Google Fonts
If a Google Font is requested
as part of a thematic theme, thematic
attempts to download, cache, and register that font for use with
showtext and ragg before plotting (see
font_spec() for more details). Therefore, to correctly
render these fonts, you’ll need at least showtext or
ragg installed; and in some scenarios, some additional
configuration may be required.
showtext allows custom fonts to be used with
essentially any R graphics device, whereas ragg itself
provides (high-quality and cross-platform) bitmap devices with 1st class
support for custom fonts. Therefore, consider using
showtext for vector-based images (i.e.,
svg(), cairo_pdf(), etc) and
ragg for raster-based images (i.e.,
ragg::agg_png(), ragg::agg_jpeg(), etc). Note
that shiny::renderPlot() currently requires a png image, so
ragg is generally preferable to
showtext in that case, especially on hosted
environments (e.g., Connect, shinyapps.io, etc. – because they don’t
have support for the high-quality quartz() device).
Shiny & R Markdown
If you have showtext installed, Google Fonts should
‘just work’ by default inside Shiny and R Markdown. However, before
deployment, include library(showtext) in the app/document
to make sure it’s installed on the hosted instance. Also, if you
encounter issues in R Markdown, make sure thematic is
being loaded in an initial “setup” chunk prior to any plotting chunks
(loading thematic ensures that the
fig.showtext knitr option defaults to
TRUE in future code chunks).
Using ragg instead of showtext in
these contexts requires some additional configuration: * Set
options(shiny.useragg = TRUE) in Shiny (requires
shiny v1.5.0 or higher). * Set
knitr::opts_chunk$set(dev = "ragg_png") in R Markdown
(requires knitr v1.29 or higher).
R graphics devices
In theory, as long as showtext is installed, Google
Fonts should render on any R graphics device. Here’s a mini example with
svglite::svglite():
thematic_on("black", "white", font = "Pacifico")
tmp <- tempfile(fileext = ".svg")
svglite::svglite(tmp, width = 7, height = 3)
plot(1, type = "n")
text(1, "Pacifico font")
dev.off()
if (rstudioapi::isAvailable()) file.show(tmp)
Note that thematic also includes a
thematic_save_plot() that is essentially a convenience
function for saving a plot to a graphics device, but also does the
following:
- Ensures the graphics device is informed by
thematic_get_option("bg"). - Ensures that showtext is aware of the device’s
resolution (
res), which is important to get the font sizes right in bitmap images (e.g., png, jpeg, etc). - Ensures that thematic is able to properly clone the device when determining if the device has support for the rendering a requested font.
# Makes a high-res png image
file <- thematic_save_plot(plot(1:10), res = 216)
if (rstudioapi::isAvailable()) file.show(tmp)Other Fonts
Other fonts that already known to R require no additional setup for
use with thematic. One way to make a font family
generally available to R is to import them via the extrafont
package. You can also register a font for use with
showtext via sysfonts::font_add() and with
ragg via systemfonts::register_font(). The
benefit of the sysfonts/systemfonts
approach is that registration is much much faster, and generally works
better, but registration must also be (re)-done in every new R
session.