diff options
| -rw-r--r-- | luaotfload.dtx | 65 |
1 files changed, 60 insertions, 5 deletions
diff --git a/luaotfload.dtx b/luaotfload.dtx index b03154e..e6e9523 100644 --- a/luaotfload.dtx +++ b/luaotfload.dtx @@ -755,10 +755,64 @@ and the derived files % % \begin{quote} % \begin{verbatim} -% \font\test={Latin Modern Roman}:color=FF0000BB +% \font\test={Latin Modern Roman}:color=FF0000BB % \end{verbatim} % \end{quote} % +% \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: +% +% \begin{quote} +% \begin{verbatim} +% \font\iwonakernedA="file:Iwona-Regular.otf:kernfactor=0.125" +% \font\iwonakernedB="file:Iwona-Regular.otf:letterspace=12.5" +% \end{verbatim} +% \end{quote} +% +% 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 \verb|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 @@ -771,14 +825,15 @@ and the derived files % Alternatively and with loss of information, you can dump % those tables into your terminal by issuing % \begin{verbatim} -% \directlua{inspect(fonts.protrusions.setups.default) -% inspect(fonts.expansions.setups.default)} +% \directlua{inspect(fonts.protrusions.setups.default) +% inspect(fonts.expansions.setups.default)} % \end{verbatim} % at some point after loading \fileent{luaotfload.sty}. % } % For both, only the set \identifier{default} is predefined. % -% For example, to enable default protrusion\footnote{% +% For example, to define a font with the default +% protrusion vector applied\footnote{% % You also need to set % \verb|pdfprotrudechars=2| and % \verb|pdfadjustspacing=2| @@ -791,7 +846,7 @@ and the derived files % % \begin{quote} % \begin{verbatim} -% \font\test=LatinModernRoman:protrusion=default +% \font\test=LatinModernRoman:protrusion=default % \end{verbatim} % \end{quote} % \end{description} |