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Diffstat (limited to 'doc/luaotfload-main.tex')
| -rw-r--r-- | doc/luaotfload-main.tex | 407 |
1 files changed, 205 insertions, 202 deletions
diff --git a/doc/luaotfload-main.tex b/doc/luaotfload-main.tex index c7a7297..7a5526a 100644 --- a/doc/luaotfload-main.tex +++ b/doc/luaotfload-main.tex @@ -144,6 +144,7 @@ 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 @@ -509,210 +510,212 @@ obviously, |random|. \font\librmsaltfirst=LatinModernRoman:salt=1 \endlisting -\noindent Other font options include: - -\begin{description} - -\item [mode] \hfill \\ - \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. - -\item [script] \label{script-tag} \hfill \\ - An \OpenType script tag;\footnote{% - See \hyperlink {http://www.microsoft.com/typography/otspec/scripttags.htm} - for a list of valid values. +\beginsubsection {Basic font features} + +\begindescriptions + + \altitem {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. + + \altitem {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 + |latn| is good choice. + } + the default value is |dlft|. + % + Some fonts, including very popular ones by foundries like Adobe, + do not assign features to the |dflt| script, in + which case the script needs to be set explicitly. + + \altitem {language} + An \OpenType language system identifier,\footnote{% + Cf. \hyperlink {http://www.microsoft.com/typography/otspec/languagetags.htm}. + } + defaulting to |dflt|. + + \altitem {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 |tkrn| feature consult + the file |tkrn.fea| that is part of \identifier{luaotfload}. + It can be read and applied as follows: + + |\font\test=Latin Modern Roman:featurefile=tkrn.fea;+tkrn| + + \altitem {color} + A font color, defined as a triplet of two-digit hexadecimal + \abbrev{rgb} values, with an optional fourth value for + transparency + (where |00| is completely transparent and |FF| is opaque). + + For example, in order to set text in semitransparent red: + + \beginlisting +\font\test={Latin Modern Roman}:color=FF0000BB + \endlisting + + \altitem {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}. % - For scripts derived from the Latin alphabet the value - |latn| is good choice. - } - the default value is |dlft|. - % - Some fonts, including very popular ones by foundries like Adobe, - do not assign features to the |dflt| script, in - which case the script needs to be set explicitly. - -\item [language] \hfill \\ - An \OpenType language system identifier,\footnote{% - Cf. \hyperlink {http://www.microsoft.com/typography/otspec/languagetags.htm}. - } - defaulting to |dflt|. - -\item [featurefile] \hfill \\ - 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 |tkrn| feature consult - the file |tkrn.fea| that is part of \identifier{luaotfload}. - It can be read and applied as follows: - - |\font\test=Latin Modern Roman:featurefile=tkrn.fea;+tkrn| - -\item [color] \hfill \\ - A font color, defined as a triplet of two-digit hexadecimal - \abbrev{rgb} values, with an optional fourth value for - transparency - (where |00| is completely transparent and |FF| is opaque). - - For example, in order to set text in semitransparent red: - - \beginlisting - \font\test={Latin Modern Roman}:color=FF0000BB - \endlisting - -\item [kernfactor \& letterspace] \hfill \\ - 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. - - -\item [protrusion \& expansion] \hfill \\ - 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 - \beginlisting - \directlua{inspect(fonts.protrusions.setups.default) - inspect(fonts.expansions.setups.default)} - \endlisting - 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 -\end{description} - -\paragraph{Non-standard font features} + 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. + + + \altitem {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 + \beginlisting +\directlua{inspect(fonts.protrusions.setups.default) + inspect(fonts.expansions.setups.default)} + \endlisting + 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 +\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: -\begin{description} +\begindescriptions - \item [anum] + \altitem {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}. - \item [tlig] + \altitem {tlig} Applies legacy \TEX ligatures: \begin{tabular}{rlrl} @@ -732,12 +735,12 @@ Currently (2014) there are three of them: remapping feature. } - \item [itlc] + \altitem {itlc} Computes italic correction values (active by default). -\end{description} - +\enddescriptions +\endsubsection \endsection %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% @@ -1138,11 +1141,11 @@ files not contained in the merge. Some of these have no equivalent in \altitem {luaotfload-letterspace.lua} font-based letterspacing. \endfilelist -\begin{figure}[b] - \caption{Schematic of the files in \identifier{Luaotfload}} +\beginfigurefloat + {file-graph} + {Schematic of the files in \identifier{Luaotfload}} \includegraphics[width=\textwidth]{filegraph.pdf} - \label{file-graph} -\end{figure} +\endfigurefloat \endsection @@ -1308,14 +1311,14 @@ are defined for which scripts. %% not implemented, may come back later % \beginsubsubsection{Database} -% +% % \beginfunctionlist % \altitem {aux.scan_external_dir(dir : string)} % Include fonts in directory \luafunction{dir} in font lookups without % adding them to the database. -% +% % \endfunctionlist -% +% % \endsubsubsection \endsubsection |