added assert_chrome_installed() for issue #12; updated documentation

R/all.R

@@ -1,7 +1,7 @@
 #' Build xaringan slides to multiple outputs.
 #'
 #' Build xaringan slides to multiple outputs. Options are `"html"`, `"pdf"`,
-#' `"gif"`, `"pptx"`, and `"thumbnail"` (a png image of the first slide).
+#' `"gif"`, `"pptx"`, `"thumbnail"`, and `"social"`.
 #' @param input Path to Rmd file of xaringan slides.
 #' @param include A vector of the different output types to build. Options are
 #' `"html"`, `"pdf"`, `"gif"`, `"pptx"`, and `"thumbnail"` (a png image of the

R/gif.R

@@ -1,4 +1,7 @@
 #' Build xaringan slides as gif file.
+#'
+#' Build xaringan slides as a gif file from a Rmd, html, or pdf file. The
+#' function builds to the pdf and then converts it to a gif.
 #' @param input Path to Rmd, html, or pdf file of xaringan slides.
 #' @param output_file Name of the output gif file.
 #' @param density Resolution of the resulting gif file.

R/html.R

@@ -1,4 +1,7 @@
 #' Build xaringan slides as html file.
+#'
+#' Build xaringan slides as html file. Essentially the same thing as
+#' `rmarkdown::render()` with `output_format = "xaringan::moon_reader"`
 #' @param input Path to Rmd file of xaringan slides.
 #' @param output_file The name of the output file. If using NULL then
 #' the output filename will be based on filename for the input file.

R/pdf.R

@@ -1,4 +1,9 @@
-#' Prints xaringan slides to a PDF file.
+#' Build xaringan slides as pdf file.
+#'
+#' Build xaringan slides to a pdf file. Requires a local installation of
+#' Chrome. If you set `complex_slides = TRUE` or `partial_slides = TRUE`,
+#' you will also need to install the {chromote} package:
+#' `devtools::install_github("rstudio/chromote")`
 #' @param input Path to Rmd or html file of xaringan slides.
 #' @param output_file The name of the output file. If `NULL` (the default) then
 #' the output filename will be based on filename for the input file.
@@ -48,6 +53,9 @@ build_pdf <- function(
   partial_slides = FALSE,
   delay = 1
 ) {
+    # Check if Chrome is installed
+    assert_chrome_installed()
+
     # Check input and output files have correct extensions
     assert_path_ext(input, c("rmd", "html"), arg = "input")
     output_file <- check_output_file(input, output_file, "pdf")

R/pptx.R

@@ -1,4 +1,8 @@
 #' Build xaringan slides as pptx file.
+#'
+#' Build xaringan slides as pptx file from a Rmd, html, or pdf file. The
+#' function builds to the pdf and then inserts a png image of each slide
+#' as a new slide in a pptx file.
 #' @param input Path to Rmd, html, or pdf file of xaringan slides.
 #' @param output_file Name of the output pptx file.
 #' @param density Resolution of the resulting pptx file.

R/social.R

@@ -1,8 +1,11 @@
 # build_social() was inspired by this function from gadenbuie's blog:
 # https://www.garrickadenbuie.com/blog/sharing-xaringan-slides/#the-perfect-share-image-ratio
 
+#' Build png image of first slide sized for social media sharing.
+#'
 #' Build png image of first xaringan slide for sharing on social media.
-#' Requires a local installation of Chrome.
+#' Requires a local installation of Chrome as well as the {webshot2} package:
+#' `remotes::install_github("rstudio/webshot2")`.
 #' @param input Path to Rmd file of xaringan slides.
 #' @param output_file The name of the output file. If using NULL then
 #' the output filename will be based on filename for the input file.
@@ -23,6 +26,9 @@ build_social <- function(input, output_file = NULL) {
         )
     }
 
+    # Check if Chrome is installed
+    assert_chrome_installed()
+
     # Check input and output files have correct extensions
     assert_path_ext(input, "rmd", arg = "input")
     output_null <- is.null(output_file)

R/thumbnail.R

@@ -1,4 +1,7 @@
-#' Build png thumbnail image of first xaringan slide.
+#' Build png thumbnail image of first slide.
+#'
+#' Build png thumbnail image of first xaringan slide. Requires a local
+#' installation of Chrome.
 #' @param input Path to Rmd or html file of xaringan slides.
 #' @param output_file Name of the output png file.
 #' @export
@@ -10,6 +13,9 @@
 #' }
 build_thumbnail <- function(input, output_file = NULL) {
 
+    # Check if Chrome is installed
+    assert_chrome_installed()
+
     # Check input and output files have correct extensions
     assert_path_ext(input, c("rmd", "html"), arg = "input")
     output_null <- is.null(output_file)

R/utils.R

@@ -42,3 +42,19 @@ append_to_file_path <- function(path, s) {
         )
     )
 }
+
+assert_chrome_installed <- function() {
+    chromePath <- NULL
+    error <- paste0(
+        "This function requires a local installation of the Chrome ",
+        "browser. You can also use other browsers based on Chromium, ",
+        "such as Chromium itself, Edge, Vivaldi, Brave, or Opera.")
+    tryCatch({
+      chromePath <- chromote::find_chrome()
+      },
+      error = function(e) { message(error) }
+    )
+    if (is.null(chromePath)) {
+        stop(error)
+    }
+}