R/events.R

In animejs: R Bindings to the 'Anime.js' Animation Library

.ANIME_EVENTS <- c(
  "onBegin",
  "onBeforeUpdate",
  "onUpdate",
  "onRender",
  "onLoop",
  "onPause",
  "onComplete"
)

#' Attach a JavaScript callback to an animation event
#'
#' The callback must be the name of a globally scoped JavaScript function
#' already present on the page, for example one injected via
#' `htmltools::tags$script()`. At render time the JavaScript binding resolves
#' the name to `window[callback]` and attaches it to the corresponding
#' Anime.js callback.
#'
#' @param x An `anime_timeline` or `anime_animation` object.
#' @param event One of
#'   `r paste0(paste0('"', .ANIME_EVENTS, '"'), collapse = ", ")`,
#'   matching the Anime.js v4 callback API.
#' @param callback Character scalar. Name of the global JS function to invoke.
#'
#' @return The modified object.
#'
#' @examples
#' if (interactive() && rlang::is_installed("htmltools")) {
#'   svg_src <- '<svg viewBox="0 0 200 100" xmlns="http://www.w3.org/2000/svg">
#'     <circle class="circle" cx="100" cy="50" r="20" fill="#4e79a7"/>
#'   </svg>'
#'
#'   widget <- anime_timeline(duration = 800) |>
#'     anime_add(selector = ".circle", props = list(opacity = c(0, 1))) |>
#'     anime_on("onComplete", "handleAnimationDone") |>
#'     anime_render(svg = svg_src)
#'
#'   callback_js <- htmltools::tags$script(
#'     "function handleAnimationDone() {
#'       console.log('Animation complete.');
#'     }"
#'   )
#'
#'   htmltools::browsable(htmltools::tagList(callback_js, widget))
#' }
#'
#' @export
anime_on <- function(x, event, callback) {
  check_anime_object(x)
  event <- rlang::arg_match(event, .ANIME_EVENTS)
  check_string(callback, "callback")
  x$events[[event]] <- callback
  x
}