Add write_extra_css and extra_css parameters

Also fixed an issue with `outfile` argument not getting passed back to write_xaringan_theme!

NAMESPACE

 export(mono_light)
 export(solarized_dark)
 export(solarized_light)
+export(write_extra_css)
 export(write_xaringan_theme)
 importFrom(grDevices,col2rgb)
 importFrom(grDevices,hsv)

R/duo.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template duo
 #' @family Duotone themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/duo_accent.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template duo_accent
 #' @family Duotone themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/duo_accent_inverse.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template duo_accent_inverse
 #' @family Duotone themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/mono_accent.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template mono_accent
 #' @family Monotone themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/mono_accent_inverse.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template mono_accent_inverse
 #' @family Monotone themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/mono_dark.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template mono_dark
 #' @family Monotone themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/mono_light.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template mono_light
 #' @family Monotone themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/solarized_dark.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template solarized_dark
 #' @family Solarized themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/solarized_light.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template solarized_light
 #' @family Solarized themes
 #' @export
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # DO NOT EDIT - Generated from inst/scripts/generate_theme_functions.R

R/utils.R

 call_write_xaringan_theme <- function() {
   paste0("write_xaringan_theme(",
          paste(template_variables$variable, collapse = ", "),
+         ", extra_css, outfile",
          ")")
 }
 

R/write_extra_css.R

+#' Write Extra CSS arguments
+#'
+#' Manually adds css elements to target `outfile`.
+#'
+#' @section css list:
+#' The `css` input must be a named list of css properties and values within a
+#' named list of class identifiers, for example
+#' `list(".class-id" = list("css-property" = "value"))`.
+#'
+#' @param css A named list of CSS definitions each containing a named list
+#'   of CSS property-value pairs, i.e.
+#'   `list(".class-id" = list("css-property" = "value"))`
+#' @inheritParams write_xaringan_theme
+#' @export
+write_extra_css <- function(css, outfile = "xaringan-themer.css") {
+  cat("\n\n/* Extra CSS */", list2css(css), file = outfile,
+      append = TRUE, sep = "\n")
+}
+
+#' @inheritParams write_extra_css
+#' @keywords internal
+list2css <- function(css) {
+  `%.%` <- function(x, y) paste0(x, y)
+  error <- NULL
+  if (is.null(names(css))) {
+    stop("All elements in `css` list must be named", call. = FALSE)
+  }
+  if (purrr::vec_depth(css) != 3) {
+    stop("`css` list must be a named list within a named list, e.g.:\n",
+         '  list(".class-id" = list("css-property" = "value"))')
+  }
+  if (any(names(css) == "")) {
+    not_named <- which(names(css) == "")
+    if (length(not_named) > 1) stop(call. = FALSE,
+      "All elements in `css` list must be named. Items ",
+      paste(not_named, collapse = ", "), " are unnamed."
+    ) else stop(call. = FALSE,
+      "All elements in `css` list must be named. Item ", not_named, " is not named.")
+  }
+  child_unnamed <- purrr::map_lgl(purrr::map(css, ~ {is.null(names(.)) || names(.) == ""}), ~ any(.))
+  if (any(child_unnamed)) {
+    has_unnamed <- names(css)[child_unnamed]
+    msg <- paste(
+      "All properties of elements in `css` list must be named.",
+      if (length(has_unnamed) > 1) "Elements" else "Element",
+      paste(has_unnamed, collapse = ", "),
+      if (length(has_unnamed) > 1) "have" else "has",
+      "unnamed property or properties."
+    )
+    stop(msg, call. = FALSE)
+  }
+
+  purrr::map_chr(names(css), function(el) {
+    paste(sep = "\n",
+      el %.% " {",
+      paste(
+        purrr::map_chr(names(css[[el]]), function(prop) {
+          "  " %.% prop %.% ': ' %.% css[[el]][[prop]] %.% ';'
+        }),
+        collapse = "\n"
+      ),
+      "}"
+    )
+  })
+}

R/write_theme.R

 #' @param code_font_family Code Font Family, defaults to 'Source Code Pro'
 #' @param code_font_url Code Font URL, defaults to https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700
 #' @param code_font_family_fallback Code Font Fallback, defaults to 'Lucida Console', Monaco
-#' @param outfile Customized xaringan CSS output file name
+#' @template extra_css
+#' @param outfile Customized xaringan CSS output file name, default is "xaringan-themer.css"
 #' @template write_xaringan_theme
 #' @export
 write_xaringan_theme <- function(
   code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
   code_font_family_fallback = "'Lucida Console', Monaco",
+  extra_css = NULL,
   outfile = "xaringan-themer.css"
 ) {
   # Make sure font names are wrapped in quotes if they have spaces
   template <- paste(template, collapse = "\n")
   x <- glue::glue(template, .open = "{{", .close = "}}")
   cat(x, file = outfile)
+  if (!is.null(extra_css)) write_extra_css(extra_css, outfile)
   outfile
 }

README.Rmd

   fig.path = "man/figures/README-",
   out.width = "100%"
 )
+library(xaringanthemer)
 ```
 # xaringanthemer
 
 [xaringan]: https://github.com/yihui/xaringan
+[remarkjs]: https://github.com/gnab/remark
 
 Easily style your [xaringan] slides with **xaringanthemer**.
 
       countIncrementalSlides: false
 ```
 
-### Fully Customized
+## Theme Settings
 
 The theme functions listed above are just wrappers around the central function of this package, `write_xaringan_theme()`.
 If you want to start from the default **xaringan** theme and make a few modifications, start there.
 cat(paste0("- `", tvv[grepl("^title_slide_", tvv)], "`"), sep = "\n")
 ```
 
+## Adding Custom CSS
+
+You can also add custom CSS classes using the `extra_css` argument in the theme functions.
+This argument takes a named list of CSS definitions each containing a named list of CSS property-value pairs.
+
+```r
+extra_css <- list(
+  ".red"   = list(color = "red"),
+  ".small" = list("font-size" = "90%"),
+  ".full-width" = list(
+    display = "flex",
+    width   = "100%",
+    flex    = "1 1 auto"
+  )
+)
+```
+
+If you would rather keep your additional css definitions in a separate file, you can call `write_extra_css()` separately.
+Just be sure to include your new CSS file in the list of applied files in your YAML header.
+
+```r
+write_extra_css(css = extra_css, outfile = "custom.css")
+```
+
+```{r results='asis', echo=FALSE}
+extra_css <- list(
+  ".red"   = list(color = "red"),
+  ".small" = list("font-size" = "90%"),
+  ".full-width" = list(
+    display = "flex",
+    width   = "100%",
+    flex    = "1 1 auto"
+  )
+)
+cat(
+  "\n```css",
+  "/* Extra CSS */",
+  xaringanthemer:::list2css(extra_css),
+  "```",
+  sep = "\n"
+)
+```
+
+This is most helpful when wanting to define helper classes to work with the [remark.js][remarkjs] `.class[]` syntax.
+Using the above example, we could color text red `.red[like this]` or write `.small[in smaller font size]`.
+
 ## Fonts
 
 [google-fonts]: https://fonts.google.com

README.md

       - [Monotone](#monotone)
       - [Duotone](#duotone)
       - [Solarized](#solarized)
-      - [Fully Customized](#fully-customized)
+  - [Theme Settings](#theme-settings)
+  - [Adding Custom CSS](#adding-custom-css)
   - [Fonts](#fonts)
 
 ## Installation
       countIncrementalSlides: false
 ```
 
-### Fully Customized
+## Theme Settings
 
 The theme functions listed above are just wrappers around the central
 function of this package, `write_xaringan_theme()`. If you want to start
   - `title_slide_background_color`
   - `title_slide_background_image`
 
+## Adding Custom CSS
+
+You can also add custom CSS classes using the `extra_css` argument in
+the theme functions. This argument takes a named list of CSS definitions
+each containing a named list of CSS property-value pairs.
+
+``` r
+extra_css <- list(
+  ".red"   = list(color = "red"),
+  ".small" = list("font-size" = "90%"),
+  ".full-width" = list(
+    display = "flex",
+    width   = "100%",
+    flex    = "1 1 auto"
+  )
+)
+```
+
+If you would rather keep your additional css definitions in a separate
+file, you can call `write_extra_css()` separately. Just be sure to
+include your new CSS file in the list of applied files in your YAML
+header.
+
+``` r
+write_extra_css(css = extra_css, outfile = "custom.css")
+```
+
+``` css
+/* Extra CSS */
+.red {
+  color: red;
+}
+.small {
+  font-size: 90%;
+}
+.full-width {
+  display: flex;
+  width: 100%;
+  flex: 1 1 auto;
+}
+```
+
+This is most helpful when wanting to define helper classes to work with
+the [remark.js](https://github.com/gnab/remark) `.class[]` syntax. Using
+the above example, we could color text red `.red[like this]` or write
+`.small[in smaller font size]`.
+
 ## Fonts
 
 Yihui picked out great fonts for the default **xaringan** theme, but

inst/scripts/generate_theme_functions.R

     as.character(
       glue::glue_data(
         tv, "#' @param {variable} {description}, defaults to {stringr::str_replace_all(default, '[{{}}]', '`')}")) %,%
-    "#' @param outfile Customized xaringan CSS output file name" %,%
+    "#' @template extra_css" %,%
+    "#' @param outfile Customized xaringan CSS output file name, default is \"xaringan-themer.css\"" %,%
     c(...) %,%
     glue::glue("{f_name} <- function(") %,%
     as.character(glue::glue_data(
       tv, "  {variable} = {ifelse(!stringr::str_detect(default, '^[{].+[}]$'), paste0('\"', default, '\"'), stringr::str_replace_all(default, '[{}]', ''))},")) %,%
+    "  extra_css = NULL," %,%
     "  outfile = \"xaringan-themer.css\"" %,%
     ") {"
   if (!is.null(body)) x <- c(x, body, "}")

inst/scripts/write_xaringan_theme_body.R

 template <- paste(template, collapse = "\n")
 x <- glue::glue(template, .open = "{{", .close = "}}")
 cat(x, file = outfile)
+if (!is.null(extra_css)) write_extra_css(extra_css, outfile)
 outfile

man-roxygen/extra_css.R

+#' @param extra_css A named list of CSS definitions each containing a named list
+#'   of CSS property-value pairs, i.e.
+#'   `list(".class-id" = list("css-property" = "value"))`

man/duo.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 A duotone theme designed to work well with two complementary

man/duo_accent.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 An default xaringan theme with a two colors used for color

man/duo_accent_inverse.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 An "inverted" default xaringan theme with a two colors used

man/mono_accent.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 The default xaringan theme with a single color used for color

man/mono_accent_inverse.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 An "inverted" default xaringan theme with a single color used

man/mono_dark.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 A dark monotone theme based around a single color.

man/mono_light.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 A light monotone theme based around a single color.

man/solarized_dark.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 A dark theme based around on the solarized color scheme.

man/solarized_light.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 A light theme based around on the solarized color scheme.

man/write_extra_css.Rd

+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/write_extra_css.R
+\name{write_extra_css}
+\alias{write_extra_css}
+\title{Write Extra CSS arguments}
+\usage{
+write_extra_css(css, outfile = "xaringan-themer.css")
+}
+\arguments{
+\item{css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+\code{list(".class-id" = list("css-property" = "value"))}}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
+}
+\description{
+Manually adds css elements to target \code{outfile}.
+}
+\section{css list}{
+
+The \code{css} input must be a named list of css properties and values within a
+named list of class identifiers, for example
+\code{list(".class-id" = list("css-property" = "value"))}.
+}
+

man/write_xaringan_theme.Rd

   header_font_url = "https://fonts.googleapis.com/css?family=Yanone+Kaffeesatz",
   code_font_google = NULL, code_font_family = "'Source Code Pro'",
   code_font_url = "https://fonts.googleapis.com/css?family=Source+Code+Pro:400,700",
-  code_font_family_fallback = "'Lucida Console', Monaco",
+  code_font_family_fallback = "'Lucida Console', Monaco", extra_css = NULL,
   outfile = "xaringan-themer.css")
 }
 \arguments{
 
 \item{code_font_family_fallback}{Code Font Fallback, defaults to 'Lucida Console', Monaco}
 
-\item{outfile}{Customized xaringan CSS output file name}
+\item{extra_css}{A named list of CSS definitions each containing a named list
+of CSS property-value pairs, i.e.
+`list(".class-id" = list("css-property" = "value"))`}
+
+\item{outfile}{Customized xaringan CSS output file name, default is "xaringan-themer.css"}
 }
 \description{
 Creates a customized Xaringan theme CSS file.

tests/testthat/test-list2css.R

+context("test-list2css.R")
+
+test_that("list2css converts lists to css", {
+  css <- list(
+    '.remark-slide' = list(
+      "color" = "#FFF",
+      "font-size" = "30px"
+    )
+  )
+  expected <- '.remark-slide {\n  color: #FFF;\n  font-size: 30px;\n}'
+  expect_equal(list2css(css), expected)
+
+  css[[".new-class"]] <- list("background-color" = "#000")
+  expected <- c(expected, ".new-class {\n  background-color: #000;\n}")
+  expect_equal(list2css(css), expected)
+})
+
+test_that("list2css errors if css list is not named", {
+  css <- list(list(
+    "color" = "#FFF",
+    "font-size" = "30px"
+  ))
+  expect_error(list2css(css))
+})
+
+test_that("list2css errors if css list has unnamed elements", {
+  css <- list(
+    list(
+      "color" = "#FFF",
+      "font-size" = "30px"
+    ),
+    '.test' = list(color = 'red')
+  )
+  expect_error(list2css(css))
+})
+
+test_that("list2css errors if css list has unnamed properties", {
+  css <- list(
+    ".class" = list(
+      color = "#FFF",
+      "font-size" = "30px"
+    ),
+    '.test' = list('red')
+  )
+  expect_error(list2css(css))
+
+  css <- list(
+    ".class" = list(
+      "#FFF",
+      "font-size" = "30px"
+    ),
+    '.test' = list('red')
+  )
+  expect_error(list2css(css))
+})
+
+test_that("list2css errors if not list within list", {
+  css <- list(
+    ".class" = list(
+      list(color = "red"),
+      "font-size" = "30px"
+    ),
+    '.test' = list('red')
+  )
+  expect_error(list2css(css))
+})