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diff --git a/doc/luaotfload-main.tex b/doc/luaotfload-main.tex new file mode 100644 index 0000000..034b704 --- /dev/null +++ b/doc/luaotfload-main.tex @@ -0,0 +1,1591 @@ +%% Copyright (C) 2009-2014 +%% +%% by Elie Roux <elie.roux@telecom-bretagne.eu> +%% and Khaled Hosny <khaledhosny@eglug.org> +%% and Philipp Gesang <philipp.gesang@alumni.uni-heidelberg.de> +%% +%% This file is part of Luaotfload. +%% +%% Home: https://github.com/lualatex/luaotfload +%% Support: <lualatex-dev@tug.org>. +%% +%% Luaotfload is under the GPL v2.0 (exactly) license. +%% +%% ---------------------------------------------------------------------------- +%% +%% Luaotfload is free software; you can redistribute it and/or +%% modify it under the terms of the GNU General Public License +%% as published by the Free Software Foundation; version 2 +%% of the License. +%% +%% Luaotfload is distributed in the hope that it will be useful, +%% but WITHOUT ANY WARRANTY; without even the implied warranty of +%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +%% GNU General Public License for more details. +%% +%% You should have received a copy of the GNU General Public License +%% along with Luaotfload; if not, see <http://www.gnu.org/licenses/>. +%% +%% ---------------------------------------------------------------------------- +%% + +\beginfrontmatter + + \setdocumenttitle {The \identifier{luaotfload} package} + \setdocumentdate {2014/**/** v2.5} + \setdocumentauthor {Elie Roux · Khaled Hosny · Philipp Gesang\\ + Home: \hyperlink {https://github.com/lualatex/luaotfload}\\ + Support: \email {lualatex-dev@tug.org}} + + \typesetdocumenttitle + + \beginabstractcontent + This package is an adaptation of the \CONTEXT font loading system. + It allows for loading \OpenType fonts with an extended syntax and adds + support for a variety of font features. + \endabstractcontent + +\endfrontmatter + +\typesetcontent + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Introduction} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +Font management and installation has always been painful with \TEX. A +lot of files are needed for one font (\abbrev{tfm}, \abbrev{pfb}, +\abbrev{map}, \abbrev{fd}, \abbrev{vf}), and due to the 8-Bit encoding +each font is limited to 256 characters. + +But the font world has evolved since the original \TEX, and new +typographic systems have appeared, most notably the so called +\emphasis{smart font} technologies like \OpenType fonts (\abbrev{otf}). + +These fonts can contain many more characters than \TEX fonts, as well +as additional functionality like ligatures, old-style numbers, small +capitals, etc., and support more complex writing systems like Arabic +and Indic\footnote{% + Unfortunately, \identifier{luaotfload} doesn‘t support many Indic + scripts right now. + Assistance in implementing the prerequisites is greatly + appreciated. +} +scripts. + +\OpenType fonts are widely deployed and available for all modern +operating systems. + +As of 2013 they have become the de facto standard for advanced text +layout. + +However, until recently the only way to use them directly in the \TEX +world was with the \XETEX engine. + +Unlike \XETEX, \LUATEX has no built-in support for \OpenType or +technologies other than the original \TEX fonts. + +Instead, it provides hooks for executing \LUA code during the \TEX run +that allow implementing extensions for loading fonts and manipulating +how input text is processed without modifying the underlying engine. + +This is where \identifier{luaotfload} comes into play: +Based on code from \CONTEXT, it extends \LUATEX with functionality necessary +for handling \OpenType fonts. + +Additionally, it provides means for accessing fonts known to the operating +system conveniently by indexing the metadata. + +\endsection + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Thanks} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +\identifier{Luaotfload} is part of \LUALATEX, the community-driven +project to provide a foundation for using the \LATEX format with the +full capabilites of the \LUATEX engine. +% +As such, the distinction between end users, contributors, and project +maintainers is intentionally kept less strict, lest we unduly +personalize the common effort. + +Nevertheless, the current maintainers would like to express their +gratitude to Khaled Hosny, Akira Kakuto, Hironori Kitagawa and Dohyun +Kim. +% +Their contributions -- be it patches, advice, or systematic +testing -- made the switch from version 1.x to 2.2 possible. +% +Also, Hans Hagen, the author of the font loader, made porting the +code to \LATEX a breeze due to the extra effort he invested into +isolating it from the rest of \CONTEXT, not to mention his assistance +in the task and willingness to respond to our suggestions. + +\endsection + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Loading Fonts} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +\identifier{luaotfload} supports an extended font request syntax: + +\beginnarrower + \nonproportional{\string\font\string\foo\space= \string{}% + \meta{prefix}\nonproportional{:}% + \meta{font name}\nonproportional{:}% + \meta{font features}\nonproportional{\string}}% + \meta{\TEX font features} +\endnarrower + +\noindent +The curly brackets are optional and escape the spaces in the enclosed +font name. +% +Alternatively, double quotes serve the same purpose. +% +A selection of individual parts of the syntax are discussed below; +for a more formal description see figure \ref{font-syntax}. + +\beginsyntaxfloat + {font-syntax} + {Font request syntax. + Braces or double quotes around the + \emphasis{specification} rule will + preserve whitespace in file names. + In addition to the font style modifiers + (\emphasis{slash-notation}) given above, there + are others that are recognized but will be silently + ignored: \nonproportional{aat}, + \nonproportional{icu}, and + \nonproportional{gr}. + The special terminals are: + \smallcaps {feature\textunderscore id} for a valid font + feature name and + \smallcaps {feature\textunderscore value} for the corresponding + value. + \smallcaps {tfmname} is the name of a \abbrev{tfm} file. + \smallcaps {digit} again refers to bytes 48--57, and + \smallcaps {all\textunderscore characters} to all byte values. + \smallcaps {csname} and \smallcaps {dimension} are the \TEX concepts.} +% + <definition> ::= `\\font', {\sc csname}, `=', <font request>, [ <size> ] ; + + <size> ::= `at', {\sc dimension} ; + + <font request> ::= `"', <unquoted font request> `"' + \alt `{', <unquoted font request> `}' + \alt <unquoted font request> ; + + <unquoted font request> ::= <specification>, [`:', <feature list> ] + \alt `[', <path lookup> `]', [ [`:'], <feature list> ] ; + + <specification> ::= <prefixed spec>, [ <subfont no> ], \{ <modifier> \} + \alt <anon lookup>, \{ <modifier> \} ; + + <prefixed spec> ::= `file:', <file lookup> + \alt `name:', <name lookup> ; + + <file lookup> ::= \{ <name character> \} ; + + <name lookup> ::= \{ <name character> \} ; + + <anon lookup> ::= {\sc tfmname} | <name lookup> ; + + <path lookup> ::= \{ {\sc all_characters} - `]' \} ; + + <modifier> ::= `/', (`I' | `B' | `BI' | `IB' | `S=', \{ {\sc digit} \} ) ; + + <subfont no> ::= `(', \{ {\sc digit} \}, `)' ; + + <feature list> ::= <feature expr>, \{ `;', <feature expr> \} ; + + <feature expr> ::= {\sc feature_id}, `=', {\sc feature_value} + \alt <feature switch>, {\sc feature_id} ; + + <feature switch> ::= `+' | `-' ; + + <name character> ::= {\sc all_characters} - ( `(' | `/' | `:' ) ; +\endsyntaxfloat + +\beginsubsection{Prefix -- the \identifier{luaotfload}{ }Way} + +In \identifier{luaotfload}, the canonical syntax for font requests +requires a \emphasis{prefix}: +% +\beginnarrower + \nonproportional{\string\font\string\fontname\space= }% + \meta{prefix}% + \nonproportional{:}% + \meta{fontname}% + \dots +\endnarrower +% +where \meta{prefix} is either \inlinecode{file:} or \inlinecode {name:}.\footnote{% + The development version also knows two further prefixes, + \inlinecode {kpse:} and \inlinecode {my:}. + % + A \inlinecode {kpse} lookup is restricted to files that can be found by + \identifier{kpathsea} and + will not attempt to locate system fonts. + % + This behavior can be of value when an extra degree of encapsulation is + needed, for instance when supplying a customized tex distribution. + + The \inlinecode {my} lookup takes this a step further: it lets you define + a custom resolver function and hook it into the \luafunction{resolve_font} + callback. + % + This ensures full control over how a file is located. + % + For a working example see the + \hyperlink [test repo]{https://bitbucket.org/phg/lua-la-tex-tests/src/5f6a535d/pln-lookup-callback-1.tex}. +} +% +It determines whether the font loader should interpret the request as +a \emphasis{file name} or + \emphasis{font name}, respectively, +which again influences how it will attempt to locate the font. +% +Examples for font names are + “Latin Modern Italic”, + “GFS Bodoni Rg”, and + “PT Serif Caption” +-- they are the human readable identifiers +usually listed in drop-down menus and the like.\footnote{% + Font names may appear like a great choice at first because they + offer seemingly more intuitive identifiers in comparison to arguably + cryptic file names: + % + “PT Sans Bold” is a lot more descriptive than \fileent{PTS75F.ttf}. + On the other hand, font names are quite arbitrary and there is no + universal method to determine their meaning. + % + While \identifier{luaotfload} provides fairly sophisticated heuristic + to figure out a matching font style, weight, and optical size, it + cannot be relied upon to work satisfactorily for all font files. + % + For an in-depth analysis of the situation and how broken font names + are, please refer to + \hyperlink [this post]{http://www.ntg.nl/pipermail/ntg-context/2013/073889.html} + by Hans Hagen, the author of the font loader. + % + If in doubt, use filenames. + % + \fileent{luaotfload-tool} can perform the matching for you with the + option \inlinecode {--find=<name>}, and you can use the file name it returns + in your font definition. +} +% +In order for fonts installed both in system locations and in your +\fileent{texmf} to be accessible by font name, \identifier{luaotfload} must +first collect the metadata included in the files. +% +Please refer to section~\ref{sec:fontdb} below for instructions on how to +create the database. + +File names are whatever your file system allows them to be, except +that that they may not contain the characters + \inlinecode {(}, + \inlinecode {:}, and + \inlinecode {/}. +% +As is obvious from the last exception, the \inlinecode {file:} lookup will +not process paths to the font location -- only those +files found when generating the database are addressable this way. +% +Continue below in the \XETEX section if you need to load your fonts +by path. +% +The file names corresponding to the example font names above are + \fileent{lmroman12-italic.otf}, + \fileent{GFSBodoni.otf}, and + \fileent{PTZ56F.ttf}. + +\endsubsection + +\beginsubsection {Compatibility Layer} + +In addition to the regular prefixed requests, \identifier{luaotfload} +accepts loading fonts the \XETEX way. +% +There are again two modes: bracketed and unbracketed. +A bracketed request looks as follows. + +\beginnarrower + \nonproportional{\string\font\string\fontname\space = [}% + \meta{/path/to/file}% + \nonproportional{]} +\endnarrower + +\noindent +Inside the square brackets, every character except for a closing +bracket is permitted, allowing for specifying paths to a font file. +% +Naturally, path-less file names are equally valid and processed the +same way as an ordinary \inlinecode {file:} lookup. + +\beginnarrower + \nonproportional{\string\font\string\fontname\space= }% + \meta{font name} + \dots +\endnarrower + +Unbracketed (or, for lack of a better word: \emphasis{anonymous}) +font requests resemble the conventional \TEX syntax. +% +However, they have a broader spectrum of possible interpretations: +before anything else, \identifier{luaotfload} attempts to load a +traditional \TEX Font Metric (\abbrev{tfm} or \abbrev{ofm}). +% +If this fails, it performs a \inlinecode {name:} lookup, which itself will +fall back to a \inlinecode {file:} lookup if no database entry matches +\meta{font name}. + +Furthermore, \identifier{luaotfload} supports the slashed (shorthand) +font style notation from \XETEX. + +\beginnarrower + \nonproportional{\string\font\string\fontname\space= }% + \meta{font name}% + \nonproportional{/}% + \meta{modifier} + \dots +\endnarrower + +\noindent +Currently, four style modifiers are supported: + \inlinecode {I} for italic shape, + \inlinecode {B} for bold weight, + \inlinecode {BI} or \inlinecode {IB} for the combination of both. +% +Other “slashed” modifiers are too specific to the \XETEX engine and +have no meaning in \LUATEX. + +\endsubsection + +\beginsubsection{Examples} + +\beginsubsubsection{Loading by File Name} + +For example, conventional \abbrev{type1} font can be loaded with a +\inlinecode {file:} request like so: + +\beginlisting + \font \lmromanten = {file:ec-lmr10} at 10pt +\endlisting + +The \OpenType version of Janusz Nowacki’s font \emphasis{Antykwa +Półtawskiego}\footnote{% + \hyperlink {http://jmn.pl/antykwa-poltawskiego/}, also available in + in \TEX Live. +} +in its condensed variant can be loaded as follows: + +\beginlisting + \font \apcregular = file:antpoltltcond-regular.otf at 42pt +\endlisting + +The next example shows how to load the \emphasis{Porson} font digitized by +the Greek Font Society using \XETEX-style syntax and an absolute path from a +non-standard directory: + +\beginlisting + \font \gfsporson = "[/tmp/GFSPorson.otf]" at 12pt +\endlisting + +\endsubsubsection + +\beginsubsubsection{Loading by Font Name} + +The \inlinecode {name:} lookup does not depend on cryptic filenames: + +\beginlisting + \font \pagellaregular = {name:TeX Gyre Pagella} at 9pt +\endlisting + +A bit more specific but essentially the same lookup would be: + +\beginlisting + \font \pagellaregular = {name:TeX Gyre Pagella Regular} at 9pt +\endlisting + +\noindent +Which fits nicely with the whole set: + +\beginlisting + \font\pagellaregular = {name:TeX Gyre Pagella Regular} at 9pt + \font\pagellaitalic = {name:TeX Gyre Pagella Italic} at 9pt + \font\pagellabold = {name:TeX Gyre Pagella Bold} at 9pt + \font\pagellabolditalic = {name:TeX Gyre Pagella Bolditalic} at 9pt + + {\pagellaregular foo bar baz\endgraf} + {\pagellaitalic foo bar baz\endgraf} + {\pagellabold foo bar baz\endgraf} + {\pagellabolditalic foo bar baz\endgraf} + + ... +\endlisting + +\endsubsubsection + +\beginsubsubsection{Modifiers} + +If the entire \emphasis{Iwona} family\footnote{% + \hyperlink {http://jmn.pl/kurier-i-iwona/}, + also in \TEX Live. +} +is installed in some location accessible by \identifier{luaotfload}, +the regular shape can be loaded as follows: + +\beginlisting + \font \iwona = Iwona at 20pt +\endlisting + +\noindent +To load the most common of the other styles, the slash notation can +be employed as shorthand: + +\beginlisting + \font \iwonaitalic = Iwona/I at 20pt + \font \iwonabold = Iwona/B at 20pt + \font \iwonabolditalic = Iwona/BI at 20pt +\endlisting + +\noindent +which is equivalent to these full names: + +\beginlisting + \font \iwonaitalic = "Iwona Italic" at 20pt + \font \iwonabold = "Iwona Bold" at 20pt + \font \iwonabolditalic = "Iwona BoldItalic" at 20pt +\endlisting + +\endsubsubsection +\endsubsection +\endsection + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Font features} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +\emphasis{Font features} are the second to last component in the +general scheme for font requests: + +\beginnarrower + \nonproportional{\string\font\string\foo\space= "}% + \meta{prefix}% + \nonproportional{:}% + \meta{font name}% + \nonproportional{:}% + \meta{font features}% + \meta{\TEX font features}% + \nonproportional{"} +\endnarrower + +\noindent +If style modifiers are present (\XETEX style), they must precede +\meta{font features}. + +The element \meta{font features} is a semicolon-separated list of feature +tags\footnote{% + Cf. \hyperlink {http://www.microsoft.com/typography/otspec/featurelist.htm}. +} +and font options. +% +Prepending a font feature with a \inlinecode{+} (plus sign) enables it, +whereas a \inlinecode{-} (minus) disables it. For instance, the request + +\beginlisting + \font \test = LatinModernRoman:+clig;-kern +\endlisting + +\noindent activates contextual ligatures (\inlinecode{clig}) and +disables kerning (\inlinecode{kern}). +% +Alternatively the options \inlinecode{true} or \inlinecode{false} can +be passed to the feature in a key/value expression. +% +The following request has the same meaning as the last one: + +\beginlisting + \font \test = LatinModernRoman:clig=true;kern=false +\endlisting + +\noindent +Furthermore, this second syntax is required should a font feature +accept other options besides a true/false switch. +% +For example, \emphasis{stylistic alternates} (\inlinecode{salt}) are +variants of given glyphs. +% +They can be selected either explicitly by supplying the variant +index (starting from one), or randomly by setting the value to, +obviously, \inlinecode{random}. + +%% TODO verify that this actually works with a font that supports +%% the salt/random feature!\fi +\beginlisting + \font \librmsaltfirst = LatinModernRoman:salt=1 +\endlisting + +\beginsubsection {Basic font features} + +\begindescriptions + + \beginaltitem {mode} + \identifier{luaotfload} has two \OpenType processing + \emphasis{modes}: + \identifier{base} and \identifier{node}. + + \identifier{base} mode works by mapping \OpenType + features to traditional \TEX ligature and kerning mechanisms. + % + Supporting only non-contextual substitutions and kerning + pairs, it is the slightly faster, albeit somewhat limited, variant. + % + \identifier{node} mode works by processing \TeX’s internal + node list directly at the \LUA end and supports + a wider range of \OpenType features. + % + The downside is that the intricate operations required for + \identifier{node} mode may slow down typesetting especially + with complex fonts and it does not work in math mode. + + By default \identifier{luaotfload} is in \identifier{node} + mode, and \identifier{base} mode has to be requested where needed, + e.~g. for math fonts. + \endaltitem + + \beginaltitem {script} \label{script-tag} + An \OpenType script tag;\footnote{% + See \hyperlink {http://www.microsoft.com/typography/otspec/scripttags.htm} + for a list of valid values. + % + For scripts derived from the Latin alphabet the value + \inlinecode{latn} is good choice. + } + the default value is \inlinecode{dlft}. + % + Some fonts, including very popular ones by foundries like Adobe, + do not assign features to the \inlinecode{dflt} script, in + which case the script needs to be set explicitly. + \endaltitem + + \beginaltitem {language} + An \OpenType language system identifier,\footnote{% + Cf. \hyperlink {http://www.microsoft.com/typography/otspec/languagetags.htm}. + } + 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: + + \inlinecode{\\font \\test = Latin Modern Roman:featurefile=tkrn.fea;+tkrn} + \endaltitem + + \beginaltitem {color} + A font color, defined as a triplet of two-digit hexadecimal + \abbrev{rgb} values, with an optional fourth value for + transparency + (where \inlinecode{00} is completely transparent and + \inlinecode{FF} is opaque). + + For example, in order to set text in semitransparent red: + + \beginlisting +\font \test = "Latin Modern Roman:color=FF0000BB" + \endlisting + \endaltitem + + \beginaltitem {kernfactor \& letterspace} + Define a font with letterspacing (tracking) enabled. + % + In \identifier{luaotfload}, letterspacing is implemented by + inserting additional kerning between glyphs. + + This approach is derived from and still quite similar to the + \emphasis{character kerning} (\texmacro{setcharacterkerning} / + \texmacro{definecharacterkerning} \& al.) functionality of + Context, see the file \fileent{typo-krn.lua} there. + % + The main difference is that \identifier{luaotfload} does not + use \LUATEX attributes to assign letterspacing to regions, + but defines virtual letterspaced versions of a font. + + The option \identifier{kernfactor} accepts a numeric value that + determines the letterspacing factor to be applied to the font + size. + % + E.~g. a kern factor of $0.42$ applied to a $10$ pt font + results in $4.2$ pt of additional kerning applied to each + pair of glyphs. + % + Ligatures are split into their component glyphs unless + explicitly ignored (see below). + + For compatibility with \XETEX an alternative + \identifier{letterspace} option is supplied that interprets the + supplied value as a \emphasis{percentage} of the font size but + is otherwise identical to \identifier{kernfactor}. + % + Consequently, both definitions in below snippet yield the same + letterspacing width: + + \beginlisting +\font \iwonakernedA = "file:Iwona-Regular.otf:kernfactor=0.125" +\font \iwonakernedB = "file:Iwona-Regular.otf:letterspace=12.5" + \endlisting + + Specific pairs of letters and ligatures may be exempt from + letterspacing by defining the \LUA functions + \luafunction{keeptogether} and \luafunction{keepligature}, + respectively, inside the namespace \inlinecode {luaotfload.letterspace}. + % + Both functions are called whenever the letterspacing callback + encounters an appropriate node or set of nodes. + % + If they return a true-ish value, no extra kern is inserted at + the current position. + % + \luafunction{keeptogether} receives a pair of consecutive + glyph nodes in order of their appearance in the node list. + % + \luafunction{keepligature} receives a single node which can be + analyzed into components. + % + (For details refer to the \emphasis{glyph nodes} section in the + \LUATEX reference manual.) + % + The implementation of both functions is left entirely to the + user. + \endaltitem + +\ifcontextmkiv + \startbuffer [printvectors] + \directlua{inspect(fonts.protrusions.setups.default) + inspect(fonts.expansions.setups.default)} + \stopbuffer +\fi + + \beginaltitem {protrusion \& expansion} + These keys control microtypographic features of the font, + namely \emphasis{character protrusion} and \emphasis{font + expansion}. + % + Their arguments are names of \LUA tables that contain + values for the respective features.\footnote{% + For examples of the table layout please refer to the + section of the file \fileent{luaotfload-fonts-ext.lua} where the + default values are defined. + % + Alternatively and with loss of information, you can dump + those tables into your terminal by issuing + \unless \ifcontextmkiv + \beginlisting + \directlua{inspect(fonts.protrusions.setups.default) + inspect(fonts.expansions.setups.default)} + \endlisting + \else + \typebuffer [printvectors] + \fi + at some point after loading \fileent{luaotfload.sty}. + } + % + For both, only the set \identifier{default} is predefined. + + For example, to define a font with the default + protrusion vector applied\footnote{% + You also need to set + \inlinecode {pdfprotrudechars=2} and + \inlinecode {pdfadjustspacing=2} + to activate protrusion and expansion, respectively. + See the + \hyperlink [\PDFTEX manual]{http://mirrors.ctan.org/systems/pdftex/manual/pdftex-a.pdf}% + for details. + }: + + \beginlisting +\font \test = LatinModernRoman:protrusion=default + \endlisting + \endaltitem +\enddescriptions + +\endsubsection + +\beginsubsection {Non-standard font features} +\identifier{luaotfload} adds a number of features that are not defined +in the original \OpenType specification, most of them +aiming at emulating the behavior familiar from other \TEX engines. +% +Currently (2014) there are three of them: + +\begindescriptions + + \beginaltitem {anum} + Substitutes the glyphs in the \abbrev{ascii} number range + with their counterparts from eastern Arabic or Persian, + depending on the value of \identifier{language}. + \endaltitem + + \beginaltitem {tlig} + Applies legacy \TEX ligatures\footnote{% + These contain the feature set \inlinecode {trep} of earlier + versions of \identifier{luaotfload}. + + Note to \XETEX users: this is the equivalent of the + assignment \inlinecode {mapping=text-tex} using \XETEX's input + remapping feature. + }: + + \unless \ifcontextmkiv + %% Using braced arg syntax with inline code appears to be + %% impossible within Latex tables -- just ignore the weird + %% exclamation points below. + \begintabulate [rlrl] + \beginrow `` \newcell {\inlinecode !``! } \newcell '' \newcell {\inlinecode !''!} \endrow + \beginrow ` \newcell {\inlinecode !`! } \newcell ' \newcell {\inlinecode !'! } \endrow + \beginrow " \newcell {\inlinecode !"! } \newcell -- \newcell {\inlinecode !--!} \endrow + \beginrow --- \newcell {\inlinecode !---!} \newcell !` \newcell {\inlinecode ?!`?} \endrow + \beginrow ?` \newcell {\inlinecode !?`! } \newcell \newcell \endrow + \endtabulate + \else + %% XXX find a way to wrap these in the tabulate environment + \startframed [frame=off,width=broad,align=middle] + \startframed [frame=off,width=\dimexpr(\textwidth/2)] + \startxtable [align=middle] + \startxrow \startxcell `` \stopxcell \startxcell \inlinecode {``} \stopxcell \startxcell '' \stopxcell \startxcell \inlinecode {''} \stopxcell \stopxrow + \startxrow \startxcell ` \stopxcell \startxcell \inlinecode {`} \stopxcell \startxcell ' \stopxcell \startxcell \inlinecode {'} \stopxcell \stopxrow + \startxrow \startxcell " \stopxcell \startxcell \inlinecode {"} \stopxcell \startxcell -- \stopxcell \startxcell \inlinecode {--} \stopxcell \stopxrow + \startxrow \startxcell --- \stopxcell \startxcell \inlinecode {---} \stopxcell \startxcell !` \stopxcell \startxcell \inlinecode {!`} \stopxcell \stopxrow + \startxrow \startxcell ?` \stopxcell \startxcell \inlinecode {?`} \stopxcell \startxcell \stopxcell \startxcell \stopxcell \stopxrow + \stopxtable + \stopframed + \stopframed + \fi + \endaltitem + + \beginaltitem {itlc} + Computes italic correction values (active by default). + \endaltitem + +\enddescriptions + +\endsubsection +\endsection + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Font names database} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +\label{sec:fontdb} + +As mentioned above, \identifier{luaotfload} keeps track of which +fonts are available to \LUATEX by means of a \emphasis{database}. +% +This allows referring to fonts not only by explicit filenames but +also by the proper names contained in the metadata which is often +more accessible to humans.\footnote{% + The tool \hyperlink[\fileent{otfinfo}]{http://www.lcdf.org/type/} + (comes with \TEX Live), when invoked on a font file with the + \inlinecode {-i} option, lists the variety of name fields defined for + it. +} + +When \identifier{luaotfload} is asked to load a font by a font name, +it will check if the database exists and load it, or else generate a +fresh one. +% +Should it then fail to locate the font, an update to the database is +performed in case the font has been added to the system only +recently. +% +As soon as the database is updated, the resolver will try +and look up the font again, all without user intervention. +% +The goal is for \identifier{luaotfload} to act in the background and +behave as unobtrusively as possible, while providing a convenient +interface to the fonts installed on the system. + +Generating the database for the first time may take a while since it +inspects every font file on your computer. +% +This is particularly noticeable if it occurs during a typesetting run. +In any case, subsequent updates to the database will be quite fast. + +\beginsubsection[luaotfload-tool] + {\fileent{luaotfload-tool}} + +It can still be desirable at times to do some of these steps +manually, and without having to compile a document. +% +To this end, \identifier{luaotfload} comes with the utility +\fileent{luaotfload-tool} that offers an interface to the database +functionality. +% +Being a \LUA script, there are two ways to run it: +either make it executable (\inlinecode {chmod +x} on unixoid systems) or +pass it as an argument to \fileent{texlua}.\footnote{% + Tests by the maintainer show only marginal performance gain by + running with Luigi Scarso’s + \hyperlink [\identifier{Luajit\kern-.25ex\TEX}]{https://foundry.supelec.fr/projects/luajittex/}, + which is probably due to the fact that most of the time is spent + on file system operations. + + \emphasis{Note}: + On \abbrev{MS} \identifier{Windows} systems, the script can be run + either by calling the wrapper application + \fileent{luaotfload-tool.exe} or as + \inlinecode {texlua.exe luaotfload-tool.lua}. +} +% +Invoked with the argument \inlinecode {--update} it will perform a database +update, scanning for fonts not indexed. + +\beginlisting + luaotfload-tool --update +\endlisting + +Adding the \inlinecode {--force} switch will initiate a complete +rebuild of the database. + +\beginlisting + luaotfload-tool --update --force +\endlisting + +\endsubsection + +\beginsubsection{Search Paths} + +\identifier{luaotfload} scans those directories where fonts are +expected to be located on a given system. +% +On a Linux machine it follows the paths listed in the +\identifier{Fontconfig} configuration files; +consult \inlinecode {man 5 fonts.conf} for further information. +% +On \identifier{Windows} systems, the standard location is +\inlinecode {Windows\\Fonts}, +% +while \identifier{Mac OS~X} requires a multitude of paths to +be examined. +% +The complete list is is given in table \ref{table-searchpaths}. +Other paths can be specified by setting the environment variable +\inlinecode {OSFONTDIR}. +% +If it is non-empty, then search will be extended to the included +directories. + +\tablefloat {table-searchpaths} + {List of paths searched for each supported operating system.} + {% + \unless \ifcontextmkiv + \begincentered + \begintabulate [lp{.5\textwidth}] + \beginrow + Windows \newcell \inlinecode !\% WINDIR\%\\ Fonts! + \endrow + \beginrow + Linux \newcell \fileent{/usr/local/etc/fonts/fonts.conf} and\hfill\break + \fileent{/etc/fonts/fonts.conf} + \endrow + \beginrow + Mac \newcell \fileent{\textasciitilde/Library/Fonts},\break + \fileent{/Library/Fonts},\break + \fileent{/System/Library/Fonts}, and\hfill\break + \fileent{/Network/Library/Fonts} + \endrow + \endtabulate + \endcentered + \else + \setuplocalinterlinespace [14pt] + \starttabulate [|l|p(.5\textwidth)|] + \NC Windows \NC \inlinecode {\% WINDIR\%\\ Fonts} \NC \NR + \NC Linux \NC \fileent{/usr/local/etc/fonts/fonts.conf} and\crlf + \fileent{/etc/fonts/fonts.conf} \NC \NR + \NC + Mac \NC \fileent{\textasciitilde/Library/Fonts},\crlf + \fileent{/Library/Fonts},\break + \fileent{/System/Library/Fonts}, and\crlf + \fileent{/Network/Library/Fonts} \NC \NR + \stoptabulate + \fi% + } + +\endsubsection + +\beginsubsection{Querying from Outside} + +\fileent{luaotfload-tool} also provides rudimentary means of +accessing the information collected in the font database. +% +If the option \inlinecode {--find=}\emphasis{name} is given, the script will +try and search the fonts indexed by \identifier{luaotfload} for a +matching name. +% +For instance, the invocation + +\beginlisting + luaotfload-tool --find="Iwona Regular" +\endlisting + +\noindent +will verify if “Iwona Regular” is found in the database and can be +readily requested in a document. + +If you are unsure about the actual font name, then add the +\inlinecode {-F} (or \inlinecode {--fuzzy}) switch to the command line to enable +approximate matching. +% +Suppose you cannot precisely remember if the variant of +\identifier{Iwona} you are looking for was “Bright” or “Light”. +The query + +\beginlisting + luaotfload-tool -F --find="Iwona Bright" +\endlisting + +\noindent +will tell you that indeed the latter name is correct. + +Basic information about fonts in the database can be displayed +using the \inlinecode {-i} option (\inlinecode {--info}). +% +\beginlisting + luaotfload-tool -i --find="Iwona Light Italic" +\endlisting +% +\noindent +The meaning of the printed values is described in section 4.4 of the +\LUATEX reference manual.\footnote{% + In \TEX Live: \fileent{texmf-dist/doc/luatex/base/luatexref-t.pdf}. +} + +For a much more detailed report about a given font try the +\inlinecode {-I} option instead (\inlinecode {--inspect}). +\beginlisting + luaotfload-tool -I --find="Iwona Light Italic" +\endlisting + +\inlinecode {luaotfload-tool --help} will list the available command line +switches, including some not discussed in detail here. +% +For a full documentation of \identifier{luaotfload-tool} and its +capabilities refer to the manpage +(\inlinecode {man 1 luaotfload-tool}).\footnote{% + Or see \inlinecode {luaotfload-tool.rst} in the source directory. +} + +\endsubsection + +\beginsubsection {Blacklisting Fonts} +\label{font-blacklist} + +Some fonts are problematic in general, or just in \LUATEX. +% +If you find that compiling your document takes far too long or eats +away all your system’s memory, you can track down the culprit by +running \inlinecode {luaotfload-tool -v} to increase verbosity. +% +Take a note of the \emphasis{filename} of the font that database +creation fails with and append it to the file +\fileent{luaotfload-blacklist.cnf}. + +A blacklist file is a list of font filenames, one per line. +Specifying the full path to where the file is located is optional, the +plain filename should suffice. +% +File extensions (\fileent{.otf}, \fileent{.ttf}, etc.) may be omitted. +% +Anything after a percent (\inlinecode {\%}) character until the end of the line +is ignored, so use this to add comments. +% +Place this file to some location where the \identifier{kpse} +library can find it, e.~g. +\fileent{texmf-local/tex/luatex/luaotfload} if you are running +\identifier{\TEX Live},\footnote{% + You may have to run \inlinecode {mktexlsr} if you created a new file in + your \fileent{texmf} tree. +} +or just leave it in the working directory of your document. +% +\identifier{luaotfload} reads all files named +\fileent{luaotfload-blacklist.cnf} it finds, so the fonts in +\fileent{./luaotfload-blacklist.cnf} extend the global blacklist. + +Furthermore, a filename prepended with a dash character (\inlinecode{-}) is +removed from the blacklist, causing it to be temporarily whitelisted +without modifying the global file. +% +An example with explicit paths: + +\beginlisting +% example otf-blacklist.cnf +/Library/Fonts/GillSans.ttc % Luaotfload ignores this font. +-/Library/Fonts/Optima.ttc % This one is usable again, even if + % blacklisted somewhere else. +\endlisting + +\endsubsection +\endsection + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Files from \CONTEXT and \LUATEX-Fonts} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +\identifier{luaotfload} relies on code originally written by Hans +Hagen for the \hyperlink[\identifier{\CONTEXT}]{http://wiki.contextgarden.net} +format. +% +It integrates the font loader as distributed in +the \identifier{\LUATEX-Fonts} package. +% +The original \LUA source files have been combined using the +\fileent{mtx-package} script into a single, self-contained blob. +In this form the font loader has no further dependencies\footnote{% + It covers, however, to some extent the functionality of the + \identifier{lualibs} package. +} +and requires only minor adaptions to integrate into +\identifier{luaotfload}. +% +The guiding principle is to let \CONTEXT/\LUATEX-Fonts take care of +the implementation, and update the imported code from time to time. +% +As maintainers, we aim at importing files from upstream essentially +\emphasis{unmodified}, except for renaming them to prevent name +clashes. +% +This job has been greatly alleviated since the advent of +\LUATEX-Fonts, prior to which the individual dependencies had to be +manually spotted and extracted from the \CONTEXT source code in a +complicated and error-prone fashion. + +Below is a commented list of the files distributed with +\identifier{luaotfload} in one way or the other. +% +See figure \ref{file-graph} on page \pageref{file-graph} for a +graphical representation of the dependencies. +% +From \LUATEX-Fonts, only the file \fileent{luatex-fonts-merged.lua} +has been imported as \fileent{luaotfload-fontloader.lua}. +% +It is generated by \fileent{mtx-package}, a \LUA source code merging +too developed by Hans Hagen.\footnote{% + \fileent{mtx-package} is + \hyperlink [part of \CONTEXT]{http://repo.or.cz/w/context.git/blob_plain/refs/heads/origin:/scripts/context/lua/mtx-package.lua} + and requires \fileent{mtxrun}. + Run + \inlinecode {mtxrun --script package --help} + to display further information. + For the actual merging code see the file + \fileent{util-mrg.lua} that is part of \CONTEXT. +} +It houses several \LUA files that can be classed in three +categories. + +\begindefinitions + \beginnormalitem + \emphasis{\LUA utility libraries}, a subset + of what is provided by the \identifier{lualibs} + package. + + \begindoublecolumns + \begindefinitions + \beginaltitem {l-lua.lua} \endaltitem + \beginaltitem {l-lpeg.lua} \endaltitem + \beginaltitem {l-function.lua} \endaltitem + \beginaltitem {l-string.lua} \endaltitem + \beginaltitem {l-table.lua} \endaltitem + \beginaltitem {l-io.lua} \endaltitem + \beginaltitem {l-file.lua} \endaltitem + \beginaltitem {l-boolean.lua} \endaltitem + \beginaltitem {l-math.lua} \endaltitem + \beginaltitem {util-str.lua} \endaltitem + \enddefinitions + \enddoublecolumns + \endnormalitem + + \beginnormalitem + The \emphasis{font loader} itself. + These files have been written for + \LUATEX-Fonts and they are distributed along + with \identifier{luaotfload}. + \begindoublecolumns + \begindefinitions + \beginaltitem{luatex-basics-gen.lua} \endaltitem + \beginaltitem{luatex-basics-nod.lua} \endaltitem + \beginaltitem{luatex-fonts-enc.lua} \endaltitem + \beginaltitem{luatex-fonts-syn.lua} \endaltitem + \beginaltitem{luatex-fonts-tfm.lua} \endaltitem + \beginaltitem{luatex-fonts-chr.lua} \endaltitem + \beginaltitem{luatex-fonts-lua.lua} \endaltitem + \beginaltitem{luatex-fonts-inj.lua} \endaltitem + \beginaltitem{luatex-fonts-otn.lua} \endaltitem + \beginaltitem{luatex-fonts-def.lua} \endaltitem + \beginaltitem{luatex-fonts-ext.lua} \endaltitem + \beginaltitem{luatex-fonts-cbk.lua} \endaltitem + \enddefinitions + \enddoublecolumns + \endnormalitem + + \beginnormalitem + Code related to \emphasis{font handling and + node processing}, taken directly from + \CONTEXT. + \begindoublecolumns + \begindefinitions + \beginaltitem{data-con.lua} \endaltitem + \beginaltitem{font-ini.lua} \endaltitem + \beginaltitem{font-con.lua} \endaltitem + \beginaltitem{font-cid.lua} \endaltitem + \beginaltitem{font-map.lua} \endaltitem + \beginaltitem{font-oti.lua} \endaltitem + \beginaltitem{font-otf.lua} \endaltitem + \beginaltitem{font-otb.lua} \endaltitem + \beginaltitem{font-ota.lua} \endaltitem + \beginaltitem{font-def.lua} \endaltitem + \beginaltitem{font-otp.lua} \endaltitem + \enddefinitions + \enddoublecolumns + \endnormalitem +\enddefinitions + +Note that if \identifier{luaotfload} cannot locate the +merged file, it will load the individual \LUA libraries +instead. +% +Their names remain the same as in \CONTEXT (without the +\inlinecode {otfl}-prefix) since we imported the relevant section of +\fileent{luatex-fonts.lua} unmodified into \fileent{luaotfload-main.lua}. +Thus if you prefer running bleeding edge code from the +\CONTEXT beta, all you have to do is remove +\fileent{luaotfload-merged.lua} from the search path. + +Also, the merged file at some point loads the Adobe Glyph List from a +\LUA table that is contained in \fileent{luaotfload-glyphlist.lua}, +which is automatically generated by the script +\fileent{mkglyphlist}.\footnote{% + See \fileent{luaotfload-font-enc.lua}. + The hard-coded file name is why we have to replace the procedure + that loads the file in \fileent{luaotfload-override.lua}. +} +There is a make target \identifier{glyphs} that will create a fresh +glyph list so we don’t need to import it from \CONTEXT any longer. + +In addition to these, \identifier{luaotfload} requires a number of +files not contained in the merge. Some of these have no equivalent in +\LUATEX-Fonts or \CONTEXT, some were taken unmodified from the latter. + + +\beginfilelist + \beginaltitem {luaotfload-features.lua} + font feature handling; incorporates some of the code from + \fileent{font-otc} from \CONTEXT; + \endaltitem + \beginaltitem {luaotfload-override.lua} + overrides the \CONTEXT logging functionality. + \endaltitem + \beginaltitem {luaotfload-loaders.lua} + registers the \OpenType font reader as handler for Postscript + fonts (\abbrev{pfa}, \abbrev{pfb}). + \endaltitem + \beginaltitem {luaotfload-parsers.lua} + various \abbrev{lpeg}-based parsers. + \endaltitem + \beginaltitem {luaotfload-database.lua} + font names database. + \endaltitem + \beginaltitem {luaotfload-colors.lua} + color handling. + \endaltitem + \beginaltitem {luaotfload-auxiliary.lua} + access to internal functionality for package authors (proposals + for additions welcome). + \endaltitem + \beginaltitem {luaotfload-letterspace.lua} + font-based letterspacing. + \endaltitem +\endfilelist + +\figurefloat + {file-graph} + {Schematic of the files in \identifier{Luaotfload}} + {filegraph.pdf} + +\endsection + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Auxiliary Functions} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +With release version 2.2, \identifier{luaotfload} received +additional functions for package authors to call from outside +(see the file \fileent{luaotfload-auxiliary.lua} for details). +% +The purpose of this addition twofold. +% +Firstly, \identifier{luaotfload} failed to provide a stable interface +to internals in the past which resulted in an unmanageable situation +of different packages abusing the raw access to font objects by means +of the \luafunction{patch_font} callback. +% +When the structure of the font object changed due to an update, all +of these imploded and several packages had to be fixed while +simultaneously providing fallbacks for earlier versions. +% +Now the patching is done on the \identifier{luaotfload} side and can +be adapted with future modifications to font objects without touching +the packages that depend on it. +% +Second, some the capabilities of the font loader and the names +database are not immediately relevant in \identifier{luaotfload} +itself but might nevertheless be of great value to package authors or +end users. + +Note that the current interface is not yet set in stone and the +development team is open to suggestions for improvements or +additions. + +\beginsubsection {Callback Functions} + +The \luafunction{patch_font} callback is inserted in the wrapper +\identifier{luaotfload} provides for the font definition callback +(see below, page \pageref{define-font}). +% +At this place it allows manipulating the font object immediately after +the font loader is done creating it. +% +For a short demonstration of its usefulness, here is a snippet that +writes an entire font object to the file \fileent{fontdump.lua}: + +\beginlisting + \input luaotfload.sty + \directlua{ + local dumpfile = "fontdump.lua" + local dump_font = function (tfmdata) + local data = table.serialize(tfmdata) + io.savedata(dumpfile, data) + end + + luatexbase.add_to_callback( + "luaotfload.patch_font", + dump_font, + "my_private_callbacks.dump_font" + ) + } + \font \dumpme = name:Iwona + \bye +\endlisting + +\emphasis{Beware}: this creates a Lua file of around 150,000 lines of +code, taking up 3~\abbrev{mb} of disk space. +% +By inspecting the output you can get a first impression of how a font +is structured in \LUATEX’s memory, what elements it is composed of, +and in what ways it can be rearranged. + +\beginsubsubsection {Compatibility with Earlier Versions} + +As has been touched on in the preface to this section, the structure +of the object as returned by the fontloader underwent rather drastic +changes during different stages of its development, and not all +packages that made use of font patching have kept up with every one +of it. +% +To ensure compatibility with these as well as older versions of +some packages, \identifier{luaotfload} sets up copies of or references +to data in the font table where it used to be located. +% +For instance, important parameters like the requested point size, the +units factor, and the font name have again been made accessible from +the toplevel of the table even though they were migrated to different +subtables in the meantime. + +\endsubsubsection + +\beginsubsubsection{Patches} + +These are mostly concerned with establishing compatibility with \XETEX. + +\beginfunctionlist + + \beginaltitem {set_sscale_dimens} + Calculate \texmacro{fontdimen}s 10 and 11 to emulate \XETEX. + \endaltitem + + \beginaltitem {set_capheight} + Calculates \texmacro{fontdimen} 8 like \XETEX. + \endaltitem + + \beginaltitem {patch_cambria_domh} + Correct some values of the font \emphasis{Cambria Math}. + \endaltitem + +\endfunctionlist + +\endsubsection + +\beginsubsection {Package Author’s Interface} + +As \LUATEX release 1.0 is nearing, the demand for a reliable interface +for package authors increases. + +\endsubsubsection + +\beginsubsubsection{Font Properties} + +Below functions mostly concern querying the different components of a +font like for instance the glyphs it contains, or what font features +are defined for which scripts. + +\beginfunctionlist + + \beginaltitem {aux.font_has_glyph (id : int, index : int)} + Predicate that returns true if the font \luafunction{id} + has glyph \luafunction{index}. + \endaltitem + + \beginaltitem {aux.slot_of_name(name : string)} + Translates an Adobe Glyph name to the corresponding glyph + slot. + \endaltitem + + \beginaltitem {aux.name_of_slot(slot : int)} + The inverse of \luafunction{slot_of_name}; note that this + might be incomplete as multiple glyph names may map to the + same codepoint, only one of which is returned by + \luafunction{name_of_slot}. + \endaltitem + + \beginaltitem {aux.provides_script(id : int, script : string)} + Test if a font supports \luafunction{script}. + \endaltitem + + \beginaltitem {aux.provides_language(id : int, script : string, language : string)} + Test if a font defines \luafunction{language} for a given + \luafunction{script}. + \endaltitem + + \beginaltitem {aux.provides_feature(id : int, script : string, + language : string, feature : string)} + Test if a font defines \luafunction{feature} for + \luafunction{language} for a given \luafunction{script}. + \endaltitem + + \beginaltitem {aux.get_math_dimension(id : int, dimension : string)} + Get the dimension \luafunction{dimension} of font \luafunction{id}. + \endaltitem + + \beginaltitem {aux.sprint_math_dimension(id : int, dimension : string)} + Same as \luafunction{get_math_dimension()}, but output the value + in scaled points at the \TEX end. + \endaltitem + +\endfunctionlist + +\endsubsubsection + +\beginsubsubsection{Database} + +%% not implemented, may come back later +\beginfunctionlist +% \beginaltitem {aux.scan_external_dir(dir : string)} +% Include fonts in directory \luafunction{dir} in font lookups without +% adding them to the database. +% + \beginaltitem {aux.read_font_index (void)} + Read the index file from the appropriate location (usually + the bytecode file \fileent{luaotfload-names.luc} somewhere + in the \fileent{texmf-var} tree) and return the result as a + table. The file is processed with each call so it is up to + the user to store the result for later access. + \endaltitem + + \beginaltitem {aux.font_index (void)} + Return a reference of the font names table used internally + by \identifier{luaotfload}. The index will be read if it + has not been loaded up to this point. Also a font scan that + overwrites the current index file might be triggered. Since + the return value points to the actual index, any + modifications to the table might influence runtime behavior + of \identifier{luaotfload}. + \endaltitem + +\endfunctionlist + +\endsubsubsection + +\endsubsection +\endsection + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +\beginsection {Troubleshooting} +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + +\beginsubsection {Database Generation} + +If you encounter problems with some fonts, please first update to the +latest version of this package before reporting a bug, as +\identifier{luaotfload} is under active development and still a moving +target. +% +The development takes place on \identifier{github} at +\hyperlink {https://github.com/lualatex/luaotfload} where there is an issue +tracker for submitting bug reports, feature requests and the likes. + +Bug reports are more likely to be addressed if they contain the output +of + +\beginlisting + luaotfload-tool --diagnose=environment,files,permissions +\endlisting + +\noindent Consult the man page for a description of these options. + +Errors during database generation can be traced by increasing the +verbosity level and redirecting log output to \fileent{stdout}: + +\beginlisting + luaotfload-tool -fuvvv --log=stdout +\endlisting + +\noindent or to a file in \fileent{/tmp}: + +\beginlisting + luaotfload-tool -fuvvv --log=file +\endlisting + +\noindent In the latter case, invoke the \inlinecode {tail(1)} utility on the +file for live monitoring of the progress. + +If database generation fails, the font last printed to the terminal or +log file is likely to be the culprit. +% +Please specify it when reporting a bug, and blacklist it for the time +being (see above, page \pageref{font-blacklist}). + +\endsubsection + +\beginsubsection {Font Features} + +A common problem is the lack of features for some +\OpenType fonts even when specified. +% +This can be related to the fact that some fonts do not provide features +for the \inlinecode {dflt} script (see above on page \pageref{script-tag}), +which is the default one in this package. +% +If this happens, assigning a noth script when the font is defined should +fix it. +% +For example with \inlinecode {latn}: + +\beginlisting + \font \test = file:MyFont.otf:script=latn;+liga; +\endlisting + +You can get a list of features that a font defines for scripts and +languages by querying it in \fileent{luaotfload-tool}: + +\beginlisting + luaotfload-tool --find="Iwona" --inspect +\endlisting + +\endsubsection + +\beginsubsection {\LUATEX Programming} + +Another strategy that helps avoiding problems is to not access raw +\LUATEX internals directly. +% +Some of them, even though they are dangerous to access, have not been +overridden or disabled. +% +Thus, whenever possible prefer the functions in the \luafunction{aux} +namespace over direct manipulation of font objects. For example, raw +access to the \luafunction{font.fonts} table like: + +\beginlisting + local somefont = font.fonts[2] +\endlisting + +\noindent can render already defined fonts unusable. +% +Instead, the function \luafunction{font.getfont()} should be used +because it has been replaced by a safe variant. + +However, \luafunction{font.getfont()} only covers fonts handled by the +font loader, e.~g. \identifier{OpenType} and \identifier{TrueType} +fonts, but not \abbrev{tfm} or \abbrev{ofm}. +% +Should you absolutely require access to all fonts known to \LUATEX, +including the virtual and autogenerated ones, then you need to query +both \luafunction{font.getfont()} and \luafunction{font.fonts}. +% +In this case, best define you own accessor: + +\beginlisting + local unsafe_getfont = function (id) + local tfmdata = font.getfont (id) + if not tfmdata then + tfmdata = font.fonts[id] + end + return tfmdata + end + + --- use like getfont() + local somefont = unsafe_getfont (2) +\endlisting + +\endsubsection +\endsection + +\beginsection {License} + +\identifier {luaotfload} is licensed under the terms of the +\hyperlink [GNU General Public License version 2.0]% + {https://www.gnu.org/licenses/old-licenses/gpl-2.0.html}. +Following the underlying fontloader code \identifier {luaotfload} +recognizes only that exact version as its license. +The „any later version” clause of the original license text as +copyrighted by the \hyperlink [Free Software Foundation]{http://www.fsf.org/} +\emphasis {does not apply} to either \identifier {luaotfload} or the +code imported from \CONTEXT. + +The complete text of the license is given as a separate file \fileent +{COPYING} in the toplevel directory of the +\hyperlink [\fileent {Luaotfload} Git repository]{https://github.com/lualatex/luaotfload/blob/master/COPYING}. +Distributions probably package it as \fileent +{doc/luatex/luaotfload/COPYING} in the relevant \fileent {texmf} tree. + +\endsection + +\endinput + |