shape_text: Calculate glyph positions for strings

In textshaping: Bindings to the 'HarfBuzz' and 'Fribidi' Libraries for Text Shaping

Calculate glyph positions for strings

Description

Performs advanced text shaping of strings including font fallbacks, bidirectional script support, word wrapping and various character and paragraph level formatting settings.

Usage

shape_text(
  strings,
  id = NULL,
  family = "",
  italic = FALSE,
  weight = "normal",
  width = "undefined",
  features = font_feature(),
  size = 12,
  res = 72,
  lineheight = 1,
  align = "auto",
  hjust = 0,
  vjust = 0,
  max_width = NA,
  tracking = 0,
  indent = 0,
  hanging = 0,
  space_before = 0,
  space_after = 0,
  direction = "auto",
  path = NULL,
  index = 0,
  bold = deprecated()
)

Arguments

strings	A character vector of strings to shape
id	A vector grouping the strings together. If strings share an id the shaping will continue between strings
family	The name of the font families to match
italic	logical indicating the font slant
weight	The weight to query for, either in numbers (0, 100, 200, 300, 400, 500, 600, 700, 800, or 900) or strings ("undefined", "thin", "ultralight", "light", "normal", "medium", "semibold", "bold", "ultrabold", or "heavy"). NA will be interpreted as "undefined"/0
width	The width to query for either in numbers (0, 1, 2, 3, 4, 5, 6, 7, 8, or 9) or strings ("undefined", "ultracondensed", "extracondensed", "condensed", "semicondensed", "normal", "semiexpanded", "expanded", "extraexpanded", or "ultraexpanded"). NA will be interpreted as "undefined"/0
features	A systemfonts::font_feature() object or a list of them, giving the OpenType font features to set
size	The size in points to use for the font
res	The resolution to use when doing the shaping. Should optimally match the resolution used when rendering the glyphs.
lineheight	A multiplier for the lineheight
align	Within text box alignment, either 'auto', 'left', 'center', 'right', 'justified', 'justified-left', 'justified-right', 'justified-center', or 'distributed'. 'auto' and 'justified' will chose the left or right version depending on the direction of the text.
hjust, vjust	The justification of the textbox surrounding the text
max_width	The requested with of the string in inches. Setting this to something other than NA will turn on word wrapping.
tracking	Tracking of the glyphs (space adjustment) measured in 1/1000 em.
indent	The indent of the first line in a paragraph measured in inches.
hanging	The indent of the remaining lines in a paragraph measured in inches.
space_before, space_after	The spacing above and below a paragraph, measured in points
direction	The overall directional flow of the text. The default ("auto") will guess the direction based on the content of the string. Use "ltr" (left-to-right) and "rtl" (right-to-left) to turn detection of and set it manually.
path, index	path an index of a font file to circumvent lookup based on family and style
bold	logical indicating whether the font weight

Value

A list with two element: shape contains the position of each glyph, relative to the origin in the enclosing textbox. metrics contain metrics about the full strings.

shape is a data.frame with the following columns:

glyph

The placement of the the first character contributing to the glyph within the string

index

The index of the glyph in the font file

metric_id

The index of the string the glyph is part of (referencing a row in the metrics data.frame)

string_id

The index of the string the glyph came from (referencing an element in the strings input)

x_offset

The x offset in pixels from the origin of the textbox

y_offset

The y offset in pixels from the origin of the textbox

font_path

The path to the font file used during shaping of the glyph

font_index

The index of the font used to shape the glyph in the font file

font_size

The size of the font used during shaping

advance

The advancement amount to the next glyph

ascender

The ascend of the font used for the glyph. This does not measure the actual glyph

descender

The descend of the font used for the glyph. This does not measure the actual glyph

metrics is a data.frame with the following columns:

string

The text the string consist of

width

The width of the string

height

The height of the string

left_bearing

The distance from the left edge of the textbox and the leftmost glyph

right_bearing

The distance from the right edge of the textbox and the rightmost glyph

top_bearing

The distance from the top edge of the textbox and the topmost glyph

bottom_bearing

The distance from the bottom edge of the textbox and the bottommost glyph

left_border

The position of the leftmost edge of the textbox related to the origin

top_border

The position of the topmost edge of the textbox related to the origin

pen_x

The horizontal position of the next glyph after the string

pen_y

The vertical position of the next glyph after the string

ltr

The global direction of the string. If TRUE then it is left-to-right, otherwise it is right-to-left

Examples

string <- "This is a long string\nLook; It spans multiple lines\nand all"

# Shape with default settings
shape_text(string)

# Mix styles within the same string
string <- c(
  "This string will have\na ",
  "very large",
  " text style\nin the middle"
)

shape_text(string, id = c(1, 1, 1), size = c(12, 24, 12))

textshaping documentation built on April 4, 2025, 5:24 a.m.