Register a font that draws the shapes at a common size

The shape palettes made with unicode = TRUE draw each shape by asking the device font for a Unicode character. Fonts draw those characters at unrelated sizes, so a circle, a triangle and a plus sign from one font can differ by a factor of two in area, and a font may not have the character at all. register_shapes_font() registers a font that ships with ggthemes and contains the geometric shapes, arrows, signs and marks used by the palettes, at the same Unicode characters, so the same palettes draw with comparable sizes.

Usage

register_shapes_font()

Value

The font family name, "ggthemes shapes", to pass as a fontfamily. As side effects, the font is registered with systemfonts again, in case the registry was cleared, and the palettes stop warning about shapes the font has.

Size

Each glyph is scaled until the convex hull of its outline has the area of one reference circle. That keeps hollow, filled and rotated shapes comparable, and it is the convention R's own pch symbols follow (circle, square, diamond and triangle have equal area). Stroke widths are fixed. The exclamation mark is too narrow to reach the reference area without outgrowing the em box, so it is drawn smaller.

Coverage

The font covers every shape the unicode = TRUE palettes draw, so they need no other font: calc_shape_pal(), cleveland_shape_pal(), stata_shape_pal() and tableau_shape_pal(). It also covers the Tableau "kpi", "arrows" and "thin-arrows" palettes and the sign shapes of "gender" (see tableau_shape_pal()). It does not cover the pictograph shapes: the Tableau "weather" and "bug-tracking" palettes and the restroom signs of "gender". Those characters still come from the device font. Palettes with no unicode argument, such as tremmel_shape_pal(), use base pch symbols and need no font.

Using the font

The simplest way is geom_point_glyph() in place of ggplot2::geom_point(). It reads the font file itself, needs no font family set anywhere, and works with ggsave().

With geom_point(), the font must be set on the device font family, because geom_point() does not take a family. With a graphics device that reads fonts through systemfonts, such as ragg or svglite, set the family on a grid viewport around the plot:

family <- register_shapes_font()
p <- ggplot(mtcars, aes(mpg, hp, shape = factor(cyl))) +
  geom_point() +
  scale_shape_tableau(unicode = TRUE)
print(p, vp = grid::viewport(gp = grid::gpar(fontfamily = family)))

A palette made with unicode = TRUE warns, when the plot is built, if the device's default font lacks its shapes; it cannot see a family set on a viewport. Once register_shapes_font() or geom_point_glyph() has been called, it warns only about shapes this font does not have. That lasts until ggthemes is unloaded, for example by restarting R or with unloadNamespace("ggthemes"), since the setting lives in the package namespace.

ggthemes registers the font with systemfonts when it loads, if systemfonts is installed, so the family name "ggthemes shapes" works even before register_shapes_font() is called.

ggsave() draws the plot without that viewport, so the font does not apply through it; draw the plot to the device yourself, as above.

Devices that look fonts up themselves (pdf(), and png() with the cairo type) do not see fonts registered this way; install system.file("fonts", "ggthemes-shapes.ttf", package = "ggthemes") on the system to use the font there. A copy installed on the system is used as it is: register_shapes_font() does not register the family a second time.

The font is original work distributed under the same license as the package. It is built by data-raw/shapes-font/build.py.

See also

tableau_shape_pal() and cleveland_shape_pal() for palettes made with unicode = TRUE.

Other shapes: cleveland_shape_pal(), embed_shapes_font(), geom_point_glyph(), scale_shape_cleveland(), scale_shape_tremmel(), tremmel_shape_pal()

Examples

if (FALSE) { # rlang::is_installed(c("systemfonts", "ragg")) && interactive()
library("ggplot2")
family <- register_shapes_font()
p <- ggplot(mtcars, aes(mpg, hp, shape = factor(cyl))) +
  geom_point(size = 4) +
  scale_shape_tableau(unicode = TRUE)
png_file <- tempfile(fileext = ".png")
ragg::agg_png(png_file, width = 480, height = 360)
print(p, vp = grid::viewport(gp = grid::gpar(fontfamily = family)))
dev.off()
}