Generate a shiny-app screenshot using snapper and download it using shinyFiles, shiny, or snapper

snapper-app.R

library(shiny)
# remotes::install_github("yonicd/snapper")
# remotes::install_github("thomas85p/shinyFiles")
library(snapper)
library(base64enc)
library(png)
library(shinyFiles)

js <- '
function get_img_src() {
  var img_src = $("#screenshot_link_preview img").attr("src");
  Shiny.setInputValue("img_src", img_src);
}
'

ui <- navbarPage("Snapper app",
  navbarMenu("", icon = icon("save"),
    tabPanel(
      snapper::preview_link(
        "screenshot_link", ui = "body", previewId = "screenshot_link_preview", label = "Take a screenshot",
        opts = config(
          ignoreElements = "function (el) {return el.className === 'dropdown-menu';}"
        )
      )
    )
  ),
  tags$head(
    tags$style(HTML("img { max-width: 85% !important; height: auto; }")),
    tags$script(HTML(js)),
    snapper::load_snapper()
  )
)

server <- function(input, output, session) {
  volumes <- c(Home = fs::path_home(), getVolumes()())
  shinyFileSave(input, "download_screenshot_sf", roots = volumes, session = session)
  shinyFileSave(input, "download_screenshot_sf_link", roots = volumes, session = session)

  observeEvent(input$screenshot_link, {
    showModal(
      modalDialog(
        title = "App screenshot",
        span(snapper::snapper_div(id = "screenshot_link_preview")),
        footer = tagList(
          shinySaveLink(
            "download_screenshot_sf_link", "", icon = icon("save"), "Save file as...",
            filename = "screenshot-sf-link.png", filetype = list(picture = "png"),
            onclick = "get_img_src();"
          ),
          shinySaveButton(
            "download_screenshot_sf", "Download (sf)", icon = icon("save"), "Save file as...",
            filename = "screenshot-sf-button.png", filetype = list(picture = "png"),
            onclick = "get_img_src();"
          ),
          downloadButton("download_screenshot", "Download (shiny)", onclick = "get_img_src();"),
          snapper::download_button(
            ui = "#screenshot_link_preview",
            label = "Download (snapper)",
            filename = "screenshot-snapper.png"
          ),
          modalButton("Cancel"),
        ),
        size = "m",
        easyClose = TRUE
      )
    )
  })

  observeEvent(input$download_screenshot_sf_link, {
    if (is.integer(input$download_screenshot_sf_link)) return()
    path <-  shinyFiles::parseSavePath(volumes, input$download_screenshot_sf_link)
    if (!inherits(path, "try-error") && length(path$datapath) > 0) {
      plt <- sub("data:.+base64,", "", input$img_src)
      plt <- png::readPNG(base64enc::base64decode(what = plt))
      png::writePNG(plt, path$datapath, dpi = 144)
    }
  })

  observeEvent(input$download_screenshot_sf, {
    if (is.integer(input$download_screenshot_sf)) return()
    path <-  shinyFiles::parseSavePath(volumes, input$download_screenshot_sf)
    if (!inherits(path, "try-error") && length(path$datapath) > 0) {
      plt <- sub("data:.+base64,", "", input$img_src)
      plt <- png::readPNG(base64enc::base64decode(what = plt))
      png::writePNG(plt, path$datapath, dpi = 144)
    }
  })

  output$download_screenshot <- downloadHandler(
    filename = function() {
      "radiant-screenshot.png"
    },
    content = function(file) {
      plt <- sub("data:.+base64,", "", isolate(input$img_src))
      plt <- png::readPNG(base64enc::base64decode(what = plt))
      png::writePNG(plt, file, dpi = 144)
    }
  )
}

shinyApp(ui, server)