R/webcam.R

In xaringanExtra: Extras and Extensions for 'xaringan' Slides

#' Webcam
#'
#' Add a live video of your webcam into your slides (in your own browser only).
#' Useful when you are presenting via video conference to include your video,
#' or when you are recording a class or lecture.
#'
#' @includeRmd man/fragments/webcam-details.Rmd details
#'
#' @examples
#' use_webcam()
#'
#' @references The webcam extension is based on the original
#'   [webcam implementation](https://yihui.org/en/2017/12/html5-camera/) by
#'   Yihui Xie, author of \pkg{xaringan}.
#' @name webcam
NULL

#' @describeIn webcam Add the webcam extension to your slides
#' @param width,height Width and height of the video pane in absolute CSS units,
#'   i.e. as `200` or `"200px"`.
#' @param margin Margin around the video pane in CSS units.
#'
#' @return An `htmltools::tagList()` with the HTML dependencies required for
#'   **webcam**.
#'
#' @export
use_webcam <- function(width = 200, height = 200, margin = "1em") {
  htmltools::tagList(
    html_dependency_webcam(width, height, margin)
  )
}

#' @describeIn webcam Returns an [htmltools::htmlDependency()] with the webcam
#'   dependencies. Most users will want to use `use_webcam()`.
#' @export
html_dependency_webcam <- function(width = 200, height = 200, margin = "1em") {
  width <- validateAbsoluteCssUnit(width)
  height <- validateAbsoluteCssUnit(height)
  margin <- htmltools::validateCssUnit(margin)
  opts <- sprintf('{"width":"%s","height":"%s","margin":"%s"}', width, height, margin)
  opts <- sprintf(
    '<script id="xaringanExtra-webcam-options" type="application/json">%s</script>',
    opts
  )
  htmltools::htmlDependency(
    name = "xaringanExtra-webcam",
    version = "0.0.1",
    package = "xaringanExtra",
    src = "webcam",
    script = "webcam.js",
    head = opts,
    all_files = FALSE
  )
}

validateAbsoluteCssUnit <- function(x) {
  var <- deparse(substitute(x))
  x <- htmltools::validateCssUnit(x)
  if (!grepl("px$", x)) {
    stop(
      var,
      " must be expressed in absolute integer ",
      "or pixel units.",
      call. = FALSE
    )
  }
  sub("px$", "", x)
}