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+% \iffalse meta-comment
+%
+% Copyright 2019-2020
+% The LaTeX3 Project and any individual authors listed elsewhere
+% in this file.
+%
+% This file is part of the LaTeX base system.
+% -------------------------------------------
+%
+% It may be distributed and/or modified under the
+% conditions of the LaTeX Project Public License, either version 1.3c
+% of this license or (at your option) any later version.
+% The latest version of this license is in
+%    https://www.latex-project.org/lppl.txt
+% and version 1.3c or later is part of all distributions of LaTeX
+% version 2008 or later.
+%
+% This file has the LPPL maintenance status "maintained".
+%
+% The list of all files belonging to the LaTeX base distribution is
+% given in the file `manifest.txt'. See also `legal.txt' for additional
+% information.
+%
+% The list of derived (unpacked) files belonging to the distribution
+% and covered by LPPL is defined by the unpacking scripts (with
+% extension .ins) which are part of the distribution.
+%
+% \fi
+% Filename: ltnews31.tex
+%
+% This is issue 31 of LaTeX News.
+
+\NeedsTeXFormat{LaTeX2e}[2020-02-02]
+
+\documentclass{ltnews}
+\usepackage[T1]{fontenc}
+
+\usepackage{lmodern,url,hologo}
+
+\usepackage{csquotes}
+\usepackage{multicol}
+
+\providecommand\meta[1]{$\langle$\textit{#1}$\rangle$}
+\providecommand\option[1]{\texttt{#1}}
+\providecommand\env[1]{\texttt{#1}}
+
+
+\providecommand\XeTeX{\hologo{XeTeX}}
+\providecommand\LuaTeX{\hologo{LuaTeX}}
+\providecommand\pdfTeX{\hologo{pdfTeX}}
+\providecommand\MiKTeX{\hologo{MiKTeX}}
+\providecommand\CTAN{\textsc{ctan}}
+\providecommand\TL{\TeX\,Live}
+\providecommand\githubissue[2][]{\ifhmode\unskip\fi
+     \quad\penalty500\strut\nobreak\hfill
+     \mbox{\small\slshape(%
+       \href{https://github.com/latex3/latex2e/issues/\getfirstgithubissue#2 \relax}%
+          	    {github issue#1 #2}%
+           )}%
+     \par\smallskip}
+
+% simple solution right now (just link to the first issue if there are more)
+\def\getfirstgithubissue#1 #2\relax{#1}
+
+\providecommand\sxissue[1]{\ifhmode\unskip\fi
+     \quad\penalty500\strut\nobreak\hfill
+     \mbox{\small\slshape(\url{https://tex.stackexchange.com/#1})}\par}
+
+\providecommand\gnatsissue[2]{\ifhmode\unskip\fi
+     \quad\penalty500\strut\nobreak\hfill
+     \mbox{\small\slshape(%
+       \href{https://www.latex-project.org/cgi-bin/ltxbugs2html?pr=#1\%2F#2}%
+          	    {gnats issue #1/#2}%
+           )}%
+     \par}
+
+\let\cls\pkg
+\providecommand\env[1]{\texttt{#1}}
+
+\vbadness=1400  % accept slightly empty columns
+
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\iffalse % only for TUB production
+\usepackage{graphicx}
+\makeatletter
+% Xe\TeX{} requires reflecting the first E, hence we complain if the
+% graphics package is not present.  (For plain documents, this can be
+% loaded via Eplain.)  Also, at Barbara's suggestion, if the current
+% font is slanted, we rotate by 180 instead of reflecting so there is at
+% least a chance to look ok.  (The magic values here seem more or less
+% ok for \texttt{cmsl} and \texttt{cmti}.)
+%
+%    \begin{macrocode}
+\def\tubreflect#1{%
+  \@ifundefined{reflectbox}{%
+    \TBerror{A graphics package must be loaded for \string\XeTeX}%
+  }{%
+    \ifdim \fontdimen1\font>0pt
+      \raise 1.6ex \hbox{\kern.1em\rotatebox{180}{#1}}\kern-.1em
+    \else
+      \reflectbox{#1}%
+    \fi
+  }%
+}
+\def\tubhideheight#1{\setbox0=\hbox{#1}\ht0=0pt \dp0=0pt \box0 }
+\def\XekernbeforeE{-.125em}
+\def\XekernafterE{-.1667em}
+\DeclareRobustCommand{\Xe}{\leavevmode
+  \tubhideheight{\hbox{X%
+    \setbox0=\hbox{\TeX}\setbox1=\hbox{E}%
+    \ifdim \fontdimen1\font>0pt \def\XekernbeforeE{0em}\fi
+    \lower\dp0\hbox{\raise\dp1\hbox{\kern\XekernbeforeE\tubreflect{E}}}%
+    \kern\XekernafterE}}}
+\def\XeTeX{\Xe\TeX}
+\def\XeLaTeX{\Xe{\kern.11em \LaTeX}}
+\fi
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\publicationmonth{February}
+\publicationyear{2020}
+
+\publicationissue{31}
+
+\begin{document}
+
+%\addtolength\textheight{4.2pc}   % only for TUB
+
+\maketitle
+{\hyphenpenalty=10000 \spaceskip=3.33pt \hbadness=10000 \tableofcontents}
+
+\setlength\rightskip{0pt plus 3em}
+
+
+\medskip
+
+
+%\section{Introduction}
+%
+%This document is under construction \ldots
+
+
+\section{Experiences with the \LaTeX\ \texttt{-dev} formats}
+
+As reported in the previous \emph{\LaTeX{} News}, we have made a pre-release
+version of the \LaTeX{} kernel available as \LaTeX\texttt{-dev}. Overall, the
+approach of having an explicit testing release has been positive: it is now
+readily available in \TeX{} systems and is getting real use\\
+beyond the team.
+
+The current
+release has been tested by a number of people, and we have had valuable feedback
+on a range of the new ideas. This has allowed us to fix issues in several of the
+new features, as described below.
+
+
+We wish to thank all the dedicated users who have been
+trying out the development formats, and we encourage others to do so. Pre-testing
+in this way does mean that, for the vast majority of users, problems are solved
+before they even appear!
+
+
+\section{Concerning this release \ldots (Lua\LaTeX{} engine)}
+
+The new LuaHB\TeX{} engine is Lua\TeX{} with an embedded HarfBuzz library.
+HarfBuzz can be used by setting a suitable renderer in the font
+declaration. A basic interface for that is provided by \pkg{fontspec}.
+This additional font renderer will greatly improve the shaping of
+various scripts when using Lua\LaTeX{}, many of which are currently handled correctly only by
+\XeTeX{}, which always uses HarfBuzz.
+
+To simplify testing of the new engine, binaries have
+already been added to MiK\TeX{} and \TeX{}~Live 2019 and both distributions have already now changed
+the Lua\LaTeX-dev format to use it.
+
+Going forward, Lua\LaTeX\ (and Lua\LaTeX-dev) will both use the LuaHB\TeX{}
+engine.
+The timing of the switch to the LuaHB\TeX{} engine
+depends on the distribution you use
+(for \TeX{}~Live this will be with \TeX{}~Live 2020).
+
+
+
+
+\section{Improved load-times for \pkg{expl3}}
+
+The \LaTeX3 programming layer, \pkg{expl3}, has over the past decade moved from
+being largely experimental to broadly stable. It is now used in a significant
+number of third-party packages, most notably \pkg{xparse}, for defining
+interfaces in cases where no \pkg{expl3} code is \enquote{visible}. In addition, most
+\LaTeX{} documents compiled using \XeTeX{} or \LuaTeX{} load \pkg{fontspec},
+which is written using \pkg{expl3}.
+
+The \pkg{expl3} layer contains a non-trivial number of macros, and when used
+with the \XeTeX{} and \LuaTeX{} engines, it also loads a large body of Unicode data.
+This means that even on a fast computer, there is a relatively large load time when
+using \pkg{expl3}.
+
+For this release, the team have made adjustments in the \LaTeXe{} kernel to
+pre-load a significant portion of \pkg{expl3} when the format is built. This is
+transparent to the user, other than the significant decrease in document
+processing time: there will be no \enquote{pause} whilst loading the Unicode data
+files. Loading \pkg{expl3} in documents and packages can continue to be done as usual;
+eventually, it will be possible to omit
+\begin{verbatim}
+\RequirePackage{expl3}
+\end{verbatim}
+entirely but, to support older formats, this is still recommended at present.
+
+
+\section[Improvements to \LaTeX{} font selection: NFSS]
+        {Improvements to \LaTeX{}'s font selection\\ mechanism (NFSS)}
+
+
+\subsection{Extending the shape management in NFSS}
+
+Over time, more and more fonts have become available for use with
+\LaTeX{}. Many such font families offer additional shapes such as small
+caps italic (\texttt{scit}), small caps slanted (\texttt{scsl}) or
+swash (\texttt{sw}).
+By using \cs{fontshape} those shapes can
+be explicitly selected. For the swash shapes there is also
+\cs{swshape} and \cs{textsw} available.
+
+In the original font selection implementation a request to select a new shape
+always overrode the current shape. With the 2020 release of \LaTeX{}
+this has changed and \cs{fontshape} can now be used to combine small
+capitals with italic, slanted or swash letters, either by explicitly
+asking for \texttt{scit}, etc., or by asking for italics when typesetting
+already in small caps, and so forth.
+
+Using \cs{upshape} will still change italics or slanted back to an
+upright shape but will not any longer alter the small caps setting. To
+change small capitals back to upper/lower case you can now use
+\cs{ulcshape} (or \cs{textulc}) which in turn will not change the font
+with respect to italics, slanted or swash.
+%
+There is one exception: for compatibility reasons \cs{upshape} will
+change small capitals back to upright (\texttt{n} shape), if the
+current shape is \texttt{sc}. This is done so that something like
+\cs{scshape}\allowbreak\texttt{...}\allowbreak\cs{upshape} continues
+to work as before, but we suggest that you don't use that deprecated method in
+new documents.
+
+
+Finally, if you want to
+reset the shape back to normal you can use \cs{normalshape} which is a
+shorthand for \cs{upshape}\cs{ulcshape}.
+
+The way that shapes combine with each other is not hardwired; it is
+customizable and extensible if there is ever a need for this. The
+mappings
+are defined through \cs{DeclareFontShapeChangeRule} and the
+details for developers are documented in \texttt{source2e.pdf}.
+
+The ideas for this interface extension have been pioneered in
+\pkg{fontspec} by Will Robertson for Unicode engines, and in
+\pkg{fontaxes} by Andreas Bühmann and Michael Ummels for \pdfTeX{};
+they are by now used in many font support packages.
+
+
+\subsection{Extending the font series management in NFSS}
+
+Many of the newer font families also come provided with additional
+weights (thin, semi-bold, ultra-bold, etc.)\ or several running widths,
+such as condensed or extra-condensed.  In some cases the number of
+different values for series (weight plus width) is really impressive:
+for example, Noto Sans
+offers 36 fonts, from ultra-light extra condensed to ultra-bold medium width.
+
+Already in its original design, NFSS supported 9 weight levels, from
+ultra-light (\texttt{ul}) to ultra-bold (\texttt{ub}), and also 9 width
+levels, from ultra-condensed (\texttt{uc}) to ultra-expanded
+(\texttt{ux}):  more than enough, even for a font family like Noto
+Sans. Unfortunately, some font support packages nevertheless invented
+their own names, so in recent years you have been able to find all kinds of
+non-standard series names (\texttt{k}, \texttt{i}, \texttt{j} and
+others), making it impossible to combine different fonts successfully
+using the standard NFSS mechanisms.
+
+Over the course of the last year a small number of individuals,
+notably, Bob Tennent, Michael Sharpe and Marc Penninga, have worked hard to
+bring this unsatisfactory situation back under control; so today we are
+happy to report that the internal font support files for more than a
+hundred font families are all back to following the standard NFSS conventions.
+Combining them is now again rather nice and easy, and from a technical
+perspective they can now be easily matched; but, of course,
+there is still the task of choosing combinations that visually work
+well together.
+
+In the original font selection implementation, a request to select a new series
+always overrode the current one. This was reasonable because there
+were nearly no fonts available that offered anything other than a
+medium or a bold series. Now that this has changed and families such
+as Noto Sans are available, combining weight and width into a single
+attribute is no longer appropriate. With the 2020 release of \LaTeX{},
+the management of series therefore changed to allow independent
+settings of the weight and the width attributes of the series.
+
+For most users this change will be largely transparent as \LaTeX{}
+offers only \cs{textbf} or \cs{bfseries} to select a bolder face (and
+\cs{textmd} and \cs{mdseries} to return to a medium series): there is no
+high-level command for selecting a condensed face, etc. However, using
+the NFSS low-level interface it is now possible to ask for, say,
+\verb=\fontseries{c}\selectfont= to get a condensed
+face (suitable for a marginal note) and that would still allow
+the use of \cs{textbf} inside the note, which would
+select a bold-condensed face (and not a rather odd-looking
+bold-extended face in the middle of condensed type).
+
+The expectation is that this functionality will be used largely by
+class and package designers but, given that the low-level NFSS
+commands are usable on the document level and that they are not really
+difficult to apply, there are probably also a number of users who will
+enjoy using these new possibilities that bring \LaTeX{} back into the
+premier league for font usage.
+
+The ways in which the different series values combine with each other is not
+hardwired but is again customizable and extensible. The mappings are
+defined through \cs{DeclareFontSeriesChangeRule} and the details for
+developers are documented in \texttt{source2e.pdf}.
+
+
+\subsection{Font series defaults per document family}
+
+With additional weights and widths now being available in
+many font families, it is more likely that somebody will want to
+match, say, a medium weight serif family with a semi-light sans serif
+family, or that with one family one wants to use the bold-extended
+face when \cs{textbf} is used, while with another it should be bold
+(not extended) or semibold, etc.
+
+In the past this kind of extension was provided by Bob Tennent's
+\pkg{mweights} package, which has been used in many font
+support packages.
+With the 2020 release of \LaTeX{} this feature is now available out
+of the box.  In addition we also offer a document-level interface to adjust the
+behavior of the high-level series commands \cs{textbf}, \cs{textmd}, and of their
+declaration forms \cs{bfseries} and \cs{mdseries}, so that they can
+have different effects for the serif, sans serif and typewriter
+families used in a document.
+
+For example, specifying
+\begin{verbatim}
+  \DeclareFontSeriesDefault[rm]{bf}{sb}
+  \DeclareFontSeriesDefault[tt]{md}{lc}
+\end{verbatim}
+in the document preamble would result in \cs{textbf} producing
+semi-bold (\texttt{sb}) when typesetting in a roman typeface.
+The second line says that the
+typewriter default face (i.e., the medium series \texttt{md}) should be
+a light-condensed face. The optional argument here can be either
+\texttt{rm}, \texttt{sf} or \texttt{tt} to indicate one of the three
+main font families in a document; if omitted you will change the
+overall document default instead.  In the first mandatory argument you
+specify either \texttt{md} or \texttt{bf} and the second mandatory
+argument then gives the desired series value in NFSS nomenclature.
+
+
+\subsection{Handling of nested emphasis}
+
+In previous releases of \LaTeX{}, nested \cs{emph} commands
+automatically alternated between italics and upright.  This mechanism
+has now been generalised so that you can now specify for arbitrary nesting
+levels how emphasis should be handled.
+
+The declaration \cs{DeclareEmphSequence} expects a comma separated
+list of font declarations corresponding to increasing levels of
+emphasis. For example,
+\begin{verbatim}
+  \DeclareEmphSequence{\itshape,%
+               \upshape\scshape,\itshape}
+\end{verbatim}
+uses italics for the first, small capitals for the second, and italic
+small capitals for the third level (provided you use a font that
+supports these shapes).  If there are more nesting levels than
+provided, \LaTeX{} uses the declarations stored in \cs{emreset} (by
+default \cs{ulcshape}\cs{upshape}) for the next level and then
+restarts the list.
+
+The mechanism tries to be \enquote{smart} by verifying that the given
+declarations actually alter the current font. If not, it continues and
+tries the next level---the assumption being that there was already a
+manual font change in the document to the font that is now supposed to
+be used for emphasis.
+%
+Of course, this only works if the declarations in the list's entries
+actually change the font and not, for example, just the color. In such
+a scenario one has to add \cs{emforce} to the entry, which directs the
+mechanism to use the entry, even if the font attributes appear to be
+unchanged.
+
+
+\subsection{Providing font family substitutions}
+
+Given that \pdfTeX{} can only handle fonts with up to 256 glyphs, a
+single font encoding can only support a few languages. The \texttt{T1}
+encoding, for example, does support many Latin-based scripts,
+but if you want to write in Greek or Cyrillic then you will need to switch
+encodings to \texttt{LGR} or \texttt{T2A}. Given that not every font
+family offers glyphs in such encodings, you may end up with some
+default family (e.g., Computer Modern) that doesn’t blend in well
+with the chosen document font.  For such cases NFSS now offers
+\cs{DeclareFontFamilySubstitution}, for example:
+\begin{verbatim}
+  \DeclareFontFamilySubstitution{LGR}
+       {Montserrat-LF}{IBMPlexSans-TLF}
+\end{verbatim}
+tells \LaTeX{} that if you are typesetting in the sans serif font
+\texttt{Montserrat-LF} and the Greek encoding \texttt{LGR} is asked
+for, then \LaTeX{} should use \texttt{IBMPlexSans-TLF} to fulfill
+the encoding request.
+
+The code is based on ideas from the \pkg{substitutefont}
+package by Günter Milde, but the implementation is different.
+
+
+\subsection{Providing all text companion symbols by default}
+
+The text companion encoding \texttt{TS1} was originally not available
+by default, but only when the \pkg{textcomp} package was loaded. The
+main reason for this was limited availability of fonts with this encoding other than
+Computer Modern; another was the memory restrictions back in the nineties.
+These days neither limitation remains, so with the 2020 release all
+the symbols provided with the \pkg{textcomp} package are available out
+of the box.
+
+Furthermore, an intelligent substitution mechanism has been
+implemented so that glyphs missing in some fonts are automatically
+substituted with default glyphs that are sans serif if you typeset in
+\cs{textsf} and monospaced if you typeset using \cs{texttt}. In the
+past they were always taken from Computer Modern Roman if substitution
+was necessary.
+
+
+\typeout{^^J^^J***************************************}
+\typeout{** This example needs LaTeX 2020-02-02}
+\typeout{** to come out correctly !!}
+\typeout{***************************************^^J^^J}
+
+\textsf{This is most noticeable with \cs{oldstylenums} which are now
+  taken from \texttt{TS1} so that you no longer get
+  \textrm{\oldstylenums{1234}} but \oldstylenums{1234} when typesetting
+  in sans serif fonts}\texttt{ and \oldstylenums{1234} when using
+  typewriter fonts.}
+
+If there ever is a need to use the original (inferior) definition,
+then that remains available as \cs{legacyoldstylenums}; and to fully
+revert to the old behavior there is also
+\cs{UseLegacyTextSymbols}. The latter declaration reverts \cs{oldstylenums}
+and also changes the footnote symbols, such as \cs{textdagger},
+\cs{textparagraph}, etc., to pick up their glyphs from the math
+fonts instead of the current text font (this means they always keep
+the same shape and do not nicely blend in with the text font).
+
+With the text companion symbols as part of the kernel, it is normally
+no longer necessary to load the \pkg{textcomp} package, but for
+backwards compatibility this package will remain available.  There is,
+however, one use case where it remains useful: if you load the package
+with the option \texttt{error} or \texttt{warn} then substitutions
+will change their behavior and result in a \LaTeX{} error or a
+\LaTeX{} warning (on the terminal), respectively. Without the package
+the substitution information only appears in the \texttt{.log}
+file. If you use the option \texttt{quiet}, then even the information in
+the transcript is suppressed (which is not really recommended).
+
+
+
+\subsection{New \texttt{alias} size function for use in \texttt{.fd} files}
+
+% These are really called ``size functions'' in NFSS, a bit weird I know
+
+Most of the newer fonts supported in \TeX{} have been set up with the
+\texttt{autoinst} tool by Marc Penninga. In the past, this program
+set up each font  using the face name chosen by that font's designer,
+e.g., \enquote{\texttt{regular}}, \enquote{\texttt{bold}}, etc.
+These face names were then mapped by substitution to
+the standard NFSS series names, i.e., \enquote{\texttt{m}}
+or \enquote{\texttt{b}}.
+As a result one got unnecessary substitution warnings such as
+\enquote{\texttt{Font T1/abc/bold/n not found, using T1/abc/b/n instead}}.
+
+%FMi the message above is actually different and longer but ...
+
+We now provide a new NFSS  size function, \texttt{alias}, that can
+and will be used by \texttt{autoinst} in the future. It provides the
+same functionality as the \texttt{subst} function but is less vocal
+about its actions, so that only significant font substitutions show
+up as warnings.
+
+
+\subsection{Suppress unnecessary font substitution warnings}
+
+Many sans serif fonts do not have real italics but usually only
+oblique/slanted shapes, so the substitution of slanted for italics is
+natural and in fact many designers talk about italic sans serif faces
+even if in reality they are oblique.
+
+With nearly all sans serif font families, the \LaTeX{} support files
+therefore silently substitute slanted if you ask for \cs{itshape} or
+\cs{textit}.  This is also true for Computer Modern in \texttt{T1}
+encoding but in \texttt{OT1} you got a warning on the terminal even
+though there is nothing you can do about it. This has now been changed
+to an information message only, written to the \texttt{.log} file.  %
+\githubissue{172}
+
+\vspace{-\smallskipamount}
+\pagebreak
+
+\section{Other changes to the \LaTeX{} kernel}
+
+
+\subsection{UTF-8 characters in package descriptions}
+
+In 2018 we made UTF-8 the default input encoding for \LaTeX{} but we
+overlooked the case of non-ASCII characters in the short
+package descriptions used in declarations, e.g., in the optional argument to
+\cs{ProvidesPackage}.
+They worked (sometimes) before, but the switch to UTF-8 made them always
+generate an error.
+This has been corrected.
+%
+\githubissue{52}
+
+
+\subsection[Fix inconsistent hook setting when\texorpdfstring{\\}{} loading packages]%
+           {Fix inconsistent hook setting when loading packages}
+
+As part of loading a package, the command
+\texttt{\textbackslash}\textit{package}\texttt{.sty-h@@k} gets
+defined.  However, attempting to load a package a second time resulted
+in this hook becoming undefined again.  Now the hook remains defined
+so that extra loading attempts do not change the state of
+\LaTeX{} (relevant only to package developers).
+%
+\githubissue{198}
+
+
+\subsection{Avoid spurious warning if \texttt{LY1} is made the default encoding}
+
+Making \texttt{LY1} the default encoding, as is done by some font support
+packages, gave a spurious warning even if \cs{rmdefault} was changed first.
+This was corrected.
+%
+\githubissue{199}
+
+\enlargethispage{-\smallskipamount}
+\vspace{-\medskipamount}
+
+\subsection{Ensure that \cs{\textbackslash} remains robust}
+
+In the last release we made most document-level commands robust, but
+\cs{\textbackslash} became fragile again\\
+whenever  \cs{raggedright} or similar typesetting\\
+was used. This has been fixed.
+%
+\githubissue{203}
+
+
+\subsection{Make math delimiters robust in a different way}
+
+Making math delimiters robust caused an issue in some situations. This
+has been corrected. This also involved a correction to \pkg{amsmath}.
+%
+\githubissue{251}
+
+
+\subsection{Allow more write streams with \texttt{filecontents} in \LuaTeX}
+
+Most \TeX{} engines only support a maximum of sixteen concurrently
+open write streams, and when those have been used up, then
+\texttt{filecontents} or any other code trying to open one
+will fail.
+In \LuaTeX{} more write streams are available and those can
+also now be utilised.
+%
+\githubissue{238}
+
+\subsection{Allow spaces in \texttt{filecontents} option list}
+
+Leaving spaces or newlines in the option list prevented the options
+from being correctly recognized. This\\ 
+has been corrected.
+%
+\githubissue{256}
+
+
+\subsection{New \texttt{reverselist} Lua callback type}
+
+A new callback type, \texttt{reverselist}, was added:\\ 
+\texttt{post\_mlist\_to\_hlist\_filter} and \texttt{post\_linebreak\_filter} 
+are now of this type.
+
+
+\section{Changes to packages in the \pkg{graphics} category}
+
+\subsection[Make \pkg{color}/\pkg{graphics} user-level commands robust]
+           {Make \pkg{color} \& \pkg{graphics} user-level commands robust}
+
+Some of the user-level commands in \pkg{color}, \pkg{graphics} and
+\pkg{graphicx},
+%\pagebreak
+such as \cs{textcolor} or \cs{includegraphics}, were
+still fragile so didn't work in moving arguments.\\
+All of these are now robust.
+%
+\githubissue{208}
+
+
+\section{Changes to packages in the \pkg{tools} category}
+
+\subsection{Fixed column depth in boxed \texttt{multicols}}
+
+The \texttt{multicols} environment was setting \cs{maxdepth} when
+splitting boxes; but, due to the way the internal interfaces of \LaTeX{} are
+designed, it should have used \cs{@maxdepth} instead. As a result,
+balanced boxed multicols sometimes ended up having different heights
+even if they had exactly the same content.
+%
+\githubissue{190}
+
+
+\subsection{Ensure that \texttt{multicols} does not lose text}
+
+The \texttt{multicols} environment needs a set of consecutively numbered boxes to
+collect column material. The way those got allocated could result in
+disaster if other packages allocated most boxes below box~255 (which
+\TeX{} always uses for the output page).  In the original
+implementation that problem was avoided because one could only
+allocate box numbers below~255, but nowadays the \LaTeX{} allocation routine
+allows allocating box numbers both below and above~255. So the assumption that
+when asking for, say, 20~boxes you always get a consecutive sequence of~20 box
+register numbers became no longer true:
+some of the column material could
+end up in box~255, where it would get overwritten. This has now been corrected by
+allocating all necessary boxes with numbers above~255 whenever there aren't enough
+lower-numbered registers available.
+%
+\githubissue{237}
+
+\subsection{Allow spaces in \cs{hhline} arguments}
+
+The \verb|\hhline| command, which allows the
+specification of rule segments in \texttt{tabular} environments, now
+allows (but ignores) spaces between its tokens: so
+\verb|\hhline{: = : =}| is now allowed and is equivalent to
+\verb|\hhline{:=:=}|. This matches similar token arguments in \LaTeX{}
+such as the \verb|[h t p]| argument on floats.  A similar change has
+been made to the extended \verb|\hhline| command in the
+\texttt{colortbl} package.
+%
+\githubissue{242}
+
+
+
+\section{\LaTeX{} requirements on engine primitives}
+
+Since the finalization of \eTeX{} in 1999, a number of additional `utility'
+primitives have been added to \pdfTeX{}. Several of these are broadly useful
+and have been required by \pkg{expl3} for some time, most notably
+\cs{pdfstrcmp}. Over time, a common set of these `post-\eTeX{}' primitives have
+been incorporated into \XeTeX{} and (u)p-\TeX{}; they were  already available in
+\LuaTeX{}.
+
+A number of these additional primitives are needed to support new or improved
+functionality in \LaTeX{}. This is seen for example in the improved UTF-8 handling,
+which uses \cs{ifincsname}. The following primitive
+functionality (which in \LuaTeX{} may be achieved using Lua code)
+will therefore be \emph{required} by the \LaTeX{} kernel and core\\
+packages from the start of 2021:
+%
+\begingroup\setlength\columnsep{0pt}
+\begin{multicols}{2}
+\fontsize{9.3}{11.3}\selectfont
+\begin{itemize}
+  \item \cs{expanded}
+  \item \cs{ifincsname}
+  \item \cs{ifpdfprimitive}
+  \item \cs{pdfcreationdate}
+  \item \cs{pdfelapsedtime}
+  \item \cs{pdffiledump}
+  \item \cs{pdffilemoddate}
+  \item \cs{pdffilesize}
+  \item \cs{pdflastxpos}
+  \item \cs{pdflastypos}
+  \item \cs{pdfmdfivesum}
+  \item \cs{pdfnormaldeviate}
+  \item \cs{pdfpageheight}
+  \item \cs{pdfpagewidth}
+%\end{itemize}
+%\end{multicols}
+%
+% very manual! multicol needs update to detect that it is used
+% inside twocolumn!
+%
+%\begin{multicols}{2}
+%\begin{itemize}
+  \item \cs{pdfprimitive}
+  \item \cs{pdfrandomseed}
+  \item \cs{pdfresettimer}
+  \item \cs{pdfsavepos}
+  \item \cs{pdfsetrandomseed}
+  \item \cs{pdfshellescape}
+  \item \cs{pdfstrcmp}
+  \item \cs{pdfuniformdeviate}
+\end{itemize}
+\end{multicols}
+\endgroup
+For ease of reference, these primitives will be referred to as the
+`\pdfTeX{} utilities'. With the exception of \cs{expanded}, these have been
+present in \pdfTeX{} since the release of version 1.40.0 in 2007; \cs{expanded}
+was added for \TeX{}~Live 2019. Similarly, the full set of these utility primitives
+has been available in \XeTeX{} from the 2019 \TeX{}~Live release, and has
+always been available in \LuaTeX{} (some by Lua emulation).
+%
+The Japanese p\TeX{} and
+up\TeX{} gained all of the above (except \cs{ifincsname}) for \TeX{}~Live
+2019 and will both have that primitive also from the 2020 release onward.
+
+At the same time, engines which are fully Unicode-capable must provide
+the following three primitives:
+
+\vspace{-\smallskipamount}
+\begingroup\setlength\columnsep{0pt}
+\begin{multicols}{2}
+\fontsize{9.3}{11.3}\selectfont
+\begin{itemize}
+  \item \cs{Uchar}
+  \quad \textbullet{}\hspace{\labelsep}\cs{Ucharcat}
+  \item \cs{Umathcode}
+\end{itemize}
+\end{multicols}
+\vspace{-\smallskipamount}
+\endgroup
+%
+Note that it has become standard practice to check for Unicode-aware engines
+by using the existence of the \cs{Umathcode} primitive. As such, this is already
+a requirement: engines lacking these primitives cannot use Unicode features
+of the \LaTeXe{} kernel or \pkg{expl3}. Note also that up\TeX{} can
+handling Unicode but it is not classed as a Unicode engine by the 
+base \LaTeX\ code.
+
+\enlargethispage*{\baselineskip}
+\vspace{3.9pt}               % manual adjustment to align the bottom
+
+
+\begin{thebibliography}{9}
+
+\fontsize{9.3}{11.3}\selectfont
+
+\bibitem{31:devformat} Frank Mittelbach:
+  \emph{The
+  \LaTeX{} release workflow and the \LaTeX{} dev formats}.
+  In: TUGboat, 40\#2, 2019.
+  \url{https://latex-project.org/publications/}
+
+\bibitem{31:fntguide} \LaTeX{} Project Team:
+  \emph{\LaTeXe{} font selection}.\\
+  \url{https://latex-project.org/help/documentation/fntguide.pdf}
+
+\bibitem{31:site-doc}
+  \emph{\LaTeX{} documentation on the \LaTeX{} Project Website}.\\
+  \url{https://latex-project.org/help/documentation/}
+
+\end{thebibliography}
+
+
+\end{document}