R/social.R

In renderthis: Render Slides to Different Formats

# to_social() was inspired by this function from gadenbuie's blog:
# https://www.garrickadenbuie.com/blog/sharing-xaringan-slides/#the-perfect-share-image-ratio

#' Render png image of first slide sized for social media sharing.
#'
#' Render png image of first slide for sharing on social media.
#' Requires a local installation of Chrome as well as the {webshot2} package:
#' `remotes::install_github("rstudio/webshot2")`.
#'
#' @param from Path to Rmd file of input media (e.g., xaringan slides).
#' @param to The name of the output file. If using NULL then the output filename
#'   will be based on filename for the `from` file. If a filename is provided, a
#'   path to the output file can also be provided.
#'
#' @return Slides are rendered as a png file.
#'
#' @example man/examples/examples_social.R
#' @export
to_social <- function(from, to = NULL) {

    input <- from
    output_file <- to

    if (!requireNamespace("webshot2", quietly = TRUE)) {
        stop(
            "`webshot2` is required: ",
            'remotes::install_github("rstudio/webshot2")'
        )
    }

    # Check if Chrome is installed
    assert_chrome_installed()

    if (is.null(output_file)) {
        output_file <- path_from(input, "social")
    }

    # Check input and output files have correct extensions
    assert_path_ext(input, "rmd", arg = "from")
    assert_path_ext(output_file, "png", arg = "to")

    # Render a temporary html file for the slide snapshot
    # We used to use `webshot2::rmdshot()` but this way we have more control
    step_html <- path_from(input, "html", temporary = TRUE)
    cli::cli_alert_info("Rendering a temporary html for social image")
    to_html(
        from = input,
        to = step_html,
        self_contained = TRUE,
        render_args = list(
            output_options = list(nature = list(ratio = "191:100"))
        )
    )

    # Render png from rmd
    proc <- cli_build_start(step_html, output_file, on_exit = "done")
    tryCatch({
        webshot2::webshot(
            url = path_from(step_html, "url"),
            file = output_file,
            vheight = 600,
            vwidth = 600 * 191 / 100
        )},
        error = cli_build_failed(proc)
    )
}