trunk/doc/ltnews27.tex

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  29 % Filename: ltnews27.tex
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  31 % This is issue 27 of LaTeX News.
  32
  33 \documentclass{ltnews}
  34 \usepackage[T1]{fontenc}
  35
  36 \usepackage{lmodern,url,hologo}
  37
  38 \publicationmonth{April}
  39 \publicationyear{2017}
  40
  41 \publicationissue{27}
  42
  43 \begin{document}
  44
  45 \maketitle
  46 \tableofcontents
  47
  48 \setlength\rightskip{0pt plus 3em}
  49
  50 \section{ISO 8601 Date Format}
  51 Since before the first releases of \LaTeXe, \LaTeX\ has used a date
  52 format in the form \textsc{yyyy/mm/dd}. This has many advantages over more
  53 conventional formats, as it is easy to sort and avoids the unfortunate
  54 ambiguity between different communities as to whether 01/02/2017 is the
  55 1st of February or 2nd of January.
  56
  57 However there is another date format, formalised by the
  58 International standard, ISO~8601. The basic format defined by this
  59 standard is functionally equivalent to the \LaTeX\ format, but using
  60 \texttt{-} rather than \texttt{/}. This date format is now supported
  61 in many Operating Systems and applications
  62 (for example the \verb|date --iso-8601| command in Linux and similar systems).
  63
  64 From this release, \LaTeX\ will accept ISO format date strings in the
  65 date argument of \verb|\ProvidesPackage|, \verb|\usepackage| etc.
  66 Currently we recommend that you do not use this format in any packages
  67 that need to work with older \LaTeX\ releases.
  68 The \textsf{latexrelease} package may be used with older releases to
  69  add this functionality. This change is handled in a special way  by
  70  \textsf{latexrelease}: The package always adds support for ISO dates
  71 whatever format date is requested, this is required so that the
  72 necessary date comparisons may be made.
  73
  74 The new functionality can be seen in the startup banner which
  75 advertises \texttt{LaTeX2e <2017-04-15>}.
  76
  77 \section{Further TU encoding improvements}
  78 The 2017/01/01 release saw the introduction of the new TU encoding for
  79 specifying Unicode fonts with \hologo{LuaTeX} and
  80 \hologo{XeTeX}. There were a number of small corrections and additions
  81 in the patch releases updating 2017/01/01, and a further addition in
  82 this release, notably extended support for the dot-under accent,
  83 \verb|\d|.
  84
  85
  86 \section{Disabling Hyphenation}
  87 The existing \LaTeX\ code for \verb|\verb| and \verb|verbatim| had some
  88 issues when used with fonts that were not loaded with hyphenation
  89 disabled via setting \verb|\hyphenchar| to $-1$. In this release these
  90 verbatim environments use a \verb|\language| setting,
  91 \verb|\l@nohyphenation|, that has no hyphenation patterns associated.
  92
  93 The format ensures that  a language has been allocated with this name.
  94 For most users this will in fact be no change as the standard
  95 \textsf{babel} language has for a long time allocated a language with
  96 this name.
  97
  98 In order that page breaks in \texttt{verbatim} do not influence the
  99 language used in the page head and foot, the format now normalises the
 100 language used in the output routine to a default language as described
 101 below.
 102
 103 \section{Discretionary Hyphenation}
 104 The \LaTeX\ definition of \verb|\-| has been adjusted so that it will
 105 insert the current font's \verb|\hyphenchar|, as would the
 106 \TeX-primitive definition. A comment in \textsf{source2e} has given
 107 this new definition since first releases of \LaTeXe, and in this
 108 release we finally acted upon this comment. Previously \verb|\-|
 109 always inserted a \texttt{-} at a break point even if a different
 110 character would be used for automatic hyphenation with the current font.
 111
 112 \section{Default Document Language}
 113
 114 A new integer parameter \verb|\document@default@language| is
 115 introduced, this is initialised to $-1$ but is set at
 116 \verb|\begin{document}| to the language in force at that time if it
 117   has not been set by preamble code. This is very similar to the
 118   handling of the default color.  and is used in a similar way to
 119   normalise the settings for page head and foot as described above.
 120 Users should not normally need to set this explicitly but it expected that
 121 language packages such as \textsf{babel} may set this if the default
 122 behaviour is not suitable.
 123
 124 \section{Line Spacing in parboxes}
 125 Inside a \verb|\parbox|
 126 \LaTeX\ normalises the baseline spacing. However it has not
 127 previously reset \verb|\lineskiplimit|. This meant that
 128 lines of a paragraph that have ascenders or descenders could be set
 129 with \emph{closer} line spacing than lines without. This can easily
 130 happen if you use a \verb|\parbox| in an AMS alignment, as they use a
 131 relativly large value of \verb|\lineskiplimit|.
 132 As usual, the \textsf{latexrelease} package may be used to
 133 force the older behavior.
 134
 135 \end{document}