sile-typesetter / sile / 11170735472

      Required = "rlig",

      Common = "liga",

      Contextual = "clig",

      Rare = "dlig",

      Discretionary = "dlig",

      Historic = "hlig",

   },

      On = "frac",

      Alternate = "afrc",

   },

   StylisticSet = function (i)

   end,

   CharacterVariant = function (i)

   end,

      Uppercase = "case",

      SmallCaps = "smcp",

      PetiteCaps = "pcap",

      UppercaseSmallCaps = "c2sc",

      UppercasePetiteCaps = "c2pc",

      Unicase = "unic",

   },

      Uppercase = "lnum",

      Lining = "lnum",

      LowerCase = "onum",

      OldStyle = "onum",

      Proportional = "pnum",

      monospaced = "tnum",

      SlashedZero = "zero",

      Arabic = "anum",

   },

      Swash = "cswh",

      Alternate = "calt",

      WordInitial = "init",

      WordFinal = "fina",

      LineFinal = "fault",

      Inner = "medi",

   },

      Superior = "sups",

      Inferior = "subs",

      Numerator = "numr",

      Denominator = "dnom",

      ScientificInferior = "sinf",

      Ordinal = "ordn",

   },

      Alternate = "salt",

      Italic = "ital",

      Ruby = "ruby",

      Swash = "swsh",

      Historic = "hist",

      TitlingCaps = "titl",

      HorizontalKana = "hkna",

      VerticalKana = "vkna",

   },

      MarkToBase = "mark",

      MarkToMark = "mkmk",

      AboveBase = "abvm",

      BelowBase = "blwm",

   },

      Uppercase = "cpsp",

      On = "kern",

   },

      Traditional = "trad",

      Simplified = "smpl",

      JIS1978 = "jp78",

      JIS1983 = "jp83",

      JIS1990 = "jp90",

      Expert = "expt",

      NLC = "nlck",

   },

      Proportional = "pwid",

      Full = "fwid",

      Half = "hwid",

      Third = "twid",

      Quarter = "qwid",

      AlternateProportional = "palt",

      AlternateHalf = "halt",

   },

}

local function tagpos (pos, k, v)

end

-- stylua: ignore start

-- Parser for feature strings

-- Parser for fontspec strings

-- Refer to fontspec.pdf (see doc), Chapter 3, Table 4 (p. 37)

-- stylua: ignore end

   end

   end

end

   end

end

   else

         end)

         else

         end

      end

   end

end

-- Input like {Ligatures = Historic} or {Ligatures = "{Historic, Discretionary}"}

--

-- Most real-world use should be single value, but multiple value use is not

-- that odd.  Junicode, for example, a common font among medievalists, has many

-- Stylistic Sets and Character Variations, many of which make sense to enable

-- simultaneously.

   end

end

end

   end)

   end)

      -- It is guaranteed that future releases of SILE will not implement non-OT \font

      -- features with capital letters.

      -- Cf. https://github.com/sile-typesetter/sile/issues/992#issuecomment-665575353

      -- So, we reserve 'em all. ⍩⃝

         end

      end

end

package.documentation = [[

\begin{document}

SILE automatically applies ligatures defined by the fonts that you use.

These ligatures are defined by tables of \em{features} within the font file.

As well as ligatures (multiple glyphs displayed as a single glyph), the features tables also declare other glyph substitutions.

The standard \autodoc:command{\font} command provides an interface to selecting the features that you want SILE to apply to a font.

The features available will be specific to the font file; some fonts come with documentation explaining their supported features.

Discussion of OpenType features is beyond the scope of this manual.

These features can be turned on and off by passing “raw” feature names to the \autodoc:command{\font} command like so:

\begin[type=autodoc:codeblock]{raw}

\font[features="+dlig,+hlig"]{...} % turn on discretionary and historic ligatures

\end{raw}

However, this is unwieldy and requires memorizing the feature codes.

The \autodoc:package{features} package provides two commands, \autodoc:command{\add-font-feature} and \autodoc:command{\remove-font-feature}, which make it easier to access OpenType features.

The interface is patterned on the TeX package \code{fontspec}; for full documentation of the OpenType features supported, see the documentation for that package.\footnote{\code{http://texdoc.net/texmf-dist/doc/latex/fontspec/fontspec.pdf}}

Here is how you would turn on discretionary and historic ligatures with the \autodoc:package{features} package:

\begin[type=autodoc:codeblock]{raw}

\add-font-feature[Ligatures=Rare]\add-font-feature[Ligatures=Discretionary]

...

\remove-font-feature[Ligatures=Rare]\remove-font-feature[Ligatures=Discretionary]

\end{raw}

\end{document}