trunk/doc/ltnews23.tex

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  29 % Filename: ltnews23.tex
  30 %
  31 % This is issue 23 of LaTeX News.
  32
  33 \documentclass{ltnews}
  34 \usepackage[T1]{fontenc}
  35
  36 \usepackage{lmodern,url,hologo}
  37
  38 \makeatletter % -- provide command introduced in new release
  39               %    so this typesets with an old format
  40
  41 % Check we are not in the preamble of a composite document
  42 \def\@tempa{\@latex@error{Can be used only in preamble}\@eha}
  43 \ifx\DeclareTextCommandDefault\@tempa
  44 \else
  45   \DeclareTextCommandDefault\textcommabelow[1]
  46     {\hmode@bgroup\ooalign{\null#1\crcr\hidewidth\raise-.31ex
  47      \hbox{\check@mathfonts\fontsize\ssf@size\z@
  48      \math@fontsfalse\selectfont,}\hidewidth}\egroup}
  49 \fi
  50 \makeatother
  51
  52 \publicationmonth{October}
  53 \publicationyear{2015}
  54
  55 \publicationissue{23}
  56
  57 \begin{document}
  58
  59 \maketitle
  60
  61 \tableofcontents
  62
  63 \section{Enhanced support for \hologo{LuaTeX}}
  64
  65 As noted in \LaTeX\ News 22, the 2015/01/01 release of \LaTeX{}
  66 introduced built-in support for extended \TeX\ systems.
  67
  68 The range of allocated register numbers (for example, for count
  69 registers) is now set according to the underlying engine capabilities
  70 to 256, 32768 or 65536. Additional allocators were also added for the
  71 facilities added by \hologo{eTeX} (\verb|\newmark|) and \hologo{XeTeX}
  72 (\verb|\newXeTeXintercharclass|). At that time, however, the work to
  73 incorporate additional allocators for \hologo{LuaTeX} was not ready for
  74 distribution.
  75
  76 The main feature of this release is  that by default it includes
  77 allocators for \hologo{LuaTeX}-provided features, such as Lua
  78 functions, bytecode registers, catcode tables and Lua callbacks.
  79 Previously these features have been provided by the contributed
  80 \package{luatex} (Heiko Oberdiek) and \package{luatexbase}
  81 (\'{E}lie Roux,
  82   Manuel P\'{e}gouri\'{e}-Gonnard and Philipp Gesang)
  83 packages. However, just as
  84 noted with the \package{etex} package in the previous release, it is
  85 better if allocation is handled by the format to avoid problems with
  86 conflicts between different allocation schemes, or definitions made
  87 before a package-defined allocation scheme is enabled.
  88
  89 The facilities incorporated into the format with this release, and
  90 described below, are closely modelled on the \package{luatexbase}
  91 package and we thank the authors, and especially \'{E}lie Roux, for
  92 help in arranging this transition.
  93
  94 The implementation of these \hologo{LuaTeX} features has been
  95 redesigned to match the allocation system introduced in the 2015/01/01
  96 \LaTeX\ release, and there are some other differences from the previous
  97 \package{luatexbase} package. However, as noted below,
  98 \package{luatexbase} is being updated in line with this \LaTeX\ release
  99 to provide the previous interface as a wrapper around the new
 100 implementation, so we expect the majority of documents using
 101 \package{luatexbase} to work without change.
 102
 103 \subsection{Names of \hologo{LuaTeX} primitive commands}
 104
 105 The 2015/01/01 \LaTeX\ release for the first time initialised
 106 \hologo{LuaTeX} in \textsf{latex.ltx} if \hologo{LuaTeX} is being
 107 used. Following the convention used in the contributed
 108 \textsf{lualatex.ini} file used to set up the format for earlier
 109 releases, most \hologo{LuaTeX}-specific primitives were defined with
 110 names prefixed by \texttt{luatex}. This was designed to minimize name
 111 clashes but had the disadvantage that names did not match the
 112 \hologo{LuaTeX} manual, or the names used in other formats, and
 113 produced some awkward command names such as \verb|\luatexluafunction|.
 114 From this release the names are enabled without the \texttt{luatex}
 115 prefix.
 116
 117 In practice this change should not affect many documents; relatively
 118 few packages access the primitive commands, and many of those are
 119 already set up to work with prefixed or unprefixed names, so that they
 120 work with multiple formats.
 121
 122 For package writers, if you want to ensure that your code works with
 123 this and earlier releases, use unprefixed names in the package and
 124 ensure that they are defined by using code such as:
 125 \begin{verbatim}
 126 \directlua{tex.enableprimitives("",
 127              tex.extraprimitives(
 128                "omega", "aleph", "luatex"))}
 129 \end{verbatim}
 130 Conversely if your document  uses a package relying on prefixed names
 131 then you can add:
 132 \begin{verbatim}
 133 \directlua{tex.enableprimitives("luatex",
 134              tex.extraprimitives(
 135                "omega", "aleph", "luatex"))}
 136 \end{verbatim}
 137 to your document.
 138
 139 Note the compatibility layer offered by the \package{luatexbase} package
 140 described below makes several commands available under both names.
 141
 142 As always, this change can be reverted using:\\
 143 \verb|\RequirePackage[2015/01/01]{latexrelease}|\\
 144 at the start of the document.
 145
 146
 147
 148 \subsection{\TeX\ commands for allocation in \hologo{LuaTeX}}
 149 For detailed descriptions of the new allocation commands see the
 150 documented sources in \textsf{ltluatex.dtx} or chapter N of
 151 \textsf{source2e}; however, the following new allocation commands are
 152 defined by default in \hologo{LuaTeX}:
 153 \verb|\newattribute|,
 154 \verb|\newcatcodetable|,
 155 \verb|\newluafunction| and
 156 \verb|\newwhatsit|.
 157 In addition, the commands \verb|\setattribute| and
 158 \verb|\unsetattribute| are defined to set and unset Lua attributes
 159 (integer values similar to counters, but attached to nodes). Finally
 160 several catcode tables are predefined:
 161 \verb|\catcodetable@initex|,
 162 \verb|\catcodetable@string|,
 163 \verb|\catcodetable@latex|,
 164 \verb|\catcodetable@atletter|.
 165
 166 \subsection{Predefined Lua functions}
 167 If used with \hologo{LuaTeX}, \LaTeX\ will initialise a Lua table,
 168 \textsf{luatexbase}, with functions supporting allocation and also
 169 the registering of Lua callback functions.
 170
 171 \subsection{Support for older releases and plain \TeX}
 172 The \hologo{LuaTeX} allocation functionality made available in this
 173 release is also available in plain \TeX\ and older \LaTeX\ releases
 174 in the files \textsf{ltluatex.tex} and \textsf{ltluatex.lua} which may be
 175 used simply by including the \TeX\ file: \verb|\input{ltluatex}|.
 176 An alternative for old \LaTeX\ releases is to use:\\
 177 \verb|\RequirePackage[2015/10/01]{latexrelease}|\\
 178 which will update the kernel to the current release, including
 179 \hologo{LuaTeX} support.
 180
 181 \subsection{Additional \hologo{LuaTeX} support packages}
 182 In addition to the base \LaTeX\ release two packages have been
 183 contributed to the \textsf{contrib} area on CTAN. The
 184 \package{ctablestack} package offers some commands to help package
 185 writers control the \hologo{LuaTeX} \textsf{catcodetable}
 186 functionality, and the \package{luatexbase} package replaces the
 187 previously available package of the same name, providing a compatible
 188 interface but implemented over the \package{ltluatex} code.
 189
 190 \section{More Floats and Inserts}
 191 If \hologo{eTeX} is available, the number of registers allocated in
 192 the format to hold floats such as figures is increased from 18 to 52.
 193
 194 The extended allocation system introduced in 2015/01/01 means that in
 195 most cases it is no longer necessary to load the \package{etex}
 196 package. Many classes and packages that previously loaded this package
 197 no longer do so. Unfortunately in some circumstances where a package
 198 or class previously used the \package{etex} \verb|\reserveinserts|
 199 command, it is possible for a document that previously worked to
 200 generate an error ``no room for a new insert''. In practice this error
 201 can always be avoided by declaring inserts earlier, before the
 202 registers below 256 are all allocated. However, it is better not
 203 to require packages to be re-ordered and in some cases the re-ordering
 204 is complicated due to delayed allocations in \verb|\AtBeginDocument|.
 205
 206 In this release, a new implementation of
 207 \verb|\newinsert| is used which allocates inserts from the previously
 208 allocated float lists once the classical register allocation has run
 209 out. This allows an extra 52 (or in \hologo{LuaTeX}, 64~thousand)
 210 insert allocations which is more than enough for practical documents
 211 (by default, \LaTeX\ only uses two insert allocations).
 212
 213 \section{Updated Unicode data}
 214
 215
 216 The file \textsf{unicode-letters.def} recording catcodes, upper and
 217 lower case mappings and other properties for Unicode characters has
 218 been regenerated using the data files from Unicode~8.0.0.
 219
 220 \section{Support for Comma Accent}
 221 The command \verb|\textcommabelow| has been added to the format.
 222 This is mainly used for the Romanian letters
 223 \textcommabelow{S}\textcommabelow{s}\textcommabelow{T}\textcommabelow{t}.
 224 This was requested in latex/4414 in the \LaTeX\ bug tracker.
 225
 226 \section{Extended \package{inputenc}}
 227 The \texttt{utf8} option for \package{inputenc} has been extended to support
 228 the letters s and t with comma accent,
 229 U+0218\,--\,U+021b. Similarly circumflex w and y U+0174\,--\,U+0177 are defined.
 230 Also U+00a0 and U+00ad are declared by default, and defined to be
 231 \verb|\nobreakspace| and \verb|\-| respectively.
 232
 233 The error message given on undefined UTF-8 input characters
 234 now displays the Unicode number
 235 in U+\textit{hex} format in addition
 236 to showing the character.
 237
 238 \section{Pre-release Releases}
 239 The patch level mechanism has been used previously to identify \LaTeX\
 240 releases that have small patches applied to the main release, without
 241 changing the main format date.
 242
 243 The mechanism has now been extended to allow identification of
 244 pre-release versions of the software (which may or may not be released
 245 via CTAN) but can be identified with a banner such as\\
 246 {\catcode`\<=13 \def<{\string<} \catcode`\>=13 \def>{\string>}%
 247 \verb|LaTeX2e <2015/10/01> pre-release-1|}\\
 248 Internally this is identified as a patch release with a negative patch
 249 level.
 250
 251 \section{Updates in tools}
 252
 253 The \package{multicol} package has been updated to fix the interaction
 254 with ``here'' floats that land on the same page as the start or end of
 255 a \textsf{multicols} environment.
 256
 257 \end{document}