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.