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Diffstat (limited to 'doc/luaotfload-main.tex')
| -rw-r--r-- | doc/luaotfload-main.tex | 88 |
1 files changed, 55 insertions, 33 deletions
diff --git a/doc/luaotfload-main.tex b/doc/luaotfload-main.tex index fdca3c0..c418991 100644 --- a/doc/luaotfload-main.tex +++ b/doc/luaotfload-main.tex @@ -584,38 +584,6 @@ obviously, \inlinecode{random}. defaulting to \inlinecode{dflt}. \endaltitem - \beginaltitem {featurefile} - A comma-separated list of feature files to be applied to the - font. - % - Feature files contain a textual representation of - \OpenType tables and extend the features of a font - on fly. - % - After they are applied to a font, features defined in a - feature file can be enabled or disabled just like any - other font feature. - % - The syntax is documented in \identifier{Adobe}’s - \OpenType Feature File Specification.\footnote{% - Cf. \hyperlink {http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html}. - Feature file support is part of the engine which at the - time of this writing (2014) implements the spec only - partially. - See the - \hyperlink [\LUATEX tracker]{http://tracker.luatex.org/view.php?id=231} - for details. - } - - For a demonstration of how to set a \inlinecode{tkrn} feature consult - the file \inlinecode{tkrn.fea} that is part of \identifier{luaotfload}. - It can be read and applied as follows: - - \beginlisting - \font \test = Latin Modern Roman:featurefile=tkrn.fea;+tkrn - \endlisting - \endaltitem - \beginaltitem {color} A font color, defined as a triplet of two-digit hexadecimal \abbrev{rgb} values, with an optional fourth value for @@ -816,6 +784,8 @@ advance as well as a special \emphasis{request syntax}. Furthermore, this allows to define \emphasis{fallback fonts} to supplement fonts that may lack certain required glyphs. +\beginsubsection {Fallbacks} + For example, the \identifier{Latin Modern} family of fonts does, as indicated in the name, not provide Cyrillic glyphs. If Latin script dominates in the copy with interspersed Cyrillic, a fallback can be created from a similiar looking @@ -832,7 +802,59 @@ that it too derives from Knuth’s original \identifier{Computer Modern} series: \bye \endlisting -TODO +As simple as this may look on the first glance, this approach is entirely +inappropriate if more than a couple letters are required from a different font. +Because the combination pulls nothing except the glyph data, all of the +important other information that constitute a proper font -- kerning, styles, +features, and suchlike -- will be missing. + +\endsubsection %% Fallbacks + +\beginsubsection {Combinations} + +Generalizing the idea of a \emphasis{fallback font}, it is also possible to +pick definite sets of glyphs from multiple fonts. On a bad day, for instance, +it may be the sanest choice to start out with \identifier{EB Garamond} italics, +typeset all decimal digits in the bold italics of \identifier{GNU Freefont}, +and tone down the punctuation with extra thin glyphs from \identifier{Source +Sans}: + +\beginlisting + \def \feats {-tlig;-liga;mode=base;-kern} + \def \fileone {EBGaramond12-Italic.otf} + \def \filetwo {FreeMonoBoldOblique.otf} + \def \filethree {SourceSansPro-ExtraLight.otf} + + \input luaotfload.sty + + \font \one = file:\fileone :\feats + \font \two = file:\filetwo :\feats + \font \three = file:\filethree:\feats + + \font \onetwothree = "combo: 1 -> \fontid\one; + 2 -> \fontid\two, 0x30-0x39; + 3 -> \fontid\three, 0x21*0x3f; + + {\onetwothree \TeX—0123456789—?!} + \bye +\endlisting + +\noindent Despite the atrocious result, the example demonstrates well the +syntax that is used to specify ranges and fonts. Fonts are being referred to by +their internal index which can be obtained by passing the font command into the +\texmacro{fontid} macro, e. g. \inlinecode{\fontid\one}, after a font has been +defined. The first component of the combination is the base font which will be +extended by the others. It is specified by the index alone. + +All further fonts require either the literal \inlinecode{fallback} or a list of +codepoint definitions to be appended after a comma. The elements of this list +again denote either single codepoints like \inlinecode{0x21} (referring to the +exclamation point character) or ranges of codepoints (\inlinecode{0x30-0x39}). +Elements are separated by the \identifier{ASCII} asterisk character +(\inlinecode{*}). The characters referenced in the list will be imported from +the respective font, if available. + +\endsubsection %% Combinations \endsection |