%% This is part of the OpTeX project, see http://petr.olsak.net/optex

\_codedecl \chap {Titles, chapters, sections, subsections <2022-10-19>} % preloaded in format

   \_doc ---------------------------
   We are using scaled fonts for titles
   \`\_titfont`, \`\_chapfont`, \`\_secfont` and \`\_seccfont`.
   They are scaled from main fonts size
   of the document, which is declared by first `\typosize[<fo-size>/<b-size>]`
   command.
   \_cod ---------------------------

\_def \_titfont  {\_scalemain\_typoscale[\_magstep4/\_magstep5]\_boldify}
\_def \_chapfont {\_scalemain\_typoscale[\_magstep3/\_magstep3]\_boldify}
\_def \_secfont  {\_scalemain\_typoscale[\_magstep2/\_magstep2]\_boldify}
\_def \_seccfont {\_scalemain\_typoscale[\_magstep1/\_magstep1]\_boldify}

   \_doc ---------------------------
   The \`\tit` macro is defined using \^`\scantoeol` and \`\_printtit`.
   It means that the parameter is
   separated by end of line and inline verbatim is allowed. The same
   principle is used in the \^`\chap`, \^`\sec`, and \^`\secc` macros.
   \_cod ---------------------------

\_def\_printtit #1{\_vglue\_titskip
  {\_leftskip=0pt plus1fill \_rightskip=\_leftskip % centering
   \_titfont \_noindent \_scantextokens{#1}\_par}%
   \_nobreak\_bigskip
}
\_def\_tit{\_scantoeol\_printtit}
\_let\_intit=\_printtit  % used by \bracedparam

\_public \tit ;

   \_doc ---------------------------
   You can re-define \`\_printchap`, \`\_printsec` or \`\_printsecc` macros if
   another design of section titles is needed. These macros get the
   `<title>` text in its parameter. The common recommendations for these macros are:
   \begitems
   * Use \^`\_abovetitle``{<penaltyA>}{<skipA>}` and \^`\_belowtitle``{<skipB>}`
     for inserting vertical material above and below the section title.
     The arguments of these macros are normally used, i.\,e.\ \^`\_abovetitle`
     inserts `<penaltyA><skipA>` and \^`\_belowtitle` inserts `<skipB>`.
     But there is an
     exception: if \^`\_belowtitle``{<skipB>}` is immediately followed by
     \^`\_abovetitle``{<penaltyA>}{<skipA>}` (for example section title is
     immediately followed by subsection title), then only `<skipA>` is generated,
     i.\,e.\ `<skipB><penaltyA><skipA>` is reduced only to `<skipA>`.
     The reason for such behavior: we don't want to duplicate vertical skip
     and we don't want to use the negative penalty in such cases.
     Moreover, \^`\_abovetitle``{<penaltyA>}{<skipA>}` takes previous whatever
     vertical skip (other than from `\_belowtitle`) and generates only
     greater from this pair of skips. It means that `<whatever-skip><penaltyA><skipA>`
     is transformed to `<penaltyA>`max(`<whatever-skip><skipA>`).
     The reason for such behavior: we don't want to
     duplicate vertical skips (from `\_belowlistskip`, for example) above the title.
   * Use \^`\_printrefnum``[<pre>@<post>]` in horizontal mode. It prints
     `<pre><ref-num><post>`. The `<ref-num>` is \^`\_thechapnum` or \^`\_thesecnum`
     or \^`\_theseccnum` depending on what type o title is processed.
     If \^`\nonum` prefix is used then \^`\_printrefnum` prints nothing.
     The macro \^`\_printrefnum` does more work: it creates destination of hyperlinks
     (if \^`\hyperlinks``{}{}` is used) and saves references from the label (if
     \^`\label``[<label>]` precedes) and saves references for the table of contents
     (if \^`\maketoc` is used).
   * Use \^`\nbpar` for closing the paragraph for printing title. This
     command inserts `\_nobreak` between each line of such paragraph, so
     the title cannot be broken into more pages.
   * You can use \^`\_firstnoindent` in order to the first paragraph after
     the title is not indented.
   \enditems
   \_cod ---------------------------

\_def\_printchap #1{\_vfill\_supereject \_prevdepth=0pt
   \_vglue\_medskipamount % shifted by topkip+\medskipamount
   {\_chapfont \_noindent \_mtext{chap} \_printrefnum[@]\_par
    \_nobreak\_smallskip
    \_noindent \_raggedright #1\_nbpar}\_mark{}%
   \_nobreak \_belowtitle{\_bigskip}%
   \_firstnoindent
}
\_def\_printsec#1{\_par
   \_abovetitle{\_penalty-151}\_bigskip
   {\_secfont \_noindent \_raggedright \_printrefnum[@\_quad]#1\_nbpar}\_insertmark{#1}%
   \_nobreak \_belowtitle{\_medskip}%
   \_firstnoindent
}
\_def\_printsecc#1{\_par
   \_abovetitle{\_penalty-101}{\_medskip\_smallskip}
   {\_seccfont \_noindent \_raggedright \_printrefnum[@\_quad]#1\_nbpar}%
   \_nobreak \_belowtitle{\_medskip}%
   \_firstnoindent
}

   \_doc --------------------------
   The \`\_sectionlevel` is the level of the printed section:
   \begitems
   * `\_sectionlevel=0` -- reserved for parts of the book (unused by default)
   * `\_sectionlevel=1` -- chapters (used in `\chap`)
   * `\_sectionlevel=2` -- sections (used in `\sec`)
   * `\_sectionlevel=3` -- subsections (used in `\secc`)
   * `\_sectionlevel=4` -- subsubsections (unused by default, see the
     \ulink[http://petr.olsak.net/optex/optex-tricks.html\#seccc]{\OpTeX/ trick 0033})
   \enditems
   \_cod --------------------------

\_newcount\_sectionlevel
\_def \_secinfo {\_ifcase \_sectionlevel
   part\_or chap\_or sec\_or secc\_or seccc\_fi
}

   \_doc --------------------------
   The \`\_chapx` initializes counters used in chapters,
   the \`\_secx` initializes counters in sections
   and \`\_seccx` initializes counters in subsections.
   If you have more types of numbered objects in your document then you can
   declare appropriate counters and do `\addto\_chapx{\yourcounter=0 }`
   for example. If you have another concept of numbering objects used in your
   document, you can re-define these macros. All settings here are global
   because it is used by `{\_globaldefs=1 \_chapx}`.

   Default concept: Tables, figures, and display maths are numbered
   from one in each section -- subsections don't reset these counters.
   Footnotes declared by \^`\fnotenumchapters` are numbered in each chapter
   from one.

   The `\_the*` macros
   \`\_thechapnum`, \`\_thesecnum`, \`\_theseccnum`,
   \`\_thetnum`, \`\_thefnum` and \`\_thednum`
   include the format of numbers used when the object
   is printing. If chapter is never used in the document then `\_chapnum=0`
   and \`\_othe``\_chapnum.` expands to empty. Sections have numbers <num> and
   subsections <num>.<num>. On the other hand, if chapter is used in the
   document then `\_chapnum>0` and sections have numbers` <num>.<num>`
   and subsections have numbers `<num>.<num>.<num>`.
   \_cod --------------------------

\_newcount \_chapnum  % chapters
\_newcount \_secnum   % sections
\_newcount \_seccnum  % subsections
\_newcount \_tnum     % table numbers
\_newcount \_fnum     % figure numbers
\_newcount \_dnum     % numbered display maths

\_def \_chapx {\_secx  \_secnum=0  \_lfnotenum=0 }
\_def \_secx  {\_seccx \_seccnum=0 \_tnum=0 \_fnum=0 \_dnum=0 \_resetABCDE }
\_def \_seccx {}

\_def \_thechapnum {\_the\_chapnum}
\_def \_thesecnum  {\_othe\_chapnum.\_the\_secnum}
\_def \_theseccnum {\_othe\_chapnum.\_the\_secnum.\_the\_seccnum}
\_def \_thetnum    {\_othe\_chapnum.\_othe\_secnum.\_the\_tnum}
\_def \_thefnum    {\_othe\_chapnum.\_othe\_secnum.\_the\_fnum}
\_def \_thednum    {(\_the\_dnum)}

\_def\_othe #1.{\_ifnum#1>0 \_the#1.\_fi}

   \_doc ----------------------------
   The \`\notoc` and \`\nonum` prefixes are implemented by
   internal `\_ifnotoc` and `\_ifnonum`. They are reset
   after each chapter/section/subsection by the \`\_resetnonumnotoc` macro.
   \_cod ----------------------------

\_newifi \_ifnotoc  \_notocfalse  \_def\_notoc {\_global\_notoctrue}
\_newifi \_ifnonum  \_nonumfalse  \_def\_nonum {\_global\_nonumtrue}
\_def \_resetnonumnotoc{\_global\_notocfalse \_global\_nonumfalse}
\_public \notoc \nonum ;

   \_doc ----------------------------
   The \`\chap`, \`\sec`, and \`\secc` macros are implemented here.
   The \`\_inchap`, \`\_insec` and \`\_insecc` macros do the real work,
   First, we read the optional parameter `[<label>]`, if it exists.
   The `\chap`, `\sec` and `\secc` macro reads its parameter using
   \^`\scantoeol`. This causes that they cannot be used inside other macros.
   Use \^`\_inchap`, \^`\_insec`, and \^`\_insecc` macros directly in such case.
   \_cod ----------------------------

\_optdef\_chap[]{\_trylabel \_scantoeol\_inchap}
\_optdef\_sec []{\_trylabel \_scantoeol\_insec}
\_optdef\_secc[]{\_trylabel \_scantoeol\_insecc}
\_def\_trylabel{\_istoksempty\_opt\_iffalse \_label[\_the\_opt]\_fi}

\_def\_inchap #1{\_par \_sectionlevel=1
   \_def \_savedtitle {#1}% saved to .ref file
   \_ifnonum \_else {\_globaldefs=1 \_incr\_chapnum \_chapx}\_fi
   \_edef \_therefnum {\_ifnonum \_space \_else \_thechapnum \_fi}%
   \_printchap{\_scantextokens{#1}}%
   \_resetnonumnotoc
}
\_def\_insec #1{\_par \_sectionlevel=2
   \_def \_savedtitle {#1}% saved to .ref file
   \_ifnonum \_else {\_globaldefs=1 \_incr\_secnum \_secx}\_fi
   \_edef \_therefnum {\_ifnonum \_space \_else \_thesecnum \_fi}%
   \_printsec{\_scantextokens{#1}}%
   \_resetnonumnotoc
}
\_def\_insecc #1{\_par \_sectionlevel=3
   \_def \_savedtitle {#1}% saved to .ref file
   \_ifnonum \_else {\_globaldefs=1 \_incr\_seccnum \_seccx}\_fi
   \_edef \_therefnum {\_ifnonum \_space \_else \_theseccnum \_fi}%
   \_printsecc{\_scantextokens{#1}}%
   \_resetnonumnotoc
}
\_public \chap \sec \secc ;

   \_doc ----------------------------
   The \`\_printrefnum``[<pre>@<post>]` macro is used in `\_print*` macros.

   Note that the `<tite-text>` is `\detokenize`d before `\_wref`, so the
   problem of \"fragile macros" from old \LaTeX/ never occurs.
   This fourth parameter is not delimited by `{...}` but by end of line.
   This gives possibility to have unbalanced braces in inline verbatim in titles.
   \_cod ----------------------------

\_def \_printrefnum [#1@#2]{\_leavevmode % we must be in horizontal mode
   \_ifnonum \_else #1\_therefnum #2\_fi
   \_wlabel \_therefnum  % references, if `\label[<label>]` is declared
   \_ifnotoc \_else \_incr \_tocrefnum
       \_dest[toc:\_the\_tocrefnum]%
       \_ewref\_Xtoc{{\_the\_sectionlevel}{\_secinfo}%
                     {\_therefnum}{\_theoutline}\_detokenize\_ea{\_savedtitle}}%
   \_fi
   \_gdef\_theoutline{}%
}

   \_doc -----------------------------
   \`\thisoutline``{<text>}` saves text to the \`\_theoutline` macro.
   \^`\_printrefnum` uses it and removes it.
   \_cod -----------------------------

\_def\_theoutline{}
\_def\_thisoutline#1{\_gdef\_theoutline{#1}}
\_public \thisoutline ;

   \_doc -----------------------------
   The \`\_abovetitle``{<penaltyA>}{<skipA>}` and \`\_belowtitle``{<skipB>}` pair
   communicates using a special penalty 11333 in vertical mode.
   The `\_belowtitle` puts the vertical skip (its value is saved in
   `\_savedtitleskip`) followed by this special penalty.
   The `\_abovetitle` reads `\lastpenalty` and if it has this special value
   then it removes the skip used before and doesn't use the parameter.
   The `\abovetitle` creates `<skipA>` only if whatever previous skip is less
   or equal than `<skipA>`. We must save `<whatever-skip>`, remove it,
   create `<penaltyA>` (if `\_belowtitle` does not precede) and create
   <whatever-skip> or `<skipA>` depending on what is greater.
   The amount of `<skipA>` is measured using `\setbox0=\vbox`.
   \_cod -----------------------------

\_newskip \_savedtitleskip
\_newskip \_savedlastskip
\_def\_abovetitle #1#2{\_savedlastskip=\_lastskip % <whatever-skip>
   \_ifdim\_lastskip>\_zo \_vskip-\_lastskip \_fi
   \_ifnum\_lastpenalty=11333 \_vskip-\_savedtitleskip \_else #1\_fi
   \_ifdim\_savedlastskip>\_zo \_setbox0=\_vbox{#2\_global\_tmpdim=\_lastskip}%
   \_else \_tmpdim=\_maxdimen \_fi
   \_ifdim\_savedlastskip>\_tmpdim \vskip\_savedlastskip \_else #2\_fi
}
\_def\_belowtitle #1{#1\_global\_savedtitleskip=\_lastskip \_penalty11333 }

   \_doc -----------------------------
   \`\nbpar` sets `\interlinepenaty` value.
   \`\nl` is \"new line" in the text (or titles), but space in toc or headlines or outlines.
   \_cod -----------------------------

\_def\_nbpar{{\_interlinepenalty=10000\_endgraf}}

\_protected\_def\_nl{\_unskip\_hfil\_break}
\_regmacro {\_def\_nl{\_unskip\_space}} {\_def\_nl{\_unskip\_space}} {\_def\_nl{ }}
\_regmacro {\_def\nl{\_unskip\_space}}  {\_def\nl{\_unskip\_space}}  {\_def\nl{ }}

\_public \nbpar \nl ;

   \_doc -----------------------------
   \`\_firstnoindent` puts a material to `\everypar` in order to next
   paragraph will be without indentation. It is useful after titles.
   If you dislike this feature then you can say `\let\_firtnoindent=\relax`.
   The \`\_wipeepar` removes the material from `\everypar`.
   \_cod -----------------------------

\_def \_firstnoindent {\_global\_everypar={\_wipeepar \_setbox7=\_lastbox}}
\_def \_wipeepar {\_global\_everypar={}}

   \_doc -----------------------------
   The `\mark` (for running heads) is used in `\_printsection` only. We
   suppose that chapters will be printed after `\vfil\break`, so users can
   implement chapter titles for running headers directly by macros, no
   `\mark` mechanism is needed. But sections need `\mark`s. And they can be
   mixed with chapter's running heads, of course.

   The \`\_insertmark``{<title text>}` saves `\mark` in the format
   `{<title-num>} {<title-text>}`, so it can be printed \"as is" in
   `\headline` (see the space between them), or you can define a formating
   macro with two parameters for processing these data, if you need it.
   \_cod -----------------------------

\_def\_insertmark#1{\_mark{{\_ifnonum\_else\_therefnum\_fi} {\_unexpanded{#1}}}}

   \_doc -----------------------------
   \OpTeX/ sets `\headline={}` by default, so no running headings are printed.
   You can activate the running headings by following code, for example.
   See also \ulink[https://github.com/olsak/OpTeX/issues/100]{issue 100}.
   \begtt
   \addto\_chapx {\globaldefs=0 \vfil\break % headline of previous chapter is printed
      \xdef\_runningchap {\_thechapnum: \unexpanded\_ea{\_savedtitle}}}
   \def \formathead #1#2{\isempty{#1}\iffalse #1: #2\fi}
   \headline = {%
      \ifodd \pageno
          \hfil \ea\formathead\firstmark{}{}%
      \else
          \ifx\_runningchap\_undefined \else Chapter \_runningchap \fi \hfil
      \fi
   }
   \endtt

   The \`\secl``<number> <title-text><eol>`
   should be used for various levels of sections (for example, when
   converting from Markdown to \OpTeX/). `\secl1` is `\chap`, `\secl2` is `\sec`,
   `\secl3` is `\secc` and all more levels (for <number>$>3$)
   are printed by the common \`\_seclp` macro. It declares only a simple design.
   If there is a requirement to use such more levels then the book designer can
   define something different here.
   \_cod -----------------------------

\_def\_secl{\_afterassignment\_secla \_sectionlevel=}
\_def\_secla{\_ifcase\_sectionlevel
   \_or\_ea\_chap\_or\_ea\_sec\_or\_ea\_secc\_else\_ea\_seclp\_fi}
\_eoldef\_seclp#1{\_par \_ifnum\_lastpenalty=0 \_removelastskip\_medskip\_fi
   \_noindent{\_bf #1}\_vadjust{\_nobreak}\_nl\_ignorepars}
\_def\_ignorepars{\_isnextchar\_par{\_ignoresecond\_ignorepars}{}}

\_public \secl ;

   \_doc -----------------------------
   The \`\caption``/<letter>` increases `\_<letter>num` counter,
   edefines \`\_thecapnum` as `\_the<letter>num` and
   defines \`\_thecaptitle` as language-dependent word using \^`\_mtext`,
   declares default format by \^`\_captionformat``{<letter>}` and
   runs the `\_everycaption<letter>` tokens register.
   The two groups opened by `\caption` are finalized by first `\_par` from
   an empty line or from `\vskip`, `\cskip` or from `\endinsert`.
   If a \code{\}} occurs first then `\_par` from `\aftergroup` is processed.
   The `\_printcaption<letter>` is called, it starts with
   printing of the caption.\nl
   The \`\cskip` macro inserts nonbreakable vertical space between the caption and
   the object.
   \_cod -----------------------------

\_def\_caption/#1{\_def\_tmpa{#1}\_nospaceafter \_capA}
\_optdef\_capA []{\_trylabel \_incaption}
\_def\_incaption {\_bgroup
   \_ifcsname _\_tmpa num\_endcsname \_ea\_incr \_csname _\_tmpa num\_endcsname
   \_else \_opwarning{Unknown caption /\_tmpa}\_fi
   \_edef\_thecapnum {\_csname _the\_tmpa num\_endcsname}%
   \_edef\_thecaptitle{\_mtext{\_tmpa}}%
   \_ea\_captionformat\_ea{\_tmpa}%
   \_ea\_the \_csname _everycaption\_tmpa\_endcsname
   \_def\_par{\_ifhmode\_nbpar\_egroup\_egroup\_fi}%
   \_ifx\par\_endgraf \_let\par=\_par \_fi
   \_bgroup \_aftergroup\_par
   \_cs{_printcaption\_tmpa}%
}
\_def \_cskip {\_par\_nobreak\_medskip} % space between caption and the object

\_public \caption \cskip ;

   \_doc -----------------------------
   The \`\_printcaptiont` and \`\_printcaptionf` macros start in vertical mode.
   They switch to horizontal mode and use `\_wlabel\_thecapnum` (in order to
   make reference and hyperlink destination). They can use:
   \begitems
   * \^`\_thecaptitle` ... expands to the word Table or Figure (depending on
                           the current language).
   * \^`\_thecapnum` ...   expands to `\the<letter>num` (caption number).
   \enditems
   The macro \^`\_printcaptiont` (or `f`) is processed inside group and the
   `\_par` can be run after this group. If you want to re-define formating
   parameters for `\_par`, do this in the macro \^`\_captionformat`.
   The \`\_captionsep` inserts a separator between auto-generated
   caption number and the following caption text. Default separator
   is `\_enspace` but if the caption text starts with dot or colon, then
   the space is not inserted. A user can wite `\caption/t: My table`
   and \"{\bf Table 1.1:} My table" is printed. You can re-define
   the \^`\_captionsep` macro if you want to use another separator.
   \_cod -----------------------------

\_def \_printcaptiont {%
   \_noindent \_wlabel\_thecapnum {\_bf\_thecaptitle~\_thecapnum}%
   \_futurelet\_next\_captionsep
}
\_def\_captionsep{\_ifx\_next.\_ea\_bfnext \_else\_ifx\_next:\_ea\_ea\_ea\_bfnext
   \_else \_enspace \_fi\_fi}
\_def\_bfnext#1{{\_bf#1}}
\_let \_printcaptionf = \_printcaptiont % caption of figures = caption of tables

   \_doc -----------------------------
   If you want to declare a new type of `\caption` with independent counter,
   you can use following lines, where `\caption/a` for Algorithms are
   declared:
   \begtt
   \let\_printcaptiona = \_printcaptionf  \let\_everycaptiona = \_everycaptionf
   \newcount\_anum  \addto\_secx {\_anum=0 }
   \def\_theanum {\_othe\_chapnum.\_the\_secnum.\_the\_anum}
   \sdef{_mt:a:en}{Algorithm}  \sdef{_mt:a:cs}{Algoritmus} % + your language...
   \endtt
   The format of the \^`\caption` text is given by the
   \`\_captionformat``{<caption-letter>}` macro.
   The default format for `t` and `f` is a paragraph in block narrower by
   `\_iindent` and with the last line is centered. This setting is done by
   the \`\_narrowlastlinecentered` macro.
   \_cod -----------------------------

\_def\_captionformat#1{\_narrowlastlinecentered\_iindent}
\_def\_narrowlastlinecentered#1{%
   \_leftskip=#1plus1fil
   \_rightskip=#1plus-1fil
   \_parfillskip=0pt plus2fil\_relax
}

   \_doc -----------------------------
   \`\eqmark` is processed in display mode (we add `\eqno` primitive)
   or in internal mode when `\eqaligno` is used (we don't add `\eqno`).
   \_cod -----------------------------

\_optdef\_eqmark []{\_trylabel \_ineqmark}
\_def\_ineqmark{\_incr\_dnum
  \_ifinner\_else\_eqno \_fi
  \_wlabel\_thednum \_hbox{\_thednum}%
}
\_public \eqmark ;

   \_doc -----------------------------
   The \`\numberedpar` `<letter>{<name>}` is implemented here.
   \_cod -----------------------------

\_newcount\_counterA \_newcount\_counterB \_newcount\_counterC
\_newcount\_counterD \_newcount\_counterE

\_def\_resetABCDE {\_counterA=0 \_counterB=0 \_counterC=0 \_counterD=0 \_counterE=0 }

\_def \_theAnum {\_othe\_chapnum.\_othe\_secnum.\_the\_counterA}
\_def \_theBnum {\_othe\_chapnum.\_othe\_secnum.\_the\_counterB}
\_def \_theCnum {\_othe\_chapnum.\_othe\_secnum.\_the\_counterC}
\_def \_theDnum {\_othe\_chapnum.\_othe\_secnum.\_the\_counterD}
\_def \_theEnum {\_othe\_chapnum.\_othe\_secnum.\_the\_counterE}

\_def\_numberedpar#1#2{\_ea \_incr \_csname _counter#1\_endcsname
   \_def\_tmpa{#1}\_def\_tmpb{#2}\_numberedparparam}
\_optdef\_numberedparparam[]{%
   \_ea \_printnumberedpar \_csname _the\_tmpa num\_ea\_endcsname\_ea{\_tmpb}}

\_public \numberedpar ;

   \_doc -----------------------------
   The \`\_printnumberedpar` `\theXnum {<name>}` opens numbered paragraph and
   prints it. The optional parameter is in `\_the\_opt`. You can re-define
   it if you need another design.

   `\_printnumberedpar` needs not to be re-defined if you only want to print
   Theorems in italic and to insert vertical skips (for example). You can do this
   by the following code:
   \begtt
   \def\theorem    {\medskip\bgroup\it \numberedpar A{Theorem}}
   \def\endtheorem {\par\egroup\medskip}

   \theorem Let $M$ be... \endtheorem
   \endtt
   \_cod -----------------------------

\_def \_printnumberedpar #1#2{\_par
   \_noindent\_wlabel #1%
   {\_bf #2 #1\_istoksempty\_opt\_iffalse \_space \_the\_opt \_fi.}\_space
   \_ignorespaces
}

\_endcode % -------------------------------------

2022-10-19 More robust \caption (two opened groups, \_printcaption introduced)
2022-08-02 Penalties in \_printsec, \_printsecc changed
2022-07-11 \_printchap: \_prevdepth=0pt added, see issue 100
2021-03-03 \_captionsep introduced, \_othe used in \_thetnum, \_thefnum.
2021-02-09 \thisoutline implemented
2021-01-26 \_nl: \unskip added
2021-01-11 \secl introduced
2021-01-05 \_thednum printed in text mode in its both occurences.
2020-04-28 \_secfonts etc: \_boldify is last.
2020-04-22 \_chapx, \_secx, \_seccx rewritten
2020-03-14 introduced
