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reprex venue RTF

Source: vignettes/articles/rtf.Rmd
rtf.Rmd

Use reprex_rtf() to get output in Rich Text Format. It is a convenience wrapper around reprex(venue = "rtf"). This is useful for creating syntax highlighted code snippets – rendered or not – to paste into software such as Keynote, PowerPoint, or Word.

Why is RTF special? Although Pandoc can produce RTF and, therefore, so can rmarkdown::render() and reprex::reprex(), Pandoc’s syntax highlighting is unavailable for RTF output. For now, we’ve got to get the functionality from somewhere else. Syntax highlighting is a non-issue for venue = "gh" (GitHub) and venue = "so" (Stack Overflow), because the target sites take care of that when the Markdown content is displayed.

Gif of setting options to control highlight and using reprex with the RTF venue

The “rtf” venue was introduced in reprex v0.2.1 and is experimental. The highlight command line tool must (1) be installed and (2) be on your PATH. People have successfully used reprex_rtf() on macOS and Windows (specifically, Windows 10 + Windows PowerShell 5.1). We consider it experimental because of the rather hacky way we shell out to highlight and, long-term, it would be preferable to get syntax-highlighted RTF through a proper R package. The existing highlight R package can’t do this (yet?).

How to install highlight

The highlight website offers downloads in various forms, for various OSes:

For macOS users who use homebrew, this works:

brew install highlight

For Windows users who use chocolatey, this works:

choco install highlight

On Windows, the chocolatey method did not add highlight to my PATH and this could affect other methods of installation as well. In this case, you’ll need to do this manually. In my case, I needed to add C:\Program Files\Highlight to PATH. A second issue we’ve seen is with the scoop package manager for Windows, which uses a shim-based method of making the executables it installs findable. The shim method appears to be less resilient to the different ways of calling highlight from R.

reprex_rtf() should work when Sys.which("highlight"), executed in R, correctly returns the path to your highlight executable.

Here’s how that looks for me on macOS:

Sys.which("highlight")
#>                  highlight 
#> "/usr/local/bin/highlight"

and on Windows:

Sys.which("highlight")
#>                              highlight 
#> "C:\\PROGRA~1\\HIGHLI~1\\HIGHLI~2.EXE"

Here is the highlight call implied by the default behaviour of reprex_rtf():

highlight -i foo_reprex.R --out-format rtf --no-trailing-nl --encoding=UTF-8 --style darkbone --font 'Courier Regular' --font-size 50 -o foo_reprex.rtf

Basic usage

Let’s reprex some code and stick it on a Keynote slide with other non-R “features”.

reprex({
  (x <- rnorm(3))
  mean(x)
}, venue = "rtf")

highlight options

If you don’t like the defaults, control highlight command line arguments by setting reprex.highlight.* options. Why options? I didn’t want to burden reprex() with even more arguments and this is usually something you want to set globally for yourself or for an entire project or talk or course.

Set these options with code like this:

options(
  reprex.highlight.hl_style  = "darkbone",
  reprex.highlight.font      = "Source Code Pro",
  reprex.highlight.font_size = 50
)

The supported options are reprex.highlight.hl_style, reprex.highlight.font, reprex.highlight.font_size (all shown above), and reprex.highlight.other (a catchall for anything else, shown below).

You could set options for all your reprexing by doing this in your user-level .Rprofile. Create or open this file via usethis::edit_r_profile().

You could also set options for a specific Project in .Rprofile inside the Project. Create or open this file via usethis::edit_r_profile("project").

Finally, you might collect all of the R snippets destined for inclusion in, e.g. some talk slides, in a .R file. It would make sense to set the reprex.highlight.* options at the start of that file.

hl_style must be one of your existing highlight themes and font must be one of your installed fonts.

List available themes:

highlight --list-scripts=themes

But what do these themes look like? Here are some galleries that probably have high overlap with your themes:

http://www.andre-simon.de/doku/highlight/en/theme-samples.php
https://rclickhandbuch.files.wordpress.com/2014/09/knitrthemesoverview.pdf

You can also override defaults on-the-fly. Here’s how to do that for a single call using withr and, as a bonus, how to use reprex.highlight.other to send arbitrary command line arguments to highlight:

withr::with_options(
  new = c(
    reprex.highlight.hl_style  = "dusk",
    reprex.highlight.font      = "Fira Code Regular",
    reprex.highlight.font_size = 35,
    reprex.highlight.other     = "--line-numbers --line-number-length=2 --zeroes"
  ),
  reprex::reprex(input = c("(x <- rnorm(3))", "mean(x)"), venue = "rtf")
)

Here’s how to set highlight options for part of an R session:

op <- options(
  reprex.highlight.hl_style  = "anotherdark",
  reprex.highlight.font      = "Andale Mono Regular",
  reprex.highlight.font_size = 60,
  reprex.highlight.other     = "--line-numbers"
)

reprex::reprex(input = c("(x <- rnorm(3))", "mean(x)"), venue = "rtf")

options(op)

Experience has shown that it is hard to predict which aspects of the RTF will be honored when you paste into the target document. We’re talking about things like the font size or background color. This seems to vary greatly across applications and operating systems and you’ll just have to experiment to find a workflow that is practical for you.

Note that it is even possible to create a custom highlight theme, e.g. to match the theme of a Keynote or Powerpoint slide deck with respect to background color, font, etc. A specific example of this is documented in these how-to notes.

Run … or not

If you just want to highlight code, but not run it, set chunk option eval = FALSE option, i.e. put a special comment as the first line of your reprex source:

#+ eval = FALSE
(x <- rnorm(3))
mean(x)

The above source, when reprex()ed, will not include the usual output. This is not specific to venue = "rtf", but it’s more likely to come up in this setting.

What if each snippet can’t be self-contained?

reprex:::prex() and friends

When preparing bits of code for a presentation, it can be impractical to make each snippet completely self-contained. You really need to run the snippets in the current workspace and session. But reprex() does not allow this.

The unexported function prex() addresses this use case. It’s like reprex(), but much less reproducible!

  • Code is evaluated in the global environment of the current R session.
  • Current working directory is used.
  • advertise = FALSE is the default.

prex() also has “venue as suffix” variants, so reprex:::prex_rtf(...) is short for reprex:::prex(..., venue = "rtf").

This code defines x and y in the current workspace and writes the file stuff.txt to the current working directory.

x <- 1
y <- 4
writeLines("blah blah", file.path(getwd(), "stuff.txt"))

Now we can show the difference between prex() and reprex().

prex({
  ls()
  x + y
  readLines("stuff.txt")  
})

yields

ls()
#> [1] "x" "y"
x + y
#> [1] 5
readLines("stuff.txt")
#> [1] "blah blah"

x and y can be found, even though they aren’t defined in the snippet, and stuff.txt can be read.

This is very different from executing the same code via reprex():

reprex({
  ls()
  x + y
  readLines("stuff.txt")  
})

which yields:

ls()
#> character(0)
x + y
#> Error in eval(expr, envir, enclos): object 'x' not found
readLines("stuff.txt")
#> Warning in file(con, "r"): cannot open file 'stuff.txt': No such file or
#> directory
#> Error in file(con, "r"): cannot open the connection

x and y can’t be found, because reprex() works in a clean session, and stuff.txt can’t be found, because reprex() works in a temp directory, by default.

If you’re going to prex() a lot, you’ll want to do something like this in your .R file of snippets or in the project-specific or user-level .Rprofile:

prex <- reprex:::prex
prex_rtf <- reprex:::prex_rtf

Selectively hide and reveal code

Before prex() existed, you had to use a more cumbersome technique to produce small snippets, by hiding code. We leave this here in case it is still useful in some situations.

You can use knitr chunk options to selectively hide code, i.e. to run a large snippet, but only include a small bit in the output.

This is easiest to show by example. If you reprex() this code, only the last three lines and their output will appear in the output. But the other lines will be run, i.e. str_reverse() will be defined, as will the bizzaro() generic and default method.

#+ include = FALSE
str_reverse <- function(x) {
  vapply(
    strsplit(x, ""),
    FUN = function(z) paste(rev(z), collapse = ""),
    FUN.VALUE = "")
}

#+ include = FALSE
bizarro <- function(x) {
  UseMethod("bizarro")
}
bizarro.default <- function(x) {
  stop(
    "Don't know how to make bizzaro <",
    class(x)[[1]], ">",
    call. = FALSE
  )
}

#+ include = TRUE
bizarro.character <- function(x) str_reverse(x)

bizarro(c("abc", "def"))

bizarro(1:5)