Set fig.showtext chunk option on package load and error loudly if fig.showtext = FALSE for a chunk with theme_xaringan()

R/ggplot2.R

@@ -742,7 +742,9 @@ register_font <- function(
           "Font '{family}' must be manually registered using `sysfonts::font_add()`."
         )
       }
-      warning(msg, call. = FALSE)
+      warning(str_wrap(msg), call. = FALSE)
+    } else {
+      verify_fig_showtext(fn)
     }
   }
   xaringanthemer_env[["registered_font_families"]] <- c(
@@ -752,6 +754,19 @@ register_font <- function(
   family
 }
 
+verify_fig_showtext <- function(fn = "theme_xaringan_base") {
+  if (is.null(knitr::current_input())) return()
+  # Try to set fig.showtext automatically
+  if (isTRUE(knitr::opts_current$get("fig.showtext"))) {
+    return()
+  }
+  stop(str_wrap(
+    "To use ", fn, "() with knitr, you need to set the chunk option ",
+    "`fig.showtext = TRUE` for this chunk. Or you can set this option ",
+    "globally with `knitr::opts_chunk$set(fig.showtext = TRUE)`."
+  ))
+}
+
 requires_xaringanthemer_env <- function(
   css_file = NULL,
   try_css = TRUE,

R/utils.R

@@ -115,3 +115,7 @@ quote_elements_w_spaces <- function(x) {
   x[has_space & not_quoted] <- paste0("'", x[has_space & not_quoted], "'")
   paste(x, collapse = ", ")
 }
+
+str_wrap <- function(...) {
+  paste(strwrap(paste0(...)), collapse = "\n")
+}

R/zzz.R

@@ -0,0 +1,17 @@
+# nocov start
+.onLoad <- function(libname, pkgname, ...) {
+
+  if ("knitr" %in% loadedNamespaces()) {
+    knitr::opts_chunk$set(fig.showtext = TRUE)
+  }
+
+  setHook(
+    packageEvent("knitr", "onLoad"),
+    function(...) {
+      knitr::opts_chunk$set(fig.showtext = TRUE)
+    }
+  )
+
+  invisible()
+}
+# nocov end