my attempt to create a widgetframe with a dark background. hackish. seems to shift xaringan presentation oddly.

dark_widgetframe.R

# remove any old tmp files
old_tmp_files <- list.files(pattern = '^tmp', include.dirs = TRUE, full.names = TRUE)
invisible(unlink(old_tmp_files, recursive = TRUE))

# create a dark widget frame via work around
dark_widgetframe <- 
function(widget, background = '#666666FF', width = '100%', height = 420) {
  file = tempfile(pattern = "tmp", tmpdir = '.', fileext = ".html")
  selfcontained = FALSE
  libdir = NULL
  knitrOptions = list()
  
  # code directly from widgetframe::frameWidget()
  parentWidget <- NULL
  if ("widgetframe" %in% class(widget)) {
      parentWidget <- widget
  } else {
    # added width, height
      parentWidget <- 
        widgetframe::frameWidget(widget, width = width, height = height)
  }
  childDir <- file.path(
    dirname(file), 
    paste0(tools::file_path_sans_ext(basename(file)), "_widget"))
  dir.create(childDir)
  parentWidget$x$url <- 
    paste0(tools::file_path_sans_ext(basename(file)), "_widget/index.html")
  childWidget <- attr(parentWidget$x, "widget")
  oldwd <- setwd(childDir)
  htmlwidgets::saveWidget(
    childWidget, "index.html", 
    selfcontained = selfcontained, 
    libdir = libdir, background = background, knitrOptions = knitrOptions)
  setwd(oldwd)
  htmlwidgets::saveWidget(
    parentWidget, file, selfcontained = selfcontained, 
    libdir = libdir, background = background, knitrOptions = knitrOptions)
  lines <- readLines(file, warn = FALSE, encoding = "UTF-8")[-1]
  html_raw <- htmltools:::paste8(lines, collapse = "\r\n")
  return(htmltools::HTML(html_raw))
}