R/utils.R

In ellessenne/uolvid: Templates for Talks and Presentations

#' Wrap output to a given width
#'
#' @description `wrap_linewidth()` wrap the output from an R code chunk to a given width, specified by the global option `width`. Usage is pretty straighforward: set the global `width` option to a given value, set the knitr chunk option `linewidth` to `getOption("width")`, and call `wrap_linewidth()`. Further details [here](https://github.com/yihui/knitr-examples/blob/master/077-wrap-output.Rmd).
#'
#' @export
#'
#' @examples
#' \dontrun{
#' options(width = 60)
#' knitr::opts_chunk$set(echo = FALSE, fig.align = "center", linewidth = getOption("width"))
#' plates:::wrap_linewidth()
#' }
#'
wrap_linewidth <- function() {
  hook_output <- knitr::knit_hooks$get("output")
  knitr::knit_hooks$set(
    output = function(x, options) {
      # this hook is used only when the linewidth option is not NULL
      if (!is.null(n <- options$linewidth)) {
        x <- split_lines(x)
        # any lines wider than n should be wrapped
        if (any(nchar(x) > n)) {
          x <- strwrap(x, width = n)
        }
        x <- paste(x, collapse = "\n")
      }
      hook_output(x, options)
    }
  )
}

# Copied and adapted from rticles package:
find_file <- function(template, file) {
  template <- system.file("rmarkdown", "templates", template, file, package = "plates")
  if (template == "") {
    stop("Couldn't find template file ", template, "/", file, call. = FALSE)
  }

  template
}

find_resource <- function(template, file) {
  find_file(template, file.path("resources", file))
}

# Copied from knitr internal
split_lines <- function(x) {
  if (length(grep("\n", x)) == 0L) {
    return(x)
  }
  con <- textConnection(x)
  on.exit(close(con))
  readLines(con)
}