This function encapsulates the specification of OpenType font features. Some specific features have named arguments, but all available features can be set by using its specific 4-letter tag For a list of the 4-letter tags available see e.g. the overview on Wikipedia.
font_feature(ligatures = NULL, letters = NULL, numbers = NULL, ...)A font_feature object
Settings related to ligatures. One or more types of ligatures to turn on (see details).
Settings related to the appearance of single letters (as opposed to ligatures that substitutes multiple letters). See details for supported values.
Settings related to the appearance of numbers. See details for supported values.
key-value pairs with the key being the 4-letter tag and the value
being the setting (usually TRUE to turn it on).
OpenType features are defined by a 4-letter tag along with an integer value.
Often that value is a simple 0 (off) or 1 (on), but some features support
additional values, e.g. stylistic alternates (salt) where a font may
provide multiple variants of a letter and the value will be used to chose
which one to use.
Common features related to appearance may be given with a long form name to
either the ligatures, letters, or numbers argument to avoid remembering
the often arbitrary 4-letter tag. Providing a long form name is the same as
setting the tag to 1 and can thus not be used to set tags to other values.
The possible long form names are given below with the tag in parenthesis:
Ligatures
standard (liga): Turns on standard multiple letter substitution
historical (hlig): Use obsolete historical ligatures
contextual (clig): Apply secondary ligatures based on the character
patterns surrounding the potential ligature
discretionary (dlig): Use ornamental ligatures
Letters
swash (cswh): Use contextual swashes (ornamental decorations)
alternates (calt): Use alternate letter forms based on the sourrounding
pattern
historical (hist): Use obsolete historical forms of the letters
localized (locl): Use alternate forms preferred by the script language
randomize (rand): Use random variants of the letters (e.g. to mimick
handwriting)
alt_annotation (nalt): Use alternate annotations (e.g. circled digits)
stylistic (salt): Use a stylistic alternative form of the letter
subscript (subs): Set letter in subscript
superscript (sups): Set letter in superscript
titling (titl): Use letter forms well suited for large text and titles
small_caps (smcp): Use small caps variants of the letters
Numbers
lining (lnum): Use number variants that rest on the baseline
oldstyle (onum): Use old style numbers that use descender and ascender
for various numbers
proportional (pnum): Let numbers take up width based on the visual
width of the glyph
tabular (tnum): Enforce all numbers to take up the same width
fractions (frac): Convert numbers separated by / into a fraction
glyph
fractions_alt (afrc): Use alternate fraction form with a horizontal
divider
font_feature(letters = "stylistic", numbers = c("lining", "tabular"))
# Use the tag directly to access additional stylistic variants
font_feature(numbers = c("lining", "tabular"), salt = 2)
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