalhbox,
+%D    normalvbox,normalvtop}
+%D
+%D There are three types of boxes, one horizontal and two
+%D vertical in nature. As we will see later on, all three types
+%D are to be handled according to their orientation and
+%D baseline behavior. Especially \type{\vtop}'s need our
+%D special attention.
+
+\let\normalhbox     = \hbox
+\let\normalvbox     = \vbox
+\let\normalvtop     = \vtop
+\let\normalvcenter  = \vcenter
+
+%D \macros
+%D   {normalhskip,
+%D    normalvskip}
+%D
+%D Next come the flexible skips, which come in two flavors
+%D too. Like boxes these are handled with \TEX\ primitives.
+
+\let\normalhskip    = \hskip
+\let\normalvskip    = \vskip
+
+%D \macros
+%D   {normalpenalty,
+%D    normalkern}
+%D
+%D Both penalties and kerns are taken care of by mode sensitive
+%D primitives. This means that when making them visible, we
+%D have to take the current mode into account.
+
+\let\normalpenalty  = \penalty
+\let\normalkern     = \kern
+
+%D \macros
+%D   {normalhglue,
+%D    normalvglue}
+%D
+%D Glues on the other hand are macro's defined in \PLAIN\ \TEX.
+%D As we will see, their definitions make the implementation of
+%D their visible counterparts a bit more \TeX{}nical.
+
+\let\normalhglue    = \hglue
+\let\normalvglue    = \vglue
+
+%D \macros
+%D   {normalmkern,
+%D    normalmskip}
+%D
+%D Math mode has its own spacing primitives, preceded by
+%D \type{m}. Due to the relation with the current font and the
+%D way math is typeset, their unit \type{mu} is not compatible
+%D with other dimensions. As a result, the visual appearance
+%D of these primitives is kept primitive too.
+
+\let\normalmkern = \mkern
+\let\normalmskip = \mskip
+
+%D \macros
+%D   {hfilneg,
+%D    vfilneg}
+%D
+%D Fills can be made visible quite easy. We only need some
+%D additional negation macros. Because \PLAIN\ \TEX\ only
+%D offers \type{\hfilneg} and \type{\vfilneg}, we define our
+%D own alternative double \type{ll}'ed ones.
+
+\def\hfillneg%
+  {\normalhskip\!!zeropoint \!!plus-1fill\relax}
+
+\def\vfillneg%
+  {\normalvskip\!!zeropoint \!!plus-1fill\relax}
+
+%D \macros
+%D   {normalhss,normalhfil,normalhfill,
+%D    normalvss,normalvfil,normalvfill}
+%D
+%D The positive stretch primitives are used independant and in
+%D combination with \type{\leaders}.
+
+\let\normalhss   = \hss
+\let\normalhfil  = \hfil
+\let\normalhfill = \hfill
+\let\normalvss   = \vss
+\let\normalvfil  = \vfil
+\let\normalvfill = \vfill
+
+%D \macros
+%D   {normalhfilneg,normalhfillneg,
+%D    normalvfilneg,normalvfillneg}
+%D
+%D Keep in mind that both \type{\hfillneg} and \type{\vfillneg}
+%D are not part of \PLAIN\ \TEX\ and therefore not documented
+%D in standard \TEX\ documentation. They can nevertheless be
+%D used at will.
+
+\let\normalhfilneg  = \hfilneg
+\let\normalhfillneg = \hfillneg
+\let\normalvfilneg  = \vfilneg
+\let\normalvfillneg = \vfillneg
+
+%D Visualization is not always wanted. Instead of turning this
+%D option off in those (unpredictable) situations, we just
+%D redefine a few \PLAIN\ macros.
+
+\def\rlap#1{\normalhbox to \!!zeropoint{#1\normalhss}}
+\def\llap#1{\normalhbox to \!!zeropoint{\normalhss#1}}
+
+\def~{\normalpenalty\!!tenthousand\ }
+
+%D \macros
+%D   {makeruledbox}
+%D
+%D Ruled boxes can be typeset is many ways. Here we present
+%D just one alternative. This implementation may be a little 
+%D complicated, but it supports all three kind of boxes. The 
+%D next command expects a \BOX\ specification, like: 
+%D
+%D \starttypen
+%D \makeruledbox0
+%D \stoptypen
+
+%D \macros
+%D   {baselinerule,baselinefill}
+%D  
+%D We can make the baseline of a box visible, both dashed and
+%D as a rule. The line is drawn on top of the baseline. All 
+%D we have to say is:
+%D
+%D \starttypen
+%D \baselineruletrue
+%D \baselinefilltrue
+%D \stoptypen
+%D
+%D At the cost of some overhead these alternatives are
+%D implemented using \type{\if}'s:
+
+\newif\ifbaselinerule  \baselineruletrue
+\newif\ifbaselinefill  \baselinefillfalse
+
+%D \macros
+%D   {iftoprule,ifbottomrule,ifleftrule,ifrightrule}
+%D  
+%D Rules can be turned on and off, but by default we have:
+%D
+%D \starttypen
+%D \topruletrue
+%D \bottomruletrue
+%D \leftruletrue
+%D \rightruletrue
+%D \stoptypen
+%D
+%D As we see below:
+
+\newif\iftoprule     \topruletrue
+\newif\ifbottomrule  \bottomruletrue
+\newif\ifleftrule    \leftruletrue
+\newif\ifrightrule   \rightruletrue
+
+%D \macros
+%D   {boxrulewidth}
+%D  
+%D The width in the surrounding rules can be specified by
+%D assigning an apropriate value to the dimension used. This
+%D module defaults the width to:
+%D
+%D \starttypen
+%D \boxrulewidth=.2pt
+%D \stoptypen
+%D
+%D Although we are already low on \DIMENSIONS\ it's best to
+%D spend one here, mainly because it enables easy manipulation,
+%D like multiplication by a given factor.
+
+\newdimen\boxrulewidth \boxrulewidth=.2pt
+
+%D The core macro \type{\makeruledbox} looks a bit hefty. The
+%D manipulation at the end is needed because we want to
+%D preserve both the mode and the baseline. This means that
+%D \type{\vtop}'s and \type{\vbox}'es behave the way we expect
+%D them to do.
+%D
+%D \startregelcorrectie
+%D \hbox
+%D   {\ruledhbox to 5em{\strut test\normalhss}\hskip1em
+%D    \ruledvbox{\hsize 5em\strut test \par test\strut}\hskip1em
+%D    \ruledvtop{\hsize 5em\strut test \par test\strut}}
+%D \stopregelcorrectie
+%D
+%D The \type{\cleaders} part of the macro is responsible for
+%D the visual baseline. The \type{\normalhfill} belongs to this
+%D primitive too. By storing and restoring the height and depth
+%D of box \type{#1}, we preserve the mode.
+
+\def\makeruledbox#1%
+  {\edef\ruledheight{\the\ht#1}%
+   \edef\ruleddepth {\the\dp#1}%
+   \edef\ruledwidth {\the\wd#1}%
+   \setbox\scratchbox=\normalvbox
+     {\dontcomplain
+      \normaloffinterlineskip
+      \visualhrule
+        \!!height\boxrulewidth
+        \iftoprule\else\!!width\!!zeropoint\fi
+      \normalvskip-\boxrulewidth
+      \normalhbox to \ruledwidth
+        {\visualvrule
+           \!!height\ruledheight
+           \!!depth\ruleddepth
+           \!!width\ifleftrule\else0\fi\boxrulewidth
+         \ifdim\ruledheight>\!!zeropoint \else \baselinerulefalse \fi
+         \ifdim\ruleddepth>\!!zeropoint \else \baselinerulefalse \fi
+         \ifbaselinerule
+           \ifdim\ruledwidth<20\boxrulewidth
+             \baselinefilltrue
+           \fi
+           \cleaders
+             \ifbaselinefill
+               \visualhrule
+                 \!!height\boxrulewidth
+             \else
+               \normalhbox
+                 {\normalhskip2.5\boxrulewidth
+                  \visualvrule
+                    \!!height\boxrulewidth
+                    \!!width5\boxrulewidth
+                  \normalhskip2.5\boxrulewidth}%
+             \fi
+         \fi
+         \normalhfill
+         \visualvrule
+           \!!width\ifrightrule\else0\fi\boxrulewidth}%
+       \normalvskip-\boxrulewidth
+       \visualhrule
+         \!!height\boxrulewidth
+         \ifbottomrule\else\!!width\!!zeropoint\fi}%
+   \wd#1=\!!zeropoint
+   \setbox#1=\ifhbox#1\normalhbox\else\normalvbox\fi
+     {\normalhbox{\box#1\lower\ruleddepth\box\scratchbox}}%
+   \ht#1=\ruledheight
+   \wd#1=\ruledwidth
+   \dp#1=\ruleddepth}
+
+%D Just in case one didn't notice: the rules are in fact layed
+%D over the box. This way the contents of a box cannot
+%D visually interfere with the rules around (upon) it. A more
+%D advanced version of ruled boxes can be found in one of the 
+%D core modules of \CONTEXT. There we take offsets, color, 
+%D rounded corners, backgrounds and alignment into account too.
+
+%D \macros
+%D   {ruledhbox,
+%D    ruledvbox,ruledvtop,
+%D    ruledvcenter}
+%D 
+%D These macro's can be used instead of \type{\hbox},
+%D \type{\vbox}, \type{\vtop} and, when in math mode,
+%D \type{\vcenter}. They just do what their names state. Using
+%D an auxiliary macro would save us a few words of memory, but
+%D it would make their appearance even more obscure. 
+%D 
+%D \startbuffer
+%D \hbox
+%D   {\strut
+%D    one
+%D    two
+%D    \hbox{three}
+%D    four
+%D    five}
+%D \stopbuffer
+%D
+%D \ShowBufferedExampleBox
+
+\unexpanded\def\ruledhbox%
+  {\normalhbox\bgroup
+   \dowithnextbox{\makeruledbox\nextbox\box\nextbox\egroup}%
+   \normalhbox}
+
+%D \startbuffer
+%D \vbox
+%D   {\strut
+%D    first line  \par
+%D    second line \par
+%D    third line  \par
+%D    fourth line \par
+%D    fifth line
+%D    \strut }
+%D \stopbuffer
+%D
+%D \ShowBufferedExampleBox
+
+\unexpanded\def\ruledvbox%
+  {\normalvbox\bgroup
+   \dowithnextbox{\makeruledbox\nextbox\box\nextbox\egroup}%
+   \normalvbox}
+
+%D \startbuffer
+%D \vtop
+%D   {\strut
+%D    first line  \par
+%D    second line \par
+%D    third line  \par
+%D    fourth line \par
+%D    fifth line
+%D    \strut }
+%D \stopbuffer
+%D
+%D \ShowBufferedExampleBox
+
+\unexpanded\def\ruledvtop%
+  {\normalvtop\bgroup
+   \dowithnextbox{\makeruledbox\nextbox\box\nextbox\egroup}%
+   \normalvtop}
+
+%D \startbuffer
+%D \hbox
+%D   {$\vcenter{\hsize.2\hsize 
+%D       alfa \par beta}$
+%D    $\vcenter to 3cm{\hsize.2\hsize 
+%D       alfa \par beta \par gamma}$
+%D    $\vcenter{\hsize.2\hsize 
+%D       alfa \par beta}$}
+%D \stopbuffer
+%D
+%D \ShowBufferedExampleBox
+
+\unexpanded\def\ruledvcenter%
+  {\normalvbox\bgroup
+   \dontinterfere
+   \dowithnextbox
+     {\scratchdimen=.5\ht\nextbox
+      \advance\scratchdimen by .5\dp\nextbox
+      \ht\nextbox=\scratchdimen
+      \dp\nextbox=\scratchdimen
+      \ruledhbox{\box\nextbox}%
+      \egroup}%
+   \normalvbox}
+
+%D \macros
+%D   {ruledbox,
+%D    setruledbox}
+%D
+%D Of the next two macros the first can be used to precede a
+%D box of ones own choice. One can for instance prefix boxes
+%D with \type{\ruledbox} and afterwards --- when the macro
+%D satisfy the needs --- let it to \type{\relax}.
+%D
+%D \starttypen
+%D \ruledbox\hbox{What rules do you mean?}
+%D \stoptypen
+%D
+%D The macro \type{\setruledbox} can be used to directly
+%D rule a box.
+%D
+%D \starttypen
+%D \setruledbox12=\hbox{Who's talking about rules here?}
+%D \stoptypen
+%D
+%D At the cost of some extra macros we can implement a
+%D variant that does not need the~\type{=}, but we stick to:
+
+\unexpanded\def\ruledbox%
+  {\dowithnextbox{\makeruledbox\nextbox\box\nextbox}}
+
+\def\setruledbox#1=%
+  {\dowithnextbox{\makeruledbox\nextbox\setbox#1=\nextbox}}
+
+%D \macros
+%D   {investigateskip,
+%D    investigatecount,
+%D    investigatemuskip}
+%D
+%D Before we meet the visualizing macro's, we first implement
+%D ourselves some handy utility ones. Just for the sake of
+%D efficiency and readability, we introduce some status
+%D variables, that tell us a bit more about the registers we
+%D use:
+%D
+%D \starttypen
+%D \ifflexible
+%D \ifzero
+%D \ifnegative
+%D \ifpositive
+%D \stoptypen
+%D
+%D These status variables are set when we call for one of the
+%D investigation macros, e.g.
+%D
+%D \starttypen
+%D \investigateskip\scratchskip
+%D \stoptypen
+%D
+%D We use some dirty trick to check stretchability of \SKIPS.
+%D Users of these macros are invited to study their exact
+%D behavior first. The positive and negative states both
+%D include zero and are in fact non-negative ($\geq0$) and
+%D non-positive ($\leq0$) .
+
+\newif\ifflexible
+\newif\ifzero
+\newif\ifnegative
+\newif\ifpositive
+
+\def\investigateskip#1%
+  {\relax
+   \scratchdimen=#1\relax
+   \edef\!!stringa{\the\scratchdimen}%
+   \edef\!!stringb{\the#1}%
+   \ifx\!!stringa\!!stringb \flexiblefalse \else \flexibletrue \fi
+   \ifdim#1=\!!zeropoint\relax
+     \zerotrue      \else
+     \zerofalse     \fi
+   \ifdim#1<\!!zeropoint\relax
+     \positivefalse \else
+     \positivetrue  \fi
+   \ifdim#1>\!!zeropoint\relax
+     \negativefalse \else
+     \negativetrue  \fi}
+
+\def\investigatecount#1%
+  {\relax
+   \flexiblefalse
+   \ifnum#1=0
+     \zerotrue      \else
+     \zerofalse     \fi
+   \ifnum#1<0
+     \positivefalse \else
+     \positivetrue  \fi
+   \ifnum#1>0
+     \negativefalse \else
+     \negativetrue  \fi}
+
+\def\investigatemuskip#1%
+  {\relax
+   \edef\!!stringa{\the\scratchmuskip}%
+   \edef\!!stringb{0mu}%
+   \def\!!stringc##1##2\\{##1}%
+   \expandafter\edef\expandafter\!!stringc\expandafter
+     {\expandafter\!!stringc\!!stringa\\}%
+   \edef\!!stringd{-}%
+   \flexiblefalse
+   \ifx\!!stringa\!!stringb
+     \zerotrue
+     \negativefalse
+     \positivefalse
+   \else
+     \zerofalse
+     \ifx\!!stringc\!!stringd
+       \positivefalse
+       \negativetrue
+     \else
+       \positivetrue
+       \negativefalse
+     \fi
+   \fi}
+
+%D Now the neccessary utility macros are defined, we can make a
+%D start with the visualizing ones. The implementation of these
+%D macros is a compromise between readability, efficiency of
+%D coding and processing speed. Sometimes we do in steps what
+%D could have been done in combination, sometimes we use a few
+%D boxes more or less then actually needed, and more than once
+%D one can find the same piece of rule drawing code twice.
+
+%D \macros
+%D   {ifcenteredvcue,normalvcue}
+%D
+%D Depending on the context, one can force visual vertical cues 
+%D being centered along \type{\hsize} or being put at the 
+%D current position. Although centering often looks better, 
+%D we've chosen the second alternative as default. The main 
+%D reason for doing so is that often when we don't set the 
+%D \type{\hsize} ourselves, \TEX\ takes the value of the 
+%D surrounding box. As a result the visual cues can migrate 
+%D outside the current context. 
+%D 
+%D This behavior is accomplished by a small but effective 
+%D auxiliary macro, which behavior can be influenced by the 
+%D boolean \type{\centeredvcue}. By saying 
+%D
+%D \starttypen 
+%D \centeredvcuetrue
+%D \stoptypen
+%D 
+%D one turns centering on. As said, we turn it off. 
+
+\newif\ifcenteredvcue  \centeredvcuefalse
+
+\def\normalvcue#1%
+  {\normalhbox \ifcenteredvcue to \hsize \fi {\normalhss#1\normalhss}}
+
+%D We could have used the more robust version 
+%D 
+%D \starttypen
+%D \def\normalvcue%
+%D   {\normalhbox \ifcenteredvcue to \hsize \fi
+%D    \bgroup\bgroup\normalhss
+%D    \aftergroup\normalhss\aftergroup\egroup
+%D    \let\next=}
+%D \stoptypen
+%D 
+%D or the probably best one: 
+%D 
+%D \starttypen
+%D \def\normalvcue%
+%D   {\hbox \ifcenteredvcue to \hsize
+%D      \bgroup\bgroup\normalhss
+%D      \aftergroup\normalhss\aftergroup\egroup
+%D    \else
+%D      \bgroup
+%D    \fi
+%D    \let\next=}
+%D \stoptypen
+%D 
+%D Because we don't have to preserve \CATCODES\ and only use 
+%D small arguments, we stick to the first alternative. 
+
+%D \macros
+%D   {testrulewidth}
+%D
+%D We build our visual cues out of rules. At the cost of a much
+%D bigger \DVI\ file, this is to be prefered over using
+%D characters (1)~because we cannot be sure of their
+%D availability and (2)~because their dimensions are fixed.
+%D
+%D As with ruled boxes, we use a \DIMENSION\ to specify the
+%D width of the ruled elements. This dimension defaults to:
+%D
+%D \starttypen
+%D \testrulewidth=\boxrulewidth
+%D \stoptypen
+%D
+%D Because we prefer whole numbers for specifying the
+%D dimensions, we often use even multiples of
+%D \type{\testrulewidth}.
+
+%D \macros
+%D   {visiblestretch}
+%D 
+%D A second variable is introduced because of the stretch
+%D components of \SKIPS. At the cost of some accuracy we can
+%D make this stretch visible. 
+%D 
+%D \starttypen
+%D \visiblestretchtrue
+%D \stoptypen
+
+\newdimen\testrulewidth  \testrulewidth=\boxrulewidth
+\newif\ifvisiblestretch  \visiblestretchfalse
+
+%D \macros
+%D   {ruledhss,
+%D    ruledhfil,ruledhfilneg,
+%D    ruledhfill,ruledhfillneg}
+%D
+%D We start with the easiest part, the fills. The scheme we
+%D follow is {\em visual filling -- going back -- normal
+%D filling}. Visualizing is implemented using \type{\cleaders}.
+%D Because the \BOX\ that follows this command is constructed
+%D only once, the \type{\copy} is not really a prerequisite. We
+%D prefer using a \type{\normalhbox} here instead of a
+%D \type{\hbox}.
+
+\def\setvisiblehfilbox#1\to#2#3#4%
+  {\setbox#1=\normalhbox
+     {\visualvrule
+        \!!width#2\testrulewidth
+        \!!height#3\testrulewidth
+        \!!depth#4\testrulewidth}%
+   \smashbox#1}
+
+\def\doruledhfiller#1#2#3#4%
+  {#1#2%
+   \bgroup
+     \dontinterfere
+     \dontcomplain
+     \setvisiblehfilbox0\to{4}{#3}{#4}%
+     \setvisiblehfilbox2\to422%
+     \copy0\copy2
+     \bgroup
+       \setvisiblehfilbox0\to422%
+       \cleaders
+         \normalhbox to 12\testrulewidth
+           {\normalhss\copy0\normalhss}%
+         #1%
+     \egroup
+     \setbox0=\normalhbox
+       {\normalhskip-4\testrulewidth\copy0\copy2}%
+     \smashbox0
+     \box0
+   \egroup}
+
+%D The horizontal fillers differ in their boundary
+%D visualization. Watch the small dots. Fillers can be 
+%D combined within reasonable margins.   
+%D
+%D \startregelcorrectie
+%D \baselinerulefalse
+%D \ruledhbox to \hsize
+%D   {\strut\type{\hss}\ruledhss test}
+%D \stopregelcorrectie
+%D
+%D \startregelcorrectie
+%D \baselinerulefalse
+%D \ruledhbox to \hsize
+%D   {\strut\type{\hfil}\ruledhfil test}
+%D \stopregelcorrectie
+%D
+%D \startregelcorrectie
+%D \baselinerulefalse
+%D \ruledhbox to \hsize
+%D   {\strut\type{\hfill}\ruledhfill test}
+%D \stopregelcorrectie
+%D
+%D \startregelcorrectie
+%D \baselinerulefalse
+%D \ruledhbox to \hsize
+%D   {\strut
+%D    \type{\hfil}\type{\hfil}\ruledhfil\ruledhfil 
+%D    test%
+%D    \ruledhfil\type{\hfil}}
+%D \stopregelcorrectie
+%D
+%D The negative counterparts are visualizes, but seldom
+%D become visible, apart from their boundaries.
+%D
+%D \startregelcorrectie
+%D \baselinerulefalse
+%D \ruledhbox to \hsize
+%D   {\strut\type{\hfilneg}\ruledhfilneg test}
+%D \stopregelcorrectie
+%D
+%D \startregelcorrectie
+%D \baselinerulefalse
+%D \ruledhbox to \hsize
+%D   {\strut\type{\hfillneg}\ruledhfillneg test}
+%D \stopregelcorrectie
+%D
+%D Although leaders are used for visualizing, they are
+%D visualized themselves correctly as the next example shows.
+%D
+%D \startregelcorrectie
+%D \baselinerulefalse
+%D \ruledhbox to \hsize
+%D   {\strut\cleaders\normalhbox to 2em{\normalhss$\circ$\normalhss}\ruledhfill}
+%D \stopregelcorrectie
+%D
+%D All five substitutions use the same auxiliary macro. Watch
+%D the positive first -- negative next approach.
+
+\unexpanded\def\ruledhss%
+  {\doruledhfiller\normalhss\normalhfilneg{0}{0}}
+
+\unexpanded\def\ruledhfil%
+  {\doruledhfiller\normalhfil\normalhfilneg{10}{-6}}
+
+\unexpanded\def\ruledhfill%
+  {\doruledhfiller\normalhfill\normalhfillneg{18}{-14}}
+
+\unexpanded\def\ruledhfilneg%
+  {\doruledhfiller\normalhfilneg\normalhfil{-6}{10}}
+
+\unexpanded\def\ruledhfillneg%
+  {\doruledhfiller\normalhfillneg\normalhfill{-14}{18}}
+
+%D \macros
+%D   {ruledvss,
+%D    ruledvfil,ruledvfilneg,
+%D    ruledvfill,ruledvfillneg}
+%D
+%D The vertical mode commands adopt the same visualization
+%D scheme, but are implemented in a slightly different way.
+
+\def\setvisiblevfilbox#1\to#2#3#4%
+  {\setbox#1=\normalhbox
+     {\visualvrule
+        \!!width#2\testrulewidth
+        \!!height#3\testrulewidth
+        \!!depth#4\testrulewidth}%
+   \smashbox#1}%
+
+\def\doruledvfiller#1#2#3%
+  {#1#2%
+   \bgroup
+     \dontinterfere
+     \dontcomplain
+     \normaloffinterlineskip
+     \setvisiblevfilbox0\to422%
+     \setbox2=\normalvcue 
+       {\normalhskip -#3\testrulewidth\copy0}%
+     \smashbox2
+     \copy2
+     \bgroup
+       \setbox2=\normalvcue 
+         {\normalhskip -2\testrulewidth\copy0}%
+       \smashbox2
+       \copy2
+       \cleaders
+         \normalvbox to 12\testrulewidth
+           {\normalvss\copy2\normalvss}%
+         #1%
+       \setbox2=\normalvbox
+         {\normalvskip-2\testrulewidth\copy2}%
+       \smashbox2
+       \box2
+     \egroup
+     \box2
+   \egroup}
+
+%D Because they act the same as their horizontal counterparts
+%D we only show a few examples.
+%D
+%D \startregelcorrectie
+%D \hbox to \hsize
+%D   {\dontinterfere
+%D    \baselinerulefalse
+%D    \centeredvcuetrue
+%D    \ruledvbox to 10ex
+%D      {\hsize.18\hsize
+%D       \type{\vss}\ruledvss last line}\normalhss
+%D    \ruledvbox to 10ex
+%D      {\hsize.18\hsize
+%D       \type{\vfil}\ruledvfil last line}\normalhss
+%D    \ruledvbox to 10ex
+%D      {\hsize.18\hsize
+%D       \type{\vfill}\ruledvfill last line}\normalhss
+%D    \ruledvbox to 10ex
+%D      {\hsize.18\hsize
+%D       \type{\vfilneg}\ruledvfilneg last line}\normalhss
+%D    \ruledvbox to 10ex
+%D      {\hsize.18\hsize
+%D       \type{\vfillneg}\ruledvfillneg last line}}
+%D \stopregelcorrectie
+%D 
+%D Keep in mind that \type{\vfillneg} is not part of \PLAIN\
+%D \TEX, but are mimmicked by a macro. 
+
+\unexpanded\def\ruledvss%
+  {\doruledvfiller\normalvss\normalvfilneg{2}}
+
+\unexpanded\def\ruledvfil%
+  {\doruledvfiller\normalvfil\normalvfilneg{-4}}
+
+\unexpanded\def\ruledvfill%
+  {\doruledvfiller\normalvfill\normalvfillneg{-12}}
+
+\unexpanded\def\ruledvfilneg%
+  {\doruledvfiller\normalvfilneg\normalvfil{8}}
+
+\unexpanded\def\ruledvfillneg%
+  {\doruledvfiller\normalvfillneg\normalvfill{16}}
+
+%D \macros
+%D   {ruledhskip}
+%D
+%D Skips differ from kerns in two important aspects:
+%D
+%D \startopsomming[opelkaar]
+%D \som  line and pagebreaks are allowed at a skip
+%D \som  skips can have a positive and/or negative
+%D       stretchcomponent
+%D \stopopsomming
+%D
+%D Stated a bit different: kerns are fixed skips at which no
+%D line or pagebreak can occur. Because skips have a more open
+%D character, they are visualized in a open way.
+%D
+%D \startbuffer
+%D one
+%D \hskip +30pt plus 5pt
+%D two
+%D \hskip +30pt
+%D \hskip -10pt plus 5pt
+%D three
+%D \hskip   0pt
+%D four
+%D \hskip +30pt
+%D five
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+%D
+%D When skips have a stretch component, this is visualized by
+%D means of a dashed line. Positive skips are on top of the
+%D baseline, negative ones are below it. This way we can show
+%D the combined results. An alternative visualization of
+%D stretch could be drawing the mid line over a length of the
+%D stretch, in positive or negative direction.
+
+\def\doruledhskip%
+  {\relax
+   \dontinterfere
+   \dontcomplain
+   \investigateskip\scratchskip
+   \ifzero
+     \setbox0=\normalhbox
+       {\normalhskip-\testrulewidth
+        \visualvrule
+          \!!width4\testrulewidth
+          \!!height16\testrulewidth
+          \!!depth16\testrulewidth}%
+   \else
+     \setbox0=\normalhbox to \ifnegative-\fi\scratchskip
+       {\visualvrule
+          \!!width2\testrulewidth
+          \ifnegative\!!depth\else\!!height\fi16\testrulewidth
+        \cleaders
+          \visualhrule
+            \ifnegative
+              \!!depth2\testrulewidth
+              \!!height\!!zeropoint
+            \else
+              \!!height2\testrulewidth
+              \!!depth\!!zeropoint
+            \fi
+          \normalhfill
+        \ifflexible
+          \normalhskip\ifnegative\else-\fi\scratchskip 
+          \normalhskip2\testrulewidth
+          \cleaders
+            \normalhbox
+              {\normalhskip 2\testrulewidth
+               \visualvrule
+                 \!!width2\testrulewidth
+                 \!!height\ifnegative-7\else9\fi\testrulewidth
+                 \!!depth\ifnegative9\else-7\fi\testrulewidth
+               \normalhskip 2\testrulewidth}%
+            \normalhfill
+        \fi
+        \visualvrule
+          \!!width2\testrulewidth
+          \ifnegative\!!depth\else\!!height\fi16\testrulewidth}%
+     \setbox0=\normalhbox
+       {\ifnegative\else\normalhskip-\scratchskip\fi
+        \box0}%
+   \fi
+   \smashbox0%
+   \ifvisiblestretch \else
+     \flexiblefalse
+   \fi
+   \ifflexible
+     % breaks ok but small displacements can occur
+     \skip2=\scratchskip
+     \advance\skip2 by -1\scratchskip
+     \divide\skip2 by 2
+     \advance\scratchskip by -\skip2
+     \normalhskip\scratchskip
+     \normalpenalty\!!tenthousand
+     \box0
+     \normalhskip\skip2
+   \else
+     \normalhskip\scratchskip
+     \box0
+   \fi
+   \egroup}
+
+\unexpanded\def\ruledhskip%
+  {\bgroup
+   \afterassignment\doruledhskip
+   \scratchskip=}
+
+%D The visual skip is located at a feasible point. Normally
+%D this does not interfere with the normaltypesetting process.
+%D The next examples show (1)~the default behavior, (2)~the
+%D (not entirely correct) distributed stretch and (3)~the way
+%D the text is typeset without cues.
+%D
+%D \startbuffer
+%D \dorecurse
+%D   {15}
+%D   {test\hskip1em plus .5em minus .5em
+%D    test\hskip2em
+%D    test}
+%D \stopbuffer
+%D
+%D \startregelcorrectie
+%D \showmakeup
+%D \haalbuffer
+%D \stopregelcorrectie
+%D
+%D \startregelcorrectie
+%D \showmakeup
+%D \visiblestretchtrue
+%D \haalbuffer
+%D \stopregelcorrectie
+%D
+%D \startregelcorrectie
+%D \haalbuffer
+%D \stopregelcorrectie
+
+%D \macros
+%D   {ruledvskip}
+%D
+%D We are less fortunate when implementing the vertical skips.
+%D This is a direct result of interference between the boxes that
+%D visualize the skip and skip removal at a pagebreak. Normally
+%D skips disappear at the top of a page, but not of course when
+%D visualized in a \type{\vbox}. A quite perfect simulation
+%D could have been built if we would have had available two
+%D more primitives: \type{\hnop} and \type{\vnop}. These new
+%D primitives could stand for boxes that are visible but are
+%D not taken into account in any way. They are there for us,
+%D but not for \TEX.
+%D
+%D \startbuffer
+%D first line
+%D \vskip +30pt plus 5pt
+%D second line
+%D \vskip +30pt
+%D \vskip -10pt plus 5pt
+%D third line
+%D \par
+%D fourth line
+%D \vskip +30pt
+%D fifth line
+%D \vskip   0pt
+%D sixth line
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+%D
+%D We have to postpone \type{\prevdepth}. Although this 
+%D precaution probably is not completely waterproof, it works 
+%D quite well. 
+
+\def\dodoruledvskip%
+  {\nextdepth=\prevdepth
+   \dontinterfere
+   \dontcomplain
+   \normaloffinterlineskip
+   \investigateskip\scratchskip
+   \ifzero
+     \setbox0=\normalvcue
+       {\visualvrule
+          \!!width32\testrulewidth
+          \!!height2\testrulewidth
+          \!!depth2\testrulewidth}%
+   \else
+     \setbox0=\normalvbox to \ifnegative-\fi\scratchskip
+       {\visualhrule
+          \!!width16\testrulewidth
+          \!!height2\testrulewidth
+        \ifflexible
+          \cleaders
+            \normalhbox to 16\testrulewidth
+              {\normalhss
+               \normalvbox
+                 {\normalvskip 2\testrulewidth
+                  \visualhrule
+                  \!!width2\testrulewidth
+                  \!!height2\testrulewidth
+                  \normalvskip 2\testrulewidth}%
+               \normalhss}%
+            \normalvfill
+        \else
+          \normalvfill
+        \fi
+        \visualhrule
+          \!!width16\testrulewidth
+          \!!height2\testrulewidth}%
+     \setbox2=\normalvbox to \ht0
+       {\visualhrule
+          \!!width2\testrulewidth
+          \!!height\ht0}%
+     \ifnegative
+       \ht0=\!!zeropoint
+       \setbox0=\normalhbox
+         {\normalhskip2\testrulewidth % will be improved
+          \normalhskip-\wd0\box0}%
+     \fi
+     \smashbox0%
+     \smashbox2%
+     \setbox0=\normalvcue
+       {\box2\box0}%
+     \setbox0=\normalvbox
+       {\ifnegative\normalvskip\scratchskip\fi\box0}%
+     \smashbox0%
+   \fi
+   \ifvisiblestretch
+     \ifflexible                      
+       \skip2=\scratchskip            
+       \advance\skip2 by -1\scratchskip
+       \divide\skip2 by 2              
+       \advance\scratchskip by -\skip2 
+       \normalvskip\skip2              
+     \fi
+   \fi
+   \normalpenalty\!!tenthousand
+   \box0
+   \prevdepth=\nextdepth % not \dp0=\nextdepth
+   \normalvskip\scratchskip}
+
+%D We try to avoid interfering at the top of a page. Of course
+%D we only do so when we are in the main vertical list.
+
+\def\doruledvskip%
+  {\endgraf % \par
+   \ifdim\pagegoal=\maxdimen
+     \ifinner
+       \dodoruledvskip
+     \fi
+   \else
+     \dodoruledvskip
+   \fi
+   \egroup}
+
+\unexpanded\def\ruledvskip%
+  {\bgroup
+   \afterassignment\doruledvskip
+   \scratchskip=}
+
+%D \macros
+%D   {ruledkern}
+%D
+%D The macros that implement the kerns are a bit more
+%D complicated than needed, because they also serve the
+%D visualization of glue, our \PLAIN\ defined kerns with
+%D stretch or shrink. We've implemented both horizontal and
+%D vertical kerns as ruled boxes.
+%D
+%D \startbuffer
+%D one
+%D \kern +30pt
+%D two
+%D \kern +30pt
+%D \kern -10pt
+%D three
+%D \kern   0pt
+%D four
+%D \kern +30pt
+%D five
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+%D
+%D Positive and negative kerns are placed on top or below the
+%D baseline, so we are able to track their added result. We
+%D didn't mention spacings of 0~pt yet. Zero values are 
+%D visualized a bit different, because we want to see them 
+%D anyhow.
+
+\def\doruledhkern%
+  {\dontinterfere
+   \dontcomplain
+   \baselinerulefalse
+   \investigateskip\scratchskip
+   \boxrulewidth=2\testrulewidth
+   \ifzero
+     \setbox0=\ruledhbox to 8\testrulewidth
+       {\visualvrule
+          \!!width\!!zeropoint
+          \!!height16\testrulewidth
+          \!!depth16\testrulewidth}%
+     \setbox0=\normalhbox
+       {\normalhskip-4\testrulewidth\box0}%
+   \else
+     \setbox0=\ruledhbox to \ifnegative-\fi\scratchskip
+       {\visualvrule
+          \!!width\!!zeropoint
+          \ifnegative\!!depth\else\!!height\fi16\testrulewidth
+        \ifflexible
+          \normalhskip2\testrulewidth
+          \cleaders
+            \normalhbox
+              {\normalhskip 2\testrulewidth
+               \visualvrule
+                 \!!width2\testrulewidth
+                 \!!height\ifnegative-7\else9\fi\testrulewidth
+                 \!!depth\ifnegative9\else-7\fi\testrulewidth
+               \normalhskip 2\testrulewidth}%
+            \normalhfill
+        \else
+          \normalhfill
+        \fi}%
+     \testrulewidth=2\testrulewidth
+     \setbox0=\ruledhbox{\box0}%  \make...
+   \fi
+   \smashbox0%
+   \normalpenalty\!!tenthousand
+   \normalhbox to \!!zeropoint
+     {\ifnegative\normalhskip1\scratchskip\fi
+      \box0}%
+   \afterwards\scratchskip
+   \egroup}
+
+\unexpanded\def\ruledhkern#1%
+  {\bgroup
+   \let\afterwards=#1\relax
+   \afterassignment\doruledhkern
+   \scratchskip=}
+
+%D After having seen the horizontal ones, the vertical kerns
+%D will not surprise us. In this example we use \type{\par} to
+%D switch to vertical mode.
+%D
+%D \startbuffer
+%D first line
+%D \par \kern +30pt
+%D second line
+%D \par \kern +30pt
+%D \par \kern -10pt
+%D third line
+%D \par
+%D fourth line
+%D \par \kern +30pt
+%D fifth line
+%D \par \kern   0pt
+%D sixth line
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+%D
+%D Like before, we have to postpone \type{\prevdepth}. If we 
+%D leave out this trick, we got ourselves some wrong spacing. 
+
+\def\dodoruledvkern%
+  {\nextdepth=\prevdepth
+   \dontinterfere
+   \dontcomplain
+   \baselinerulefalse
+   \normaloffinterlineskip
+   \investigateskip\scratchskip
+   \boxrulewidth=2\testrulewidth
+   \ifzero
+     \setbox0=\ruledhbox to 32\testrulewidth
+       {\visualvrule
+          \!!width\!!zeropoint
+          \!!height4\testrulewidth
+          \!!depth4\testrulewidth}%
+   \else
+     \setbox0=\ruledvbox to \ifnegative-\fi\scratchskip
+       {\hsize16\testrulewidth
+        \ifflexible
+          \cleaders
+            \normalhbox to 16\testrulewidth
+              {\normalhss
+               \normalvbox
+                 {\normalvskip 2\testrulewidth
+                  \visualhrule
+                    \!!width2\testrulewidth
+                    \!!height2\testrulewidth
+                  \normalvskip 2\testrulewidth}%
+               \normalhss}%
+            \normalvfill
+        \else
+          \visualvrule
+            \!!width\!!zeropoint
+            \!!height\ifnegative-\fi\scratchskip
+          \normalhfill
+        \fi}
+   \fi
+   \testrulewidth=2\testrulewidth
+   \setbox0=\ruledvbox{\box0}%  \make...
+   \smashbox0%
+   \setbox0=\normalvbox
+     {\ifnegative\normalvskip\scratchskip\fi
+      \normalvcue 
+       {\ifnegative\normalhskip-16\testrulewidth\fi\box0}}%
+   \smashbox0%
+   \normalpenalty\!!tenthousand
+   \box0
+   \prevdepth=\nextdepth} % not \dp0=\nextdepth
+
+\def\doruledvkern%
+  {\ifdim\pagegoal=\maxdimen
+     \ifinner
+       \dodoruledvkern
+     \fi
+   \else
+     \dodoruledvkern
+   \fi
+   \afterwards\scratchskip
+   \egroup}
+
+\unexpanded\def\ruledvkern#1%
+  {\bgroup
+   \let\afterwards=#1\relax
+   \afterassignment\doruledvkern
+   \scratchskip=}
+
+\unexpanded\def\ruledkern%
+  {\ifvmode
+     \expandafter\ruledvkern
+   \else
+     \expandafter\ruledhkern
+   \fi
+   \normalkern}
+
+%D A a bit more \TEX nice solution is:
+%D 
+%D \starttypen
+%D \unexpanded\def\ruledkern%
+%D   {\csname ruled\ifvmode v\else h\fi kern\endcsname\normalkern}
+%D \stoptypen
+
+%D \macros
+%D   {ruledhglue,ruledvglue}
+%D
+%D The non-primitive glue commands are treated as kerns with
+%D stretch. This stretch is presented as a dashed line. I
+%D have to admit that until now, I've never used these glue
+%D commands.
+%D
+%D \startbuffer
+%D one
+%D \hglue +30pt plus 5pt
+%D two
+%D \hglue +30pt
+%D \hglue -10pt plus 5pt
+%D three
+%D \hglue   0pt
+%D four
+%D \hglue +30pt
+%D five
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+
+\def\doruledhglue%
+  {\leavevmode
+   \scratchcounter=\spacefactor
+   \visualvrule\!!width\!!zeropoint
+   \normalpenalty\!!tenthousand
+   \ruledhkern\normalhskip\scratchskip
+   \spacefactor=\scratchcounter
+   \egroup}
+
+\unexpanded\def\ruledhglue%
+  {\bgroup
+   \afterassignment\doruledhglue\scratchskip=}
+
+%D \startbuffer
+%D first line
+%D \vglue +30pt plus 5pt
+%D second line
+%D \vglue +30pt
+%D \vglue -10pt plus 5pt
+%D third line
+%D \par
+%D fourth line
+%D \vglue +30pt
+%D fifth line
+%D \vglue   0pt
+%D sixth line
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+
+\def\doruledvglue%
+  {\endgraf % \par
+   \nextdepth=\prevdepth 
+   \visualhrule\!!height\!!zeropoint
+   \normalpenalty\!!tenthousand
+   \ruledvkern\normalvskip\scratchskip
+   \prevdepth=\nextdepth
+   \egroup}
+
+\unexpanded\def\ruledvglue%
+  {\bgroup
+   \afterassignment\doruledvglue\scratchskip=}
+
+%D \macros
+%D   {ruledmkern,ruledmskip}
+%D
+%D Mathematical kerns and skips are specified in mu. This
+%D font related unit is incompatible with those of \DIMENSIONS\
+%D and \SKIPS. Because in math mode spacing is often a very
+%D subtle matter, we've used a very simple, not overloaded way
+%D to show them.
+
+\def\dodoruledmkern#1%
+  {\dontinterfere
+   \dontcomplain
+   \setbox0=\normalhbox
+     {$\normalmkern\ifnegative-\fi\scratchmuskip$}%
+   \setbox0=\normalhbox to \wd0
+     {\visualvrule
+        \!!height16\testrulewidth
+        \!!depth16\testrulewidth
+        \!!width\testrulewidth
+      \leaders
+        \visualhrule
+          \!!height\ifpositive16\else-14\fi\testrulewidth
+          \!!depth\ifpositive-14\else16\fi\testrulewidth
+        \normalhfill
+      \ifflexible
+        \normalhskip-\wd0
+        \leaders
+          \visualhrule
+            \!!height\testrulewidth
+            \!!depth\testrulewidth
+          \normalhfill
+      \fi
+      \visualvrule
+        \!!height16\testrulewidth
+        \!!depth16\testrulewidth
+        \!!width\testrulewidth}%
+   \smashbox0%
+   \ifnegative
+      #1\scratchmuskip
+     \box0
+   \else
+     \box0
+      #1\scratchmuskip
+   \fi
+   \egroup}
+
+%D \startbuffer
+%D $a \mkern3mu = \mkern3mu
+%D  b \quad
+%D  \mkern-2mu + \mkern-2mu
+%D  \quad c$
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+
+\def\doruledmkern%
+  {\investigatemuskip\scratchmuskip
+   \flexiblefalse
+   \dodoruledmkern\normalmkern}
+
+\unexpanded\def\ruledmkern%
+  {\bgroup
+   \afterassignment\doruledmkern\scratchmuskip=}
+
+%D \startbuffer
+%D $a \mskip3mu = \mskip3mu
+%D  b \quad
+%D  \mskip-2mu + \mskip-2mu
+%D  \quad c$
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+
+\def\doruledmskip%
+  {\investigatemuskip\scratchmuskip
+   \flexibletrue
+   \dodoruledmkern\normalmskip}
+
+\unexpanded\def\ruledmskip%
+  {\bgroup
+   \afterassignment\doruledmskip\scratchmuskip=}
+
+%D \macros
+%D   {penalty}
+%D
+%D After presenting fills, skip, kerns and glue we've come to
+%D see penalties. In the first implementation --- most of the
+%D time needed to develop this set of macros went into testing
+%D different types of visualization --- penalties were mere
+%D small blocks with one black half, depending on the sign.
+%D This most recent version also gives an indication of the
+%D amount of penalty. Penalties can go from less than $-10000$
+%D to over $+10000$, and their behavior is somewhat
+%D non-lineair, with some values having special meanings. We
+%D therefore decided not to use its value for a lineair
+%D indicator.
+%D
+%D \startbuffer
+%D one
+%D \penalty +100
+%D two
+%D \penalty +100
+%D \penalty -100
+%D three
+%D \penalty    0
+%D four
+%D \penalty +100
+%D five
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+%D
+%D The small sticks at the side of the penalty indicate it
+%D size. The next example shows the positive and negative
+%D penalties of 0, 1, 10, 100, 1000 and 10000.
+%D
+%D \startregelcorrectie
+%D \hbox
+%D   {test \ruledhpenalty0
+%D    test \ruledhpenalty1
+%D    test \ruledhpenalty10
+%D    test \ruledhpenalty100
+%D    test \ruledhpenalty1000
+%D    test \ruledhpenalty10000
+%D    test}
+%D \stopregelcorrectie
+%D
+%D \blanko
+%D
+%D \startregelcorrectie
+%D \hbox
+%D   {test \ruledhpenalty0
+%D    test \ruledhpenalty-1
+%D    test \ruledhpenalty-10
+%D    test \ruledhpenalty-100
+%D    test \ruledhpenalty-1000
+%D    test \ruledhpenalty-10000
+%D    test}
+%D \stopregelcorrectie
+%D
+%D \blanko
+%D
+%D This way stacked penalties of different severance can be
+%D shown in combination.
+%D
+%D test \ruledhpenalty10 \ruledhpenalty100
+%D test
+%D test \ruledhpenalty1000 \ruledhpenalty-1000
+%D test
+
+\def\setruledpenaltybox#1#2#3#4#5#6%
+  {\setbox#1=\normalhbox
+     {\ifnum#2=0 \else
+        \ifnum#2>0
+          \def\sign{+}%
+        \else
+          \def\sign{-}%
+        \fi
+        \dimen0=\ifnum\sign#2>9999
+                  28\else
+                \ifnum\sign#2>999
+                  22\else
+                \ifnum\sign#2>99
+                  16\else
+                \ifnum\sign#2>9
+                  10\else
+                  4
+                \fi\fi\fi\fi \testrulewidth
+        \ifnum#2<0
+          \normalhskip-\dimen0
+          \normalhskip-2\testrulewidth
+          \visualvrule
+            \!!width2\testrulewidth
+            \!!height#3\testrulewidth
+            \!!depth#4\testrulewidth
+        \fi
+        \visualvrule
+          \!!width\dimen0
+          \!!height#5\testrulewidth
+          \!!depth#6\testrulewidth
+        \ifnum#2>0
+          \visualvrule
+            \!!width2\testrulewidth
+            \!!height#3\testrulewidth
+            \!!depth#4\testrulewidth
+         \fi
+      \fi}%
+   \smashbox#1}
+
+\def\doruledhpenalty%
+  {\dontinterfere
+   \dontcomplain
+   \investigatecount\scratchcounter
+   \testrulewidth=2\testrulewidth
+   \boxrulewidth=\testrulewidth
+   \setbox0=\ruledhbox to 8\testrulewidth
+     {\ifnegative\else\normalhss\fi
+      \visualvrule
+        \!!depth8\testrulewidth
+        \!!width\ifzero0\else4\fi\testrulewidth
+      \ifpositive\else\normalhss\fi}%
+   \setruledpenaltybox{2}{\scratchcounter}{0}{8}{-3.5}{4.5}%
+   \normalpenalty\!!tenthousand
+   \setbox0=\normalhbox
+     {\normalhskip-4\testrulewidth
+      \ifnegative
+        \box2\box0
+      \else
+        \box0\box2
+      \fi}%
+   \smashbox0%
+   \box0
+   \normalpenalty\scratchcounter
+   \egroup}
+
+\unexpanded\def\ruledhpenalty%
+  {\bgroup
+   \afterassignment\doruledhpenalty
+   \scratchcounter=}
+
+%D The size of a vertical penalty is also shown on the
+%D horizontal axis. This way there is less interference with
+%D the often preceding or following skips and kerns.
+%D
+%D \startbuffer
+%D first line
+%D \par \penalty +100
+%D second line
+%D \par \penalty +100
+%D \par \penalty -100
+%D third line
+%D \par \penalty    0
+%D fourth line
+%D \par \penalty +100
+%D fifth line
+%D \stopbuffer
+%D
+%D \ShowBufferedExample
+
+\def\doruledvpenalty%
+  {\ifdim\pagegoal=\maxdimen
+   \else
+     \nextdepth=\prevdepth  
+     \dontinterfere
+     \dontcomplain
+     \investigatecount\scratchcounter
+     \testrulewidth=2\testrulewidth
+     \boxrulewidth=\testrulewidth
+     \setbox0=\ruledhbox
+       {\visualvrule
+          \!!height4\testrulewidth
+          \!!depth4\testrulewidth
+          \!!width\!!zeropoint
+        \visualvrule
+          \!!height\ifnegative.5\else4\fi\testrulewidth
+          \!!depth\ifpositive.5\else4\fi\testrulewidth
+          \!!width8\testrulewidth}%
+     \setruledpenaltybox{2}{\scratchcounter}{4}{4}{.5}{.5}%
+     \setbox0=\normalhbox
+       {\normalhskip-4\testrulewidth
+        \ifnegative
+          \box2\box0
+        \else
+          \box0\box2
+        \fi
+        \normalhss}%
+     \smashbox0%
+     \normalpenalty\!!tenthousand
+     \nointerlineskip
+     \dp0=\nextdepth  % not \prevdepth=\nextdepth 
+     \normalvbox
+       {\normalvcue{\box0}}%
+   \fi
+   \normalpenalty\scratchcounter
+   \egroup}
+
+\unexpanded\def\ruledvpenalty%
+  {\bgroup
+   \afterassignment\doruledvpenalty
+   \scratchcounter=}
+
+\unexpanded\def\ruledpenalty%
+  {\ifvmode
+     \expandafter\ruledvpenalty
+   \else
+     \expandafter\ruledhpenalty
+   \fi}
+
+%D At the cost of some more tokens, a bit more clever 
+%D implementation would be:
+%D
+%D \starttypen
+%D \unexpanded\def\ruledpenalty%
+%D   {\csname ruled\ifvmode v\else h\fi penalty\endcsname}
+%D \stoptypen
+
+%D \macros
+%D   {showfils,dontshowfils,
+%D    showboxes,dontshowboxes,
+%D    showskips,dontshowskips,
+%D    showpenalties,dontshowpenalties}
+%D
+%D For those who want to manipulate the visual cues in detail,
+%D we have grouped them.
+
+\def\showfils%
+  {\let\hss      = \ruledhss
+   \let\hfil     = \ruledhfil
+   \let\hfill    = \ruledhfill
+   \let\hfilneg  = \ruledhfilneg
+   \let\hfillneg = \ruledhfillneg
+   \let\vss      = \ruledvss
+   \let\vfil     = \ruledvfil
+   \let\vfill    = \ruledvfill
+   \let\vfilneg  = \ruledvfilneg
+   \let\vfillneg = \ruledvfillneg}
+
+\def\dontshowfils%
+  {\let\hss      = \normalhss
+   \let\hfil     = \normalhfil
+   \let\hfill    = \normalhfill
+   \let\hfilneg  = \normalhfilneg
+   \let\hfillneg = \normalhfillneg
+   \let\vss      = \normalvss
+   \let\vfil     = \normalvfil
+   \let\vfill    = \normalvfill
+   \let\vfilneg  = \normalvfilneg
+   \let\vfillneg = \normalvfillneg}
+
+\def\showboxes%
+  {\baselineruletrue
+   \let\hbox     = \ruledhbox
+   \let\vbox     = \ruledvbox
+   \let\vtop     = \ruledvtop
+   \let\vcenter  = \ruledvcenter}
+
+\def\dontshowboxes%
+  {\let\hbox     = \normalhbox
+   \let\vbox     = \normalvbox
+   \let\vtop     = \normalvtop
+   \let\vcenter  = \normalvcenter}
+
+\def\showskips%
+  {\let\hskip    = \ruledhskip
+   \let\vskip    = \ruledvskip
+   \let\kern     = \ruledkern
+   \let\mskip    = \ruledmskip
+   \let\mkern    = \ruledmkern
+   \let\hglue    = \ruledhglue
+   \let\vglue    = \ruledvglue}
+
+\def\dontshowskips%
+  {\let\hskip    = \normalhskip
+   \let\vskip    = \normalvskip
+   \let\kern     = \normalkern
+   \let\mskip    = \normalmskip
+   \let\mkern    = \normalmkern
+   \let\hglue    = \normalhglue
+   \let\vglue    = \normalvglue}
+
+\def\showpenalties%
+  {\let\penalty  = \ruledpenalty}
+
+\def\dontshowpenalties%
+  {\let\penalty  = \normalpenalty}
+
+%D \macros
+%D   {showingcomposition,
+%D    showcomposition,dontshowcomposition}
+%D
+%D All these nice options come together in two macros. The
+%D first one turns the options on, the second turnes them off.
+%D Both macros only do their job when we are actually showing
+%D the composition.
+%D
+%D \starttypen
+%D \showingcompositiontrue
+%D \showcomposition
+%D \stoptypen
+%D 
+%D Because the output routine can do tricky things, like
+%D multiple column typesetting and manipulation of the
+%D pagebody, shifting things around and so on, the macro
+%D \type{\dontshowcomposition} best can be called when we enter
+%D this routine. Too much visual cues just don't make sense. In
+%D \CONTEXT\ this has been taken care of. 
+
+\newif\ifshowingcomposition
+
+\def\showcomposition%
+  {\ifshowingcomposition
+     \showfils
+     \showboxes
+     \showskips
+     \showpenalties
+   \fi}
+
+\def\dontshowcomposition%
+  {\ifshowingcomposition
+     \dontshowfils
+     \dontshowboxes
+     \dontshowskips
+     \dontshowpenalties
+   \fi}
+
+%D \macros
+%D   {showmakeup,
+%D    defaulttestrulewidth}
+%D
+%D Just to make things even more easy, we have defined:
+%D
+%D \starttypen
+%D \showmakeup
+%D \stoptypen
+%D
+%D For the sake of those who don't (yet) use \CONTEXT\ we 
+%D preset \type{\defaulttestrulewidth} to the already set 
+%D value. Otherwise we default to a bodyfontsize related value.
+%D
+%D \starttypen
+%D \def\defaulttestrulewidth{.2pt}
+%D \stoptypen
+%D
+%D Beware, it's a macro not a \DIMENSION.
+
+\ifx\korpsgrootte\undefined
+  \edef\defaulttestrulewidth{\the\testrulewidth}
+\else
+  \def\defaulttestrulewidth{.02\korpsgrootte}  % still dutch
+\fi
+
+\def\showmakeup%
+  {\testrulewidth=\defaulttestrulewidth
+   \showingcompositiontrue
+   \showcomposition}
+
+\protect
+
+%D \ifCONTEXT \let\next=\relax \else \let\next=\endinput 
+%D The documented source you have been reading was processed
+%D using some surrogate makeup. When this file is processed
+%D in \CONTEXT, a few more examples show up here, like a local
+%D table of contents and a local register. 
+%D \fi \next
+
+% %D Lets end with some more advanced examples. When visualized,
+% %D the table of contents of the outer level is typeset as:
+% %D
+% %D {\showmakeup\plaatsinhoud[criterium=vorige]}
+% %D
+%D Lets end with some more advanced examples. 
+%D Definitions and enumerations come in many flavors. The 
+%D next one for instance is defined as: 
+%D
+%D \starttypen
+%D \definedescription[test][place=left,hang=3,width=6em]
+%D \stoptypen
+%D
+%D When applied to some text, this would look like: 
+%D
+%D \bgroup
+%D \showmakeup
+%D \doordefinieren[test][plaats=links,hang=3,breedte=6em]
+%D
+%D \test{visual\\debugger} I would be very pleased if \TEX\
+%D had two more primitives: \type{\vnop} and \type{\hnop}. Both
+%D should act and show up as normal boxes, but stay invisible
+%D for \TEX\ when it's doing calculations. The \type{\vnop} 
+%D for instance should not interact with the internal mechanism 
+%D responsible for the disappearing skips, kerns and penalties
+%D at a pagebreak. As long as we don't have these two boxtypes, 
+%D visual debugging will never be perfect. 
+%D
+%D \egroup
+%D
+%D The index to this section looks like:
+%D
+%D {\stelrefererenin[prefix=dummy]\showmakeup\plaatsindex[criterium=lokaal]}
+%D
+%D Although not impressive examples or typesetting, both
+%D show us how and where things happen. When somehow the last
+%D lines in this two column index don't allign, then this is
+%D due to some still unknown interference.
+
+\endinput